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Volume 14, issue 5 | Copyright

Special issue: Coastal marine infrastructure in support of monitoring, science,...

Ocean Sci., 14, 1223-1245, 2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Review article 12 Oct 2018

Review article | 12 Oct 2018

An integrated open-coastal biogeochemistry, ecosystem and biodiversity observatory of the eastern Mediterranean – the Cretan Sea component of the POSEIDON system

George Petihakis1, Leonidas Perivoliotis1, Gerasimos Korres1, Dionysios Ballas1, Constantin Frangoulis1, Paris Pagonis1, Manolis Ntoumas1, Manos Pettas1, Antonis Chalkiopoulos1, Maria Sotiropoulou1, Margarita Bekiari1, Alkiviadis Kalampokis1, Michalis Ravdas1, Evi Bourma1, Sylvia Christodoulaki1, Anna Zacharioudaki1, Dimitris Kassis1, Emmanuel Potiris1,a, George Triantafyllou1, Kostas Tsiaras1, Evangelia Krasakopoulou1,a, Spyros Velanas1, and Nikos Zisis1 George Petihakis et al.
  • 1Institute of Oceanography, Hellenic Centre for Marine Research (HCMR), 72100 Heraklion, Greece
  • apresent address: Department of Marine Sciences, School of the Environment, University of the Aegean, 81132 Mytilene, Greece

Abstract. There is a general scarcity of oceanic observations that concurrently examine air–sea interactions, coastal–open-ocean processes and physical–biogeochemical processes, in appropriate spatiotemporal scales and under continuous, long-term data acquisition schemes. In the Mediterranean Sea, the resulting knowledge gaps and observing challenges increase due to its oligotrophic character, especially in the eastern part of the basin. The oligotrophic open Cretan Sea's biogeochemistry is considered to be representative of a greater Mediterranean area up to 106km2, and understanding its features may be useful on even larger oceanic scales, since the Mediterranean Sea has been considered a miniature model of the global ocean. The spatiotemporal coverage of biogeochemical (BGC) observations in the Cretan Sea has progressively increased over the last decades, especially since the creation of the POSEIDON observing system, which has adopted a multiplatform, multivariable approach, supporting BGC data acquisition. The current POSEIDON system's status includes open and coastal sea fixed platforms, a Ferrybox (FB) system and Bio-Argo autonomous floats that remotely deliver fluorescence as a proxy of chlorophyll-a (Chl-a), O2, pH and pCO2 data, as well as BGC-related physical variables. Since 2010, the list has been further expanded to other BGC (nutrients, vertical particulate matter fluxes), ecosystem and biodiversity (from viruses up to zooplankton) variables, thanks to the addition of sediment traps, frequent research vessel (R/V) visits for seawater–plankton sampling and an acoustic Doppler current profiler (ADCP) delivering information on macrozooplankton–micronekton vertical migration (in the epipelagic to mesopelagic layer). Gliders and drifters are the new (currently under integration to the existing system) platforms, supporting BGC monitoring. Land-based facilities, such as data centres, technical support infrastructure, calibration laboratory and mesocosms, support and give added value to the observatory. The data gathered from these platforms are used to improve the quality of the BGC-ecosystem model predictions, which have recently incorporated atmospheric nutrient deposition processes and assimilation of satellite Chl-a data. Besides addressing open scientific questions at regional and international levels, examples of which are presented, the observatory provides user-oriented services to marine policy makers and the society, and is a technological test bed for new and/or cost-efficient BGC sensor technology and marine equipment. It is part of European and international observing programs, playing a key role in regional data handling and participating in harmonization and best practices procedures. Future expansion plans consider the evolving scientific and society priorities, balanced with sustainable management.

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Short summary
Integrated oceanic observations on multiple processes including biogeochemistry are scarce. In the eastern Mediterranean (Cretan Sea) the spatiotemporal coverage of such observations has increased with the expansion of the POSEIDON observatory. The observatory addresses scientific questions, provides services to policy makers and society, and serves as a technological test bed. It plays a key role in European and international observing programs, in harmonization procedures and data handling.
Integrated oceanic observations on multiple processes including biogeochemistry are scarce. In...