Larval Trematode Communities as Indicators of Wetland Ecosystem Health
|Irit Altman||UNH - Department of Biological Sciences|
|April Blakeslee||UNH - Department of Biological Sciences|
|Sarah Fierce||Dartmouth College|
|Deb Zdankiewicz||UNH - Institute for the Study of Earth, Oceans and Space|
|Chelsea Wood||Dartmouth College|
|Erin Dewey||University of New Hampshire|
|Amy Fowler||UNH - Department of Biological Sciences|
|Ben Cilley||UNH - Department of Biological Sciences|
|Lena Collins||UNH - Department of Biological Sciences|
|Thais Fournier||UNH - Department of Biological Sciences|
|Brielle Friedman||UNH - Department of Biological Sciences|
Because of a typically large number of anthropogenic disturbances, efforts to identify the agents of degradation of salt marshes can be costly and difficult. Some of these agents include chemical pollution (e.g., eutrophication, PCBs, hydrocarbons, heavy metals), physical degradation (e.g., erosion; diking; alteration of current, temperature or salinity regime), and modification of biological structure and consequent trophic interactions.
We seek to develop an efficient, holistic method of assessing whether a marsh system is significantly degraded by analyzing the structure of digenetic trematode parasites within the marsh community. Digenetic trematodes are prime candidates to use as indicator species within a marsh because they obligately use several hosts to complete their complex life cycles. Thus, the parasites' presence necessitates the presence of all other host species in the cycle; if any link in the trematode's life cycle is compromised or missing, the parasite declines or is locally extirpated.
We hypothesize that variation in parasite diversity and abundance directly reflects variability in environmental quality and the abundance and density of the parasites' host populations. Because these parasites are trophically transmitted to the final host, these parasites also reveal the extent and strength of predator-prey interactions on a local scale.
In contrast to extensive surveys that approach impact assessment on a species-by-species or a stressor-by-stressor basis, this technique capitalizes on the trematode species' integration of stresses that may be acting on many species (hosts) at variable spatial and temporal scales. This process could drastically improve our detection of marsh degradation, which may be subtle or increase through time, and also eventually save tremendous time, effort and expense compared to traditional techniques to pinpoint environmental impacts within marshes.
The objectives of this task are to determine the effectiveness of trematode parasites as biological indications of marsh degradation. Specifically, we address two main objectives:
1) What are the physical, chemical and biological attributes within salt marshes across a regional scale that influence trematode diversity and abundance in first intermediate host snails?
2) Can the presence (or absence) of individual trematode species in first intermediate host snails predict the presence (or absence) of other host species in the parasites' life cycle?
We will monitor physical (temperature, salinity, currents, pH), chemical (e.g., N, P, lead, mercury), and biological (number of birds, crabs, bivalves, snails and fish, and chlorophyll) variables in at least 20 sites throughout northern New England. At each site we will collect mature snails (Littorina littorea, Ilyanassa obsoleta) to examine for trematode parasite infection. Parasite species richness and prevalence of infection within each snail host population will be analyzed with multivariate analyses to determine which environmental factors are most influential on parasite diversity and prevalence.
We propose a supplemental tool to assess the ecosystem health of estuaries using a single metric--the abundance and diversity of digenetic trematode parasites. By monitoring a suite of trematodes that are obligately dependent on the presence of healthy, viable populations of other marsh species that serve as hosts, we integrate the detection of impacts occurring at a variety of trophic levels within the marsh. Marine resource managers in New England (The Nature Conservancy, NH Estuaries Project, NH Fish and Game, NH Coastal Program and the NOAA NERR System) will benefit from our project.
Success in Meeting Objectives
Available from the National Sea Grant Library (use NHU number to search) or NH Sea Grant
- Blakeslee, A., I. Altman, A. Miller, J. Byers, C. Hamer and G. Ruiz. Parasites and invasions: a biogeographic examination of parasites and hosts in native and introduced ranges. Journal of Biogeography 39(3):609-622, March 2012.
- Altman, I. and J. Byers (2014). Large-scale spatial variation in parasite communities influenced by anthropogenic factors. Ecology 95(7):1876-1887, July 2014.
- Byers, J., A. Blakeslee, E. Linder, A. Cooper and T. Maguire (2008). Controls of spatial variation in the prevalence of trematode parasites infecting a marine snail. Ecology 89(2):439-451, 2008.
- Blakeslee, A. and J. Byers (2008). Using parasites to inform ecological history: comparisons among three congeneric marine snails. Ecology 89(4):1068-1078, 2008.
- Blakeslee, A., J. Byers and M. Lesser (2008). Solving cryptogenic histories using host and parasite molecular genetics: the resolution of "Littorina littorea's" North American origin. Molecular Ecology 17(16):3684-3696, 2008.
- Wood, C. (2006). Effects of the trematode "Cryptocotyle lingua" on the behavioral ecology of "Littorina littorea" in the New England rocky intertidal zone. Undergraduate Honor's Thesis, Dartmouth College.
- Altman, I. (2010). Trematode parasites of the mudsnail "Ilyanassa obsoleta": an analysis of parasite communities at different scales. Doctoral Dissertation, University of New Hampshire.
- Wood, C., J. Byers, K. Cottingham, I. Altman, M. Donahue and A. Blakeslee (2007). Parasites alter community structure. Proceedings of the National Academy of Sciences 104(22):9335-9339, May 29, 2007.