A Stochastic Dynamic Methodology (SDM) to the modelling of trophic interactions, with a focus on estuarine eutrophication scenarios.

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In the face of global change, declines in environmental quality are of increasing concern, especially in shallow coastal areas, densely populated and commonly affected by nutrient enrichment. The warm temperate Mondego estuary (Western Portugal), in commonwithmanyothershallowestuarineareas, isexhibitingincreasedmacroalgalgrowthdue tonutrientenrichment.The increase of macroalgal biomass and possible shift of other primary producers resulting from eutrophication, may have profound effects on estuarine trophic chain. The present paper examined the performance of a holistic Stochastic Dynamic Methodology (SDM) in predicting the tendencies of three representative trophic levels as a response to the increase of nutrient concentrations.Therefore, the proposed methodology has been developed by focusing on the interactions between conceptually isolated key-components, such as primary producers (macroalgae and seagrass), some relevant benthic macroinvertebrates, wading birds and changes in local physicochemical conditions. The dynamic model developed was preceded by a conventional multivariate statistical procedure (stepwise multiple regression analysis) performed to discriminate the significant relationships between prevailing biological and environmental variables. Since this statistical analysis is static, the dataset recorded from the field included true gradients of habitat changes.ThedatausedinthemodelconstructionwassampledbetweenJanuary1993andSeptember1995in threeareasoftheestuary mudflats forbenthicmacroinvertebrates,macroalgae,environmentalandphysicochemical factorsandfromOctober1993toOctober 1994 forwading birds. Themodel validation was based on independent data collected in two different periods, fromJanuary 1996 to January1997andfromFebruary1999toApril2000for all thevariables selected.Overall, thesimulationresults areencouragingsince they seemto demonstrate themodel reliability in capturing the trophic dynamics of the studied estuary by predicting the behavioural pattern for the most part of the components selected under a very complex and variable environmental scenario.
Stochastic dynamic modelling , Ecological integrity , Eutrophication , Mondego estuary , Trophic interactions
Silva-Santos P. et al., 2006