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The use of multi-wavelength spectrofluorometers for the fast detection of algal taxa, based on chlorophyll

The use of multi-wavelength spectrofluorometers for the fast detection of algal taxa, based on chlorophyll a (Chl-a) emission spectra, has become a common practice in freshwater water management, although concerns about their accuracy have been raised. Here, inter-laboratory comparisons using monoalgal cultures have been performed to assess the reliability of different spectrofluorometer models, alongside Chl-a extraction methods. Higher Chl-a concentrations were obtained when using the spectrofluorometers than extraction methods, likely due to the poor extraction efficiencies of solvents, highlighting that traditional extraction methods could underestimate algal or cyanobacterial biomass. Spectrofluorometers correctly assigned species to the respective taxonomic group, with low and constant percent attribution errors (Chlorophyta and Euglenophyceae 6–8%, Cyanobacteria 0–3%, and Bacillariophyta 10–16%), suggesting that functioning limitations can be overcome by spectrofluorometer re-calibration with fresh cultures. The monitoring of a natural phytoplankton assemblage dominated by Chlorophyta and Cyanobacteria gave consistent results among spectrofluorometers and with microscopic observations, especially when cell biovolume rather than cell density was considered. In conclusion, multi-wavelength spectrofluorometers were confirmed as valid tools for freshwater monitoring, whereas a major focus on intercalibration procedures is encouraged to improve their reliability and broaden their use as fast monitoring tools to prevent environmental and public health issues related to the presence of harmful cyanobacteria.

An inventory of phytoplankton diversity in 12 Adriatic ports was performed with the port baseline survey. Particular emphasis was put on the detection of harmful aquatic organisms and pathogens (HAOP) because of their negative impact on ecosystem, human health, and the economy. Phytoplanktonic HAOP are identified as species, either native or non-indigenous (NIS), which can trigger harmful algal blooms (HAB). A list of 691 taxa was prepared, and among them 52 were classified as HAB and five as NIS. Records of toxigenic NIS (Pseudo-nitzschia multistriata, Ostreopsis species including O. cf. ovata) indicate that the intrusion of non-native invasive phytoplankton species has already occurred in some Adriatic ports. The seasonal occurrence and abundance of HAOP offers a solid baseline for a monitoring design in ports in order to prevent ballast water uptake and possible expansion of HAOP outside their native region.

Marine biotoxins can accumulate in filter-feeders bivalve molluscs, that may represent a source of potential health problems being vectors of toxins, that are transferred to humans through their consumption. Harmful Algal Blooms impact on aquaculture may give also economic losses due to temporary closures of contaminated shellfish harvest and marketing. The presence of toxic algae for Paralytic Shellfish Poisoning (PSP), with recurrent toxic blooms of dinoflagellates, such as several Alexandrium species, been known since 2000 in the waters of an Ionian bay of Sicily, the Syracuse harbour, where shellfish farms are located. Our previous works reported in this area the positivity for PSP toxin in mussels (Mytilus galloprovincialis) with saxitoxin concentrations above the limit of the law and the simultaneous presence of toxic species of the genus Alexandrium in the waters. This work reports new recent episodes of algal blooms of Alexandrium minutum in the waters of the Syracuse harbour and PSP toxin contamination in farmed mussels, with values beyond the limits established by law, with the consequent immediate closure of the production area. PSP toxicity was detected with the MBA (Mouse Bioassay) with the confirm carried out with Lawrence method to quantify the total saxitoxin equivalents and characterize the toxic profile. Regular application of the implemented health plan is very important in order to prevent any risk and protect consumer health.

The “Serious Game” experiment was focused on the development of an integrated monitoring approach to oil spill events in the Mediterranean Sea; it was carried out in the Northern Tyrrhenian Sea, an area that is reported to have intense marine traffic often connected to operational oil discharges. Our experiment was designed in order to develop a rapid assessment of oil spill effects on phytoplankton community through the integration of satellite imagery, in situ sampling and new low-cost technologies. In particular, satellite images were frequently acquired to monitor the study area. When the oil slick was detected, a real time sampling survey was carried out with the support of the Italian Coast Guards, employed as Voluntary Observing Ships for the identification of the polluted area, as well as for sampling and measuring activities. During the experiment, numerous analyses were carried out on the controls (C1, C5, E1, E5) and oiled (M1, M2, M4) stations to assess the most useful methods to quantify the impact of oil slick on the phytoplankton community. Among the numerous methods used, phytoplankton qualitative and quantitative evaluation was indispensable to appreciate subtle changes among the different phytoplankton groups; it is therefore a crucial analysis to observe the short negative effects of oil exposure on microalgae. In addition, the C:N ratio was shown to be a reliable parameter to evaluate the presence of oil compounds in the particulate fraction. Also the new low-cost technology used (the vertical profiler T-FLaPpro) was proved to be an efficient support to the rapid assessment of the oil impact along the water column.