4.6 Article

Catchment modifications influence the composition of basal organic matter supporting suspension-feeding bivalves

Journal

ESTUARINE COASTAL AND SHELF SCIENCE
Volume 275, Issue -, Pages -

Publisher

ACADEMIC PRESS LTD- ELSEVIER SCIENCE LTD
DOI: 10.1016/j.ecss.2022.107989

Keywords

Land -sea connectivity; Bivalves; Kelp forest; Trophic position; Multiple stressors; Food web; Ecosystem -based management

Funding

  1. University of Otago doctoral scholarships

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Marine primary production is sensitive to environmental stressors from land-based and maritime anthropogenic activities. This study found significant differences in the composition of basal organic matter supporting bivalve species among sites and regions, highlighting the strong linkages between land use and the composition of organic matter sources. The findings also revealed the impact of salmon farming on the trophic dynamics of shellfish in the coastal zone.
Marine primary production is sensitive to multiple environmental stressors from land-based and maritime anthropogenic activities. Stressors may alter the distribution, abundance and composition of primary producers and thereby directly influence the fluxes of organic matter into marine food webs. To investigate these effects, we measured the relative contributions of basal organic matter derived from macroalgae and phytoplankton to five suspension-feeding bivalve species (Pecten novaezelandiae, Atrina zelandica, Tucetona laticostata, Perna canaliculus and Mytilus galloprovincialis) along a gradient in catchment modification and marine farming activity in the Marlborough Sounds, Tasman Bay and Fiordland, on the South Island of New Zealand. Stable isotope analyses (delta 15N and delta 13C) were conducted on samples of basal organic matter and muscle tissue of bivalves collected from multiple sites within each region during 2018 and 2019. Mass balance mixing models revealed significant differences in the composition of basal organic matter supporting individual bivalve species among sites and regions. The proportion of macroalgal-derived organic matter supporting the subtidal bivalve community was negatively associated with the area of modified land use in the surrounding catchments. These results support strong linkages between land use in catchments and the composition of basal organic matter sources supporting bivalve communities. Values of delta 15N among four of the bivalve species were consistently higher at sites associated with salmon farming, indicating inputs of allochthonous nitrogen from the farms. These findings highlight the intimate connection between anthropogenic stressors and the trophic dynamics of shellfish in the coastal zone.

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