European Journal of Phycology
We examined the combined effects of light and pCO2 on growth, CO2-fixation and N2-fixation rates by strains of the unicellular marine N2-fixing cyanobacterium Crocosphaera watsonii with small (WH0401) and large (WH0402) cells that were isolated from the western tropical Atlantic Ocean. In low-pCO2-acclimated cultures (190ppm) of WH0401, growth, CO2-fixation and N2-fixation rates were significantly lower than those in cultures acclimated to higher (present-day approximate to 385ppm, or future approximate to 750ppm) pCO2 treatments. Growth rates were not significantly different, however, in low-pCO2-acclimated cultures of WH0402 in comparison with higher pCO2 treatments. Unlike previous reports for C. watsonii (strain WH8501), N2-fixation rates did not increase further in cultures of WH0401 or WH0402 when acclimated to 750ppm relative to those maintained at present-day pCO2. Both light and pCO2 had a significant negative effect on gross : net N2-fixation rates in WH0402 and trends were similar in WH0401, implying that retention of fixed N was enhanced under elevated light and pCO2. These data, along with previously reported results, suggest that C. watsonii may have wide-ranging, strain-specific responses to changing light and pCO2, emphasizing the need for examining the effects of global change on a range of isolates within this biogeochemically important genus. In general, however, our data suggest that cellular N retention and CO2-fixation rates of C. watsonii may be positively affected by elevated light and pCO2 within the next 100 years, potentially increasing trophic transfer efficiency of C and N and thereby facilitating uptake of atmospheric carbon by the marine biota.
Original Publication Citation
Garcia, N. S., Fu, F. X., Breene, C. L., Yu, E. K., Bernhardt, P. W., Mulholland, M. R., & Hutchins, D. A. (2013). Combined effects of CO2 and light on large and small isolates of the unicellular N2-fixing cyanobacterium Crocosphaera watsonii from the western tropical Atlantic Ocean. European Journal of Phycology, 48(1), 128-139. doi:10.1080/09670262.2013.773383
Garcia, Nathan S.; Fu, Fei-Xue; Breene, Cynthia L.; Yu, Elizabeth K.; Bernhardt, Peter W.; Mulholland, Margaret R.; and Hutchins, David A., "Combined Effects of CO2 and Light on Large and Small Isolates of the Unicellular N2-Fixing Cyanobacterium Crocosphaera watsonii From the Western Tropical Atlantic Ocean" (2013). OES Faculty Publications. 290.