Biovolume determination of phytoplankton guilds in transitional water ecosystems of Mediterranean Ecoregion

Abstract

1 - Conceptually, morphometric measurements of phytoplankton guilds seem to have major advantages as descriptors of the ecological status of transitional water ecosystems (TW) with respect to classical taxonomic descriptors. However, at present, standardized or common methodologies for the use of morphometric descriptors do not exist. 2 - This paper aims to provide a starting point for the activation of standardized methods for the determination of morphometric descriptors of phytoplankton as a quality element in TW in accordance with the new directive of WFD 2000/60/EU. 3 - Phytoplankton biovolume is one of the most studied morphometric descriptors. It can be estimated by associating the algae with similar geometric forms and determining the volume of these by measuring the linear dimensions required for its calculation under the microscope. However, the lack of a standardized set of geometric forms and equations for calculating biovolume causes difficulties and produces data that are not comparable. 4 - A set of geometric models is suggested here for calculating the cell biovolumes of 201 phytoplankton genera found in transitional water ecosystems of Mediterranean Ecoregion. The equations were designed to minimize the effort of microscopic measurements. The main methodological problems, and the similarities and differences between our own and previously published proposals are discussed.