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Biodiversity in a changing World

« Oceanic productivity, fishery yields and the net marine sequestration of atmospheric greenhouse gases are all controlled by the structure and function of planktonic communities », as stressed by Karl et al. (2001). Recent studies have documented increases in the magnitude of phytoplankton developments in various parts of the World Ocean in coastal areas as well as in remote oceanic sites. In the coastal ecosystems the increased phytoplankton bloom magnitude of the last decade has been hypothesized to originate from increased upwelling or coastal eutrophication (Kahru & Mitchell, 2008). At the ALOHA site, the famous shift in phytoplankton community structure documented by Karl et al. (2001) was later on explained by a ‘slow motion’ bloom of N2–fixing microorganisms controlled by some processes other than P availability, possibly grazing, viral lysis, the bioavailability of Fe, or increased water column stratification (Karl, 2007). At the BATS site more subtle changes in the relative abundance and variability of the Haptophyte group correlated negatively with the winter North Atlantic Oscillation (NAO) index have been documented by Lomas & Bates (2004) ; they relate these changes to the recent hypothesis that the increased stratification due to global warming could favor the blooming of diatoms over Haptophytes (Tortell et al., 2002). Most of these data have been obtained in the context of Microbial Observatories that were developed with the strong support of the National Science Foundation in the USA. The goal of these observatories is to develop a network of sites in different oceanic areas to study and to understand microbial diversity over time and across environmental gradients.

In the North–western Mediterranean there does not exist any complete data set of simultaneous time–series of bacteria, phytoplankton, and zooplankton. Some changes have however been documented for zooplankton populations in the Ligurian Sea by Molinero et al. (2005) and a recent study of phytoplankton populations in the Gulf of Lion’s also indicated both variations in the microphytoplankton diversity and an interannual evolution parallel to the NAO index trend. Recently, the spatial and temporal scales for the monitoring of bacterioplankton communities were investigated at different stations located at the exit of the Gulf (Ghiglione et al., 2005).

Relevance of biodiversity studies in an observing system .

The areas with altered blooms are likely to be environmentally stressed and undergoing undesirable environmental changes such as a higher frequency of harmful algal blooms and oxygen depletion in bottom layers. These changes can in turn alter pelagic as well as benthic ecosystem dynamics, disrupt traditional fisheries (e.g. jellyfish blooms), and preclude the recreational use of coastal areas (CIESM, 2008). Therefore, there is an important need for the monitoring of bacterial, archaeal and protistan communities in combination with other environmental data to provide not only a comprehensive data set on physical and biogeochemical characteristics but also on processes. The discovery of unexpected microbial taxa and new metabolic processes are changing our current views of many fundamental processes including energy capture pathways and element cycles.

The monitoring of biological community structures of the continuum bacteria–phytoplankton–zooplankton–resources, the latter including benthic and pelagic organisms will give new insights in : 1) the characterization of community dynamics for the definition of functional types to be taken into consideration in complex biogeochemical–ecological–physical coupled models ; 2) the temporal trends of ecosystem structure changes. Finally, in conjunction with WP3 operations and the implementation plan, the WP4 monitoring should help investigating the sensitivity of marine biogeochemical cycles and ecosystems to global change by deciphering the mechanisms regulating the interrelationships between phytoplankton diversity and biogeochemical macronutrient cycles, between bacterial and phytoplankton diversity, between zooplankton and phytoplankton diversity, up to the halieutical resource and whale preservation.

Organizational aspects of biodiversity data acquisition

  • sampling at the three mooring sites (MOLA-Lacaze, Convection zone, Ligurian zone) will be performed monthly for viruses, bacteria, phytoplankton, and zooplankton in addition to the monitoring of benthic communities that should be organized at different time scales. Samples for bacteria, phytoplankton, and microzooplankton will be made at three depths (surface water, deep chlorophyll maximum, bottom water) by using Niskin bottles. A vertical tow net will be performed for mesozooplankton sampling on the entire water column. A vertical phytoplankton tow net will also be performed to look at the entire microplankton community (incl. rare species). The new UVP5 (installed on the CTD-Rosette instrument) will be also useful to estimate “on-line” the zooplankton and large phytoplankton population.

  • analysis for the three stations will be performed by a single operating laboratory per parameter to insure taxonomical coherence of the data sets ; analysis will have to be performed in order to derive or compute biovolumes and biomass for each recorded and enumerated taxon

  • the sampling strategy will be progressively implemented to develop a 2–D picture of the transit between harbor and sampling site by using moving profiler vessel(s) equipped with LOPC (Laser Optical Plankton Counter) and LISST (In Situ Scattering Transmissometer) to get continuous profiles from ~1 μm to ~3 cm particle size classes.

  • 4) development of new and innovative tools derived from molecular techniques, nanotechnologies and omics data will be encouraged in partnership between the different partners