Experimental Design:

Experiments were conducted during the CORSACS (Controls On Ross Sea Algal Community Structure) expedition in November 2006 to the Ross Sea, Antarctica, onboard the RVIB Nathaniel B. Palmer (cruise NBP-0608). Water was collected at 76 50' S, 173 47' E using a trace metal clean towed-intake surface water Teflon diaphragm pumping system (Bruland et al., 2005). Sea surface temperature at this location was -1.5 deg C at the time of water collection. Water was prescreened through acid-washed 200 um Nitex mesh to eliminate large zooplankton and collected into a 50-L mixing carboy. Collected water was gently mixed and dispensed into 24 4.5-L acid washed trace metal clean clear polycarbonate bottles for incubation. Four treatments were used with six replicates per treatment. Bottles were incubated in two temperature controlled deck-board incubators housed in deck vans under halogen lights (Feng et al., 2009; Hare et al., 2007). Irradiance was 2000 uE m2 s-1 without screening. Incubators were screened with neutral density filter and measured irradiances in the four treatments were:

Low light, low temperature (LLLT): 61 uE m2 s-1
Low light, high temperature (LLHT): 45 uE m2 s-1
High light, low temperature (HLLT): 321 uE m2 s-1
High light, high temperature (HLHT): 320 uE m2 s-1

One incubator was maintained at 0 deg C, while the temperature in the other was gradually increased to 4 deg C over the course of 24 h. Bottles were incubated for eight days. All sampling occurred under a laminar flow hood using trace metal clean techniques.

References:

Bruland, K.W., E.L. Rue, G.J. Smith, and G.R. DiTullio. 2005. Iron, macronutrients and diatom blooms in the Peru upwelling regime: brown and blue waters of Peru. Marine Chemistry 93: 81-103.

Feng, Y., C.E. Hare, K. Leblanc, G.R. DiTullio, P.A. Lee, S.W. Wilhelm, J. Sun, J.M. Rose, N. Nemcek, I. Benner, and D.A. Hutchins. 2009. The effects of increased pCO2 and temperature on the North Atlantic Spring Bloom: I. The phytoplankton community and biogeochemical response. Marine Ecology Progress Series 388: 13-25.

Hare, C.E., K. Leblanc, G.R. DiTullio, R.M. Kudela, Y. Zhang, P.A. Lee, S.F. Riseman, and D.A. Hutchins. 2007. Consequences of increased temperature and CO2 for phytoplankton community structure in the Bering Sea. Marine Ecology Progress Series 352: 9-16.