Effects of Mercury on a Globally Threatened Salt Marsh Specialist: Indicator of Salt Marsh Ecosystem Health
Recently, my colleagues, Drs. Kimberly Babbitt (UNH, Natural Resources) and David Evers (BRI, Gorham, ME), and I submitted a research proposal, "Effects of mercury on a globally threatened salt marsh specialist: indicator of salt marsh ecosystem health," in response to the 2008-2009 New Hampshire Sea Grant RFP. Although our proposal was not selected to receive Sea Grant funding, several reviewers recognized the importance of our research questions and the Technical Advisory Panel encouraged us to conduct additional, preliminary studies before pursuing our full research objectives, as initially proposed. To this end, I am writing now to request NH Sea Grant Development Funds to conduct preliminary studies that will be used to generate a more competitive full Sea Grant proposal in the near future.
Our original proposal was to investigate the impacts of mercury contamination on the saltmarsh sharp-tailed sparrow, a salt marsh ecosystem obligate and a species of conservation concern. Our objective was to use a combination of ecological, genetic and toxicological data to examine the relationship of blood mercury levels and population size, nesting success and inter-marsh dispersal of the saltmarsh sparrow, to evaluate its role as an indicator of salt marsh ecosystem health. By examining the link between mercury levels and bird demographics, we aimed to determine the impacts of mercury contamination on saltmarsh sharp-tailed sparrow population dynamics and whether populations subject to high mercury contamination are suffering declines. The rationale for our research is that mercury contamination is a significant threat to salt marshes because of its toxicity to humans and wildlife, its persistence in ecosystems and capacity to bio-accumulate. Our colleagues at BRI have documented alarmingly high blood levels of mercury in sharp-tailed saltmarsh sparrows in some New England marshes (>3.0 ppm, well exceeding the lowest observed adverse affects level, LOAEL, of 1.18 ppm used for songbird blood). Recently, the saltmarsh sharp-tailed sparrow has been recommended as a bioindicator for estuarine systems in northeastern North America.
The over-arching objectives for our research remain the same; however, we recognize the need for conducting preliminary studies to establish potential causative links prior to embarking on the large-scale research effort. To this end, we intend to focus our efforts in the upcoming year on obtaining genetic and demographic data on dispersal and population productivity. If awarded NH Sea Grant Development Funds, we will use them to support the collection and analysis of genetic and demographic data from 4 salt marsh complexes in New Hampshire: Hampton Beach Marsh (Hampton), Chapman's Landing Marsh (Stratham), Fairhill Marsh (Rye), and Squamscott River Marsh (Newfields) in the summer of 2008. We will assess population size (via point counts) and nesting success (via nest surveys) to provide measures of local bird use and productivity of individual marshes. Because only determination of the fate of fledged birds can reveal whether local production yields effective dispersers (source population) or not (sink), we will assess source-sink dynamics by measuring gene flow among marshes. To this end, we will use mist netting to capture a target sample of 50 saltmarsh sparrows from each site. Blood samples (30-50 µl) will be drawn from the cutaneous ulnar vein and subject to microsatellite DNA analysis to determine population genetic structure and inter-pond dispersal. These data will enable us to characterize marshes by their population productivity and to identify marshes that are acting as sources and sinks. We will then be in a position to compare these data with mercury data that will be collected concurrently by our colleagues at BRI (funded by other sources). If, as we expect, we find a link between mercury and saltmarsh sparrow population dynamics, we will have the preliminary data necessary to initiate a large-scale effort to tease apart the effects of mercury on saltmarsh sparrow population viability. As we currently lack data on local or regional inter-marsh movements of saltmarsh sparrows, preliminary data on dispersal and genetic structure collected via support from Sea Grant will be critical for identifying the appropriate scale at which to aim further studies (i.e., how fine a scale of sampling is necessary to accurately assess saltmarsh sparrow population structure?).
Through our partners and collaborators at the USFWS, we have received additional funding for similar research on salt marshes in four National Wildlife Refuges. This research was initiated in the summer of 2007, and 266 genetic samples were collected from sites within Rachel Carson National Wildlife Refuge (NWR: sites in both Wells and Scarborough, ME), Parker River NWR (Parker River, MA), John H Chafee NWR (Rhode Island) and Wertheim NWR (Shirley, Long Island). Large complexes of salt marsh habitat were sampled to allow analysis of dispersal within marshes in addition to among marshes. Point counts and nest surveys were conducted at three of these sites (at both sites in Rachel Carson NWR and in Parker River NWR), and additional demographic data will be conducted from these and additional NWRs in 2008. The lack of genetic samples and population demographic data from New Hampshire marshes is an obvious gap in this sampling regime that Sea Grant Development Funds would enable us to fill.
We hope that you will agree that this is an important area of research (recently, our collaborator, Dave Evers, has been holding press conferences and events with Maine senators about the significance of his mercury toxicology research) and that UNH involvement is worthwhile. We foresee that the awarding of Sea Grant Development Funds to this effort will prove productive. The research we propose herein constitutes a solid stand-alone project, and as such will provide critical information on saltmarsh sparrow population dynamics in New Hampshire. Our results will have additional value, however, when combined with the work we are doing with our partners at the USFWS and with the mercury work of our colleagues at BRI. Through these collaborative efforts, we will begin to be able to evaluate the role of the saltmarsh sharp-tailed sparrow as an indicator of salt marsh ecosystem health. Therefore, the preliminary data that we will collect with the help of these development funds will certainly strengthen our ability to get future NH Sea Grant and other external funding. Thank you for consideration of our project for Sea Grant Development Funds.