Total Zooplankton Abundance Research Articles

Spatial Distribution of Plankton in Citanduy River, Cisayong Region, Tasikmalaya, West Java

The Cisayong area of ​​Tasikmalaya Regency is an area that is passed by the Citanduy River. The condition of the waters in the Citanduy River in Cisayong area, has received various waste inputs which will affect the quality of the river waters and cause a decrease in water fertility. Plankton can be used as an indicator of water fertility. This study aims to determine the spatial distribution of plankton in the Citanduy River, Cisayong Tasikmalaya Region, West Java. This research was conducted from January 2020 to February 2020. The research stations are located in four locations which are determined based on environmental and land use factors with a sampling period span of once every seven days. This research was conducted using a survey method and the data were analyzed descriptively and comparatively. The results showed that there were 67 genera of plankton from 5 phytoplankton phyla and 4 zooplankton phyla with most of the phytoplankton groups found from the Bacillariophyceae class and the zooplankton group from the Tubulinea class. The total average abundance of phytoplankton was 11,534 ind / L and the total average abundance of zooplankton was 295 ind / L. The biological index values ​​of the average diversity and dominance of phytoplankton were 2.72 and 0.11, while the average values ​​of diversity and dominance of zooplankton were 0.92 and 0.47. The results of the plankton spatial distribution show that the fertility of the waters in Citanduy River is classified as oligotrophic for station 1 and mesotrophic waters for stations 2,3, and 4.

Zooplankton abundance and community structure driven by tidal currents in a Mediterranean coastal lagoon (Boughrara, Tunisia, SW Mediterranean Sea)

Lagoons and coastal marine zones are very productive and useful ecosystems, but they are threatened by the effects of global change and anthropogenic pressures. These effects have a negative impact on the zooplankton, weakening its function of phytoplankton consumer, leading to uncontrolled proliferation of microalgae in case of eutrophication. In this study we test the hypothesis that tidal exchanges with the sea can counteract these deleterious effect, by renewing the zooplankton community and by enhancing its top-down control of phytoplankton through selective retention of zooplankton grazers. Our study focused on the southern region of the Gulf of Gabes and the Boughrara lagoon which presents the highest tidal range in the Mediterranean. During two field campaigns (October 2016 and April 2017) we have analyzed zooplankton descriptive (taxonomic composition, abundance; biomass) and functional (ingestion rate, grazing pressure) variables and environmental variables during time series at a fixed station during ebb-flood sequences and at 8 stations along a sea-lagoon transect and during different tidal amplitude periods. Multivariate analyses of both environmental parameters and zooplankton taxa showed the existence of three distinct zones along the sea-lagoon transect, but also the influence of tidal circulation and water mixing on the renewal of the zooplankton community up to the innermost zones of the lagoon. Time series gave clear patterns for the input/output of marine/lagoon species and show a net import for different taxa and for the total zooplankton abundance and biomass (mean flood/ebb ratio = 2.2 for the total abundance and 2.4 for the biomass), leading to differential retention of zooplankton in the lagoon and to an increase in the potential grazing pressure on phytoplankton (mean flood/ebb ratio = 2.8). We also estimated that the grazing pressure in the lagoon was twice higher during the periods of high tidal amplitudes (at or close to spring tide) compared to periods with low amplitude (neap tides), clearly showing that the retention of zooplankton significantly increases the grazing impact on phytoplankton. These results highlight the importance of the tidal forcing for maintaining the good status of the zooplankton structure and function in strongly anthropized coastal and lagoon ecosystems.

Copepod species assemblage and carbon biomass during two anomalous warm periods of distinct origin during 2014–2015 in the southern Gulf of California

Copepod species assemblage and biomass were studied during a weekly time series done during an anomalously warm and low sea surface Chlorophyll-a concentration period 2014–2015, compared with 2002–2018, at Cabo Pulmo National Park, Gulf of California, Mexico. Forty-nine copepod species accounted for 64% of the total zooplankton abundance. Three small copepods (Oncaea venusta 12.6%, Paracalanus parvus 11.5%, Clausocalanus jobei 8.6%) out of 45 species numerically dominated during 2014. The large copepods Subeucalanus subtenuis and Subeucalanus subcrassus out of 38 species recorded during 2015 increased in abundance accounting for 69% of copepod Carbon biomass. A Canonical Correspondence Analysis demonstrated SST drove copepod species assemblages. Copepod abundance was significantly higher during the cold (Nov–May) that during the warm (Jun–Oct) season and lower during Jan–Aug 2014 regional heatwave than during the Equatorial El Niño (Nov 2014–Dec 2015). Acartia tonsa was the only significant species indicator during the 2014 regional heatwave and Clausocalanus furcatus, Copilia mirabilis, and Cosmocalanus darwinii were significant species indicators of El Niño 2015. Copepod species assemblage had 87% tropical species during the Jan–Aug 2014 due to the regional heatwave that started the tropicalization of copepod community increasing to 95% of tropical species during El Niño 2015.

Zooplankton Distribution and Community Structure in the Pacific and Atlantic Sectors of the Southern Ocean during Austral Summer 2017–18: A Pilot Study Conducted from Ukrainian Long-Liners

Preliminary results of the pilot study of the zooplankton in the region between the Ross and Scotia Seas from November 2017 to April 2018 are presented. In total, 53 zooplankton samples were collected in the top 100 m water layer using vertical tows of a 0.1 m2 Juday net from four Ukrainian longliners operating during the Antarctic toothfish fishery. Total zooplankton abundance ranged from 3 to 2836 ind m−3 with a global mean of 360 ± 550 (±1 SD) ind m−3. The highest abundances were recorded at the northeastern Ross Sea. At those stations, small copepods (mainly Oithona spp., Oncaea spp., Ctenocalanus spp. and copepod nauplii) numerically dominated the samples. Total biomass ranged from 0.3 to 85 mg DW m−3 with a mean of 10.9 ± 14.5 mg DW m−3. The highest biomasses were recorded at the eastern Ross Sea, where pelagic tunicates Salpa thompsoni, siphonophores and ctenophora Callianira sp. accounted for >90% of total zooplankton biomass. At other stations, zooplankton biomass generally ranged from 5 to 20 mg DW m−3 with no clear pattern in distribution. The community composition was driven by the sampling latitude and/or season rather than longitudinally. This pilot study emphasized the unique opportunity to investigate zooplankton dynamics in the regions traditionally not sampled during the oceanographic surveys. It also created unprecedented opportunities to increase the seasonal and geographical zooplankton sampling coverage using ships of opportunity at a fraction of a dedicated oceanographic survey costs. The potential of such surveys are enormous in both providing invaluable information, contributing to existing long-term databases and enhancing an international collaboration in the Southern Ocean, particularly in light of recent modeling initiatives of the whole Antarctic system undertaken by the Commission for the Conservation of Antarctic Marine Living Resources.

Seasonal Changes in Zooplankton Community Structure and Distribution Pattern in the Yellow Sea, China

Changes in zooplankton community and distribution have significant influences on fishery resources due to their vital role in the marine food web. Seasonal variations in zooplankton community structure, abundance and biomass of major taxa and distribution pattern in the Yellow Sea, China were analyzed to obtain the current status of secondary production. A total of 73 taxa (mostly at the species level) were recorded with the highest species richness in summer and lowest in spring. The most abundant zooplankton species in all seasons were copepods Oithona similis, Paracalanus sp. and Calanus sinicus. The mean total zooplankton abundance was the highest in spring and followed a declining trend till winter. Cluster analysis identified two distinct zooplankton assemblages geographically found in the deep (> 50 m depth) and shallow regions. Zooplankton in the shallow region had higher abundance and species richness with the exception of winter season. Small copepods exhibited higher biomass in the shallow region but few abundance differences between the two domains. Large copepods (LC) and giant crustaceans (GC) usually had higher biomass in the deep region with the exceptions of LC in spring and GC in summer. Both the abundance and biomass of chaetognaths were significantly higher in the shallow region, where cnidarian abundance was also higher from spring to autumn. Water currents contributed to the transport of zooplankton between the two domains. The high abundance of copepods in the shallow region satisfied the requirements for the larval fish survival from spring to autumn. However, the high abundance of carnivorous zooplankton in summer–autumn may compete with larval fish for prey, and may directly feed on fish larvae.

Micro- and mesozooplankton at the edges of coastal tropical reefs (Tamandar\xe9, Brazil)

Tropical reef ecosystems are generally considered to be sinks of marine zooplankton, mainly due to the predation by scleractinian corals and other planktivores. The present study aims to evaluate the zooplankton community of a coastal reef in two specific environments: the reef edge and open-water channels between patch reefs. Sampling was carried out at two patch reefs that border the Tamandaré coastal lagoon system (Pernambuco State, Brazil). Two passive stationary nets (64 μm mesh size) were used: the Reef Edge Net (REN) and the Channel Midwater Neuston Net (CMNN). Sampling was performed simultaneously at both reefs during eight nocturnal sampling campaigns, always at new moon ebb tides. Zooplankton was classified by “origin” (estuarine, reef, neritic and neritic/estuarine). During all campaigns and at both sites, a significant buildup of zooplankton at the reefs was observed. Reef edges showed significantly higher abundance (77,579 ± 73,985 ind. m−3) and biomass (48.9 ± 45.5 mg C m−3) of zooplankton compared to open-water channels (9982 ± 11,427 ind. m−3 and 11.4 ± 21.9 mg C m−3, respectively). A total of 65 taxonomic groups were identified. Copepods were the most abundant group with a contribution of 69% for total zooplankton abundance, followed by foraminiferans, gastropod veligers, appendicularians, cirripedians nauplii, and polychaete larvae. Copepods from neritic/estuarine environments dominated the reef edges in both relative abundance and relative biomass (91% and 88%, respectively). The unexpectedly high abundance of copepods and other holoplankton at the reef edges, when compared to Indo-Pacific and Caribbean reefs, is probably due to very low cover of corals and other zooplanktivorous sessile animals (< 0.2%) on these coastal reefs, which leads to a very low predation mortality for zooplankters. Also, we propose that the reduced water column above the reef top leads to a buildup of very high densities in these environments.

Zooplankton-population dynamics in the Salado-River basin (Buenos Aires, Argentina) in relation to hydraulic works and resulting wetland function

The construction of drainage canals in the upper stretch of the Salado River has caused the input of salty waters into the basin, with unexplored consequences on zooplankton dynamics and reproduction. To determine the consequences of those anthropic interventions, zooplankton samples were taken under four hydrologic conditions (high water, mean flows, low flows, very low flows) in the canals and the river watercourse. Environmental variables were measured in situ (pH, temperature, conductivity, turbidity, flow velocity, water level, dissolved-oxygen concentration) and in the laboratory (chlorophyll a, nutrients). A total of 166 zooplankton taxa was identified, among which rotifers and ciliates were the most diverse and abundant. A redundancy analysis indicated temperature, conductivity, and water discharge to be the main constraints to zooplankton development. Accordingly, abundance peaks were recorded during mean and low flows in the spring and summer, and minimum values during high water (autumn–winter floodings). The dominant species, Brachionus plicatilis s.l., recorded outstanding densities at ca. 34,800 ind L–1—that figure representing a worldwide novelty—during low flows in the canals and at the river downstream site. The wetlands and shallow lakes in the study area acted as sources of inocula for the river, increasing the total abundance of zooplankton, gravid females, nauplii, copepodites, juveniles, and total number of eggs being carried at the second river site downstream from the canals’ discharges. The presence of diverse habitats coupled with the alternation of hydrologic conditions have resulted in the development of a very rich, complex zooplankton community.

Distribution of Zooplankton Community in the River Nile at Esna Barrages, Egypt in relation to some ecological factors

In riverine systems, zooplankton communities are usually thought to be driven by abiotic forces. This study was designed to assess the effect of ecological factors on the distribution of zooplankton community in the River Nile at Esna barrages which located 1.2 km downstream the old barrages. Monthly samples were collected during a period of one year from six sites situated in the River Nile, (upstream and downstream) of Esna Barrages. Seven physic-chemical parameters were measured during sampling using electronic portable instruments: air and water temperature, hydrogen ion concentration, dissolved oxygen, conductivity, total dissolved solids and turbidity. The collected zooplankton groups were Cladocera, Copepoda and Ostracoda where Cladocera exhibited the highest peak of density. The highest value of total abundance of zooplankton was recorded during winter 40% and the lowest value was recorded during summer 11%. The results indicated that Turbidity, pH and conductivity were the most affecting factors on abundance of all zooplankton groups during the study. Cladocera group correlated significantly with dissolved oxygen (p>0.01) and pH (p<0.01). Moreover, temperature and turbidity were the most affecting factors on Copepoda, while Ostracoda was affected by pH and conductivity.

Plankton distribution patterns and the relationship with environmental gradients and hydrological connectivity of wetlands in the Yellow River Delta

In order to discover the plankton distribution patterns and its relationship with environment gradients and hydrological connectivity in wetlands, samples from Yellow River Delta that span gradients in salinity and hydrological connectivity were analyzed in this study. Plankton community composition, abundance and biomass were determined and correlated with water variables and hydrological connectivity indexes to gain information about the forces that structure the plankton community in this dynamic environment. Phytoplankton with a total of 88 species and zooplankton with a total of 49 species were observed at an average abundance of 4.11 × 107 cells/L and 951.27 ind./L, respectively. Predominant species were Merismopedia minima G.Beck/Merismopedia elegans A. Braun ex Kützing (Cyanobacteria) and Trichocerca pusilla (Jennings) (Rotifera), accounting for over 10% of the total abundance of phytoplankton and zooplankton, respectively. The dominant species of phytoplankton communities were shifted from freshwater Chlorophyta (e.g., Oocystis sp.) to brackish Cyanobacteria (e.g., Merismopedia minima and Merismopedia elegans) and then to marine cyanobacterium (e.g., Oscillatoria sp. and Pseudoanabaena sp.); That shift in zooplankton community was from freshwater rotifers Trichocerca pusilla and Polyarthra trigla (Ehrenberg) to brackish rotifer Brachionus urceus (Linnaeus) and copepod Thermocyclops spp. and then to marine copepods Sinocalanus spp. and Microsetella spp. toward the river mouth. However, abundance, biomass and community similarity of plankton decreased with increasing water salinity and decreasing hydrological connectivity from upper reaches to river mouth. Salinity gradient could be major force for the shift of plankton community while the increasing hydrological connectivity between freshwater and saline habitats promoted the similarity of plankton distribution patterns within the wetland network.

Microplastics integrating the zooplanktonic fraction in a saline lake of Argentina: influence of water management.

This study address for the first time in Argentina and the South American continent the effect of water management on the presence of microplastics (MPs) in a shallow lake, assessing their contribution to the zooplankton fraction. Water samples were collected in the lakeand its principal affluent, an irrigation channel, from winter 2018 to summer 2019 with a zooplankton net (47μm). MPs were present in all analyzed samples, with a dominance of fibers, black color, and ≤ 1000μm range size. MPs concentration was maximum during summer at the lake (180 MPs m-3) while during spring (140 MPs m-3) at the channel. Rotifers and cyclopoids dominated the zooplanktonic fraction at both sites which range sizes (< 200 to 600μm) included most of the size range found for MPs (50-950μm). According to our results, the MPs found represents a potential risk for the first levels of the food web. In the lake, the concentration of MPs concerning total zooplankton abundance was higher when the channel was closed. Nevertheless, when the channel was open, the higher concentration in summer matches with the increase of tourism and an extraordinary rainfall. Our results suggest that while the runoff of agro-industrial waste regulates the MPs concentration in the channel, its water management, the touristic activities, and the runoff of MPs from nearby urban settlements regulate the concentration of MPs in the lake. These findings emphasize the need for better treatment of urban and agro-industrial waste that develops near continental aquatic systems, mainly in those where tourism activities are frequent and treatment facilities scarce.

Changes in the composition of the spring zooplankton of Lake Baikal

Since the 60s of the past century, researchers from Limnological Institute SB RAS have been regularly sampling zooplankton in a network of stationary stations along the Baikal water areas. In 2009-2018, the samples were collected in late May or early June immediately after the melting of ice during the complex expedition. The total biomass and abundance of zooplankton did not go beyond the interannual fluctuations observed in the 60-90s of the past century. A high abundance of spring rotifers in the Middle and Southern basins was also observed in 2015-2018. In the northern basin, the maximum rotifers indicator for the entire period of 30% of the plankton abundance was recorded only in 2016. The amount and composition of organisms in the surface layer depend on many factors. In our opinion, the depth and temperature characteristics of the water layer play an important role. The change in the heating and mixing of water could have led to observed shifts in the surface plankton composition.

Zooplankton Community Response to Seasonal Hypoxia: A Test of Three Hypotheses

Several hypotheses of how zooplankton communities respond to coastal hypoxia have been put forward in the literature over the past few decades. We explored three of those that are focused on how zooplankton composition or biomass is affected by seasonal hypoxia using data collected over two summers in Hood Canal, a seasonally-hypoxic sub-basin of Puget Sound, Washington. We conducted hydrographic profiles and zooplankton net tows at four stations, from a region in the south that annually experiences moderate hypoxia to a region in the north where oxygen remains above hypoxic levels. The specific hypotheses tested were that low oxygen leads to: (1) increased dominance of gelatinous relative to crustacean zooplankton, (2) increased dominance of cyclopoid copepods relative to calanoid copepods, and (3) overall decreased zooplankton abundance and biomass at hypoxic sites compared to where oxygen levels are high. Additionally, we examined whether the temporal stability of community structure was decreased by hypoxia. We found evidence of a shift toward more gelatinous zooplankton and lower total zooplankton abundance and biomass at hypoxic sites, but no clear increase in the dominance of cyclopoid relative to calanoid copepods. We also found the lowest variance in community structure at the most hypoxic site, in contrast to our prediction. Hypoxia can fundamentally alter marine ecosystems, but the impacts differ among systems.

Temporal distribution of zooplankton communities in coastal waters of the northern Bay of Bengal, Bangladesh

The temporal distribution pattern of zooplankton communities was studied in coastal waters of the northern Bay of Bengal, Bangladesh, during a 1-year period of investigation (May 2014-April 2015). Throughout the investigation, a total of 38 zooplankton species were recorded, in details 22 holo-plankton and 16 mero-plankton species. Copepods (Acartia danae, Acartia tonsa, Cyclops biscuspidatus, and Canthocalanus pauper), amphipods (Grandidierella megnae), shrimps (Penaeus indicus and Penaeus merguiensis), Acetes (Acetes indicus), and mysids (Americamysis bahai) were the dominant zooplankton taxa. The maximum abundance of total zooplankton and species richness was recorded in monsoon season whereas abundance of holo-plankton and species diversity was recorded in winter. Multivariate analyses revealed that the temporal pattern of species distribution of zooplankton communities significantly differed among the four seasons. RELATE analysis signified that temporal variation in species distribution and community structure of zooplankton significantly correlated with ecological condition of water. Moreover, BEST matching analysis indicated that NO2-N along with salinity, rainfall, transparency, TDS, TSS and pH were the main driving forces for these temporal variations in species distribution and community composition of zooplankton communities. Finally, correlation analysis showed that species evenness and diversity significantly correlated with salinity, transparency and TDS. These results suggest that zooplankton distribution pattern might be shaped by ecological condition of water in such marine ecosystem and may potentially be used as bioindicators of marine water quality.

Surf zone zooplankton temporal dynamics and their environmental regulation in a southwestern Atlantic sandy beach (Pehuen Co, Argentina)

Temporal dynamics of a zooplankton community were examined in the surf zone of Pehuen Co beach (PC), Argentina. The effect of environmental variables on the zooplankton composition and abundance was also investigated. Samples were obtained monthly between December 2016 and November 2017 from a fixed site during low tide. In all, 37 taxa were representative of the community. Meroplankton represented 59.45% of the total taxa, whereas holoplankton reached 40.54%. Five species were dominant: Acartia tonsa in summer months (2032 ind. m−3 in March), Paracalanus parvus and Ctenocalanus vanus in winter (4055 ind. m−3 and 264 ind. m−3, respectively, in July), and the sergestid Peisos petrunkevitchi (838.7 ind. m−3 in September) and the mysids Arthromysis magellanica (284 ind. m−3 in October) in spring. The highest total zooplankton abundances were registered in summer and winter, and the lowest ones were registered in autumn. The zooplankton community showed a strong seasonality, which can be mainly attributed to temporal changes in water temperature and to variations in suspended particulate matter (SPM), particulate organic matter (POM), and chlorophyll-a (Chl-a). Our results show that the zooplankton community structure was also affected by local variations in the velocity of the littoral current (VLC) and the wave height (WH). The present study shows that, besides seasonality, which seemed to be strong in this temperate region, other events affect zooplankton dynamics at a short-term time scale. Both VLC and WH are key factors that affect the zooplankton community structure in PC.

Significant shifts in coastal zooplankton populations through the 2015/16 Tasman Sea marine heatwave

The waters east of Tasmania, Australia, are warming at a rate 3–4 times the global average, largely as a result of the increasing duration and frequency of the southward penetration of the East Australia Current (EAC). In 2015/16, the southward movement of this sub-tropical current caused a severe marine heatwave (MHW) event. The effects of this event on the abundance and structure of the zooplankton community of south-east Tasmania are examined between November 2015 and January 2018. Generalized additive models indicated temperature to be significantly correlated with total zooplankton abundance (R2 = 0.6, p < 0.001). When modelled separately, species groups that are highly associated with the EAC, including bryozoan larvae (R2 = 0.2), echinoderm larvae (R2 = 0.6) and gelatinous zooplankton such as thaliaceans (R2 = 0.3), exhibited significant positive relationship with temperature (p < 0.001). The most abundant groups in samples; copepods (R2 = 0.6), appendicularians (R2 = 0.5) and cladocerans (R2 = 0.2), all exhibited negative relationships (p < 0.001; p < 0.001; p < 0.01, respectively). The abundances of cold-water and warm-water species of copepods were also analysed in relation to temperature. Sub-tropical species which are indicative of the East Australia Current, such as copepods from the Family Corycaeidae, and the calanoids Temora turbinata and Acartia danae, were present when temperatures exceeded ~17 °C, with a concurrent drop in the abundance of cold-water species. The east-coast of Tasmania is a region of rapid oceanographic change, and we have linked these changes with shifts in zooplankton population structure. Long-term studies from other regions that have also experienced marine heatwaves indicate these changes may have cascading implications for higher trophic levels. Gelatinous zooplankton and other zooplankton taxa not previously observed have now been documented in local predator diets. During warm periods, these species may represent an important alternative energy pathway.

Calibration of the zooplankton community size spectrum as an indicator of change in Canadian Shield lakes

Developing the crustacean zooplankton community size spectrum into an indicator of change in lakes requires quantification of the natural variability in the size spectrum related to broad-scale seasonal, annual, and spatial factors. Characterizing seasonal patterns of variation in the size spectrum is necessary so that monitoring programs can be designed to minimize the masking effects that seasonal processes can have on detecting longer-term temporal change. We used a random effects model to measure monthly, annual, and interlake variability in the slope (i.e., relative abundance of small and large organisms) and centered height (i.e., total abundance) of the crustacean zooplankton normalized abundance size spectrum from 1981 to 2011 among eight Canadian Shield lakes. Consistent with theoretical predictions, the slope was a relatively stable characteristic of the zooplankton community compared with the height, which varied significantly among lakes. We identified a seasonal signal in height and slope and used a mixed effects model to characterize the linear rate of change from May to October; there was an overall decline in height and an overall increase in slope. Seasonal variance was greater than annual variance for both the height and the slope, suggesting that long-term monitoring of lakes and interlake comparisons using zooplankton size spectra should be based on temporally standardized sampling protocols that minimize the effects of seasonal processes. We recommend sampling the zooplankton community in midsummer because this results in size spectrum estimates close to seasonal mean values.

Interannual dynamics of zooplankton in the Kola Section of the Barents Sea during the recent warming period

Abstract Our research focused on the analysis of interannual variability of zooplankton in the Kola Section (the Barents Sea) in the period of current warming in the Arctic basing on previously unpublished data. The zooplankton community was investigated based on the analysis of 240 plankton samples, collected in late May–early June 2009–2017. A total of 74 zooplankton taxa of nine phyla were identified in the plankton samples, but copepods were the most diverse and numerous taxonomic group. The biodiversity index varied considerably from year to year, but a stable tendency for the index to increase since the beginning of the period studied was observed. Copepods dominated in terms of abundance and biomass, comprising on average 73–96% of the total zooplankton abundance and 81–96% of the total zooplankton biomass. Calanus finmarchicus was the main zooplankton species utterly dominated by abundance and biomass (on average 92 and 97% respectively). Considerable differences in zooplankton abundance and biomass at different stations of the section were observed. Although the investigations were carried out during a warming period, interannual differences in zooplankton abundance and biomass were observed. Zooplankton biomasses were higher in the years with higher temperatures and stronger water inflow.

Spatial patterns of zooplankton size structure in relation to environmental factors in Jiaozhou Bay, South Yellow Sea.

The spatial variation in size structure of mesozooplankton and its relationship with environmental factors were studied from January 2006 to December 2010 in Jiaozhou Bay. The spatial body-size patterns of zooplankton differed significantly from the inner to the outer bay, and have a significant correlation with environmental variables, especially nutrients, salinity and water depth. The abundance of total zooplankton and small size ranks presented a decreasing gradient from the inner to the outer part, and was positive correlated with nutrients and negative with salinity, while the abundance of large size ranks exhibited an opposite gradient, and was positive correlated with water depth and negative with nutrients. The size spectra slope and size diversity were generally low in the inner part and closely related to body size ranks. Our results suggest that size structure patterns of zooplankton showed a clear spatial pattern and significantly associated with environmental factors in marine ecosystems.

Zooplankton communities in the Drake Passage through environmental boundaries: a snapshot of 2010, early spring.

BackgroundSpatial distribution of zooplankton communities influenced by various environmental factors is always important for understanding pelagic ecosystems. The area of the Drake Passage (Southern Ocean) is of particular interest owing to the high spatial and temporal variability of hydrological parameters affecting marine fauna. This study provides a survey of zooplankton composition and spatial distribution along a transect in the Drake Passage sampled during the 31th Cruise of RV “Akademik Sergey Vavilov” in November, 2010. The main aim was to trace the main regularities in spatial zooplankton structure and its relationships with the environmental parameters.MethodologyA total of 43 vertical hauls from the surface to 1,000 m depth were made at 13 stations using the Juday plankton net. 60 taxa were recorded, abundance and biomass of each were assessed. Environmental parameters including temperature, salinity, depth, horizontal distance between stations and surface chlorophyll concentration were tested as environmental factors possibly explaining plankton distribution.ResultsHigher zooplankton abundance and biomass with lower diversity were observed near the Polar Front. Cluster analysis revealed five different groups of zooplankton samples, four of which were arranged mostly by depth. Along the transect within the 1,000 m depth range, the qualitative taxonomical composition differed significantly with depth and to some extent differed also among horizontal hydrological regimes, while the quantitative structure of the communities (abundance of taxa) was mainly determined by depth. Plankton assemblages within the upper 300-m layer depended on hydrological fronts. Abundance of dominant taxa as well as total zooplankton abundance showed a clear correlation with depth, salinity and surface chlorophyll concentration. Some taxa also showed correlations with temperature and latitude. Between the stations the similarity in zooplankton structure was clearly dependent on the distance among them which indicates an importance of latitudinal gradient. Surface chlorophyll concentration was not correlated with zooplankton biomass, which can be explained by the uncompleted seasonal migrations of zooplankton from deeper waters in early spring.

The long‐term changes in plankton composition: Is Bay Sivash transforming back into one of the world's largest habitats ofArtemiasp. (Crustacea, Anostraca)?

Bay Sivash was a hypersaline lagoon but after construction of the North Crimean canal, it shifted to a brackish water state. In 2014, the canal was closed; a salinity increase started. In 2018 and 2019, plankton sampling was conducted in the bay at salinity from 30 to 100 g/L. A decrease in taxonomic diversity and total abundance was observed. Before November of 2018, Harpacticoida and chironomid larvae were the most common and abundant groups. Different stages of Artemia were consumed by invertebrate predators and fish at that time. In November 2018, Artemia stages contributed more than 90% to total zooplankton abundance at all sites excepting with salinity lower than 55 g/L. In June–July 2019, adult Artemia were at all sites with salinity higher than 82 g/L when there was no suppression by predators. A self-sustaining Artemia population in the bay may recover in 2 or 3 years, when the average salinity would reach 80–90 g/L; total abundance of the active Artemia stages may reach 3000–5000 ind. M−3 between April and August. The lagoon may become one of the world main habitats of Artemia having a significant impact to provide world's supply by its cysts.