Experiment with the diatom Chaetoceros sp. on the impact of temperature, light climate, and carbonate chemistry on TEP production and aggregation processes from May 2015 (OA - Effects of High CO2 project)

<p>In this experiment, we used five-liter rolling tanks to address the question of whether elevated pCO2, temperature, and light climate simulating a future climate scenario will increase the aggregation potential for a phytoplankton clone representing the diatom genus, Chaetoceros. Bloom development, TEP production, and aggregation were monitored over an eight-day period to observe how simulated future ocean conditions may influence bloom dynamics for this species compared to the species’ optimal growth condition.</p>

<p>A freshly isolated species of the phytoplankter genus Chaetoceros (10-50um cell length) was used was isolated in June of 2014 in the Eastern Pacific CCS (38.700N 123.671W). In culture, Chaetoceros sp. grew in f/2 media, over a temperature gradient of 12-25 ºC and light climate ranging from 70-400 µmol m-2s-1.</p>

<p>Two experimental treatments were used to assess the impacts of increased light, temperature, and pCO2 stress on the processes of DIC uptake, TEP production, and aggregation. For each treatment, 12 gas-tight polycarbonate rolling tanks were exposed to a single combination of light climate, temperature, and pCO2 representing either optimal or future conditions. Rolling tanks were constructed and maintained to establish solid body rotation. Target temperature (13 °C) and light intensity (100 µmol m-2s-1) for the optimal treatment were determined in the pre-experimental phase with the addition of present-day levels of pCO2 (400 ppm). In the treatment representing predicted increases in stratification, warming, and elevated pCO2, target future conditions were 18 ºC, 200 µmol m-2s-1, and 800 ppm.</p>