I am an experimental biologist whose research interests are directed toward an understanding of the dynamic relations between marine animals and their environment. In particular, my work focuses on the endogenous and exogenous factors that mediate the behavior and physiology of benthic, particle-feeding invertebrates. I take an integrative approach in my research program by studying processes ranging from the organism to ecosystem level. Much of my research focuses on commercially important species, or shellfish (e.g., clams, oysters, mussels, scallops). These animals exert great control over the particle supply and distribution in many coastal ecosystems and can influence the biology and ecology of other organisms. Additionally, they provide vital ecosystem services, and are an important link between the oceans and human health. Because suspension feeders play such a key role in near-shore ecosystems, it is important to understand how they obtain and process food and non-food particles, what factors control feeding processes, and the effects of environmental perturbations on their overall health. For more information about my research laboratory, please visit my web page (see link to the left).

Trophic Interactions Between Benthic Suspension Feeders and Marine Aggregates: This research focuses on the interactions between aggregated material (flocs, marine snow), and benthic, suspension-feeding animals. In the marine environment, transparent exopolymer particles (TEP) are known to enhance flocculation of phytoplankton, detritus, and other particles into aggregates known as marine snow. Marine aggregates increase deposition of carbon to the benthos and serve as a substrate for microbes. Little is known, however, about the sources and fate of TEP. In laboratory and field studies my students and I have been studying the production of TEP by benthic suspension feeders. Field research has been conducted in Bermuda, Long Island Sound (LIS), and New Brunswick (Canada). To date, we have demonstrated that several species of suspension feeders (e.g., bivalves, tunicates) release polysaccharide-rich mucins during normal feeding activities which contribute to the production of TEP in near-shore environments. We are also examining if suspension feeders utilize aggregates or their constituent particles as a food resource. A knowledge of the role of suspension feeders in the production of TEP will lead to a better understanding of inshore food web dynamics.

Linking Marine Pathogens to Molluscan Shellfish: The Ecological Role of Marine Aggregates: In this study we are focusing on the ecological role of marine aggregates as a link between pathogens (e.g., MSX, QPX) and benthic, suspension-feeding bivalves (e.g., oysters, clams). Marine aggregates (e.g., marine snow, flocs), ranging in size from a few micrometers to several millimeters, are ubiquitous in the marine environment. Consequently, benthic organisms, such as bivalves, are exposed to a steady supply of marine aggregates and the various microorganisms contained within. Although many recent studies have focused on the composition, formation, distribution, and fate of marine aggregates none have addressed the role of aggregates in the ecology of marine pathogens. We hypothesize that marine aggregates enhance the transmission of shellfish diseases by at least two mechanisms: 1) as reservoirs when aggregates serve to concentrate marine pathogens within their matrix; and 2) as vectors when aggregates serve as a mechanism by which smaller pathogens (e.g., bacteria, zoospores) are more readily captured by the gills of suspension-feeding bivalves and gain access to their hosts. This research is being conducted in collaboration with scientists at Stony Brook University, New York and the Marine Biological Laboratory, Woods Hole.

Elucidating Particle Selection Mechanisms in Bivalves: Using our previously developed techniques of feeding physiology and biochemistry, we are examining for the first time the bases of selection at the cell and organ level. This work allows us to address long-standing questions regarding the mechanism(s) by which bivalves and other suspension feeders accomplish particle selection. At the core of this research are two fundamental questions:1) Is particle selection an active process, i.e., based on chemically mediated behavior, or a passive process, i.e., based on interactions between particles and mucus-coated feeding structures?; and 2) Do different groups of suspension-feeding molluscs, employ the same or different mechanisms for particle discrimination? Based on our previous studies with these organisms, we have developed several lines of research to investigate the most plausible mechanisms involved in the selection process. Our work focuses on: a) manipulating particle surfaces to determine if selection is a function of surface properties (charge, wettability, protein coated, carbohydrate coated, etc); and b) investigating whether lectins in ctenidial and labial-palp mucus bind to carbohydrate residues of the extracellular matrix of phytoplankton to mediate selection. Results from this research will provide a better understanding of feeding processes in different species of bivalves, the potential impact of bivalves on coastal environments, and how environmental perturbations (e.g., pollution) might affect particle feeding. This study is being conducted in collaboration with Dr. Sandra Shumway, another faculty member in the Department of Marine Sciences, and scientists at Stony Brook University, New York.

Functional Mechanisms of Control in the Bivalve Pump: In this study we are applying two new techniques, our recently developed Pressure-Gape System and Particle Image Velocimetry (PIV), to investigate the physiological bases of water pumping and particle feeding in bivalve molluscs. Experiments are designed to determine relationships between pumping pressure and rate (volume flux), investigate mechanisms by which bivalves alter pumping activity, test the hypothesis that bivalve pumping activity is mediated by exogenous factors, and examine the variation in pumping behavior and performance among several bivalve species. Our research has the potential to resolve some of the long standing controversies regarding the physiological basis of water processing in bivalves, and will provide back-ground data for future studies on the performance of bivalves in the natural environment. This study is being conducted in collaboration with Dr. Sandra Shumway, another faculty member in the Department of Marine Sciences, and scientists at the University of Louisiana.

Li, B., J.E. Ward & B.A. Holohan, 2008. Effect of transparent exopolymer particles (TEP) from marine suspension feeders on particle aggregation. Mar. Ecol. Prog. Ser. 357: 67–77.

Frank, D.M., J.E. Ward, S.E. Shumway, C. Gray & B.A. Holohan, 2008. Application of particle image velocimetry to the study of suspension feeding in marine invertebrates. Marine and Freshwater Behaviour and Physiology. 41: 1-18.

Kach, D.J. & J.E. Ward, 2008. The role of marine aggregates in the ingestion of picoplankton-size particles by suspension-feeding molluscs. Mar. Biol. 153: 797-805.

Lyons, M.M., Y.T. Lau, W.E. Carden, J.E. Ward, S.B. Roberts, R.S. Smolowitz, J. Vallino & B. Allam, 2008. Characteristics of marine aggregates in shallow-water ecosystems: Implications for disease ecology. EcoHealth. 4: 406-420.

Heinonen, K.B., J.E. Ward & B.A. Holohan, 2007. Production of transparent exopolymer particles (TEP) by benthic suspension feeders in coastal systems. J. Exp. Mar. Biol. Ecol. 341: 184-195.

Lyons, M.M., J.E. Ward, R. Smolowitz, K.R. Uhlinger & R.J. Gast, 2005. Lethal marine snow:  Pathogen of bivalve mollusc concealed in marine aggregates. Limnol. & Oceanog. 50: 1983-1988.

Ward, J.E. & S.E. Shumway, 2004. Separating the grain from the chaff: Particle selection in suspension- and deposit-feeding bivalves. J. Exp. Mar. Biol. Ecol. 300: 83-130.

Ward, J.E. , J.S. Levinton & S.E. Shumway, 2003. Influence of diet on pre-ingestive particle processing in bivalves.  I: Transport velocities on the ctenidium. J. Exp. Mar. Biol. Ecol. 293: 129-149.

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