Statistical evaluation of differences in phytoplankton richness and abundance as constrained by environmental drivers in transitional waters of the Mediterranean basin

Abstract

ABSTRACT1. This paper is focused on the identification of patterns of variation in phytoplankton abundance and taxonomic composition at the eco-regional scale. In addition, these patterns were evaluated with respect to climatic, hydrological and physiographic drivers.2. A hierarchical sampling design was used to integrate seasonal and spatial variations in taxonomic richness, abundance and taxonomic composition of phytoplankton guilds. Data were collected synoptically during two seasons (autumn and spring) in 12 transitional water bodies in Italy, Albania and Greece.3. The number of taxa and the cell density of phytoplankton guilds varied between seasons and across ecosystems. Overall, physiographic and hydrological components accounted for 61% of the variation in the number of taxa, but just 19% of the variation in cell density. 4. At the univariate level, cell density varied significantly with temperature, whereas the number of taxa was found to vary significantly with depth, sinuosity index and outlet structure, lagoon surface area and geographic location.5. The taxonomic composition of phytoplankton guilds varied markedly among lagoons. More than 61% of the 242 taxa identified overall were detected in only one of the lagoons.6. The average similarity of phytoplankton taxonomic structure among ecosystems was 33.15 AE 15.02. Taxonomic similarity varied substantially across both ecosystems and seasons. Overall, more than 70% of variance in taxonomic similarity was explained by physiographic and hydrological forcing factors. Specifically, differences in taxonomic structure were found in transitional ecosystems showing differences in outlet structure, depth and salinity, as well as geographic location. A recurrent pattern of decreasing taxonomic similarity with increasing Euclidean distance was observed for each factor. 7. The results obtained in this study suggest that certain large-scale driving forces can explain eco-regional scale patterns of species richness and taxonomic composition but not of cell abundance, which are probably more affected by local forcing factors.

Phytoplankton Communities in a Coastal Site of Natural Reserve “Lake of Tarsia-Mouth of River Crati”-Northern Ionian Sea, Calabria (Italy)

“…Phytoplankton communities are in fact, the first to suffer the effect and/or to draw any benefits from periods characterized by high presence of nutrients; the high trophy, detected especially in some periods, feeds phytoplankton growth with likely positive effects even for upper trophic rings [22,23]. Moreover, it is necessary to highlight that phytoplankton biodiversity and dynamoics in transitional waters are controlled by different factors, such as flushing rate, residence time, depth, salinity, light and nutrient concentrations; the relevance of each of these factors to the dynamics of phytoplankton guilds is modulated by specific geo-and hydrodynamic properties of each singular transitional system, which determine the differentiation of phytoplankton assemblages [24]. Climatic variations affect phytoplankton directly by eliciting physiological and adaptive responses, and indirectly by inducing hydrological and biological changes, which influence both bottom-up and top-down processes involving phytoplankton variability [25].…”

Long-term phytoplankton dynamics in a Mediterranean eutrophic lagoon (Cabras Lagoon, Italy)

“…It is true that in these two lagoons, phytoplankton is not the main primary producer, but macroalgae component is also very important. In general, it is necessary to highlight that phytoplankton biodiversity and dynamics in transitional waters are controlled by different factors, such as flushing rate, residence time, depth, salinity, light and nutrient concentrations; the relevance of each of these factors to the dynamics of phytoplankton guilds is modulated by specific geo-and hydrodynamic properties of each singular transitional system, which determine the differentiation of phytoplankton assemblages (Vadrucci et al 2008).…”

Biodiversity conservation in Mediterranean and Black Sea lagoons: a trait-oriented approach to benthic invertebrate guilds

“…A hierarchical sampling design (see Vadrucci et al, 2008) was adopted to investigate the seasonal and spatial variation of macroinvertebrate community structure. Data were collected during autumn 2004 and spring 2005, at two sampling points for each habitat type in each ecosystem (TWReferenceNET 'Technical Report on the Biotic Indices of Natural Heritage Safety in Transitional Waters' www.twreferencenet.com/ Products section).…”