Article

Modelling the impacts of semi-intensive aquaculture on the foodweb functioning of a Nile Delta coastal lake

Published in: African Journal of Marine Science
Volume 39, issue 3, 2017 , pages: 237–249
DOI: 10.2989/1814232X.2017.1362354
Author(s): M BocciDepartment of Environmental Sciences, Informatics and Statistics, Italy, R PastresDepartment of Environmental Sciences, Informatics and Statistics, Italy, S KholeifNational Institute of Oceanography and Fisheries (NIOF), Egypt, D Dalla BarbaDepartment of Environmental Sciences, Informatics and Statistics, Italy, D BrigolinDepartment of Environmental Sciences, Informatics and Statistics, Italy

Abstract

Nutrient loadings are an important component of aquaculture impacts as they can lead to cascade effects at the ecosystem level. An evaluation of these effects on foodweb functioning is presented and discussed for the case study of Lake Burullus in the Nile Delta, Egypt, where semi-intensive aquaculture in earthen ponds has grown remarkably in recent decades. Estimations of nutrient loads into the lake's brackish water, from agriculture and fish ponds, were assessed. A biogeochemical model was set up and calibrated to simulate the loads from nitrogen, phosphorus and phytoplankton, with and without fish ponds. The biogeochemical model was coupled offline to a foodweb model to test the effects of additional nutrient loads from aquaculture on the lake's foodweb functioning. The results obtained by comparing the present conditions of aquaculture development with a no-aquaculture scenario allowed us to identify a set of indicators of foodweb functioning which are sensitive to changes in nutrient loads from aquaculture. The limited changes in phytoplankton concentration with respect to changes in nutrient loads suggested that primary production in Lake Burullus is presently controlled largely by factors other than nutrient influxes from aquaculture. This study emphasises the potential benefits of using a combination of biogeochemical and foodweb models to assess the cumulative effects of nutrient loading from aquaculture on a receiving water body.

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