Details

Autor(en) / Beteiligte

• Lever, Mark A.
• Valiela, Ivan

Titel

Response of microphytobenthic biomass to experimental nutrient enrichment and grazer exclusion at different land-derived nitrogen loads

Ist Teil von

• Marine ecology. Progress series (Halstenbek), 2005-06, Vol.294, p.117-129

Ort / Verlag

Oldendorf: Inter-Research

Erscheinungsjahr

2005

Quelle

EZB Electronic Journals Library

Beschreibungen/Notizen

• Effects of eutrophication on the relative importance of nutrients and macroherbivores as controls of microphytobenthic standing crop were examined in estuaries with different nitrogen loading rates: Sage Lot Pond (14 kg ha–1yr–1), Green Pond (178 kg ha–1yr–1), and Childs River (601 kg ha–1yr–1). We selected 5 sites with similar salinity ranges on shallow-water, sandy substrates per estuary. In year-round experiments, we fertilized sediments with nitrogen + phosphorus to examine nutrient limitation. We conducted exclusion experiments to determine the significance of macroherbivores as controls of microphytobenthic biomass and examined possible interactions between nutrients and grazing in cages fertilized with nitrogen + phosphorus. Cages fertilized with nitrogen only were also included to determine if nitrogen availability was limiting. Nitrogen + phosphorus addition increased sediment chlorophylla(chla) content (herein used as a proxy for biomass) by a similar magnitude across estuaries. Grazer exclusion also increased chla, but to a different extent across estuaries: the magnitude of the response increased with increasing nitrogen loading rates. We found no interactions between nutrients and grazing. Strong chlaincreases in response to nitrogen only addition indicated N limitation in Sage Lot Pond and Green Pond. In the highly eutrophic Childs River estuary we found virtually no response to nitrogen-only additions, suggesting the possibility of phosphorus limitation in this estuary.