Pelagic habitats in the Mediterranean Sea: A review of Good Environmental Status (GES) determination for plankton components and identification of gaps and priority needs to improve coherence for the MSFD implementation

Varkitzi, France, Basset, Cozzoli, Stanca, Zervoudaki, Giannakourou, Assimakopoulou, Venetsanopoulou, Mozetič, Tinkara Tinta, Skejic, Vidjak, Cadiou, Pagou

At present there is no consistent approach for the definition of Good Environmental Status (GES) and targets in
the Mediterranean Sea, especially for Biodiversity Descriptors, according to the Article 12 of the Marine Strategy
Framework Directive (MSFD). The use of plankton indicators in the Mediterranean Sea refers mostly to pelagic
habitats in coastal waters and to case studies connected with environmental pressures, e.g. in the Adriatic,
Aegean etc. The aim of this review is to study the existing biodiversity indicators for different plankton groups in
order to compare GES definitions for the Biodiversity Descriptor and identify the relevant gaps and priority
needs to improve coherence for the MSFD implementation across the Mediterranean. For these purposes, we
focus on plankton indicators for phytoplankton, zooplankton and prokaryotes. Regional conventions (OSPAR,
HELCOM, Barcelona and Bucharest Conventions) have long considered phytoplankton as a key element for
integrated assessment systems. Phytoplankton biomass, community composition, abundance, frequency and
intensity of blooms are used for such assessment purposes. Chlorophyll a still remains the most widely used
indicator mostly thanks to its time saving, cost-effective and reproducible analytical methods that provide easily
comparable datasets. Despite some integrated indices proposed for phytoplankton in the literature at the
Mediterranean level, a number of constrains still prevent their wide use. Regarding zooplankton communities,
commonly used indicators have a taxonomic base while recently size structure and biomass can provide a valuable
index of zooplankton population dynamics and ecosystem production. Jellyfish blooms’ occurrence and
frequency are also considered important zooplankton indicators in specific areas, e.g. North Adriatic. Concerning
the prokaryotes, so far MSFD takes into account only their pathogenic component. The revision of MSFD GES
definitions shows that all Mediterranean MSs have defined GES at the Descriptor level (e.g. D1 Biodiversity), but
our comparison of approaches shows a low level of coherence in GES related to pelagic habitats and plankton
communities. Gaps mostly focus on the lack of thresholds and baselines for many biodiversity indicators, and on
the scarcity of common and consistent methodological approaches for biodiversity assessment by the MSs.
Suggestions to fill these gaps and inconsistencies among MSs include: integration of EU legislation and Regional
Agreements and Conventions; targeting on priority species and habitats; testing of existing biodiversity indices
with good performances in case studies; coordination and intercalibration actions for the establishment of
threshold values and baselines; determination of common methodologies; undertaking of regular monitoring
programs and impact assessment studies at regional and sub-regional levels.

Functional and Evolutionary Ecology
External organisation(s)
National Institute of Biology, Hellenic Centre for Marine Research, Università del Salento, Institute of Oceanography and Fisheries, Institut français de recherche pour l'exploitation de la mer (IFREMER)
Ecological Indicators
No. of pages
Publication date
Peer reviewed
Austrian Fields of Science 2012
106021 Marine biology
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