Synergistic effects of iron and temperature on Antarctic phytoplankton and microzooplankton assemblages

• Published in: Biogeosciences
• Main Authors: Rose, J. M., Feng, Y., DiTullio, Giacomo R., Dunbar, Robert B., Hare, C. E., Lee, Peter A., Lohan, Maeve C., Long, Matthew C., Smith, Walker O., Sohst, Bettina M., Tozzi, S., Zhang, Y., Hutchins, David A.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Copernicus Publications on behalf of the European Geosciences Union 2009
• Subjects: Antarctic; Ross Sea; Antarc*; Antarctica
• Online Access: https://hdl.handle.net/1912/3127

© 2009 The Authors. This article is distributed under the terms of the Creative Commons Attribution 3.0 License. The definitive version was published in Biogeosciences 6 (2009): 3131-3147, doi:10.5194/bg-6-3131-2009 Iron availability and temperature are important limiting factors for the biota in many areas of the world ocean, and both have been predicted to change in future climate scenarios. However, the impacts of combined changes in these two key factors on microbial trophic dynamics and nutrient cycling are unknown. We examined the relative effects of iron addition (+1 nM) and increased temperature (+4°C) on plankton assemblages of the Ross Sea, Antarctica, a region characterized by annual algal blooms and an active microbial community. Increased iron and temperature individually had consistently significant but relatively minor positive effects on total phytoplankton abundance, phytoplankton and microzooplankton community composition, as well as photosynthetic parameters and nutrient drawdown. Unexpectedly, increased iron had a consistently negative impact on microzooplankton abundance, most likely a secondary response to changes in phytoplankton community composition. When iron and temperature were increased in concert, the resulting interactive effects were greatly magnified. This synergy between iron and temperature increases would not have been predictable by examining the effects of each variable individually. Our results suggest the possibility that if iron availability increases under future climate regimes, the impacts of predicted temperature increases on plankton assemblages in polar regions could be significantly enhanced. Such synergistic and antagonistic interactions between individual climate change variables highlight the importance of multivariate studies for marine global change experiments. This project was supported by US NSF grants ANT 0528715 to JMR, ANT 0741411, ANT 0741428 and OCE 0825319 to DAH, ANT 0338157 to WOS, ANT 0338097 to GRD, and ANT 0338350 to RBD.