Calanoid Copepods Research Articles

An accessible method to standardize polyethylene microsphere (

The ubiquity of microplastics has caused alarm as to the impact of these materials on aquatic life, leading to experimental studies to understand these effects. In zooplankton bioassays, microspheres (Ms) are often used as a proxy to represent aquatic microplastic contamination due to their homogeneity and small sizes (<100 μm). The present study proposes an accessible protocol that does not require highly specialized equipment for the creation of Ms stock solutions and environmentally realistic experimental concentrations and describes some common issues. Adult females of the calanoid copepod Centropages furcatus underwent treatments of two Ms sizes at experimental concentrations of 10 Ms/mL. They consumed on average 0.9 ± 2.6 Ms/mL of 45–53 μm Ms, and 2.4 ± 1.1 Ms/mL of 38–45 μm Ms. The results are not directly comparable with other studies due to the wide variety of methods used but successfully demonstrate the reproducibility of the proposed protocol.

Swimming behavior and energy metabolism of the calanoid copepod invader Sinodiaptomus sarsi

The appearance of invasive species threatens the integrity of aquatic ecosystems. Much is known about dispersal and introduction mechanisms while little is known on the biological properties of invasive species, such as behavior and energy efficiency, allowing them to successfully colonize new environments and compete with native species. This study examines the functional features of the Asian invasive copepod Sinodiaptomus sarsi (Rylov, 1923) that has invaded Europe since 2016. We focused on the energy metabolism and kinematic parameters of the main swimming types (i.e., gliding, hovering, small relocation jumps, and the escape reaction) of females and males of S. sarsi. Based on the above parameters, the mechanical energy for swimming and the respiration energy needed for movement were calculated. Females and males spend up to 95% of time hovering and slowly gliding at a speed of up to 0.5 cm s−1. During the remaining time, the average swimming speed was 8 cm s−1 by small jumps. In contrast, the average speed was 42 cm s−1 during escape swimming. Non-ovigerous females moved faster than ovigerous females during all relocation swimming types except for upward gliding. While performing small jumps with a frequency of 0.79 Hz, the respiration rate of active non-ovigerous females (0.32 ± 0.03 µg O2 ind−1 h−1) was 2.1 times higher than that of anesthetized individuals. The respiration energy associated with movement was 2.6 * 10−3 J h−1, while the total mechanical energy was only 4.2% of this value. The low energy cost of feeding along with the high speed of locomotion may explain the success of this Asian invader in European waters.

Daily vertical distribution and diet of Cyclothone braueri (Gonostomatidae) in the Polcevera submarine canyon (Ligurian Sea, north-western Mediterranean)

Despite its abundance, the role of Cyclothone braueri in intermediate mesopelagic food webs has been poorly investigated, notably its trophic behaviour in areas characterized by peculiar oceanographic and ecological features, such as submarine canyons. In this study, we investigated the diel feeding pattern of C. braueri in the Polcevera submarine canyon, in the Ligurian Sea. Stratified sampling from the surface to 1300 m was undertaken with a BIONESS every 6 h during a 24 h period. Stomach contents of 244 C. braueri specimens from 11.6 to 27.5 mm SL were examined. Calanoid copepods were the dominant taxa in the fish stomachs (98% of all copepods), with Pleuromamma abdominalis, Neocalanus gracilis, Pleuromamma gracilis and Euchaeta acuta being the main preys. Among the 20 identified copepod prey species, about 20% were typical of the epipelagic zone, while the remaining 80% usually live in mesopelagic waters. The low number of prey per stomach (average = 1.4) and high vacuity index (53%) indicated that this species had very low metabolic requirements (trophic level in this study was 3.03). Most of the full stomachs were found during the morning and afternoon in the upper mesopelagic zone (200–400 m), indicating two main periods of feeding activity per day. This study confirmed high abundance and biomass of C. braueri in Polcevera canyon compared to those of open ocean waters and raised the question of how the presence of the canyon affects migratory and trophic behaviours of this mesopelagic fish. Further analyses aimed at investigating the link between the hydrodynamic regime of the Polcevera canyon and the behaviour and trophic ecology of C. braueri are needed to address this question.

Environmental DNA reveals spatial patterns of fish and plankton diversity at a floating offshore wind farm

AbstractIn this study, we collected water eDNA from sampling stations at the first full scale floating offshore wind farm (OWF), the Hywind Pilot Park, east of Peterhead, UK, and a nearby reference area. We combined targeted droplet digital PCR (ddPCR) quantification of two commercially important species, Atlantic mackerel (Scombrus scombrus) and Atlantic herring (Clupea harengus), with metabarcoding of fish and plankton communities. The goal of this study was to assess the performance of eDNA data to characterize pelagic communities and its use for environmental monitoring. The metabarcoding recovered 26 fish species including both pelagic and demersal taxa. The plankton data were dominated by dinoflagellates (Karenia) and calanoid copepods. We found that both specific quantification of eDNA from mackerel and herring and eDNA metabarcoding of fish communities were able to reveal spatial patterns: Mackerel was most abundant in the surface across both OWF and reference sites; herring was present at a wider depth range. While ddPCR and metabarcoding data for these two species were broadly congruent, we observed detection/non‐detection mismatches for both methods, highlighting the need for robust sampling design. There was no consistent OWF versus reference area pattern in the demersal fraction of fish assemblages. We interpret our findings as representing a snapshot of fish school location around the time of sampling, and do not consider the single timepoint data from this pilot study to be sufficient to attribute any effects to the OWF itself. As a non‐invasive tool, we conclude that eDNA has a high potential in future environmental monitoring of OWFs. We recommend further ground‐truthing and biomass correlation of eDNA data with catch data and establishing eDNA time series as next steps towards implementation of eDNA in OWF environmental monitoring.

Persistent effects of historical sea levels on the population structure of a temporary wetland copepod

Abstract Temporary wetland ecosystems are common in arid and semi‐arid environments, and are inhabited by diverse invertebrate communities. Little is known about the dynamics of genetic connectivity in the geographically scattered populations of these wetland specialists. The current study investigated the spatial genetic structure and dispersal history of a recently described calanoid copepod, Lovenula raynerae, reported from temporary wetlands in the Eastern Cape province of South Africa. We tested whether the species represents a single, well‐connected population or comprises different regional genetic groups, some of which may be rare or endangered. Mitochondrial COI sequences were generated for 365 specimens from 46 temporary wetlands spread across the species' known distribution range. Isolation‐by‐distance and isolation‐by‐environment patterns of partitioning genetic variations across the landscape were evaluated. In addition, the presence of historical impediments to gene flow between contemporary populations was investigated using a combination of Monmonier's algorithm and Bayesian reconstruction of phylogeographical diffusion in continuous space. The wetland populations were highly structured across the landscape and could be assigned to six distinct evolutionary lineages, potentially representing some level of cryptic speciation. Two distinct phases were identified in the dispersal history of these lineages. Initially, dispersal only occurred inland of a postulated barrier, but eventually the barrier disappeared and the species extended its range by spreading into regions close to the coastline. Molecular dating shows that the barrier represents the upper limit of the coastline during the Pliocene, and that its crossing was facilitated by Pliocene sea regression in southern Africa. Our finding shows that complex demographic histories can be preserved in the mitochondrial DNA of temporary wetland crustaceans because of limited effective gene flow after initial colonisation events. This makes them an interesting study system to explore the long‐term effects of climate change on arid ecosystem communities.

The Reproductive Capacities of the Calanoid Copepods Parvocalanus crassirostis and Acartia pacifica under Different pH and Temperature Conditions.

The increasing atmospheric CO2 concentrations and warming of marine waters have encouraged experiments on multi-stressor interactions in marine organisms. We conducted a multigenerational experiment to assess reproductive capacities regarding egg production in calanoid copepods Parvocalanus crassirostis and Acartia pacifica under different pH and temperature conditions. The experimental set-up allowed assessing the tandem effect of warming and acidification on the number of eggs produced by healthy copepod pairs under two pH conditions of 8.20 and 7.50 (hard selection) as well as with a gradual reduction of 0.05 pH units at each generation (soft selection). The results are quite interesting, with very diverse performance across temperatures. The number of eggs produced under hard selection was higher at pH 8.20 compared to pH 7.50 for both species, with the maximum number of eggs produced at 24-28 °C, whereas under soft selection, there was no significant difference in the egg production rate at 24-28 °C across generations and there was an improvement in the number of eggs produced at 8-16 °C. The results provide evidence that in a future ocean scenario of lower pH and higher temperature, the two species, and possibly the copepod population at large, might not decrease. Copepod populations might be resilient, and the transcriptomic evidence of adaptation to increased temperature and lower pH is a ray of hope. We believe further studies are needed to provide more robust datasets to underpin the hypothesis of adaptation to climate change.

Links between the timing of life history transitions and dietary and morphological variation during early life history in the sand goby, Pomatoschistus minutus.

Bipartite life histories involve a suite of morphological changes that support the pelagic to demersal transition and an expanded range of prey options and microhabitats. Pelagic individuals are thought to shift (settle) to their preferred benthic habitat at the earliest opportunity, once having attained a minimum level of morphological competency to access their new environment. In theory, early changes in larval morphology (collectively termed 'metamorphosis'), habitat, and diet - a measure of habitat-use - ought to be synchronous. Yet relationships may be decoupled by factors linked to behaviour, prey availability or morphological complexity, and few descriptions exist to allow such synchrony to be assessed. The sand goby, Pomatoschistus minutus, is a common coastal fish across north-western Europe, with a size at larval metamorphosis and settlement of around 10 and 16-18 mm SL, respectively. We sampled shoreline larval and juvenile populations to examine relationships between morphology, diet, and life stage. Prey diversity increased with body length. However, dietary change was clearest at 16-18 mm SL, with a reduction in calanoid copepods and shift to larger prey such as Nereis polychaetes and mysid and amphipod crustacea. Early growth in five prey capture and processing morphologies was rapid. Four of these showed a subsequent marked shift to slower growth, but none of these changes were aligned with size at metamorphosis and only that of mouth width coincided with the body size at settlement. Early life history in P. minutus appears geared towards a protracted morphological reorganisation prior to demersal life and an alternative suite of prey resources. Larval metamorphosis seems to be of limited consequence in this regard. Comparable studies of other Baltic Sea fishes would confirm whether these dynamics relate to shared environmental pressures or to factors intrinsic to P. minutus biology. This article is protected by copyright. All rights reserved.

New Benthopelagic Calanoids (Copepoda: Clausocalanoidea) of the deep Japan Sea

Two new species of benthopelagic calanoid copepod Bradfordian genera Pseudophaenna japonica sp. nov. and Xantharus dubius sp. nov. are described from collections of the Russian-German deep-sea expedition (SoJaBio) to the Sea of Japan onboard of the R/V Akademik Lavrentyev, 51st cruise taken close to the sea bed. The rare calanoid copepod genera Pseudophaenna Sars, 1902 and Xantharus Andronov, 1981 and a rare aetideid species Bradyidius rakuma (Zvereva, 1977) are recorded for the first time from the Japan Sea; the male of B. rakuma is described for the first time. Pseudophaenna japonica sp. nov. is the second species described for the genus Pseudophaenna and is distinguished by biramous rostrum, antennule ancestral segment XXII without seta, details of oral parts setation in females and in P5 structure in dimorphic males. Xantharus dubius sp. nov. is described from males and is distinguished from congeners in the antennule ancestral segments XXII and XXIII not comparatively small relative to the segment XXI and in the large and robust uniramous P5. In the collections of the expedition SoJaBio in 2010 from the Japan Sea the near-bottom benthopelgic fauna of Calanoida have been represented by these species only and they all belong to the calanoid superfamily Clausocalanoidea.

Decadal decline of dominant copepod species in the North Sea is associated with ocean warming: Importance of marine heatwaves

Time-series are crucial to understand the status of zooplankton communities and to anticipate changes that might affect the entire food web. Long-term time series allow us to understand impacts of multiple environmental and anthropogenic stressors, such as chemical pollution and ocean warming, on the marine ecosystems. Here, a recent time series (2018–2022) of abundance data of four dominant calanoid and one harpacticoid copepod species from the Belgian Part of the North Sea was combined with previously collected (2009–2010, 2015–2016) datasets for the same study area. The time series reveals a significant decrease (up to two orders of magnitude) in calanoid copepod abundance (Temora longicornis, Acartia clausi, Centropages spp., Calanus helgolandicus), while this was not the case for the harpacticoid Euterpina acutifrons. We applied generalized additive models to quantify the relative contribution of temperature, nutrients, salinity, primary production, turbidity and pollution (anthropogenic chemicals, i.e., polychlorinated biphenyls and polycyclic aromatic hydrocarbons) to the population dynamics of these species. Temperature, turbidity and chlorophyll a concentrations were the only variables consistently showing a relative high contribution in all models predicting the abundances of the selected species. The observed heat waves which occurred during the summer periods of the investigated years coincided with population collapses (versus population densities in non-heatwave years) and are considered the most likely cause for the observed copepod abundance decreases. Moreover, the recorded water temperatures during these heatwaves correspond to the physiological thermal limit of some of the studied species. As far as we know, this is the first study to observe ocean warming and marine heat waves having such a dramatic impact (population collapse) on the dominant zooplankton species in shallow coastal areas.

EDNA metabarcoding vs metagenomics: an assessment of dietary competition in two estuarine pipefishes

Understanding the dietary preferences of endangered species can be useful in implementing conservation strategies, including habitat restoration, translocation, and captive breeding. Environmental DNA (eDNA) from feces provides a non-invasive method for analysing animal diets. Currently, metabarcoding, a PCR-based approach, is the method of choice for analysing such data. However, this method has limitations, specifically PCR bias, which can result in the overestimation of the importance of certain taxa and failure to detect other taxa because they do not amplify. The present study compared metabarcoding with metagenomics, a PCR-free method, to assess the diversity of prey items in the feces of a critically endangered South African estuarine pipefish, Syngnathus watermeyeri, and its widely distributed congener S. temminckii to investigate potential dietary competition. The metabarcoding results showed a distinct difference between the diets of S. watermeyeri and S. temminckii, with the former mainly consuming calanoid copepods and the latter preferring caridean shrimp. In each case, a single species dominated the sequences generated by metabarcoding. Metagenomics produced more species identifications, and although the same trend was found regarding the preference of S. watermeyeri for copepods and that of S. temminckii for shrimp, this approach identified additional, albeit yet unidentified, copepod species as being important in the diet of S. watermeyeri. We conclude that the lower number of species identified using metabarcoding was most likely a result of amplification bias, resulting in key copepod species missing from the dietary analysis. These findings suggest that metagenomics is not only a useful complementary method for molecular dietary analysis, but may in some cases outperform metabarcoding. However, metagenomics is even more strongly affected by the lack of reference sequences than is metabarcoding, as the majority of sequences originate from genomic regions that have not yet been sequenced for the putative prey species in question.

Temperature as main driver of the growth of an endemic Philippine freshwater copepod (Copepoda: Calanoida: Diaptomidae)

Abstract We conducted a preliminary analysis on the effects of various physical and chemical parameters on the morphometry and reproductive capacity of the calanoid copepod Filipinodiaptomus insulanus (Wright, 1928), endemic to the Philippines, by proxying clutch size (CS). Specimens and water quality readings were obtained between October 2019 and February 2020 from four sites in northern Philippines. Only the sizes of adult males and non-ovigerous adult females showed significant differences (P &amp;lt; 0.05) among populations. Non-eutrophic, temporary shallow waters were the predominant habitat type of F. insulanus, corroborating earlier observations that it is mainly found in relatively pristine environments. Correlation analysis showed a significant indirect relationship (P &amp;lt; 0.001) between the size of individuals and temperature, a potential adaptive response to its environment. Such observations may be valuable in preventing the disappearance of this species from parts of its previously known range.

Recent Changes in Composition and Distribution Patterns of Summer Mesozooplankton off the Western Antarctic Peninsula

The Southern Ocean has undergone significant climate-related changes in recent decades. As a result, pelagic communities inhabiting these waters, particularly mesozooplankton, have adapted to new conditions. The present study considers the patterns of horizontal and vertical (up to 1000 m) distribution, the composition, abundance, and biomass of mesozooplankton, and the relationships of these parameters to the extreme environmental conditions off the western Antarctic Peninsula throughout the record-warm austral summer season of 2022. Sampling was conducted using the opening/closing Multinet system (0.25 m2 aperture) equipped with five 150-μm mesh nets and a WP-2 net. The mesozooplankton was represented by the three most abundant groups: eggs and larvae of euphausiids such as Euphausia superba, small copepods such as Oithona similis, and large calanoid copepods such as Calanoides acutus, Calanus propinquus, Metridia gerlachei, and Rhincalanus gigas. The composition and quantitative distribution of the mesozooplankton significantly varied: the copepods were abundant in the west, off the Antarctic Peninsula, while eggs and larvae of euphausiids were abundant in the east, off the South Orkney Islands. Most mesozooplankton occurred in the upper 200 m layer, and each taxon showed characteristic depth preference: small copepods, euphausiids larvae, and cirripeds cypris larvae were abundant in the epipelagic layer, while large calanoid copepods, euphausiids eggs, amphipods, pelagic polychaetes, and ostracods were found mostly in the mesopelagic layer. The composition and quantitative distribution of mesozooplankton had clear relationships with environmental factors, particularly with a combination of variables such as water salinity, temperature, and chlorophyll a concentration.

Molecular characterization of the nearly complete nuclear ribosomal DNA sequence of the Neotropical freshwater copepod Arctodiaptomus dorsalis (Marsh, 1907) (Copepoda, Calanoida, Diaptomidae)

Abstract Arctodiaptomus dorsalis has been reported in the Philippines as an invasive species, which originated from Central America. Apart from its wide distribution in the United States and Central America, it is now widely distributed in many lakes in the Philippine islands, such as Luzon Island and southwestern Mindanao, making it an ideal specimen for studies on population dynamics and population genetics. Recently, new techniques have been emerging as important zooplankton monitoring tools, such as metabarcoding and the use of environmental DNA/environmental RNA. However, these would only be useful if good-quality reference DNA sequences are available before utilizing these techniques. This study sequenced the nearly complete nuclear ribosomal DNA (nrDNA) of A. dorsalis from 202 individuals from Lake Taal, Batangas. The total length was 5887 bp, which includes the partial 18S sequences, and the complete 5.8S, ITS and 28S sequences with an organization that is typical for any eukaryotic organism. This is the first record of a nearly complete nrDNA sequence for freshwater calanoid copepods and is considered an important stepping stone for further molecular studies in freshwater Copepoda.

Growth and diet of a larval myctophid across distinct upwelling regimes in the California Current

Abstract Eastern boundary systems support major fisheries of species whose early stages depend on upwelling production. However, upwelling can be highly variable at the regional scale, leading to complex patterns of feeding, growth, and survival for taxa that are broadly distributed in space and time. The northern California Current (NCC) is characterized by latitudinal variability in the seasonality and intensity of coastal upwelling. We examined the diet and larval growth of a dominant myctophid (Stenobrachius leucopsarus) in the context of their prey and predators in distinct NCC upwelling regimes. Larvae exhibited significant differences in diet and growth, with greater seasonal than latitudinal variability. In winter, during reduced upwelling, growth was substantially slower, guts less full, and diets dominated by copepod nauplii. During summer upwelling, faster-growing larvae had guts that were more full from feeding on calanoid copepods and relying less heavily on lower trophic level prey. Yet, our findings revealed a dome-shaped relationship with the fastest growth occurring at moderate upwelling intensity. High zooplanktivorous predation pressure led to above average growth, which may indicate the selective loss of slower-growing larvae. Our results suggest that species whose spatio-temporal distributions encompass multiple regional upwelling regimes experience unique feeding and predation environments throughout their range with implications for larval survivorship.

Opening the black box of winter: Full‐year dynamics of crustacean zooplankton along a nearshore depth gradient in a large lake

AbstractPast studies of zooplankton seasonality in large temperate lakes have often neglected the winter period. Winter conditions are rapidly changing (e.g., reduced ice cover extent and duration, altered thermal and mixing regimes) in northern lakes, making it important to fill the existing winter knowledge gap. In this study, we sampled five stations in Lake Superior across a nearshore depth gradient through the full year to assess the phenology of crustacean zooplankton communities and the effect of environmental drivers on them. Across stations, zooplankton densities were the lowest in winter (0.9 ± 0.6 Ind. L−1) and highest in summer (14.2 ± 15.1 Ind. L−1). Zooplankton abundances and community composition were less seasonally variable at deeper stations compared to shallower and more terrestrially affected regions. Cladocerans were the dominant taxonomic group during the summer across all stations, while cyclopoid and calanoid copepods were more important during the fall, winter, and spring. Among feeding groups, herbivores were most abundant in summer while omnivores and carnivores dominated in winter. We found that water temperature and food availability were the main drivers of total zooplankton densities through the year and during the cold seasons, but the effect of these factors varied among the main taxonomic groups. Our study demonstrates seasonal and spatial variation in crustacean zooplankton and environmental parameters, with the highest fluctuation at shallower stations. This study offers new information on seasonal crustacean zooplankton dynamics and contributes to understanding the effects of climate change on large lake ecosystems.

Cumulative reproduction model to quantify the production of the invasive species Arctodiaptomus dorsalis (Calanoida, Copepoda)

Arctodiaptomus dorsalis is an invasive calanoid copepod originally from America and has recently established a population in Lake Taal in the Philippines. It has been proposed that eutrophication due to aquaculture contributes to the establishment and success of this species. This study aimed to clarify this hypothesis by quantifying the effect of increasing food concentration on the reproduction of A. dorsalis using an Individual-Based Model. We parameterized food concentration-dependent equations to simulate the effect of different food concentration on the reproductive traits (latency time, embryonic development time, clutch size, and hatching success) of this species using data from the literature and simulated the reproduction of 1000 independent females for 20 days at different food concentration, taking into account the variability among individuals. The simulation results showed that the cumulative production of eggs and offspring increased continuously with time when the food concentration was above 3.2 × 104 cells mL−1, suggesting that this value was the threshold concentration required for stable reproduction of A. dorsalis. This value is not particularly low compared to other copepods. Hence, our result revealed that the food use efficiency of A. dorsalis is not particularly outstanding and urge the need of a comparison with native species to confirm a possible superiority. We suggest that A. dorsalis has filled the ecological niche left vacant by the disappearance of the original species due to the deterioration of water quality caused by the eutrophication of the lake. The reproductive cycle model developed in this study constitutes a necessary step in the development of a complete population dynamics model, which can help clarify the invasive abilities of A. dorsalis.

De novo transcriptomes of six calanoid copepods (Crustacea): a resource for the discovery of novel genes

This study presents eight new high-quality de novo transcriptomes from six co-occurring species of calanoid copepods, the first published for Neocalanus plumchrus, N. cristatus, Eucalanus bungii and Metridia pacifica and additional ones for N. flemingeri and Calanus marshallae. They are ecologically-important members of sub-arctic North Pacific marine zooplankton communities. ‘Omics data for this diverse and numerous taxonomic group are sparse and difficult to obtain. Total RNA from single individuals was used to construct gene libraries that were sequenced on an Illumina Next-Seq platform. Quality filtered reads were assembled with Trinity software and validated using multiple criteria. The study’s primary purpose is to provide a resource for gene expression studies. The integrated database can be used for quantitative inter- and intra-species comparisons of gene expression patterns across biological processes. An example of an additional use is provided for discovering novel and evolutionarily-significant proteins within the Calanoida. A workflow was designed to find and characterize unannotated transcripts with homologies across de novo assemblies that have also been shown to be eco-responsive.

Assessing key influences on the distribution and life-history of Arctic and boreal Calanus: are online databases up to the challenge?

Despite the importance of calanoid copepods to healthy ecosystem functioning of the Arctic Ocean and Subarctic Seas, many aspects of their biogeography, particularly in winter months, remain unresolved. At the same time, online databases that digitize species distribution records are growing in popularity as a tool to investigate ecological patterns at macro scales. The value of such databases for Calanus research requires investigation - the long history of Calanus sampling holds promise for such databases, while conditions at high latitudes may impose limits through spatial and temporal biases. We collated records of three Calanus species (C. finmarchicus, C. glacialis, and C. hyperboreus) from the Ocean Biodiversity Information System (OBIS) and the Global Biodiversity Information Facility (GBIF) providing over 230,000 unique records spanning 150 years and over 100 individual datasets. After quality control and cleaning, the latitudinal and vertical distribution of occurrences were explored, as well as the completeness of informative metadata fields. Calanus sampling was found to be temporally and spatially biased towards surfacemost layers (&amp;lt;10m) in spring and summer. Only 3.5% of records had an average collection depth ≥400m, approximately half of these in months important for diapause. Just over 40% of records lacked associated information on sampling protocol while 11% of records lacked life-stage information. OBIS data contained fields for maximum and minimum collection depth and so were subset into discrete “shallow summer” and “deep winter” life cycle phases and matched to sea-ice and temperature conditions. 23% of OBIS records north of 66° latitude were located in regions of seasonal sea-ice presence and occurrences show species-specific thermal optima during the shallow summer period. The collection depth of C. finmarchicus was significantly different to C. hyperboreus during the deep winter. Overall, online databases contain a vast number of Calanus records but sampling biases should be acknowledged when they are used to investigate patterns of biogeography. We advocate efforts to integrate additional data sources within online portals. Particular gaps to be filled by existing or future collections are (i) widening the spatial extent of sampling during spring/summer months, (ii) increasing the frequency of sampling during winter, particularly at depths below 400m, and (iii) improving the quality, quantity and consistency of metadata reporting.

A review of zooplankton research in Chile

This study is a review of literature records on diversity, distribution and ecology of the Chilean inland water zooplankton including microcrustaceans (Copepoda, Branchiopoda), rotifera (Bdelloida and Monogononta) and ciliated protozoa. For that, several databases were consulted, and about 239 records were analysed and evaluated. The results revealed that in total about 109 water bodies have been sampled in Chile. Crustacea are well studied in the entire Chilean territory, whereas records on Rotifera and Ciliata are more restricted to the Central and Southern zones. Within Crustacea calanoid copepods of the genus Boeckella and to lower degree Cladocera (Branchiopoda) predominate. Anostraca are reported for hypersaline waterbodies and ephemeral pools, whereas Laevicaudata and Spinicaudata (Branchiopoda) are only found in shallow ephemeral pools. Regarding rotifers, 121 species were identified, whereas 46 species of ciliated protozoa were registered in lentic water bodies of the Southern zone. Ecological studies included different aspects as population dynamics, vertical migration, diapause, role of ultraviolet radiation among others. We discuss also shortcomings and future studies. Future studies should consider more in detail population dynamics, molecular topics to better assess taxonomical determinations, trophic interactions within the food webs and effects of global changes at population and community level.

Spatial variation of summer microphytoplankton and zooplankton communities related to environmental parameters in the coastal area of Djerba Island (Tunisia, Eastern Mediterranean)

In the present study, we investigated the effects of pollution and anthropization on the summer distribution of phyto-zooplanktoncommunities in relation to environmental factors in the coastal zone of DjerbaIsland. On the basis of chemical factors, theDjerba coasts can be divided into two parts: the Western Area (WA), characterized by high values of nitrogen forms of nutrients,with higher N/P ratio, and the Eastern Area (EA), poorer in inorganic nitrogen with an N/P ratio lower than the Redfield ratio (16).Strong differences in terms of plankton communities were also observed between these two areas. Bacillariophyceae was the most important microphytoplankton group in the WA whereas the proportion of Cyanobacteria was higher in the EA. High Cyanobacteria abundance in the EA may be linked to high DIP concentration. In the WA, the Bacillariophyceae Chaetoceros, Coscinodiscus, Grammatophora, Navicula and Pinnularia reached high abundance in relation with their good adaptability to adverse conditions. Copepods were the most abundant zooplankton present in the WA (54–100% of total zooplankton abundance), whereas other zooplankton were always dominant (60–90%) in the EA. The small pollution-tolerant Calanoid copepod Paracalanus parvus was dominant in the WA, illustrating its affinity for highly eutrophic sites. Despite human pressure and industrial activities, the coastal waters of Djerba showed a wide diversity of microphytoplankton and zooplankton.