Copepod Species Research Articles

Impact of shallow hydrothermal vent waters on monsoonal copepod distribution and abundance around active volcanic island off northeast Taiwan, West Pacific

Extreme oceanic environments such as shallow hydrothermal vents (HVs) have rarely been investigated with respect to their impact on the water column and its organisms, such as zooplankton. We collected mesozooplankton from the near shore shallow HV areas off northeast Taiwan during three distinct monsoonal periods in 2022. The results showed the occurrence of 99 copepod species belonging to 24 families and 49 genera from a one-year study. The results from similarity percentage (SIMPER) and indicator species analysis (IndVal) identified that top 5 species namely Temora turbinata, Oncaea venusta, Clausocalanus furcatus, Macrosetella gracilis, and Canthocalanus pauper showed variations in their abundance between HV and non-HV sites which contributed to 72.12 % dissimilarity with only four of the species with significantly higher contributions during the SW monsoon season. This distinction is explained by the fact that copepods were negatively affected by HV water. Furthermore, Temora turbinata (3530.7 ± 4967.83 ind. m−3), Calanus sinicus (70.86 ± 163.78 ind. m−3), and Paracalanus parvus (40.47 ± 85.67 ind. m−3) emerging as the dominant species with a clear seasonal succession pattern during the southwest monsoon, northeast-southwest monsoon transition, and northeast monsoon prevailing phase, respectively. The total abundance of copepod was significantly higher during the southwest monsoon than during the other two monsoonal periods (p < 0.01, one-way ANOVA). In contrast, the number of species and the richness index were significantly higher during the northeast-southwest and northeast monsoon than during the southwest monsoon period (p < 0.05, one-way ANOVA) indicating temporal succession in the copepod community.

Sublethal effects of microplastic and oil co-exposure on biological rates and lipid profiles of keystone Arctic copepods

Microplastics (MPs) and petroleum hydrocarbons are contaminants of emerging concern in the Arctic, but little is known about their co-exposure effects. In this study, we present the first assessment of the sublethal impacts resulting from combined exposure to microplastics and oil in three key Arctic copepod species. Specifically, we investigated the effects of a 5-day exposure to oil alone (1 μL L−1) and in combination with MPs (polyethylene microspheres, 20 μm, 20 MP mL−1) and dispersant (Corexit 9500, 0.05 μL L−1) on the biological functions and lipid profiles of the planktonic copepods Metridia longa, Calanus finmarchicus, and Calanus glacialis. Exposure to oil alone caused a significant reduction (34–58%) in fecal pellet production, but neither microplastics nor dispersant increased the negative effect of oil on fecal pellet production. C. glacialis and C. finmarchicus exposed to the studied pollutants for 5 days produced eggs with delayed hatching and lower hatching success. The highest hatching inhibition (50%) was observed in eggs of C. glacialis exposed to oil plus MPs and dispersant for five days. This indicates that maternal transfer of oil components to eggs negatively affects embryonic development and hatching. Lipid content and fatty acids profiles varied among the studied copepod species but were not affected by the tested pollutants after five days of exposure. By microscopical observation of fecal pellets, ingestion of small oil droplets and MPs was confirmed in all species, but the estimated ingestion of MPs was low (<25 MPs cop−1 d−1, <0.2% of total offered MPs) suggesting avoidance of MP consumption in copepods. Our results indicate that virgin MPs did not increase the toxicity of oil to the studied Arctic copepods under co-exposure conditions, and dispersants can slightly increase certain adverse effects of oil (hatching). However, environmentally relevant concentrations of oil alone can negatively impact Arctic keystone copepods and potentially the biological carbon pump. These findings emphasize the need to reduce petrogenic pollution and the risk of oil spills in the sensitive Arctic ecosystem.

Arctic copepod copper sensitivity and comparison with Antarctic and temperate copepods.

The ongoing global climate crisis increases temperatures in polar regions faster and with greater magnitude than elsewhere. The decline of Arctic sea ice opens up new passages, eventually leading to higher anthropogenic activities such as shipping, fishing, and mining. Climate change and anthropogenic activities will increase contaminant transport from temperate to Arctic regions. The shipping industry uses copper as an antifouling coating. Copper is an essential element but becomes toxic at excess concentrations, and its use may inadvertently affect non-target organisms such as copepods. Copper affects copepods by lowering reproductive output, prolonging developmental time, and causing increased mortality. As data on copper sensitivity of polar copepods at low temperatures are rare, we conducted onboard survival experiments with the Arctic region's most common copepod species (Calanus finmarchicus, C. glacialis, C. hyperboreus). Acute survival tests were done for up to 8 days on individuals in 70 ml bottles at 1 °C with nominal copper concentrations ranging from 3 to 480 μg L-1. We used a reduced General Unified Threshold model for Survival (GUTS) to analyse the data, and placed our results in the context of the few published copper sensitivity data of the Antarctic and temperate copepod species at low temperatures. The sensitivity of Cu exposure was similar between the three Calanus species. However, a model comparison suggests that the tested C. glacialis population is less sensitive than the other two species in our experiments. Compared to published data, the three Arctic species appear slightly less sensitive to copper compared to their Antarctic counterparts but more compared to their temperate ones. Our literature search revealed only a few available studies on the copper sensitivity of polar copepods. In the future, this species group will be exposed to more pollutants, which warrants more studies to predict potential risks, especially given possible interactions with environmental factors.

Diversity and Seasonal Variations of Zooplankton in Dudhiya Talab of Sirohi, India

In this study, the seasonal fluctuations of zooplankton and specific physico-chemical parameters were examined in Dudhiya Talab, a significant artificial reservoir located in Sirohi, Rajasthan. During the research period, a total of 41 zooplankton species were identified, comprising 12 species of Rotifera, 14 species of Cladocera, 5 species of Ostracoda, and 4 species of Copepoda. Among these, Rotifera emerged as the predominant group, with a peak abundance of 689 individuals per liter recorded in the summer, while the lowest numbers were noted during the winter season. Additionally, the zooplankton community exhibited correlations with various physico-chemical parameters. The findings of this research suggest that the distribution and density of zooplankton species are significantly affected by the prevailing physical and chemical conditions of the aquatic environment. Key words: Zooplankton, Physico-chemical factors,P Cladocera, Rotifera.

Assessing the potential of native copepods in Guatemala for Aedes vector control.

In this study we examine the feeding efficiency of copepods locally found in Guatemala on first instar Aedes aegypti larvae. Copepods are a potential tool for Aedes vector control that has shown promising results in the laboratory and in community-based field trials. Four different copepod species from different habitat types were included in the laboratory assays of this study. All four tested copepod species decreased the number of the first instar Aedes larvae that were inserted into the glass vessels compared with controls. However, average predation rates between the tested species were highly different, with Thermocyclops crassus and Mesocyclops longisetus achieving the highest, with 31.0% (standard deviation [SD] 18.9) and 28. 9% (SD 11.2), respectively. The copepod species with identified high predation rates are potential candidates for planned and other future field trials for community-based Aedes vector control with copepods in the region.

Ecological impact of artificial barrage on calanoid copepods in the Vembanad Lake, Southwest Coast of India

The Vembanad Lake (VL) is a brackish water lagoon, an integral part of Ramsar site, Vembanad Kol Wetland ecosystem on the southwestern coast of India. VL faces escalating anthropogenic impact, notably worsened by the establishment of the Thanneermukkom barrage (TMB) in 1976. This study hypothesizes that the TMB has led to significant ecological changes in VL, specifically altering the distribution and abundance of calanoid copepods, which are vital as a food source for higher trophic levels, particularly fish. To test this hypothesis, zooplankton samples were collected from various sites along the lake, and environmental parameters such as salinity and chlorophyll-a concentration were measured. This investigation reveals a distinct limnetic zone in the southern region, in contrast to the oligo-mesohaline zone in the north, attributed to the TMB. The study identifies the prevalence of calanoid copepod species such as Heliodiaptomus cinctus, Allodiaptomus mirabilipes, and Acartiella gravelyi in the TMB-South region, reflecting a freshwater-dominated ecosystem. The low salinity and high chlorophyll-a content in this area create an optimal environment for these species. In contrast, the dominance of Acartia (Odontacartia) spinicauda, Pseudodiaptomus serricadatus, and Paracalanus sp. in the TMB-North indicates higher salinity levels, with species in this region adapting to a different ecological niche. Thus, the installation of the TMB has significantly altered the ecological balance of VL by dividing the water body into two distinct salinity zones. This separation has led to changes in the distribution and abundance of calanoid copepods, which are essential for energy transfer to higher trophic levels in the VL food web, consequently affecting fish populations and overall biodiversity.

The modified artificial cohort method for three dominant pelagic copepods in the northern North Pacific revealed species-specific differences in the optimum temperature

The most concerning recent ocean changes in temperature issues are known as marine heat waves. Under these conditions, it is important to evaluate the effects of temperature on zooplankton. In this study, we investigated the growth rates of three dominant copepod species (Eucalanus bungii, Metridia pacifica, and Neocalanus plumchrus) in the northern North Pacific under three different temperature conditions (3, 7, and 11°C) using an artificial cohort method. Experimental conditions for 42 hour incubations were set to light intensity and photoperiod corresponding to 50 m depth. The dissolved oxygen solubility after rearing ranged from 69.2% to 102.1%, suggesting sufficient conditions for copepod growth. Chlorophyll a increased in 83% of the experiments, indicating that the food conditions were sufficient for the copepods. The mean proportion of dead specimens evaluated using neutral red was 10.2%, corresponding with the reported values in the field. Thus, it can be concluded that the laboratory-rearing conditions used in this study provided sufficient food, and the only effect evaluated would be that of the three different temperatures. Since the developmental time for each stage is longer than the rearing period, it is important to conduct experiments with a large number of individuals to obtain accurate growth rate results. The specific growth rates of E. bungii and M. pacifica increased with increasing temperature. In contrast, N. plumchrus showed the highest growth rate under moderate water temperature conditions. In terms of weight units (dry, carbon, and nitrogen), the carbon weight-specific growth rates were higher than those of the other two units, a common characteristic of the three species. This reflected lipid accumulation during the late copepodite stages. The interspecies differences in growth rate responses to water temperature reflect species-specific differences in temperature tolerance or the optimum temperature for each species. As E. bungii and M. pacifica reproduce near the surface layer through income breeding, their temperature tolerance or optimum temperature is expected to be high. However, because the reproduction of N. plumchrus occurs in the cold deep layer by using capital breeding, its temperature tolerance and optimum temperature would be lower than those of the former two species.

An ecological niche model that considers local relationships among variables: The Environmental String Model

AbstractMany methods have been proposed to model the spatial distribution of a species. While some methods have been specifically designed for this purpose, others are well‐known statistical tools that can be used in many scientific fields. In this paper, I propose a new ecological niche model, called the Environmental String Model (ESM), that is based on the concept of environmental string, which is defined as being a combination of environmental variables, with as many nodes as environmental variables. There are two types of environmental strings: (1) the abundance‐known string and (2) the abundance‐unknown string (or target string) for which an estimation of abundance is searched. The novelty of the model is that it assesses the abundance associated with a target string from nearby abundance‐known strings, which preserve the local multidimensional relationships with the target string. The model does not provide an abundance estimate in the absence of data from a similar environment and it can therefore deal with truncated spatial distributions or niches. It is tested in the North Atlantic Ocean on two key copepod species, Calanus finmarchicus and Calanus helgolandicus, which have been monitored by the Continuous Plankton Recorder (CPR) survey for decades. I investigate the influence of variables on model performance. I show that the model reconstructs the mean spatial distribution and seasonal fluctuations in both Calanus well. When compared with generalized linear models (GLMs), generalized additive models (GAMs) and generalized regression neural network (GRNN), the ESM gives the best performance. I propose a number of indicators to evaluate the robustness of estimated abundance in space and time and show how the model may be extended to presence/absence or presence‐only data. I think that the ESM could be used to fill gaps in any sampling program such as the CPR survey and many satellite databases (e.g., ocean color and photosynthetically active radiation).

Relationship between Respiration Rate and Body Weight in Arctic Copepods at Subzero Temperature

Dependence of the respiration rate (R) on the animal’s weight (W) is described by the equation R = a Wb, where the exponential coefficient b is usually taken equal to ¾. However, several authors indicate that the value of the coefficient b may vary with temperature changes as well as during ontogeny. In the Arctic seas, copepods spend most of their lives at temperature below or close to zero. Meanwhile, there are very few measurements of respiration rate at temperatures ≤ 0°C, which does not allow us to estimate the overall R(W) dependence at these temperatures. The work was carried out in three cruises of the R/V “Akademik Mstislav Keldysh” in the Siberian Arctic seas in 2018–2020. Copepods caught from the sea were adapted to experimental temperature and placed in tightly capped vials filled with filtered sea water for 24 h. The oxygen concentration was measured with a fiber-optic oxygen probe. The results of 120 measurements of respiration rate and 111 measurements of body carbon in five species of copepods at a temperature of -1.5°C are presented. The obtained relationship between body carbon content (W) and the prosome length (L) was described by the equation W = 6.982 L3.221, and the dependence of respiration on body weight was described by the equation R = 0.077 W0.753. No effect of a subzero temperature on the coefficient b was found. The regression parameters of R(W) did not change with the ontogenetic development of Calanus glacialis.

Altimeter-derived poleward Lagrangian pathways in the California Current System: Part 1

We use altimeter-derived geostrophic velocities, with and without the addition of surface Ekman transports, to create trajectories for virtual parcels in the California Current System (CCS). The goal is to investigate the poleward transport of passive water parcels in the surface 50–100 m of the nominally equatorward system. Motivation for the study is provided by observations of anomalous biomass of copepods with warm water affinities along the Newport Hydrographic Line off central Oregon (44.7°N) during El Niño years, as well as during and following the 2014–2016 marine heat wave. By backward tracking virtual parcels from 44.7°N, we find that the most distant source of passive water parcels in the upper ocean during a one-year period of travel is from within the Southern California Bight (SCB), north of 30°N. To make that journey, parcels use the Inshore Countercurrent off southern and central California during summer–winter and the Davidson Current off northern California and Oregon during autumn–winter. The inclusion of small-scale eddy diffusion usually increases the number of parcels that reach more northern latitudes, while the inclusion of Ekman velocities more often reduces those numbers. Even so, parcels can travel from the SCB to central Oregon in either the Ekman layer or beneath it in the geostrophic flow. Using backward tracking, we find that parcels arrive at 44.7°N most often in winter–spring, least often in autumn. They arrive from within the large-cape region off northern California (41°–42°N) during all years and all months, from just south of the large-cape region (38°–39°N) during most years but seldom in autumn, from south of Monterey Bay along central California (36°N) and within the SCB (34.5°N) during a third (or less) of the years and only in winter-spring. The shortest average transit times are found in winter: for parcels reaching 44.7°N in February, the average transit time is 2 months for parcels coming from 41°–42°N, 4 months for parcels coming from 38°–39°N, and 5–6 months or more for parcels coming from south of 36°N. Transit times increase as the arrival time progresses from winter to autumn. The longest average transit times are for parcels reaching central Oregon in autumn (9–12 months in October for parcels coming from south of 39°N). This makes the journey a multi-generational task for the copepods. Interannual variability in the observed southern copepod species biomass off central Oregon correlates highly with years when more virtual parcels from the south reach central and northern Oregon, providing increased confidence in the results found with the altimeter-derived parcel trajectories.

Checklist and distribution of the groundwater crustacean fauna from Sicily, Italy

Owing to the “Racovitzan impediment”, the groundwater fauna of most biogeographical regions is currently inadequately known, thus hampering our understanding of subterranean biodiversity and its protection. Based on an extensive bibliographical review accompanied by fieldwork to localize occurrence sites, a checklist of crustacean taxa reported to date from Sicilian groundwater is provided, and their distribution is described. Among the 63 taxa recorded to date, 43 belong to the class Copepoda (orders Cyclopoida and Harpacticoida), 15 to the class Malacostraca (orders Amphipoda, Bathynellacea, Isopoda, and Thermosbaenacea), and 5 to the class Ostracoda (order Podocopida). Conversely, to date, no representatives of the copepod order Calanoida nor species of the class Branchiopoda have been recorded from groundwater habitats on the island. Several taxa require accurate taxonomic revision or are yet to be formally described and are thus at present left in open nomenclature. Finally, the date of publication of several copepod and amphipod taxa is amended. A high incidence of stygobites (i.e., obligate groundwater dwellers) has been observed in malacostracans, whereas nearly half of the recorded copepods were non-stygobites. This pattern is mirrored by the incidence of endemic species, which is higher in malacostracans than in copepods. The only non-stygobitic crustacean species endemic to Sicily observed in the frame of present review is the asellid isopod Proasellus montalentii. The paucity of information currently available on the Sicilian groundwater ostracods prevents us from drawing conclusions regarding this crustacean group. The origin and composition of Sicilian groundwater crustacean fauna can be explained by considering three major faunal assemblages: the presence of ancient paleoendemic taxa, likely of Miocene origin, the colonization of the groundwater of the island during late Pliocene and Pleistocene land connections with peninsular Italy, and the direct colonization of these environments from the sea; no species of African origin have been discovered to date. Based on currently available data, the groundwater of southeastern Sicily hosts the highest species richness and some of the most biogeographically interesting taxa. Unfortunately, a progressive lowering and salinization of the local aquifers possibly due to climate change and its overexploitation threats this fauna, and several taxa are disappearing even before their discovery and description.

Nutritional condition drives spatial variation in physiology of Antarctic lipid-storing copepods.

Lipid-rich copepods form an essential link between primary producers and higher trophic levels in high-latitude oceans. These zooplankton can take advantage of ephemeral phytoplankton blooms to fuel development and reproduction. However, we have limited understanding of how the physiological condition of these animals varies in relation to environmental factors such as food availability. Due to high advection, it is likely that physiological plasticity, rather than local adaptation, is primarily responsible for physiological differences within a region. We use transcriptomics and other physiological metrics to understand how two species of copepods (Calanoides acutus and Calanus propinquus) vary across environmental gradients along the West Antarctic Peninsula. For the primarily herbivorous C. acutus, physiological separation between sampling locations appears to be driven by feeding status, and gene expression differences indicate differential expression of genes regulating lipid metabolism, reproduction, aerobic metabolism, and protein translation. For the more omnivorous C. propinquus, physiology and gene expression did not segregate as clearly by location, showed minimal signs of food deprivation at any location, and had a weaker relationship with chlorophyll compared to C. acutus. By comparing these results with concurrent starvation experiments, we find that spatial variation in gene expression reflects short-term differences in food availability (particularly for C. acutus), and we identify genes whose expression indicates recent feeding status. Further examination of the relationships between food availability, copepod physiology, and population dynamics will ultimately improve our capacity to predict how copepod populations will respond to rapidly changing environmental conditions in the West Antarctic Peninsula ecosystem.

Subchronic Effects of Tetrachloroethylene on Two Freshwater Copepod Species: Implications for Groundwater Risk Assessment.

Aliphatic chlorinated hydrocarbons, notably tetrachloroethylene (also known as perchloroethylene [PCE]), are persistent, mobile, and toxic (PMT) and/or very persistent, mobile, and toxic (vPMT) groundwater pollutants, often exceeding safe drinking water thresholds. The present study delves into the groundwater risk assessment of PCE with a novel focus on the sensitivity of stygobitic species-organisms uniquely adapted to groundwater environments. Through a comparative analysis of the subchronic effects of PCE on the locomotion behavior of two copepod species, the stygobitic Moraria sp. and the nonstygobitic Bryocamptus zschokkei, we highlighted the inadequacy of the current European predicted-no-effect concentration of PCE for groundwater ecosystems. Our findings indicate significant behavioral impairments in both species at a concentration (32 ng/L PCE) well below the threshold deemed safe, suggesting that the current European guidelines for groundwater risk assessment may not adequately protect the unique biodiversity of groundwater habitats. Importantly, B. zschokkei demonstrated sensitivity to PCE comparable to or greater than that of the target stygobitic species, suggesting its utility as a substitute species in groundwater risk assessment. The present study adds to the limited research on the ecotoxicological sensitivity of groundwater species to PMT/vPMT chemicals and highlights the need for refined groundwater risk-assessment methodologies that consider the susceptibilities of stygobitic species. Environ Toxicol Chem 2024;00:1-13. © 2024 The Author(s). Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Integrative approach to monitoring metazoan diversity and distribution in two Mediterranean coastal sites through morphology and organismal eDNA

Marine and coastal ecosystems respond to climate change in various ways, such as the type of ecosystem, the species composition, interactions, and distribution, and the effect of local stressors. Metazoan organisms, particularly zooplankton, are important indicators for monitoring the effects climate-driven warming in marine coastal ecosystems over the long term. In this study, the diversity and distribution of zooplankton communities in the Mediterranean Sea (Canyon Dohrn and LTER-MareChiara, Gulf of Naples), a known biodiversity and climate changes hotspot, have been assessed using the integration of morphological-based identification and organismal eDNA. Our findings showed that the multi-locus strategy including the mitochondrial cytochrome c oxidase I (COI) gene and the hypervariable region V9 of the 18S rDNA (18S V9) as targets, improved the taxonomic overview, with the COI gene being more effective than the 18S V9 region for metazoans at the species level. However, appendicularians were detected only with the 18S V9 region. Overall, organismal eDNA is a powerful approach for revealing hidden biodiversity, especially for gelatinous and meroplankton components, and provided new insights into biodiversity patterns. The ecological importance of calanoid copepods in coastal ecosystems has been confirmed. In contrast, the discovery of 13 new metazoan records in the Mediterranean Sea, including two non-indigenous copepod species, suggested that local stressors affect zooplankton community structure and resilience, highlighting the importance of biomonitoring and protecting marine coastal ecosystems.

A description of a new species of Mongolodiaptomus Kiefer, 1937 (Copepoda, Calanoida, Diaptomidae) from Thailand with an up-to-date key to the genus.

The genus Mongolodiaptomus is widely distributed in stagnant water bodies in Southeast Asia. During a comprehensive collection of freshwater copepods from different areas in Thailand, a previously unknown species of calanoid copepod, Mongolodiaptomusphutakaensis sp. nov., was recorded. Representatives were found in a natural swamp located in the Kok Phutaka community forest in Khon Kaen Province, northeastern Thailand. The new species belongs to the "M.loeiensis species group" and most closely resembles M.loeiensis and M.mekongensis by having a distinct shape of the second exopodal segment of the male right P5, with enlarged proximal and distal parts of the outer margin as well as a bent and twisted principal lateral spine. The new species can be distinguished from its congeners by various characters in the males. The ventral surface of the right caudal ramus has two chitinous teeth and two knobs. The intercoxal plate is slightly produced distally and without any spine. The right P5 basis lacks a hyaline membrane on the inner margin but has a distinct spur-like chitinous process at the mid-distal margin on the posterior surface. The left P5 basis has a thin, longer hyaline lamella on the inner margin. The new species is rare, having been observed in only one out of approximately 5,000 surveyed locations in Thailand. A detailed morphological comparison and an up-to-date key to the Mongolodiaptomus species are presented. Their taxonomic characters, interspecies relationships, and biogeography are discussed.

Machine learning applied to species occurrence and interactions: the missing link in biodiversity assessment and modelling of Antarctic plankton distribution

BackgroundPlankton is the essential ecological category that occupies the lower levels of aquatic trophic networks, representing a good indicator of environmental change. However, most studies deal with distribution of single species or taxa and do not take into account the complex of biological interactions of the real world that rule the ecological processes.ResultsThis study focused on analyzing Antarctic marine phytoplankton, mesozooplankton, and microzooplankton, examining their biological interactions and co-existences. Field data yielded 1053 biological interaction values, 762 coexistence values, and 15 zero values. Six phytoplankton assemblages and six copepod species were selected based on their abundance and ecological roles. Using 23 environmental descriptors, we modelled the distribution of taxa to accurately represent their occurrences. Sampling was conducted during the 2016–2017 Italian National Antarctic Programme (PNRA) ‘P-ROSE’ project in the East Ross Sea. Machine learning techniques were applied to the occurrence data to generate 48 predictive species distribution maps (SDMs), producing 3D maps for the entire Ross Sea area. These models quantitatively predicted the occurrences of each copepod and phytoplankton assemblage, providing crucial insights into potential variations in biotic and trophic interactions, with significant implications for the management and conservation of Antarctic marine resources. The Receiver Operating Characteristic (ROC) results indicated the highest model efficiency, for Cyanophyta (74%) among phytoplankton assemblages and Paralabidocera antarctica (83%) among copepod communities. The SDMs revealed distinct spatial heterogeneity in the Ross Sea area, with an average Relative Index of Occurrence values of 0.28 (min: 0; max: 0.65) for phytoplankton assemblages and 0.39 (min: 0; max: 0.71) for copepods.ConclusionThe results of this study are essential for a science-based management for one of the world’s most pristine ecosystems and addressing potential climate-induced alterations in species interactions. Our study emphasizes the importance of considering biological interactions in planktonic studies, employing open access and machine learning for measurable and repeatable distribution modelling, and providing crucial ecological insights for informed conservation strategies in the face of environmental change.

Response of the abundance and size of Acartia (Acartiura) hongi (Copepoda: Calanoida) copepodites to environmental variables in Laizhou Bay, Bohai Sea

Acartia hongi is an endemic brackish and coastal copepod species in the Yellow and Bohai Seas. To investigate the population structure and distribution, we examined samples of A. hongi copepodites from May 2011 to April 2012, excluding the ice season. A generalized additive model (GAM) was used to explore the response of the abundance and prosome length (PL) of A. hongi to a range of environmental variables, including temperature, salinity, chlorophyll a (Chl a) content, Yellow River runoff, pelagic fish, and phytoplankton. A. hongi occurred throughout the survey season continuously and area widely in Laizhou Bay. It was a dominant species in the copepod community and showed a maximum abundance during April and May. The CI-CIII copepodites were the primary contributors to the total population of A. hongi during the blooming months. Population densities (>10,000 ind.m−3) occurred in nearshore waters with temperatures between 10°C and 15°C and salinities between 25 and 27. Mean PLs across all copepodite stages were shortest in August or September and longest in March. The best-fitting GAMs for copepodite abundance and PL included the variables of temperature, salinity, Chl a content, and runoff. The abundance of A. hongi copepodites decreased with increasing temperature, particularly for CI and CII copepodites, when the temperature exceeded 10–15°C. Salinity and runoff showed more negative correlations with A. hongi copepodites of younger stages. The PLs across the copepodite stages demonstrated significant inverse correlations with temperature. Furthermore, the Chl a content significantly influenced the PLs of CVs and adults through interactions with temperature. Overall, this study highlights temperature as a critical factor for the abundance and size distribution of the A. hongi population. Copepodites at earlier stages are more sensitive to temperature and salinity fluctuations. These findings provide valuable insights into the environmental effects on the A. hongi population dynamics in Laizhou Bay.

Biodiversity and functioning of mesozooplankton in a changing Ross Sea

Literature on Ross Sea zooplankton is limited, although it is the most productive system and has the highest biomass of phytoplankton in the Southern Ocean. Energy transfer within the food web and response of continental shelf food web to climate change depend on the knowledge of the density and distribution of zooplankton. We evaluated its density, composition, spatial distribution and their potential relations with environmental factors and specific water mass presence. Particular attention was given to copepods. Mesozooplankton samples were collected between 14 January and February 11, 2017 from 14 stations in the western Ross Sea and Terra Nova Bay, while other micronekton samplings were completed at 6 stations. Results highlighted three pools of stations: one inside Terra Nova Bay with the highest densities, one on the platform with lower mean density, and the third represented by a N–S transept at 175°E with the lowest mean density. This partitioning of the region fit with the grouping of stations according to a ternary plot based on the different percentages of water masses in each station and reflected the similarity of zooplankton. The presence of specific water masses and their contribution in the upper 200 m influences zooplankton biodiversity and density. A phylogenetic tree of the zooplankton was constructed to analyse the distance among the observed taxa. The area located near the coast exhibited the highest degree of phylogenetic overdispersion. In coastal waters, typical copepod species constituted the main part of the neritic zooplankton of Terra Nova Bay and Ross Sea. Oithona similis was the most abundant species both in coastal and offshore sectors, followed by pteropods, polychaetes and euphausiids.

Plankton Community Stability and Drive Factor Identification Guizhou Plateau Reservoir

In order to understand the stability of the zooplankton and phytoplankton communities in the Guizhou plateau reservoir environment, the process of reservoir water quality change affecting the stability of plankton was studied. The changes in the plankton community and water quality in three different nutrient reservoirs （Huaxi Reservoir, Goupitan Reservoir, and Hailong Reservoir） were studied from October 2020 to August 2021. The stability of the zooplankton and phytoplankton communities was studied using time-lag analysis （TLA）. Variance decomposition analysis （VPA） was used to explore the response of the two communities to environmental changes. The driving factors of plankton community changes in reservoirs were also revealed. The results showed that Huaxi Reservoir and Goupitan Reservoir were mesotrophic reservoirs, and Hailong Reservoir was a eutrophic reservoir. The average comprehensive nutrition indices of the three reservoirs were 44.07, 44.68, and 50.25. A total of 51 species of zooplankton rotifers, 39 species of rotifers, three species of copepods, and nine species of cladocera were identified. Among them, the abundance of rotifers was the highest, accounting for 85.96%. A total of seven phyla and 73 species of phytoplankton were identified, including 16 species in the phylum Cyanophyta, 32 species in the phylum Chlorophyta, 16 species in the phylum Diatoma, three species in the phylum Chlorophyta, four species in the phylum Euglenophyta, and one species each in the phyla Cryptophyta and Chrysophyta. Among them, the abundance of cyanobacteria and diatoms was the highest, accounting for 66.2% and 27.35%, respectively. The median absolute deviation （MAD） of the Bray-Curtis distance of zooplankton and phytoplankton community in the three reservoirs were 0.67 and 0.65 in Huaxi Reservoir, 0.80 and 0.69 in Goupitan Reservoir, and 0.85 and 0.47 in Hailong Reservoir, respectively. The larger the value, the greater the variation in the community. The absolute value of the slope of zooplankton was greater than that of phytoplankton in the TLA results, and the absolute values of the slopes were 0.018 and 0.004, respectively. The larger the absolute value of the slope, the faster the community variability. The zooplankton community in the three reservoirs was less stable than the phytoplankton community and more sensitive to environmental changes, and the degree of variation was greater. The higher the degree of eutrophication of the reservoir, the more obvious this phenomenon. VPA showed that the changes in plankton communities in Huaxi Reservoir and Hailong Reservoir were mainly influenced by water temperature and eutrophication factors. The changes in planktonic community in Goupitan Reservoir were mainly influenced by water temperature and chemical factors. The driving factors of Huaxi Reservoir were water temperature, TP, permanganate index, and SD. The driving factors of Goupitan Reservoir were water temperature, NO3-- N, and pH. The driving factors of Hailong Reservoir were water temperature and TP. Nutrients and water temperature were the main factors affecting the stability of plankton communities in reservoirs.

A new species of Metadiaptomus Wang & Wang, 2024 from the Qinghai-Tibetan Plateau, China (Copepoda, Calanoida, Diaptomidae)

A new copepod species Metadiaptomus aliensis sp. nov., collected from lakes in the Qinghai-Tibetan Plateau, is described. M. aliensis sp. nov. is differentiated by total length of both sexes, the fifth leg of both sexes, and the right antennule of the male, compared with the similar species M. asiaticus Ul'yanin, 1875 and M. chevreuxi Guerne & Richard, 1894. The low temperature species M. aliensis sp. nov. survives in a wide salinity range from fresh to polyhaline water, and a wide alkalinity range from 6.12 to 40.39 mmol/L. The first generic record of M. aliensis sp. nov. in the Qinghai-Tibetan Plateau contributes to our understanding of the global biogeography of the subfamily Paradiaptominae.