An assessment of the functional variability of selected coastal ecosystems in the context of local environmental changes

Abstract

The functioning of coastal ecosystems is greatly dependent on a wide variety of external pulses (e.g. tides, freshwater influx, seasonal trends in temperature, nutrient input, etc.). Assessments of the effect of a selection of environmental characteristics driven by natural and/or anthropogenic forces on ecosystem function are given using selected ecosystem properties, such as total system throughput, system organization, productivity, recycling, and trophic efficiency, derived from ecological network analysis (ENA) of several coastal ecosystems on monthly, intra-seasonal, seasonal, and interdecadal scales. Each ecosystem was modelled depicting data of standing stocks, the flows between the constituent living and non-living components in the system, exports, and imports. Results from ENA revealed considerable differences of the same property (or properties) resulting from physical changes (e.g. temperature, salinity, oxygen, rate of freshwater inflow) over time. A small temperature increase in a Florida seagrass bed, for example, resulted in increases in system throughput, the P/B ratio, and in the rate of carbon recycling, but also in a significant decrease in system organization. The effect of seasonal increases in water temperature and of measured decrease/increase in river run-off to a few selected estuaries is discussed using ENA. © 2009 International Council for the Exploration of the Sea. Published by Oxford Journals. All rights reserved.