ForCenS-LGM: a dataset of planktonic foraminifera species assemblage composition for the Last Glacial Maximum.

Species assemblage composition of marine microfossils offers the possibility to investigate ecological and climatological change on time scales inaccessible using conventional observations. Planktonic foraminifera - calcareous zooplankton - have an excellent fossil record and are used extensively in palaeoecology and palaeoceanography. During the Last Glacial Maximum (LGM; 19,000 - 23,000 years ago), the climate was in a radically different state. This period is therefore a key target to investigate climate and biodiversity under different conditions than today. Studying LGM climate and ecosystems indeed has a long history, yet the most recent global synthesis of planktonic foraminifera assemblage composition is now nearly two decades old. Here we present the ForCenS-LGM dataset with 2,365 species assemblage samples collected using standardised methods and with harmonised taxonomy. The data originate from marine sediments from 664 sites and present a more than 50% increase in coverage compared to previous work. The taxonomy is compatible with the most recent global core top dataset, enabling direct investigation of temporal changes in foraminifera biogeography and facilitating seawater temperature reconstructions.

Influence of the community assemblage on sulfur distributions in the South China sea.

Marine distribution of dimethylsulfoniopropionate (DMSP) and its cleavage product dimethyl sulfide (DMS) is greatly affected by the community structures of bacteria, phytoplankton, and zooplankton. Spatial distributions of dissolved and particulate DMSP (DMSPd,p), and DMS were measured and their relationships with DMSP lyase activity (DLA), abundance of DMSP-consuming bacteria (DCB), and the community structures of phytoplankton, zooplankton, and bacteria were determined during summer in the South China Sea (SCS). The depth distributions of DMSPd,p exhibited a similar trend with Chl a, reaching their maxima in the mixing layer. The DMS concentration was positively correlated with DCB abundance and DLA, indicating that DCB and DMSP lyase had a significant effect on DMS production. High DMS concentrations in the horizontal distribution coincided with high DCB abundance and DLA and may be due to the rapid growth of phytoplankton resulting from the high dissolved inorganic nitrogen concentration brought by the cold vortices. Moreover, the highest copepod abundance at station G3 coincided with the highest DMS concentrations there among stations B4, F2, and G3. These results suggest that copepod may play an important role in DMS production. The bacterial SAR11 clade was positively correlated with DLA, indicating its significant contribution to DMSP degradation in the SCS. These findings contribute to the understanding of the effect of the community assemblage on DMSP/DMS distributions in the SCS dominated by mesoscale vortices.

Assessment of toxic effects of imidacloprid on freshwater zooplankton: An experimental test for 27 species.

The neonicotinoid pesticide imidacloprid has been used worldwide since 1992. As one of the most important chemicals used in pest control, there have been concerns that its run-off into rivers and lakes could adversely affect aquatic ecosystems, where zooplankton play a central role in the energy flow from primary to higher trophic levels. However, studies assessing the effects of pesticides at the species level have relied on a Daphnia-centric approach, and no studies have been conducted using species-level assessments on a broad range of zooplankton taxa. In the present study, we therefore investigated the acute toxicity of imidacloprid on 27 freshwater crustacean zooplankton (18 cladocerans, 3 calanoid copepods and 6 cyclopoid copepods). The experiment showed that a majority of calanoid copepods and cladocerans were not affected at all by imidacloprid, with the exception of one species each of Ceriodaphnia and Diaphasoma, while all six cyclopoid copepods showed high mortality rates, even at concentrations of imidacloprid typically found in nature. In addition, we found a remarkable intra-taxonomic variation in susceptibility to this chemical. As many cyclopoid copepods are omnivorous, they act as predators as well as competitors with other zooplankton. Accordingly, their susceptibility to imidacloprid is likely to cause different responses at the community level through changes in predation pressure as well as changes in competitive interactions. The present results demonstrate the need for species-level assessments of various zooplankton taxa to understand the complex responses of aquatic communities to pesticide disturbance.

Influence of microplastics and biogenic particles on the size spectra of tropical estuarine and marine pelagic ecosystems.

Size spectra analysis has been widely used to study pelagic ecosystems worldwide. It has a solid theoretical and empirical basis and can be used to provide useful information on ecosystem structure and trophic efficiency. The objective of this study was to obtain complete Normalized Biovolume Size Spectra (NBSS), including zooplankton, microplastics, and other suspended particles, along an estuary-shelf gradient. Plankton net samples (300 µm mesh) were obtained in the Rio Formoso Estuary, in Tamandaré Bay and on the continental shelf off Tamandaré, Brazil, during two years (from April/2013 to May/2015). Particles were identified by image analysis (ZooScan) and infrared spectroscopy (FTIR). Generally, NBSS slopes were close to -1 (i.e., between -1.09 and -0.85), except for NBSSz (zooplankton only) in the Estuary (-1.59) and in the Bay (-1.44), where the steepest slopes were observed, due to the importance of small-sized zooplankton in these areas. The NBSSz slope was significantly steeper in the Estuary and in the Bay than on the Shelf. The inclusion of particles into the NBSS (NBSSp) turned the slope significantly less steep in the Estuary and in the Bay. Intercepts were significantly higher in the Estuary than in the other areas, after including particles in the analysis (NBSSp), due to the extremely high total volume of biogenic particles in the estuary. The most relevant impacts of microplastics were detected within the larger size classes (> 2.60 mm Feret length, > 0.58 log10 mm3). In the Estuary, large-sized microplastics were similarly important (in terms of volume) as zooplankton. Large-sized polyethylene and polypropylene were more relevant in the Bay, large-sized nylon fibers on the Shelf (in the rainy season). The present study, a pioneering effort towards a synthetic analysis of zooplankton, microplastics, and other particles, highlights the importance of including non-living particles in size-based studies and ecosystem models.

Impact of climate change and oligotrophication on quality and quantity of lake primary production: A case study in Lake Biwa.

Global climate change and anthropogenic oligotrophication are expected to reshape the dynamics of primary production (PP) in aquatic ecosystems; however, few studies have explored their long-term effects. In theory, the PP of phytoplankton in Lake Biwa may decline over decades due to warming, heightened stratification, and anthropogenic oligotrophication. Furthermore, the PP of large phytoplankton, which are inedible to zooplankton, along with biomass-specific productivity (PBc), could decrease. In this study, data from 1976 to 2021 and active fluorometry measurements taken in 2020 and 2021 were evaluated. Quantitatively, the temporal dynamics of mean seasonal PP during 1971-2021 were assessed according to the carbon fixation rate to investigate relationships among environmental factors. Qualitatively, phytoplankton biomass, PP, and PBc were measured in two size fractions [edible (S) or inedible (L) for zooplankton] in 2020 and 2021, and the L:S balance for these three measures was compared between 1992 (low-temperature/high-nutrient conditions) and 2020-2021 (high-temperature/low-nutrient conditions) to assess seasonal dynamics. The results indicated that climate change and anthropogenic oligotrophication over the past 30 years have diminished Lake Biwa's PP since the 1990s, impacting the phenology of PP dynamics. However, the L:S balance in PP and PBc has exhibited minimal change between the data from 1992 and the 2020-2021 period. These findings suggest that, although climate change and oligotrophication may reduce overall PP, they may not markedly alter the inedible/edible phytoplankton balance in terms of PP and PBc. Instead, as total PP declines, the production of small edible phytoplankton may decrease proportionally, potentially affecting trophic transfer efficiency and material cycling in Lake Biwa.

Temporal and Spatial Comparison of Mercury Bioaccumulation in the Lower Trophic Levels of a Post-glacial Lake Food Web.

Total mercury (Hg) concentrations and carbon (δ13C) and nitrogen (δ15N) stable isotopes were quantified among aquatic invertebrate and sediment samples collected from Keuka Lake in New York's Finger Lakes region to evaluate temporal and spatial variability in Hg bioaccumulation and trophic ecology among these lower trophic levels. Hg concentrations ranged from 6.3 to 158.8 ng/g (dry wt) across dreissenid mussel, zooplankton, and juvenile (< 10 mm) and adult (≥ 10 mm) mysid shrimp (Mysis diluviana) samples. Hg concentrations were higher in samples collected from the western basin in 2015 relative to those for samples collected from this basin in 2022 (p < 0.001). While no specific mechanisms could be identified to explain this difference, higher δ15N values for zooplankton collected in 2015 support conclusions regarding the role of zooplankton trophic status on Hg concentrations in these populations. Spatial patterns in Hg concentrations were of generally low variability among samples collected from the lake's east, west and south basins in 2022. Trophic positions as inferred by δ15N were represented by adult mysids > juvenile mysids > large zooplankton (≥ 500 µm) > dreissenid mussels ≥ small zooplankton (64-500 µm). Differences were evident among the regression slopes describing the relationships between sample Hg concentrations and δ15N values across the lake's three basins (p = 0.028). However, this was primarily attributed to high δ15N values measured in dreissenid mussels collected from the south basin in 2022. Biota sediment accumulation factors ranged from 0.2 to 2.3 and were highest for adult M. diluviana but mysid δ13C values generally supported a pelagic pathway of Hg exposure relative to benthic sediments. Overall, these results provide additional support regarding the contributions of lower trophic levels to Hg biomagnification in aquatic food-webs.

Unprecedented insights into extents of biological responses to physical forcing in an Arctic sub-mesoscale filament by combining high-resolution measurement approaches.

In Fram Strait, we combined underway-sampling using the remote-controlled Automated Filtration System for Marine Microbes (AUTOFIM) with CTD-sampling for eDNA analyses, and with high-resolution optical measurements in an unprecedented approach to determine variability in plankton composition in response to physical forcing in a sub-mesoscale filament. We determined plankton composition and biomass near the surface with a horizontal resolution of ~ 2 km, and addressed vertical variability at five selected sites. Inside and near the filament, plankton composition was tightly linked to the hydrological dynamics related to the presence of sea ice. The comprehensive data set indicates that sea-ice melt related stratification near the surface inside the sub-mesoscale filament resulted in increased sequence abundances of sea ice-associated diatoms and zooplankton near the surface. In analogy to the physical data set, the underway eDNA data, complemented with highly sampled phytoplankton pigment data suggest a corridor of 7 km along the filament with enhanced photosynthetic biomass and sequence abundances of sea-ice associated plankton. Thus, based on our data we extrapolated an area of 350 km2 in Fram Strait with enhanced plankton abundances, possibly leading to enhanced POC export in an area that is around a magnitude larger than the visible streak of sea-ice.

Declining calcium concentration drives shifts toward smaller and less nutritious zooplankton in northern lakes.

Zooplankton community composition of northern lakes is changing due to the interactive effects of climate change and recovery from acidification, yet limited data are available to assess these changes combined. Here, we built a database using archives of temperature, water chemistry and zooplankton data from 60 Scandinavian lakes that represent broad spatial and temporal gradients in key parameters: temperature, calcium (Ca), total phosphorus (TP), total organic carbon (TOC), and pH. Using machine learning techniques, we found that Ca was the most important determinant of the relative abundance of all zooplankton groups studied, while pH was second, and TOC third in importance. Further, we found that Ca is declining in almost all lakes, and we detected a critical Ca threshold in lake water of 1.3 mg L-1 , below which the relative abundance of zooplankton shifts toward dominance of Holopedium gibberum and small cladocerans at the expense of Daphnia and copepods. Our findings suggest that low Ca concentrations may shape zooplankton communities, and that current trajectories of Ca decline could promote widespread changes in pelagic food webs as zooplankton are important trophic links from phytoplankton to fish and different zooplankton species play different roles in this context.

Toxicity assays and in silico approach to assess the impacts of chlorine dioxide on survival, respiration and some biochemical markers of marine zooplankton.

Chlorination is the common antifouling method in desalination and power plant water intake structures to control microbial and macrofouling growth. In this study, the impacts of chlorine dioxide on toxicity, metabolic activity and biochemical markers like glutathione S-transferase and catalase enzyme activity were tested using four zooplankton species (Centropages sp., Acartia sp., Oncaea sp., and Calanus sp.) collected from the Red Sea. The zooplankton species were treated with different concentrations (0.02, 0.05, 0.1, 0.2, and 0.5 mg L-1) of chlorine dioxide. Further, chlorite, the main decomposition product of chlorine dioxide, was used for molecular docking studies against glutathione S-transferase and catalase enzymes. The results indicated the LC50 range of 0.552-1.643 mg L-1 for the studied zooplankton species. The respiration rate of the zooplankton increased due to the chlorine dioxide treatment with a maximum of 0.562 µg O2 copepod h-1 in Acartia. The glutathione S-transferase and catalase enzyme activities showed elevated values in zooplankton treated with chlorine dioxide. Molecular docking of chlorite with enzymes involved in antioxidant defense activity, such as glutathione S-transferase and catalase enzyme showed weak interactions. Overall, this study yielded significant insights for understanding the effects of chlorine dioxide on the survival, metabolism, and biochemical composition of marine zooplankton.

Incorporating recirculation effects into metrics of feeding performance for current-feeding zooplankton.

The feeding performance of zooplankton influences their evolution and can explain their behaviour. A commonly used metric for feeding performance is the volume of fluid that flows through a filtering surface and is scanned for food. Here, we show that such a metric may give incorrect results for organisms that produce recirculatory flows, so that fluid flowing through the filter may have been already filtered of food. In a numerical model, we construct a feeding metric that correctly accounts for recirculation in a sessile model organism inspired by our experimental observations of Vorticella and its flow field. Our metric tracks the history of current-borne particles to determine if they have already been filtered by the filtering surface. Examining the pathlines of food particles reveals that the capture of fresh particles preferentially involves the tips of cilia, which we corroborate in observations of feeding Vorticella. We compare the amount of fresh nutrient particles carried to the organism with other metrics of feeding, and show that metrics that do not take into account the history of particles cannot correctly compute the volume of freshly scanned fluid.

Marine Bioluminescence: Simulation of Dynamics within a Pump-Through Bathyphotometer.

Bioluminescence is light produced by organisms through chemical reactions. In most cases, bioluminescent organisms produce light in response to mechanical stimulation, including from shear around objects moving in the water. Many phytoplankton and zooplankton are capable of producing bioluminescence, which is commonly measured as bioluminescence potential, defined as mechanically stimulated light measured inside of a chambered pump-through bathyphotometer. We have developed a numerical model of a pump-through bathyphotometer and simulated flow using Lagrangian particles as an approximation for bioluminescent marine plankton taxa. The results indicate that all particles remain in the detection chamber for a residence time of at least 0.25 s. This suggests that the total first flash of bioluminescent autotrophic and heterotrophic dinoflagellates will be measured based on the existing literature regarding their flash duration. We have found low sensitivity of particle residence time to variations in particle size, density, or measurement depth. In addition, the results show that a high percentage of organisms may experience stimulation well before the detection chamber, or even multiple stimulations within the detection chamber. The results of this work serve to inform the processing of current bioluminescent potential data and assist in the development of future instruments.

Synergistic digestibility effect by planktonic natural food and habitat renders high digestion efficiency in agastric aquatic consumers.

A digestibility enhancing effect of natural food on stomachless fish model (Cyprinus carpio) was verified by fluorogenic substrate assays of enzymatic activities in experimental pond carp gut flush and planktonic food over a full vegetative season. Then compared with size-matched conspecific grown artificially (tank carp) and an advanced omnivore species possessing true stomach (tilapia, Oreochromis niloticus). Results suggested activities of digestive enzymes (except amylolytic) were significantly higher in pond carp (p ≤ 0.05) than in the size-matched tank carp. Even compared to tilapia, pond carp appeared superior (p < 0.05; proteolytic or chitinolytic activities) or comparable (p > 0.05; phosphatase or cellulolytic activities). Amylolytic, chitinolytic, and phosphatases activities in pond carp gut significantly increased (p ≤ 0.01) over season. Several orders-of-magnitude higher enzymatic activities were detected in planktonic natural food than expressed in carp gut. Amino acid markers in planktonic food revealed a higher share of zooplankton (microcrustaceans), but not phytoplankton, synchronized with higher activities of complex polysaccharide-splitting enzymes (cellulolytic and chitinolytic) in fish gut. Periods of clear water phase low in chlorophyll-a and nutrients, but high in certain zooplankton (preferably cladocerans), may create a synergistic digestibility effect in pond carp. We conclude aquatic ecosystem components (natural food, water, microbiota) enhance fishes' hydrolyzing capabilities of C/N/P macromolecules and even their complex polymers such as cellulose, chitin, and maybe phytate (to be validated), to the extent that being stomachless is not an issue. Aquatic nutritional ecologists may consider that laboratory-based understandings of digestibility may underestimate digestion efficiency of free-ranging fish in ponds or lakes.

Interference of two typical polycyclic aromatic hydrocarbons on the induced anti-grazing defense of Tetradesmus obliquus.

Anthropogenic emissions of polycyclic aromatic hydrocarbons (PAHs) cause severe ecological impacts by contaminating natural water bodies, affecting various biological groups, and altering interspecies relationships and ecological functions. This study examined the effects of two typical PAHs, phenanthrene (Phe) and naphthalene (Nap), on the anti-grazing defense mechanisms of Tetradesmus obliquus, a primary producer in freshwater food chains. Four non-lethal concentrations (0.01, 0.1, 1, and 10 mg L-1) of Phe and Nap were tested and the population growth, photosynthetic capacity, pigment content, and morphological defense of T. obliquus were analyzed. The results indicated that Phe and Nap inhibited both the growth rate and formation of defensive colonies of T. obliquus induced by Daphnia grazing cues, and the inhibition ratio increased with concentration. Phe and Nap significantly shortened the defense colony formation time of T. obliquus. Phe and Nap significantly suppressed photosynthesis in the early stages; however, the photosynthetic efficiency recovered over time. These findings highlight the high sensitivity of grazing-induced colony formation in T. obliquus to Phe and Nap at non-lethal concentrations, which could affect the interactions between phytoplankton and zooplankton in aquatic ecosystems. Our study underscores the influence of Phe and Nap on the defense mechanisms of phytoplankton and the consequential effects on ecological interactions within freshwater ecosystems, providing insight into the complex impacts of pollutants on phytoplankton-zooplankton relationships. Therefore, it is necessary to consider interspecific interactions when assessing the potential negative effects of environmental pollutants on aquatic ecosystems.

Shifts in phytoplankton and zooplankton communities in three cyanobacteria-dominated lakes after treatment with hydrogen peroxide.

Cyanobacteria can reach high densities in eutrophic lakes, which may cause problems due to their potential toxin production. Several methods are in use to prevent, control or mitigate harmful cyanobacterial blooms. Treatment of blooms with low concentrations of hydrogen peroxide (H2O2) is a promising emergency method. However, effects of H2O2 on cyanobacteria, eukaryotic phytoplankton and zooplankton have mainly been studied in controlled cultures and mesocosm experiments, while much less is known about the effectiveness and potential side effects of H2O2 treatments on entire lake ecosystems. In this study, we report on three different lakes in the Netherlands that were treated with average H2O2 concentrations ranging from 2 to 5 mg L-1 to suppress cyanobacterial blooms. Effects on phytoplankton and zooplankton communities, on cyanotoxin concentrations, and on nutrient availability in the lakes were assessed. After every H2O2 treatment, cyanobacteria drastically declined, sometimes by more than 99%, although blooms of Dolichospermum sp., Aphanizomenon sp., and Planktothrix rubescens were more strongly suppressed than a Planktothrix agardhii bloom. Eukaryotic phytoplankton were not significantly affected by the H2O2 additions and had an initial advantage over cyanobacteria after the treatment, when ample nutrients and light were available. In all three lakes, a new cyanobacterial bloom developed within several weeks after the first H2O2 treatment, and in two lakes a second H2O2 treatment was therefore applied to again suppress the cyanobacterial population. Rotifers strongly declined after most H2O2 treatments except when the H2O2 concentration was ≤ 2 mg L-1, whereas cladocerans were only mildly affected and copepods were least impacted by the added H2O2. In response to the treatments, the cyanotoxins microcystins and anabaenopeptins were released from the cells into the water column, but disappeared after a few days. We conclude that lake treatments with low concentrations of H2O2 can be a successful tool to suppress harmful cyanobacterial blooms, but may negatively affect some of the zooplankton taxa in lakes. We advise pre-tests prior to the treatment of lakes to define optimal treatment concentrations that kill the majority of the cyanobacteria and to minimize potential side effects on non-target organisms. In some cases, the pre-tests may discourage treatment of the lake.

Ingestion and adherence of microplastics by estuarine mysid shrimp.

Microplastics have been reported to be present in zooplankton, yet questions persist regarding their fate and dynamics within biota. We selected the commercial mysid shrimp, Mesopodopsis orientalis, as the focal zooplankton for this study due to their crucial role in our study area, the Inner Gulf of Thailand in January 2022. We investigated the presence of microplastics in mysid bodies and fecal pellets, examining both attached microplastics on external body parts and those ingested. In addition, we conducted microplastic feeding experiments, exposing mysids to various treatments of microplastics. The results of the field investigation indicate that mysids exhibited an average of 0.12 ± 0.03 microplastic items/mysid from whole-body samples. The shape, type, and color of microplastics found in mysids were similar to those present in seawater, with blue PET microfibers being the most prevalent. Our observations on live mysids revealed that microplastics were acquired through ingestion and adherence to appendages and exoskeletons. Microplastics were observed in mysid's fecal pellets at 0.09 ± 0.03 items/mysid, while microplastics adhering to the mysid's body and appendages were observed at 0.10 ± 0.04 items/mysid. The sizes of microplastics extracted from preserved mysids ranged from 58 µm to 4669 µm, with median of 507 µm. The laboratory experiments revealed that the presence of microalgae enhanced microplastic ingestion in mysids; microplastics incubated with a cyanobacterium, Oscillatoria sp., and diatom Navicula sp. significantly increased the number of microplastic particles ingested by mysids. This study showed that microplastics can be more ingested in mysids, especially when food items are present. Microplastic fate in these animals may involve expulsion into the environment or adherence, potentially facilitating their transfer up the marine food web.

Environmental factors controlling seasonal and spatial variability of zooplankton in thermokarst lakes along a permafrost gradient of Western Siberia.

Humic thermokarst lakes of permafrost peatlands in Western Siberia Lowland (WSL) are major environmental controllers of carbon and nutrient storage in inland waters and greenhouse gases emissions to the atmosphere in the subarctic. In contrast to sizable former research devoted to hydrochemical and hydrobiological (phytoplankton) composition, zooplankton communities of these thermokarst lakes and thaw ponds remain poorly understood, especially along the latitudinal gradient, which is a perfect predictor of permafrost zones. To fill this gap, 69 thermokarst lakes of the WSL were sampled using unprecedented spatial coverage, from continuous to sporadic permafrost zone, in order to assess zooplankton (Cladocera, Copepoda, Rotifera) diversity and abundance across three main open water physiological seasons (spring, summer and autumn). We aimed at assessing the relationship of environmental factors (water column hydrochemistry, nutrients, and phytoplankton parameters) with the abundance and diversity of zooplankton. A total of 74 zooplankton species and taxa were detected, with an average eight taxa per lake/pond. Species richness increased towards the north and reached the maximum in the continuous permafrost zone with 13 species found in this zone only. In contrast, the number of species per waterbody decreased towards the north, which was mainly associated with a decrease in the number of cladocerans. Abundance and diversity of specific zooplankton groups strongly varied across the seasons and permafrost zones. Among the main environmental controllers, Redundancy Analysis revealed that water temperature, lake area, depth, pH, Dissolved Inorganic and Organic Carbon and CO2 concentrations were closely related to zooplankton abundance. Cladocerans were positively related to water temperature during all seasons. Copepods were positively related to depth and lake water pH in all seasons. Rotifers were related to different factors in each season, but were most strongly associated with DOC, depth, CH4, phytoplankton and cladoceran abundance. Under climate warming scenario, considering water temperature increase and permafrost boundary shift northward, one can expect an increase in the diversity and abundance of cladocerans towards the north which can lead to partial disappearance of copepods, especially rare calanoid species.

Resilience of rotifers and cladocerans communities in four reservoirs with eutrophication pollution and lead concentrations in Aguascalientes, Mexico.

Pollution in aquatic ecosystems has been increasing drastically worldwide changing their water quality. Therefore, species must be adapted to these new scenarios. In Aguascalientes City, four representative urban reservoirs contain lead in the water column and extremely high concentrations of sediments. Therefore, an analysis was conducted to evaluate the resilience of zooplankton species to lead exposure in each reservoir using dormant and organisms. Results demonstrated a decrease range from 57.5 to 22.5% in overall diapausing egg hatching rate, while survivorship rate also decreased from 98 to 54% when organisms were exposed to the water of the four reservoirs and increasing lead concentrations. When Pb exposure increased, results showed a global negative effect on both hatching rate (decreasing from 58 to 30% at 0.09 mg L-1) and survivorship levels (decreasing from 100% to 0.07% at 0.09 mg L-1). We provide Species Sensitivity Distribution for both water reservoir dilutions and lead concentration to analyze diapausing eggs hatching and survivorship of offspring in the presence of same polluted conditions or lead of the autochthonous species found in reservoirs. Furthermore, specific analysis with two populations of the cladoceran Moina macrocopa showed clear dissimilar hatching patterns that suggested a different adaptive mechanism. Niagara population shows a hatching rate of approximately 25% in the first two days of reservoir water exposure, while UAA population drastically increased hatching rate to 75% on exposure at day seven. We provide the first record of bioaccumulation in ephippia of M. macrocopa.

Enhancing water quality and ecosystems of reclaimed water-replenished river: A case study of Dongsha River, Beijing, China.

The use of reclaimed water for urban river replenishment has raised concerns regarding its impact on water quality and aquatic ecosystems. This study aims to reveal the improvements seen in an urban river undergoing a practical water eco-remediation after being replenished with reclaimed water. A one-year monitoring of water quality, phytoplankton, and zooplankton was carried out in Dongsha River undergoing eco-remediation in Beijing, China. The results showed that compared to the unrestored river, the concentrations of COD, NH4+-N, TP, and TN decreased by 28.22 ± 7.88 %, 40.24 ± 11.77 %, 44.17 ± 17.29 %, and 28.66 ± 10.39 % in the restoration project area, respectively. The concentration of Chlorophyll-a in the restoration area was maintained below 40 µg/L. During summer, when algal growth is vigorous, the density of Cyanophyta in the unrestored river decreased from 46.84 × 104cells/L to 16.32 × 104cells/L in the restored area, while that of Chlorophyta decreased from 41.61 × 104cells/L to 11.87 × 104cells/L, a reduction of 65.16 % and 71.47 %, respectively. The dominant phytoplankton species were replaced with Bacillariophyta, such as Synedra sp. and Nitzschia sp., indicating that the restoration of aquatic plants reduces the risk of Cyanophyta blooms. Zooplankton species also changed in the restoration area, especially during summer. The density of pollution-tolerant Rotifer and Protozoa decreased by 31.06 % and 27.22 %, while the density of clean water indicating Cladocera increased by 101.19 %. We further calculated the diversity and evenness index of phytoplankton and zooplankton within and outside the restoration area. The results showed that the Shannon-Weaver index for phytoplankton and zooplankton in the restoration area was 2.1 and 1.91, which was higher than those in the river (1.84 and 1.82). This further confirmed that aquatic plant restoration has positive effects. This study can provide a practical reference and theoretical basis for the implementation of water ecological restoration projects in other reclaimed water rivers in China.

Herbicide leakage into seawater impacts primary productivity and zooplankton globally.

Predicting the magnitude of herbicide impacts on marine primary productivity remains challenging because the extent of worldwide herbicide pollution in coastal waters and the concentration-response relationships of phytoplankton communities to multiple herbicides are unclear. By analyzing the spatiotemporal distribution of herbicides at 661 bay and gulf stations worldwide from 1990 to 2022, we determined median, third quartile and maximum concentrations of 12 triazine herbicides of 0.18 nmol L-1, 1.27 nmol L-1 and 29.50 nmol L-1 (95%Confidence Interval: CI 1.06, 1.47), respectively. Under current herbicide stress, phytoplankton primary productivity was inhibited by more than 5% at 25% of the sites and by more than 10% at 10% of the sites (95%CI 3.67, 4.34), due to the inhibition of highly abundant sensitive species, community structure/particle size succession (from Bacillariophyta to Dinophyceae and from nano-phytoplankton to micro-phytoplankton), and resulting growth rate reduction. Concurrently, due to food chain cascade effects, the dominant micro-zooplankton population shifted from larger copepod larvae to smaller unicellular ciliates, which might prolong the transmission process in marine food chain and reduce the primary productivity transmission efficiency. As herbicide application rates on farmlands worldwide are correlated with residues in their adjacent seas, a continued future increase in herbicide input may seriously affect the stability of coastal waters.