Total Zooplankton Density Research Articles

Applying various indices to evaluate the effects of fertilizer discharges on zooplankton biodiversity and water quality of Ismailia Canal, Egypt

One of the most useful water streams in Egypt is the Ismailia Canal. However, despite its significance, numerous factories discharge their waste into the canal, causing a drastic decrease in its water quality and fauna. In this respect, this study aims to evaluate the negative impact of fertilizer discharge on community structure, zooplankton biodiversity, and water quality in the Ismailia Canal. Four stations were selected, where the Canadian Water Quality Index and the Metal Indexwere used to determine the point source of contamination at each station. As revealed in the Canadian WQI results, Stations (3) and (4) have marginal water quality, but no metal pollution was shown in the Metal Index results of the study area. The Canonical Correspondence Analysis (CCA) was also applied. The zooplankton community structure and biodiversity were examined, where their total density recorded an average of 598,854 ind./m3. Nineteen zooplankton species—belonging to the groups: Rotifera, Cladocera, Copepoda, and Nematoda—were identified. Rotifera was predominant, representing 97.05% of the total zooplankton density. Although Station (3) had the highest diversity index, there was a special abundance of organic matter bio-indicators. That is why mandatory laws and management plans had to be enforced to mitigate the canal deterioration.

Spatial-Temporal Variations of Zooplankton in Relation to Selected Limnological Parameters: A Case of Kisii Town Wastewater Treatment Plant, Kisii County, Kenya

Zooplankton have been used as bioindicators of water quality. In this study, we assessed the spatial-temporal variations of zooplankton in the Kisii town wastewater treatment plant and how they were influenced by limnological parameters between May and August 2021. Triplicate zooplankton samples were collected monthly for laboratory analysis. Physical parameters were measured in situ using a YSI multi-parameter probe while triplicate wastewater samples were collected for chemical parameters analyses ex situ. Eleven (11) zooplankton species were identified belonging to three groups. Cladocera was represented by 5 species (45.5 %), Rotifera by 4 species (36.4 %), and Copepoda by 2 species (18.2 %). The total zooplankton density recorded was 515IndL-1 with the family Cladocera dominating (57.7 %) followed by Copepoda (22.8 %) then Rotifera (19.5 %) with the least number in the population density. The limnological parameters measurements indicate considerable wastewater pollutant removal during polishing but negatively influenced zooplankton diversity. Therefore, zooplankton can be used to monitor wastewater treatment progress.

Opening the black box of winter: Full‐year dynamics of crustacean zooplankton along a nearshore depth gradient in a large lake

AbstractPast studies of zooplankton seasonality in large temperate lakes have often neglected the winter period. Winter conditions are rapidly changing (e.g., reduced ice cover extent and duration, altered thermal and mixing regimes) in northern lakes, making it important to fill the existing winter knowledge gap. In this study, we sampled five stations in Lake Superior across a nearshore depth gradient through the full year to assess the phenology of crustacean zooplankton communities and the effect of environmental drivers on them. Across stations, zooplankton densities were the lowest in winter (0.9 ± 0.6 Ind. L−1) and highest in summer (14.2 ± 15.1 Ind. L−1). Zooplankton abundances and community composition were less seasonally variable at deeper stations compared to shallower and more terrestrially affected regions. Cladocerans were the dominant taxonomic group during the summer across all stations, while cyclopoid and calanoid copepods were more important during the fall, winter, and spring. Among feeding groups, herbivores were most abundant in summer while omnivores and carnivores dominated in winter. We found that water temperature and food availability were the main drivers of total zooplankton densities through the year and during the cold seasons, but the effect of these factors varied among the main taxonomic groups. Our study demonstrates seasonal and spatial variation in crustacean zooplankton and environmental parameters, with the highest fluctuation at shallower stations. This study offers new information on seasonal crustacean zooplankton dynamics and contributes to understanding the effects of climate change on large lake ecosystems.

Fish and Zooplankton Community Responses to the Cessation of Long-Term Invasive Eurasian Watermilfoil (Myriophyllum spicatum) Chemical Treatments in a North-Temperate, USA Lake

2,4-Dichlorophenoxyacetic acid (2,4-D) is commonly used to control invasive aquatic macrophytes, including Eurasian watermilfoil (Myriophyllum spicatum) (EWM). Potential influences of 2,4-D on non-target organisms are poorly understood; however, research has suggested the possibility of lethal effects on certain fish species. Lake Ellwood, Wisconsin was treated with 2,4-D to control EWM annually during 2003–2012. Fish surveys following treatment revealed natural recruitment failures of several regionally thriving species, including largemouth bass (Micropterus salmoides) and bluegill (Lepomis macrochirus). We hypothesized that these species had been negatively influenced by the chemical treatments. We monitored the post-chemical treatment fish community and aquatic ecosystem for responses during 2013–2019. Similar data were collected from Cosgrove (EWM absent) and Seidel lakes (EWM present, no chemical treatment) as reference systems. Limnological and submersed aquatic vegetation conditions did not change on Lake Ellwood post-chemical treatment. Total zooplankton density increased immediately post-chemical treatment on Lake Ellwood and then stabilized, whereas total zooplankton density did not change on the reference lakes over time. Analyses indicated immediate increases in recruitment post-chemical treatment for largemouth bass, smallmouth bass (Micropterus dolomieu), bluegill, and yellow perch (Perca flavescens). Back calculation of year class strength confirmed failures occurred during treatment for northern pike (Esox lucius), largemouth bass, bluegill, and black crappie (Pomoxis nigromaculatus). Our results provide evidence to suggest long-term 2,4-D treatments may negatively influence fish through lethal and sublethal mechanisms. Thus, there remains a critical need for directed research on whole-lake herbicide treatment side-effects.

Relationship between physicochemical parameters and the abundance of zooplankton in Lake Mweru-Wantipa, Zambia

Abstract. Anamunda A, Lamtane HA. 2022. Relationship between physicochemical parameters and the abundance of zooplankton in Lake Mweru-Wantipa, Zambia. Intl J Bonorowo Wetlands 12: 33-40. This study aimed to assess the abundance of zooplankton and their relationship with physicochemical parameters within Lake Mweru-Wantipa, Zambia. A National Park borders the lake on one side and settlements on the other, so four sampling stations were selected, two on each side of the lake. Five physicochemical parameters, including temperature, turbidity, salinity, pH, and dissolved oxygen, were measured monthly using portable instruments concurrently with a collection of duplet zooplankton samples at each sampling point at depths between 0.1m and 0.5m. All physicochemical parameters were significantly different between the two sites (p<0.05) apart from temperature and pH. A total of 13 genera of zooplankton were identified, belonging to four groups, namely, rotifers, cladoceran, copepods, and ostracods. The cladoceran had the highest number of species (6), followed by copepods (4) in both sites. However, the copepods had the largest contribution in abundance in both sites. The diversity was high in settlement areas, but the National Park had higher species richness. There was a significant difference in species diversity between the two sites (t=3.96; p=0.001). The most abundant group was the cyclopoid on both sides of the lake, followed by the Moina on the settlement site and the Daphnia sp. on the National Park site. The densities of Molina, Simocephalus, Ceriodaphinia, and Cypris were significantly different between the two sites (p<0.05). Except for copepods, all groups were significantly different between the two sites (p<0.05). Generally, the total zooplankton density was not significantly different between the two sites (t=0.73; p=0.06). The results showed that the zooplankton abundance was influenced by turbidity in settlement areas and pH in National park areas.

Comparisons of Zooplankton Community Structure between with- and without- Pesticide Applications on Rice Fields

Herbicide usage in rice fields over time may have a direct and indirect influence on the biodiversity of the fields. The impacts of herbicide usage on non-target organisms were assessed by examining the species richness and zooplankton density of two rice fields. One was 2.08 hectares in size and had been treated with pesticides during the sampling year (RF-PA). The second field, measuring 1.76 hectares, had received no pesticide treatment (RF-NPA). Every two weeks, zooplankton was quantitatively collected from ten sampling sites in each field. At each station, 20 L of measured water was filtered through a plankton net with a mesh size of 20 µm and preserved in 1% Lugol’s solution. The results revealed that RF-NPA and RF-PA had 112 and 88 species of zooplankton, respectively, with an abundance-based Jaccard index (Jabd) of 0.438. The total zooplankton density in RF-NPA was 24.4 ind./L, significantly higher than the 16.6 ind./L in RF-PA (p < 0.001). The Shannon-Wiener diversity index (H’) and evenness (J) were highest in RF-NPA at the second sampling (3.45 and 0.75, respectively). These results indicate that glyphosate application affects the diversity of species and density of zooplankton in rice fields.

Response of Zooplankton Size Structure to Multiple Stressors in Urban Lakes

Urban lakes are important environmental assets that contribute significant ecosystem services in urbanised areas around the world. Consequently, urban lakes are more exposed to anthropogenic pressures. Zooplankton communities play a central role in lake processes and, as such, are very sensitive to the impacts of human activities both through in-lake and catchment processes. Understanding their ecological function in urban lakes and how they respond to urbanisation is essential for environmental sustainability. In this study, we investigated the reliability of zooplankton size structure as indicators of anthropogenic stressors in urban lakes. We examined the relationship between environmental variables and zooplankton community size spectra derived as mean body size, density, and biomass. Our study showed that the overall mean body size was within the small size group ranged from 416 to 735 µm equivalent spherical diameter (ESD). Despite no significant difference in total zooplankton density between lakes, there was variability in the total density of the five different size classes. Total biomass was characterised by a significant proportion of size >750 µm. As the specific parameter of normalised biomass size spectra (NBSS), the slopes of the NBSS varied from moderate (−0.83 to −1.04) for a community with higher biomass of the larger size zooplankton to steeper slopes (from −1.15 to −1.49) for a community with higher biomass of smaller size. The environmental variables, represented by total phosphorus (TP) and chlorophyll a (chl-a), had a strong effect on zooplankton biomass and NBSS, where TP and chl-a were significantly correlated with the increase of total biomass and corresponded well with a less negative slope. Our results indicated that the community metric was sensitive to nutrient input and that size-based metrics have the potential to serve as key indicators for the management of urban lakes.

Diversity and Abundance of Zooplankton in River Aswa in Uganda

Zooplankton community constitutes one of the keystone organisms that are crucial in understanding aquatic ecosystem responses to environmental distresses. The objective of this study was to contribute to the understanding of zooplankton ecological conservation status and assessment of potential impacts of the proposed Hydropower plant on the zooplankton community in River Aswa, Nwoya District, in Uganda. Baseline information on aquatic micro-invertebrate diversity, abundance and distribution along the affected river section was generated. Two copepods and four species of rotifers were recorded. The Intake site had the highest diversity (six species) while Powerhouse hadfour species. Of the species encountered, Keratella tropica registered the highest abundance—1,025 and 732 individuals m-2 at the Powerhouse and Intake sites, respectively. Total zooplankton densities were comparable with Intake (2,773 individuals m-2) and Powerhouse (2,311 individuals m-2). The zooplankton taxa do not appear in the IUCN Red List in the Catalogue of Life. Therefore, the proposed construction of a hydropower plant may not pose zooplankton conservation problems.
 Keywords: Biodiversity, Zooplankton, invertebrates, hydropower, River Aswa.

Seasonal Variation of Zooplankton Density and Physicochemical Parameters of A Perennial Freshwater Body, Samudrabundh of Joypur, Bankura, West Bengal, India

Water is the most essential and vital component required for the survival of all organisms in this earth. The physico-chemical and biological characteristics of a water body determine its efficacy for the production of plankton especially the zooplankton. Zooplankton are the most important primary consumer of aquatic food chain which in turn influence the productivity of finfishes in an aquatic body .The present study is primarily based on assessment of seasonal density and diversity as well as the physico-chemical condition of Samudrabundh, of Joypur block of Bankura district, West Bengal. Such type of assessment on this water body has not been done before this.. The study was carried during March.2019 to February, 2020. The water quality parameters which were used for study were temperature, PH, Dissolved Oxygen (DO), Free carbon dioxide (CO2),Chloride, salinity, alkalinity and total hardness. A total of 26 taxa of zooplankton were recorded. Out of which 8 sp ecies comprises of Rotifera, 05 species of Copepoda, 10 species of Cladocera and 03 species of Ostracoda. The total zooplankton density ranges from 756 (Ind/L) to 957 (Ind/L) which is quiet lower than the desired value required for good fish culture. The study concludes that the water body is of soft water type and medium productive in nature.

Effect of salinity on growth, survival, and proximate composition of Macrobrachium rosenbergii post larvae as well as zooplankton composition reared in a maize starch based biofloc system

Improved sustainable aquaculture can be achieved through biofloc technology (BFT) by reducing feed input and water use. Although BFT is considered a viable culture strategy to various crustaceans, including Macrobrachium rosenbergii, the influence of salinity has not received much attention. The aim of this study was to investigate the effects of increasing salinities of BF0, BF5, BF10, and BF15 PSU on M. rosenbergii post larval (PL) growth performance and proximate composition in a biofloc system as well as water quality, total bacteria and Vibrio spp. and zooplankton abundance/composition. A carbon: nitrogen ratio was maintained at 10 by maize starch additions. Each tank contained 500 prawns (42.5 ± 5.6 mg) in triplicate. Growth was similar (p > 0.05) in BF0, BF10 and BF15, but was significantly lower in BF5. The best FCR was observed in BF15 and BF10. PL survival was significantly (p < 0.05) higher at BF10 and BF15 than in BF5 and BF0. Higher gross return, net return and benefit cost ratio were obtained (P < 0.05) at BF10 and BF15 than in BF0 or BF5. Whole-body crude protein was significantly elevated in BF15 than all others. Nitrate-N, pH, floc volume and VSS were unaffected by salinity (p > 0.05); however, at weeks 3 and 4, ammonia-N was higher in BF0 (p < 0.05). Total bacteria density and Vibrio spp. were significantly (p < 0.05) higher at BF10 and BF15 than in BF5 and BF0. Total zooplankton density was higher (P < 0.05) at BF15. This study demonstrates that a salinity of 15 PSU improved survival, production economics and protein content of M. rosenbergii, which was likely linked with greater zooplankton abundance in the biofloc-based system.

El Zooplancton de dos lagos someros del sur de la Formación Meauco (ProvincIa de la Pampa, Argentina)

The Meauco Formation, a dune region of the central Pampa province, has numerous shallow lakes. Although there is hydrological information about them, it is very scarce about their limnological characteristics. The objectives are to know the physical-chemical and zooplankton parameters of two nearby shallow lakes, with and without fishes: Santa Isabel I (SI I) and Santa Isabel II (I II) respectively, and determine the influence of zooplankton on phytoplankton biomass and transparency. It was sampled during 2018 and 2019. In both the mean salinity were less than 1g.L-1 and the Secchi disk depth was around 0.45m. The chlorophyll concentrations varied between 9.32 and 11.63 mg.m-3. Seven cladocerans, 4 copepods and 20 rotifers were recorded. Most of the taxa were shared by both lakes, however, 20 rotifers were recorded in SI I and 13 in SI II. The total zooplankton density did not differ, but SI I had greater abundance of rotifers (69% of total) and SI II of crustaceans (72%). The presence of fish influences the zooplankton composition but its small size, even in the absence of fish, makes it have little influence on the phytoplankton; therefore, no differences were found in the transparency and phytoplankton biomass of both lakes.

Seasonal variation of the zooplankton community of Gamak Bay, Korea

The seasonal variation in the zooplankton community and hydrographic conditions were examined in three regions (inner, central, and outer regions) of Gamak Bay, Korea. Zooplankton samples were collected over a period of 12 months from January to December 2006. The hydrographical parameters of temperature, salinity, chlorophyll-a concentrations, dissolved oxygen, and chemical oxygen demand were measured. The total zooplankton density varied from 411 to 58,485 ind. m-3, with peaks in early summer. A total of 65 taxa accounted for approximately 86.9% of the annual mean zooplankton density: Noctiluca scintillans (30.9%) Paracalanus parvus s. l. (24.3%), Acartia omorii (11.9 %), Eurytemora pacifica (5.7%), cladocerans (4.1%), cirriped larvae (3.8%), Oithona similis (3.7%), and Pseudevedne tergestina (2.5%). Copepods dominated numerically throughout the year and comprised 54.3% of the total zooplankton. Most of the dominant copepods showed a well-defined seasonal pattern. The density and diversity of zooplankton in Gamak Bay were influenced by the hydrographic environment that was subject to significant spatial and temporal variations. Multivariate statistics showed that seasonal temperature was the most significant predictor of zooplankton taxa, density, and diversity, as well as the density of dominant taxa. Our results suggest that fluctuations in the zooplankton populations, particularly copepods, followed progressive increments in the temperature and COD concentrations.

The Zooplankton composition and surface water quality in some watershed around the aquaculture areas at the Ben Tre province

The research was conducted in 3 districts: Binh Dai, Ba Tri and Thanh Phu in Ben Tre province in September 2017 (wet season) and April 2018 (dry season). The study recorded 63 taxa of zooplankton belong to 40 genera, 7 classes, and six groups: Protozoans, Rotifers, Cladocerans, Copepods, Ostracods and larvae (of shrimp and crab). Rotifers dominated the local zooplankton quantitatively, with 55,56% of the total organisms. Total zooplankton densities oscillated from 120 – 23 304 ind.m-3 during the wet and dry season. The total zooplankton in the wet season is higher in the dry season. The result of the research showed that zooplanktons were affected by season and salinity. The water quality indices (pH, temperature, salinity, TDS, DO, NO3-, NH4+, PO43-) were under limitation to use for aquaculture activities, aquatic organism conservation, and daily living. The Shannon – Wiener index (H’) fluctuated from 0,51 to 2,02, the Simpson index fluctuated from 0,15 to 0,8, the Pielou index fluctuated from 0,23 to 0,94. The bioindex showed that the water bodies are polluted (from α, β – mesosaprobic level to polysaprobic level). Our results indicated that there was a difference between water environmental parameters and zooplankton communities among seasons and stations. Therefore, it is necessary to combine these two indicators for better accurate results in water quality assessment.

Zooneuston and zooplankton abundance and diversity in relation to spatial and nycthemeral variations in the Gulf of Aqaba and northern Red Sea

Zooplankton and zooneuston observations were made at seven stations (four from the Gulf of Aqaba and three from the northern Red Sea), during September and October 2016. The main objective of this study was to assess the variability of nycthemeral fauna in relation to the sampling methods using two different types of nets namely, WP2 net and Neuston net along the two study sites, i.e., the Gulf of Aqaba and the northern Red Sea. Zooplankton was sampled vertically using a standard WP2 net from a depth of 200 m to the surface, whereas zooneuston was made using a standard Neuston net from a depth of 0–10 cm of the water surface. Total zooplankton density was maximum during night time ((617.83 ± 201.84) ind./m3) at the Gulf of Aqaba and total zooneuston was maximum during night at the northern Red Sea ((60.94±29.48) ind./m3), respectively. The most abundant taxa were Copepoda, Gastropoda, Bivalva, Chaetognatha, Tunicata and Ostracoda. The abundance was almost 50% higher at night time at both the Gulf of Aqaba and the northern Red Sea. Overall, 30 taxa covering 10 phyla and 27 taxa covering 8 phyla were recorded in the Gulf of Aqaba and the northern Red Sea.

Effects of Anthropogenic Activity on Coral Reef Fish Assemblages of the Northern Persian Gulf

The present research was performed to investigate the effects of anthropogenic perturbation on spatial variations of coral reef fish distribution and abundance on a coral reef area in the northern Persian Gulf. For this purpose, wintertime and summertime coral reef fish assemblages along with some environmental parameters were assessed at three different sites along a presumed anthropogenic disturbance gradient. Results indicated that the alterations in substrate rugosity and orthophosphate concentration could be responsible for spatial variations in family composition and fish assemblage structure in winter. On the other hand, live coral cover, total zooplankton density, and TDS were identified as the most important variables regulating spatial variability of fish assemblages in summer.

Does salinity change determine zooplankton variability in the saline Qarun Lake (Egypt)?

Zooplankton and 14 abiotic variables were studied during August 2011 at 10 stations in Lake Qarun, Egypt. Stations with the lowest salinity and highest nutrient concentrations and turbidity were close to the discharge of waters from the El-Bats and El-Wadi drainage systems. A total of 15 holozooplankton species were identified. The salinity in Lake Qarun increased and fluctuated since 1901: 12 g/L in 1901; 8.5 g/L in 1905; 12.0 g/L in 1922; 30.0 g/L in 1985; 38.7 g/L in 1994; 35.3 g/L in 2006, and 33.4 g/L in 2011. The mean concentration of nutrients (nitrate, nitrite and orthophosphate) gradually increased from 35, 0.16 and 0.38 µg/L, respectively, in 1953–1955 to 113, 16.4, and 30.26 µg/L in 2011. From 1999–2003 some decrease of species diversity occurred. Average total zooplankton density was 30 000 ind./m3 in 1974–1977; 356 125 ind./m3 in 1989; 534 000 ind./m3 in 1994–1995; from 965 000 to 1 452 000 ind./m3 in 2006, and 595 000 ind./m3 in 2011. A range of long-term summer salinity variability during the last decades was very similar to a range of salinity spatial variability in summer 2011. There is no significant correlation between zooplankton abundance and salinity in spatial and long-term changes. We conclude that salinity fluctuations since at least 1955 did not directly drive the changes of composition and abundance of zooplankton in the lake. A marine community had formed in the lake, and it continues to change. One of the main drivers of this change is a regular introduction and a pressure of alien species on the existent community. Eutrophication also plays an important role. The introduction of Mnemiopsis leidyi, first reported in 2014, may lead to a start of a new stage of the biotic changes in Lake Qarun, when eutrophication and the population dynamics of this ctenophore will be main drivers of the ecosystem change.

Vertical distribution of zooplankton in Lake Nasser

The composition and distribution of zooplankton communities in three depths (surface, 10–5m and 20–15m depths) along main channel of Lake Nasser were studied in 2013. The density of total zooplankton was increased to maximum during winter and autumn at surface water (39,362 and 63,100Ind.m−3, respectively) and gradually decreased with depth until attaining the lowest average density at 20–15m (12,460 and 8976Ind.m−3). During spring and summer, zooplankton was irregularly distributed through the water profile, where the highest average density was recorded at 10–5m depth (66,007 and 66,734Ind.m−3). Copepoda was the dominant zooplankton group at all depths, it represented about 70–76.2% of the total zooplankton count. Cladocera formed about 13.4%, 14.5% and 11% of total zooplankton density for surface, 10–5m and 20–15m depth. It was decreased with increasing depth during winter and autumn; however it attained its maximum density at 10–5m depth during spring and summer. Rotifera average density decreased with increasing depth. The dominant zooplankton species inhabiting Lake Nasser were strongly temperature-dependent. The study recommends the introduction of some pelagic fish species to consume the high persistence of zooplankton community at the upper 10meters of water column.

Seasonal trends in physico-chemical parameters and zooplankton in a freshwater reservoir of Dejla Dewada, Khargone, M.P.

Seasonal variation in physico-chemical and zooplankton communities of Dejla Dewada Reservoir (D.D.R.), West Nimar district (Khargone) was studied during October 2009 to September 2010. Protozoa, Rotifera, Copepoda, Cladocera and Ostrcoda were found dominated zooplanktonic groups. The total zooplankton density ranged between 879 unit/L to 2980 unit/L.The composition of zooplankton was found as Protozoa &gt;Rotifera&gt;Copepoda&gt;Cladocera&gt;Ostracoda.

Beyşehir Gölü Zooplankton Türlerinin Aylık Dağılımı

In this study, Lake Beysehir water and zooplankton samples were taken in 8 different stations once a month, between May 2009-April 2010. 37 taxa of Rotifera, 5 taxa of Copepoda, 4 taxa of Cladocera and 1 taxa belonging to Bivalvia and a total of 47 species have been identified. The lake-wide total zooplankton density; Rotifera of 95.45%, Cladocera of 3.66%, Copepoda of 0.89% and belong to Bivalvia of <0.01% calculated. Zooplankton was represented by a large portion of micro-zooplankton. Large zooplankter zooplankton such as Daphnia that water filtration capacity is constituted a very small portion

Structure, abundance and biomass size spectra of copepods and other zooplankton communities in upper waters of the Southwestern Atlantic Ocean during summer

Little attention has been paid to small copepods and other zooplankton inhabiting pelagic ecosystems of the Southwestern Atlantic Ocean under the influence of the Antarctic Circumpolar Current circulation, despite their important role in the trophic chain and fisheries. This study gives a synoptic view (January 2001) of the micro and mesoplankton size fractions and normalized biomass size spectra (NBSS) in upper waters of five different ecological domains (shelf and oceanic Subantarctic and Antarctic waters) including the Brazil–Malvinas confluence (BMC). Copepods were always the main component of the zooplankton; the <300-µm fraction represented between 70 and 99% in terms of numbers and from 20 to 88% in terms of biomass. Other zooplankton contributed with <40% to total zooplankton densities, though showing some biomass peaks (>50%). Chlorophyll a, sea surface temperature and salinity were the environmental variables that best explained the distribution trend of zooplankton, mainly that of the <300-µm fraction. For all the domains, NBSS revealed flat slopes (−0.6 to −1), suggesting a higher proportion of large organisms than expected at equilibrium. A dome-shape feature was detected in the BMC. Total biomass and trophic levels of the system were related to the composition of the community and the hydrological conditions of the domains covered.