Effects of oil spills on zooplankton communities: insights from laboratory microcosms

Abstract

Oil spills in aquatic environments have been of increasing concern in recent decades. Particularly, the Enbridge Line 5 pipeline that runs under the Mackinac Straits presents the potential for a disastrous oil spill that would affect over 1000 km of coastline. To assess the potential effects of an oil spill on zooplankton communities in the Great Lakes, two sets of microcosms, one for a Michigan inland lake and another for Lake Huron, were manipulated over an exposure period of three days each. The abundance of alive Cladocera was not observed to decrease as oil content in water increased in both microcosms. Hydrocarbon content within biomass was found to be significantly lower in our control group compared to experimental groups. Chlorophyll-a levels did not differ between control and experimental groups for both microcosms. These results suggest that a longer exposure time was needed to view any significant change in abundance of zooplankton and primary productivity. However, the increased hydrocarbons in biomass suggest that zooplankton were intaking oil into bodies and storing it. We believe a more extensive microcosm study of zooplankton communities is merited to further understand the impacts an oil spill would have on them.