Phytoplankton modelling of Lake Erken, Sweden by linking the models PROBE and PROTECH

A phytoplankton community model (PROTECH) and a lake physical model (PROBE) were linked, for the first time, to simulate the phytoplankton community of Lake Erken (Sweden). This allowed the physical effects of ice formation to be incorporated into the calculations of PROTECH. This is the highest latitude lake simulated by PROTECH thus far and was a further test of its biological application to lake ecosystems in general. A new cyanobacteria species was added to the PROTECH model: Gloeotrichia echinulata (Smith) Richter which had functional characteristics never before simulated in PROTECH and was an order of magnitude larger than species previously simulated. The biological outputs of total chlorophyll a were successfully validated against quantitative observations from the lake (EF = 0.76). The addition of G. echinulata to the model notably improved this fit, particularly in the period from July to October. Key taxa biomass were also simulated, with good fits for diatoms (EF = 0.70) and cyanobacteria (EF = 0.83). Furthermore, the characteristic periodic blooms of Gloeotrichia were captured, thus supporting its assigned model parameters and suggesting that PROTECH's growth equations can be applied to this significantly larger species. Furthermore, it appears that Gloeotrichia's simulated seasonal pattern of growth was greatly dependent upon the water temperature.