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Evaluating Connections Between Nitrogen Cycling and the Macrofauna in Native Oyster Beds in a New England Estuary
Citation:
Ayvazian, S., N. Ray, A. Gerber-Williams, S. Grabbert, A. Pimenta, B. Hancock, D. Cobb, C. Strobel, AND R. Fulweiler. Evaluating Connections Between Nitrogen Cycling and the Macrofauna in Native Oyster Beds in a New England Estuary. Estuaries and Coasts. Estuarine Research Federation, Port Republic, MD, 45:196-212, (2022). https://doi.org/10.1007/s12237-021-00954-x
Impact/Purpose:
Recognition of the extent of oyster loss has brought into focus the importance of non-extractive ecosystem services once provided by sustainable oyster reefs and inspired large-scale restoration of this imperiled habitat. Coastal managers aim to use oyster reefs and aquaculture to help restore some of these ecosystems. For example, major efforts are underway to understand how oyster habitats can restore macrofauna habitat and reduce N pollution. Restored oyster reef habitat and enhanced aquaculture practices are widely considered as preferred options to mitigate some of the negative impacts of coastal N loading through stimulation of microbial mediated denitrification, burial of biodeposits, and assimilation of N in soft tissues and shell, followed by subsequent removal during harvest or burial in sediment. Bioextraction from oyster cultivation is considered a best management practice for nutrient mitigation policies in the Chesapeake Bay and on Cape Cod, MA. The aim of this research was to investigate the capacity of a native oyster bed in Green Hill Pond, RI to mitigate nitrogen pollution through denitrification, burial, and nitrogen assimilation in oyster tissue.
Description:
Recent efforts to quantify biogeochemical and ecological processes in oyster habitats have focused on provision of habitat and regulation of the nitrogen cycle. However, it is unclear how these two processes may interact. In this study, seasonal patterns of habitat use and nitrogen removal from natural oyster beds were quantified for comparison with nearby bare sediment in Green Hill Pond, a temperate coastal lagoon in RI, USA. Relationships were tested between benthic macrofaunal abundance and nitrogen removal via denitrification and burial in sediments. Nitrogen removal by oyster bio-assimilation was quantified and compared with nearby oyster aquaculture. Despite limited differences in habitat use by macrofauna, there were fewer non-oyster benthic organisms (e.g., filter-feeders, detritivores) where oysters were present, possibly due to competition for resources. Additionally, low rugosity of the native oyster beds provided little refuge value for prey. There was a shift from net N removal via denitrification in bare sediments to nitrogen fixation beneath oysters, though this change was not statistically significant (t(96) = 1.201; p = 0.233). Sediments contained low concentrations of N; however sediments beneath oysters contained almost twice as much N (0.07%) as bare sediments (0.04%; p < 0.001). There was no difference in tissue N content between wild oysters and those raised in aquaculture nearby, though caged oysters had more tissue per shell mass and length, and therefore removed more N on a shell length basis. These oyster beds lacked the complex structure of three-dimensional oyster reefs which may have diminished their ability to provide habitat for refugia, foraging sites for macrofauna, and conditions known to stimulate denitrification.
URLs/Downloads:
DOI: Evaluating Connections Between Nitrogen Cycling and the Macrofauna in Native Oyster Beds in a New England Estuary
https://link.springer.com/article/10.1007/s12237-021-00954-x