An integrated open-coastal biogeochemistry, ecosystem and biodiversity observatory of the Eastern Mediterranean. The Cretan Sea component of POSEIDON system

Abstract

Abstract. There is a general scarcity of oceanic observations that concurrently examine air-sea interactions, coastal-open ocean processes, and biogeochemical (BGC) parameters, 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 15 oligotrophic open Cretan Sea's biogeochemistry is considered to be representative of a greater Mediterranean area up to 10 6 km 2 , 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 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-multiparameter approach, supporting BGC data acquisition. 20The current POSEIDON system's status includes open and coastal sea fixed platforms, a Ferrybox (FB) system, and Bio-Argo autonomous floats, that deliver remotely Chlorophyll-a (Chl-a), O 2 , pH and pCO 2 data, as well as BGC-related physical parameters. Since 2010, the list has been further expanded to other BGC (nutrients, vertical particulate matter fluxes), ecosystem and biodiversity (from viruses up to zooplankton) parameters, thanks to the addition of sediment traps, frequent R/V visits for seawater-plankton sampling, and of an ADCP delivering 25 information on macrozooplankton-micronekton vertical migration (in the epi-, 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 centers, technical support infrastructures, calibration laboratory, 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 30 deposition processes and assimilation of satellite Chl-a data. Besides addressing open scientific questions at regional and international level, 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 key role in regional data handling and participating in harmonization and best practices procedures. Future expansion plans 35 consider the evolving scientific and society priorities, balanced with sustainable management.Ocean Sci. Discuss., https://doi.org/10.5194/os-2018-3 Manuscript under review for journal Ocean Sci. Discussion started: 6 February 2018 c Author(s) 2018. CC BY 4.0 License. 1 International need for observatoriesOceans are complex dynamic systems embracing various physical...