The Plum Island Ecosystems (PIE) LTER is an integrated research, education and outreach program whose goal is to develop a predictive understanding of the long-term response of watershed and estuarine ecosystems at the land-sea interface to changes in climate, land use and sea level. The principal study site is the Plum Island Sound estuary, its coupled Parker, Rowley and Ipswich River watersheds and the adjacent coastal ocean, the Gulf of Maine. Humans are altering the ecosystems of the world at rates not previously experienced. Understanding and predicting how multiple stresses affect the sustainability of ecosystems is one of the most crucial challenges in environmental biology. The PIE LTER focuses on how several aspects of global change influence organic matter and inorganic nutrient biogeochemistry and estuarine food-webs. The inputs of organic matter and nutrients from land, ocean and marshes interact with the external drivers (climate, land use, river discharge, sea level) to dictate the extent and degree of nutrient and organic matter processing and determine the spatial patterns of estuarine productivity and trophic structure. The overarching question is: How will trophic structure and primary and secondary productivity in estuaries be affected by changes in organic matter and nutrient loading and hydrodynamics caused by changing land use, climate and sea level? The project uses a combination of approaches to address research questions and hypotheses: 1) short- and long-term core measurements; 2) short and long-term experiments; 3) comparative ecosystem studies; and 4) modeling. The research integrates estuarine biogeochemistry with studies of food webs and population biology of all trophic levels. The PIE LTER data and information system provides a centralized network of information and data related to the Plum Island Sound Estuarine Ecosystem and its watersheds. This network provides researchers associated with PIE-LTER access to common information and data in addition to centralized long-term storage. Data and information are easily accessible to PIE-LTER scientists, local, regional, state partners and the broader scientific community. Researchers associated with PIE-LTER are committed to the integrity of the information and databases resulting from the research. Broader Impacts: PIE-LTER has developed links with local teachers and students, citizens, conservation organizations, and local, state and federal agencies. What started out as a minimalist program has grown to be a broad, well-rounded suite of activities. The education/outreach program is expected to further expand during this next awqard period, as additional support is obtained from other federal agencies, the Commonwealth of Massachusetts, and private foundations. The long-term goal is to establish a Coastal Outreach office at the PIE-LTER study site that will serve to integrate and promote interactions with interested parties throughout New England. During this grant period, the PIE-LTER will expand its schoolyard program to provide on-going professional development for teachers; support the expansion of this project into nearby urban areas including Salem, Boston, and Revere; and facilitate the transfer of this program to New Hampshire and Maine via the Gulf of Maine Institute. There will be greater involvement with undergraduate and graduate education with the addition of PIs Mather and Pontius from UMass and Clark University, respectively. PIE-LTER has a very active outreach program in which the goal is to communicate research findings to individuals,
Scientific Merit: The Plum Island Ecosystems (PIE) LTER is an integrated research, education and outreach program whose goal is to understand the long-term response of watershed and estuarine ecosystems to changes in climate, sea level and human activities. Some key findings are: 1) Over the last 20 years, climate change has led to a 20% increase in rain and snow falling on watersheds in the PIE region. However, this increase in precipitation has not lead to an increase in water delivery to the coast because over the same period, the amount of water diverted from rivers for human use has increased an equivalent amount. So, on an annual basis, the average amount of water reaching the coast has not changed. However, during summer, when river flow is lowest and human use is highest, water withdrawals have a significant impact on water levels in the river, at times causing the rivers to "run dry". 2) Much of the nitrogen that gets into streams from land sources (lawns, septic, sewage, runoff) may be removed by biological processes that occur within streams. By naturally removing nitrogen from the water, streams help protect estuaries from excess nitrogen. At PIE, we have found that more nitrogen is prevented from reaching the estuary than is the case for most watersheds in the northeastern United States. This may be because most of our nitrogen sources are far from the estuary, unlike many other watersheds. 3) Nitrogen that does reach the estuary may be further removed in sediments and in the marsh through processes that are controlled by a variety of factors. In the upper estuary, sediment removal of N varies most with changes in salinity. In the lower estuary, bivalves influence nitrogen cycling. In the marsh, loss of nitrogen varies with vegetation type, and can be very high in some types of salt marsh vegetation. Nitrogen removal also happens in the root zone of marsh plants, a finding we were able to demonstrate by developing a new method. 4) We have found that yearly variations in sea level have a dramatic impact on how much marsh grass is produced, with production being higher in years when sea level is higher. Using this and other information we developed a model to predict how marshes are responding to sea-level rise. Both the rate of sea-level rise and the availability of sediments in the water column determine what range of sea-level rise rates marshes can tolerate before being lost through submergence. 5) We have found no evidence that herbivory plays a significant role in controlling marsh grass production at PIE, in contrast to findings for some other, more southern marshes. 6) The periodic harvesting of salt marsh hay appears to be sustainable. It has no long-term effect on the abundances of fish, or breeding birds and only minor effects on the food web overall. 7) A great deal of organic material enters the water columns of PIE estuaries from land but we have been able to determine that much of this material simply passes through the estuary without being used by bacteria or higher organisms. In contrast, organic matter derived from the marsh is important in fueling estuarine food webs. 8) Our work has shown the importance of small fish in marsh food webs. Mummichogs, small bait fish, are omnivores that eat small invertebrates but will also consume algae growing on the marsh surface. They switch their diet depending upon food availability. The population of these fish has fluctuated markedly at PIE, and data suggest their abundance changes in response to numbers of a top predator, striped bass. 9) Using radio receivers we have been able to track the movement of striped bass and herring within PIE estuaries, and beyond. This work has helped us understand where these fish feed, whether or not they return to PIE each year, and what their diet and growth rates are in PIE estuaries. 10) Beaver populations have dramatically increased in PIE watersheds, greatly altering stream channels. We found that beaver dams alter both stream chemistry and increase native fish biodiversity. 11) We have applied new methods to map changes in land use at PIE to understand what causes development to occur in specific areas. These results are used to better predict what areas will be targeted for development in the future. Broader Impacts: We have involved well over 1,000 students in grades 5-12 from 10 schools in hands-on activities designed to help them understand their local salt marsh environment. Our marsh equilibrium model (http://jellyfish.geol.sc.edu/model/marsh/mem.asp) has been made available to managers and students and can be used in any marsh system. We have produced a curriculum called "Stripe Bass Science" for teachers and students (www.massaudubon.org/saltmarsh/striper/ ). Data collected on this project is made available on: http://pie-lter.mbl.edu/ .
