Phytoplankton Blooms, Red Tides and Mucilaginous Aggregates in the Urban Thessaloniki Bay, Eastern Mediterranean

We investigated the plankton community composition and abundance in the urban marine environment of Thessaloniki Bay. We collected water samples weekly from March 2017 to February 2018 at the coastal front of Thessaloniki city center and monthly samples from three other inshore sites along the urban front of the bay. During the study period, conspicuous and successive phytoplankton blooms, dominated by known mucilage-producing diatoms alternated with red tide events formed by the dinoflagellates Noctiluca scintillans and Spatulodinium pseudonoctiluca, and an extensive mucilage aggregate phenomenon, which appeared in late June 2017. At least 11 known harmful algae were identified throughout the study, with the increase in the abundance of the known harmful dinoflagellate Dinophysis cf. acuminata occurring in October and November 2017. Finally, a red tide caused by the photosynthetic ciliate Mesodinium rubrum on December 2017 was conspicuous throughout the sampling sites. The above-mentioned harmful blooms and red tides were linked to high nutrient concentrations and eutrophication. This paper provides an overview of eutrophication impacts on the response of the unicellular eukaryotic plankton organisms and their impact on water quality and ecosystem service

Protist community composition during early phytoplankton blooms in the naturally iron-fertilized Kerguelen area (Southern Ocean)

International audienceAbstract. Microbial eukaryotic community composition was examined by 18S rRNA gene tag pyrosequencing, during the early phase of spring phytoplankton blooms induced by natural iron fertilization, off Kerguelen Island in the Southern Ocean (KEOPS2 cruise). A total of 999 operational taxonomical units (OTUs), affiliated to 30 known high-level taxonomic groups, were retrieved from 16 samples collected in the upper 300 m water column. The alveolata group was the most abundant in terms of sequence number and diversity (696 OTUs). The majority of alveolata sequences were affiliated to Dinophyceae and to two major groups of marine alveolates (MALV-I and MALV-II). In the upper 180 m, only 13% of the OTUs were shared between of the fertilized stations and the reference site characterized by high-nutrient low-chlorophyll (HNLC) waters. Fungi and Cercozoa were present in iron-fertilized waters, but almost absent in the HNLC samples, while Haptophyta and Chlorophyta characterized the HNLC sample. Finally, the 300 m depth samples of all stations were differentiated by the presence of MALV-II and Radiolaria. Multivariate analysis, examining the level of similarity between different samples, showed that protistan assemblages differed significantly between the HNLC and iron-fertilized stations, but also between the diverse iron-fertilized blooms

Editorial: Microbial Communities of Coastal Eutrophic Systems

[No abstract available

Airborne microeukaryote colonists in experimental water containers: diversity, succession, life histories and established food webs

Airborne freshwater and marine microeukaryotes in the city of Thessaloniki, situated in Thermaikos Bay, Greece, were examined as sources of colonization of experimental water containers during the period autumn 2007 to spring 2008. The microeukaryote composition of the plankton in the nearby aquatic systems (distance < 1 km) was also examined. Airborne microeukaryotes were examined by morphology and 18S rRNA gene diversity. A total of 29 species of airborne microeukaryotes were identified, most of them commonly observed in aerobiological studies. Airborne organisms of only 8 taxa were also detected in the nearby aquatic systems. The algae Haematococcus lacustris, a Chlorella-like taxon, and Scenedesmus cf. obliquus, the heterotrophic nanoflagellates (HNF) Bodo sp., Cafeteria minuta and Rynchomonas nasuta, and the ciliate Pattersoniella vitiphila were present in all 3 seasons, indicating capabilities of successful dispersal and colonization under a wide range of meteorological conditions. Rapid colonization of the water containers by the microeukaryotes occurred at the beginning of the experiment, but the rate of colonization quickly stabilized. The initial phase of colonization was dominated by HNF; subsequently, members of the Chlorophyta were the dominant autotrophs. The heterotrophic and autotrophic colonists established similar food webs in all 3 seasons, with P. vitiphila being the common top predator

Airborne algae and cyanobacteria: Occurrence and related health effects

Published information on airborne algae and cyanobacteria worldwide and the related human health effects is scarce. Since 1844, a total of 353 morphological taxa (genera or species) have been identified in aerobiological studies. However, due to diverse methodologies and different microorganisms targeted in these studies, direct comparisons on the occurrences of airborne algae and cyanobacteria in various studies are rather dubious. Thirty-eight airborne algae and cyanobacteria were shown to induce allergy, skin irritation, hay fever, rhinitis, sclerosis and respiratory problems when aerosolized and inhaled. Another 14 airborne taxa are known toxin producers posing threat to human health. Most frequently associated with health effects are the genera Chlorella, Scenedesmus, Chlorococcum, Klebsormidium (Hormidium) and Lyngbya. In the air of the Mediterranean city of Thessaloniki, we found 63 algal and cyanobacterial taxa, with 21 reported for the first time in the air. Seven taxa were potentially harmful. Algae and cyanobacteria can contribute significantly in the total air particle load, rendering them as causative agents for health issues when inhaled

Treatment of rheumatoid arthritis with gene therapy applications: Biosafety and bioethical considerations

Rheumatoid Arthritis (RA) is an autoimmune and inflammatory disease that affects the synovium (lining that surrounds the joints), causing the immune system to attack its own healthy tissues. Treatment options, to the current day, have serious limitations and merely offer short-term alleviation to the pain. Using a theoretical exercise based on literature, a new potentially viable therapy has been proposed. The new therapy focusses on a long-term treatment of RA based on gene therapy, which is only active when inflammation of the joint occurs. This treatment will prevent side effects of systemic application of drugs. Furthermore, the benefits of this treatment for the patient from a socio-economic perspective has been discussed, focusing on the quality of life of the patent and lower costs for the society. © 2021 by the authors. Licensee MDPI, Basel, Switzerland

Changes in microbial (Bacteria and archaea) plankton community structure after artificial dispersal in grazer-free microcosms

Microbes are considered to have a global distribution due to their high dispersal capabilities. However, our knowledge of the way geographically distant microbial communities assemble after dispersal in a new environment is limited. In this study, we examined whether communities would converge because similar taxa would be selected under the same environmental conditions, or would diverge because of initial community composition, after artificial dispersal. To this aim, a microcosm experiment was performed, in which the temporal changes in the composition and diversity of different prokaryoplankton assemblages from three distant geographic coastal areas (Banyuls-sur-Mer in northwest Mediterranean Sea, Pagasitikos Gulf in northeast Mediterranean and Woods Hole, MA, USA in the northwest Atlantic), were studied. Diversity was investigated using amplicon pyrosequencing of the V1–V3 hypervariable regions of the 16S rRNA. The three assemblages were grown separately in particle free and autoclaved Banyuls-sur-mer seawater at 18◦C in the dark. We found that the variability of prokaryoplankton community diversity (expressed as richness, evenness and dominance) as well as the composition were driven by patterns observed in Bacteria. Regarding community composition, similarities were found between treatments at family level. However, at the OTU level microbial communities from the three different original locations diverge rather than converge during incubation. It is suggested that slight differences in the composition of the initial prokaryoplankton communities, resulted in separate clusters the following days even when growth took place under identical abiotic conditions. © 2017 by the authors. Licensee MDPI, Basel, Switzerland

Molecular diversity reveals previously undetected air-dispersed protist colonists in a Mediterranean area

The molecular diversity of air-dispersed protists was examined through the 18S rRNA gene clone library construction in air samples and samples from experimental water containers passively collecting air-dispersed microorganisms, from July 2007 till October 2008 in three different sites of Northern Greece. The majority of the samplings took place in an urban industrialized coastal city (Thessaloniki). In all the samples, a total of 29 unique phylotypes were detected belonging to 10 known major taxonomic groups. The most abundant phylotypes were affiliated to known taxa of Ciliophora and Chlorophyceae, commonly found in various habitats. Additionally, various previously unnoticed and under-studied taxa, such as Bicosoecida, Oomycetes and Labyrinthulomycetes, were detected. These taxa are potentially important in ecological processes, through dispersal and colonization of various habitats. Multivariate statistical analysis associated the most abundant phylotypes with rainfall, suggesting that rain is a favorable means for reposition of air-dispersed protists. This is the first study investigating the molecular diversity of air-dispersed protists, including algae and heterotrophic protists. (c) 2014 Elsevier B.V. All rights reserved

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. © 2016 Vardaka et al