Zooplankton Abundance Research Articles

Abiotic–Biotic Interrelations in the Context of Stabilized Ecological Potential of Post-Mining Waters

The creation of man-made reservoirs has become more common globally and provides many important technical, biological, and socio-economic functions. The study focused on abiotic–biotic and trophic interrelations responsible for ecological potential and biodiversity in potentially stabilized conditions of the aquatic ecosystem. Therefore, the analyses concerned 2014–2015 and 2018–2019, assuming repeatable hydrochemical conditions, in three chambers (C1–C3) of the Kamień sedimentation pond supplied through opencast mine drainage. The studies indicated eutrophic levels and at least good ecological potential. Phytoplankton were quite abundant at an average biomass of 10.0 mg L−1, while zooplankton and planktivorous fish were estimated at 0.51 mg L−1 and 74.3 g m−2, respectively The general order of the growth level in chambers was C-1 > C-2 > C-3, C-1 < C-2 < C-3, and C-1 < C-3 < C-2 for phytoplankton, zooplankton, and planktivorous fish, respectively, and indicated clear differences. Both mechanisms of the top-down and bottom-up effects were revealed in all chambers. Some significant differences between abiotic and biotic (i.e., fish density and biomass, phytoplankton density) factors were recorded on a temporal scale, whereas the density and biomass of planktivorous fish were significantly differentiated on a spatial scale. The stabilized conditions concerned relatively high biodiversity but quite abundant phytoplankton and lower zooplankton abundances, trophic efficiency, and eutrophy under the maximum ecological potential.

Dynamics of Zooplankton along the Romanian Black Sea Coastline: Temporal Variation, Community Structure, and Environmental Drivers

Between 2013 and 2020, a total of 27 distinct zooplankton taxa, encompassing both holoplanktonic and meroplanktonic organisms spanning different classes and orders, were successfully identified along the Romanian Black Sea coastline. The seasonal dispersion patterns of these zooplankton taxa revealed a notable augmentation in species identification during the warmer periods, contrasting with reduced zooplankton diversity during the colder seasons. This phenomenon was underscored by the outcomes of SIMPER analysis, which highlighted that copepods, meroplankton, and cladocerans predominantly contributed to the community structure during warmer seasons. In contrast, during colder seasons, cladocerans were scarcely represented, and the density levels of copepods and meroplankton were diminished. From a quantitative perspective, the dinoflagellate Noctiluca scintillans, exhibited its highest density and biomass during the warm season, with a relatively lower representation during colder periods. The variation in the abundance of zooplankton was closely linked to changes in salinity and temperature, culminating in noticeable fluctuations, which were particularly evident during the cold season. During this period, the values of zooplankton abundance were notably lower compared to those observed in the warmer season. The comprehension of zooplankton dynamics stands as a critical facet for assessing biodiversity, monitoring ecosystem well-being, and guiding conservation endeavours.

Characterizing the Variability of a Physical Driver of North Atlantic Right Whale Foraging Habitat Using Altimetric Indices

Physical ocean circulation features, especially the Gaspé Current (GC) intrusion, influence the transport and aggregation of whale prey, thereby influencing the whale foraging habitat in the Gulf of St. Lawrence (GSL), Canada. We employ satellite altimetry-derived sea level anomaly (SLA) indices to monitor interannual variations in the intensity of the GC in the North Atlantic Right Whale (Eubalaena glacialis; NARW) habitat in the GSL. Measurements of surface slope and volume transport are taken from the SLA profiles along a repeating ground track of the Jason-2/3 satellites. These are employed as complementary proxies in characterizations of physical processes in the GSL. The relationship between altimetric indices and indices of zooplankton abundance are explored in the southern GSL. Results demonstrate that an altimetric index estimated from surface slope (Indexslope−half) is correlated with river discharge of the St. Lawrence River and can be utilized to infer variations in GC intensities. Time series of the altimetric indices during 2009–2021 are found to exhibit interannual and seasonal environmental variability, which influence transport into the southern GSL. As captured by the altimetric indices, these features of the surface ocean circulation can be linked to zooplankton variations in the Shediac Valley, where NARWs are frequently observed. Therefore, in linking physical drivers of ocean dynamics to the NARW foraging habitat, variations in these indices can also potentially help describe some features of the distribution patterns of NARW sightings in this area.

Spatial patterns of zooplankton abundance, biovolume, and size structure in response to environmental variables: a case study in the Yellow Sea and East China Sea

Spatial patterns of zooplankton abundance, biovolume, and size structure in response to environmental variables: a case study in the Yellow Sea and East China Sea

The pelagic food web of the Western Adriatic Sea: a focus on the role of small pelagics

The Adriatic Sea is one of the largest areas of occurrence of shared small pelagic stocks and the most fished area of the Mediterranean Sea, which is in turn one of the most exploited basins of the world. The variations in the stable isotope contents (δ15N and δ13C) were determined for three small pelagic fishes (i.e., Engraulis encrasicolus, Sardina pilchardus, and Sprattus sprattus, respectively known as anchovies, sardines and sprats) collected across the western side of the basin. Our data allowed to determine the width and features of their trophic niches, to assess potential overlap or resource partitioning among them, and likely anticipate species adaptation to future climate change scenarios. Moreover, variations in stable isotope contents were correlated to both resource availability (i.e., mesozooplankton) and environmental variables. The high productivity and in turn the high resource availability of the basin, especially in the northern part, resulted in favor of the resource partitioning that occurs in each sub-area of the Adriatic Sea among the three species. Medium-sized specimens of the three species mostly fed on small zooplankton, while adult sprats relied on large copepods and those of sardines and anchovies also consumed large portion of phytoplankton, confirming the high trophic plasticity of these two dominants small pelagic species. However, considering that anchovies have the greatest degree of trophic diversity compared with the other two species, they could be the most adapted to changing feeding conditions. The increase in sea temperatures that are reducing primary production and in turn zooplankton abundances, coupled with even more frequent extreme meteorologic events could exacerbate the competition for trophic resources among pelagic mesopredators, and could lead to more notable stocks’ fluctuations and unpredictable wasp-waist effects.

The Ecosystem of Lake Tolpanjärvi, Western Karelia, Preserved in Natural State

The results of the study of Lake Tolpanjärvi’s ecosystem are reported. Its hydrological and geochemical indices, as well as the current condition of biotic communities (zooplankton, benthos and fish population), were studied and analyzed. Analysis of the chemical composition of water indicates the low organic matter content (total phosphorus 0.007 mg/l, nitrogen 0.26 mg/l) of the lake. The Tolpanjärvi is an oligotrophic lake, as indicated by the abundance of zooplankton (with a biomass of less than 1 g/m3) and zoobenthos (biomass 0.44 g/m2). The lake is of an oligosaprobic class (2nd quality class, clean natural water), as evidenced by its saprobity index estimated using Pantle–Bukk’s method. The quantitative indices of zoobenthos varied from 120 individuals/m2 and 0.08 g/m2 in the profundal zone to 1200 inds./м2 and 0.86 g/m2 in the quiet littoral zone. The lake is more similar in the chironomid index (К – 2.00) to clean natural water. It is inhabited by 8 fish species of 5 families. The fish population is dominated by the whitefish Coregonus lavaretus, the perch Perca fluviatilis and the roach Rutilus rutilus. Two ecological forms of whitefish, differing in both the number of gill rakers (sparsely-rakered 18–24 and medium-rakered 28–36) and biological indices (linear-weight growth рост, maturation, fertility and feeding), occur in the lake. Stable highly diverse ecosystems were shown to form the basis for the preservation of the gene pool and for assessment of the current condition of water bodies heavily affected by human activities.

Effects of bigheaded carp on larval Freshwater Drum diets

AbstractObjectiveWe investigated foraging success, diet composition, and the abundances of various prey taxa in the diets of larval Freshwater Drum Aplodinotus grunniens across a gradient of bigheaded carp (Bighead Carp Hypophthalmichthys nobilis and Silver Carp H. molitrix) relative abundance and in relation to zooplankton density, temperature, discharge, and larval fish densities in the upper Mississippi River (UMR).MethodsWe sampled fish larvae and zooplankton every 10 days (May–August 2017 and 2018) from UMR Pools 14, 16, and 18–20; collected environmental data from nearby gauging stations; and assessed bigheaded carp relative abundance.ResultCrustacean zooplankton abundance was positively related to larval foraging success. Copepods were the dominant prey, but larvae also consumed large proportions of rotifer eggs and benthic insect larvae. Bigheaded carp presence and catch per unit effort were positively associated with increased larval consumption of atypical prey (rotifer eggs and aquatic insect larvae) and cyclopoid copepods. Cladocerans were the rarest prey consumed by larvae in pools where bigheaded carp were present, but they were more frequently consumed in pools where bigheaded carp were absent. In addition to bigheaded carp abundance, river discharge was negatively associated with larval consumption of cladocerans, aquatic insect larvae, and rotifers; water temperature was negatively associated with the consumption of copepods and cladocerans; and rotifer abundance was positively associated with their consumption.ConclusionWe suggest that bigheaded carp alter larval fish diets to prey that may be less energetically beneficial, which can have implications for larval growth and survival.

Zooplankton Abundance and Growth of Carps in Farm-Ponds of Different Agro-Climatic Zones of Karnataka

Availability of planktons / natural fish food plays an important role in getting better growth of fish from farm ponds. Study was carried out to evaluate the zooplankton community and growth performance of Carp fishes in farm ponds of coastal and malnad agro-climatic regions of Karnataka. All the ponds were manured with cowdung and poultry manure @ 2000 kg/ha. for the production of planktons. Catla, Rohu and common carp fingerlings were stocked in all the ponds @ 10,000 nos. /ha in 1:1:1 ratio and fishes were fed with groundnut oil cake and rice bran (in 1:1 ratio) @ 5% of the body weight every day. The water samples from all the ponds were collected and filtered for zooplanktons using nylon bolting cloth (60 µm). The growth of fishes in terms of weight was recorded. The analyzed zooplankton planktons were classified into 5 class’s viz., Rotifera, Protozoa, Copepoda, Cladocera and Ostracod. Among zooplanktons observed, copepod contributed maximum to zooplankton community followed by rotifers, cladocerans and ostracod. In coastal ponds the average maximum number of zooplankton 10,368 Cells/m3 and minimum number of 176 Cells/m3 were observed. In Malnad ponds the average maximum number of zooplankton 21,797 Cells/m3 and minimum number of 1579 Cells/m3 were observed. The average maximum growth of Catla, Rohu and Common carp was observed in coastal ponds were 884.42, 640.1 and 692.27 gms respectively and in Malnad farm ponds 1080.71, 954.19 and 1023.18 gms respectively. Use of cowdung and poultry manure in combination was found useful for getting better growth in farm ponds of both the regions.

Abundance and diversity of phytoplankton and zooplankton in selected village tanks in Vavuniya, Sri Lanka

The abundance and diversity of planktons in selected village tanks namely Peraru, Nochchimoddai and Mamaduwa in the Vavuniya district were studied from March to April, 2021. The objectives of the study were to identify the phyto- and zooplanktons, and to estimate their abundance and diversity in the selected village tanks. Planktons were sampled weekly using a plankton net. Based on the morphological features, samples were initially identified up to the genus level using standard keys and their respective abundance was estimated using Sedgewick- rafter counting cell. Simultaneously, water samples were also collected at each location to determine the water quality parameters such as dissolved oxygen, electrical conductivity, pH, turbidity, temperature, and, nitrate and phosphate concentrations. The results showed that there were 16 genera of Chlorophyceae, six genera of Bacillariophyceae and seven genera of Cyanophyceae, while three species of Copepods, one species of Cladocerans and 10 species of Rotifers were identified. The dominant phytoplanktons belonged to Bacillariophyceae, and represented about 50% of total population of phytoplanktons while Cyanophyceae as the least abundant. Copepods were dominant in Peraru and Nochchimoddai tanks, representing more than 50% of the total zooplankton population while Rotifers were dominant in Mamaduwa village tank, with a 58% of total zooplankton population.

Studies on Limnological Parameters and their Impact on the Distribution and Diversity of Zooplankton in Anchar Lake, Kashmir

The transfer of energy from producers to consumers, such as fish, fish larvae, and invertebrates, is facilitated by zooplankton. Consequently, zooplankton play a crucial part in the productivity and functioning of aquatic ecosystems, and they are also involved in the application of several emerging environmental management concepts, such as Environmental Impact Assessment (EIA), bioindication of pollution, and biomonitoring. To analyse the present condition of the Anchar Lake, this research was conducted to investigate the zooplankton association, their abundance, richness, diversity (Cladocera and Rotifera), and their seasonal fluctuations in connection to limnological factors. Four sampling sites were used to examine thirteen physicochemical parameters along with the abundance of zooplankton from January 2019 to December 2020. During the present investigation, significant variation (p < 0.05) was observed in transparency (trans), dissolved oxygen (DO), pH, electrical conductivity (EC), total alkalinity (TA), nitrate-nitrogen (NO3-N), total hardness (TH), and total phosphorus (TP) between the different sites of Anchar Lake, whereas non-significant variation was observed in air temperature (AT), water temperature (WT), free carbon dioxide (FCO2), chloride (Cl-), and nitrite-nitrogen (NO2-N). The results further revealed a total of 44 zooplankton species, belonging to two: Rotifera (27 species) and Cladocera (17 species). The zooplankton diversity was found to vary on spatiotemporal scales showing maximum values for the Shannon diversity index in the case of Cladocera during spring (2.63±0.25) and for Rotifera during summer (2.53±0.25) whereas, minimum diversity values were recorded during winter for both Cladocera and Rotifera (1.54±0.44 & 1.47±0.54 respectively). On the spatial scale, site-A2 showed maximum diversity of Cladocera (2.3±0.21), while site-A4 showed maximum diversity of Rotifera (1.99±0.03). The influence of physicochemical parameters on zooplankton distribution and diversity provides a detailed picture of the impact of pollution load in Anchar Lake.

The abundance and types of plankton in milkfish ponds at Banyuasin South Sumatera

Tidal lowland is an area with significant potential for fisheries development, especially in aquaculture. Abundant water supply and land availability provide great opportunities for cultivating aquaculture commodities such as fish, shrimp, and crab. However, effective water quality management poses a significant challenge, necessitating a comprehensive evaluation based on biological, physical, and chemical assessment. Among the crucial parameters influencing water fertility, the presence of plankton stands out. Therefore, this study aimed to investigate water fertility by identifying plankton species, abundance, diversity, dominancy, and water quality in milkfish ponds at Banyuasin, South Sumatra. The results showed that the abundance of phytoplankton and zooplankton ranged from 1030-1791 individual L-1 and 103-461 individual L-1, respectively. Furthermore, Bacillariaceae was recorded to be the highest specie, followed by Cyanophyta, Chlorophyta, Protozoa, Rotifer, and Arthropoda. The range diversity index varied between 1 to 2.6, while the density and dominance indices ranged from 0.9 and 1, as well as 0.1 and 0.8, respectively. The classification of the pond's fertility fell within the mesotrophic category, signifying a moderate level. In conclusion, the water quality maintained an optimum range, thereby supporting the growth of plankton and milkfish. Meanwhile, only ammonia was below the optimum range stipulated by PP No. 22 of 2021 suggested.Keywords:bioindicatormilkfishplanktontidal lowlandwater quality

Zooplankton derived organic matter as a food source for benthic coral

Zooplankton derived organic matter, such as fecal pellets and carcasses, may be a vital source of nutrients for benthic corals. In shallow tropical reefs, settling particles (organic matter) often reach the benthos, in contrast with deeper systems where the particles are recycled/transformed prior to reaching the benthos. Furthermore, zooplankton fecal pellets aggregate together and entrain additional organic matter, aiding in the transference of organic matter to reefs. These settling particles can be ingested by coral as a supplement to the nutrients obtained from their symbionts (zooxanthellae). Settling particles can provide essential lipids, which are produced by phytoplankton and repackaged by zooplankton, to coral reefs. Settling particles collected in the Upper Florida Keys Reef Tract were used to evaluate the role of zooplankton in the transportation of organic matter. The general chemical composition remained constant in the sediment particles, and total sediment flux generally decreased as distance from shore increased. Through lipid and stable isotope analyses, zooplankton sources were determined to contribute approximately 50% of the total lipid content in the particles with smaller contributions coming from phytoplankton, bacteria, vascular plants, and coral. The repackaging of phytoplankton derived organic matter by zooplankton demonstrates zooplankton as a primary driver of settling particles in coral reefs. The shallow water column in the reef habitat results in less recycling and remineralization of sediment particles compared to the open ocean, leading to the direct transport of organic matter from the surface to the benthos. Therefore, zooplankton abundance and composition play a vital role in determining the availability of organic matter and settling particles on coral reefs. Without zooplankton transporting organic matter throughout the water column reefs would likely decline, meaning it is imperative that zooplankton derived organic matter is considered when studying coral reefs.

Phototropic Behavioral Responses of Zooplankton in Lake Baikal In Situ and during the Anthropogenic Impact Modeling

Earlier, we showed that the registration of the behavioral responses of autochthonous mesozooplankton communities in situ is a more dynamic methodological approach in the biological assessment of the environmental well-being of aquatic ecosystems, as well as an alternative method to generally accepted tests on mortality and immobilization. The change in behavioral responses, including phototropic responses, may occur at lower concentrations of pollutants, leading to the inhibition of the risk-avoidance response of predatory fish attack and, ultimately, to the change in zooplankton abundance and biodiversity. The biological significance of such changes is quite high since zooplankters form the basis of food chains. This work studies the possibility of biomonitoring the quality of fresh water in Lake Baikal according to the state of the autochthonous mesozooplankton community in summer and winter using a digital holographic camera developed and tested by us in laboratory conditions. This method makes it possible to determine the concentration of plankters in the controlled volume of the DHC and perform photostimulation with different levels of illuminance. The depth profilometry of the phototropic response was compared with the profilometry of plankton concentration, intraspecific diversity of crustaceans according to the Pielou index, and the results of catching using the Juday net in the natural environment of the lake and during the modeling of the anthropogenic impact (introduction of table salt solution into the local area close to the registration probe). The circadian rhythm parameters were determined by the spectral analysis of the long-term registration of the phototropic response dynamics. It was noted that the inhibition of the phototropic response was the most adequate marker of the exogenous impact and the appearance of an alternating factor among the studied indicators of the state of the plankton community, namely, intraspecific diversity, synchronism of circadian rhythms, and response to paired photostimulation. The revealed patterns of behavioral responses of autochthonous zooplankton in natural and artificially modified conditions will allow for the implementation of long-term continuous control over the environmental well-being of water areas, including the collection ponds of treatment facilities, cooling ponds of nuclear power plants, and other water areas in contact with potentially hazardous facilities. The comparison of the identified patterns with the behavioral responses of euryhaline mesozooplankton will expand this method to assess the well-being of salt-water and marine reservoirs under the anthropogenic impact and will make it possible to create a continuous monitoring system.

Viability of zooplankton resting eggs in rice field sediment after pesticide applications.

Many herbicide products are commonly used in agricultural areas to prevent and eliminate weeds. Contamination from these toxicants in water might affect aquatic organisms not only in the active stage, but also in the diapause stage. To test the effect of herbicide on the resting eggs of zooplankton, we prepared two rice fields: one field without the application of pesticides (RF-NPA) and one with the application of pesticides (RF-PA) in a sampling year. We conducted a hatching experiment for 30 days. Twenty-four taxa of zooplankton were found. Sixteen species of these were rotifers, seven species were cladocerans and one taxon was an unidentified nauplius copepod. The species richness of zooplankton between RF-NPA (17 taxa) and RF-PA (16 taxa) was close, but species compositions between RF-NPA and RF-PA were different, indicated by the similarity index of 0.545. Lecanidae was the most diverse family of rotifers in both rice fields with nine species, while Chydoridae was the most diverse family of cladocerans (four species). The total abundance of zooplankton of RF-NPA was higher than RF-PA with 1,897 and 1,286 individuals, respectively. The Shannon-Wiener diversity index (H´) and Pielou's evenness (J) in RF-NPA were higher than in RF-PA. The high species richness of zooplankton in both rice fields occurred on days 18 to 30. On the other hand, the highest abundance was recorded on day 18 for RF-NPA and on day 24 for RF-PA. The non-metric multidimensional scaling (NMDS) demonstrated significant differences in zooplankton community composition between RF-NPA and RF-PA (p < 0.05; ANOSIM test). According to the diversity indices, the RF-NPA has more diversity than the RF-PA, which might be a result of herbicide application in the sampling year. This study suggests that the toxicity of glyphosate should be a concern in terms of the biodiversity of rice field ecosystems.

Biotic and Abiotic Interactions in Freshwater Mesocosms Determine Fate and Toxicity of CuO Nanoparticles.

Transformation, dissolution, and sorption of copper oxide nanoparticles (CuO-NP) play an important role in freshwater ecosystems. We present the first mesocosm experiment on the fate of CuO-NP and the dynamics of the zooplankton community over a period of 12 months. Increasingly low (0.08-0.28 mg Cu L-1) and high (0.99-2.99 mg Cu L-1) concentrations of CuO-NP and CuSO4 (0.10-0.34 mg Cu L-1) were tested in a multiple dosing scenario. At the high applied concentration (CuO-NP_H) CuO-NP aggregated and sank onto the sediment layer, where we recovered 63% of Cu applied. For the low concentration (CuO-NP_L) only 41% of applied copper could be recovered in the sediment. In the water column, the percentage of initially applied Cu recovered was on average 3-fold higher for CuO-NP_L than for CuO-NP_H. Zooplankton abundance was substantially compromised in the treatments CuSO4 (p < 0.001) and CuO-NP_L (p < 0.001). Community analysis indicated that Cladocera were most affected (bk = -0.49), followed by Nematocera (bk = -0.32). The abundance of Cladocera over time and of Dixidae in summer was significantly reduced in the treatment CuO-NP_L (p < 0.001; p < 0.05) compared to the Control. Our results indicate a higher potential for negative impacts on the freshwater community when lower concentrations of CuO-NP (<0.1 mg Cu L-1) enter the ecosystem.

A dataset of zooplankton occurrence, abundance, and biomass in the Far East seas and adjacent Pacific Ocean waters.

Planktonic animals drifting or floating in the sea have small body sizes and weights from hundreds to thousands of milligrams, and are primarily the food for other zooplankton and macrofauna: fish, cephalopods, seabirds and marine mammals, and also the larval pool of many benthic invertebrates. This paper describes a unique dataset of zooplankton collected from 1984 to 2013 in the North Pacific (the Bering Sea, Sea of Okhotsk, Sea of Japan and adjacent Pacific Ocean waters), one of the most productive and economically important regions of the world's oceans using a Juday net made of kapron sieve No. 49 (0.168 mm mesh) with a 0.1 m2 opening. The information in this dataset has already been used to quantify the inventory of marine biological resources and assess the waters of the Russian Far Eastern seas and adjacent Pacific Ocean. In 2016, five tabular reference books were printed in Russian in limited numbers containing the species composition, occurrence (number and percentage of samples), abundance and biomass (in individuals per cubic meter, milligrams per cubic meter) of zooplankton in the surveyed area. The data are grouped by species, developmental stages, size fractions (animal length of 0.6-1.2 mm "fine/small," 1.2-3.2 mm "medium" and >3.2 mm "large"), standard regions (their total area is more than 6 million km2 ), vertical layers of water, light and dark time of the day, four seasons of the year and multiyear periods, in which there were considerable changes in the biota of the region caused by global climate and oceanographic factors. This information has recently been verified, corrected, translated into English, transformed from text to digital format, and supplemented by GIS with maps of the standard regions by which data were aggregated using morphometric parameters (volume of water in cubic kilometers in the region, in its epipelagic 0-200 m, and upper epipelagic 0-50 m water layers, occupied area in square kilometers, longitude and latitude of their centroids in decimal degrees) to increase their availability to the scientific community worldwide. The data enable the evaluation of the total plankton stock of the Russian Far Eastern seas in the North Pacific (in trillions of specimens and thousands of tons), recalculate the volumetric characteristics of density into areal characteristics (in billions of specimens per square kilometer or tons per square kilometer), and, using previously published tables on calorific value and chemical composition of zooplankton, obtain their energy characteristics. Such data are crucial for the proper management of marine resources, aquaculture development, nature conservation, and the assessment of the anthropogenic impact on nature. The presented metadata provide a detailed description of how this unique dataset was created, sources and volume of gathered information, its benefits and drawbacks, some results on the quantitative inventory of marine biological resources and assessment of waters in the North Pacific, and future prospects for the use of this type of dataset in applied and fundamental research. There are no copyright restrictions on the data; please cite this data paper when the data are used in publications.

Mesozooplankton and oceanographic conditions in the North zone of Coiba National Park (Panamá, Central America)

Zooplankton plays a central role in marine trophic webs, where community indexes (diversity, abundance, and biomass) are affected by regional and local oceanographic conditions. The multinational conservation initiative, known as the Eastern Tropical Marine Corridor (CMAR) encompasses a network of Marine Protected Areas of unique and high biological diversity along the Eastern Tropical Pacific. Zooplankton studies in this area are scarce and recently conducted. In the northern zone of Coiba Island (Coiba National Park, Panamá) during the dry and rainy seasons (2019–2020), the composition, abundance, and biomass of mesozooplankton and its relationship with oceanographic variables (temperature, salinity and euphotic zone) were analyzed. In both seasons different oceanographic conditions were found with vertical heterogeneities of temperature (T) and salinity and seasonal significant differences in minimum of T and euphotic zone depth (EZ). Zooplankton abundance and total biomass showed positive associations, and maximum values during the dry season; in oblique trawls, total zooplankton biomass showed negative associations with T (−0,60) and positive with Secchi disk depth (0.67). These patterns suggest higher zooplankton productivity during dry season associated with oceanographic conditions in the North zone of Coiba Island. Organisms were classified to the lowest taxonomic level possible (Sub-family or Genus) and a total of 33 zooplankton taxa were identified. In the holoplankton the most important groups were Copepoda, Chaetognata, Appendicularia and Thaliacea, while in the meroplankton larvae of Crustacea, Echinodermatha and Mollusca were the most common groups. Zooplankton indexes (abundance, biomass and composition) were similar to those reported for other CMAR islands. Strategies recommended to strengthen biodiversity conservation in this MPA include more studies on taxonomy, trophic dynamics, and connectivity of planktonic communities as central link in marine trophic webs.

Assessment of the Zooplankton Community and Water Quality in an Artificial Freshwater Lake from a Semi-Arid Area (Irbid, Jordan)

Zooplankton play a crucial role in aquatic food chains and contain many species, which could be bioindicators of water quality and ecosystem health. The ecological impacts of eutrophication on zooplankton composition in freshwater lakes have recently gained wide interest. Geographic location and water-body size influence zooplankton diversity in freshwaters; meanwhile, less is known about the composition and dynamic of the zooplankton community and their relationship with the trophic status in artificial water in semi-arid areas. The present study aimed to assess the physical–chemical parameters and to document the seasonal distribution of zooplankton species and their relationship with environmental factors and trophic state in the artificial freshwater lake JUST, in a semi-arid area. The high concentrations of nutrients and the trophic level index (TLI) classified the lake as eutrophic–hypertrophic. The zooplankton in the JUST lake were composed of twenty-six species, with eleven Rotifera, ten Copepoda, and five Cladocera. Copepoda was numerically the most abundant taxon, accounting for 64% of the total zooplankton abundance, in both seasons. However, the second most abundant taxon in summer was Rotifera (28.26%) while in winter it was Cladocera (25.88%). The community structure seemed to be influenced, most likely, by trophic state, phytoplankton abundance, water temperature, dissolved oxygen, and nutrient loading. The zooplankton were largely dominated by bioindicator species of high trophic levels. Zooplankton could be used as a tool to monitor the trophic state of the lake. For sustainable development, the introduction of phytoplanktivorous, aquaculture species, such as carp and koi, will strengthen the top-down control of the phytoplankton concentration, leading to a reduced trophic state.

Photoperiod effects in a freshwater community: Amphibian larvae develop faster and zooplankton abundance increases under an early-season photoperiod.

Organisms that shift their phenologies in response to global warming will experience novel photic environments, as photoperiod (daylength) continues to follow the same annual cycle. How different organisms respond to novel photoperiods could result in phenological mismatches and altered interspecific interactions. We conducted an outdoor mesocosm experiment exposing green frog (Rana clamitans) larvae, gray treefrog (Hyla versicolor) larvae, phytoplankton, periphyton, and zooplankton to a three-month shift in photoperiod: an early-season photoperiod (simulating April) and a late-season photoperiod (simulating July). We manipulated photoperiod by covering and uncovering tanks with clear or light-blocking lids to mimic realistic changes in daylength. We assessed amphibian life history traits and measured phytoplankton, periphyton, and zooplankton abundances. Green frog larvae and gray treefrog metamorphs were more developed under the early-season photoperiod. Gray treefrog total length was also reduced, but photoperiod did not affect green frog total length. Although phytoplankton and periphyton abundances were not affected by photoperiod, copepod nauplii were in greater abundance under the early-season photoperiod. Overall, this simplified aquatic community did not exhibit significant changes to structure when exposed to a three-month shift in photoperiod. Temperate amphibians that breed earlier in the year may develop faster, which may have long-term costs to post-metamorphic growth and performance. Asynchronous shifts in zooplankton abundances in response to altered photoperiods could subsequently affect freshwater community structure. While photoperiod has been shown to individually affect freshwater organisms, our study using replicated outdoor wetland communities shows that the comprehensive effects of photoperiod may be less important than other cues such as temperature and precipitation.

Microplastic pollution in Kolavai Lake, Tamil Nadu, India: quantification of plankton-sized microplastics in the surface water of lake.

The prevalence of microplastics (MP) (< 5 mm) in aquatic habitats has recently raised concerns owing to their influence on humans and aquatic organisms, as they absorb organic pollutants and pathogens from the surrounding media because of their higher surface-to-volume ratio. Freshwater systems are severely affected by the increased intake of discarded waste from diverse sources. This study focused on the microplastic-to-zooplankton ratio and its potential impact on the environment's food chain. The sampling sites of Kolavai Lake were divided into three zones (18 stations) to investigate the spatial distribution of microplastics and zooplankton biota. The average microplastic abundance was 6.1 ± 2.5 particles/L. Fourier transform infrared spectroscopy (FTIR) and SEM analysis were performed to understand the chemical composition and surface morphology of microplastics. Water samples collected along the Central and Southern Zones revealed a high abundance of microplastics, which might be due to anthropogenic activities. A negative correlation was observed between the abundance of microplastics and zooplankton. The microplastic-to-zooplankton ratio was found to range from 0.05 to 0.74. Furthermore, the impact of microplastics in the lake ecosystem was analysed using the size and shape descriptors for both zooplankton and microplastics. These findings suggest that microplastics built up in aquatic environments, particularly those with rich biota, could be a severe concern because of their capacity to infiltrate the food web.