Search

This study investigates DNA damage and mortality in an Arctic marine copepod after long-term exposure to lowered pH. Acartia longiremis were collected from northern Norway and incubated in ambient pH 8.1, and reduced pH 7.6 and 7.2 over 3-4 weeks. Cumulative mortality was significantly elevated in the lowered pH treatments in all exposures. The fluorescence-based fast micromethod for analysis of DNA strand breaks and alkali-labile sites was modified for use on crustaceous zooplankton. DNA damage initially increased in the lowered pH treatments, decreasing after >14 days, and DNA damage was significantly higher in lowered pH conditions. This method is ideal for investigating oxidative stress and genotoxicity response to low pH in Arctic marine copepods exposed to future ocean acidification conditions.

Microplastics (

In the advective realm of the seas, it is challenging to disentangle the role of regional and local processes on zooplankton populations. However, comparative studies of spatially separated zooplankton populations can provide valuable insights into this issue. We studied interannual abundance variation of the key zooplankton species Calanus finmarchicus and C. hyperboreus in three near-shore locations of the Nordic Seas: off northern Norway, Svalbard, and northern Iceland. Average abundances of both species were similar among locations, while in each location the abundance of C. finmarchicus was about an order of magnitude higher than the abundance of C. hyperboreus. The abundance of both species decreased in northern Norway, while C. finmarchicus abundance increased in northern Iceland. C. finmarchicus abundance in northern Norway covaried with regional climate, while the Svalbard Calanus populations were related to local environment (hydrography, phytoplankton). In northern Iceland, C. finmarchicus abundance covaried with local environmental factors, while C. hyperboreus abundance covaried with climate variability. Top-down forcing could not be investigated. The results indicate that the mechanisms relating regional climate variability (North Atlantic and Arctic oscillations) to Calanus abundance are mediated through advection of water masses, while more local environmental variability involved bottom-up processes or advection.

This is a pre-copyedited, author-produced version of an article accepted for publication in ICES Journal of Marine Science following peer review. The version of record Renaud, P.E., Daase, M., Banas, N.S., Gabrielsen, T.M., Søreide, J.E., Varpe, Ø., ... Berge, J. (2018). Pelagic food-webs in a changing Arctic: a trait-based perspective suggests a mode of resilience. ICES Journal of Marine Science, is available online at: https://doi.org/10.1093/icesjms/fsy063. Arctic marine ecosystems support fisheries of significant and increasing economic and nutritional value. Commercial stocks are sustained by pelagic food webs with relatively few keystone taxa mediating energy transfer to higher trophic levels, and it remains largely unknown how these taxa will be affected by changing climate and the influx of boreal taxa. Calanus species store large quantities of lipids, making these zooplankton a critical link in marine food-webs. The Arctic Calanus species are usually larger and, importantly, have been suggested to contain disproportionately larger lipid stores than their boreal congeners. Continued climate warming and subsequent changes in primary production regimes have been predicted to lead to a shift from the larger, lipid-rich Arctic species, Calanus glacialis and Calanus hyperboreus, toward the smaller, boreal Calanus finmarchicus in the European Arctic, with negative consequences for top predators. Our data show that lipid content is closely related to body size for all three species, i.e. is not a species-specific trait, and that there is considerable overlap in size between C. finmarchicus and C. glacialis. A trait-based life-history model was used to examine an idealized scenario where, in a changed Arctic with a longer period of primary production, C. glacialis- and C. hyperboreus-like copepods are indeed replaced by C. finmarchicus-like individuals, whether through competition, plasticity, hybridization, or evolution. However, the model finds that transfer of energy from primary producers to higher predators may actually be more efficient in this future scenario, because of the changes in generation length and population turnover rate that accompany the body-size shifts. These findings suggest that Arctic marine food webs may be more resilient to climate-related shifts in the Calanus complex than previously assumed.

Microscopic plastic debris, termed “microplastics”, are of increasing environmental concern. Recent studies have demonstrated that a range of zooplankton, including copepods, can ingest microplastics. Copepods are a globally abundant class of zooplankton that form a key trophic link between primary producers and higher trophic marine organisms. Here we demonstrate that ingestion of microplastics can significantly alter the feeding capacity of the pelagic copepod Calanus helgolandicus. Exposed to 20 μm polystyrene beads (75 microplastics mL(–1)) and cultured algae ([250 μg C L(–1)) for 24 h, C. helgolandicus ingested 11% fewer algal cells (P = 0.33) and 40% less carbon biomass (P < 0.01). There was a net downward shift in the mean size of algal prey consumed (P < 0.001), with a 3.6 fold increase in ingestion rate for the smallest size class of algal prey (11.6–12.6 μm), suggestive of postcapture or postingestion rejection. Prolonged exposure to polystyrene microplastics significantly decreased reproductive output, but there were no significant differences in egg production rates, respiration or survival. We constructed a conceptual energetic (carbon) budget showing that microplastic-exposed copepods suffer energetic depletion over time. We conclude that microplastics impede feeding in copepods, which over time could lead to sustained reductions in ingested carbon biomass.

AC is funded by the Ministry of Science and Innovation of Spain through project CTM2009-08783. AM was part funded by NERC UK project NE/K001345/1. KJF was funded by NERC UK through projects NE/H01750X/1 and NE/F003455/1. This review was supported in part by project EURO-BASIN (Ref. 264933, 7FP, European Union), and by a Leverhulme International Network ‘‘Placing marine mixotrophs in context: modelling mixotrophy in a changing world’’., Exploring climate and anthropogenic impacts on marine ecosystems requires an understanding of how trophic components interact. However, integrative end-to-end ecosystem studies (experimental and/or modelling) are rare. Experimental investigations often concentrate on a particular group or individual species within a trophic level, while tropho-dynamic field studies typically employ either a bottom-up approach concentrating on the phytoplankton community or a top-down approach concentrating on the fish community. Likewise the emphasis within modelling studies is usually placed upon phytoplankton- dominated biogeochemistry or on aspects of fisheries regulation. In consequence the roles of zooplankton communities (protists and metazoans) linking phytoplankton and fish communities are typically under-represented if not (especially in fisheries models) ignored. Where represented in ecosystem models, zooplankton are usually incorporated in an extremely simplistic fashion, using empirical descriptions merging various interacting physiological functions governing zooplankton growth and development, and thence ignoring physiological feedback mechanisms. Here we demonstrate, within a modelled plankton food-web system, how trophic dynamics are sensitive to small changes in parameter values describing zooplankton vital rates and thus the importance of using appropriate zooplankton descriptors. Through a comprehensive review, we reveal the mismatch between empirical understanding and modelling activities identifying important issues that warrant further experimental and modelling investigation. These include: food selectivity, kinetics of prey consumption and interactions with assimilation and growth, form of voided material, mortality rates at different age-stages relative to prior nutrient history. In particular there is a need for dynamic data series in which predator and prey of known nutrient history are studied interacting under varied pH and temperature regimes., FP7, MINECO, NERC, Leverhulme International Network, 3,2690

Species of the genus Pseudocalanus (Copepoda: Calanoida) are widespread in the North Atlantic Ocean and provide an opportunity to explore ocean-basin-scale genetic relationships of closely related holozooplanktonic species. A phylogeographic analysis of five species of Pseudocalanus, using two mitochondrial DNA markers and one nuclear DNA marker, was conducted. The results show that there are differences in the overall genetic structure among the five species. Three species, P. minutus, P. moultoni and P. elongatus displayed no or little genetic structuring, while P. acuspes and P. newmani showed comparatively higher genetic structure. These results, combined with tree-based and demographic-history analyses, may indicate that the five copepod species investigated herein could represent two diverging evolutionary branches.

Meroplankton are seasonally important contributors to the zooplankton, particularly at inshore sites, yet their feeding ecology is poorly known relative to holoplankton. While several studies have measured feeding in decapod larvae, few studies have examined the feeding rates of decapod larvae on natural prey assemblages throughout the reproductive season. We conducted 8 feeding experiments with Necora puber, Liocarcinus spp. and Upogebia spp. zoea larvae collected from the L4 monitoring site off Plymouth (50°15.00′N, 4°13.02′W) during spring–summer 2009 and 2010. This period spanned moderate-to-high food availability (0.5–1.6 µg chl-a L−1), but a great range in food composition with small cells

Plastic debris is a widespread contaminant, prevalent in aquatic ecosystems across the globe. Zooplankton readily ingest microscopic plastic (microplastic,1 mm), which are later egested within their faecal pellets. These pellets are a source of food for marine organisms, and contribute to the oceanic vertical flux of particulate organic matter as part of the biological pump. The effects of microplastics on faecal pellet properties are currently unknown. Here we test the hypotheses that (1) faecal pellets are a vector for transport of microplastics, (2) polystyrene microplastics can alter the properties and sinking rates of zooplankton egests and, (3) faecal pellets can facilitate the transfer of plastics to coprophagous biota. Following exposure to 20.6 μm polystyrene microplastics (1000 microplastics mL(-1)) and natural prey (∼1650 algae mL(-1)) the copepod Calanus helgolandicus egested faecal pellets with significantly (P0.001) reduced densities, a 2.25-fold reduction in sinking rates, and a higher propensity for fragmentation. We further show that microplastics, encapsulated within egests of the copepod Centropages typicus, could be transferred to C. helgolandicus via coprophagy. Our results support the proposal that sinking faecal matter represents a mechanism by which floating plastics can be vertically transported away from surface waters.

The genus Pseudocalanus (Copepoda, Calanoida) consists of seven species, all of which are known to co-occur with two or more sibling species in some areas of their geographic ranges. Despite the ecological importance of this abundant genus, there is no available method that can reliably and accurately identify Pseudocalanus species without knowledge of origin. We present evidence of several observations of Pseudocalanus moultoni [Frost (1989) Can. J. Zool., 67, 525–551] in fjords of Svalbard and northern Norway; this species has previously been known to occur only on the east and west coasts of North America. Patterns of DNA sequence variation of the mitochondrial cytochrome oxidase subunit I (COI) gene allow us to confidently identify the species, discriminate it from co-occurring sibling species and infer relationships among the newly discovered and previously sampled P. moultoni populations. Our observations suggest that NE Atlantic populations of P. moultoni are self-sustaining and we discuss potential source populations and pathways of transport. In light of recent reports of climate-driven shifts in distributional ranges of marine zooplankton, accurate species identification is essential for monitoring and understanding marine ecosystems.

DAMIEN ELOIRE1,2*, PAUL J. SOMERFIELD1, DAVID V. P. CONWAY3, CLAUDIA HALSBAND-LENK1, ROGER HARRIS1 AND DELPHINE BONNET2 1 PLYMOUTH MARINE LABORATORY, PROSPECT PLACE, THE HOE, PLYMOUTH, DEVON PL1 3DH, UK, LABORATOIRE ECOSYSTEME LAGUNAIRE, UMR 5119, CNRS – UNIVERSITE MONTPELLIER II – IRD –IFREMER, CC093, PLACE EUGENE BATAILLON, 34095 MONTPELLIER CEDEX 05, FRANCE AND MARINE BIOLOGICAL ASSOCIATION OF THE UNITED KINGDOM, CITADEL HILL, THE HOE, PLYMOUTH, DEVON PL1 2PB, UK

Microplastic litter is a pervasive pollutant present in aquatic systems across the globe. A range of marine organisms have the capacity to ingest microplastics, resulting in adverse health effects. Developing methods to accurately quantify microplastics in productive marine waters and those internalized by marine organisms, is of growing importance. Here we investigate the efficacy of using acid, alkaline and enzymatic digestion techniques in mineralizing biological material from marine surface trawls to reveal any microplastics present. Our optimized enzymatic protocol can digest >97% (by weight) of the material present in plankton-rich seawater samples without destroying any microplastic debris present. In applying the method to replicate marine samples from the western English Channel, we identified 0.27 microplastics m−3. The protocol was further used to extract microplastics ingested by marine zooplankton under laboratory conditions. Our findings illustrate that enzymatic digestion can aid the detection of microplastic debris within seawater samples and marine biota.

The seasonal cycles of reproduction of the dominant copepods Acartia clausi, Temora longicornis, Centropages hamatus, C. typicus and Pseudocalanus spp. were studied at Helgoland Roads, southern North Sea. Egg production rate, clutch size, number of spawning females and pro- some length were compared with temperature and phytoplankton concentration. Female A. clausi, T. longicornis and Pseudocalanus spp. were present all year round. T. longicornis and Pseudocalanus spp. bred continuously throughout the year, although egg production rates and the proportion of spawning females were low in winter. A. clausi did not spawn between the end of September and the end of January. Female C. hamatus were absent from the water column from November to May, and C. typicus from February to August. As the latter 3 species spawn year round in warmer regions, low temperature inhibition of reproduction is suggested for Helgoland, where winter temperatures are below 0°C. Maximum egg production was observed in all species, except the late-arriving C. typicus, in April/May, when females were largest. Significant correlations were only obtained between clutch size or egg production rate and prosome length, which in turn was correlated with temperature. It is therefore concluded that for Helgoland waters temperature controlled egg production by its effect on prosome length, and that food conditions were not limiting.

Small plastic detritus, termed "microplastics", are a widespread and ubiquitous contaminant of marine ecosystems across the globe. Ingestion of microplastics by marine biota, including mussels, worms, fish, and seabirds, has been widely reported, but despite their vital ecological role in marine food-webs, the impact of microplastics on zooplankton remains under-researched. Here, we show that microplastics are ingested by, and may impact upon, zooplankton. We used bioimaging techniques to document ingestion, egestion, and adherence of microplastics in a range of zooplankton common to the northeast Atlantic, and employed feeding rate studies to determine the impact of plastic detritus on algal ingestion rates in copepods. Using fluorescence and coherent anti-Stokes Raman scattering (CARS) microscopy we identified that thirteen zooplankton taxa had the capacity to ingest 1.7-30.6 μm polystyrene beads, with uptake varying by taxa, life-stage and bead-size. Post-ingestion, copepods egested faecal pellets laden with microplastics. We further observed microplastics adhered to the external carapace and appendages of exposed zooplankton. Exposure of the copepod Centropages typicus to natural assemblages of algae with and without microplastics showed that 7.3 μm microplastics (4000 mL(-1)) significantly decreased algal feeding. Our findings imply that marine microplastic debris can negatively impact upon zooplankton function and health.

Carbon capture and storage (CCS) technologies involve localized acidification of significant volumes of seawater, inhabited mainly by planktonic species. Knowledge on potential impacts of these techniques on the survival and physiology of zooplankton, and subsequent consequences for ecosystem health in targeted areas, is scarce. The recent literature has a focus on anthropogenic greenhouse gas emissions into the atmosphere, leading to enhanced absorption of CO2 by the oceans and a lowered seawater pH, termed ocean acidification. These studies explore the effects of changes in seawater chemistry, as predicted by climate models for the end of this century, on marine biota. Early studies have used unrealistically severe CO2/pH values in this context, but are relevant for CCS leakage scenarios. Little studied meso- and bathypelagic species of the deep sea may be especially vulnerable, as well as vertically migrating zooplankton, which require significant residence times at great depths as part of their life cycle.

Marine chemical ecology comprises the study of the production and interaction of bioactive molecules affecting organism behavior and function. Here we focus on bioactive compounds and interactions associated with phytoplankton, particularly bloom-forming diatoms, prymnesiophytes and dinoflagellates. Planktonic bioactive metabolites are structurally and functionally diverse and some may have multiple simultaneous functions including roles in chemical defense (antipredator, allelopathic and antibacterial compounds), and/or cell-to-cell signaling (e. g., polyunsaturated aldehydes (PUAs) of diatoms). Among inducible chemical defenses in response to grazing, there is high species-specific variability in the effects on grazers, ranging from severe physical incapacitation and/or death to no apparent physiological response, depending on predator susceptibility and detoxification capability. Most bioactive compounds are present in very low concentrations, in both the producing organism and the surrounding aqueous medium. Furthermore, bioactivity may be subject to synergistic interactions with other natural and anthropogenic environmental toxicants. Most, if not all phycotoxins are classic secondary metabolites, but many other bioactive metabolites are simple molecules derived from primary metabolism (e. g., PUAs in diatoms, dimethylsulfoniopropionate (DMSP) in prymnesiophytes). Producing cells do not seem to suffer physiological impact due to their synthesis. Functional genome sequence data and gene expression analysis will provide insights into regulatory and metabolic pathways in producer organisms, as well as identification of mechanisms of action in target organisms. Understanding chemical ecological responses to environmental triggers and chemically-mediated species interactions will help define crucial chemical and molecular processes that help maintain biodiversity and ecosystem functionality.

[1] Organic carbon flux and zooplankton carbon consumption rates were measured in the deep water of the eastern Mediterranean. Standardized carbon consumption rates of zooplankton were higher than rates measured in the deep open ocean, probably due to the elevated temperature of ∼14°C in the bathypelagic zone of the eastern Mediterranean. The absolute rates, however, were very low, reflecting the oligotrophic character of the basin. Zooplankton were estimated to consume 23% of the sinking flux between 1050 m and 4250 m. Owing to the high temperature in the Levantine deep-sea, however, the carbon losses from the sinking flux calculated by the Martin equation are probably underestimated, and higher total losses may occur. Lucicutia longiserrata, an intrinsic faunal element in the deep Levantine Sea, played a significant role in carbon recycling. The increased recycling efficiency of pelagic organisms in the bathypelagic zone possibly facilitates starvation of the benthos in the nutrient-poor Levantine Basin.