The impact of climate change on aquatic systems and phytoplankton communities : A quantitative study of the impacts of altering food-quality on microzooplankton growth rate

Abstract: A global increase in atmospheric CO2 and temperature is assumed to affect the marine ecosystems in numerous ways, e.g. by altering ocean circulation patterns and changing nutrient regimes. The changes are expected to impact heavily on both phytoplankton communities as well as the rest of the marine food-web. Based on previous experimental studies that have investigated the impacts of varied algae food-quality on zooplankton, this quantitative study hypothesizes that (i) the tested microzooplankton species Brachionus plicatilis (rotifer) and Euplotes sp. (ciliate) will show high population growth rates (g) when fed with Nannochloropsis sp. grown under nutrient replete conditions, (ii) that the species will show a population growth rate close to zero when fed with algae grown on phosphorous-deficient media and (iii) that microzooplankton will be negatively affected by the algae grown in nitrogen-deficient media. The study thus aims to investigate how changes in the balance of energy and several chemical elements in ecological interactions, ecological stoichiometry, affect the growth rates of algal grazers. The results show that food-independent factors had a large impact on growth rates and resulted in unexpected, deviating trends. However, as the growth rates for B. plicatilis fed with phosphorous-deficient algae were lower than those of B. plicatilis fed with nitrogen-deficient algae, there is some support for the