As one of the three workshops at IMBER IMBIZO III conference, workshop 2 was convened by three SCOR WG 134 members ( Nianzhi Jiao, Farooq Azam and Carol Robinson), together with Helmuth Thomas from Canada. Also, SCOR WG134 member David Kirchman and Ramaiah Nagappa attended the workshop as one of the session chairs and the local organizers, respectively.
The IMBIZO III conference was hosted by National Institute of Oceanography in Goa, India during 28-31 January, 2013. It comprised three interdisciplinary workshops held in parallel. In order to provide the environment conducive for scientists to interact and discuss, each workshop was limited to approximately 40 participants. Workshop 2 has attracted scientists from multiple disciplines including microbial ecology, biogeochemistry, organic chemistry, climate science, fisheries and marine economy, to exchange ideas and devise strategies to integrate the Microbial Carbon Pump(MCP) mechanism into the concepts and models of carbon sequestration in the ocean’s and the global carbon cycle.
During the day 1 (28 January, 2013)IMBIZO joint session, Dr. Farooq Azam gave a Workshop 2 Keynote presentation: Microbial carbon pump and ecosystem connectivity. The science highlights in this presentation focused mainly on the opportunity exploring the linkages and interaction between MCP and Biological Pump (BP). A few important statements were addressed, including the profound and critical role of microbial regulation on organic matter processing (both dissolved phase/MCP and particulate phase/BP) but coupling is highly variable; bacterial molecular interactions connect MCP & BP by structuring biogeochemical state as interaction matrix (“connectome” & “interactome”); comparable in magnitude to BP; and bacterial DOC in the MCP is comparable in magnitude to BP et al.Finally, Dr. Azam wrapped up the talk by proposing that“give me ahigh bacterial growth efficiency (BGE) and I will give you the next ice age”, and we should LOOK AT the thing in order to study molecular interaction in the complex system, which means multiple microscopic based images should be included as a fundamental studying methodology.
Keynote presentation by Dr. Azam at the plenary session
Workshop 2 included three scientific sessions and one synthesis session. It was beginning with an introduction of the overview and objectives by conveners: processing of DOC, interactions between MCP and BP, perturbations and links to humanity and large scale C cycling. There were plenary sessions for collecting and integrating ideas following the discussion of three separated workshops.
During session 1, the nature of DOC, microbial processing of DOC and genetic diversity were discussed. How can the diversity change help to explain the MCP mechanism in the ocean?Dr. David Kirchmangave the answers by explaining three topics: different roles of different bacteria in the DOM processing, new roles in the carbon cycling, and the link between diversity and biogeochemistry. Session 2 was focused on the interaction between MCP and BP and their responses to anthropogenic perturbation. Dr. Louis Legendre presented the potential effects of ocean warming on the biological and microbial carbon pumps. Particularly, a short video of MCP and its application from Dr. Nianzhi Jiao’s group was showed during the plenary session and attracted much interest. The following photos displayed Dr. Jiao addressing the importance of reducing the use of chemical fertilization on the land which could lead to an enhancement of the MCP as a carbon sink in eutrophic coastal waters.
A short vedio about MCP.
Dr Jiao at the plenary session
Dr. Jiao introduced that enriched nutrients enhance heterotrophic microbial metabolisms and influence the carbon transformation in the euphotic zone, microbial carbon pump may have profound effect on the carbon sequestration, but excess nutrients may reduce the marine carbon sequestration. Meanwhile, the results of microbiological and photochemical transformation of organic carbon during an in situ iron and phosphate addition experiment conducted by Dr. Carol Robinsonindicated that the important role of both microbial and biological carbon pump to organic carbon under changing nutrient conditions. The keynote of session 3 was about the large temporal and spatial scale dynamics & links to humanity, during which the global alliance of continuous plankton recorder surveys (GACS) was introduced by Dr. Peter Burkill.
One of the key questions we’re trying to answer is how carbon transforms through MCP and BP as well as the interaction of two. The following aspects should be stressed: anthropogenic perturbation, land and atmospheric nutrients uploading, higher trophic levels, and natural scenarios from estuary to deep ocean, upwelling & eddy as well. The future work should focus on the mechanism, quantity, rate and proportion of MCP. With the combination of multiple efforts from genes to ecosystems, from observation to modeling, we should also study the impact of anthropogenic influence on the ocean system.
Outcomes of summary reports and a template for workshop synthesis paper were achieved during the day-4 last synthesis session. The processes and sources of DOC and their relative roles were already covered in recent reviews. We know that two pumps (BP&MCP) are tightly coupled and have physical connectivity, so we should view them as system but not boxes. The reason of organic matter being refractory is either because enzyme missing/not efficient enough to use, or molecular/processes too diverse, patchiness too dilute. We need alternative hypotheses to test.
Therefore, research highlights should focus on processes and mechanisms govern (the efficiency of) microbial processing of DOC and their timescales; definition of important environmental controls (climate, weather, ocean circulation…); model and observation investigating the “change effect” et al. Particularly, Louis Legendre gave a talk and poster which helped us understand how the two carbon pumps act and interact to sequester atmospheric CO2 into the deep oceans. Potential anthropogenic perturbations were also discussed during the session, followed by a consequential hypothesis that change in C flux of BCP and MCP due to anthropogenic change are irrelevant when consider next 100 years.
Finally, in order to build linkage between our natural and social science. We want to make our message society relevant: why open ocean so important – elevator statement to Barack Obama– microbes why important– sustainability of Planet Earth– and ultimately to consolidate the food security/fisheries and alleviate poverty through climate mediation (carbon sequestration). We also want to persuade policy makers to look to open ocean in order to better define areas, to make international law of the sea and thus translate to better stewardship of fundamental ecological services.
A special issue in Biogeosciences was proposed to bring together articles arising from discussions of workshop 2. Topics to be investigated include the organisms and microbial processes which produce and transform dissolved organic carbon in the ocean, organisms and processes which influence the interaction between the BP and the MCP, and the impact of anthropogenic perturbations such as nutrient addition and ocean acidification on oceanic carbon transformation, export and sequestration. Manuscripts review will be available online in July 2013.
Workshop 2 discussion
(Editing Contact：xjz@xmu.edu.cn)