THE USE OF FOSSIL BENTHIC FORAMINIFERA TO ASSESS HUMAN IMPACTS OVER THE LAST DECADES ALONG SE NORWEGIAN COASTS

The fossil record has a potential to provide usefull data to document changes in past marine environnmental systems. Unlike most macrofaunal groups which are the most commonly used biological quality indicator in present-day marine environments, benthic foraminifera leave a fossil record and therefore allow the reconstruction of human-induced environmental disturbance over decades to centuries. Study of changes in benthic foraminifera assemblages can provide valuable “baseline” data to help identify the extent to which humans have played a role in the change. Foraminifera have the potential to serve as ecosystem characterization tools in modern and past marine environments. We studied the response of benthic foraminifera along a decreasing gradient of oxygen. In August 2008, replicate samples for living (stained) benthic foraminifera from 27 stations in 11 silled fjords along the Norwegian Skagerrak coast were examined. Environmental data (bottom-water dissolved-oxygen, TOC, TN and pigments) were analysed for each station. The ecological quality status (EcoQS) was determined at each sites using living benthic foraminifera. The same kind of data were analysed from 2 recolonisation sites in the inner Oslofjord. In addition, the PaleoEcoQS during the past century was reconstructed using benthic foraminifera and selected environmental parameters from 11 stations in the inner Oslofjord. Results show that living benthic foraminifera are at least as reliable to define present-day EcoQS as conventional methods. Fossil benthic foraminifera can also define ecological status of reference conditions from pre-impacted times. This is not possible using conventional methods. Consequently, benthic foraminifera are excellent bioindicators of human-induced environmental impacts over time.