Marine Microbiota Responses to Shipping Scrubber Effluent Assessed at Community Structure and Function Endpoints.

The use of novel high-throughput sequencing (HTS) technologies to examine the responses of natural multidomain microbial communities to scrubber effluent discharges to the marine environment is still limited. Thus, we applied metabarcoding sequencing targeting the planktonic unicellular eukaryotic and prokaryotic fraction (phytoplankton, bacterioplankton, and protozooplankton) in mesocosm experiments with natural microbial communities from a polluted and an unpolluted site. Furthermore, metagenomic analysis revealed changes in the taxonomic and functional dominance of multidomain marine microbial communities after scrubber effluent additions. The results indicated a clear shift in the microbial communities after such additions, which favored bacterial taxa with known oil and polycyclic aromatic hydrocarbons (PAHs) biodegradation capacities. These bacteria exhibited high connectedness with planktonic unicellular eukaryotes employing variable trophic strategies, suggesting that environmentally relevant bacteria can influence eukaryotic community structure. Furthermore, Clusters of Orthologous Genes associated with pathways of PAHs and monocyclic hydrocarbon degradation increased in numbers at treatments with high scrubber effluent additions acutely. These genes are known to express enzymes acting at various substrates including PAHs. These indications, in combination with the abrupt decrease in the most abundant PAHs in the scrubber effluent below the limit of detection-much faster than their known half-lives-could point toward a bacterioplankton-initiated rapid ultimate biodegradation of the most abundant toxic contaminants of the scrubber effluent. The implementation of HTS could be a valuable tool to develop multilevel biodiversity indicators of the scrubber effluent impacts on the marine environment, which could lead to improved impact assessment. Environ Toxicol Chem 2024;43:1012-1029. © 2024 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

A catastrophic change in a european protected wetland: From harmful phytoplankton blooms to fish and bird kill.

Understanding the processes that underlay an ecological disaster represents a major scientific challenge. Here, we investigated phytoplankton and zooplankton community changes before and during a fauna mass kill in a European protected wetland. Evidence on gradual development and collapse of harmful phytoplankton blooms, allowed us to delineate the biotic and abiotic interactions that led to this ecological disaster. Before the mass fauna kill, mixed blooms of known harmful cyanobacteria and the killer alga Prymnesium parvum altered biomass flow and minimized zooplankton resource use efficiency. These blooms collapsed under high nutrient concentrations and inhibitory ammonia levels, with low phytoplankton biomass leading to a dramatic drop in photosynthetic oxygenation and a shift to a heterotrophic ecosystem phase. Along with the phytoplankton collapse, extremely high numbers of red planktonic crustaceans-Daphnia magna, visible through satellite images, indicated low oxygen conditions as well as a decrease or absence of fish predation pressure. Our findings provide clear evidence that the mass episode of fish and birds kill resulted through severe changes in phytoplankton and zooplankton dynamics, and the alternation on key abiotic conditions. Our study highlights that plankton-related ecosystem functions mirror the accumulated heavy anthropogenic impacts on freshwaters and could reflect a failure in conservation and restoration measures.

The genus Diaphanosoma (Diplostraca: Sididae) in Greece: morphological and molecular assessment.

For the genus Diaphanosoma Fischer (Cladocera) the species name D. brachyurum has been widely used for many decades to identify other species belonging to this genus. To clarify the diversity of the genus in Greek lakes in the present study, we morphologically and genetically identified the Diaphanosoma species occurring in eight lakes. Three hundred twenty-nine Diaphanosoma individuals were morphologically examined, while for the genetic analyses the mtDNA COI gene was sequenced in 48 individuals. Combining the morphological and genetic results, we verified the occurrence of D. mongolianum, D. orghidani and D. macedonicum in our study area. We could not confirm prior records of D. brachyurum and D. lacustris while we provide the molecular identity of D. macedonicum. Furthermore, we highlight the need to check whether the European D. mongolianum populations are characterised of mitochondrial discordance and hybridization as the individuals from the Asian type locality of the species. Our results support the importance of combining both approaches to correctly identify taxonomic species, despite the extra effort and cost during the sample analysis.

Rotifers from inland water bodies of continental Ecuador and Galápagos Islands: An updated checklist.

We present an updated checklist of the rotifer fauna from inland aquatic habitats in continental Ecuador and the Galápagos islands based on published rotifer records found in the literature. The checklist summarizes the status of the current taxonomic and faunistic knowledge on rotifers in Ecuador, updates the nomenclature, and reports the regions where each species has been found in the country. A total of 287 valid species (269 monogononts and 18 bdelloids was found. The Ecuadorian region with the highest number of records was Amazonia (228) followed by the Coastal region (139) and the Andes (121), whereas in the Galápagos Archipelago only 40 species have been recorded. Studies of the rotifer fauna of the areas are scarce and quite recent, pointing to important gaps in our knowledge on taxonomy and biogeography of Ecuadorian rotifers.

Reverse taxonomy applied to the Brachionus calyciflorus cryptic species complex: Morphometric analysis confirms species delimitations revealed by molecular phylogenetic analysis and allows the (re)description of four species.

The discovery and exploration of cryptic species have been profoundly expedited thanks to developments in molecular biology and phylogenetics. In this study, we apply a reverse taxonomy approach to the Brachionus calyciflorus species complex, a commonly studied freshwater monogonont rotifer. By combining phylogenetic, morphometric and morphological analyses, we confirm the existence of four cryptic species that have been recently suggested by a molecular study. Based on these results and according to an exhaustive review of the taxonomic literature, we name each of these four species and provide their taxonomic description alongside a diagnostic key.

Period of public commentary begins on the revised proposal of species-group level names, and on the proposal of genus-group level names of the Candidate Part of List of Available Names (LAN) in the phylum Rotifera.

Following ICZN (1999) Article 79 Chapter 17 http://www.nhm.ac.uk/hosted-sites/iczn/code/), we, with the full support of the international community of rotifer researchers as expressed during subsequent international Rotifera symposia, developed a Candidate Part of the List of Available Names for species and genera of Rotifera from the start of zoological nomenclature to the year 2000.

Integrative Taxonomy Recognizes Evolutionary Units Despite Widespread Mitonuclear Discordance: Evidence from a Rotifer Cryptic Species Complex.

Mitonuclear discordance across taxa is increasingly recognized as posing a major challenge to species delimitation based on DNA sequence data. Integrative taxonomy has been proposed as a promising framework to help address this problem. However, we still lack compelling empirical evidence scrutinizing the efficacy of integrative taxonomy in relation to, for instance, complex introgression scenarios involving many species. Here, we report remarkably widespread mitonuclear discordance between about 15 mitochondrial and 4 nuclear Brachionus calyciflorus groups identified using different species delimitation approaches. Using coalescent-, Bayesian admixture-, and allele sharing-based methods with DNA sequence or microsatellite data, we provide strong evidence in support of hybridization as a driver of the observed discordance. We then describe our combined molecular, morphological, and ecological approaches to resolving phylogenetic conflict and inferring species boundaries. Species delimitations based on the ITS1 and 28S nuclear DNA markers proved a more reliable predictor of morphological variation than delimitations using the mitochondrial COI gene. A short-term competition experiment further revealed systematic differences in the competitive ability between two of the nuclear-delimited species under six different growth conditions, independent of COI delimitations; hybrids were also observed. In light of these findings, we discuss the failure of the COI marker to estimate morphological stasis and morphological plasticity in the B. calyciflorus complex. By using B. calyciflorus as a representative case, we demonstrate the potential of integrative taxonomy to guide species delimitation in the presence of mitonuclear phylogenetic conflicts.

Updating the description and taxonomic status of Brachionus sessilis Varga, 1951 (Rotifera: Brachionidae) based on detailed morphological analysis and molecular data.

Brachionus sessilis Varga, 1951 is an epizoic rotifer living exclusively on cladocerans of the genus Diaphanosoma. Current taxonomic knowledge relies solely on limited morphological information, whereas there is no type material. Here, we aim to resolve issues concerning its morphology and taxonomy using both morphological and genetic characters on material sampled from Lake Balaton (Hungary), as well as Lake Doirani (Greece) that was selected for comparison purposes. Biometrical analysis was based on extensive lorica measurements. Phylogenetic reconstruction was based on DNA sequence information of the mitochondrial cytochrome c oxidase subunit I (COI) and 16S rRNA gene regions as well as of the nuclear internal transcribed spacer 1 (ITS1). Well-supported evidence for substantial differentiation of B. sessilis from its closest phylogenetic relatives supports its species-rank status. Our phylogenetic analysis suggests a highly supported clade encompassing B. sessilis and another epizoic rotifer, namely B. rubens. 

Phytoplankton and water quality in a Mediterranean drinking-water reservoir (Marathonas Reservoir, Greece).

Phytoplankton and water quality of Marathonas drinking-water Reservoir were examined for the first time. During the study period (July-September 2007), phytoplankton composition was indicative of eutrophic conditions although phytoplankton biovolume was low (max. 2.7 mm³ l⁻¹). Phytoplankton was dominated by cyanobacteria and diatoms, whereas desmids and dinoflagellates contributed with lower biovolume values. Changing flushing rate in the reservoir (up to 0.7% of reservoir's water volume per day) driven by water withdrawal and occurring in pulses for a period of 15-25 days was associated with phytoplankton dynamics. Under flushing pulses: (1) biovolume was low and (2) both 'good' quality species and the tolerant to flushing 'nuisance' cyanobacterium Microcystis aeruginosa dominated. According to the Water Framework Directive, the metrics of phytoplankton biovolume and cyanobacterial percentage (%) contribution indicated a moderate ecological water quality. In addition, the total biovolume of cyanobacteria as well as the dominance of the known toxin-producing M. aeruginosa in the reservoir's phytoplankton indicated a potential hazard for human health according to the World Health Organization.