Time-Series Stations  
    Future ocean carbon studies, whether OCTET, EDOCC or some combination of the two should consider conducting process studies in the context of established time series stations. Our present ocean time-series stations, BATS and HOTS, have proven to be a tremendous resource to assess seasonal and annual variability in carbon cycle processes; to conduct focused process studies; and, to test various types of biogeochemical models. Given this background of data and understanding, it is surprising that we did not conduct JGOFS-type process studies at the HOTS and BATS sites with all of the detailed measurements of trophic processes, nutrient cycling and flux measurements that were done at the JGOFS process study sites. Detailed process studies imbedded within time-series studies allow one to assess the physical, chemical and biological conditions of the study site before and after the process measurements and thus provide an essential framework for interpreting rate measurements in the context of seasonal, annual and decadal changes.
    Future carbon studies in both the open ocean and on coastal margins should establish time-series stations with comparative approaches in different ecosystems. Long-term studies are essential to understand the changes that are occurring in the ocean carbon cycle. While previous expeditionary processes studies have resulted in many new insights into important biogeochemical processes, these “snapshots” do not allow us to confidently extrapolate rate measurements that vary as the scalar properties of the ecosystem change. An integral component of future process studies should be the establishment of time-series stations that provide an essential context of variability of the system. 

Mesopelagic Studies 
    JGOFS processes studies were concentrated primarily in the euphotic zone. Through these studies we have greatly increased our understanding of the food-web processes that recycle carbon within, or export carbon from the euphotic zone. Thorium and sediment trap studies have estimated the gravitational flux at different depths in the water column, however we have little notion of the mechanisms responsible for the utilization and transformation of carbon below the euphotic zone. JGOFS process studies in the Arabian Sea and Equatorial Pacific have shown that roughly 90% of the carbon fixed by autotrophs is recycled within the water column with approximately 10% exported as the gravitational flux at the base of the euphotic zone. Sediment traps at 1000 m have shown that approximately 90% of this gravitational flux from the euphotic zone is recycled between 100 and 1000 m. Thus the percentage of the carbon that is recycled (90%) is roughly the same in the euphotic zone and in the 100 to 1000 m depth horizon. Is this recycling distributed homogeneously between 100 and 1000 m? How do the bacteria, protozoa, mesozooplankton and fish determine the rates of carbon utilization, transformation and export in the mesopelagic zone? We might guess that there are particular depths horizons that are “hot spots” for recycling, regeneration and the utilization and repackaging of sinking particles. If one compares the “average” particle concentration (POC) from bottle casts to the carbon requirements for the resident mesopelagic mesozooplankton, the zooplankton should all starve to death. Clearly this is not the case, implying that sinking particles may be concentrated at particular density interfaces where the mesozooplankton could not only meet their nutritional needs but also repackage sinking material into faster sinking fecal pellets. In the case of meso- and macrozooplankton , there are similar species and genera worldwide in the mesopelagic depths. Thus there are particular species that could be important in the interception and utilization of sinking carbon particles.

Feb 15 2000