Acartia Clausi Research Articles

The Spatial Distribution of Copepod Functional Traits in a Highly Anthropized Mediterranean Coastal Marine Region

Copepods dominate marine zooplankton in abundance and play key roles in pelagic food webs. These small crustaceans show high taxonomic and functional diversity. Although there has been considerable research on their taxonomy, only a few studies have focused on their functional traits. In this study, we analyzed the functional traits of 95 copepod species, considering their body size, trophic regime, feeding behavior, and spawning strategy. Based on samples collected during two surveys (autumn 2020 and summer 2021) located in the coastal waters of three gulfs (Gaeta, Naples, and Salerno) in the highly populated Campania region (the central Tyrrhenian Sea, NW Mediterranean), we identified nine functional groups of copepods with different characteristics. The group that comprised herbivorous copepods with feeding currents and a broadcast strategy was the most abundant in both seasons and all gulfs. This group was dominated by Acartia clausi, Centropages typicus, Temora stylifera, and the Paracalanus parvus complex. The other functional groups showed differences in their temporal and spatial distribution. Our study reports the functional diversity of copepods along the Campania coast, thus contributing to advancing our knowledge of the planktonic trophic structure in a region of considerable importance due to its marine resources and services.

Relationship Between Environmental Parameters and Manta Ray Occurrence in Raja Ampat Archipelago, Indonesia

Understanding the influence and impact of environmental factors on manta ray sightings is critical to understanding the spatial and temporal ecology of a highly mobile species. Therefore, this study aims to determine the influence and impact of environmental factors as indicated by the parameters of wind speed, chlorophyll-a, SST, salinity, pH, dissolved oxygen, and the number of phytoplankton and zooplankton species. The mapped chlorophyll-a was re-analyzed based on the seasonal period throughout 2021 downloaded from marine copernicus and analyzed by kriging method. The influence and effects of environmental parameters on the short-term appearance of eye rays were studied using an adaptive model (GAM). The analysis showed a significant influence of environmental factors on manta ray sightings in Raja Ampat, namely Calanoid spp, Oithona nana, Acartia clausi, Calanus helgoladicus, and Oithona brevicornis. Based on this model, zooplankton is an important parameter that can describe the influence of environmental parameters on manta ray sightings at observation points in Raja Ampat MPA. The results of the reanalysis of chlorophyll-a concentrations were highest in the eastern to transitional seasons, which were scattered on the west side of Raja Ampat waters. Meanwhile, chlorophyll-a concentrations were low in the west to transitional season on the east side. This mechanism may drive the foraging strategy of manta rays, which visit shallow waters where zooplankton density and biomass are abundant. Adopting the BHS MPA network concept, as it has been implemented, would be in line with broader conservation expectations for the sustainability of manta rays in Raja Ampat.

Decadal Trends in the Zooplankton Community of the Western Mediterranean

Decadal trends in the zooplankton community were seasonally investigated in multiple monitoring transects of the western Mediterranean Sea during a period of increasing and record-high water temperatures. The transition area around the Baleares archipelago can be separated into two regions: the Alborán Sea and the Balearic Sea. Differences were found in the abundance and structure of the dominant zooplankton groups: the cladocerans and copepods. The highest zooplankton abundances were found during the stratified summer season, when cladoceran numbers peaked. However, copepods were more abundant during the winter. A marked seasonality was found in all groups and the dominant taxa: 114 species of copepods and 5 species of cladocerans were identified, but less than 8 species of copepods and 2 species of cladocerans dominated the populations. During the 2007–2017 study, warm and salty waters were observed in the Balearic Sea. In the Alborán Sea, cool and fresh waters were observed, along with a decline in chlorophyll. Irregular group and species trends were observed in both regions, exhibiting both increases and decreases depending on region and season. Trends differed, often oppositely, for the Alborán versus the Balearic Sea, with the transition region between them mirroring one or the other, switching with the seasons. The most dominant species, including Penilia avirostris and Clausocalanus arcuicornis, but also Evadne spinifera, C. lividus, C. furcatus, Paracalanus parvus, Acartia clausi, Centropages typicus, Subeucalanus monachus, and Calanus helgolandicus, are proposed as biological tracers to be used in further studies on climate and zooplankton community changes in the western Mediterranean Sea.

Variations in copepod composition and diversity in relation to eutrophication and hydrology in İzmir Bay, Aegean Sea

Hyrographic and trophic gradient along Izmir Bay used to assess their effects on the copepod composition and diversity. Trophic state of the bay varied from oligotrophic in the outer region to hypertrophic condition in the inner region as stated by trophic index (TRIX). Aegean Sea water entrance and trophic conditions of the bay affected species assemblages. Oithona davisae, Oithona nana and Acartia clausi were associated with hyper-eutrophic conditions whereas the typical Aegean Sea species, such as Oncaea media group, Oithona similis, Paracalanus parvus, A. clausi, Farranula rostrata and Calocalanus styliremis were related to oligotrophic condition. Copepod diversity indices decreased linearly along the trophic gradient, from oligotrophic to hyper-eutrophic conditions, highlighting the substantial impact of eutrophication on the copepod community structure in the inner region. These findings emphasize TRIX's value in assessing eutrophication in anthropized systems, and immense potential for using copepod composition and diversity in monitoring programs for ecological assessments studies.

Transcriptomic analysis reveals responses to a polluted sediment in the Mediterranean copepod Acartia clausi

Marine sediments are regarded as sinks for several classes of contaminants. Characterization and effects of sediments on marine biota now require a multidisciplinary approach, which includes chemical and ecotoxicological analyses and molecular biomarkers. Here, a gene expression study was performed to measure the response of adult females of the Mediterranean copepod Acartia clausi to elutriates of polluted sediments (containing high concentrations of polycyclic aromatic hydrocarbons, PAHs, and heavy metals) from an industrial area in the Southern Tyrrhenian Sea (Bagnoli-Coroglio).Functional annotation of the A. clausi transcriptome generated as reference here, showed a good quality of the assembly and great homology with other copepod and crustacean sequences in public databases. This is one of the few available transcriptomic resources for this widespread copepod species of great ecological relevance in temperate coastal areas. Differential expression analysis between females exposed to the elutriate and those in control seawater identified 1000 differentially expressed genes, of which 743 up- and 257 down-regulated. Within the up-regulated genes, the most represented functions were related to proteolysis (lysosomal protease, peptidase, cathepsin), response to stress and detoxification (heat-shock protein, superoxide dismutase, glutathione-S-transferase, cytochrome P450), and cytoskeleton structure (α- and β-tubulin). Down-regulated genes were mostly involved with ribosome structure (ribosomal proteins) and DNA binding (histone proteins, transcription factors). Overall, these results suggest that processes such as transcription, translation, protein degradation, metabolism of biomolecules, reproduction, and xenobiotic detoxification were altered in the copepod in response to polluted elutriates. In conclusion, our results contribute to gaining information on the transcriptomic responses of copepods to polluted sediments. They will also prompt the selection of genes of interest to be used as biomarkers of exposure to PAHs and heavy metals in molecular toxicology studies on copepods, and in general, in comparative functional genomic studies on marine zooplankton.

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.

Reduced Survival and Disruption of Female Reproductive Output in Two Copepod Species (Acartia clausi and A. tonsa) Exposed to the Model Endocrine Disruptor 17α-Ethinylestradiol.

Estuaries are heavily impacted by pollutants from different sources such as urban sewage, industrial waste and agricultural runoff. Endocrine-disrupting chemicals (EDCs) are very concerning pollutants to estuarine wildlife, but little is known about their impact on microscopic biota such as zooplankton. The aim of this work was to investigate the effects of a model EDC, the 17α-ethinylestradiol (EE2), on two copepod species inhabiting the Basque coast (Southeastern Bay of Biscay) estuaries: Acartia clausi (autochthonous neritic species) and Acartia tonsa (non-indigenous brackish species). Female copepods were collected at population maximum time (spring for A. clausi and summer for A. tonsa) and exposed individually to 5 ng/L (low), 5 µg/L (medium) and 500 µg/L EE2 (high) doses, from environmental concentrations found in sewage effluents to toxicological concentrations. After 24 h exposure, the survival rate of experimental individuals was checked and the lethal concentration LC50 was calculated. The number of egg-producing females and the amount of egg laying and egg hatching were recorded. The integrated biomarker index (IBR) was calculated to integrate the overall effects of EE2 exposure. Both species had reduced survival rates at 500 µg/L, and the LC50 was lower in A. tonsa (158 µg/L) compared to A. clausi (398 µg/L). The number of eggs laid was significantly reduced in A. clausi at EE2 medium and high doses, while a reduction in the number of eggs in A. tonsa was observed only at the high dose. However, no significant differences were detected in the egg hatching success of exposed A. clausi and A. tonsa. IBR index showed that EE2 had the most detrimental effects on A. tonsa and A. clausi females at the 500 µg/L dose. In conclusion, after 24 h of exposure, EE2 reduced female copepod survival and disrupted reproductive output, but only at high non-environmentally relevant concentrations.

Culture Techniques for Acartia clausi from the Romanian Black Sea coastal waters

As copepods are an important food source for most fish larvae, there is a continuing interest in developing techniques for culturing marine copepods as live food in aquaculture. Studies have shown that several species of calanoid copepods can be used successfully in aquaculture, acclimatized and grown in the laboratory over several generations and serve as testing organisms in acute toxicity tests. However, significant difficulties in cultivating calanoid copepods in high quantities were reported. They are related to their low tolerance to changes in water quality and reduced production capacity compared to other taxonomic groups. Therefore, working methods for obtaining viable cultures of calanoid copepods are dependent highly on the local environmental context. Until now, such a method has not been implemented for calanoid species from the Romanian Black Sea coast. This paper details the methodology we adapted and used for achieving a viable Acartia (Acartiura) clausi (Giesbrecht, 1889) culture using specimens collected along the Romania Black Sea coast Reproduction and egg hatching occurred under laboratory-controlled conditions, and viable individuals of A. clausi were obtained. Our results open the possibility of integrating this species in toxicity tests and food production for the marine aquaculture industry.

Seasonality and interannual variability of copepods in the Western English Channel, Celtic Sea, Bay of Biscay, and Cantabrian Sea with a special emphasis to Calanus helgolandicus and Acartia clausi

Abstract A total of five mesozooplankton time series data sets were assembled to compare the seasonal and interannual patterns of abundance of calanoid copepods in the Western English Channel (Station L4), Celtic Sea, Bay of Biscay (Continuous Plankton Recorder), and the Cantabrian Sea (RADIALES time series, Santander, St-4 and St-6) from January 1992 to December 1999. A strong seasonal component in taxonomic composition was detected at the locations considered. There was also a strong latitudinal effect on diversity at each location, southernmost locations being more diverse. The seasonal dynamics and year-to-year variability of two copepod species: Calanus helgolandicus and Acartia clausi were studied in detail. A latitudinal pattern in the seasonal cycles of both copepod species was observed. The peaks of both occur earlier in spring in the warmer southern region and move northwards, consistent with the temperature regimes at each location, supporting the broad concept that species occupy a thermal niche in time as well as in space. There was a strong degree of interannual variability between sites and between species. No clear trends, but some coherent events among data sets, reveal a regional response to environmental forcing factors. Correlations suggest possible connections with environmental indices like the North Atlantic Oscillation and the Gulf Stream North Wall index. There was a positive correlation between the NAO and the abundance of C. helgolandicus at station L4 off Plymouth; however, the relationship in the Celtic Sea and Bay of Biscay was opposite to that expected based on previous results. Despite the differences in the sampling techniques used within each dataset, the results are comparable and coherent in terms of taxonomic composition and the seasonal and interannual patterns detected.

Oxygen consumption rates and respiratory carbon losses in three species of copepods(Acartia clausi, Calanus helgolandicus and Limnocalanus macrurus) during starvation

Calanoid copepods with different life cycle strategies demonstrate varied velocity in the utilization of energy resources during starvation. This study analyzes the influence of multiday starvation on the rate of total, basal and active energy metabolism in adult females of two Marmara Sea and one Baltic Sea species of copepods; epiplanktonic Acartia clausi unable to accumulate lipid reserves and mesoplanktonic Calanus helgolandicus with minor lipid reserves in the oil sac (approximately 7% of body volume) and the Baltic Sea copepod Limnocalanus macrurus in quasi-diapausing state with large lipid reserves in the oil sac (approximately 19% of body volume). Initially, total weight specific respiration rates were about 0.12 μg C per μg C body weight per day (d$^{-1}$) for both Marmara Sea species at 20 °C and 0.079 d$^{-1}$ in the Baltic L. macrurus at 14 °C, decreasing significantly by 1.6-2.5 times with starvation, while basal metabolic rates, measured in the same anesthetized individuals, was nearly constant during starvation. In this regard, the active metabolic rates, defined as the difference between the respiration rate of active and anesthetized individuals, decreased during starvation by 1.7 times in C. helgolandicus and by 4.7 and 6 times in A. clausi and L. macrurus, respectively. In A. clausi and C. helgolandicus with minimal lipid reserves, total daily energy expenditure (5.1% of initial body carbon content) was twice as high as in L. macrurus (2.2% of initial body carbon content daily), which has a large oil sac. Overall, the trend demonstrates that despite different energy reserves, a decrease in the total energy metabolism in copepods occurs due to a reduction in energy expenditure for locomotor activity.

Gene expression and epigenetic responses of the marine Cladoceran, Evadne nordmanni, and the copepod, Acartia clausi, to elevated CO2.

Characterizing the capacity of marine organisms to adapt to climate change related drivers (e.g., pCO2 and temperature), and the possible rate of this adaptation, is required to assess their resilience (or lack thereof) to these drivers. Several studies have hypothesized that epigenetic markers such as DNA methylation, histone modifications and noncoding RNAs, act as drivers of adaptation in marine organisms, especially corals. However, this hypothesis has not been tested in zooplankton, a keystone organism in marine food webs. The objective of this study is to test the hypothesis that acute ocean acidification (OA) exposure alters DNA methylation in two zooplanktonic species—copepods (Acartia clausii) and cladocerans (Evadne nordmanii). We exposed these two species to near‐future OA conditions (400 and 900 ppm pCO2) for 24 h and assessed transcriptional and DNA methylation patterns using RNA sequencing and Reduced Representation Bisulfite Sequencing (RRBS). OA exposure caused differential expression of genes associated with energy metabolism, cytoskeletal and extracellular matrix functions, hypoxia and one‐carbon metabolism. Similarly, OA exposure also caused altered DNA methylation patterns in both species but the effect of these changes on gene expression and physiological effects remains to be determined. The results from this study form the basis for studies investigating the potential role of epigenetic mechanisms in OA induced phenotypic plasticity and/or adaptive responses in zooplanktonic organisms.

Surf zone zooplankton communities from the west coast of the Iberian Peninsula — Influence of season, substrate type and environmental factors

Studies on surf zone zooplankton biodiversity and population dynamics processes remain scarce in comparison to other coastal areas. In this work, we analysed the seasonal (winter/summer) variability of the surf zone zooplankton assemblage structure and copepod biomass of distinct areas with different substrate types (sandy beaches/rocky shores) at the west coast of the Iberian Peninsula (Portugal). Cypris of Cirripedia and Acartia clausi prevailed during summer at both areas. In the winter, Paracalanus parvus and Temora longicornis were the most abundant species at sandy beaches, while Harpacticoida n.id.1 and Euterpina acutifrons dominated at rocky shores. Copepod biomass was higher during the winter and in sandy beaches. Zooplankton showed distinct community structure according to season and substrate type, with Harpacticoids and cirripeds being the main responsible for seasonal differences, while fish eggs and harpacticoids were mainly responsible for differences among substrates. Surf zone assemblages were influenced by temperature, chlorophyll a and local hydrodynamics, which reflects species seasonal reproduction and drift in the water column.

Acute and chronic toxicity assessments of 17β-estradiol (E2) and 17α-ethinylestradiol (EE2) on the calanoid copepod Acartia clausi: Effects on survival, development, sex-ratio and reproduction

Estrogens, such as the 17β-estradiol (E2) and the 17α-ethinylestradiol (EE2), have been regarded as a global threat to aquatic ecosystems due to their pseudo-persistence, their high estrogenic activity and their toxicity towards non-target species. Data regarding their ecotoxicological effects on marine calanoid copepods are very scarce. In this study, the calanoid copepod Acartia clausi was used as a model organism for estrogens exposure in marine pelagic ecosystems. Lethal effects of estrogens on A. clausi life-stages (Embryos, one day old nauplii: N1, three day old nauplii: N3, copepodites: C1-C3 and adults: C6) were investigated using 48 h acute tests. Copepods showed stage-specific responses against E2 and EE2 acute exposure. The most resistant life stage was N1 with LC50 values > 1500 μg L-1 and >5000 μg L-1, respectively for E2 and EE2. For N3, C1-C3, and C6, sensitivity to estrogens decreased with age and survival was affected at concentrations above those detected in the environment reflecting low estrogens acute toxicity for these life stages. In contrast, embryonic stage revealed high vulnerability to E2 and EE2 acute effects. Embryos showed non-monotonic dose-response and hatching success was significantly reduced at low realistic concentrations of E2 (0.005, 0.5, and 5 μg L-1) and EE2 (0.05 and 5 μg L-1).Survival, development and sex ratio of A. clausi to EE2 exposure at 1 and 100 μg L-1 were also determined during a life cycle experiment. Fitness of the females of the generation F0 was evaluated by measuring lifespan, prosome length and egg production. The main observed effects were the decrease of females’ prosome length, the feminization of the population and the reduction of the egg production for the generation F0 at 100 μg L-1 of EE2. This concentration is above those reported in the environment indicating the tolerance of A. clausi to EE2 at environmentally relevant concentrations.

Current state and long-term changes in the mesozooplankton community of the Ukrainian and Georgian parts of the Black Sea as indicators of its ecological status

Water quality assessment is a key task of any measures in the field of water use, environmental management and protection. Thus, it is necessary to conduct systematic monitoring to assess the ecological state in the marine waters and to develop a strategy for its recovery. Anthropogenic impacts of various types leading to eutrophication and pollution of the Black Sea are changing the main characteristics of all components of the aquatic ecosystem. Zooplankton plays a key role in the pelagic food web. This article presents the results of the research on the state of zooplankton which was conducted during the Ukrainian-Georgian expedition in the framework of the international project “Emblas-plus” during 2016, 2017 and 2019. The ecological quality class of the investigated Black Sea waters was determined by the zooplankton integrated index (IZI). In Ukrainian waters in total, 49 taxa of zooplankton were registered. In 2017 taxonomic composition of zooplankton was more diverse (36 taxa in 2016, 35 in 2019). In Georgian waters in 2019, 40 taxa of mesozooplankton were registered, most of them are widespread forms in the Black Sea. The most diverse group is Crustacea (Cladocera and Copepoda).The most prevalent crustaceans were the eurythermic species, an important representative of forage zooplankton – Acartia (Acartiura) clausi Giesbrecht, 1889 and two thermophilic species of Calanoida – Acartia (Acanthacartia) tonsa Dana, 1849 and Centropages ponticus Karavaev, 1895. In Ukrainian waters average abundance and biomass of zooplankton in 2019 was similar to those in 2016 and much higher than in 2017. Dominant taxa and spatial distribution of zooplankton in 2019 were similar to those in 2016 and 2017. Average biomass of forage zooplankton in 2019 was approximately 10 times higher than in 2016 and 2017. In the Georgian coastal waters annual average abundance and biomass of mesozooplankton decreased, due to a sharp decline in the abundance of Noctiluca scintillans (Macartney) Kofoid & Swezy, 1921. It was found that at most of the stations the dominant role in the formation of zooplankton biomass was played by the organisms of forage zooplankton. By the IZI index, the subdivision Northwestern Black Sea Bays had “Good”, “Poor” and “Moderate” water quality in spring, summer and autumn respectively. The subdivision’s deepwater shelf and shallow shelf had “Bad” water quality. The subdivision Danube-Dnieper interfluve coastal waters had “High” water quality. The Danube Avandelta area had “High”, “Good” and “High” water quality in spring, summer and autumn respectively. The best ecological class status was in 2019 and the worst – in 2016. The main tendencies in changes in the mesozooplankton community in the Black Sea are decrease in the percentage of N. scintillans in the total zooplankton biomass and increase in the percentage of Copepoda. Those tendencies indicate decrease in the pressure of the negative eutrophication factor and show positive changes in the forage base of commercial planktophagous fish and the ecological status of the Black Sea waters.

Microplastic consumption and physiological response in Acartia clausi and Centropages typicus: Possible roles of feeding mechanisms

Multi-day experiments were carried out with two Marmara Sea calanoid copepod species: Acartia clausi and Centropages typicus, to assess the possible role of the type of feeding on the consumption of microplastics and its influence on the rate of energy metabolism of these species. In a mixture of microplastic beads (6μm diameter) and algae Rhodomonas salina (5–10μm size range) with equal concentrations of about 5000 cells/beads mL −1 the ambush feeder A. clausi consumed almost 5 times less microplastic 858.8 ± 294.1 beads ind −1 day −1 than the cruising feeder C. typicus and halved its consumption of microplastics alone, while C. typicus, on the contrary, increased its consumption rate of pure microplastics to 20237.4 ± 7020.41 beads ind −1 day −1. Both types of reaction to microplastics lead to a decrease in the respiratory rates of the copepods. During the 5 days of maintenance on a solely microplastic diet, the respiration rates of A. clausi and C. typicus decreased 2.2 and 3.4 times, respectively, due to a decrease in the energy spent on motor activity, whilst maintaining basal metabolic energy. It has been shown that in A. clausi, consuming microplastics, a decrease in respiration rate occurs in the same way as in individuals starving in filtered water. A more rapid respiration rate decrease in Centropages typicus consuming microplastics may be due to the greater energy expenditure on microplastic beads capture and egestion via fecal pellets. Acartia clausi seems to exhibit a better strategy in dealing with the adverse consequences of microplastics consumption in comparison to Centropages typicus.

Вплив з’єднувального каналу Куяльник – Чорне море на показники зоопланктону

Changes in the qualitative and quantitative indicators of mesozooplankton in seawater flowing througha special channel from the Odessa Bay of the Black Sea to the Kuyalnytsya estuary are considered in order tomaintain the permissible level of salinity. This is the first study in the world of the impact of a high-velocitycanal on zooplankton for seawater. In 2017, during the operation of the connecting channel (in the cold waterperiod), a comparison of zooplankton indicators was performed at sea and at the exit from the channel. As a resultof passing through the canal, the quantitative indicators of zooplankton decreased by an order of magnitude:the number at sea – 18372 ind. ∙ m-3 and at the exit from the canal – 398 ind. ∙ m-3; biomass – 60.0 mg ∙m-3 and 2.0 mg ∙ m-3, respectively. The percentage of losses fluctuated by seasons and ranged from 41% (April) to99% (February) in number, and from 27% (March) to 99% (February and December) in biomass. Such a large runwas associated with changes in the qualitative composition of zooplankton. Zooplankton of the study period wasrepresented by 11 taxa. Its constant component at sea and at the exit of the canal was Acartia clausi + tonsa. Insome months, the following representatives of zooplankton were present only in the sea: in April, the eutrophicindicator Noctiluca scintillans (Macartney) Kofoid & Swezy, 1921 (40 ind. ∙ m-3, 1.8962.0 mg ∙ m-3), and –Rissoa splendida Eichwald, 1830 (20 ind. ∙ m-3, 0.140 mg ∙ m-3), and in February – rotifers of the genus Keratella(1400 ind ∙ m-3, 0.700 mg ∙ m-3). All these species did not tolerate passage through the channel: N. scintillans and R. splendida did not pass at all; rotor losses ranged from 88.5% to 99.9%. Minimal losses were observedin Acartia clausi + tonsa from 0% to 83.0%, depending on the stage of development. Based on the calculationsof the monthly volume of water entering the estuary, 43,657 kg of zooplankton entered the estuary duringthe 6 months of the canal’ s operation, which could not harm the estuary resources.

Effects of HABs and a dystrophic event on zooplankton community structure in a Mediterranean lagoon (W Greece)

This study reports on the spatiotemporal distributions of zooplankton assemblages during two harmful algal blooms (ΗΑΒs) and a dystrophic crisis in Papas lagoon (W Greece, E Mediterranean), a water body with a long history of eutrophication phenomena. The main focus is placed on the impact of toxic microalgae on the metazooplankton community structure under contrasting environmental conditions including an anoxic event. Towards this aim, we recorded environmental parameters and sampled different size components of plankton communities (microalgae, microzooplankton and mesozooplankton) over the course of a year, in order to assess the metazooplankton assemblages (using nMDS, PERMANOVA and CCA) within a more comprehensive framework, considering lower trophic levels. HABs had a detrimental impact on all key holoplankton and meroplankton taxa regardless of environmental conditions, while their co-occurrence with anoxia resulted in the collapse of zooplankton populations. Recovery of zooplankton abundances after the compounded effects of HABs and anoxia was significantly slower in relation to the sole impact of HABs. Concerning holoplankton, dominance of egg-spawning calanoid copepods (Acartia clausi, Paracartia latisetosa) prior to the compounded extreme events shifted to smaller egg-carrying harpacticoids (Euterpina acutifrons) and cyclopoids (Oithona nana) in the recovered assemblages while in meroplankton, bivalvia larvae were largely replaced by cirripedia nauplii. These results suggested that the cumulative effects of HABs and dystrophic crises may significantly alter the taxonomic composition and size-structure of metazooplankton communities with possible harmful consequences for ecosystem functioning and fish and shellfish recruitment.

Plankton community and copepod production in a temperate coastal lagoon: What is changing in a short temporal scale?

Coastal lagoons are often exposed to intense short-term environmental changes and strong anthropogenic pressures influencing zooplanktonic communities and production. However, most works focus on long-term temporal scales using monthly or seasonal sampling strategies. The present study analysed the structure of the mesozooplanktonic assemblages, the production (egg production rates) and physiological condition (RNA:DNA ratio) of the copepod Acartia clausi in a temperate coastal lagoon (Ria Formosa) during the summer, using an intensive sampling approach. Salinity was the main factor affecting the short-term variability of mesozooplankton composition, followed by tidal phase (ebb tides) and semilunar cycle (spring tides). There was a positive relationship between the abundance of Appendicularia and the cladoceran Penilia avirostris with the toxic dinoflagellate Gymnodinium catenatum, suggesting no deleterious effects. The egg production rate of A. clausi was influenced by salinity and ammonia concentration, with a positive correlation between the egg productivity and the macronutrient, showing a possible adaptation of this calanoid species. The RNA:DNA index was positively related to egg production rate, suggesting that it is a good proxy for the reproductive output of copepods, even in short-term periods. This study shows that different timescales need to be included in regular monitoring of planktonic assemblages in coastal lagoons in order to understand the influence of environmental and anthropogenic variables on marine organisms.

Plankton community of trafficked ports as a baseline reference for Non Indigenous Species arrivals. Case study of the Port of Bar (South Adriatic Sea)

Plankton (ichthyo, zoo and phyto) communities were studied in the temperate shallow waters of the Port of Bar, one of the main cargo ports on the south-eastern Adriatic coast. Sampling was undertaken in February, April, June and October 2015 at 12 stations using the BALMAS Port Baseline Survey protocol. The research was conducted to determine the presence of invasive and potentially toxic plankton species in the port.The most dominant species of ichthyoplankton were eggs and larvae of families Engraulidae, Bothidae and Sparidae with a dominance of Engraulis encrasicolus, Arnoglossus laterna and Diplodus annularis. In addition to ichthyoplankton, sampling of phyto and zooplankton was performed to estimate the abundance and diversity of species.The most numerous zooplankton species throughout investigated period were Penilia avirostris, Euterpina acutifrons, Oithona nana, Acartia clausi, Centropages kroyeri, Paracalanus parvus, Oncaeidae and larvae of Bivalvia. One very unusual occurrence was the spawning of parrotfish Sparisoma cretense (Linnaeus, 1758), a species with Atlantic origin and tropical affinities, whose presence throughout the Mediterranean has shown an increasing trend over the last decade. The most dominant species of phytoplankton were the diatoms Chaetoceros affinis and Chaetoceros spp., Asterionellopsis glacialis, Pseudo-nitzschia spp., Thalassionema nitzschioides, and dinoflagellates Gymnodinium spp. and Prorocentrum triestinum. The potentially toxic species from genus Pseudo- nitzschia reached an abundance of 104 cells L-1. Toxic dinoflagellates Prorocentrum cordatum and P. micans reached values of 103 cells L-1.Although there were no HAOP species found during the survey, presence of several potentially toxic and toxic phytoplankton species whose impact is not sufficiently known indicates the necessity of introduction of regular monitoring activities and definition of preventive protection measures.

Polyethylene microplastics do not increase bioaccumulation or toxicity of nonylphenol and 4-MBC to marine zooplankton.

Global production of synthetic polymers, led by polyethylene (PE), rose steadily in the last decades, and marine ecosystems are considered as a global sink. Although PE is not biodegradable, in coastal areas it fragments into microplastics (MP) readily taken up by biota, and have been postulated as vectors of hydrophobic chemicals to marine organisms. We have tested this hypothesis using two organisms representative of the marine plankton, the holoplanktonic copepod Acartia clausi, and the meroplanktonic larva of the Paracentrotus lividus sea-urchin, and two model chemicals with similar hydrophobic properties, the 4-n-Nonylphenol and the 4-Methylbenzylidene-camphor used as plastic additive and UV filter in cosmetics. Both test species actively ingested the MP particles. However, the presence of MP never increased the bioaccumulation of neither model chemicals, nor their toxicity to the exposed organisms. Bioaccumulation was a linear function of waterborne chemical disregarding the level of MP. Toxicity, assessed by the threshold (EC10) and median (EC50) effect levels, was either independent of the level of MP or even in some instances significantly decreased in the presence of MPs. These consistent results challenge the assumption that MP act as vectors of hydrophobic chemicals to planktonic marine organisms.