Environmental Sciences Research Institute

The impact of phytoplankton growth on the biogeochemical cycling of metals in lakes

The growth of the global economy since the early 20th Century has been mirrored by atmospheric trace metal burden. Consequently, toxic metals such as lead, cadmium and mercury have entered freshwater lakes.


Fig. 2

This has posed a threat to ecosystems and humans as these metals are accumulated by the primary producers (the phytoplankton) and subsequently transferred through the aquatic food chain.

This project has focused on quantifying the short-term changes in the uptake of metals by the phytoplankton in lakes of varying nutrient status. Three remote Scottish lakes (Figure 2) that have received high, medium or low metal contamination from the atmosphere were selected for analysis. It was found that a higher trophic status in the lakes resulted in significant algae dilution of mass specific metals in the phytoplankton and the impact of phytoplankton growth is an important factor in the cycling of lead, cadmium, mercury and chromium in these lakes.

Figure 2. The pristine environment of Loch Coire nan Arr in the north Scottish Highlands (one of the study lakes) where the aquatic life are subject to toxic metal burden.