A spatially explicit ecosystem model of seston depletion in dense mussel culture

Type Article
Date 2008-09
Language English
Author(s) Grant J1, Bacher CedricORCID2, Cranford P3, Guyondet T4, Carreau M5
Affiliation(s) 1 : Dalhousie Univ, Dept Oceanog, Halifax, NS B3H 4J1, Canada.
2 : Inst Francais Rech Exploitat Mer, F-29280 Plouzane, France.
3 : Bedford Inst Oceanog, Ecosyst Res Div, Dept Fisheries & Oceans, Dartmouth, NS B2Y 4A2, Canada.
4 : UQAR, ISMER, Rimouski, PQ G5L 3A1, Canada.
5 : Hatch Ltd, Synexus Global BU, Montreal, PQ H3B 2G2, Canada.
Source Journal of Marine Systems (0924-7963) (Elsevier), 2008-09 , Vol. 73 , N. 1-2 , P. 155-168
DOI 10.1016/j.jmarsys.2007.10.007
WOS© Times Cited 61
Keyword(s) Towed sensors, Nutrient dynamics, Circulation model, Phytoplankton, Carrying capacity, Shellfish aquaculture, Estuaries, Ecosystem model
Abstract A fully-coupled biological-physical-chemical model of a coastal ecosystem was constructed to examine the impact of suspended mussel culture on phytoplankton biomass in Tracadie Bay, Prince Edward Island, Canada. Due to the extent of mussel culture there, we hypothesised that shellfish filtration would control the concentration and distribution of phytoplankton and other suspended particles in the bay. Circulation was delineated with a tidally-driven 2D numerical model and used to drive an ecosystem model with a focus on pelagic components including phytoplankton production, nutrients, detritus, and mussels. The benthos were treated as a sink. Nutrients and seston were forced by tidal exchange and river input, with phytoplankton additionally forced by light. Boundary conditions of seston and nutrients were derived from field studies with an emphasis on the contrast between spring (high river nutrients, low temperature) and summer (low river inputs and high temperatures). Model output was used to map phytoplankton carbon over the bay for each season and in the presence of mussels and river nutrient input. Results indicate severe depletion effects of mussel culture on overall phytoplankton biomass, but no spatial pattern that can be attributed to grazing alone. Primary production generated by nutrient-rich river water created a mid-bay spike in phytoplankton that dominated the spatial pattern of chlorophyll-based carbon. Model results were validated with surveys from a towed sensor array (Acrobat) that confirmed the river influence and indicated bay-wide depletion of 29% between high and low water. Our model results indicate that the farm-scale depletion emphasised in previous studies cannot simply be extrapolated to seston limitation at the ecosystem level. (C) 2007 Elsevier B.V. All rights reserved.
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