The demise of the alga Botryococcus braunii from a Norwegian fjord was due to early eutrophication

In the sedimentary record of the permanently anoxic Drammensfjord, a suite of lipid biomarkers that are derived from the alga Botryococcus braunii ( Kutzing), botryococcenes, is present in varying amounts, but absent in sediments deposited after AD 1850. The disappearance is concurrent with the industrialization of sawmills and the introduction of paper and pulp mills along the river Drammen and upstream water bodies, and the related increase of anthropogenic eutrophication. Because of the sensitivity of this alga for environmental change, a direct correlation between these two events is inferred. This implies that the disappearance of the botryococcenes can serve as a palaeoenvironmental indicator for early eutrophication or environmental change in general. This may be a useful tool in the ongoing research to unravel the response of natural systems to climatic, geophysical or anthropogenic changes.