Changes in species diversity among echinoderms in the sill area of Gullmarsfjorden : Effects on changes in species composition among echinoderms - ecosystem functions and possible changes

Increasing attention has been given marine benthic macrofauna due to its importance in marine ecosystems and for its value as bioindicator of environmental changes. One of the most abundant groups among benthic macrofauna are echinoderms which often hold keystone positions in the ecosystems and have proven to be good bioindicators. The aim of this study was to inventory echinoderms and analyze whether species diversity has change over time in Gullmarsfjorden, a fjord with limited water exchange and hence highly sensitive to environmental fluctuations. Also, what may have caused any changes and what potential effects can it have on ecosystems in the fjord, and which species may be valuable as bioindicators. The results show that species diversity of echinoderms has decreased significantly since the early 1900s and the main reduction have occured among species living on/in soft or sandy bottoms. Many of the lost echinoderms species are essential bioturbators and thus important to marine ecosystems. However, Echinocyamus pennatifidum, a sea urchin which is a valuable bioturbator may have established in the fjord during the last century judging from this study. Species like Asterias rubens and Psammechinus miliaris, which are common in the fjord, have also proved to be valuable bioindicators for abiotic changes such as increased CO2-levels and pollution of heavy metals and PCB