Ecological genomics in the Northern krill uncovers loci for local adaptation across ocean basins.

Krill are vital as food for many marine animals but also impacted by global warming. To learn how they and other zooplankton may adapt to a warmer world we studied local adaptation in the widespread Northern krill (Meganyctiphanes norvegica). We assemble and characterize its large genome and compare genome-scale variation among 74 specimens from the colder Atlantic Ocean and warmer Mediterranean Sea.

Recurring seasonality exposes dominant species and niche partitioning strategies of open ocean picoeukaryotic algae.

Ocean spring phytoplankton blooms are dynamic periods important to global primary production. We document vertical patterns of a diverse suite of eukaryotic algae, the prasinophytes, in the North Atlantic Subtropical Gyre with monthly sampling over four years at the Bermuda Atlantic Time-series Study site. Water column structure was used to delineate seasonal stability periods more ecologically relevant than seasons defined by calendar dates.

RotoBOD─Quantifying Oxygen Consumption by Suspended Particles and Organisms.

Sinking or floating is the natural state of planktonic organisms and particles in the ocean. Simulating these conditions is critical when making measurements, such as respirometry, because they allow the natural exchange of substrates and products between sinking particles and water flowing around them and prevent organisms that are accustomed to motion from changing their metabolism. We developed a rotating incubator, the RotoBOD (named after its capability to rotate and determine biological oxygen demand, BOD), that uniquely enables automated oxygen measurements in small volumes while keeping the samples in their natural state of suspension.

Removal of Exogenous Stimuli Reveals a Canalization of Circadian Physiology in a Vertically Migrating Copepod.

Diel rhythms are observed across taxa and are important for maintaining synchrony between the environment and organismal physiology. A striking example of this is the diel vertical migration undertaken by zooplankton, some of which, such as the 5 mm-long copepod (), migrate hundreds of meters daily between the surface ocean and deeper waters. Some of the molecular pathways that underlie the expressed phenotype at different stages of this migration are entrained by environmental variables (e.

MetaZooGene Atlas and Database: Reference Sequences for Marine Ecosystems.

The MetaZooGene Atlas and Database (MZGdb; https://metazoogene.org/mzgdb/ ) is an open-access data and metadata portal synchronized with the NCBI GenBank and BOLD data repositories. The MZGdb includes sequences for genes used for the classification and identification of marine organisms based on DNA barcoding and metabarcoding.

Role of Syndiniales parasites in depth-specific networks and carbon flux in the oligotrophic ocean.

Microbial associations that result in phytoplankton mortality are important for carbon transport in the ocean. This includes parasitism, which in microbial food webs is dominated by the marine alveolate group, Syndiniales. Parasites are expected to contribute to carbon recycling via host lysis; however, knowledge on host dynamics and correlation to carbon export remain unclear and limit the inclusion of parasitism in biogeochemical models.

Diel metabolic patterns revealed by in situ transcriptome and proteome in a vertically migratory copepod.

Zooplankton undergo a diel vertical migration (DVM) which exposes them to gradients of light, temperature, oxygen, and food availability on a predictable daily schedule. Disentangling the co-varying and potentially synergistic interactions on metabolic rates has proven difficult, despite the importance of this migration for the delivery of metabolic waste products to the distinctly different daytime (deep) and nighttime (surface) habitats. This study examines the transcriptomic and proteomic profiles of the circumglobal migratory copepod, Pleuromamma xiphias, over the diel cycle.

Morphological and taxonomic diversity of mesozooplankton is an important driver of carbon export fluxes in the ocean.

Mesozooplankton is a very diverse group of small animals ranging in size from 0.2 to 20 mm not able to swim against ocean currents. It is a key component of pelagic ecosystems through its roles in the trophic networks and the biological carbon pump.

Divergent patterns of zooplankton connectivity in the epipelagic and mesopelagic zones of the eastern North Pacific.

Due to historical under-sampling of the deep ocean, the distributional ranges of mesopelagic zooplankton are not well documented, leading to uncertainty about the mechanisms that shape midwater zooplankton community composition. Using a combination of DNA metabarcoding (18S-V4 and mtCOI) and trait-based analysis, we characterized zooplankton diversity and community composition in the upper 1000 m of the northeast Pacific Ocean. We tested whether the North Pacific Transition Zone is a biogeographic boundary region for mesopelagic zooplankton.

Taxonomy and morphology of Calciopappus curvus sp. nov. (Syracosphaeraceae, Prymnesiophyceae), a novel appendage-bearing coccolithophore.

Based on scanning electron microscopy observations, a new species of the coccolithophore genus Calciopappus (Syracosphaeraceae, Prymnesiophyceae) is described from the surface waters off Bergen and from the lower photic zone of sub-tropical and tropical waters. Morphological, coccolith rim structure and biometric analyses strongly support separation of this morphotype from the two described Calciopappus species, but inclusion of it within the genus. The new form differs from the other species in being noticeably smaller and in morpho-structural details of each of the three coccolith types that form the coccosphere: (1) the body coccoliths have an open central area; (2) the whorl coccoliths have a wide central opening and two thumb-like protrusions; and (3) the appendage coccoliths are curved.

Organic and inorganic nutrients modulate taxonomic diversity and trophic strategies of small eukaryotes in oligotrophic oceans.

As the oligotrophic gyres expand due to global warming, exacerbating resource limitation impacts on primary producers, predicting changes to microbial assemblages and productivity requires knowledge of the community response to nutrient availability. This study examines how organic and inorganic nutrients influence the taxonomic and trophic composition (18S metabarcoding) of small eukaryotic plankton communities (< 200 µm) within the euphotic zone of the oligotrophic Sargasso Sea. The study was conducted by means of field sampling of natural microbial communities and laboratory incubation of these communities under different nutrient regimes.

The photic-aphotic divide is a strong ecological and evolutionary force determining the distribution of ciliates (Alveolata, Ciliophora) in the ocean.

The bulk of knowledge on marine ciliates is from shallow and/or sunlit waters. We studied ciliate diversity and distribution across epi- and mesopelagic oceanic waters, using DNA metabarcoding and phylogeny-based metrics. We analyzed sequences of the 18S rRNA gene (V4 region) from 369 samples collected at 12 depths (0-1000 m) at the Bermuda Atlantic Time-series Study site of the Sargasso Sea (North Atlantic) monthly for 3 years.

The crossover from microscopy to genes in marine diversity: from species to assemblages in marine pelagic copepods.

An accurate identification of species and communities is a prerequisite for analysing and recording biodiversity and community shifts. In the context of marine biodiversity conservation and management, this review outlines past, present and forward-looking perspectives on identifying and recording planktonic diversity by illustrating the transition from traditional species identification based on morphological diagnostic characters to full molecular genetic identification of marine assemblages. In this process, the article presents the methodological advancements by discussing progress and critical aspects of the crossover from traditional to novel and future molecular genetic identifications and it outlines the advantages of integrative approaches using the strengths of both morphological and molecular techniques to identify species and assemblages.

Retraction Note: Molecular Phylogeny and Revision of Copepod Orders (Crustacea: Copepoda).

Editor's Note: this Article has been retracted; the Retraction Note is available at https://www.nature.com/articles/s41598-020-72330-x.

Towards population genomics in non-model species with large genomes: a case study of the marine zooplankton .

Advances in next-generation sequencing technologies and the development of genome-reduced representation protocols have opened the way to genome-wide population studies in non-model species. However, species with large genomes remain challenging, hampering the development of genomic resources for a number of taxa including marine arthropods. Here, we developed a genome-reduced representation method for the ecologically important marine copepod (haploid genome size of 6.

Variations in Copepod Proteome and Respiration Rate in Association with Diel Vertical Migration and Circadian Cycle.

The diel vertical migration of zooplankton is a process during which individuals spend the night in surface waters and retreat to depth during the daytime, with substantial implications for carbon transport and the ecology of midwater ecosystems. The physiological consequences of this daily pattern have, however, been poorly studied beyond investigations of speed and the energetic cost of swimming. Many other processes are likely influenced, such as fuel use, energetic trade-offs, underlying diel (circadian) rhythms, and antioxidant responses.

Molecular Phylogeny and Revision of Copepod Orders (Crustacea: Copepoda).

For the first time, the phylogenetic relationships between representatives of all 10 copepod orders have been investigated using 28S and 18S rRNA, Histone H3 protein and COI mtDNA. The monophyly of Copepoda (including Platycopioida Fosshagen, 1985) is demonstrated for the first time using molecular data. Maxillopoda is rejected, as it is a polyphyletic group.

New insights into global biogeography, population structure and natural selection from the genome of the epipelagic copepod Oithona.

In the epipelagic ocean, the genus Oithona is considered as one of the most abundant and widespread copepods and plays an important role in the trophic food web. Despite its ecological importance, little is known about Oithona and cyclopoid copepods genomics. Therefore, we sequenced, assembled and annotated the genome of Oithona nana.

A transcriptomic resource for the northern krill Meganyctiphanes norvegica based on a short-term temperature exposure experiment.

The northern krill, Meganyctiphanes norvegica, is an important component of the pelagic food web across the North Atlantic. Widespread from the Mediterranean to the Subarctic Atlantic, populations appear to be strongly adapted to local temperatures, and seem to have very little plasticity. The goal of this study was to create and annotate a de novo transcriptome assembly to allow for comparative and physiological studies and to explore the gene expression response of M.

Revision of Family Megacalanidae (Copepoda: Calanoida).

The Megacalanidae were revised based on new and archived material. Taxonomic confusion that has existed in the family is discussed and a method is suggested for stabilising names. A detailed examination of the morphology of this family, using the light microscope, has added further useful characters that distinguish genera and species.

Phylogeography and connectivity of the (Copepoda: Calanoida) species complex in the eastern North Pacific and the Pacific Arctic Region.

The genus (Copepoda, Calanoida) is among the most numerically dominant copepods in eastern North Pacific and Pacific-Arctic waters. We compared population connectivity and phylogeography based on DNA sequence variation for a portion of the mitochondrial cytochrome oxidase I gene for four species with differing biogeographical ranges within these ocean regions. Genetic analyses were linked to characterization of biological and physical environmental variables for each sampled region.

DNA barcoding of marine copepods: assessment of analytical approaches to species identification.

More than 2,500 species of copepods (Class Maxillopoda; Subclass Copepoda) occur in the marine planktonic environment. The exceptional morphological conservation of the group, with numerous sibling species groups, makes the identification of species challenging, even for expert taxonomists. Molecular approaches to species identification have allowed rapid detection, discrimination, and identification of species based on DNA sequencing of single specimens and environmental samples.

Phylogeny of the Paracalanidae Giesbrecht, 1888 (Crustacea: Copepoda: Calanoida).

The Paracalanidae are ecologically-important marine planktonic copepods that occur in the epipelagic zone in temperate and tropical waters. They are often the dominant taxon - in terms of biomass and abundance - in continental shelf regions. As primary consumers, they form a vital link in the pelagic food web between primary producers and higher trophic levels.

Reexamination of the species assignment of Diacavolinia pteropods using DNA barcoding.

Thecosome pteropods (Mollusca, Gastropoda) are an ecologically important, diverse, and ubiquitous group of holoplanktonic animals that are the focus of intense research interest due to their external aragonite shell and vulnerability to ocean acidification. Characterizing the response of these animals to low pH and other environmental stressors has been hampered by continued uncertainty in their taxonomic identification. An example of this confusion in species assignment is found in the genus Diacavolinia.

Multi-gene analysis reveals a lack of genetic divergence between Calanus agulhensis and C. sinicus (Copepoda; Calanoida).

The discrimination and taxonomic identification of marine species continues to pose a challenge despite the growing number of diagnostic metrics and approaches. This study examined the genetic relationship between two sibling species of the genus Calanus (Crustacea; Copepoda; Calanidae), C. agulhensis and C.