Abstract
Atmospheric CO2 is projected to double by 2100, resulting in increased temperatures, ocean acidification (OA) and changes in the balance of marine ecosystems. While chemical effects of OA are well understood, the biological effects are less certain. Predictions include a shift in plankton communities towards smaller organisms, reduced carbon (C) export rates, and increased roles of gelatinous zooplankton in C cycling. Using a whole ecosystem approach we will test hypotheses that (H1) CO2 induced acidification, with warming, will result in a shift of autotrophic plankton communities favoring smaller flagellate species rather than large diatoms and (H2) acidification and warming will favor gelatinous plankton resulting in increased transfer of autotrophic production to the microbial loop. To address these hypotheses, we propose to conduct experiments using a multi-factorial design (CO2, temperature, presence/absence of gelatinous plankton). We will quantify and characterize autotrophic, heterotrophic, and bacterial plankton communities, growth and development rates of a model gelatinous plankter (Oikopleura dioica) and dominant copepod species, DOM production, fate, and turnover rates, as well as net microbial community respiration rates. By examining in detail the 'microbial black box', this proposal will generate data with clear implications for international biogeochemical initiatives which seek to provide understanding of global change and consequent effects on human society. Determining how gelatinous plankton alter C flows in a high CO2 world is also important in managing commercial fisheries as yields are controlled by C bioavailability to higher trophic levels and C transfer efficiency through planktonic food webs. Combining multidisciplinary international science and state of the art research facilities and approaches, provides a unique template for transformative research on impacts of OA on biologically mediated elemental flux through our changing oceans.
Norway