Hardy Lab
Marine Environmental Physiology
Does intertidal position influence stress resilience in barnacles residing in the rocky intertidal zone?
Life in the intertidal zone can be very challenging for animals that cannot move. Barnacles, mussels, and other non-mobile animals found here spend part of each day submerged in cool, oxygenated, food-rich seawater, and another part of the day in the air where they experience temperature extremes, dehydration, UV radiation and a lack of food. By necessity, life in such a dynamic habitat has led to the evolution of robust biochemical, physiological, morphological and behavioral stress defenses in these organisms. The stress experience of any particular species (or individual) in the intertidal zone, however is dependent on where they are anchored relative to the low tide mark. Animals that are found very high in the intertidal zone - or even in the splash zone above the high tide line - experience much longer period of stressful air exposure than those lower in the intertidal.
We hypothesize that non-mobile organisms found in the higher reaches of the intertidal zone will demonstrate 1) increased survival in the face of environmental stress and 2) increased cellular stress defenses. Further, we expect these differences to exist both within a single species (e.g., Balanus glandula) and across multiple species (e.g., Chthamalus dalli, B. glandula, Tetraclita rubescens and Semibalanus cariosus) that can be found spanning the wide vertical distribution in the rocky intertidal. Understanding how the early stress history of marine organisms influences their stress resilience as an adult has wide-ranging implications for fields including aquaculture, climate-change biology, and conservation biology.
Funded by: CSU-COAST, Santa Rosa Creek Foundation
Applying ecophysiological principles to support local aquaculture
In collaboration with Dr. Kevin Johnson, I apply my expertise in marine invertebrate ecophysiology to address practical challenges facing shellfish aquaculture and restoration along the California coast. Our research integrates controlled laboratory experiments with field-based studies to evaluate how environmental stressors—including elevated temperatures, hypoxia, and changes in salinity—affect shellfish survival, growth, metabolism, immune function, and cellular stress responses. By combining physiological assays, biochemical indicators of stress, and quantitative assessments of stress tolerance, we aim to identify conditions and practices that improve shellfish resilience, aquaculture productivity, and restoration success. Our collaborative projects focus on four areas: (1) expanding cultivation of native Pacific littleneck clams as a sustainable alternative to nonnative Manila clams; (2) supporting restoration of native Olympia oysters by investigating local adaptation and physiological differences among populations; (3) evaluating the feasibility of introducing Eastern oysters into West Coast aquaculture to diversify production and reduce vulnerability to environmental stress and disease; and (4) improving Pacific oyster aquaculture success by identifying differences in growth, survival, and stress resilience among commercially important oyster lineages. Together, these projects translate fundamental physiological research into actionable information for local shellfish growers, hatcheries, and restoration practitioners.
Funded by: CA SeaGrant, Nature Conservancy, Santa Rosa Creek Foundation, CSU - COAST
Diffusion Effects on Skeletal Muscle Energetics & Design
We use both experimental and modeling approaches to examine how intracellular diffusive transport processes influence cellular energetics and structural organization in skeletal muscle. The issue of diffuse flux is largely ignored within the fields of biochemistry and cellular energetics, as diffusion rates inside of a cell are generally assumed to be rapid relative to enzyme reaction rates, but this isn’t always the case. Portunid swimming crabs, for example, are known for their unusually large skeletal muscle fibers (<600 μm in diameter), as well as their excellent aerobic swimming ability. Whereas typical adult mammalian skeletal muscle fibers are approximately 10-50 μm in diameter, blue crab (Callinectes sapidus) fibers are only small (<60 μm) in the juveniles and grow hypertrophically to exceed 600 μm in diameter in the adults. In the giant acorn barnacle (balanus nubilus) skeletal muscle fiber diamters of greater than 1mm (1000 μm)have been observed! At these sizes, excessive intracellular diffusion distances and low surface area to volume ratios should prohibit aerobic metabolism (and ultimately locomotor behavior). For this reason, the blue crab represents an excellent model organism for studying the role of diffusion in regulating metabolic rates.
This project can be broadly divided into four main research objectives: 1) assess the extent to which diffusion may control aerobic metabolism during extreme fiber growth in blue crab skeletal muscle, 2) investigate the intracellular organization of blue crab muscle fibers during growth to determine whether diffusion constraints play a role in shaping the evolution of skeletal muscle fiber design, 3) determine whether the cellular level responses to diffusion constraints are universally observed in all cells, and 4) explore the effect of limited environmental oxygen (e.g., hypoxic zones, intertidal emersion of sessile organisms) on crustacean skeletal muscle energetics and structure (namely in barnacles). Ultimately we have determined that aerobic metabolism in the giant skeletal muscle fibers of the adult blue crab is not limited by diffusion, however, it is on the brink of being severely diffusion limited. Using a reaction-diffusion mathematical model we resolved that these animals are able to maintain normal muscle function during extreme growth by dramatically altering their fiber’s structural organization as they get larger (i.e., changing the distribution of organelles or the pattern of intra-fiber perfusion). Furthermore, the same cellular level responses to diffusion constraints have been observed in the homologous muscle group from eight different species of Brachyuran crab, indicating that the influence of diffusion on fiber design may be universal.