Contribution of invasive bivalves (Dreissena spp.) to element distribution: phase interaction, regional and seasonal comparison in a large shallow lake

After introduction, the invasive bivalve dreissenids became key species in the biota of Lake Balaton, the largest shallow lake in Central Europe. The contribution of dreissenid soft tissue and shell, as biotic phases, in element distribution and its interaction with the water and upper sediment phases were examined in two basins with different trophic conditions in spring and autumn. Six metals (Ba, Cu, Fe, Mn, Pb, Zn) were detected in all investigated phases. In general, metals were abundant in the water and soft tissue in the eastern basin in spring, and in the sediment and shells in the western basin in autumn. This might be associated with the more urbanized surroundings in the eastern, and the enhanced organic matter production in the western basin. High relative shares of Ba, Cu, Mn, and Pb were associated with the water and shell samples, whereas high shares of Fe and Zn were noted in the soft mussel tissue and sediments. Results suggest that dynamics of metal uptake by dreissenids depend on the seasonal change in metabolic activity. Shell metal content is less changeable; shells might absorb metals from both the soft tissue and water phases. Metallothionein peptides, the scavengers of intracellular metals, were determined to be biomarkers of the bulk contaminants rather than only metals. The present study shows that invasive bivalves, with high abundance, filtering activity, and storing capacity can significantly contribute to element distribution in the shoreline of a shallow lake ecosystem.

Unique issues of the species concept in molluscs of the genus Corbicula: a mismatch of mitochondrial and nuclear genomes

Molluscs of the genus Corbicula are well-known invasive bivalves found all over the world. These ecologically important clams are characterised by a wide range of habitats (both brackish waters and freshwater environments) and by contrasting modes of reproduction in native ranges (including sexual and asexual modes) and in invasive ranges (asexual mode). The asexual freshwater Corbicula reproduces through androgenetic fertilization, also termed “egg parasitism”, where the oocyte nucleus is replaced by the spermatozoon nucleus, yet the mitochondria are inherited from the mother cell. This results in a mismatch between the genetic material of the nucleus and mitochondria (and, accordingly, with the external morphology of the shell). In addition, the low nucleotide diversity in the genus Corbicula challenges the delimitation of separate species, thus it is difficult to apply the traditional taxonomic and phylogenetic species criteria to Corbicula populations.

Structure, function and parallel evolution of the bivalve byssus, with insights from proteomes and the zebra mussel genome

The byssus is a structure unique to bivalves. Byssal threads composed of many proteins extend like tendons from muscle cells, ending in adhesive pads that attach underwater. Crucial to settlement and metamorphosis, larvae of virtually all species are byssate. By contrast, in adults, the byssus is scattered throughout bivalves, where it has had profound effects on morphological evolution and been key to adaptive radiations of epifaunal species. I compare byssus structure and proteins in blue mussels ( Mytilus ), by far the best characterized, to zebra mussels ( Dreissena polymorpha ), in which several byssal proteins have been isolated and sequenced. By mapping the adult byssus onto a recent phylogenomic tree, I confirm its independent evolution in these and other lineages, likely parallelisms with common origins in development. While the byssus is superficially similar in Dreissena and Mytilus , in finer detail it is not, and byssal proteins are dramatically different. I used the chromosome-scale D. polymorpha genome we recently assembled to search for byssal genes and found 37 byssal loci on 10 of the 16 chromosomes. Most byssal genes are in small families, with several amino acid substitutions between paralogs. Byssal proteins of zebra mussels and related quagga mussels ( D. rostriformis ) are divergent, suggesting rapid evolution typical of proteins with repetitive low complexity domains. Opportunities abound for proteomic and genomic work to further our understanding of this textbook example of a marine natural material. A priority should be invasive bivalves, given the role of byssal attachment in the spread of, and ecological and economic damage caused by zebra mussels, quagga mussels and others. This article is part of the Theo Murphy meeting issue ‘Molluscan genomics: broad insights and future directions for a neglected phylum’.

Massive economic costs of invasive bivalves in freshwater ecosystems

Many countries lack the economic capacity to effectively manage invasive species. Yet, the direct socioeconomic impact generally much outweighs the expected costs of prevention. A distinct lack of monetary cost quantification associated with key invasive species groups impedes decision-making, and thus resource allocation, by policy makers to address invasions. Here, we synthesize published global economic costs of impacts for one key taxonomic group – freshwater bivalves – whilst explicitly considering the reliability of estimation methodologies, cost types, economic sectors and impacted regions. Although several species from this group are notorious widespread invaders, estimations of their economic costs have remained relatively sparse. Cumulative total global costs of invasive macrofouling bivalves were US$ 63.6 billion (2017 USD) across all regions and socioeconomic sectors between 1980 and 2020. Costs were heavily biased taxonomically and spatially, dominated by two families, Dreissenidae and Cyrenidae (Corbiculidae), and largely constrained to North America. The largest share of reported costs ($ 30.6 billion) did not make the distinction between damage and management. However, of those that did, damages and resource losses were one order of magnitude higher ($ 30.3 billion) than control or preventative measures ($ 1.7 billion). Moreover, although many impacted socioeconomic sectors lacked specification, the largest shares of costs were incurred through authorities and stakeholders ($ 26.3 billion, e.g. public and private sector interventions) and by public and social welfare ($ 11.6 billion, e.g. via power/drinking water plant and irrigation system damage). Average cost estimates over the entire period amounted to approximately $ 1.6 billion per year, most of which was incurred in North America. We thus present novel cost quantifications that offer a strong economic incentive to invest in preventative management of invasive bivalves in freshwaters. However, these costs are severely underestimated because well-documented economic impacts are lacking for most invaded countries and most invasive bivalve species.

Metabarcoding with MinION: Speeding up the detection of invasive aquatic species using environmental DNA and nanopore sequencing

Traditional detection of aquatic invasive species, via morphological identification is often time-consuming and can require a high level of taxonomic expertise, leading to delayed mitigation responses. Environmental DNA (eDNA) detection approaches of multiple species using Illumina-based sequencing technology have been used to overcome these hindrances, but sample processing is often lengthy. More recently, portable nanopore sequencing technology has become available, which has the potential to make molecular detection of invasive species more widely accessible and to substantially decrease sample turnaround times. However, nanopore-sequenced reads have a much higher error rate than those produced by Illumina platforms, which has so far hindered the adoption of this technology. We provide a detailed laboratory protocol and bioinformatic tools to increase the reliability of nanopore sequencing to detect invasive species, and we test its application using invasive bivalves. We sampled water from sites with pre-existing bivalve occurrence and abundance data, and contrasting bivalve communities, in Italy and Portugal. We extracted, amplified and sequenced eDNA with a turnaround of 3.5 days. The majority of processed reads were ≥ 99 % identical to reference sequences. There were no taxa detected other than those known to occur. The lack of detections of some species at some sites could be explained by their known low abundances. The approach is now being tested on other target taxa such as fish and other vertebrates.

Molecular diet analysis in zebra and quagga mussels (Dreissena spp.) and an assessment of the utility of aquatic filter feeders as biological eDNA filters

Molecular gut content analysis is a popular tool to study food web interactions and was recently also suggested as an alternative source for DNA based biomonitoring. However, the overabundant consumer’s DNA often outcompetes that of its diet during PCR. Blocking approaches are an efficient means to reduce consumer amplification while retaining broad specificity for dietary taxa. We here designed an assay to monitor the eukaryotic diet of mussels and test their utility as biological eDNA filters to monitor planktonic communities. We designed several rDNA primer sets with a broad taxonomic suitability for eukaryotes, which suppress the amplification of mussels. The primers were tested using mussel DNA extracts and the results were compared to eDNA water samples collected next to the mussel colonies. Taxonomic recovery, as well as patterns of alpha and beta diversity, were compared between mussels and water samples. In addition, we analyzed time series samples of mussel samples from different German rivers. Our primer sets efficiently block the amplification of various mussel genera. The recovered DNA reflects a broad dietary preference across the eukaryotic tree of life and considerable taxonomic overlap with filtered water samples. We also recover various taxa of possible commensals and parasites, associated with the mussels. Our protocol will enable large scale dietary analysis in mussels, facilitate aquatic food web analysis, elucidate the ecological impact of invasive bivalves and the rapid survey of mussel aquacultures for pathogens. Moreover, we show that mussels could serve as an interesting complementary DNA source for biomonitoring.

Marine bioinvasions: bivalve molluscs introduced in northeast Brazil

ABSTRACT: Invasive alien species are those that, once introduced from other environments, adapt, starting to reproduce and proliferate in places they did not previously inhabit. The introduction of exotic marine species as a result of anthropic activity, whether intentionally or not, is a process that has been remote for centuries, which makes it difficult to assess the impact of these activities, making studies that address the status of knowledge about such organisms always important. Thus, this research aims to gather information about bivalve molluscs introduced into marine ecosystems in northeastern Brazil, in addition to discussing the knowledge of this invasive fauna for the Northeast, Southeast and South regions of Brazil. For that there was a search for bibliography in 5 databases - SciELO, Web of Science, Google Scholar, ScienceResearch.com and I3N Brazil Database of the Horus Institute for Environmental Conservation and Development. Three invasive bivalves for the northeastern region of Brazil were counted. When compared to the South and Southeast regions, the Northeast presents a significant amount of research on the ecology of the species Isognomon bicolor (C. B. Adams, 1845) and Mytilopsis leucophaeata (Conrad, 1831), which is very important, because with these results it is possible to track and understand the pathways that make bioinvasions possible. Regarding Perna Perna (Linnaeus, 1758), although there is a discussion about its supposed introduction in Brazilian waters, the species can be considered invasive in Northeastern Brazil. KEYWORDS: Invasive species, marine ecosystem, ecology.

Speeding up the detection of invasive aquatic species using environmental DNA and nanopore sequencing

Traditional detection of aquatic invasive species, via morphological identification is often time-consuming and can require a high level of taxonomic expertise, leading to delayed mitigation responses. Environmental DNA (eDNA) detection approaches of multiple species using Illumina-based sequencing technology have been used to overcome these hindrances, but sample processing is often lengthy. More recently, portable nanopore sequencing technology has become available, which has the potential to make molecular detection of invasive species more widely accessible and to substantially decrease sample turnaround times. However, nanopore-sequenced reads have a much higher error rate than those produced by Illumina platforms, which has so far hindered the adoption of this technology. We provide a detailed laboratory protocol and bioinformatic tools to increase the reliability of nanopore sequencing to detect invasive species, and we test its application using invasive bivalves. We sampled water from sites with pre-existing bivalve occurrence and abundance data, and contrasting bivalve communities, in Italy and Portugal. We extracted, amplified and sequenced eDNA with a turnaround of 3.5 days. The majority of processed reads were ≥ 99 % identical to reference sequences. There were no taxa detected other than those known to occur. The lack of detections of some species at some sites could be explained by their known low abundances. This is the first reported use of MinION to detect aquatic invasive species from eDNA samples. The approach can be easily adapted for other metabarcoding applications, such as biodiversity assessment, ecosystem health assessment and diet studies.

Bioremediation of Wastewater using Invasive Bivalves

The contaminant concentration in water bodies are increasing with the increase in industrialization of the country. Pollution of water is measured by the parameters like BOD, COD, nutrients (N,P & K), and pathogens. The COD can occur due to industrialization pollutants. Eutrophication is caused due to the presence of N,P and K in the water bodies. The polluted water can be treated by chemical and physical methods. In physical treatment methods decontamination is done by using biological activities like biofiltration and bioaccumulation. In this study physical method (biofiltration) is adopted using ‘invasive bivalves’ as media. Wastewater can be decontaminated near to 85% using bivalves. The main types of the bivalves used in this study are dressina polymorpha, mytilus edulis and corbiculaflumina. These bivalves decrease the contamination level and these will encompass nutrient and phosphorus removal for recovery of eutrophic sites. They have also capacity of removing biological and chemical contaminants from water. The mechanism involved to reduce the contaminant concentration is biofiltration using bivalves.