Carrington Lab Research Interests

My research program, in its broadest sense, investigates the physiological ecology of marine organisms. I am fascinated by the form and function of organisms inhabiting physically demanding environments, where thermal, osmotic, and hydrodynamic conditions can be extreme. I generally focus on organisms common to wave-swept rocky shores, where they are alternately exposed to marine and terrestrial conditions with the rise and fall of the tides. For example, sturdy mussels, mobile snails, and flexible seaweeds can experience cool water flowing over 10 m/s (>20 knots) in the morning, followed by an afternoon high and dry in the baking summer sun. How do these kinds of environmental fluctuations affect the growth, survival, and reproduction of organisms with such different body plans?

My research involves both plants and animals and spans many levels of biological organization, from the mechanics of biological materials, to the persistence of populations, to the characterization of the physical environment and how it influences biological processes. I often take an engineering approach to the study of living systems, applying the basic mechanical principles to evaluate the organismal form and function. My laboratory is located at the University of Washington’s Friday Harbor Laboratories and comprises a broad range of biomechanical research tools, including several recirculating flumes, materials testing devices, force transducers, flow meters, temperature probes, and a wind tunnel.

In recent years, there have been four major themes to my research, all of which involve collaboration with my students and other researchers: 1) ecomechanics of wave-swept mussels, 2) mechanical design of mussel byssus, 3) thermal effects on ecological processes, and 4) functional morphology of seaweeds. Although these themes may appear disparate, I view them as being entirely complementary; they all explore how organisms perform within the physical constraints of their environment. A more detailed description of each research theme follows.

Ecomechanics of wave-swept mussels. This has been a major focus of my laboratory in recent years, funded by the National Science Foundation. We use mussels as a model system to investigate how organisms inhabiting rocky shores respond to changes in wave climate that occur seasonally and interannually. This research draws upon the disciplines of oceanography, marine ecology, biomechanics, and biology. We have shown that mussel attachment strength varies seasonally, perhaps due to energetic constraints, and consequently mussels are prone to large mortality events during specific windows of time (September - October for mussels in Rhode Island), rather than an entire storm season (Carrington et al. 2009; Carrington 2002). These findings underscore the importance of evaluating environmental conditions in the context of physiological tolerances that may vary spatially and temporally. Investigations with graduate student Gretchen Moeser, explored the causes of variable mussel attachment and refocused our studies to environmental (water temperature, chemistry, food supply) and physiological (reproductive cycle) influences on thread quality (Moeser and Carrington 2006, Moeser et al. 2006). We continue this work at FHL, drawing upon comparisons to other local mussel species and also in collaboration with colleagues in Canada, Spain, and South Africa (e.g. Carrington et al. 2008, Lachance et al. 2008).

Mechanical design of mussel byssus. I initiated this line of research in the early 1990's, when I was a postdoctoral fellow in Dr. John Gosline’s biomaterials laboratory at the University of British Columbia. I quantified the unique mechanical properties of the fibers (byssal threads) that tether mussels to hard substrate; byssal threads are extremely stretchy and tough in comparison to other biological materials (Bell & Gosline 1996, 1997; Gosline et al. 2002). Along with two of my graduate students, I continued these studies using more advance techniques, comparing threads produced by different species, and examining how thread mechanics varies with environmental conditions (Carrington & Gosline 2004, Brazee & Carrington 2006, Moeser & Carrington 2006). The latter study established a fascinating link between byssus material integrity and ecological performance, as discussed in the previous section. The next step is to address why byssal material properties vary seasonally, and I am working with collaborators in Canada and Spain to explore the role of intrinsic (mussel physiological condition) and extrinsic (water conditions, food supply). Although my research on mussel byssus was initially motivated by a desire to understand how mussels evolved flexible tethers to survive on wave-swept shores, my investigations have also captured the attention of bioengineers interested in the design of novel high performing materials, such as artificial tendons that are strong and durable. Mussel byssus has become an important model system in the emerging field of bio-inspired design (Holton-Anderson et al. 2007, Carrington 2008, Waite 2008) and my comparative work has been important in identifying which species make the best candidates for further study by biochemists and material scientists. I continue these investigations at FHL, working with mussel byssus as well as other biomaterials produced by local plants and animals.

Thermal effects on ecological processes. This new NSF-funded project (with Dr. Sarah Gilman, Claremont Colleges) focuses on how temperature affects three key interacting species: the predatory whelk (snail) Nucella ostrina, its preferred prey species, the acorn barnacle Balanus glandula, and the rockweed Fucus distichus, which may alter the thermal and/or flow environment encountered by the two animal species. This simple rocky shore community provides an ideal model system to study the mechanisms by which temperature influences multiple, hierarchical ecological processes. For example, it is well known that temperature influences organismal physiology, behavior, and species interactions, but rarely are all three studied concurrently. Our research is centered around three major goals: to develop biophysical models to predict organismal body temperatures from local climatic conditions, to develop energetic models to link body temperature to individual performance, and to determine the effect of temperature on the interactions among the three species. Altogether, this represents the first study to integrate biophysical, physiological, and ecological techniques into a comprehensive model to evaluate the multiple roles of temperature in determining species distribution and abundance. As such, it represents as significant contribution to understanding basic ecological questions, such as the role of temperature in structuring communities, and will also contribute to a more mechanistic understanding of the ecological consequences of future climate changes, such as global warming (Helmuth et al. 2005). One important output of this project is a continuous record of local weather conditions, which we record at our research site at FHL and publish online for public access .

Functional morphology of seaweeds This has been a long-standing research interest of mine, beginning with an exploration the consequences of variable morphology of the intertidal alga Mastocarpus papillatus as a graduate student (Carrington 1990). Marine algae of temperate rocky shores, especially in Washington waters, are fascinating because they are so diverse in the way they are constructed. How can so many different, and seemingly delicate, growth forms thrive on a shore pounded by surf? Many of my earlier contributions focus on how thallus morphology influences the ability of algae to withstand wave forces, while others detail the mechanical properties (strength, stiffness, etc.) of various species. More recently, I have published a number of papers on the biomechanics of Chondrus crispus, a red alga that is commercially harvested in the North Atlantic for the extraction of carrageenan (an emulsifier commonly added to dairy products such as Ben & Jerry’s ice cream). The studies by Michael Boller use a combination of field, laboratory and modeling techniques to illustrate how tissue construction (plant stiffness, thickness, and size) influences the ability of a plant to deform and reconfigure in flow, which in turn influences the flow forces it encounters (Boller and Carrington 2006a, 2006b, 2007). This work extends our basic understanding of how flexible objects, which are less commonly studied by engineers, interact with and modulate water moving past them.