Ecological, morphological and molecular characterization of Kryptoperidinium sp. (Dinophyceae) from two Mediterranean coastal shallow lagoons.

In this study, the field ecology of Kryptoperidinium sp. was examined in two Mediterranean shallow lagoons, Calich (CA) and Santa Giusta (SG) in Sardinia, Italy. Kryptoperidinium cell density and the environmental conditions were examined monthly from 2008 to 2015 in CA and from 2011 to 2016 in SG. Cell morphology was determined by observing specimens taken from the field and from cultures that were established by single-cell isolation from samples collected in the two lagoons. The molecular identity of strains from each lagoon was also ascertained. The growth rates of the strains were determined under three different temperature conditions and six salinity treatments. The two wild populations shared the same morphology and the cultured strains were morphologically and molecularly identical. The SSU and 5.8S phylogenies show the presence of two clusters within the available Kryptoperidinium sequences and the strains obtained in this study clustered with others from the Mediterranean and Baltic. The multiannual dynamics of Kryptoperidinium sp. in the field significantly differed in the two lagoons, showing much higher cell densities in CA than in SG. The presence of Kryptoperidinium sp. was detected throughout the year in CA, with recurrent blooms also affecting the adjacent coastal area. In contrast, Kryptoperidinium sp. was sporadically observed in SG. The variation in the environmental parameters was fairly wide during the presence and blooms of Kryptoperidinium sp., especially in CA. The application of Generalized Linear Models to the field data revealed a significant role of rainfall and dissolved inorganic nitrogen on the presence and blooms of the species. Although growth rates were similar between the two strains, significant differences were detected for the 10 and 40 salinity treatments. The results obtained in this study add to our knowledge about the ecology of a harmful species that is not well understood in transitional ecosystems such as Mediterranean lagoons.

Paralytic Shellfish Toxins and Cyanotoxins in the Mediterranean: New Data from Sardinia and Sicily (Italy).

Harmful algal blooms represent a severe issue worldwide. They affect ecosystem functions and related services and goods, with consequences on human health and socio-economic activities. This study reports new data on paralytic shellfish toxins (PSTs) from Sardinia and Sicily (Italy), the largest Mediterranean islands where toxic events, mainly caused by Alexandrium species (Dinophyceae), have been ascertained in mussel farms since the 2000s. The toxicity of the A. minutum, A. tamarense and A. pacificum strains, established from the isolation of vegetative cells and resting cysts, was determined by high performance liquid chromatography (HPLC). The analyses indicated the highest toxicity for A. pacificum strains (total PSTs up to 17.811 fmol cell-1). The PSTs were also assessed in a strain of A. tamarense. The results encourage further investigation to increase the knowledge of toxic species still debated in the Mediterranean. This study also reports new data on microcystins (MCs) and ß-N-methylamino-L-alanine (BMAA) from a Sardinian artificial lake (Lake Bidighinzu). The presence of MCs and BMAA was assessed in natural samples and in cell cultures by enzyme-linked immunosorbent assay (ELISA). BMAA positives were found in all the analysed samples with a maximum of 17.84 µg L-1. The obtained results added further information on cyanotoxins in Mediterranean reservoirs, particularly BMAA, which have not yet been thoroughly investigated.

Spatial distribution and multiannual trends of potentially toxic microalgae in shellfish farms along the Sardinian coast (NW Mediterranean Sea).

In this study, the geographical distribution and multiannual trends of potentially toxic harmful algal species (HAS) were analysed at 18 mussel farms in Sardinia (Italy, North-Western Mediterranean Sea) using data derived from the Sardinian Regional Monitoring Programme (1988-2012). The results showed an increasing number of potentially toxic microalgae over the study period. Alexandrium catenella and Alexandrium minutum were the most harmful species detected. From 2002 to 2009, these species caused eight paralytic shellfish poisoning-positive events which temporarily stopped commercial trade of mussels. The statistical analysis indicated that some taxa exhibited temporal increasing trends in their abundance (e.g. Pseudo-nitzschia spp.), significant decrements (e.g. Dinophysis sp.), or both increasing and decreasing significant trends (e.g. A. minutum) at different sites, indicating the necessity of further in-depth studies, especially on certain taxa. Overall, the statistical elaboration of the long-term data provided useful signals for early detection of shellfish contamination by different potentially toxic HAS in defined sites. These signals can be used to develop best management practices.