People

Bio

POST-DOCTORAL FELLOW

National Estuarine Research Reserve

Wells, ME, 04090

RESEARCH INTERESTS

My research interests include the following areas: Interaction between climate change, marine invasions and their impact on communities, specifically related to native diversity and species richness; biogeographic patterns of marine invasions, physiological response of marine invasions to climate change (e.g., salinity, temperature and pH); evolutionary, conservation and historical ecology questions; biogenic attributes of habitats and species richness, abundance; species-specific effects of habitat engineers on species richness, abundance and relative contribution to ecosystem function; climate change effects on bioaccumulation of heavy metals.

BACKGROUND AND CURRENT EMPLOYMENT

I am currently employed at the National Estuarine Research Reserve in Wells, ME as a post-doctoral fellow working with Michele Dionne. At the reserve, I am using ecads (floating seaweeds) to study ecological questions relating to equivalence of ecosystem engineers to salt marsh ecosystem function.

Seaweeds can be easily dislodged by surging water and ice rafting, dispersing as morphologically distinct ecad species to other locations. Since they do not have holdfasts, ecads are only held in place by means of entangling around or underneath seaweeds (intertidal rocky shores) or rooted vegetation (salt marshes). When ecads are deposited in marsh ecosystems, they grow entangled among the roots of Spartina alterniflora. Thereby, adding structure to the under story of these relatively simple habitats created by marsh grass.

I also examine climate change effects on bioaccumulation of heavy metals. Climate change and its effect on mercury transfer in aquatic systems is still unknown. In estuarine and marine organisms, the cycling of mercury involves different chemical forms and is commonly found as mercury ion (Hg²⁺) or methylmercury (MeHg). Generally it is MeHg that is of public concern as it is a potent toxin that bioaccumulates and concentrates at all trophic levels in the food web, placing at risk people who consume predatory fish. It is of special concern for both women and children as there are strong correlations between total Hg in fish and delays in neurobehavioral development in children. Human exposures to Hg and MeHg are largely through the consumption of predatory fish species e.g., tuna and swordfish that obtain their mercury burdens from prey that reside in productive coastal and estuarine waters. Much of the research on the transfer of mercury in aquatic food webs has centered on freshwater systems. Only recently have studies focused on Hg and MeHg transfer in food webs in estuaries. This work is collaborative effort between Celia Chen (Dartmouth College), Michele Dionne and David Evans (NOAA).

Prior to my appointment at Wells NERR, I completed my PhD in September 2007 at the University of New Hampshire with Larry G. Harris (advisor). My dissertation work explored the interaction between climate change, introduced species (colonial sea-squirts) and community development. I replicated an earlier study (Harris and Irons 1982) that documented the development of a marine fouling community and I used historical climate data from the study site to infer climate related changes in non-native species, species composition and species turnover. I also coupled this work with physiological studies to mechanistically examine the relationship between climate and species distribution and abundance. Some of this work has been published in the Journal of Experimental Marine Biology and Ecology, Marine Ecology Progress Series, Marine Biology and are in review.

I completed my B.A. at the University of New Brunswick in Canada and my masters at the University of Bremen in Germany through the Alfred-Wegner Institute for Polar and Marine Research. My master's research focused on the impacts of iceberg scouring on succession of megafaunal communities in the Weddell Sea, Antarctica.

SELECTED PUBLICATIONS

Dijkstra J.A., L.G. Harris, C. Brooks, W.J. Lambert (in review) Invasive species alter food web structure in marine rocky subtidal habitats. Marine Ecology Progress Series.

Dijkstra J.A. and L.G. Harris (2009) Maintenance of diversity altered by a shift in dominant species: Implications for species coexistence. Marine Ecology Progress Series. 387: 71-80.

Westerman E.L., R.B. Whitlatch, J.A. Dijkstra, L.G. Harris (2009) Variation in brooding period masks similarities in response to changing temperatures. Marine Ecology Progress Series. 391: 13-19.

Valentine P. C., M. R. Carman, J. Dijkstra, D. Blackwood (2009). Larval recruitment of the colonial ascidian Didemnum vexillum, seasonal water temperatures in New England coastal and offshore waters, and implications for spread of the species. Aquatic Invasions.

Westerman E.G., J.A. Dijkstra, L.G. Harris (2009). High natural fusion rates in a Botryllid ascidian. Marine Biology. 156: 2613-2619.

Dijkstra J., *A. Dutton, E. Westerman and L. G. Harris. (2008) Heart Rate reflects osmostic stress levels in two introduced colonial ascidians Botryllus schlosseri and Botrylloides violaceus. Marine Biology. Vol. 154 (5): 805-811.

Dijkstra, J., *H. Sherman, L. Harris. (2007) The role of colonial ascidians in altering biodiversity in marine fouling communities. Journal of Experimental Marine Biology and Ecology. 342: 168-171.

Dijkstra J., L. Harris and E. Westerman. (2007) The long-term distribution and ecology of four invasive colonial ascidians in the Gulf of Maine. Journal of Experimental Marine Biology and Ecology. 342: 61-68.

Bullard, S. G., G. Lambert, M. R. Carman, J. Byrnes, R. Whitlatch, G. Ruiz, R. Miller, L. Harris, P. Valentine, J. Collie, J. Pederson, D. McNaught, A. Cohen, R. Asch, J. Dijkstra, K. Heinonen. (2007) Distribution and ecology of Didemnum sp. Journal of Experimental Marine Biology and Ecology. 342. 99-108.

Grizzle R.E.,  L. G. Ward, R. Langan, G. M. Schnaittacher, J. A. Dijkstra, J.R. Adams. (2003) Environmental monitoring at an open ocean aquaculture site in the Gulf of Maine: Results for 1997-2000. In CJ. Bridger and BA Costa-Pierce (eds). Open ocean aquaculture: From research to commercial reality. The World Aquaculture Society, Baton Rouge, Louisiana, United States.

Teaching Experience

Instructor: Introduction to Marine Biology. University of New Hampshire. 2007 to present

Faculty advisor: Research Internships in Field Science. Shoals Marine Laboratory (Cornell University and University of New Hampshire). 2008 and 2009.

Co-instructor in Ecology. University of New Hampshire. Topic: Population ecology. 2008

Faculty advisor: Research Experience for Undergraduates (NSF sponsored program). Shoals Marine Laboratory (Cornell University and University of New Hampshire). 2007

Teaching assistant. University of New Hampshire. 2001-2007

Ecology and Evolution of Marine Invertebrates

Mammology

Human Anatomy and Physiology