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

In this paper I present a short review on laboratory test methods using mai nly macroalgae and the basis for how to monitor phytobenthic communities al ong salinity gradients. The presentation focuses on problems related to var ying 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 th e factors, which can interfere with the reliable use of e.g, macrophytes as monitors of metal pollution. The influence of the physical and chemical pr operties 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. Abiot ic factors, e.g. salinity, pH in the water and organic content in the sedim ent 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 pollut ion hot spots are situated at the coast and the concentration will decrease from the outlet towards the open sea. The pollution gradient interacts wit h 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 plan ts and animals along the estuary as well as when the sites for monitoring a re selected.