Zooplankton Community Abundance Research Articles

Quantitative composition, distribution and abundance of zooplankton communities in relation to physico-chemical parameters from selected beaches of Alappuzha in Arabian Sea, southwest coast of India

Quantitative composition, distribution and abundance of zooplankton communities in relation to physico-chemical parameters from selected beaches of Alappuzha in Arabian Sea, southwest coast of India

Strong winds as driver of surf zooplankton abundance and composition in a temperate sandy beach

This study explores the effect of different wind events (direction and duration) on the surf zone zooplankton community in a temperate sandy beach. Samplings were realized on the surf zone of Pehuen Co sandy beach during 17 wind events from May 17th, 2017, to July 19th, 2019. Biological samples were taken before and after the events. The identification of the events was realized using recorded high-frequency wind speed data. General Linear Model (LM) and Generalized linear models (GLM) were employed to compare physical and biological variables. We observed that the wind direction unequally altered the ecosystem along with its duration, modifying the composition and abundance of zooplankton communities. Short-duration wind events were associated with an increment in the zooplankton abundances, being Acartia tonsa and Paracalanus parvus dominant. Within the short-duration cases, winds from the W sector were identified with the inner continental shelf species' presence, such as Ctenocalanus vanus and Euterpina acutifrons, and to a lesser extent, Calanoides carinatus, and Labidocera fluviatilis, together with surf zone copepods. Long-duration cases were associated with a significant decrease in the zooplankton abundance. Within this group, SE-SW wind events were identified with adventitious fraction taxa. Considering that the occurrence of extreme events is growing because of climate change, affecting the frequency and intensity of storm surges, the knowledge of the responses of biological communities to these events is necessary. This work provides quantitative evidence on a short-time scale of the implications of the physical-biological interaction during different strong wind cases in surf zone waters of sandy beaches.

Horizontal and Vertical Distribution and Abundance of Zooplankton around the Swatch-of-No-Ground of Northern Bay of Bengal

This study assessed horizontal and vertical distribution and abundance of zooplankton community in water samples collected from 26 stations at a depth of 0 to 250 m of the northern Bay of Bengal. A total of 55 zooplankton species were identified where Copepod was 72.41% and Ciliophora was 8.62%. Among the Copepod, 48%, 40% and 12% of species were Calanoid, Cyclopoid and Harpacticoid Copepod, respectively. This study also found 2 species of Decapod, 2 species of Rotifer, 2 species of Cladocera, 1 species of Chaetognatha and 1 species of Stomatopoda. Spatial distribution of zooplankton species was varied from station to station and cruise to cruise. Maximum 23,868 individuals of zooplanktons were recorded in cruise 2, whereas the lowest number (758 individuals) was found in cruise 4. Zooplankton abundance was ranged between 18 to 22,500 cells/L in all cruises, whereas the highest abundance was found in cruise 2 and the lowest was recorded in cruise 4. The highest abundance (37,310 individuals) was documented at surface water and the lowermost number of zooplankton (10 individuals) was recorded at 100 m depth. This study showed negative correlation between zooplankton abundance and water depth. The results of the current study might help to understand zooplankton abundance and distribution in the northern Bay of Bengal and will use as a baseline study for further research. The Dhaka University Journal of Earth and Environmental Sciences, Vol. 10(2), 2021, P 1-8

Current state of zooplankton diversity in the pelagic zone of Lake Tanganyika offshore of Bujumbura City

A study on the current state of zooplankton diversity in the pelagic zone of Lake Tanganyika along Bujumbura City was conducted from April to July 2020. The objective of the study was to assess zooplankton diversity for sustainable management of fishery resources and the conservation of this ecosystem. Two sampling sites were chosen. The first station was supposed to be polluted whereas the second one was considered as less polluted (or control). Zooplankton was collected with 50μm plankton net at different depths. The results obtained showed a total of 12 species identified in all the sampling stations among which, the copepods group was dominant while the rotifers group was found diversified with seven species (58.3%). The group of cladocerans represented by Moina macrocopa was identified for the first time in the pelagic zone. The calculation of the diversity index has reflected that the waters of Lake Tanganyika are classified into low level pollution category with a tolerable threshold. Therefore, the protection of Lake Tanganyika is necessary for sustainable fishery production and the future studies shall be carried out at several sites with annual sampling at a regular frequency to demonstrate the effect of seasons on the abundance of zooplankton communities.

Seasonal variability of gelatinous zooplankton during an anomalously warm year at Cabo Pulmo National Park, Mexico

The seasonal variability of gelatinous zooplankton (siphonophores, medusae, and thaliaceans) abundance was investigated at Cabo Pulmo National Park (CPNP) from weekly zooplankton samples collected throughout 2014. The Gulf of California had prolonged warming during 2009-2019, with 2014 as the anomalously warm year preceding El Niño 2015-2016 compared to the 2003-2020 SST time series. Gelatinous zooplankton accounted <1% of the entire zooplankton community abundance at CPNP during 2014, suggesting a low influence of predation pressure upon their zooplanktonic and micronekton preys. Siphonophores (57%), thaliaceans (42%), and medusae (1%) were present throughout the year. The abundance of gelatinous zooplankton had a significant negative association with sea surface temperature and a positive association with sea surface chlorophyll-a concentration and velocity and direction of the wind, increasing their abundance during October after the hurricane season. The gelatinous zooplankton species assemblage at the coastal CPNP was similar but less abundant than the gelatinous zooplankton species assemblage observed in the oceanic region of the southern Gulf of California during summer 2014. Tropical species Diphyes dispar, Abylopsis tetragona, Chelophyes contorta, and Thalia spp. numerically dominated the gelatinous zooplankton community associated with a regional heatwave period recorded during 2014. A high proportion of tropical zooplankton indicates that mesotrophic conditions sustain the current high biomass and diversity of nektonic and benthonic planktophagous fauna inhabiting CPNP. However, prolonged warming events might decrease zooplankton biomass in the southern region of the Gulf of California in the future.

Habitat utilization of a mesopredator linked to lower sea-surface temperatures & prey abundance in a region of rapid warming

Central place foragers rely on areas within a small range of their breeding grounds for chick provisioning. Therefore there exists a tight coupling between their breeding success and local bio-physical conditions. The effects of fine-scale variability in environmental parameters and resource distribution on the foraging behaviour of marine predators is studied in a region of rapid environmental change. Here we use little penguin habitat preference during two years of varying environmental conditions, to investigate the interactions between environmental variables, resource distribution and penguin habitat preference. Penguins were tagged with GPS devices during a marine heatwave event in 2016 and again in 2018 during comparatively cooler conditions. We found the distribution of penguins to be highly correlated with a fine-scale horizontal SST gradient feature, which appeared on the shelf in 2016 as a result of tropical water from the East Australian Current (EAC) interacting with cooler temperate water from southern Tasmania. Spatially, warmer SST anomalies corresponded to a lower probability of little penguins utilizing an area in both years. This was despite the much more uniform SSTs which were present during 2018. By modelling little penguin habitat preferences using two biological predictors, zooplankton community abundance as an indication of general resource distribution, and krill abundance - a prey species of little penguins - we show habitat preference to be only slightly more strongly driven by prey type, than by general resource distribution. The correlation between little penguin habitat preference and both zooplankton and krill abundance could indicate a plasticity in foraging behaviour which might be beneficial if lower-trophic level structure continues to change due to warming. In light of the continued warming predicted for this region, and the preference shown for cooler SSTs, this plasticity might be important under future resource climates.

Пространственная вариабельность и пищевые характеристики популяций желетелых в акватории Крыма в летний период

Численность, биомасса, размерная структура популяций желетелых хищников [медуза Aurelia aurita Linnaeus, 1758; гребневики Mnemiopsis leidyi A. Agassiz, 1865 и Pleurobrachia pileus (O. F. Müller, 1776)] и интенсивность питания двух видов (A. aurita и M. leidyi) исследованы в раннелетний период (июнь) 2016 г. на 45 станциях, охватывавших зону шельфа у берегов Крыма от м. Тарханкут до г. Керчи, а также на 3 станциях глубоководного района с координатами 44°23′N–45°5′N и 32°22′E–36°36′E. Сбор материала проводили вертикальными тралениями от дна (10–100 м) до поверхности на шельфовых станциях и от глубины с σt = 16,2 до поверхности ― на глубоководных, используя модифицированную сеть Богорова ― Расса с диаметром входного отверстия 80 см и ячеëй 500 мкм. Спектр питания определяли под микроскопом в лаборатории сразу после вылова животных, рассчитывая впоследствии суточные рационы и скорость выедания зоопланктона. Установлены пространственные различия в биомассе и численности отдельных видов: максимальная биомасса A. aurita, преобладавшей во всех районах, отмечена в Евпаторийско-Севастопольском районе и обусловлена большими скоплениями среднеразмерных особей новой генерации. Гребневик P. pileus доминировал по численности в районе халистазы. Пищевой спектр медуз был очень разнообразен и включал различные стадии Copepoda, Tunicata, Cladocera, а также меропланктонные организмы ― велигеров Bivalvia и Gastropoda. Халистатическая зона с большими глубинами характеризовалась максимальным количеством видов планктонных Copepoda в пище A. aurita. Среднесуточные рационы медуз, рассчитанные по содержанию пищи в гастральной полости и по времени переваривания, изменялись в широких пределах от района к району. Самыми низкими показатели были в Каркинитском заливе [(0,113 ± 0,10) мг C·экз.-1·сут-1, или (1,6 ± 2,18) % C тела], где большую долю пищи составляли водоросли Coscinodiscus granii Gough, 1905. Наиболее интенсивно питались животные в халистатической области [(0,687 ± 0,094) мг C·экз.-1·сут-1, или (56,2 ± 23,7) % C тела], в пище преобладали Calanus euxinus Hulsemann, 1991 и Pseudocalanus elongatus Boeck, 1865. Ни в одном из районов A. aurita не могла компенсировать затраты на дыхание за счёт потребления мезозоопланктона. Наибольший пресс на зоопланктон оказывала популяция медуз в Каркинитском заливе и в Евпаторийско-Севастопольском районе, хотя во всех исследованных районах её пресс был очень низок и не приводил к кардинальному сокращению численности зоопланктонного сообщества.

Fate of thiamethoxam in mesocosms and response of the zooplankton community

Thiamethoxam is a neonicotinoid insecticide that can reach wetlands in agro-ecosystems through runoff. The fate and effects of thiamethoxam on non-target organisms in shallow wetland ecosystems have not been well characterized. To this end, a mesocosm study was conducted with a focus on characterizing zooplankton community responses. A single pulse application of thiamethoxam (0, 25, 50, 100, 250, and 500 μg/L; n = 3) was applied to experimental systems and monitored for 8 weeks. The mean half-life of thiamethoxam among the different treatments was 3.7 days in the water column with concentrations of <0.8 μg/L in the majority of mesocosms by 56 days. Principal response curve analysis did not show any significant concentration-dependent differences in the zooplankton community among treatments over the course of the study. The minimum detectable difference (MDD%) values for abundance of potentially sensitive arthropod taxa (nauplius larvae, cyclopoid copepods) allowed the detections from controls as low as 42 and 59% effect, respectively. The MDD% values for total abundance of zooplankton (including the potentially less sensitive taxonomic group of Rotifera) allowed the detection from controls as low as 41% effect. There were no statistically significant differences in zooplankton abundance or diversity between control and treated mesocosms at the end of the study. There were also no statistically significant differences for individual taxa that were sustained between sampling points, or manifested as a concentration-response. We conclude that acute exposure to thiamethoxam at environmentally relevant concentrations (typically ng/L) likely does not represent a significant adverse ecological risk to wetland zooplankton community abundance and structure.

Role of Mesoscale Eddies in the Distribution Pattern of Zooplankton Standing Stock of Western Bay of Bengal During Spring Transition

Hydrography and spatial variability of zooplankton community during spring transition associated with Anti Cyclonic Eddies (ACE) and Cyclonic Eddies (CE) in the south western Bay of Bengal is investigated. In situ data collected on board FORV Sagar Sampada and satellite derived products were used for the study. Physical parameters such as temperature, salinity, and sigma-t in the surface waters showed typical spring condition with almost uniform distribution in the region. However, MLD, ILD and BLT showed noticeable variation between ACE and CE region. The satellite derived SSHA overlaid geostrophic current pattern indicates the piling up of surface water (20cm) in the region as the result of ACE centred at 13.25°N, 83°E and negative anomaly of 24cm associated with Cyclonic eddy at 15°N, 84°E. Observed cyclonic eddies (15°N, 84°E) are characterised by depressing temperature by about 7°C at 100m depth. The forcing mechanism of ACE identified as negative wind stress curl and associated westward propagating Rossby waves and formation of CE might be due to baroclinic instability developed by equator ward flow of fresh plume water from the north during the winter monsoon period. The biological response in the primary and secondary level to these phenomena explained based on chlorophyll-a distribution and mesozooplankton standing stock. Satellite imagery showed a uniform distribution of surface chlorophyll (< 0.1 mg m˗3) in the study region, except a slight increase in the CE. Subsurface Chlorophyll Maxima (SCM) observed at the base of the mixed layer showed the preference of phytoplankton community to the optimum environmental conditions. Mesozooplankton standing stock observed was relatively higher at CE and the centre of ACE. Enhanced phytoplankton standing stock due to the nutrient enrichment at CE favoured the abundance of zooplankton community. In contrast to the general trend, core of ACE supported higher zooplankton standing with dominance of copepods, chaetognaths, ostracods etc. Relatively higher biological production in the primary as well as secondary level during the present study was associated either with the extended winter production to the early months of spring or the characteristics like intensity, age, spatial variation of prevailing physical processes.

Role of macrophytes as microhabitats for zooplankton community in lentic freshwater ecosystems of South Korea

Zooplankton community distribution depends largely on the microhabitat characteristics of the water body. It has been reported that macrophytes provide microhabitats for zooplankton (e.g., space and food resources). To date, studies have focused on the overall influence of macrophytes on zooplankton (e.g., positive relationships with zooplankton diversity); however, the morphological characteristics of macrophytes have not been intensively studied. To fill this gap in knowledge, we investigated zooplankton abundance and diversity, macrophyte characteristics (types, dry weight, and species number), and physicochemical parameters (water temperature, dissolved oxygen, pH, conductivity, and chlorophyll a) by using the 1×1m quadrat method. We surveyed 164 wetlands in South Korea during spring (May to June), prior to the summer monsoon. Patterning zooplankton distribution was accomplished using a Self-organizing map (SOM). We used 34 input variables (zooplankton genera) to train the model. The distribution of five plant habit parameters (no plant, emergent, free-floating, floating-leaved, and submerged) was investigated with a trained SOM plane, by environment data masking. Based on a U-matrix, three clusters were identified from the model. Zooplankton assemblages were positively related to macrophyte characteristics (i.e., dry weight, species number, and plant type). In particular, free-floating plants supported rotifers, such as Testudinella, and cladocerans, such as Alona, Chydorus, Diaphanosoma, and Ilyocryptus (mostly epiphytic). Submerged plants were associated with planktonic rotifers, such as Filinia, Ploesoma, Synchaeta, cladocerans, such as Daphnia, and copepods, such as Eucyclops and Macrocyclops. On the basis of these results, we suggest that the microhabitat structure, created by macrophytes, is an important factor in determining the diversity and abundance of zooplankton communities, because the different species compositions of macrophytes support diverse zooplankton genera in these habitats. The results indicate that macrophytes are the key components of lentic freshwater ecosystem heterogeneity, and the inclusion of diverse plant species in wetland construction or restoration schemes will result in ecologically healthy food webs.

Zooplankton response to organic carbon level in lakes of differing trophic states

Key-words: zooplankton, Crustacea, total organic carbon, dissolved organic carbon, particulate organic carbon Water eutrophication is associated with an increase in the organic carbon content (both particulate and dissolved forms), which may affect the functioning of the zooplankton community. Mesotrophic and eutrophic lakes in the Masurian Lake District (Poland) were selected to evaluate the relationship between the organic carbon level and the zooplankton community. The lakes differed significantly in most environmental variables. RDA analysis was performed to evaluate the impact of environmental variables on zooplankton. The variables that significantly explained the variance in the zooplankton community abundance (Monte Carlo permutation test) included dissolved and particulate organic carbon, Secchi disc visibility, soluble reactive phosphorus and total nitrogen. The response of zooplankton to an increasing level of organic carbon is functional rather than quantitative. In the mesotrophic system, the results of the redundancy analysis indicated relatively strong positive relationships between dissolved organic carbon and zooplankton biomass, and negative correlations between chlorophyll a and zooplankton biomass. The above suggests that indirect organic carbon utilization by zooplankton could partly compensate for the poor feeding conditions of planktonic animals (decreasedphytoplankton availability). In the eutrophic lake, elevated organic carbon levels are partly limited by zooplankton, which is suggested by the positive relationship between particulate organic matter and the total zooplankton biomass (RDA results). The positive relationship between the biomass of copepods and organic carbon in particulate and dissolved forms implies that copepods benefit from the increased heterotrophic carbon flow that is activated in the eutrophic lake.

Composition and abundance of zooplankton community of an impacted estuarine lagoon in Northeast Brazil

Guaraíras Lagoon is a shallow coastal lagoon subject to intense human impacts, including shrimp aquaculture, urban expansion and agricultural activities, and is therefore vulnerable to eutrophication. With the aim of detecting the effects of human-mediated disturbance and environmental change in the lagoon, a spatial-temporal study was conducted in order to assess the actual ecological status of the lagoon and the species composition and density of the mesozooplankton, highlighting copepod assemblages. Algal biomass (chlorophyll-a) and total phosphorus concentration indicated that the lagoon is a meso-eutrophic coastal system in the inner part, and is oligotrophic in the areas influenced by the marine waters. High salinities were recorded in the lagoon, characterizing the lagoon as a coastal-marine ecosystem, rather than true estuarine. Mesozooplankton abundance fluctuated widely and showed marked spatial heterogeneity. The copepod assemblage was characterized by a coastal/estuarine group dominated by Oithona spp., Acartia lilljeborgi and Parvocalanus crassirostris in the inner areas of the lagoon, and a marine group characterized by the copepods Paracalanus quasimodo, Calanopia americana, Corycaeus (C.) speciosus and Monstrilloida in the area of marine influence. Thus, the spatial variability in the distribution of mesozooplankton species can be ascribed to the presence of a horizontal gradient of salinity and trophic conditions. Overall, the results showed that spatial variation in the water physicochemical characteristics of Guarairas Lagoon have significant effects on the structure and repartition of the mesozooplankton assemblages, which may potentially affect the functioning and biodiversity of this coastal ecosystem.

Complex interactions between regional dispersal of native taxa and an invasive species

In the event of an environmental disturbance, dispersal of native taxa may provide species and genetic diversity to ecosystems, increasing the likelihood that there will be species and genotypes present that are less vulnerable to the disturbance. This may allow communities to maintain functioning during a disturbance and may be particularly important when the perturbation is novel to the system, such as the establishment of an invasive species. We examined how dispersal of native species may influence crustacean zooplankton communities in freshwater lakes invaded by the invertebrate predator, Bythotrephes longimanus. Using large enclosures, we experimentally tested the effect of dispersal on zooplankton community abundance, richness, and composition in (1) a community invaded by Bythotrephes, (2) the same community with the invader removed, and (3) a community that was never invaded. Dispersal increased zooplankton community abundance and richness; however, these effects were usually only significant in the invader-removed treatment. Dispersal tended to make the invader-removed communities more similar to never-invaded communities in abundance, richness, and composition. Dispersal had little effect on zooplankton abundance in the invaded community; however, richness significantly increased, and the community composition changed to resemble a never-invaded community by the end of the experiment. Our results have implications for understanding the role of dispersal during transitory states in communities. Dispersal of native taxa may be particularly important during the period between the arrival and broad-scale establishment of Bythotrephes, as dispersal through space or time (i.e., from resting eggs) may rapidly increase zooplankton abundance when the invader is absent or in low abundances. Overall, our results suggest that communities with strong local predatory and competitive interactions may be closed to immigration from colonists, but that invasive species may alter the conditions under which species can establish. These results have implications for the interaction of native and invasive species across broad spatial scales, as regional dispersal of native taxa may forestall the local extirpation of native species. In particular, transient phases that result from variable persistence of invaders within habitats or across a region may permit native colonists to successfully establish, and thus increase local and regional resistance to future disturbance.

Zooplankton variability and climatic anomalies from 1994 to 2001 in the Balearic Sea (Western Mediterranean)

Abstract The long-term and seasonal changes in biomass and zooplankton abundance at a station off Mallorca Island (Balearic Sea) were studied in relation to the main physical and chemical conditions. The results are based on a total of 276 samples collected every 10 days during 8 years by means of oblique hauls from bottom to surface. At this neritic station (77-m depth) located in a hydrographic area between northern Mediterranean and Atlantic southern waters, salinity ranged from 37 to 38.4 psu and temperature from 13.4°C (February 1996) to 27.4°C (August 1998). With the exception of salinity, the other environmental parameters and the most abundant zooplankton groups showed irregular but seasonal cycles. Interannual variability was also observed, with higher zooplankton abundance during the cooler and more saline years when the influence of northern water was stronger. Zooplankton abundance decreased during a warm period in 1998. Copepods were the most abundant group (54%) and their abundance was significantly correlated with temperature (negatively) and salinity (positively). Here, we summarize the changes in the zooplankton community abundance and how hydrographic forcing and other climatic factors have changed during the period from 1994 to 2001 in the Balearic Sea (Western Mediterranean).

Zooplankton of subarctic Imandra Lake following water quality improvements, Kola Peninsula, Russia

The composition, species richness and abundance of zooplankton communities were studied in two highly contaminated areas: (1) mainly by heavy metals and other toxic and non-toxic matter, and (2) mainly by fine particles of nepheline and other minerals and organic matter, in the large, subarctic Imandra Lake (northwestern Russia), based on data collected between 1978 and 1990. Reduction in the relative abundance of the typical inhabitants of northern oligotrophic lakes and their substitution by tolerant-to-pollution, widely distributed, circumpolar species were the general trends for the communities. In both lake areas, water quality changes occurred in response to reductions in contamination of metals, mineral particles and organic matter in the mid 1980s. Water chemistry improvements, including decreased concentrations of pollutants, have resulted in partial recovery of zooplankton communities, increase in species richness, density of individuals, and shifts in composition of the dominance group. However, both lake areas are still contaminated and re-establishment of communities typical of a non-polluted lake did not occur between the mid 1980s and mid 1990s.

Planktivory by the predacious cladoceranBythotrephes longimanus: effects on zooplankton size structure and abundance

In order to study density-dependent effects of invertebrate planktivory, four different densities of Bythotrephes longimanus were inoculated into mesocosm enclosures with a mixed zooplankton community. Changes in size structure and abundance of zooplankton and phytoplankton communities were recorded over a period of 3 weeks. High densities of Bythotrephes were able to reduce total zooplankton abundance, which was mainly due to a decrease in the density of the relatively large species Holopedium gibberum. The density of the smaller species Bosmina longirostris was also reduced with increasing densities of Bythotrephes, whereas rotifer abundance remained largely unaffected. The mean size of Holopedium increased with increasing densities of Bythotrephes. Despite the decrease in total zooplankton biomass in high-Bythotrephes treatments, no effect of Bythotrephes density on primary producers was observed. Our experiment shows that predacious cladocerans may reduce macrozooplankton biomass, large as well as small species. Predation from invertebrate planktivores results in a zooplankton community consisting of larger individuals. Comparing our experimental densities with densities of Bythotrephes found in natural systems suggests that invertebrate planktivores may influence size structure and abundance of zooplankton communities even in lakes with planktivorous fish.