Monitoring eutrophication and pollution in estuarine environments - Focusing on the use of benthic communities

Abstract

In this paper I present a short review on laboratory test methods using mainly macroalgae and the basis for how to monitor phytobenthic communities along salinity gradients. The presentation focuses on problems related to varying salinity combined with pollution outlets. After briefly describing the rationale for using key species and/or changes in species composition in monitoring programs, I will highlight some of the factors, which can interfere with the reliable use of e.g. macrophytes as monitors of metal pollution. The influence of the physical and chemical properties of the different types of aquatic ecosystems, e.g. lakes, rivers, estuaries, have to be taken into consideration when assessing the impact of toxic agents on living organisms and the function of the ecosystems. Abiotic factors, e.g. salinity, pH in the water and organic content in the sediment may all have an impact on the form in which the compounds are found in the water and thus the bioavailability to the organisms. Most of the pollution hot spots are situated at the coast and the concentration will decrease from the outlet towards the open sea. The pollution gradient interacts with the salinity, and among other things the amount of organic content in the water. This has to be taken into account when measuring the impact on plants and animals along the estuary as well as when the sites for monitoring are selected.