Zooplankton Density Research Articles

Does winter application of road salt affect zooplankton communities in urban ponds?

Road salt (NaCl) is commonly used as a deicer during winter to improve road safety, resulting in freshwater salinization. Such elevated chloride concentrations may have a strong effect on zooplankton, which are key elements in freshwater food webs. The aim of this study was to investigate the effect of chloride ion concentration and inter-pond environmental variability on zooplankton density in four urban ponds over 3 years differing in winter conditions. Analysis of variance showed significant differences in chloride ion concentration and zooplankton density regarding study year and ponds. Redundancy analysis of column water data showed that both the environmental variables (including chloride ion concentration) and the pond location significantly contributed to the model explaining the variability in zooplankton densities. However, the environment variable (referring to the environmental variables) had a smaller contribution (11%) than the POND variable (related to the spatial configuration of the ponds), which contributed 62%, indicating that the dynamics of zooplankton density depended primarily on ecosystem characteristics. Even so, although chloride content was not the main determinant of zooplankton density, their presence in aquatic ecosystems and potential interactions with other types of pollutants could have negative biological and ecological effects.

The impact of cottonseed meal condition on water quality, zooplankton densities, and sunshine bass production when used as an organic fertilizer in ponds

AbstractObjectiveCottonseed meal is applied to sunshine bass (female White Bass Morone chrysops × male Striped Bass M. saxatilis) fry rearing ponds as an organic fertilizer to stimulate plankton development. The efficacy of cottonseed meal as a fertilizer following long‐term storage and degradation is unknown. The use of degraded and undegraded cottonseed meal were compared during the production of sunshine bass fingerlings in lined 0.4‐ha ponds.MethodsFilling ponds were fertilized repeatedly between 13 days before and 6 days after fry stocking, and water quality, zooplankton, and 41–48‐day fingerling production were monitored. Adequate phytoplankton and zooplankton densities were maintained using cottonseed meal of both conditions.ResultCottonseed meal condition had no significant impact on any fish production metric. The degraded cottonseed meal appeared to release nitrogen more readily as indicated by higher prestocking NH3‐N concentrations. Higher nutrient availability likely stimulated primary productivity at a faster rate, leading to higher dissolved oxygen, pH, and zooplankton densities during the first half of the pond cycle. The ponds fertilized with degraded cottonseed meal required more intensive water quality management to maintain adequate dissolved oxygen and pH for sunshine bass fry. However, poststocking water quality parameters were within species tolerance ranges.ConclusionThe study confirmed that degraded cottonseed meal can be used as an organic fertilizer in sunshine bass fry rearing ponds without compromising fingerling production, provided ponds are managed appropriately.

Studying the Metazoan Zooplankton Community Characteristics and Evaluating the Water Quality Based on the Ecological and Functional Zones in Gaoyou Lake

To study the metazoan zooplankton community structure and water quality, we investigated the amount of metazoan zooplankton and the water quality in Gaoyou Lake from January to December 2022. Furthermore, we also evaluated the multi-index and nutritional status of Gaoyou Lake using the comprehensive nutritional status index of water quality, dominant population composition of the metazoan zooplankton, B/T index, and Shannon–Weaver diversity index based on the situation of each ecological and functional zone. The results indicated that the metazoan zooplankton of Gaoyou Lake included 21 families, 31 genera, and 63 species. The rotifers had 8 families, 16 genera, and 34 species, accounting for 53.9% of all species. The cladocerans had 6 families, 7 genera, and 16 species, which accounted for 25.4% of all species. The copepods had 7 families, 8 genera, and 13 species, that accounted for 20.7% of all species. The density and species of small metazoan zooplankton (rotifers) had a higher proportion than large metazoan zooplankton (crustaceans). The average annual metazoan zooplankton density was 1595.7 ind./L, the average annual biomass was 4.31 mg/L, the average annual total nitrogen (TN) was 1.101 mg/L, and the average annual total phosphorus (TP) was 0.082 mg/L. The TN and TP of the Gaoyou Lake were over the standard. The comprehensive nutritional status indices of the water quality in the entire lake and the ecological and functional areas were consistent with the metazoan zooplankton evaluation results, which determined that Gaoyou Lake showed mild eutrophication.

Climate and juvenile recruitment as drivers of Arctic cod (Boreogadus saida) dynamics in two Canadian Arctic seas

Arctic cod (Boreogadus saida) is the most abundant forage fish species in Arctic seas and plays a pivotal role in the transfer of energy between zooplankton and top predators. The dominance of Arctic cod and the Arctic’s relatively low biodiversity interact such that changing population dynamics of Arctic cod have cascading effects on whole Arctic marine ecosystems. Over the last decades, warming in the Arctic has led to a decline in Arctic cod populations in the Barents Sea, but in the Canadian Arctic these conditions have been correlated with up to a 10-fold higher biomass of age-0 Arctic cod at the end of summer. However, whether this enhanced larval survival with warmer waters endures through age-1+ populations is unknown. A better understanding of spatial variation in the response of Arctic cod populations to environmental conditions is critical to forecast future changes in Arctic ecosystems. Here, we rely on a 17-year time series of acoustic-trawl surveys (2003–2019) to test whether ice-breakup date, sea surface temperature, zooplankton density, and Arctic climate indices during early life stages affect the subsequent recruitment of age-1+ Arctic cod in the Beaufort Sea and Baffin Bay. In the Beaufort Sea, the biomass of age-1+ Arctic cod correlated with both Arctic Oscillation indices and age-0 biomass of the previous year. In Baffin Bay, the biomass of age-1+ Arctic cod correlated with previous-year North Atlantic Oscillation indices and the timing of ice breakup. This study demonstrates that climate and environmental conditions experienced during the early life stages drive the recruitment of the age-1+ Arctic cod population and helps to quantify spatial variation in the main environmental drivers.

Phytoplankton-zooplankton coupling in a cascade of hypertrophic fishponds

In Central Europe, a significant proportion of shallow lake ecosystems are represented by artificial fishponds, where phytoplankton and zooplankton are an essential part of the food web. Owing to their high fish stocks and intensive fishery management, most fishponds are now eutrophic or hypertrophic, which has had clear impacts on plankton assemblages. To obtain a better understanding of phytoplankton-zooplankton coupling in fishponds, this study examines their ecological relationships in a cascade of three small fishponds over two subsequent years. In all, 133 phytoplankton taxa were recorded, mostly chlorophytes, diatoms and euglenophytes, and 60 zooplankton taxa. Multivariate analysis revealed dissolved oxygen content, dissolved inorganic nitrogen and biochemical oxygen demand as the main factors influencing phytoplankton biomass, while the most significant environment variables affecting zooplankton composition were dissolved oxygen, phosphate concentrations and conductivity. Co-correspondence analysis revealed a significant relationship between phytoplankton and zooplankton density, with cross-correlations from 76% to 87% within the first four axes. Such a high cross-correlation denotes a strong relationship between phytoplankton and zooplankton, even within the hypertrophic conditions determining fishpond ecosystems.

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.

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.

Studies on plankton community and physico-chemical parameters of Elechi Creek, Eagle Island, Port Harcourt

Studies on the plankton communities and physico-chemical characteristics of Elechi Creek were carried out for six months, from January to June. Fourteen physico-chemical parameters were evaluated, and monthly plankton alteration was investigated. Water quality samples and plankton analyses were obtained simultaneously. Water temperature was in the range of (29.4–35.5⁰C) across the (3) study locations. The results revealed no spatial dissimilarity (P˃0.05) of all physicochemical factors while results of the monthly variations test showed significant elevations (P˂0.05) for some parameters between (April and June), except for Turbidity, Nitrate, pH, Sulphate and Chloride. The mean concentration levels in total hardness (1600 mg/L), chloride (1075.8 mg/L) and sulphate (621.6 mg/L), were found considerably above the acceptable levels. Most plankton showed negative changes subsequent to these elevations. Phytoplankton identified comprised two families, of which Bacillariophyceae (diatoms) were higher followed by Cyanophyceae. Bacillariophyceae, cell density (46 cells L-1) contributed the highest (80.7%) sum phytoplankton cell–density while Cyanophyceae had (11 cells L-1) contributing (19.3%). The zooplankton density was from (17 L-1 - 1190 L-1). Copepoda recorded the utmost percentage population, contributing (91%) zooplankton, followed by Cladocera (4.8%), Crustaceae (2.9%) and most reduced (1.3%) contribution by Rotifera. Monthly variations of Plankton density showed that most families recorded higher density during the wet months (April–June). The occurrence of these factors and conditions in Elechi Creek underscore pollution therefore, aquatic organisms from such water are almost unsafe for food. Hence, standard checking of the creek is advocated to ensure seafood safety.

Influence of extreme cold and warm oceanographic events on larval fish assemblages in the southern region of the California Current

The larval fish community in the southern region of the California Current (CC) was analyzed to test the hypothesis of a northward expansion of tropical species for the summer-fall seasons of La Niña (LN) 2010-2011, The Blob 2014, and El Niño (EN) 2015-2016. Interannual temperature anomalies (-5 to +2°C), as well as decreases in chlorophyll a (68%) and zooplankton density (71%), resulted in dramatic changes in the larval fish community, such as an 82% decline in larval fish density, unprecedented for the CC. Tropical species richness increased in the north by 46%, while temperate species decreased by 65% in the south. Mesopelagic species richness and relative abundance increased in the north by 53 and 92%, respectively. In the south, the species richness of the demersal component increased up to 39%, although demersal species were co-dominant with mesopelagic species, accounting for 47% of the relative abundance compared to 49% for the mesopelagic species. The magnitude of the changes in the community was unparalleled when compared with other warming events, such as EN 1983-1984 or EN 1997-1998. The differences were probably related to the presence of The Blob, which favored the transport of oceanic species into the neritic region of the CC. In both cold and warm years, fronts and mesoscale eddies in the middle part of the Baja California Peninsula represented barriers to the latitudinal distribution of species, even during intense tropicalization processes, since no latitudinal extensions in species distribution occurred.

Zooplankton size-structure dynamics of a lowland tropical floodplain lake

Floodplains are highly complex ecosystems representing high biodiversity and conservation values, but they are also one of the world’s most threatened ecosystems due to extensive development and anthropogenic activities. Lake Tempe is a lowland riverine floodplain lake in Sulawesi Island, Indonesia, that is subject to multiple stressors such as flow alteration, eutrophication and invasive species. In this study, the dynamics of the zooplankton community size structure was investigated in Lake Tempe. Five size-based metrics, including zooplankton mean body size, total abundance, total, biomass, and normalised biomass size spectra (NBSS) slope and intercept were assessed from net-sampled zooplankton collected monthly from March to December 2016, and the role of environmental variables in shaping these size-based metrics were also examined. Zooplankton community size structure is a useful metric as it is less labour intensive than traditional approaches, provides more data accuracy and does not require highly specialised taxonomic expertise. The zooplankton community in Lake Tempe was characterised by high density of small-sized zooplankton with an average mean body size < 500 µm equivalent spherical diameter. While the zooplankton density was characterised by the dominance of the size class 300–700 µm, there was evidence of a significant contribution of the size > 700 µm towards total biomass. Seasonal hydrological regimes, water temperature and eutrophication parameters, as indicated by total phosphorus and chlorophyll-a concentration, had a significant role in driving the variability of zooplankton community size structure in this system. The results of this study are not only a significant step in providing critical baseline information on the zooplankton assemblage of Lake Tempe, but is also a significant contribution to the overall understanding of zooplankton community structure in tropical lakes, and will aid in improving lake management plans in these regions.

Top-down and bottom-up control of plankton structure and dynamics in hypertrophic fishponds

We investigated the effects of strong top-down control by high fish stock on structure and seasonal dynamics of plankton in nine fishponds under conventional fishery management based on auxiliary feeding during two vegetation seasons. Mean concentrations of total nitrogen, phosphorus, and high densities of phytoplankton, bacteria, heterotrophic nanoflagellates, and ciliates indicated hypertrophic state of the fishponds, as well as a markedly reduced control of these microbial food web components by crustacean zooplankton. Mean seasonal densities of zooplankton varied within one order of magnitude for cladocerans, copepods, nauplii, and rotifers. Daphnia were found in most fishponds in densities up to 630 ind. l−1 (median: 53 ind. l−1). While TN and TP concentrations were high, dissolved inorganic N (median: 29 µg l−1) and reactive P (median: 11 µg l−1) indicated possible nutrient deficiency. The fish stock index (defined as the product of biomass and square root of densities) was used as a proxy for fish predation pressure. Multivariate analysis revealed that nutrients and high fish stocks (market carp, carp fry, and/or undesirable small planktivorous fishes) were the main driving forces shaping the fishpond plankton. The resulting trophic structure thus severely reduced the herbivorous zooplankton–fish link during a vegetation season.

Long-term studies of water chemistry and zooplankton interactions in a submontane dam reservoir in variable hydrological years (dry, wet, average)

The differences in environmental parameters and zooplankton community were studied in the epilimnion of the Carpathian Dobczyce Dam Reservoir on the Raba River (southern Poland) between hydrologically dry (HD), average (HA) and wet (HW) years distinguished on the basis of mean annual flow for 2000-2017. We found significant differences in water chemistry (conductivity, nutrients: P-tot, PO43−, NH4+) in the epilimnion between the studied hydrological years. The total density and dry weight of zooplankton and the density of Rotifera: Keratella quadrata (Müller, 1786), Copepoda: Copepoda n. det. (immature stages), Cyclops strenuus Fischer, 1851, Eudiaptomus gracilis (Sars G.O., 1863) and Cladocera: Bosmina longirostris (O.F.Müller, 1776), Daphnia cucullata G.O. Sars, 1862, and D. longispina (O.F.Müller, 1776) were significantly higher in HA and HW years than in HD years. The highest densities of many Rotifera, Cladocera and Copepoda species were found in HA and HW years with high flows or floods in the river in spring or early summer. At these times, the epilimnion was rich in P-tot (diffuse pollution), considered as a limiting factor for algal growth in Carpathian reservoirs. The best Generalized Linear Models (GLM) for zooplankton density included 4-6 factors, among which P-tot, NO3−, and pH were always present. We found that river flows prevailing in a given year determine water chemistry and eutrophication processes, which has a significant impact on densities and dry weight of zooplankton communities in HD, HA and HW years. The results obtained have important implications for proper management in mountain catchments.

Flow Augmentations Modify an Estuarine Prey Field

Zooplankton density and community composition in estuaries can be affected by variation in freshwater inputs, with important implications for higher trophic levels. In the San Francisco Estuary, management agencies have initiated autumn flow augmentations in the form of changes to reservoir releases or to exported water from the South Delta to increase and improve available habitat for endangered Delta Smelt, Hypomesus transpacificus, during the season when their body condition most influences fecundity. Autumn flow augmentation only occurs in years with higher precipitation, effectively moving the Low-Salinity Zone (LSZ) downstream to key foraging habitats for Delta Smelt in Suisun Bay and Suisun Marsh. To assess whether augmented flow enhanced prey resources for Delta Smelt, we compared autumn zooplankton abundance, biomass, spatial distribution, and community composition in years when flow was augmented (2017, 2019) with reference years when flow was not augmented (2018, 2020). In augmented years, we detected higher total zooplankton abundance and altered community composition in Suisun Bay and Suisun Marsh. Increased freshwater in these regions was associated with higher abundance of Pseudodiaptomus forbesi, a preferred prey of Delta Smelt, while species associated with higher salinities—Acartiella sinensis and Tortanus dextrilobatus—were less abundant. Thus, autumn flow augmentations can influence foraging habitat and prey availability for Delta Smelt, underscoring the complex responses of estuarine zooplankton communities to changes in response to flow and salinity regimes. This study is management- relevant because it shows that important Delta Smelt prey items increase in downstream regions when X2 is lower. Whether that results in a response in Delta Smelt abundance remains to be seen.

Lagoon morphology as an overarching driver for perch breeding success

Fish spawning and nursery habitats are critically important for the maintenance and conservation of viable fish stocks. Understanding habitat use of breeding fish is therefore important. This study examines the spatial distribution of Eurasian perch (Perca fluviatilis) egg strand occurrence and larval density in 18 brackish water post-glacial land-uplift lagoons in the northern Baltic Sea. The aim of the study was to quantify spawning habitat characteristics and evaluate how geomorphological, hydrological, and biological parameters affect perch breeding. Egg strand occurrence was assessed by snorkeling whereas fish larvae and zooplankton were sampled using horizontal surface hauls. Egg strand and larval density increased with higher habitat isolation, i.e., bay morphology had a decisive role in determining early recruitment success. Moreover, egg strand occurrence and larval density correlated positively with water temperature, charophyte cover and negatively with salinity. The zooplankton community structure differed among lagoon types but neither zooplankton density nor diversity showed a clear association with egg strand or fish larvae abundance. However, cladocerans and copepods were abundant in the most enclosed bays, and their density correlated positively with perch larval density. Our findings comply with earlier studies highlighting the importance of bay isolation for fish recruitment strength. We call for a foreseeing coastal management planning, that apart from considering current status and trends, also integrates decadal long projections of isostatic land-uplift processes in conservation decisions to secure the long-term persistence of the best spawning and nursery areas.

Abundance trade-offs and dominant taxa maintain the stability of the bacterioplankton community underlying Microcystis blooms.

Microcystis blooms are an intractable global environmental problem that pollute water and compromise ecosystem functioning. Closed-lake management practices keep lakes free of sewage and harmful algae invasions and have succeeded in controlling local Microcystis blooms; however, there is little understanding of how the bacterioplankton communities associated with Microcystis have changed. Here, based on metagenomic sequencing, the phyla, genera, functional genes and metabolic functions of the bacterioplankton communities were compared between open lakes (underlying Microcystis blooms) and closed lakes (no Microcystis blooms). Water properties and zooplankton density were investigated and measured as factors influencing blooms. The results showed that (1) the water quality of closed lakes was improved, and the nitrogen and phosphorus concentrations were significantly reduced. (2) The stability of open vs. closed-managed lakes differed notably at the species and genus levels (p < 0.01), but no significant variations were identified at the phylum and functional genes levels (p > 0.05). (3) The relative abundance of Microcystis (Cyanobacteria) increased dramatically in the open lakes (proportions from 1.44 to 41.76%), whereas the relative abundance of several other dominant genera of Cyanobacteria experienced a trade-off and decreased with increasing Microcystis relative abundance. (4) The main functions of the bacterioplankton communities were primarily related to dominant genera of Proteobacteria and had no significant relationship with Microcystis. Overall, the closed-lake management practices significantly reduced nutrients and prevented Microcystis blooms, but the taxonomic and functional structures of bacterioplankton communities remained stable overall.

The Resource Status of Plankton after Stocked Protosalanx chinensis Population Collapse in a Lake of Northeastern China

In order to understand the relative strength of top-down and bottom-up control in lakes of grazing alien fish, Protosalanx chinensis, investigations were designed in Lake Longhu (Lake L, P. chinensis introduced in 2013) and Lake Qijia (Lake Q, P. chinensis free). Plankton samples were collected bimonthly through the whole life cycle of P. chinensis (from February to December in 2018). A total of 133 phytoplankton and 68 zooplankton species were recorded in the two lakes. The total density and biomass of phytoplankton and zooplankton were 991.89 × 104 ind/L and 9.2418 mg/L as well as 5212 ind/L and 20.2646 mg/L, respectively. This study revealed that P. chinensis grazing did not deplete the zooplankton resources in the lake where it was stocked. Biodiversity in Lake L was not significantly different from that in Lake Q based on both phytoplankton and zooplankton. Overall, the over grazing of P. chinensis was not found in Lake L. Nevertheless, compared to Lake Q, the correlation between phytoplankton and zooplankton was weakened in Lake L, which meant there were still some effects of stocking P. chinensis on the ecological equilibrium of the plankton community, although no dramatic influences were found in Lake L yet. We also found that P. chinensis and Cladocera were significantly correlated, which should account for the top-down influences. Long-term successive investigations are suggested for sustainable resource utilization and maintaining biological balance.

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.

Flow and plankton availability control young‐of‐the‐year fish diet in two floodplain nurseries

AbstractIn large river floodplains, the availability of trophic resources to the fish fauna is highly variable as a consequence of seasonal environmental change and habitat diversity. Young‐of‐the‐year fishes (YOY) must find suitable habitats to settle, feed and survive. However, very few in‐depth studies are available about the food preferences of the young fishes during their first growing season. Here, we investigated the composition of planktonic assemblages and the YOY diet of three generalist fish species Alburnus alburnus (Linnaeus, 1758), Squalius cephalus (Linnaeus, 1758) and Pseudorasbora parva (Temminck &amp; Schlegel, 1846) from four floodplain sites of the French Upper Rhône River. More specifically, we studied their temporal and spatial variations in relation to five environmental variables: hydrology, dissolved oxygen, primary production, water temperature and conductivity. Stable flow conditions and the associated temperature and conductivity strongly structured the phytoplankton community in the floodplain channels, whereas water movements within channels and dissolved oxygen concentrations were significantly correlated to the zooplankton composition. A zooplankton density above ≈100 ind L−1 allowed the initiation of a YOY diet mainly based upon zooplankton for the three fish species. When zooplankton densities were insufficient, all three species used phytoplankton as their main food resource. Finally, the diet overlaps between species, differed significantly between sites. The study highlights the need to examine the diet of juvenile fishes and environmental variables in the floodplains.

Evaluating Surface Water Quality Using Indexes of Water Quality and Plankton Diversity

The study aimed to assess the relationship between surface water quality and the diversity of planktonic communities in An Giang province, Vietnam. The national technical regulations on surface water quality, the water quality index (WQI), and the Shannon-Wiener diversity index (H') were applied to evaluate water quality. The considerable influence of water quality parameters on the dominant plankton was determined by canonical correspondence analysis (CCA) and similarity percentage analysis (SIMPER). The results showed that water quality was contaminated by organic matter, total suspended solids (TSS), and microorganisms. WQI values classified water quality as ranging from bad to good. The species composition of phytoplankton was dominated by two phyla, Chlorophyta and Bacillariophyta, and that of zooplankton was the Rotifera group. SIMPER analysis identified phytoplankton species with dominant density, including Melosira granulata, Pediastrum duplex, Anabaena sp., and Lyngbya circumcreta. Microcyclops varicans, Filinia longiseta, Trichocerca pusilla, Copepoda nauplius, Brachionus caudatus, and Polyarthra vulgarisdominated the density of zooplankton. Temperature, pH, TSS, ammonium, orthophosphate, and coliform considerably influence the dominant species composition of plankton. However, the indicators of diversity and composition of plankton were unable to completely reflect water quality. These findings could contribute to the indicator selection in developing the monitoring water quality programs. Doi: 10.28991/CEJ-2023-09-05-011 Full Text: PDF

Epibenthic faunal community dynamics and seasonal species turnover in a deep-sea coral ecosystem

Deep-sea coral ecosystems represent oases of life in the deep ocean, often hosting abundant and diverse faunal communities. Although mounting evidence indicates that deep-sea benthic communities are highly dynamic and can change over scales of a few hours to seasons or years, such dynamics have never been characterized in deep-sea coral ecosystems. We used a time-lapse camera deployed for a year at a depth of 1230 m on Sur Ridge (Monterey Bay National Marine Sanctuary) to characterize hourly changes in megafaunal abundance and diversity in a deep-sea coral assemblage. The response of community dynamics to variation in environmental factors, including surface net primary production as well as current speed/direction, temperature and acoustic backscatter (a proxy for particle and zooplankton density) at depth, was also evaluated. Overall, 33 taxa from 6 phyla, including multiple commercially valuable species, were observed throughout the study period. The strong seasonal pattern and periodicities in the occurrence of the most abundant taxa likely drove the observed temporal trends in overall abundance and diversity. Fluctuations in food availability may have, at least partially, driven these trends, as indicated by the significant relationship between community dynamics, surface net primary production and acoustic backscatter at depth. However, the low explanatory power of environmental parameters tested here suggest that biotic factors such as individual behaviors and species interactions had a strong influence on community dynamics. This study emphasizes the role of deep-sea coral as habitat and the need for monitoring to better understand how environmental and biological processes interact to shape associated faunal communities.