Matina Katsiapi

Plankton Microorganisms Coinciding with Two Consecutive Mass Fish Kills in a Newly Reconstructed Lake

Lake Karla, Greece, was dried up in 1962 and its refilling started in 2009. We examined the Cyanobacteria and unicellular eukaryotes found during two fish kill incidents, in March and April 2010, in order to detect possible causative agents. Both microscopic and molecular (16S/18S rRNA gene diversity) identification were applied. Potentially toxic Cyanobacteria included representatives of the Planktothrix and Anabaena groups. Known toxic eukaryotes or parasites related to fish kill events were Prymnesium parvum and Pfiesteria cf. piscicida, the latter being reported in an inland lake for the second time. Other potentially harmful microorganisms, for fish and other aquatic life, included representatives of Fungi, Mesomycetozoa, Alveolata, and Heterokontophyta (stramenopiles). In addition, Euglenophyta, Chlorophyta, and diatoms were represented by species indicative of hypertrophic conditions. The pioneers of L. Karlas plankton during the first months of its water refilling process included species that could cause the two observed fish kill events.

Artificially-born "killer" lake: Phytoplankton based water quality and microcystin affected fish in a reconstructed lake

Lake Karla (Greece) is an example of a lake ecosystem which was dried in 1960s and now is restored, facing various anthropogenic pressures, whereas it is also listed in the network of Greek protected areas in terms of its conservation value. The objective of the present study was to determine the presence of microcystins (MCYST) in the lake water and their accumulation in tissues of the commercial fish species Cyprinus carpio, along with the highlighting of phytoplankton community and general limnological features of Lake Karla, a newly reconstructed lake, the first year of its refilling. MCYST concentrations in water and fish tissues were determined by an enzyme-linked immunosorbent assay (ELISA). Results suggest that Lake Karla has undergone a progressive cultural eutrophication with frequent cyanobacterial blooms. The most dominant species in lakes phytoplankton were Anabaenopsis elenkinii, Sphaerospermopsis and Planktothrix agardhii. MCYST concentrations were detected in water samples comparable to those reported for other eutrophicated Mediterranean lakes while considerable amounts of MCYST were detected in the tissues of the species C. carpio in the following order: liver>kidney>brain>intestine>muscles. The presence of prominent cyanobacterial blooms dominated by toxic species highlights the need to undertake eutrophication control measures so as to avoid further toxicological problems.

Watershed land use types as drivers of freshwater phytoplankton structure

The potential importance of watershed land use types, lake/watershed morphometry/topography and geographic distance as drivers of phytoplankton community composition was evaluated by using data collected from 18 freshwaters (lakes and reservoirs) distributed around Greece. In all freshwaters, phytoplankton species composition showed a strong correlation with the composition of land uses within their watersheds but no correlation with morphometry/topography and geographic distance. Cyanobacteria were found to be associated with artificial and agricultural land use types. Chrysophytes were closely associated to forested areas whereas euglenophytes to industrial, commercial, and transport units. Phytoplankton total biomass was significantly higher in freshwaters with a cover of agricultural and artificial land use >30% in their watersheds. This rather low threshold of agricultural and artificial land use cover might be indicative of the higher sensitivity of Mediterranean freshwaters to eutrophication process. Analysis performed separately for lakes and reservoirs revealed some diverse patterns with lake morphometric/topographic variables significantly affecting similarity in species occurrence. The results demonstrate that land use types reflecting anthropogenic pressures could act as critical drivers explaining phytoplankton structure. Our research suggests that Mediterranean freshwaters could be highly sensitive to land use types within their watersheds, thus landscape structure and configuration should be taken into account toward effective conservation and management plans.

Assessing ecological water quality of freshwaters: PhyCoI—a new phytoplankton community Index

Highlights: • We propose a new Phytoplankton Index for monitoring the ecological status of lakes. • We develop a community index integrating the response to anthropogenic pressure. • We link high frequency Secchi depth with low frequency phytoplankton monitoring. • We demonstrate the correlation of the index with land use on the watershed scale. • The index offers a cost-effective tool, practical for medium-qualified personnel. Abstract: We propose and test a new Phytoplankton Community Index (PhyCoI) for monitoring the ecological status of lakes and reservoirs. The design of our PhyCoI is based on the fact that phytoplankton biomass and community structure respond to changes in water quality (mainly eutrophication) and by themselves also influence water quality. In order to accommodate this double role of phytoplankton as indicator and impact, PhyCoI is based on phytoplankton community properties at different hierarchical levels combining both specific metrics (total biomass, taxonomic group biomass, cyanobacteria contribution, taxonomic group species richness) and new or modified sub-indices. It is calculated from the scores of the different metrics/sub-indices resulting in a final index value in the range from 0 to 5, to assess water quality on the basis of five ecological classes according to the Water Framework Directive (WFD). The test of PhyCoI was based on Carlsons Trophic State Index (TSISD) based on water transparency (Secchi depth) in 26 Greek lakes and reservoirs covering the entire spectrum from oligotrophic to hypertrophic. A highly significant relationship at p < 0.001 between the two variables was found, with the values of the PhyCoI declining with increasing TSISD. Furthermore, a significant relationship between the PhyCoI and land use types at the watershed of the studied freshwaters was found identifying permanent crops, pastures and shrubs and herbaceous vegetation associations as significant predictors of PhyCoI values. Because of the amount of labor involved in obtaining the PhyCoI we suggest to combine low frequency PhyCoI determinations with a high frequency Secchi depth measurements for practical monitoring purposes.

Molecular diversity of bacteria in commercially available “Spirulina” food supplements

The cyanobacterium Arthrospira is among the most well-known food supplements worldwide known as “Spirulina.” While it is a widely recognized health-promoting natural product, there are no reports on the molecular diversity of commercially available brands of “Spirulina” supplements and the occurrence of other cyanobacterial and heterotrophic bacterial microorganisms in these products. In this study, 454-pyrosequencing analysis of the total bacterial occurrence in 31 brands of “Spirulina” dietary supplements from the Greek market was applied for the first time. In all samples, operational taxonomic units (OTUs) of Arthrospira platensis were the predominant cyanobacteria. Some products contained additional cyanobacterial OTUs including a few known potentially toxic taxa. Moreover, 469 OTUs were detected in all 31 products collectively, with most of them being related to the Proteobacteria, Firmicutes, Bacteroidetes, Actinobacteria and Verrucomicrobia. All samples included heterotrophic bacterial OTUs, ranging from 9–157 per product. Among the most common OTUs were ones closely related to taxa known for causing health issues (i.e., Pseudomonas, Flavobacterium, Vibrio, Aeromonas, Clostridium, Bacillus, Fusobacterium, Enterococcus). The observed high cyanobacterial and heterotrophic bacterial OTUs richness in the final product is a point for further research on the growth and processing of Arthrospira biomass for commercial purposes.

Implementation of the Water Framework Directive: Lessons learned and future perspectives for an ecologically meaningful classification of the status of Greek lakes, Mediterranean region

The enactment of the Water Framework Directive (WFD) initiated scientific efforts to develop reliable methods for comparing prevailing lake conditions against reference (or non-impaired) states, using the state of a set biological elements. Drawing a distinction between impaired and natural conditions can be a challenging exercise, as it stipulates the robust delineation of reference conditions along with the establishment of threshold values for key environmental variables used as proxies for the degree of system impairment. Another important aspect is to ensure that water quality assessment is comparable among the different Member States. In this context, the present paper offers a constructive critique of the practices followed during the WFD implementation in Greece by pinpointing methodological weaknesses and knowledge gaps that undermine our ability to classify the ecological status of Greek lakes. One of the pillars of WDF is a valid lake typology that sets ecological standards transcending geographic regions and national boundaries. The national typology of Greek lakes has failed to take into account essential components (e.g. surface area, altitude, salinity). WFD compliance assessments based on descriptions of phytoplankton communities are oversimplified and as such should be revisited. Exclusion of most chroococcal species from the analysis of cyanobacteria biovolume in Greek lakes and most reservoirs in the Mediterranean Geographical Intercalibration Group (Greece, Spain, Portugal and Cyprus) is not consistent with the distribution of those taxa in lakes. Similarly, the total biovolume reference values and the indices used in their classification schemes reflect misunderstandings of WFD core principles. This hampers the comparability of ecological status across Europe and leads to quality standards that are too relaxed to provide an efficient target especially for the protection and management of Greek/transboundary lakes such as Lake Megali Prespa, one of the oldest lakes in Europe.

Cyanotoxins as the “common suspects” for the Dalmatian pelican ( Pelecanus crispus ) deaths in a Mediterranean reconstructed reservoir

Toxic cyanobacterial blooms have been implicated for their negative consequences on many terrestrial and aquatic organisms. Water birds belong to the most common members of the freshwater food chains and are most likely to be affected by the consumption of toxic cyanobacteria as food. However, the contribution of cyanotoxins in bird mortalities is under-studied. The aim of the study was to investigate the likely role of cyanotoxins in a mass mortality event of the Dalmatian pelican (Pelecanus crispus) in the Karla Reservoir, in Greece. Water, scum, tissues and stomach content of dead birds were examined for the presence of microcystins, cylindrospermopsins and saxitoxins by an enzyme-linked immunosorbent assay. High abundances of potential toxic cyanobacterial species and significant concentrations of cyanotoxins were recorded in the reservoir water. All examined tissues and stomach content of the Dalmatian pelicans contained significant concentrations of microcystins and saxitoxins. Cylindrospermopsin concentrations were detected in all tissues except from the brain. Our results suggest that cyanotoxins are a plausible cause for this bird mass mortality episode in the Karla Reservoir.

First report of Aphanizomenon favaloroi occurrence in Europe associated with saxitoxins and a massive fish kill in Lake Vistonis, Greece

The cyanobacterium Aphanizomenon favaloroi was identified for the first time in Europe in the Mediterranean brackish Lake Vistonis during July–August 2014. It formed a dense bloom (from 16×106 to 81×106 trichomes L–1), causing a brown colouration of the lake water. When A. favaloroi formed 100% of the total phytoplankton biomass (44mg L–1), saxitoxins (saxitoxin and neo-saxitoxin) were detected in the lake seston (42 and 17μg g–1 phytoplankton dry weight respectively), which was screened for saxitoxins, cylindrospermopsin, anatoxin-a, microcystins and nodularin. A massive fish kill coincided with the A. favaloroi bloom. This new saxitoxin-producing species of cyanobacteria, with traits for successful dispersal, may pose a health risk to animals and humans and cause adverse effects on water quality and water services because of its expansion potential.