Award: OCE-1238212

Scientific Merit: The Plum Island Ecosystems (PIE) LTER is an integrated research, education and outreach program whose goal is to develop a predictive understanding of the response of a linked watershed-marsh-estuarine system in northeastern Massachusetts to rapid environmental change. Some key findings are: 1) Biological processes occurring in streams and rivers in the watershed remove much of the nitrogen from land sources (lawns, septic, sewage, runoff) and thus prevent nitrogen (N) from reaching the downstream estuary. 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 in upstream portions of the watershed furthest from the estuary, so streams have more opportunity to do their work. In addition, abundant riverine wetlands have the ability to reduce N loading, a role that may be increasing due to expanded beaver ponding since 2000. 2) Nitrogen that does reach the estuary may be further removed in creek and marsh sediments through a biological processes called denitrification that converts nitrate to nitrogen gas. However, our research has shown that a competing nitrate reduction process, dissimilatory nitrate reduction to ammonium (DNRA), that conserves N within the ecosystem is a major nitrogen pathway that cannot be ignored. PIE is not unusual; in a cross-site comparison we found that DNRA accounted for more than 30% of the nitrate reduction at many sites. This has important implications for estuarine production. 3) A better understanding of the role that marshes play in the carbon balance of coastal ecosystems is essential for predicting carbon sequestration in marsh peat and for the ability of marshes to maintain elevation relative to SLR. We measured large variability in net carbon uptake between 2013 and 2016. Years with lower carbon uptake were years when there was a summer drought. This work suggests that variations in summer precipitation have a dramatic impact on annual marsh grass production (carbon uptake), probably through altering soil salinity during a critical growth period. In turn, marsh productivity affects how much carbon is stored in sediments. 4) Warming water temperatures in the Gulf of Maine have allowed for the northward migration of some species. In 2012 we documented the arrival of the warm-water blue crab and in 2014 for the first time we found adult Atlantic marsh fiddler crabs, Uca pugnax, in the marsh. Fiddler crabs have now become well established in PIE marshes. 5) To understand how striped bass, important large mobile predators, are distributed and how their distribution relates to prey abundance we used acoustic tagging techniques to map the whole system distributional patterns of the fish. This allowed us to understand how currents and bathymetry controlled the distribution of the striped bass. We were also able to determine that young striped bass are very dependent on the marsh for their growth. 6) Our work has shown the importance of a small, highly adaptable bait fish in PIE marsh food webs. Mummichogs (Fundulus heteroclitus) , are omnivores that eat small invertebrates but will also consume algae growing on the marsh surface, switching their diet depending upon food availability. However, their fitness improves when their diet is supplemented by protein-rich food items such as insects, which they gain access to during tides that flood the marsh. 7) We have described a change in behavior and appearance in some parasitized amphipods that makes them highly vulnerable to predation. When infected by the flatworm Levinseniella byrdi , the salt-marsh amphipod Orchestia grillis, turns orange and moves "zombie-like" into open areas where it is easy prey for birds, the necessary host for the flatworm. Our work suggests that nutrient enrichment, which is occurring in many marshes, may increase the incidence of parasitization. BROADER IMPACTS: Our award winning K-12 schoolyard program, "Salt Marsh Science", served over 1,000 students per year in grades 5-12 in ten schools. In addition, local high school students served as interns and we had a local teacher studying striped bass. A total of 24 college undergraduate students, funded through the NSF Research Experience for Undergraduates (REU) program, spent the summer in residence. Twenty-one additional undergraduates from all over the country worked or conducted summer research at PIE. Thirty-one Masters and Ph.D. students and 5 post-doctoral fellows conducted their research under the PIE-LTER Program. PIE's contribution to the LTER children?s book series was "Save our Stream", published in 2017. Two children learn how to make lawn care more ecologically sensitive and take action on what they have learned. The science carried out at PIE has influenced environmental policy locally, regionally and nationally, and outreach activities involve nearly every member of the team. PIE scientists serve on numerous advisory committees for federal and state commissions and nonprofit environmental organizations. Data can be found at: http://pie-lter.ecosystems.mbl.edu/ Last Modified: 12/18/2017 Submitted by: Anne E Giblin