Marine zooplankton are rapid-responders and useful indicators of environmental variability and climate change impacts on pelagic ecosystems on time scales ranging from seasons to years to decades. The systematic complexity and taxonomic diversity of the zooplankton assemblage has presented significant challenges for routine morphological (microscopic) identification of species in samples collected during ecosystem monitoring and fisheries management surveys. Metabarcoding using the mitochondrial Cytochrome Oxidase I (COI) gene region has shown promise for detecting and identifying species of some – but not all – taxonomic groups in samples of marine zooplankton. This study examined species diversity of zooplankton on the Northwest Atlantic Continental Shelf using 27 samples collected in 2002-2012 from the Gulf of Maine, Georges Bank, and Mid-Atlantic Bight during Ecosystem Monitoring (EcoMon) Surveys by the NOAA NMFS Northeast Fisheries Science Center. COI metabarcodes were identified using the MetaZooGene Barcode Atlas and Database ( https://metazoogene.org/MZGdb ) specific to the North Atlantic Ocean. A total of 181 species across 23 taxonomic groups were detected, including a number of sibling and cryptic species that were not discriminated by morphological taxonomic analysis of EcoMon samples. In all, 67 species of 15 taxonomic groups had ≥ 50 COI sequences; 23 species had >1,000 COI sequences. Comparative analysis of molecular and morphological data showed significant correlations between COI sequence numbers and microscopic counts for 5 of 6 taxonomic groups and for 5 of 7 species with >1,000 COI sequences for which both types of data were available. Multivariate statistical analysis showed clustering of samples within each region based on both COI sequence numbers and EcoMon counts, although differences among the three regions were not statistically significant. The results demonstrate the power and potential of COI metabarcoding for identification of species of metazoan zooplankton in the context of ecosystem monitoring.
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New insights into biodiversity, biogeography, ecology, and evolution of marine zooplankton based on molecular approaches
Marine zooplankton are key players in pelagic food webs, central links in ecosystem function, useful indicators of water masses, and rapid responders to environmental variation and climate change. Characterization of biodiversity of the marine zooplankton assemblage is complicated by many factors, including systematic complexity of the assemblage, with numerous rare and cryptic species, and high local-to-global ratios of species diversity. The papers in this themed article set document important advances in molecular protocols and procedures, integration with morphological taxonomic identifications, and quantitative analyses (abundance and biomass). The studies highlight several overarching conclusions and recommendations. A primary issue is the continuing need for morphological taxonomic experts, who can identify species and provide voucher specimens for reference sequence databases, which are essential for biodiversity analyses based on molecular approaches. The power of metabarcoding using multi-gene markers, including both DNA (Deoxyribonucleic Acid) and RNA (Ribonucleic Acid)templates, is demonstrated. An essential goal is the accurate identification of species across all taxonomic groups of marine zooplankton, with particular concern for detection of rare, cryptic, and invasive species. Applications of molecular approaches include analysis of trophic relationships by metabarcoding of gut contents, as well as investigation of the underlying ecological and evolutionary forces driving zooplankton diversity and structure.
more » « less- Award ID(s):
- 1840868
- NSF-PAR ID:
- 10308501
- Publisher / Repository:
- Oxford University Press
- Date Published:
- Journal Name:
- ICES Journal of Marine Science
- Volume:
- 78
- Issue:
- 9
- ISSN:
- 1054-3139
- Page Range / eLocation ID:
- p. 3281-3287
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Abstract Characterization of species diversity of zooplankton is key to understanding, assessing, and predicting the function and future of pelagic ecosystems throughout the global ocean. The marine zooplankton assemblage, including only metazoans, is highly diverse and taxonomically complex, with an estimated ~28,000 species of 41 major taxonomic groups. This review provides a comprehensive summary of DNA sequences for the barcode region of mitochondrial cytochrome oxidase I (COI) for identified specimens. The foundation of this summary is the MetaZooGene Barcode Atlas and Database (MZGdb), a new open-access data and metadata portal that is linked to NCBI GenBank and BOLD data repositories. The MZGdb provides enhanced quality control and tools for assembling COI reference sequence databases that are specific to selected taxonomic groups and/or ocean regions, with associated metadata (e.g., collection georeferencing, verification of species identification, molecular protocols), and tools for statistical analysis, mapping, and visualization. To date, over 150,000 COI sequences for ~ 5600 described species of marine metazoan plankton (including holo- and meroplankton) are available via the MZGdb portal. This review uses the MZGdb as a resource for summaries of COI barcode data and metadata for important taxonomic groups of marine zooplankton and selected regions, including the North Atlantic, Arctic, North Pacific, and Southern Oceans. The MZGdb is designed to provide a foundation for analysis of species diversity of marine zooplankton based on DNA barcoding and metabarcoding for assessment of marine ecosystems and rapid detection of the impacts of climate change.
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Hauser, Lorenz (Ed.)Abstract Metabarcoding of zooplankton communities is becoming more common, but molecular results must be interpreted carefully and validated with morphology-based analyses, where possible. To evaluate our metabarcoding approach within the California Current Ecosystem, we tested whether physical subsampling and PCR replication affects observed community composition; whether community composition resolved by metabarcoding is comparable to morphological analyses by digital imaging; and whether pH neutralization of ethanol with ammonium hydroxide affects molecular diversity. We found that (1) PCR replication was important to accurately resolve alpha diversity and that physical subsampling can decrease sensitivity to rare taxa; (2) there were significant correlations between relative read abundance and proportions of carbon biomass for most taxonomic groups analyzed, but such relationships showed better agreement for the more dominant taxonomic groups; and (3) ammonium hydroxide in ethanol had no effect on molecular diversity. Together, these results indicate that with appropriate replication, paired metabarcoding and morphological analyses can characterize zooplankton community structure and biomass, and that metabarcoding methods are to some extent indicative of relative community composition when absolute measures of abundance or biomass are not available.more » « less
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Abstract Although metazoan animals in the mesopelagic zone play critical roles in deep pelagic food webs and in the attenuation of carbon in midwaters, the diversity of these assemblages is not fully known. A metabarcoding survey of mesozooplankton diversity across the epipelagic, mesopelagic and upper bathypelagic zones (0–1500 m) in the North Pacific Subtropical Gyre revealed far higher estimates of species richness than expected given prior morphology‐based studies in the region (4,024
OTU s, 10‐fold increase), despite conservative bioinformatic processing. Operational taxonomic unit (OTU ) richness of the full assemblage peaked at lower epipelagic–upper mesopelagic depths (100–300 m), with slight shoaling of maximal richness at night due to diel vertical migration, in contrast to expectations of a deep mesopelagic diversity maximum as reported for several plankton groups in early systematic and zoogeographic studies. Four distinct depth‐stratified species assemblages were identified, with faunal transitions occurring at 100 m, 300 m and 500 m. Highest diversity occurred in the smallest zooplankton size fractions (0.2–0.5 mm), which had significantly lower %OTU s classified due to poor representation in reference databases, suggesting a deep reservoir of poorly understood diversity in the smallest metazoan animals. A diverse meroplankton assemblage also was detected (350OTU s), including larvae of both shallow and deep living benthic species. Our results provide some of the first insights into the hidden diversity present in zooplankton assemblages in midwaters, and a molecular reappraisal of vertical gradients in species richness, depth distributions and community composition for the full zooplankton assemblage across the epipelagic, mesopelagic and upper bathypelagic zones. -
Fields, David (Ed.)Abstract Community-based diversity analyses, such as metabarcoding, are increasingly popular in the field of metazoan zooplankton community ecology. However, some of the methodological uncertainties remain, such as the potential inflation of diversity estimates resulting from contamination by pseudogene sequences. Furthermore, primer affinity to specific taxonomic groups might skew community composition and structure during PCR. In this study, we estimated OTU (operational taxonomic unit) richness, Shannon’s H’, and the phylum-level community composition of samples from a coastal zooplankton community using four approaches: complement DNA (cDNA) and genomic DNA (gDNA) mitochondrial COI (Cytochrome oxidase subunit I) gene amplicon, metatranscriptome sequencing, and morphological identification. Results of mismatch distribution demonstrated that 90% is good threshold percentage to differentiate intra- and inter-species. Moderate level of correlations appeared upon comparing the species/OTU richness estimated from the different methods. Results strongly indicated that diversity inflation occurred in the samples amplified from gDNA because of mitochondrial pseudogene contamination (overall, gDNA produced two times more richness compared with cDNA amplicons). The unique community compositions observed in the PCR-based methods indicated that taxonomic amplification bias had occurred during the PCR. Therefore, it is recommended that PCR-free approaches be used whenever resolving community structure represents an essential aspect of the analysis.more » « less
