Mark Denny

All Publications

• The extraordinary joint material of an articulated coralline alga. II. Modeling the structural basis of its mechanical properties JOURNAL OF EXPERIMENTAL BIOLOGY Denny, M. W., King, F. A. 2016; 219 (12): 1843-1850

  Abstract

  By incorporating joints into their otherwise rigid fronds, erect coralline algae have evolved to be as flexible as other seaweeds, which allows them to thrive - and even dominate space - on wave-washed shores around the globe. However, to provide the required flexibility, the joint tissue of Calliarthron cheilosporioides, a representative articulated coralline alga, relies on an extraordinary tissue that is stronger, more extensible and more fatigue resistant than that of other algae. Here, we used the results from recent experiments to parameterize a conceptual model that links the microscale architecture of cell walls to the adaptive mechanical properties of joint tissue. Our analysis suggests that the theory of discontinuous fiber-wound composite materials (with cellulose fibrils as the fibers and galactan gel as the matrix) can explain key aspects of the material's mechanics. In particular, its adaptive viscoelastic behavior can be characterized by two, widely separated time constants. We speculate that the short time constant (∼14 s) results from the viscous response of the matrix to the change in cell-wall shape as a joint is stretched, a response that allows the material both to remain flexible and to dissipate energy as a frond is lashed by waves. We propose that the long time constant (∼35 h), is governed by the shearing of the matrix between cellulose fibrils. The resulting high apparent viscosity ensures that joints avoid accumulating lethal deformation in the course of a frond's lifetime. Our synthesis of experimental measurements allows us to draw a chain of mechanistic inference from molecules to cell walls to fronds and community ecology.

  View details for DOI 10.1242/jeb.138867

  View details for Web of Science ID 000378097500014

  View details for PubMedID 27307542

• The extraordinary joint material of an articulated coralline alga. I. Mechanical characterization of a key adaptation JOURNAL OF EXPERIMENTAL BIOLOGY Denny, M. W., King, F. A. 2016; 219 (12): 1833-1842

  Abstract

  Flexibility is key to survival for seaweeds exposed to the extreme hydrodynamic environment of wave-washed rocky shores. This poses a problem for coralline algae, whose calcified cell walls make them rigid. Through the course of evolution, erect coralline algae have solved this problem by incorporating joints (genicula) into their morphology, allowing their fronds to be as flexible as those of uncalcified seaweeds. To provide the flexibility required by this structural innovation, the joint material of Calliarthron cheilosporioides, a representative articulated coralline alga, relies on an extraordinary tissue that is stronger, more extensible and more fatigue resistant than the tissue of other algal fronds. Here, we report on experiments that reveal the viscoelastic properties of this material. On the one hand, its compliance is independent of the rate of deformation across a wide range of deformation rates, a characteristic of elastic solids. This deformation rate independence allows joints to maintain their flexibility when loaded by the unpredictable - and often rapidly imposed - hydrodynamic force of breaking waves. On the other hand, the genicular material has viscous characteristics that similarly augment its function. The genicular material dissipates much of the energy absorbed as a joint is deformed during cyclic wave loading, which potentially reduces the chance of failure by fatigue, and the material accrues a limited amount of deformation through time. This limited creep increases the flexibility of the joints while preventing them from gradually stretching to the point of failure. These new findings provide the basis for understanding how the microscale architecture of genicular cell walls results in the adaptive mechanical properties of coralline algal joints.

  View details for DOI 10.1242/jeb.138859

  View details for Web of Science ID 000378097500013

  View details for PubMedID 27307541

• Ecological Mechanics: Principles of Life's Physical Interactions Denny, M. W. Princeton University Press. 2016
• Experimental determination of the hydrodynamic forces responsible for wave impact events JOURNAL OF EXPERIMENTAL MARINE BIOLOGY AND ECOLOGY Jensen, M. M., Denny, M. W. 2015; 469: 123-130

  View details for DOI 10.1016/j.jembe.2015.04.013

  View details for Web of Science ID 000356545200016

• Thermal variation, thermal extremes and the physiological performance of individuals JOURNAL OF EXPERIMENTAL BIOLOGY Dowd, W. W., King, F. A., Denny, M. W. 2015; 218 (12): 1956-1967

  View details for DOI 10.1242/jeb.114926

  View details for Web of Science ID 000356497200017

• Thermal variation, thermal extremes and the physiological performance of individuals. journal of experimental biology Dowd, W. W., King, F. A., Denny, M. W. 2015; 218: 1956-1967

  Abstract

  In this review we consider how small-scale temporal and spatial variation in body temperature, and biochemical/physiological variation among individuals, affect the prediction of organisms' performance in nature. For 'normal' body temperatures - benign temperatures near the species' mean - thermal biology traditionally uses performance curves to describe how physiological capabilities vary with temperature. However, these curves, which are typically measured under static laboratory conditions, can yield incomplete or inaccurate predictions of how organisms respond to natural patterns of temperature variation. For example, scale transition theory predicts that, in a variable environment, peak average performance is lower and occurs at a lower mean temperature than the peak of statically measured performance. We also demonstrate that temporal variation in performance is minimized near this new 'optimal' temperature. These factors add complexity to predictions of the consequences of climate change. We then move beyond the performance curve approach to consider the effects of rare, extreme temperatures. A statistical procedure (the environmental bootstrap) allows for long-term simulations that capture the temporal pattern of extremes (a Poisson interval distribution), which is characterized by clusters of events interspersed with long intervals of benign conditions. The bootstrap can be combined with biophysical models to incorporate temporal, spatial and physiological variation into evolutionary models of thermal tolerance. We conclude with several challenges that must be overcome to more fully develop our understanding of thermal performance in the context of a changing climate by explicitly considering different forms of small-scale variation. These challenges highlight the need to empirically and rigorously test existing theories.

  View details for DOI 10.1242/jeb.114926

  View details for PubMedID 26085672

• Warm microhabitats drive both increased respiration and growth rates of intertidal consumers MARINE ECOLOGY PROGRESS SERIES Miller, L. P., Allen, B. J., King, F. A., Chilin, D. R., Reynoso, V. M., Denny, M. W. 2015; 522: 127-143

  View details for DOI 10.3354/meps11117

  View details for Web of Science ID 000350667800009

• United We Fail: Group versus Individual Strength in the California Sea Mussel, Mytilus californianus BIOLOGICAL BULLETIN Cole, A., Denny, M. 2014; 227 (1): 61-67

  View details for Web of Science ID 000341728600007

• United we fail: Group versus individual strength in the California sea mussel, Mytilus californianus. Biological bulletin Cole, A., Denny, M. 2014; 227 (1): 61-67

  Abstract

  The mussel Mytilus californianus is a dominant competitor for space on wave-swept rocky shores, where it forms dense beds. Byssal threads anchor each mussel both to the substratum and to neighbors, allowing mussels to resist the onslaught of waves. When incident hydrodynamic stress exceeds a mussel's tenacity, the threads are broken, the mussel is dislodged, and a gap is opened in the bed. Here, we show that when groups of contiguous bed mussels experience similar hydrodynamic forces, they collectively have a lower tenacity than when force is applied to a single individual. Lowered group tenacity leads to greater probabilities of dislodgment, with ramifications for community dynamics and species diversity.

  View details for PubMedID 25216503

• Aperture effects in squid jet propulsion JOURNAL OF EXPERIMENTAL BIOLOGY Staaf, D. J., Gilly, W. F., Denny, M. W. 2014; 217 (9): 1588-1600

  Abstract

  Squid are the largest jet propellers in nature as adults, but as paralarvae they are some of the smallest, faced with the inherent inefficiency of jet propulsion at a low Reynolds number. In this study we describe the behavior and kinematics of locomotion in 1 mm paralarvae of Dosidicus gigas, the smallest squid yet studied. They swim with hop-and-sink behavior and can engage in fast jets by reducing the size of the mantle aperture during the contraction phase of a jetting cycle. We go on to explore the general effects of a variable mantle and funnel aperture in a theoretical model of jet propulsion scaled from the smallest (1 mm mantle length) to the largest (3 m) squid. Aperture reduction during mantle contraction increases propulsive efficiency at all squid sizes, although 1 mm squid still suffer from low efficiency (20%) because of a limited speed of contraction. Efficiency increases to a peak of 40% for 1 cm squid, then slowly declines. Squid larger than 6 cm must either reduce contraction speed or increase aperture size to maintain stress within maximal muscle tolerance. Ecological pressure to maintain maximum velocity may lead them to increase aperture size, which reduces efficiency. This effect might be ameliorated by nonaxial flow during the refill phase of the cycle. Our model's predictions highlight areas for future empirical work, and emphasize the existence of complex behavioral options for maximizing efficiency at both very small and large sizes.

  View details for DOI 10.1242/jeb.082271

  View details for Web of Science ID 000335583500029

  View details for PubMedID 24501132

• Indefatigable: an erect coralline alga is highly resistant to fatigue. journal of experimental biology Denny, M., Mach, K., Tepler, S., Martone, P. 2013; 216: 3772-3780

  Abstract

  Intertidal organisms are subjected to intense hydrodynamic forces as waves break on the shore. These repeated insults can cause a plant or animal's structural materials to fatigue and fail, even though no single force would be sufficient to break the organism. Indeed, the survivorship and maximum size of at least one species of seaweed is set by the accumulated effects of small forces rather than the catastrophic imposition of a single lethal force. One might suppose that fatigue would be especially potent in articulated coralline algae, in which the strain of the entire structure is concentrated in localized joints, the genicula. However, previous studies of joint morphology suggest an alternative hypothesis. Each geniculum is composed of a single tier of cells, which are attached at their ends to the calcified segments of the plant (the intergenicula) but have minimal connection to each other along their lengths. This lack of neighborly attachment potentially allows the weak interfaces between cells to act as 'crack stoppers', inhibiting the growth of fatigue cracks. We tested this possibility by repeatedly loading fronds of Calliarthron cheilosporioides, a coralline alga common on wave-washed shores in California. When repeatedly loaded to 50-80% of its breaking strength, C. cheilosporioides commonly survives more than a million stress cycles, with a record of 51 million. We show how this extraordinary fatigue resistance interacts with the distribution of wave-induced water velocities to set the limits to size in this species.

  View details for DOI 10.1242/jeb.091264

  View details for PubMedID 24068348

• Interaction of waves and currents with kelp forests (Macrocystis pyrifera): Insights from a dynamically scaled laboratory model LIMNOLOGY AND OCEANOGRAPHY Rosman, J. H., Denny, M. W., Zeller, R. B., Monismith, S. G., Koseff, J. R. 2013; 58 (3): 790-802

  View details for DOI 10.4319/lo.2013.58.3.0790

  View details for Web of Science ID 000322491100003

• Natural intrusions of hypoxic, low pH water into nearshore marine environments on the California coast CONTINENTAL SHELF RESEARCH Booth, J. A., McPhee-Shaw, E. E., Chua, P., Kingsley, E., Denny, M., Phillips, R., Bograd, S. J., Zeidberg, L. D., Gilly, W. F. 2012; 45: 108-115

  View details for DOI 10.1016/j.csr.2012.06.009

  View details for Web of Science ID 000308899500011

• Biophysics, environmental stochasticity, and the evolution of thermal safety margins in intertidal limpets JOURNAL OF EXPERIMENTAL BIOLOGY Denny, M. W., DOWD, W. W. 2012; 215 (6): 934-947

  Abstract

  As the air temperature of the Earth rises, ecological relationships within a community might shift, in part due to differences in the thermal physiology of species. Prediction of these shifts - an urgent task for ecologists - will be complicated if thermal tolerance itself can rapidly evolve. Here, we employ a mechanistic approach to predict the potential for rapid evolution of thermal tolerance in the intertidal limpet Lottia gigantea. Using biophysical principles to predict body temperature as a function of the state of the environment, and an environmental bootstrap procedure to predict how the environment fluctuates through time, we create hypothetical time-series of limpet body temperatures, which are in turn used as a test platform for a mechanistic evolutionary model of thermal tolerance. Our simulations suggest that environmentally driven stochastic variation of L. gigantea body temperature results in rapid evolution of a substantial 'safety margin': the average lethal limit is 5-7°C above the average annual maximum temperature. This predicted safety margin approximately matches that found in nature, and once established is sufficient, in our simulations, to allow some limpet populations to survive a drastic, century-long increase in air temperature. By contrast, in the absence of environmental stochasticity, the safety margin is dramatically reduced. We suggest that the risk of exceeding the safety margin, rather than the absolute value of the safety margin, plays an underappreciated role in the evolution of thermal tolerance. Our predictions are based on a simple, hypothetical, allelic model that connects genetics to thermal physiology. To move beyond this simple model - and thereby potentially to predict differential evolution among populations and among species - will require significant advances in our ability to translate the details of thermal histories into physiological and population-genetic consequences.

  View details for DOI 10.1242/jeb.058958

  View details for Web of Science ID 000300718100008

  View details for PubMedID 22357587

• The fine art of surfacing: Its efficacy in broadcast spawning JOURNAL OF THEORETICAL BIOLOGY Molacek, J., Denny, M., Bush, J. W. 2012; 294: 40-47

  Abstract

  Many organisms reproduce by releasing gametes into the surrounding fluid. For some such broadcast spawners, gametes are positively or negatively buoyant, and, as a result, fertilization occurs on a two-dimensional surface rather than in the bulk of the air or water. We here rationalize this behaviour by considering the encounter rates of gametes on the surface and in the fluid bulk. The advantage of surfacing is quantified by considering an infinitely wide body of water of constant depth. Differential loss rates at the surface and in the bulk are considered and their influence on the robustness of surface search assessed. For small and moderate differential loss rates, the advantage of surfacing is very robust and significant; only for large loss rate differences can the advantage of surfacing be nullified.

  View details for DOI 10.1016/j.jtbi.2011.10.013

  View details for Web of Science ID 000299353300005

  View details for PubMedID 22019506

• Scaling Up in Ecology: Mechanistic Approaches ANNUAL REVIEW OF ECOLOGY, EVOLUTION, AND SYSTEMATICS, VOL 43 Denny, M., Benedetti-Cecchi, L. 2012; 43: 1-22

  View details for DOI 10.1146/annurev-ecolsys-102710-145103

  View details for Web of Science ID 000311573500001

• Anchor Ice and Benthic Disturbance in Shallow Antarctic Waters: Interspecific Variation in Initiation and Propagation of Ice Crystals BIOLOGICAL BULLETIN Denny, M., Dorgan, K. M., Evangelista, D., Hettinger, A., Leichter, J., Ruder, W. C., Tuval, I. 2011; 221 (2): 155-163

  Abstract

  Sea ice typically forms at the ocean's surface, but given a source of supercooled water, an unusual form of ice--anchor ice--can grow on objects in the water column or at the seafloor. For several decades, ecologists have considered anchor ice to be an important agent of disturbance in the shallow-water benthic communities of McMurdo Sound, Antarctica, and potentially elsewhere in polar seas. Divers have documented anchor ice in the McMurdo communities, and its presence coincides with reduced abundance of the sponge Homaxinella balfourensis, which provides habitat for a diverse assemblage of benthic organisms. However, the mechanism of this disturbance has not been explored. Here we show interspecific differences in anchor-ice formation and propagation characteristics for Antarctic benthic organisms. The sponges H. balfourensis and Suberites caminatus show increased incidence of formation and accelerated spread of ice crystals compared to urchins and sea stars. Anchor ice also forms readily on sediments, from which it can grow and adhere to organisms. Our results are consistent with, and provide a potential first step toward, an explanation for disturbance patterns observed in shallow polar benthic communities. Interspecific differences in ice formation raise questions about how surface tissue characteristics such as surface area, rugosity, and mucus coating affect ice formation on invertebrates.

  View details for Web of Science ID 000296594800002

  View details for PubMedID 22042434

• Grand Opportunities: Strategies for Addressing Grand Challenges in Organismal Animal Biology INTEGRATIVE AND COMPARATIVE BIOLOGY Stillman, J. H., Denny, M., Padilla, D. K., Wake, M. H., Patek, S., Tsukimura, B. 2011; 51 (1): 7-13

  View details for DOI 10.1093/icb/icr052

  View details for Web of Science ID 000292313800001

  View details for PubMedID 21659394

• Importance of Behavior and Morphological Traits for Controlling Body Temperature in Littorinid Snails BIOLOGICAL BULLETIN Miller, L. P., Denny, M. W. 2011; 220 (3): 209-223

  Abstract

  For organisms living in the intertidal zone, temperature is an important selective agent that can shape species distributions and drive phenotypic variation among populations. Littorinid snails, which occupy the upper limits of rocky shores and estuaries worldwide, often experience extreme high temperatures and prolonged aerial emersion during low tides, yet their robust physiology--coupled with morphological and behavioral traits--permits these gastropods to persist and exert strong grazing control over algal communities. We use a mechanistic heat-budget model to compare the effects of behavioral and morphological traits on the body temperatures of five species of littorinid snails under natural weather conditions. Model predictions and field experiments indicate that, for all five species, the relative contribution of shell color or sculpturing to temperature regulation is small, on the order of 0.2-2 °C, while behavioral choices such as removing the foot from the substratum or reorienting the shell can lower body temperatures by 2-4 °C on average. Temperatures in central California rarely exceeded the thermal tolerance limits of the local littorinid species during the study period, but at sites where snails are regularly exposed to extreme high temperatures, the functional significance of the tested traits may be important. The mechanistic approach used here provides the ability to gauge the importance of behavioral and morphological traits for controlling body temperature as species approach their physiological thresholds.

  View details for Web of Science ID 000292532300006

  View details for PubMedID 21712229

• Failure by fatigue in the field: a model of fatigue breakage for the macroalga Mazzaella, with validation JOURNAL OF EXPERIMENTAL BIOLOGY Mach, K. J., Tepler, S. K., Staaf, A. V., Bohnhoff, J. C., Denny, M. W. 2011; 214 (9): 1571-1585

  Abstract

  Seaweeds inhabiting the extreme hydrodynamic environment of wave-swept shores break frequently. However, traditional biomechanical analyses, evaluating breakage due to the largest individual waves, have perennially underestimated rates of macroalgal breakage. Recent laboratory testing has established that some seaweeds fail by fatigue, accumulating damage over a series of force impositions. Failure by fatigue may thus account, in part, for the discrepancy between prior breakage predictions, based on individual not repeated wave forces, and reality. Nonetheless, the degree to which fatigue breaks seaweeds on wave-swept shores remains unknown. Here, we developed a model of fatigue breakage due to wave-induced forces for the macroalga Mazzaella flaccida. To test model performance, we made extensive measurements of M. flaccida breakage and of wave-induced velocities experienced by the macroalga. The fatigue-breakage model accounted for significantly more breakage than traditional prediction methods. For life history phases modeled most accurately, 105% (for female gametophytes) and 79% (for tetrasporophytes) of field-observed breakage was predicted, on average. When M. flaccida fronds displayed attributes such as temperature stress and substantial tattering, the fatigue-breakage model underestimated breakage, suggesting that these attributes weaken fronds and lead to more rapid breakage. Exposure to waves had the greatest influence on model performance. At the most wave-protected sites, the model underpredicted breakage, and at the most wave-exposed sites, it overpredicted breakage. Overall, our fatigue-breakage model strongly suggests that, in addition to occurring predictably in the laboratory, fatigue-induced breakage of M. flaccida occurs on wave-swept shores.

  View details for DOI 10.1242/jeb.051623

  View details for Web of Science ID 000289477400025

  View details for PubMedID 21490265

• An inexpensive instrument for measuring wave exposure and water velocity LIMNOLOGY AND OCEANOGRAPHY-METHODS Figurski, J. D., Malone, D., Lacy, J. R., Denny, M. 2011; 9: 204-214

  View details for DOI 10.4319/lom.2011.9.204

  View details for Web of Science ID 000294604500004

• Spreading the risk: Small-scale body temperature variation among intertidal organisms and its implications for species persistence JOURNAL OF EXPERIMENTAL MARINE BIOLOGY AND ECOLOGY Denny, M. W., Dowd, W. W., Bilir, L., Mach, K. J. 2011; 400 (1-2): 175-190

  View details for DOI 10.1016/j.jembe.2011.02.006

  View details for Web of Science ID 000291143900016

• Preference Versus Performance: Body Temperature of the Intertidal Snail Chlorostoma funebralis BIOLOGICAL BULLETIN Tepler, S., Mach, K., Denny, M. 2011; 220 (2): 107-117

  Abstract

  Evolutionary theory predicts that, in variable environments, it is advantageous for ectothermic organisms to prefer a body temperature slightly below the physiological optimum. This theory works well for many terrestrial organisms but has not been tested for animals inhabiting the hypervariable physical environment of intertidal shores. In laboratory experiments, we allowed the intertidal snail Chlorostoma funebralis to position itself on a temperature gradient, then measured its thermal preference and determined an index of how its performance varied with temperature. Snails performed a biased random walk along the temperature gradient, which, contrary to expectations, caused them to aggregate where body temperature was 15 to 17 °C below their temperature of optimum performance and near the species' lower thermal limit. This "cold-biased" behavioral response may guide snails to refuges in shaded cracks and crevices, but potentially precludes C. funebralis from taking full advantage of its physiological capabilities.

  View details for Web of Science ID 000290596200005

  View details for PubMedID 21551447

• Diatom sinking speeds: Improved predictions and insight from a modified Stokes' law LIMNOLOGY AND OCEANOGRAPHY Miklasz, K. A., Denny, M. W. 2010; 55 (6): 2513-2525

  View details for DOI 10.4319/lo.2010.55.6.2513

  View details for Web of Science ID 000287844700023

• Currents and turbulence within a kelp forest (Macrocystis pyrifera): Insights from a dynamically scaled laboratory model LIMNOLOGY AND OCEANOGRAPHY Rosman, J. H., Monismith, S. G., Denny, M. W., Koseff, J. R. 2010; 55 (3): 1145-1158

  View details for DOI 10.4319/lo.2010.55.3.1145

  View details for Web of Science ID 000277650900016

• Organismal climatology: analyzing environmental variability at scales relevant to physiological stress JOURNAL OF EXPERIMENTAL BIOLOGY Helmuth, B., Broitman, B. R., Yamane, L., Gilman, S. E., Mach, K., Mislan, K. A., Denny, M. W. 2010; 213 (6): 995-1003

  Abstract

  Predicting when, where and with what magnitude climate change is likely to affect the fitness, abundance and distribution of organisms and the functioning of ecosystems has emerged as a high priority for scientists and resource managers. However, even in cases where we have detailed knowledge of current species' range boundaries, we often do not understand what, if any, aspects of weather and climate act to set these limits. This shortcoming significantly curtails our capacity to predict potential future range shifts in response to climate change, especially since the factors that set range boundaries under those novel conditions may be different from those that set limits today. We quantitatively examine a nine-year time series of temperature records relevant to the body temperatures of intertidal mussels as measured using biomimetic sensors. Specifically, we explore how a 'climatology' of body temperatures, as opposed to long-term records of habitat-level parameters such as air and water temperatures, can be used to extrapolate meaningful spatial and temporal patterns of physiological stress. Using different metrics that correspond to various aspects of physiological stress (seasonal means, cumulative temperature and the return time of extremes) we show that these potential environmental stressors do not always occur in synchrony with one another. Our analysis also shows that patterns of animal temperature are not well correlated with simple, commonly used metrics such as air temperature. Detailed physiological studies can provide guidance to predicting the effects of global climate change on natural ecosystems but only if we concomitantly record, archive and model environmental signals at appropriate scales.

  View details for DOI 10.1242/jeb.038463

  View details for Web of Science ID 000275002600021

  View details for PubMedID 20190124

• Marine Ecomechanics ANNUAL REVIEW OF MARINE SCIENCE Denny, M. W., Gaylord, B. 2010; 2: 89-114

  Abstract

  The emerging field of marine ecomechanics provides an explicit physical framework for exploring interactions among marine organisms and between these organisms and their environments. It exhibits particular utility through its construction of predictive, mechanistic models, a number of which address responses to changing climatic conditions. Examples include predictions of (a) the change in relative abundance of corals as a function of colony morphology, ocean acidity, and storm intensity; (b) the rate of disturbance and patch formation in beds of mussels, a competitive dominant on many intertidal shores; (c) the dispersal and recruitment patterns of giant kelps, an important nearshore foundation species; (d) the effects of turbulence on external fertilization, a widespread method of reproduction in the sea; and (e) the long-term incidence of extreme ecological events. These diverse examples emphasize the breadth of marine ecomechanics. Indeed, its principles can be applied to any ecological system.

  View details for DOI 10.1146/annurev-marine-120308-081011

  View details for Web of Science ID 000273985300004

  View details for PubMedID 21141659

• Confronting the physiological bottleneck: A challenge from ecomechanics INTEGRATIVE AND COMPARATIVE BIOLOGY Denny, M., Helmuth, B. 2009; 49 (3): 197-201

  View details for DOI 10.1093/icb/icp070

  View details for Web of Science ID 000269962300001

  View details for PubMedID 20607137

• On the prediction of extreme ecological events ECOLOGICAL MONOGRAPHS Denny, M. W., Hunt, L. J., Miller, L. P., Harley, C. D. 2009; 79 (3): 397-421

  View details for Web of Science ID 000268011200003

• The role of temperature and desiccation stress in limiting the local-scale distribution of the owl limpet, Lottia gigantea FUNCTIONAL ECOLOGY Miller, L. P., Harley, C. D., Denny, M. W. 2009; 23 (4): 756-767

  View details for DOI 10.1111/j.1365-2435.2009.01567.x

  View details for Web of Science ID 000267539000011

• Thermal stress and morphological adaptations in limpets FUNCTIONAL ECOLOGY Harley, C. D., Denny, M. W., Mach, K. J., Miller, L. P. 2009; 23 (2): 292-301

  View details for DOI 10.1111/j.1365-2435.2008.01496.x

  View details for Web of Science ID 000264185500009

• Discovery of Lignin in Seaweed Reveals Convergent Evolution of Cell-Wall Architecture CURRENT BIOLOGY Martone, P. T., Estevez, J. M., Lu, F., Ruel, K., Denny, M. W., Somerville, C., Ralph, J. 2009; 19 (2): 169-175

  Abstract

  Lignified cell walls are widely considered to be key innovations in the evolution of terrestrial plants from aquatic ancestors some 475 million years ago. Lignins, complex aromatic heteropolymers, stiffen and fortify secondary cell walls within xylem tissues, creating a dense matrix that binds cellulose microfibrils and crosslinks other wall components, thereby preventing the collapse of conductive vessels, lending biomechanical support to stems, and allowing plants to adopt an erect-growth habit in air. Although "lignin-like" compounds have been identified in primitive green algae, the presence of true lignins in nonvascular organisms, such as aquatic algae, has not been confirmed. Here, we report the discovery of secondary walls and lignin within cells of the intertidal red alga Calliarthron cheilosporioides. Until now, such developmentally specialized cell walls have been described only in vascular plants. The finding of secondary walls and lignin in red algae raises many questions about the convergent or deeply conserved evolutionary history of these traits, given that red algae and vascular plants probably diverged more than 1 billion years ago.

  View details for DOI 10.1016/j.cub.2008.12.031

  View details for Web of Science ID 000263012600030

  View details for PubMedID 19167225

• Limits to running speed in dogs, horses and humans JOURNAL OF EXPERIMENTAL BIOLOGY Denny, M. W. 2008; 211 (24): 3836-3849

  Abstract

  Are there absolute limits to the speed at which animals can run? If so, how close are present-day individuals to these limits? I approach these questions by using three statistical models and data from competitive races to estimate maximum running speeds for greyhounds, thoroughbred horses and elite human athletes. In each case, an absolute speed limit is definable, and the current record approaches that predicted maximum. While all such extrapolations must be used cautiously, these data suggest that there are limits to the ability of either natural or artificial selection to produce ever faster dogs, horses and humans. Quantification of the limits to running speed may aid in formulating and testing models of locomotion.

  View details for DOI 10.1242/jeb.024968

  View details for Web of Science ID 000261260500013

  View details for PubMedID 19043056

• Flow Forces on Seaweeds: Field Evidence for Roles of Wave Impingement and Organism Inertia BIOLOGICAL BULLETIN Gaylord, B., Denny, M. W., Koehl, M. A. 2008; 215 (3): 295-308

  Abstract

  Hydrodynamic forces dislodge and kill large numbers of organisms in intertidal and subtidal habitats along rocky shores. Although this feature of wave-driven water motion is well recognized, the mechanics of force imposition on compliant organisms is incompletely understood. Here we undertake a field examination of two processes that are thought to impose many of the more dangerous forces that act on flexible benthic seaweeds: impingement of breaking waves directly on emergent organisms, and inertial effects tied to the rapid deceleration of mass that occurs when a passively moving but attached organism abruptly reaches the extent of its range of motion. We focus on two common and important seaweed species: one intertidal kelp (Egregia menziesii) and one subtidal kelp (Macrocystis pyrifera). Results support the concept that wave impingement and inertial effects produce intermittent force transients whose magnitudes commonly exceed values readily attributable to drag. Peak force transients are elevated by as much as a factor of 3 relative to drag in both small and large individuals, consistent with smaller seaweeds being more susceptible to brief impingement forces, and larger seaweeds being more vulnerable to inertial forces. Because both wave impingement and inertial effects vary with the size of an organism, they may have the potential to influence the demographics of physical disturbance in an array of flexible species.

  View details for Web of Science ID 000262021400009

  View details for PubMedID 19098150

• To bend a coralline: effect of joint morphology on flexibility and stress amplification in an articulated calcified seaweed JOURNAL OF EXPERIMENTAL BIOLOGY Martone, P. T., Denny, M. W. 2008; 211 (21): 3421-3432

  Abstract

  Previous studies have demonstrated that fleshy seaweeds resist wave-induced drag forces in part by being flexible. Flexibility allows fronds to 'go with the flow', reconfiguring into streamlined shapes and reducing frond area projected into flow. This paradigm extends even to articulated coralline algae, which produce calcified fronds that are flexible only because they have distinct joints (genicula). The evolution of flexibility through genicula was a major event that allowed articulated coralline algae to grow elaborate erect fronds in wave-exposed habitats. Here we describe the mechanics of genicula in the articulated coralline Calliarthron and demonstrate how segmentation affects bending performance and amplifies bending stresses within genicula. A numerical model successfully predicted deflections of articulated fronds by assuming genicula to be assemblages of cables connecting adjacent calcified segments (intergenicula). By varying the dimensions of genicula in the model, we predicted the optimal genicular morphology that maximizes flexibility while minimizing stress amplification. Morphological dimensions of genicula most prone to bending stresses (i.e. genicula near the base of fronds) match model predictions.

  View details for DOI 10.1242/jeb.020479

  View details for Web of Science ID 000260165100017

  View details for PubMedID 18931315

• To break a coralline: mechanical constraints on the size and survival of a wave-swept seaweed JOURNAL OF EXPERIMENTAL BIOLOGY Martone, P. T., Denny, M. W. 2008; 211 (21): 3433-3441

  Abstract

  Previous studies have hypothesized that wave-induced drag forces may constrain the size of intertidal organisms by dislodging or breaking organisms that exceed some critical dimension. In this study, we explored constraints on the size of the articulated coralline alga Calliarthron, which thrives in wave-exposed intertidal habitats. Its ability to survive depends critically upon its segmented morphology (calcified segments separated by flexible joints or ;genicula'), which allows otherwise rigid fronds to bend and thereby reduce drag. However, bending also amplifies stress within genicula near the base of fronds. We quantified breakage of genicula in bending by applying known forces to fronds until they broke. Using a mathematical model, we demonstrate the mitigating effect of neighboring fronds on breakage and show that fronds growing within dense populations are no more likely to break in bending than in tension, suggesting that genicular morphology approaches an engineering optimum, possibly reflecting adaptation to hydrodynamic stress. We measured drag in a re-circulating water flume (0.23-3.6 m s(-1)) and a gravity-accelerated water flume, which generates jets of water that mimic the impact of breaking waves (6-10 m s(-1)). We used frond Reynolds number to extrapolate drag coefficients in the field and to predict water velocities necessary to break fronds of given sizes. Laboratory data successfully predicted frond sizes found in the field, suggesting that, although Calliarthron is well adapted to resist breakage, wave forces may ultimately limit the size of intertidal fronds.

  View details for DOI 10.1242/jeb.020495

  View details for Web of Science ID 000260165100018

  View details for PubMedID 18931316

• Desiccation protection and disruption: A trade-off for an intertidal marine alga JOURNAL OF PHYCOLOGY Hunt, L. J., Denny, M. W. 2008; 44 (5): 1164-1170

  View details for DOI 10.1111/j.1529-8817.2008.00578.x

  View details for Web of Science ID 000259866800008

• DESICCATION PROTECTION AND DISRUPTION: A TRADE-OFF FOR AN INTERTIDAL MARINE ALGA(1). Journal of phycology Hunt, L. J., Denny, M. W. 2008; 44 (5): 1164-1170

  Abstract

  For marine algae, the benefits of drying out are often overshadowed by the stresses involved. Here we used laboratory and field experiments to examine both the costs and benefits of desiccation in the intertidal turf alga Endocladia muricata (Endlichter) J. Agardh. Laboratory experiments showed that when Endocladia is dry, photosynthesis stops, but thermotolerance increases to the point that the alga is protected from heat-induced mortality. Drying rates measured in a wind tunnel, combined with tidal data and measured wave splash, indicate that a substantial fraction of the year is spent "drying out" (∼30% of the total time available for photosynthesis). During these periods, the rate of drying determines how much time is spent hydrated and potentially engaged in photosynthesis, but also vulnerable to high temperatures. Turf algae such as Endocladia dry from the edge of a clump inward. Consequently, the clump center remains hydrated longer than the clump edge. The resulting regionalization of a clump results in notable patterns of frond mortality ("fairy rings," and zoned patterns of frond bleaching) within the Endocladia zone.

  View details for DOI 10.1111/j.1529-8817.2008.00578.x

  View details for PubMedID 27041713

• Biophysics - The intrigue of the interface SCIENCE Denny, M. W. 2008; 320 (5878): 886-886

  View details for DOI 10.1126/science.1158189

  View details for Web of Science ID 000255868300030

  View details for PubMedID 18487182

• Hydrodynamic forces and surface topography: Centimeter-scale spatial variation in wave forces LIMNOLOGY AND OCEANOGRAPHY O'Donnell, M. J., Denny, M. W. 2008; 53 (2): 579-588

  View details for Web of Science ID 000256498700017

• Techniques for predicting the lifetimes of wave-swept macroalgae: a primer on fracture mechanics and crack growth JOURNAL OF EXPERIMENTAL BIOLOGY Mach, K. J., Nelson, D. V., Denny, M. W. 2007; 210 (13): 2213-2230

  Abstract

  Biomechanical analyses of intertidal and shallow subtidal seaweeds have elucidated ways in which these organisms avoid breakage in the presence of exceptional hydrodynamic forces imposed by pounding surf. However, comparison of algal material properties to maximum hydrodynamic forces predicts lower rates of breakage and dislodgment than are actually observed. Why the disparity between prediction and reality? Most previous research has measured algal material properties during a single application of force, equivalent to a single wave rushing past an alga. In contrast, intertidal macroalgae may experience more than 8000 waves a day. This repeated loading can cause cracks - introduced, for example, by herbivory or abrasion - to grow and eventually cause breakage, yet fatigue crack growth has not previously been taken into account. Here, we present methods from the engineering field of fracture mechanics that can be used to assess consequences of repeated force imposition for seaweeds. These techniques allow quantification of crack growth in wave-swept macroalgae, a first step towards considering macroalgal breakage in the realistic context of repeated force imposition. These analyses can also be applied to many other soft materials.

  View details for DOI 10.1242/jeb.001560

  View details for Web of Science ID 000248304900009

  View details for PubMedID 17575028

• Death by small forces: a fracture and fatigue analysis of wave-swept macroalgae JOURNAL OF EXPERIMENTAL BIOLOGY Mach, K. J., Hale, B. B., Denny, M. W., Nelson, D. V. 2007; 210 (13): 2231-2243

  Abstract

  Wave-swept macroalgae are subjected to large hydrodynamic forces as each wave breaks on shore, loads that are repeated thousands of times per day. Previous studies have shown that macroalgae can easily withstand isolated impositions of maximal field forces. Nonetheless, macroalgae break frequently. Here we investigate the possibility that repeated loading by sub-lethal forces can eventually cause fracture by fatigue. We determine fracture toughness, in the form of critical strain energy release rate, for several flat-bladed macroalgae, thereby assessing their resistance to complete fracture in the presence of cracks. Critical energy release rates are evaluated through single-edge-notch, pull-to-break tests and single-edge-notch, repeated-loading tests. Crack growth at sub-critical energy release rates is measured in repeated-loading tests, providing a first assessment of algal breakage under conditions of repeated loading. We then estimate the number of imposed waves required for un-notched algal blades to reach the point of complete fracture. We find that, if not checked by repair, fatigue crack growth from repeated sub-lethal stresses may completely fracture individuals within days. Our results suggest that fatigue may play an important role in macroalgal breakage.

  View details for DOI 10.1242/jeb.001578

  View details for Web of Science ID 000248304900010

  View details for PubMedID 17575029

• Ocean waves, nearshore ecology, and natural selection AQUATIC ECOLOGY Denny, M. W. 2006; 40 (4): 439-461

  View details for DOI 10.1007/s10452-004-5409-8

  View details for Web of Science ID 000242144700003

• Jet propulsion in the cold: mechanics of swimming in the Antarctic scallop Adamussium colbecki JOURNAL OF EXPERIMENTAL BIOLOGY Denny, M., Miller, L. 2006; 209 (22): 4503-4514

  Abstract

  Unlike most bivalves, scallops are able to swim, relying on a shell with reduced mass and streamlined proportions, a large fast-twitch adductor muscle and the elastic characteristics of the shell's hinge. Despite these adaptations, swimming in scallops is never far from failure, and it is surprising to find a swimming scallop in Antarctica, where low temperature increases the viscosity of seawater, decreases the power output of the adductor muscle and potentially compromises the energy storage capability of the hinge material (abductin, a protein rubber). How does the Antarctic scallop, Adamussium colbecki, cope with the cold? Its shell mass is substantially reduced relative to that of temperate and tropical scallops, but this potential advantage is more than offset by a drastic reduction in adductor-muscle mass. By contrast, A. colbecki's abductin maintains a higher resilience at low temperatures than does the abductin of a temperate scallop. This resilience may help to compensate for reduced muscle mass, assisting the Antarctic scallop to maintain its marginal swimming ability. However, theory suggests that this assistance should be slight, so the adaptive value of increased resilience remains open to question. The high resilience of A. colbecki abductin at low temperatures may be of interest to materials engineers.

  View details for DOI 10.1242/jeb.02538

  View details for Web of Science ID 000242132800015

  View details for PubMedID 17079720

• Hot limpets: predicting body temperature in a conductance-mediated thermal system JOURNAL OF EXPERIMENTAL BIOLOGY Denny, M. W., Harley, C. D. 2006; 209 (13): 2409-2419

  Abstract

  Living at the interface between the marine and terrestrial environments, intertidal organisms may serve as a bellwether for environmental change and a test of our ability to predict its biological consequences. However, current models do not allow us to predict the body temperature of intertidal organisms whose heat budgets are strongly affected by conduction to and from the substratum. Here, we propose a simple heat-budget model of one such animal, the limpet Lottia gigantea, and test the model against measurements made in the field. Working solely from easily measured physical and meteorological inputs, the model predicts the daily maximal body temperatures of live limpets within a fraction of a degree, suggesting that it may be a useful tool for exploring the thermal biology of limpets and for predicting effects of climate change. The model can easily be adapted to predict the temperatures of chitons, acorn barnacles, keyhole limpets, and encrusting animals and plants.

  View details for DOI 10.1242/jeb.02257

  View details for Web of Science ID 000238421800011

  View details for PubMedID 16788024

• Thermal stress on intertidal limpets: long-term hindcasts and lethal limits JOURNAL OF EXPERIMENTAL BIOLOGY Denny, M. W., Miller, L. P., Harley, C. D. 2006; 209 (13): 2420-2431

  Abstract

  When coupled with long-term meteorological records, a heat-budget model for the limpet, Lottia gigantea, provides a wealth of information regarding environmental and topographic controls of body temperature in this ecologically important species. (1) The maximum body temperature predicted for any site (37.5 degrees C) is insufficient to kill all limpets, suggesting that acute thermal stress does not set an absolute upper limit to the elevation of L. gigantea on the shore. Therefore, the upper limit must be set by behavioral responses, sublethal effects or ecological interactions. (2) Temperatures sufficient to kill limpets are reached at only a small fraction of substratum orientations and elevations and on only three occasions in 5 years. These rare predicted lethal temperatures could easily be missed in field measurements, thereby influencing the interpretation of thermal stress. (3) Body temperature is typically higher than air temperature, but maximum air temperature can nonetheless be used as an accurate predictor of maximum body temperature. Warmer air temperatures in the future may thus cause increased mortality in this intertidal species. Interpretation of the ecological effects of elevated body temperature depends strongly on laboratory measurements of thermal stress, highlighting the need for additional research on the temporal and spatial variability of thermal limits and sublethal stress. The lengthy time series of body temperatures calculated from the heat-budget model provides insight into how these physiological measurements should be conducted.

  View details for DOI 10.1242/jeb.02258

  View details for Web of Science ID 000238421800012

  View details for PubMedID 16788025

• Red algae respond to waves: Morphological and mechanical variation in Mastocarpus papillatus along a gradient of force BIOLOGICAL BULLETIN Kitzes, J. A., Denny, M. W. 2005; 208 (2): 114-119

  Abstract

  Intertidal algae are exposed to the potentially severe drag forces generated by crashing waves, and several species of brown algae respond, in part, by varying the strength of their stipe material. In contrast, previous measurements have suggested that the material strength of red algae is constant across wave exposures. Here, we reexamine the responses to drag of the intertidal red alga Mastocarpus papillatus Kutzing. By measuring individuals at multiple sites along a known force gradient, we discern responses overlooked by previous methods, which compared groups of individuals between "exposed" and "protected" sites. This improved resolution reveals that material strength and stipe cross-sectional area are both positively correlated with drag, suggesting that individual blades or populations can adjust either or both of these parameters in response to their mechanical environment. The combined effect of this variation is a stipe breaking force that is positively correlated with locally imposed drag. Owing to this response to drag, the estimated wave-imposed limit to thallus size in M. papillatus is larger than previously predicted and larger than sizes observed in the field, indicating that factors other than wave force alone constrain the size of this alga on wave-swept shores.

  View details for Web of Science ID 000228618100005

  View details for PubMedID 15837960

• Quantifying scale in ecology: Lessons from a wave-swept shore ECOLOGICAL MONOGRAPHS Denny, M. W., Helmuth, B., Leonard, G. H., Harley, C. D., Hunt, L. J., Nelson, E. K. 2004; 74 (3): 513-532

  View details for Web of Science ID 000223455600006

• Limits to phenotypic plasticity: Flow effects on barnacle feeding appendages BIOLOGICAL BULLETIN Li, N. K., Denny, M. W. 2004; 206 (3): 121-124

  Abstract

  Phenotypic plasticity, the capacity of a given genotype to produce differing morphologies in response to the environment, is widespread among marine organisms (1). For example, acorn barnacles feed by extending specialized appendages (the cirral legs) into flow, and the length of the cirri is plastic: the higher the velocity, the shorter the feeding legs (2,3). However, this effect has been explored only for flows less than 4.6 m/s, slow compared to typical flows measured at sites on wave-exposed shores. What happens at faster speeds? Leg lengths of Balanus glandula Darwin, 1854, an acorn barnacle, were measured at 15 sites in Monterey, California, across flows ranging from 0.5 to 14.0 m/s. Similar to previous findings, a plastic response in leg length was noted for the four sites with water velocities less than 3 m/s. However, no plastic response was present at the 11 sites exposed to faster velocities, despite a 4-fold variation in speed. We conclude that the velocity at which the plastic response occurs has an upper limit of 2-4 m/s, a velocity commonly exceeded within the typical habitat of this species.

  View details for Web of Science ID 000222318600001

  View details for PubMedID 15198937

• Paradox lost: answers and questions about walking on water JOURNAL OF EXPERIMENTAL BIOLOGY Denny, M. W. 2004; 207 (10): 1601-1606

  Abstract

  The mechanism by which surface tension allows water striders (members of the genus Gerris) to stand on the surface of a pond or stream is a classic example for introductory classes in animal mechanics. Until recently, however, the question of how these insects propelled themselves remained open. One plausible mechanism-creating momentum in the water via the production of capillary waves-led to a paradox: juvenile water striders move their limbs too slowly to produce waves, but nonetheless travel across the water's surface. Two recent papers demonstrate that both water striders and water-walking spiders circumvent this paradox by foregoing any reliance on waves to gain purchase on the water. Instead they use their legs as oars, and the capillary 'dimple' formed by each leg acts as the oar's blade. The resulting hydrodynamic drag produces vortices in the water, and the motion of these vortices imparts the necessary fluid momentum. These studies pave the way for a more thorough understanding of the complex mechanics of walking on water, and an exploration of how this intriguing form of locomotion scales with the size of the organism.

  View details for DOI 10.1242/jeb.00908

  View details for Web of Science ID 000221571100006

  View details for PubMedID 15073192

• Cyberkelp: an integrative approach to the modelling of flexible organisms PHILOSOPHICAL TRANSACTIONS OF THE ROYAL SOCIETY B-BIOLOGICAL SCIENCES Denny, M. W., Hale, B. B. 2003; 358 (1437): 1535-1542

  Abstract

  Biomechanical models come in a variety of forms: conceptual models; physical models; and mathematical models (both of the sort written down on paper and the sort carried out on computers). There are model structures (such as insect flight muscle and the tendons of rats' tails), model organisms (such as the flying insect, Manduca sexta), even model systems of organisms (such as the communities that live on wave-swept rocky shores). These different types of models are typically employed separately, but their value often can be enhanced if their insights are integrated. In this brief report we explore a particular example of such integration among models, as applied to flexible marine algae. A conceptual model serves as a template for the construction of a mathematical model of a model species of giant kelp, and the validity of this numerical model is tested using physical models. The validated mathematical model is then used in conjunction with a computer-controlled tensile testing apparatus to simulate the loading regime placed on algal materials. The resulting information can be used to create a more precise mathematical model.

  View details for DOI 10.1098/rstb.2003.1341

  View details for Web of Science ID 000185739500013

  View details for PubMedID 14561344

• Predicting wave exposure in the rocky intertidal zone: Do bigger waves always lead to larger forces-9 LIMNOLOGY AND OCEANOGRAPHY Helmuth, B., Denny, M. W. 2003; 48 (3): 1338-1345

  View details for Web of Science ID 000182982300039

• Modulation of wave forces on kelp canopies by alongshore currents LIMNOLOGY AND OCEANOGRAPHY Gaylord, B., Denny, M. W., Koehl, M. A. 2003; 48 (2): 860-871

  View details for Web of Science ID 000181758700024

• Extreme water velocities: Topographical amplification of wave-induced flow in the surf zone of rocky shores LIMNOLOGY AND OCEANOGRAPHY Denny, M. W., Miller, L. P., Stokes, M. D., Hunt, L. J., Helmuth, B. S. 2003; 48 (1): 1-8

  View details for Web of Science ID 000182050000001

• Revised estimates of the effects of turbulence on fertilization in the purple sea urchin, Strongylocentrotus purpuratus BIOLOGICAL BULLETIN Denny, M. W., Nelson, E. K., Mead, K. S. 2002; 203 (3): 275-277

  View details for Web of Science ID 000179814900002

  View details for PubMedID 12480718

• Blade motion and nutrient flux to the Kelp, Eisenia arborea BIOLOGICAL BULLETIN Denny, M., Roberson, L. 2002; 203 (1): 1-13

  Abstract

  Marine algae rely on currents and waves to replenish the nutrients required for photosynthesis. The interaction of algal blades with flow often involves dynamic reorientations of the blade surface (pitching and flapping) that may in turn affect nutrient flux. As a first step toward understanding the consequences of blade motion, we explore the effect of oscillatory pitching on the flux to a flat plate and to two morphologies of the kelp Eisenia arborea. In slow flow (equivalent to a water velocity of 2.7 cm s(-1)), pitching increases the time-averaged flux to both kelp morphologies, but not to the plate. In fast flow (equivalent to 20 cm s(-1) in water), pitching has negligible effect on flux regardless of shape. For many aspects of flux, the flat plate is a reliable model for the flow-protected algal blade, but predictions made from the plate would substantially underestimate the flux to the flow-exposed blade. These measurements highlight the complexities of flow-related nutrient transport and the need to understand better the dynamic interactions among nutrient flux, blade motion, blade morphology, and water flow.

  View details for Web of Science ID 000177717100001

  View details for PubMedID 12200251

• The mechanics of wave-swept algae JOURNAL OF EXPERIMENTAL BIOLOGY Denny, M., Gaylord, B. 2002; 205 (10): 1355-1362

  Abstract

  Wave-swept marine algae must contend with the hydrodynamic forces imposed by extreme water velocities. Nonetheless, they seldom have a shape that appears streamlined and they are constructed of weak, compliant materials. How do they survive? The answer is complex, but a coherent story is beginning to emerge. The combined effect of frond shape and material properties ensures that algae are flexible. In small individuals, flexibility allows the plant to reorient and reconfigure in flow, thereby assuming a streamlined shape and reducing the applied hydrodynamic force. In large individuals, flexibility allows fronds to 'go with the flow', a strategy that can at times allow the plant to avoid hydrodynamic forces but may at other times impose inertial loads. Our understanding of algal mechanics is such that we can begin to predict the survivorship of algae as a function of size, spatial distribution and wave climate.

  View details for Web of Science ID 000176013300001

  View details for PubMedID 11976348

• The rewards of chance NATURAL HISTORY Denny, M. 2001; 110 (4): 72-76

  View details for Web of Science ID 000168263800018

• Consequences of transient fluid forces for compliant benthic organisms JOURNAL OF EXPERIMENTAL BIOLOGY Gaylord, B., Hale, B. B., Denny, M. W. 2001; 204 (7): 1347-1360

  Abstract

  The diversity of form among benthic marine plants and animals on rocky coasts is remarkable. Stiff and strong organisms grow alongside others that are compliant and flimsy. Given the severity of wave action on many shores and thus the potential for the imposition of large hydrodynamic forces, this immediately raises the question of how, from this overall spectrum of designs, flexible and weak organisms survive. A number of explanations have been proposed, most emphasizing one or more of several possible advantages of deformability. Here, we explore quantitatively two of the more common of these explanations: (i) that strength can be traded against extensibility in allowing stretchy organisms to withstand transient wave forces, and (ii) that greater compliance (and thus longer organism response times) allows universally for the amelioration of brief loads. We find that, although these explanations contain kernels of validity and are accurate for a subset of conditions, they are not as general as has often been assumed.

  View details for Web of Science ID 000168205500011

  View details for PubMedID 11249843

• Hydrodynamics, shell shape, behavior and survivorship in the owl limpet Lottia gigantea JOURNAL OF EXPERIMENTAL BIOLOGY Denny, M. W., Blanchette, C. A. 2000; 203 (17): 2623-2639

  Abstract

  On wave-swept rocky shores, limpets are subjected to water velocities in excess of 20 m s(-1), which may impose large hydrodynamic forces. Despite the extreme severity of this flow environment, predictions from conical models suggest that limpets' shells are typically far from the optimal shape that would minimize the risk of dislodgment, a deviation that is allowed by the high tenacity of the limpets' adhesive system. In this study, we test this conclusion using an actual limpet. The shell of Lottia gigantea differs substantially from the hydrodynamic optimum in that its apex is displaced anteriorly to form a plough, which is used to defend the limpet's territory. The hydrodynamic effects of this shape are similar to those observed in conical models: the animal experiences an increased lift when facing into the flow and a decreased lift when the flow is at its back. However, neither effect has a substantial impact on the risk of dislodgment. When the animal is stationary, its adhesion to the substratum is very strong, and its risk of being dislodged is small regardless of its orientation to the flow and despite its sub-optimal shape. In contrast, when the animal is crawling rapidly, its adhesion is substantially decreased, and it would probably be dislodged by rapid flow even if the shell were shaped optimally. The risk of dislodgment by waves is therefore functionally independent of shell shape. In essence, despite the extremely high water velocities to which this species is subjected, its shell has had the 'permission' of the flow environment to respond to other selective factors, in particular those associated with its aggressive, territorial behavior. The result is a shell that is both a potent territorial weapon and a functional (albeit less than optimal) hydrodynamic shape.

  View details for Web of Science ID 000089453500009

  View details for PubMedID 10934004

• Limits to optimization: Fluid dynamics, adhesive strength and the evolution of shape in limpet shells JOURNAL OF EXPERIMENTAL BIOLOGY Denny, M. W. 2000; 203 (17): 2603-2622

  Abstract

  Limpets are commonly found on wave-swept rocky shores, where they may be subjected to water velocities in excess of 20 m s(-1). These extreme flows can impose large forces (lift and drag), challenging the animal's ability to adhere to the substratum. It is commonly thought that the conical shape of limpet shells has evolved in part to reduce these hydrodynamic forces while providing a large aperture for adhesion. This study documents how lift and drag actually vary with the shape of limpet-like models and uses these data to explore the potential of hydrodynamic forces to serve as a selective factor in the evolution of limpet shell morphology. At a low ratio of shell height to shell radius, lift is the dominant force, while at high ratios of height to radius drag is dominant. The risk of dislodgment is minimized when the ratio of height to radius is 1.06 and the apex is in the center of the shell. Real limpets are seldom optimally shaped, however, with a typical height-to-radius ratio of 0.68 and an apex well anterior of the shell's center. The disparity between the actual and the hydrodynamically optimal shape of shells may be due to the high tenacity of limpets' adhesive system. Most limpets adhere to the substratum so strongly that they are unlikely to be dislodged by lift or drag regardless of the shape of their shell. The evolution of a tenacious adhesion system (perhaps in response to predation) has thus preempted selection for a hydrodynamically optimal shell, allowing the shell to respond to alternative selective factors.

  View details for Web of Science ID 000089453500008

  View details for PubMedID 10934003

• Are there mechanical limits to size in wave-swept organisms? JOURNAL OF EXPERIMENTAL BIOLOGY Denny, M. 1999; 202 (23): 3463-3467

  Abstract

  Hydrodynamic forces imposed by ocean waves are thought to limit the size of nearshore plants and animals, but it has proved difficult to determine the mechanism. Explanations based on the scaling mismatch between hydrodynamic accelerational forces and the strength of organisms do not work. Mechanisms that incorporate the allometry of drag and strength accurately predict the maximal size of intertidal algae but not of animals, and internally imposed inertial forces may explain the limits to size in large kelps. The general question of size in wave-swept organisms remains open and intriguing.

  View details for Web of Science ID 000084691600024

  View details for PubMedID 10562529

• The menace of momentum: Dynamic forces on flexible organisms LIMNOLOGY AND OCEANOGRAPHY Denny, M., Gaylord, B., Helmuth, B., Daniel, T. 1998; 43 (5): 955-968

  View details for Web of Science ID 000076115800020

• Celestial mechanics, sea-level changes, and intertidal ecology BIOLOGICAL BULLETIN Denny, M. W., Paine, R. T. 1998; 194 (2): 108-115

  View details for Web of Science ID 000073859600003

• Flow and flexibility - II. The roles of size and shape in determining wave forces on the bull kelp Nereocystis luetkeana JOURNAL OF EXPERIMENTAL BIOLOGY Denny, M. W., Gaylord, B. P., Cowen, E. A. 1997; 200 (24): 3165-3183

  View details for Web of Science ID 000071294200007

• Flow and flexibility - I. Effects of size, shape and stiffness in determining wave forces on the stipitate kelps Eisenia arborea and Pterygophora californica JOURNAL OF EXPERIMENTAL BIOLOGY Gaylord, B., Denny, M. W. 1997; 200 (24): 3141-3164

  View details for Web of Science ID 000071294200006

• A biomechanical hypothesis explaining upstream movements by the freshwater snail Elimia FUNCTIONAL ECOLOGY Huryn, A. D., Denny, M. W. 1997; 11 (4): 472-483

  View details for Web of Science ID A1997XR94300008

• A conjecture on the relationship of bacterial shape to motility in rod-shaped bacteria FEMS MICROBIOLOGY LETTERS Cooper, S., Denny, M. W. 1997; 148 (2): 227-231

  View details for Web of Science ID A1997WP01700018

• Settlement of marine organisms in flow ANNUAL REVIEW OF ECOLOGY AND SYSTEMATICS Abelson, A., Denny, M. 1997; 28: 317-339

  View details for Web of Science ID 000070961400013

• Wave-induced forces on the giant kelp Macrocystis pyrifera (Agardh): Field test of a computational model JOURNAL OF EXPERIMENTAL BIOLOGY Utter, B. D., Denny, M. W. 1996; 199 (12): 2645-2654

  View details for Web of Science ID A1996VX95400011

• Pulsed delivery of subthermocline water to Conch Reef (Florida Keys) by internal tidal bores LIMNOLOGY AND OCEANOGRAPHY Leichter, J. J., Wing, S. R., Miller, S. L., Denny, M. W. 1996; 41 (7): 1490-1501

  View details for Web of Science ID A1996WU27300012

• Why the urchin lost its spines: Hydrodynamic forces and survivorship in three echinoids JOURNAL OF EXPERIMENTAL BIOLOGY Denny, M., Gaylord, B. 1996; 199 (3): 717-729

  View details for Web of Science ID A1996UB09700024

• PREDICTING PHYSICAL DISTURBANCE - MECHANISTIC APPROACHES TO THE STUDY OF SURVIVORSHIP ON WAVE-SWEPT SHORES ECOLOGICAL MONOGRAPHS Denny, M. 1995; 65 (4): 371-418

  View details for Web of Science ID A1995TC85800001

• SURVIVING HYDRODYNAMIC-FORCES IN A WAVE-SWEPT ENVIRONMENT - CONSEQUENCES OF MORPHOLOGY IN THE FEATHER BOA KELP, EGREGIA-MENZIESII (TURNER) JOURNAL OF EXPERIMENTAL MARINE BIOLOGY AND ECOLOGY FRIEDLAND, M. T., Denny, M. W. 1995; 190 (1): 109-133

  View details for Web of Science ID A1995RP04700008

• SURVIVAL IN THE SURF ZONE AMERICAN SCIENTIST Denny, M. 1995; 83 (2): 166-173

  View details for Web of Science ID A1995QG53900021

• THE EFFECTS OF HYDRODYNAMIC SHEAR-STRESS ON FERTILIZATION AND EARLY DEVELOPMENT OF THE PURPLE SEA-URCHIN STRONGYLOCENTROTUS-PURPURATUS BIOLOGICAL BULLETIN Mead, K. S., Denny, M. W. 1995; 188 (1): 46-56

  Abstract

  Life in the highly turbulent surf zone poses a severe challenge to reproduction in free-spawning animals. Not only can breaking waves quickly dilute the gametes shed by spawning organisms, but turbulence-induced shear stresses may limit fertilization and interfere with normal development. A Couette cell was used to re-create some of the effects of turbulent water motion to study effects of environmentally relevant shear stresses on fertilization in the purple sea urchin (Strongylocentrotus purpuratus). Although low shear stresses improved fertilization success (presumably by increasing mixing), exposure to high shear stresses (of the magnitude found in the surf zone) substantially decreased fertilization success, probably by interfering with contact between egg and sperm. Furthermore, eggs fertilized at high shear stresses often showed abnormal development and low survival of eggs through the blastula stage.

  View details for Web of Science ID A1995QH33900007

  View details for PubMedID 7696387

• EXTREME DRAG FORCES AND THE SURVIVAL OF WIND-SWEPT AND WATER-SWEPT ORGANISMS JOURNAL OF EXPERIMENTAL BIOLOGY Denny, M. W. 1994; 194: 97-115

  View details for Web of Science ID A1994PF20900007

• QUANTIFYING WAVE EXPOSURE - A SIMPLE DEVICE FOR RECORDING MAXIMUM VELOCITY AND RESULTS OF ITS USE AT SEVERAL FIELD SITES JOURNAL OF EXPERIMENTAL MARINE BIOLOGY AND ECOLOGY Bell, E. C., Denny, M. W. 1994; 181 (1): 9-29

  View details for Web of Science ID A1994PE20500002

• MECHANICAL CONSEQUENCES OF SIZE IN WAVE-SWEPT ALGAE ECOLOGICAL MONOGRAPHS Gaylord, B., Blanchette, C. A., Denny, M. W. 1994; 64 (3): 287-313

  View details for Web of Science ID A1994NX85000002

• ELASTOMERIC NETWORK MODELS FOR THE FRAME AND VISCID SILKS FROM THE ORB WEB OF THE SPIDER ARANEUS-DIADEMATUS Workshop on Silk Polymers: Biology, Structure, Properties, Genetics Gosline, J. M., POLLAK, C. C., Guerette, P. A., Cheng, A., Demont, M. E., Denny, M. W. AMER CHEMICAL SOC. 1994: 328–341

  View details for Web of Science ID A1994BZ58L00027

• THE LARGEST, SMALLEST, HIGHEST, LOWEST, LONGEST, AND SHORTEST - EXTREMES IN ECOLOGY ECOLOGY Gaines, S. D., Denny, M. W. 1993; 74 (6): 1677-1692

  View details for Web of Science ID A1993LV24200008

• A DYNAMIC-MODEL FOR WAVE-INDUCED LIGHT FLUCTUATIONS IN A KELP FOREST LIMNOLOGY AND OCEANOGRAPHY Wing, S. R., Leichter, J. J., Denny, M. W. 1993; 38 (2): 396-407

  View details for Web of Science ID A1993LD67500013

• BIOLOGICAL CONSEQUENCES OF TOPOGRAPHY ON WAVE-SWEPT ROCKY SHORES .1. ENHANCEMENT OF EXTERNAL FERTILIZATION BIOLOGICAL BULLETIN Denny, M., Dairiki, J., Distefano, S. 1992; 183 (2): 220-232

  View details for Web of Science ID A1992KC97700004

• INTERTIDAL TREES - CONSEQUENCES OF AGGREGATION ON THE MECHANICAL AND PHOTOSYNTHETIC PROPERTIES OF SEA-PALMS POSTELSIA-PALMAEFORMIS RUPRECHT JOURNAL OF EXPERIMENTAL MARINE BIOLOGY AND ECOLOGY Holbrook, N. M., Denny, M. W., Koehl, M. A. 1991; 146 (1): 39-67

  View details for Web of Science ID A1991FG09500004

• BIOLOGY, NATURAL-SELECTION AND THE PREDICTION OF MAXIMAL WAVE-INDUCED FORCES SOUTH AFRICAN JOURNAL OF MARINE SCIENCE-SUID-AFRIKAANSE TYDSKRIF VIR SEEWETENSKAP Denny, M. W. 1991; 10: 353-363

  View details for Web of Science ID A1991GP22400031

• TERRESTRIAL VERSUS AQUATIC BIOLOGY - THE MEDIUM AND ITS MESSAGE AMERICAN ZOOLOGIST Denny, M. W. 1990; 30 (1): 111-121

  View details for Web of Science ID A1990CQ32500011

• ON THE PREDICTION OF MAXIMAL INTERTIDAL WAVE-FORCES LIMNOLOGY AND OCEANOGRAPHY Denny, M. W., Gaines, S. D. 1990; 35 (1): 1-15

  View details for Web of Science ID A1990DB63600001

• CONSEQUENCES OF SURF-ZONE TURBULENCE FOR SETTLEMENT AND EXTERNAL FERTILIZATION AMERICAN NATURALIST Denny, M. W., SHIBATA, M. F. 1989; 134 (6): 859-889

  View details for Web of Science ID A1989CQ33700003

• A LIMPET SHELL SHAPE THAT REDUCES DRAG - LABORATORY DEMONSTRATION OF A HYDRODYNAMIC MECHANISM AND AN EXPLORATION OF ITS EFFECTIVENESS IN NATURE CANADIAN JOURNAL OF ZOOLOGY-REVUE CANADIENNE DE ZOOLOGIE Denny, M. 1989; 67 (9): 2098-2106

  View details for Web of Science ID A1989AM53200003

• TENACITY-MEDIATED SELECTIVE PREDATION BY OYSTERCATCHERS ON INTERTIDAL LIMPETS AND ITS ROLE IN MAINTAINING HABITAT PARTITIONING BY COLLISELLA-SCABRA AND LOTTIA-DIGITALIS MARINE ECOLOGY PROGRESS SERIES Hahn, T., Denny, M. 1989; 53 (1): 1-10

  View details for Web of Science ID A1989U150400001

• INVERTEBRATE MUCOUS SECRETIONS - FUNCTIONAL ALTERNATIVES TO VERTEBRATE PARADIGMS SYMP ON MUCUS AND RELATED TOPICS Denny, M. W. COMPANY BIOLOGISTS LTD. 1989: 337–366

  Abstract

  Invertebrates use mucus in a far broader spectrum of functions than do vertebrates. Examples include: 1. Navigation. The slime trails of grastropods often contain directional information that is used in homing, mating, and predation. 2. Defense. Many invertebrates coat themselves with slippery, distasteful mucus secretions to ward off predators. 3. Desiccation resistance. Limpets and terrestrial snails use a thin barrier of dry mucus as a mechanism for minimizing desiccation. 4. Structural support. Mucus functions as a tensile structural element in feeding nets and mating ropes. A preliminary analysis of these structures indicates that tensile stiffnesses of 10(4)-10(5) N/m2 may be common. 5. Food. The production of mucus can account for up to 80% of the total energy expenditure of some invertebrates. Mucus is often used as a food source, and in some cases is used to enhance the growth of food items. 6. Locomotion. The adhesive locomotion of gastropods is dependent on the unusual mechanical properties of pedal mucus. These properties may set limits to the size and speed of snails and slugs.

  View details for Web of Science ID A1989BR39N00029

  View details for PubMedID 2701483

• FRACTURE-MECHANICS AND THE SURVIVAL OF WAVE-SWEPT MACROALGAE JOURNAL OF EXPERIMENTAL MARINE BIOLOGY AND ECOLOGY Denny, M., Brown, V., Carrington, E., Kraemer, G., Miller, A. 1989; 127 (3): 211-228

  View details for Web of Science ID A1989AF23700002

• LIFT AS A MECHANISM OF PATCH INITIATION IN MUSSEL BEDS JOURNAL OF EXPERIMENTAL MARINE BIOLOGY AND ECOLOGY Denny, M. W. 1987; 113 (3): 231-245

  View details for Web of Science ID A1987L539600003

• LIFE IN THE MAELSTROM - THE BIOMECHANICS OF WAVE-SWEPT ROCKY SHORES TRENDS IN ECOLOGY & EVOLUTION Denny, M. W. 1987; 2 (3): 61-66

  Abstract

  Nowhere on earth is water motion more violent than in the surf zone of rocky shores, and the hydrodynamic stresses imposed on plants and animals by wave-induced flows far exceed any in terrestrial or oceanic environments. Despite the harshness of the physical environment, wave-swept habitats support persistent, diverse communities. Knowledge of the physical mechanisms by which water motion affects plants and animals and of the ways in which they cope with their environment is essential for understanding the community ecology of these turbulent habitats.

  View details for Web of Science ID A1987G532900005

  View details for PubMedID 21227818

• THE STRUCTURE AND PROPERTIES OF SPIDER SILK ENDEAVOUR Gosline, J. M., Demont, M. E., Denny, M. W. 1986; 10 (1): 37-43

  View details for Web of Science ID A1986A743100008

• WAVE-FORCES ON INTERTIDAL ORGANISMS - A CASE-STUDY LIMNOLOGY AND OCEANOGRAPHY Denny, M. W. 1985; 30 (6): 1171-1187

  View details for Web of Science ID A1985AVJ1000004

• MECHANICAL LIMITS TO SIZE IN WAVE-SWEPT ORGANISMS ECOLOGICAL MONOGRAPHS Denny, M. W., Daniel, T. L., Koehl, M. A. 1985; 55 (1): 69-102

  View details for Web of Science ID A1985ABW5600004

• MECHANICAL-PROPERTIES OF PEDAL MUCUS AND THEIR CONSEQUENCES FOR GASTROPOD STRUCTURE AND PERFORMANCE AMERICAN ZOOLOGIST Denny, M. W. 1984; 24 (1): 23-36

  View details for Web of Science ID A1984SQ04400004

• SPIDER SILK AS RUBBER NATURE Gosline, J. M., Denny, M. W., Demont, M. E. 1984; 309 (5968): 551-552

  View details for Web of Science ID A1984SU57800074

• THE PHYSICAL-PROPERTIES OF THE PEDAL MUCUS OF THE TERRESTRIAL SLUG, ARIOLIMAX-COLUMBIANUS JOURNAL OF EXPERIMENTAL BIOLOGY Denny, M. W., Gosline, J. M. 1980; 88 (OCT): 375-393

  View details for Web of Science ID A1980KV37400026