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Marine Ecology Progress Series

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MEPS 463:127-139 (2012)  -  DOI: https://doi.org/10.3354/meps09809

Benthic grazing impact: coupling and uncoupling in relation to physical forcing

Jens Kjerulf Petersen1,*, Marie Maar2, Flemming Møhlenberg3, Jens E. N. Larsen4

1Dansk Skaldyrcenter, Øroddevej 80, 7900 Nykøbing Mors, Denmark
2Department of Bioscience, Aarhus University, PO Box 358, Frederiksborgvej 399, 4000 Roskilde, Denmark
3DHI Water Environment Health, Agern Allé 5, 2920 Hørsholm, Denmark
4Marine Biological Section, Department of Biology, Copenhagen University, Strandpromenaden 5, 3000 Helsingør, Denmark

ABSTRACT: In the shallow micro-tidal cove Kertinge Nor, Denmark, a series of field campaigns were conducted from April 1995 to September 1996. During these campaigns, the effect of benthic grazing on phytoplankton concentrations was studied using a dual approach. In the first approach, the density, size distribution and in situ growth of 3 dominant benthic grazers were determined to assess grazing potential and its realisation. In the second approach, the realised grazing potential was estimated from the decline in area-specific chlorophyll a (chl a) concentrations after breakdown of stratification. Forcing functions were monitored continuously during the field campaigns using meteorological data, current meters, temperature loggers and CTD point measurements. In addition, measurements from a local monitoring program in Kertinge Nor were included in the data analysis. Stratification of the water column in the cove was mainly governed by wind speed and solar radiation and occurred 50 to 75% of the time. The potential grazing pressure of the benthic suspension feeders varied but was always greater than that required to graze the entire volume of the cove per day. Using both approaches, it was estimated that realised grazing was ~50% of the potential. The lack of realisation of the grazing potential could be attributed to a lack of mixing of the water column, which resulted in strong vertical gradients in concentrations of chl a. The primary mode of decoupling between benthic suspension feeders and phytoplankton was the stratification of the water column, which created refuges for the phytoplankton.


KEY WORDS: Suspension feeding · Stratification · Ciona intestinalis · Mya arenaria · Mytilus edulis · Wind driven exchange


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Cite this article as: Petersen JK, Maar M, Møhlenberg F, Larsen JEN (2012) Benthic grazing impact: coupling and uncoupling in relation to physical forcing. Mar Ecol Prog Ser 463:127-139. https://doi.org/10.3354/meps09809

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