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The early–middle Frasnian boundary interval of the northern part of the East European Platform (northwest of Russia) corresponding to the transitans-punctata isotope event is revealed by biostratigraphically constrained conodont carbon stable isotope data (δ13Ccon). The dynamics of δ13Ccon demonstrate a three-fold pattern with positive peaks at the onset of the main phase of the transitans-punctata isotope event (upper part of Montagne Noire 4 conodont Zone, MN4; up to -22.5‰ VPDB), and during the late part of the event (lower and middle parts of MN6 Zone; up to -24.0‰ VPDB and -22.1‰ VPDB). The stratigraphic level near the MN5 and MN6 boundary is marked by a prominent negative excursion in δ13Ccon (down to -31.8‰ VPDB) that resembles the negative excursion in the terminal phase of the transitans-punctata isotope event worldwide. The δ13Ccon variations in different taxa are generally consistent but demonstrate some differences in values and amplitudes. It is assumed that variations in the carbon isotopic compositions of conodonts were mainly controlled by changes in the isotope composition of the planktons as the main food source for conodonts.

It is generally assumed that viruses outnumber cells on Earth by at least tenfold. Virus-to-microbe ratios (VMR) are largely based on counts of fluorescently labelled virus-like particles. However, these exclude intracellular viruses and potentially include false positives (DNA-containing vesicles, gene-transfer agents, unspecifically stained inert particles). Here, we develop a metagenome-based VMR estimate (mVRM) that accounts for DNA viruses across all stages of their replication cycles (virion, intracellular lytic and lysogenic) by using normalised RPKM (reads per kilobase of gene sequence per million of mapped metagenome reads) counts of the major capsid protein (MCP) genes and cellular universal single-copy genes (USCGs) as proxies for virus and cell counts, respectively. After benchmarking this strategy using mock metagenomes with increasing VMR, we inferred mVMR across different biomes. To properly estimate mVMR in aquatic ecosystems, we generated metagenomes from co-occurring cellular and viral fractions (>50 kDa-200 µm size-range) in freshwater, seawater and solar saltern ponds (10 metagenomes, 2 control metaviromes). Viruses outnumbered cells in freshwater by ∼13 fold and in plankton from marine and saline waters by ∼2-4 fold. However, across an additional set of 121 diverse non-aquatic metagenomes including microbial mats, microbialites, soils, freshwater and marine sediments and metazoan-associated microbiomes, viruses, on average, outnumbered cells by barely two-fold. Although viruses likely are the most diverse biological entities on Earth, their global numbers might be closer to those of cells than previously estimated.

Litopenaeus vannamei is one of the largest commodities having a major impact on the global economy. Shrimp larvae have drastic changes in morphology and physiology which require extra maintenance. Feed management in early rearing using a blind feeding system which plankton as the main food. The relation between plankton and C/N needs to be investigated to optimize the growth of natural feed. The aims of the study were to analyze plankton community structure; the relationship between plankton to C/N and the environmental parameters; and determine the shrimp preferences of plankton. Data were collected at 3 points in 3 different ponds (PA, PB, PC) on day 8 and day 15 using a stratified sampling method with criteria (intensive system and blind feeding phase). Plankton density and C/N relationship were analyzed using Linear Regression, plankton and environmental parameters using Canonical Correspondence Analysis (CCA). Shrimp food preferences were analyzed descriptively in percentage. The results showed that diatoms and dinoflagellates dominated phytoplankton, and rotifers dominate zooplankton. C/N showed a positive correlation to protozoa, but a negative correlation to pennate diatoms and copepods. The most influential environmental factors for both phytoplankton and zooplankton density were temperature, C-organic, salinity, pH, alkalinity, and dissolved oxygen.

As the biggest inter-basin water transfer scheme in the world, the South-to-North Water Diversion Project (SNWD) was designed to alleviate the water crisis in North China. The main channel of the middle route of the SNWD is of great concern in terms of the drinking water quality. In this study, we tested the hypothesis that the dissolved organic matter (DOM) derived from the planktonic algae causes the rising levels of CODMn along the middle route by monitoring data on water quality (2015-2019, monthly resolution). The results showed that algal density in the main channel increased along the channel and was significantly correlated with CODMn (p

Highlight Research Indicated that white feces at Vanammei appeared along with the appearance of the disease besides its main trigger that is Vibrio sp. Increase the availability of carbon for photosynthesis process of phytoplankton. Clinical symptom of shrimp attacked by white feces disease is indicated by a change in intestine. Abstract Shrimp disease that currently causes economic loss to shrimp farmers is White Feces Disease (WFD). This disease appeared due to several factors, such as poor pond management, unhealthy shrimp seed, and poor water quality which resulted in the appearance of Vibrio sp. bacteria and Dinoflagellate. This study aimed to analyze the cause of WFD outbreak in vannamei shrimp pond. The study method through direct experiment was applied in shrimp pond. Sampling was performed three times in each feeding tray to collect ten shrimps. Overall, sampling was performed twice a week. The Sample Survey Method was used to collect sample in this study. Result of study showed that clinical symptom was observed through changes in pattern and behavior of vannamei shrimp during culture. However, this observation resulted in insignificant data. Vannamei shrimp infected WFD tended to swim slower and often rose to the surface with body color turned red. Moreover, total organic matter (TOM) increased on week-7 along with the increasing growth of plankton, particularly from the Dinoflagellate group. However, bacterial growth of Vibrio sp. on week-7 was insignificant, yet many shrimps were found dead with white feces during that period. The result of analysis indicated that white feces disease was caused by Dinoflagellate besides the main trigger, namely, Vibrio sp.

An intense bloom of Asterionellopsis glacialis (Family: Flagilariaceae; Class: Bacillariophyceae; Phylum: Ochrophyta) was observed in the near-shore waters at Kalpakkam, Tamil Nadu. Proliferation was supported by the favorable temperature, salinity, and nutrient levels in the coastal waters prevailing in the post-northeast monsoon period. BIOENV analysis and PCA confirmed salinity and nitrate as the key environmental factors responsible for the A. glacialis abundance. Cluster analysis further supported the distinct state of coastal water during the bloom with respect to physicochemical properties. The bloom period was floristically and faunistically richer than the pre- and post-bloom periods. The cluster and nMDS analysis confirmed the effects of bloom on plankton dynamics in the near-shore waters at Kalpakkam. The dominance of meroplankters especially, Cirripedia nauplii and Bivalvia larvae over Copepoda during the peak bloom period, was a significant result of the study. PCA ordination plot for the quantitative aspects of phytoplankton and zooplankton groups further supported the above observation. Among Copepoda, Cyclopoida and Poecilostomatoida (mostly carnivorous) exceeded the Calanoida (mostly herbivorous) during the peak bloom period unlike the reverse trend observed during other periods. Fish eggs and larvae were available in substantial numbers during the bloom which indicated their proliferation in the presence of the blooming diatom standing stock as the food material.

Within the marine fossil record, size is a fundamental trait providing information on both assemblages and individual species. Changes in size within an assemblage are largely driven by species composition typically related to environmental conditions. Changes in size of an individual species can be an indicator of health and whether optimal growth conditions (i.e. temperature, salinity and food availability) prevail. Over evolutionary timescales, individuals tend to increase in size (Cope’s rule) also altering the average size of the population.The Pliocene provides an excellent opportunity to look at environmental drivers and ecological responses to a warmer world, at high resolution and with extant species. A short glaciation phase, during marine isotope stage (MIS) M2, interrupted the Pliocene global warming between ~ 3.31 – 3.26 Ma. This event provides the ideal framework to quantify how biota, already adapted to warming conditions, respond to a short, but substantial cooling event. We analysed the size and species composition of samples collected as part of the Pliocene Research, Interpretation and Synoptic Mapping (PRISM) Project from a variety of locations around the globe. The samples cover the Atlantic, Indian and Pacific oceans at a range of latitudes (e.g. DSDP Site 521, 586, 607 and ODP Site 716, 754, 887). We measured the maximum diameter of planktonic foraminifera tests with a fully automated light microscope, enabling high resolution sampling at a multitude of sites, before, during and after the MIS M2 glaciation event. On average 2000 specimens were measured per sample, resulting in over a million analyses in total. Changes in planktonic foraminiferal assemblage composition were characterised by quantifying relative species abundances and augmented by determining the largest species.Planktonic foraminiferal assemblage size shows a general increase during the Pliocene likely related to warming temperatures. What is unclear is if this change is driven by changes in diversity due to extinction and origination, responses to environmental change or a general increase in size of species found through the record. Here we discuss reactions of species and (or) ecological groups to environmental change and determine the individual drivers of size change across the world’s oceans.

Murray-Darling Freshwater Research CentreMDFRC item.1. Contrary to that for lakes and ponds, our knowledge of the influence of planktivorous fish on zooplankton communities in rivers is slight, largely because of the general assumption that such communities are overwhelmingly regulated by physical conditions. 2. In two separate but concurrent in situ enclosure experiments, we investigated the effects of carp gudgeon (Hypseleotris spp.) and Eastern Gambusia (Gambusia holbrooki) on zooplankton communities in slackwaters of a temperate Australian floodplain river. 3. A high biomass of Hypseleotris suppressed the density of daphniid microcrustaceans, but enhanced the total density of rotifers. A high biomass of Gambusia, on the other hand, suppressed the total density of both microcrustaceans and rotifers. 4. A high biomass of planktivorous fish also reduced the density of many of the ovigerous (egg-carrying) zooplanktonic taxa. Indeed, ovigerous cyclopoid copepods were suppressed in the presence of a high biomass of Hypseleotris, even though there was no significant effect on overall (ovigerous plus non-ovigerous) density. 5. Our results imply that a high biomass of planktivorous fish can potentially influence zooplankton communities in riverine slackwaters, as in many lakes and ponds.

Murray-Darling Freshwater Research CentreMDFRC item.Planktivorous fish are important in shaping zooplankton communities in many freshwater ecosystems, and there is an intrinsic link between the active and resting forms of many zooplankton taxa. However, few field studies have considered the influence of planktivorous fish on zooplankton resting-stage communities, and none have considered this phenomenon in rivers. In two separate but concurrent 12-day experiments, we investigated the effects of Eastern Gambusia (Gambusia holbrooki Girard) and carp gudgeon (Hypseleotris spp.) on zooplankton resting-stage communities in slackwaters of an Australian floodplain river. This was achieved by setting coconut fibre mats on the bottom of the experimental enclosures and later incubating the resting stages captured. A high biomass (2.5 g m(-2)) of Gambusia suppressed the total abundance and diversity of resting-stage microcrustaceans between days 6 and 12, and the abundance of resting-stage Asplanchna spp. throughout the entire 12-day period. Furthermore, a high biomass of Hypseleotris suppressed the total diversity of resting-stage rotifers between days 0 and 6. These response patterns generally reflected changes in active populations according to the fish biomass treatment, rather than changes in dormancy induction by active individuals. This suggests that a high biomass of planktivorous fish can potentially influence zooplankton resting-stage communities in riverine slackwaters in addition to active zooplankton communities due to the inherent association between resting stage and active forms of zooplankton taxa.

La Trobe University Faculty of Science, Technology and Engineering Murray Darling Freshwater Research CentreMDFRC item.Bacterial production is important in aquatic carbon cycles because it represents a key component whereby dissolved and particulate carbon can be recycled back into food webs. Despite its acknowledged importance, few studies have examined bacterial production in lowland rivers. Since studies have suggested bacterial production is closely related to some carbon pools, we anticipated this to be the case in the Murray River, but that the timing and type of carbon inputs in the Murray River may lead to bacterial dynamics that differ from studies from other sites. Bacterial abundance and production were measured at three contrasting sites of the lowland Murray River, southeastern Australia, over an 18- month period. Bacterial abundance varied across the three sites on the Murray River and was correlated with chlorophyll a concentrations but not with temperature, nutrients, particulate organic carbon and dissolved organic carbon concentrations. Bacterial production also varied across the sites. Lowest production was at the site most immediately downstream of a large reservoir, with production generally ranging from 0.88 to 8.00 mu g CL-1 h(-1). Bacterial production in a reach within a large forest ranged from 4.00 to 17.38 mu CL-1 h(-1). Production at the reach furthest downstream ranged from 1.04 to 23.50 mu g C L-1 h(-1). Bacterial production in the Murray River was generally greater than in the European River Spree, reaches of the Meuse and Rhine without immediate impacts from major urban centres and the Amazon River, but was similar to the concentration measured in the Mississippi and Hudson Rivers. Bacterial production was closely correlated with chlorophyll a concentration and total phosphorus, but not with temperature, dissolved organic carbon, particulate organic carbon or inorganic nitrogen. Despite the differences in production and respiration measured at different sites across the Murray River, bacterial growth efficiency was very similar at the three sites. Bacterial populations in the Murray River appear to be influenced by reach-specific conditions rather than broad-scale drivers such as temperature, carbon and nutrient concentrations.

Murray-Darling Freshwater Research CentreMDFRC item.The properties of Daphnia carinata King as a grazer for use in biomanipulation trials were investigated. Mesocosm experiments suggested that in water from a lake where D. carinata was scarce, phytoplankton was nutrient-limited and the manipulated biomass of zooplankton had no effect on total chlorophyll a, whereas in water from a lake where D. carinata was dominant, nutrients were not limiting and total chlorophyll a was negatively correlated with the manipulated biomass of zooplankton. When offered lake phytoplankton in feeding trials, D. carinata consumed all items present, including colonies of cyanobacteria and long filaments of diatoms. In large outdoor tanks with natural plankton, the biovolume of prokaryotic ultraplankton (possible predecessors of cyanobacterial blooms) was consistently reduced in the presence of D. carinata. There was no evidence of an adverse effect of single-celled Microcystis aeruginosa containing the peptide toxin microcystin-LR on D. carinata grazing rates or survival. Different concentrations of microcystin-LR in solution covering the range of toxicities observed during M. aeruginosa blooms (5-500 nM) had no effect on D. carinata grazing. The suppression of phytoplankton biomass by D. carinata grazing is one of several possible mechanisms that might be considered for biomanipulation in Australia.

Murray-Darling Freshwater Research CentreMDFRC item.Both phytoplankton and bacterioplankton produce alkaline phosphatases, but the techniques currently available for discriminating between the two sources are poor, especially when samples are from turbid waters. A novel approach, based on the differential inhibition of alkaline phosphatases by various physical and chemical treatments, was assessed as a rapid and inexpensive technique for determining whether phytoplankton or bacterioplankton were the more important producers of alkaline phosphatases in turbid rivers of south-eastern Australia. Eight phytoplankton strains and 14 bacterial strains (eight isolated from the Ovens River and six isolated as bacterial contaminants of the phytoplankton cultures) were grown in laboratory culture. Rates of alkaline phosphatase activity in the bacterial cultures varied from 70% of cases) grouped separately from those of the laboratory cultures of bacteria and phytoplankton, perhaps because the microbes studied in laboratory culture were not representative of native assemblages or because the culture conditions did not mimic those in nature. Nevertheless, differential-inhibition techniques have much potential for determining the origin of the alkaline phosphatases found in natural waters, with the major factor limiting their application being the collection of valid inhibition profiles for native bacterial and algal communities.

La Trobe University Faculty of Science, Technology and Engineering Murray Darling Freshwater Research CentreMDFRC item.1. River metabolism was measured over an annual cycle at three sites distributed along a 1000 km length of the lowland Murray River, Australia.2. Whole system metabolism was measured using water column changes in dissolved oxygen concentrations while planktonic and benthic metabolism were partitioned using light-dark bottles and benthic chambers.3. Annual gross primary production (GPP) ranged from 775 to 1126 g O2 m−2 year−1 which in comparison with rivers of similar physical characteristics is moderately productive.4. Community respiration (CR) ranged from 872 to 1284 g O2 m−2 year−1 so that annual net ecosystem production (NEP) was near zero, suggesting photosynthesis and respiration were balanced and that allochthonous organic carbon played a minor role in fuelling metabolism.5. Planktonic rates of gross photosynthesis and respiration were similar to those of the total channel, indicating that plankton were responsible for much of the observed metabolism.6. Respiration rates correlated with phytoplankton standing crop (estimated as the sum of GPP plus the chlorophyll concentration in carbon units), yielding a specific respiration rate of −1.1 g O2 g C−1 day−1. The respiration rate was equivalent to 19% of the maximum rate of phytoplankton photosynthesis, which is typical of diatoms.7. The daily GPP per unit phytoplankton biomass correlated with the mean irradiance of the water column giving a constant carbon specific photon fixation rate of 0.35 gO2 g Chl a−1 day−1 per μmole photons m−2 s−1 (ca. 0.08 per mole photons m−2 on a carbon basis) indicating that light availability determined daily primary production.8. Annual phytoplankton net production (NP) estimates at two sites indicated 25 and 36 g C m−2 year−1 were available to support riverine food webs, equivalent to 6% and 11% of annual GPP.9. Metabolised organic carbon was predominantly derived from phytoplankton and was fully utilised, suggesting that food-web production was restricted by the energy supply.

Murray-Darling Freshwater Research CentreMDFRC item.The interactions of size, shape, and density of cyanobacteria result in a 5-order of magnitude difference in flotation or sinking rates which, in turn, influence the extent of their dispersion in turbulent water masses. Active mixing through resource-replete waters of high clarity favours fast-growing, small-celled species. Where photosynthetically active radiation is severely attenuated through the wind-mixed layer, species may rely on turbulent entrainment but must be adapted toward efficient light harvesting (morphological attenuation, enhanced pigmentation). In both strongly segregated waters (light- and nutrient-rich layers separated vertically) and waters experiencing high-frequency fluctuations in vertical mixing and optical depth, emphasis is placed on the ability to make rapid, buoyancy-adjusted vertical movements, favoured by large size. The cyanobacterial 1ife-forms respectively typical of these contrasted limnological systems — unicellular coccoids (e.g., Synechococcus), solitary filaments (e.g., Oscillatoria) and colonial forms (e.g., Microcystis) — illustrate the diversity of evolutionary adaptations to be discerned among the planktonic cyanobacteria and which contributes to their reputation as a prominent and successful group of organisms.

La Trobe University Faculty of Science, Technology and Engineering Murray Darling Freshwater Research CentreMDFRC item.Density-size distributions of a river zooplankton community were examined about biweekly over a year in the upper tidal freshwater portion of a regulated Australian river, specifically the Hawkesbury-Nepean, Results were compared with those of similar studies in lakes (and reservoirs) to characterize the similarities and differences in the structure and grazing function of river and lake zooplankton communities. The density-size distributions of the river zooplankton community were similar to those of lake plankton communities, in terms of a marked temporal variation in shape and overall bimodal shape. They differed in terms of the truncation of the upper body size and the absence of a significant relationship between the slope (regression coefficient) of a log-linear density-size model and environmental variables. The river zooplankton community appeared to have a high average rate of biomass increase when measured against body-mass class and a low mass-specific grazing rate, compared with those of lake communities. Because of methodological differences between studies, intersystem comparisons of size spectra and grazing rates need cautious interpretations and generalizations.

Murray-Darling Freshwater Research CentreMDFRC item.Grazing rates by a zooplankton community were measured in situ by a radiotracer cellmethod at depths of 1 m and 4 m at the upper tidal freshwater portion of a regulated river over a year.The objectives were to evaluate the likely grazing impact on the river phytoplankton community and toproduce predictive models by regressing the measured grazing rates against zooplankton biomass,temperature and food concentrations (represented by chlorophyll a). Grazing attained rates (overallaverage 0.2 day-', range 0.01-0.59 day-', expressed as instantaneous mortality rates of algal cells)comparable to those reported for lentic zooplankton communities. The measured community grazingrates were predictable largely as a function of total biomass or rotifer biomass and surface temperaturefor 1 m depth, and as a function of total biomass or juvenile copepod biomass and surface temperaturefor 4 m depth, with all-positive regression coefficients in the models. Owing to the predominance ofmicrozooplankton in the river, the impact of zooplankton community grazing appears likely to be linkedto a small-size fraction of the phytoplankton community all year. Management strategies for river waterquality may need to take account of possible functional demarcation of grazing by river zooplankton.

Objectives To characterize the abundance and relative composition of seawater bacterioplankton communities in Changle city using Illumina MiSeq sequencing and bacterial culture techniques. Methods Seawater samples and physicochemical factors were collected from the coastal zone of Changle city on 8 September 2019. Nineteen filter membranes were obtained after using a suction filtration system. We randomly selected eight samples for total seawater bacteria (SWDNA group) sequencing and three samples for active seawater bacteria (SWRNA group) sequencing by Illumina MiSeq. The remaining eight samples were used for bacterial culture and identification. Alpha diversity including species coverage (Coverage), species diversity (Shannon–Wiener and Simpson index), richness estimators (Chao1), and abundance‐based richness estimation (ACE) were calculated to assess biodiversity of seawater bacterioplankton. Beta diversity was used to evaluate the differences between samples. The species abundance differences were determined using the Wilcoxon rank‐sum test. Statistical analyses were performed in R environment. Results The Alpha diversity in the SWDNA group in each index was ACE 3206.99, Chao1 2615.12, Shannon 4.64, Simpson 0.05, and coverage 0.97; the corresponding index was ACE 1199.55, Chao1 934.75, Shannon 3.49, Simpson 0.09, and coverage 0.99. The sequencing results of seawater bacterial genes in the coastal waters of Changle city showed that the phyla of high‐abundance bacteria of both the SWDNA and SWRNA groups included Cyanobacteria, Proteobacteria, and Bacteroidetes. The main classes included Oxyphotobacteria, Alphaproteobacteria, and Gammaproteobacteria. The main genera included Synechococcus CC9902, Chloroplast, and Cyanobium_PCC‐6307. Beta diversity analysis showed a significant difference between the SWDNA and SWRNA groups (P, In the SWDNA and SWRNA groups, the dominance of the phyla were Cyanobacteria, Proteobacteria, and Bacteroides; the main classes were oxygen‐producing photobacteria, α‐proteobacteria, and γ‐proteobacteria. The predominant genera are Synechococcus_CC9902, Chloroplast, Cyanobium_PCC‐6307, Candidatus Actinomarina, Ascidiaceihabitans and HIMB11 in SWDNA; Chloroplast, Synechococcus_CC9902, HIMB11, Cyanobium_PCC‐6307, Ascidiaceihabitans, and Ralstonia in SWRNA.

A marine sediment core EW17-09 (03˚ 28’358” latitude and 96˚ 18’788” longitude, 870 m water depth, 390 cm core length) was retrieved from the western Sumatra, Simeulue sub-basin, Indonesia. Simeulue sub-basin are situated in eastern Indian Ocean, western part of Aceh Province, which is one of the outer islands in Indonesia. This sub-basin is influenced by adjacent lands in response to tectonic and climate dynamics. The dynamics of marine ecological conditions in the past is an urgent need for providing an analogy to the changes in the future conditions. In this study, the ecological conditions were examined by identifying the vertical distribution of planktonic foraminifera assemblages. This preliminary study demonstrated the presence of Globigerinoides ruber, Neogloboquadrina dutertrei, Pulleniatina obliquiloculata, Globigerina calida calida, Globigerinoides elongates, Globigerinoides cyclostomus and Globigerinoides sacculiferus in the samples. The assemblages indicate warm water conditions prevailed in the Simeulue sub-basin during the deposition of the samples. However, subtle ecological changes might have occurred in response to the dynamic of thermocline layer. Cluster analysis of planktonic foraminifera abundance and diversity resulted in three groups showing different ecological conditions. Warm water conditions, high salinity, deeper thermocline with moderate sedimentation disturbance prevailed during the deposition of lower part of the core. Oligotropic water conditions with higher temperature, lower salinity, shallower thermocline layer, and moderate sedimentation disturbance predominated during the deposition of the middle part of the core. The paleooceanography conditions of the upper part of the core are comparable to the lower part. Nevertheless, there are a shoaling of the thermocline in the end of the period. These conditions may indicate an increase in upwelling fluctuations and may represent a change in the IOD-like mean state of the Indian Ocean.

Heterosigma akashiwo is a bloom-forming planktonic flagellate that causes fish mortalities, which damages the aquaculture industry worldwide. In Chile, this species was reported for the first time ...

Epibiotic associations in the plankton community have been documented along the west and east coast of India. This report indicates a higher predominance of epibiosis along the east coast compared to the west. A total of 28 ciliates and one diatom species were reported epibiotic on the various planktonic host in the east coast, whereas only 17 ciliates and two diatoms were listed as epibiotic along the west coast. Ciliates formed the prevalent epibiotic species mainly on zooplanktonic crustacean host. Females of the host organisms were more infected due to their higher number in the population. The host specificity of various epibionts are also well-defined. The abundance of epibiotic organisms results from global warming and eutrophication and acts as indicators of ecosystem shifts.

We investigated diatom assemblages for the last 19 ka in a piston core KY07-04 PC01 collected from the northern Okinawa Trough, East China Sea. Most of the diatom taxa in the Core KY07-04 PC01 were subtropical to temperate marine species throughout the core. Pronounced turnover of major diatom groups from periphytic to planktonic taxa occurred during deglaciation between 17 and 14 ka ago. During the Last Glacial Maximum (LGM) to early deglaciation, the representative taxa were Paralia spp., a periphytic diatom abundant in continental shelves of the modern East China Sea covering the Chinese Coastal Water. Relative abundances of Paralia spp. rapidly decreased during 15–14 ka ago, corresponding to sea-level rise, displaced by planktonic taxa such as Thalassionema. Thalassionema nitzschioides varieties living in subtropical water increased since 12 ka and have reached the present level at 8 ka ago, suggesting strengthening the influences of Kuroshio water in the northern East China Sea during the early to middle Holocene. Warm planktonic diatom taxa such as Nitzschia bicapitata also gradually increased from 12 to 8 ka ago. Near the core top, a sudden increase in N. bicapitata might relate to the intensifying Kuroshio during the latest Holocene.

Metabarcoding in combination with high-throughput sequencing (HTS) allows simultaneous detection of multiple taxa by targeting single or several taxonomically informative gene regions from environmental DNA samples. In this study, a multiple-marker HTS approach was applied to investigate the plankton diversity and seasonal succession in the Baltic Sea from winter to autumn. Four different markers targeting the 16S, 18S, and 28S ribosomal RNA genes were employed, including a marker for more efficient dinoflagellate detection. Typical seasonal changes were observed in phyto- and bacterioplankton communities. In phytoplankton, the appearance patterns of selected common, dominant, or harmful species followed the patterns also confirmed based on 20 years of phytoplankton monitoring data. In the case of zooplankton, both macro- and microzooplankton species were detected. However, no seasonal patterns were detected in their appearance. In total, 15 and 2 new zoo- and phytoplankton species were detected from the Baltic Sea. HTS approach was especially useful for detecting microzooplankton species as well as for investigating the co-occurrence and potential interactions of different taxa. The results of this study further exemplify the efficiency of metabarcoding for biodiversity monitoring and the advantage of employing multiple markers through the detection of species not identifiable based on a single marker survey and/or by traditional morphology-based methods.

The aggregation of phytoplankton into marine snow provides a mechanism by which smaller particles can coagulate to form larger particles, which can be consumed at various depths or readily transported to the deep ocean and sequestered from the atmosphere on time scales of a thousand years or more. Zooplankton interacting with these large carbon-rich aggregates can obtain nutrition in environments where the phytoplankton size spectrum is small and not directly available, enhancing the possibility of obtaining adequate nutrition in environments dominated by small cells. In addition, interactions between zooplankton and marine snow can result in fragmentation, thus affecting the particle sinking rate and changing the export of carbon. Unfortunately, these interactions are understudied and poorly understood. This study focuses on how two factors – phytoplankton growth phase and species – affect copepod feeding on marine snow, providing insight into the role of this food source in planktonic trophic dynamics and export of carbon to depth. We conducted a series of grazing experiments using gut pigment and stable isotope methods to quantify the ingestion rate of the copepod, Calanus pacificus, on marine snow aggregates in comparison to their ingestion rate on individual phytoplankton. We also examined how the ingestion of copepods on marine snow was affected by the phytoplankton species and phytoplankton growth phase from which the aggregates were formed. Results demonstrate that marine snow represents a substantial food source for copepods, with ingestion rates comparable to those on individual phytoplankton as measured with both gut pigment and stable isotope analysis. We found that phytoplankton growth phase can significantly affect the ingestion of marine snow. Finally, ingestion of marine snow was affected by phytoplankton species, and while aggregates formed from Thalassiosira weissflogii resulted in consistent patterns of ingestion rate between experiments and methodologies, the same was not the case for aggregates formed from Skeletonema marinoi. These findings suggest that marine snow is likely an important source of nutrition for copepods, but that its role in planktonic food webs may differ depending on the phytoplankton community composition and the stage of phytoplankton blooms.

Arctic marine protist communities have been understudied due to challenging sampling conditions, in particular during winter and in deep waters. The aim of this study was to improve our knowledge on Arctic protist diversity through the year, in both the epipelagic (< 200 m depth) and mesopelagic zones (200–1000 m depth). Sampling campaigns were performed in 2014, during five different months, to capture the various phases of the Arctic primary production: January (winter), March (pre-bloom), May (spring bloom), August (post-bloom), and November (early winter). The cruises were undertaken west and north of the Svalbard archipelago, where warmer Atlantic waters from the West Spitsbergen Current meet cold Arctic waters from the Arctic Ocean. From each cruise, station, and depth, 50 L of seawater was collected, and the plankton was size-fractionated by serial filtration into four size fractions between 0.45–200 µm, representing picoplankton (0.45–3 µm), small and large nanoplankton (3–10 and 10–50 µm, respectively), and microplankton (50–200 µm). In addition, vertical net hauls were taken from 50 m depth to the surface at selected stations. The net hauls were fractionated into the large nanoplankton (10–50 µm) and microplankton (50–200 µm) fractions. From the plankton samples DNA was extracted, the V4 region of the 18S rRNA-gene was amplified by polymerase chain reaction (PCR) with universal eukaryote primers, and the amplicons were sequenced by Illumina high-throughput sequencing. Sequences were clustered into amplicon sequence variants (ASVs), representing protist genotypes, with the dada2 pipeline. Taxonomic classification was made against the curated Protist Ribosomal Reference database (PR2). Altogether, 6536 protist ASVs were obtained (including 54 fungal ASVs). Both ASV richness and taxonomic composition varied between size fractions, seasons, and depths. ASV richness was generally higher in the smaller fractions and higher in winter and the mesopelagic samples than in samples from the well-lit epipelagic zone during summer. During spring and summer, the phytoplankton groups diatoms, chlorophytes, and haptophytes dominated in terms of relative read abundance in the epipelagic zone. Parasitic and heterotrophic groups such as Syndiniales and certain dinoflagellates dominated in the mesopelagic zone all year, as well as in the epipelagic zone during the winter. The dataset is available at https://doi.org/10.17882/79823 (Egge et al., 2014).

Three species of dinophysoid planktonic dinoflagellates are described from the eastern Mediterranean Sea. Amphisolenia sp. aff. brevicauda was collected at 70-m depth in the Ionian Sea. This small species showed a more asymmetric midbody and a proportionally longer neck when compared to the closer relative A. brevicauda. Three individuals of Dinofurcula tricornuta sp. nov. collected at 154-m depth in the Marmara Sea are characterized by three posterior-oriented processes when compared to its congeneric species. This is the first record of the genus Dinofurcula beyond the eastern tropical Pacific Ocean. Dinophysis profunda sp. nov. collected at 500-m depth in the Ionian Sea is characterized by ovate hypotheca and a serrate crest-like left sulcal list when compared to its close relative D. alata. These findings evidence an undescribed biodiversity in the under-sampled subphotic depths.

Biophysical models of parasite dispersal are being increasingly used as a method for screening marine aquaculture developments, whether in establishment of new sites or expansion of existing sites, or planning of farmed fish health management strategies on local or regional spatial scales. How well these models reflect reality, however, is often brought into question, due to the difficulties in validating their outputs. Larval parasitic sea lice can spend up to around 14 d in the water column, as a result potentially travelling several 10s of km between farms. Lice distribution in the water column is typically patchy and low density. Furthermore, infection can occur from lice carried by wild fish. Combined with rapid population turnover and larval exchange between farms, this causes difficulties in attributing links between juvenile lice and their sources. We sought to validate a biophysical model of sea lice dispersal using plankton trawl abundance data and farm site juvenile lice counts. Unusually high farm lice abundances over the study period allowed model predictions of larval density to be compared with trawled samples, in addition to mapping the link between parent and offspring lice counts found on farm sites. We compared the prediction of the larval dispersal model with a site neighbourhood-based metric of infection pressure. Our results validate the ability of the model to predict variation in larval density over time and space and suggest an exponential relationship between estimated infection pressure and observed site juvenile count.

An investigation of changes in lake diatom assemblages and diversity with water depth can help determine whether the biodiversity of a single sediment core is representative of that of the entire lake, as well as can improve our understanding of the relationship between diatom assemblages and water depth. In this study, Huguang Maar Lake in Southern China was investigated in order to explore the spatial patterns of diatom diversity and diatom assemblages of 95 surface sediment samples from different locations and depth zones within the lake. The results show an essentially constant diatom diversity, dominated by planktonic diatoms, in the open deep water zone (OD), and consistent diatom diversity in the northern gently-sloping shallow water zone (NS). However, there is a much higher diatom diversity in different microhabitats in the southern and western shallow water zone (SWS), where the bathymetry is much steeper. This difference may reflect the influence of the bathymetry on the occurrence of sediment slumping. In the steeply-sloping SWS zone, frequently influenced by wave action and sediment slumping, diatom diversity is less representative of that of the entire lake, possibly due to the presence of diatoms from different sources and of different depositional ages. The results indicate that for relatively strongly mixed lakes with a simple morphometry, water depth has little influence on diatom diversity; however, the possible influence of local lake basin topography should be considered when reconstructing past diatom diversity changes from sediment cores.

Marine and freshwater ecosystems differ in persistence, size, population connectivity, and the variance in physical and biotic conditions they experience. These differences may select for differing reproductive modes, life histories, dispersal strategies, and chemically cued recruitment behaviors. In marine systems, adults are commonly less mobile, while larvae spend hours to weeks to months dispersing in the plankton and may move over great distances. It is these immature larval stages that must select appropriate recruitment sites in marine environments. In freshwater systems, the fully developed adults more commonly disperse over greater distances, and it is usually adults that determine juvenile recruitment sites via their placement of larvae or fertilized eggs. Thus, in terms of large-scale habitat choices involving chemical cuing, adult stages should be selected to detect and react to habitat cues among most freshwater species, while juveniles should play this role among most marine species. Few studies assess this hypothesis, but adults of freshwater organisms as different as mosquitoes and frogs do key on chemical cues to select sites for depositing eggs or larvae, while chemical cuing of recruitment in marine systems occurs primarily among the larval stages of the numerous fishes and marine invertebrates investigated to date. Cues to general habitat features, to predators or competitors, and to specific prey or hosts have all been shown to affect recruitment. Here, we review chemically mediated recruitment in marine versus freshwater systems, summarizing what is known and suggesting unknowns that may be productive to investigate.

Two diets were formulated, a low lysine (LowL) and a balanced lysine diet (BalL), containing 9.10 and 13.10 g lysine kg−1 feed, respectively. Twenty fish (30.2 ± 1.9 g) per tank were stocked in 110-L tanks, mounted in a recycling aquaculture system (RAS), and nine hundred fish (17.2 ± 1.6 g) per pond were stocked in 200 m2 fertilized ponds (FPS). Four replicates in RAS and five replicates in FPS were assigned for each diet tested. Fish were fed with the experimental diets at a feeding rate based on metabolic body weight, twice daily for 70 days. Fish fed the BalL diet in RAS had a higher yield (kg m−3), specific growth rate, nitrogen retention efficiency (%), protein efficiency ratio (g g−1 protein), protein content and essential amino acid content, as well as a better feed conversion ratio (p .05) affect the growth indices of nutrient utilization, survival (%), body composition and essential amino acids or nitrogen utilization efficiency. Percentage compositions of plankton in the gut contents and plankton abundances in water were approximately the same between diets. The Pearson correlation coefficient (r) between plankton abundance and growth in fish fed the LowL diet was.761 and −.961 for phytoplankton and zooplankton, respectively, compared with.50 and.54 in fish fed the BalL diet. The contribution of the natural food to nitrogen gain was 30% in fish fed the LowL diet, compared with 21% in fish fed the BalL diet (p

The Arctic Ocean (including sub-Arctic margins) is one of the fastest changing ecosystems affected by climate change. However, much remains unknown about its ecosystematic functioning, trophic interactions, and species diversity. Plankton communities have been studied to some extent, but gelatinous zooplankton (GZ; cnidarians, ctenophores, pelagic tunicates), a group that may be favoured by ocean warming, were widely neglected and only recently gained more attention. Plankton assemblages and dynamics around Iceland are well studied, while limited baseline information on GZ ecology are regionally available. In the present study, we aim to describe the seasonal changes in GZ assemblages in two North-western fjords that are representative of other fjords in Iceland. Near-surface horizontal net tows were performed regularly between April and September 2008 at five stations. In total, > 12,000 specimens of 14 species (ten hydromedusae, two scyphomedusae, one ctenophore) were collected, with peak abundances of 1937 ind. 1000 m−3 by Clytia sp. in June. The majority (10 species) of GZ was characterised by a meroplanktonic life cycle. The total abundance of GZ increased from April to June (like the species richness), while scyphomedusae and ctenophore abundances decreased towards September. The hydromedusa abundance remained high until September. While evenness and diversity indices were high in April and May, they decreased in June and remained at a lower level thereafter. Non-metric multidimensional scaling revealed that month, but not sampling station, had a significant effect on the assemblage composition, and temperature was found to have a marginally significant effect on structuring the GZ assemblage.

Marine biodiversity is the essential foundation for the structure and functioning of ocean ecosystems and for providing the full range of ecosystem services that benefit humans on local, regional, and global scales. These benefits include many visible as well as unseen functions and services such as the oxygen we breathe, the seafood we eat, the support of local livelihoods, the marine plants storing 'blue' carbon and protecting our shorelines, the medical and biochemical compounds found in marine species, the coral reefs we explore when scuba diving, and the charismatic creatures inspiring our lives. All these benefits are provided by the diversity and interplay of ocean life, from tiny plankton and bacteria to 30 metre whales and giant kelp.

Unraveling planktonic community patterns and their linkage with the surrounding ecology is essential for aquatic resource management. Studies on the tintinnid microzooplankton in most of the marine waters of Malaysian South China Sea (SCS) are scarce though the trophic role of this community is well established. Thus, we aimed to investigate on spatiotemporal pattern of composition, abundance, and biomass of tintinnid, and how this community patterns are regulated with the basic ecological parameters. A total of 46 species were recorded, mostly in southwest monsoon (33 species) during the study period from May 2016 to April 2017. Tintinnopsis was counted as major genera with 19 species, and Tintinnopsis radix, a species that reported as neritic-estuarine origin calculated as the most abundant (11%) in our study. Both the space and time were equally responsible for differences in species richness, diversity, abundance, and biomass. However, species richness variation was not influenced by space–time interaction, whereas we observed season (time) and species size worked as a strong factor in terms of biomass variations. Accordingly, the higher mean abundance (Station 3; 132,116 ind m−3 in southwest monsoon) did not scale up to the bigger mean biomass (Station 4; 1.317 µgC L−1 in Inter-monsoon April). Among the ecological variables, the strongest influence was observed in the tintinnid community by pH, dissolved oxygen and salinity mostly during southwest monsoon around Bintulu-Mukah areas. Similarly, species-specific affinity to pH was also observed by most of the species. In addition, Favella campanula showed affinity to salinity, turbidity, and conductivity, while T. cylindrica and T. gracilis were driven by the temperature and dissolved oxygen. The findings of this research may help to explore comprehensive food web dynamics in future ecosystem studies in SCS region.

Fil: Garcia Chapori, Natalia Luz. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Oficina de Coordinacion Administrativa Ciudad Universitaria. Instituto de Estudios Andinos "Don Pablo Groeber". Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Estudios Andinos "Don Pablo Groeber"; Argentina

Nile tilapia feed on plankton in natural environments. This food source can be increased in ponds through fertilization and can reduce feed expenses or improve fish performance when used as supplementary food. Organic fertilization is an alternative to commercial fertilization; however, its use increases concerns regarding water quality and sanitary aspects. This study aimed to evaluate the effects of the use of poultry litter as organic fertilizer on the physical and chemical parameters of water, gill ectoparasite metazoan abundance, and growth of Nile tilapia (Oreochromis niloticus) during the culture cycle lasting 240 days. Four earthen ponds, two fertilized with poultry litter and two non-fertilized ponds, as fertilized and non-fertilized treatments, respectively, were used. Stocking density was 3 fish per m2 with an average initial weight of 0.64 ± 0.15 g. The mean water quality values and the growth performance parameters of Nile tilapia did not show significant differences between the two treatments. The gill parasites found in the fish belonged to the class Monogenea, comprising two genera, Cichlidogyrus and Scutogyrus, with significant differences between treatments. The non-fertilized treatment showed a high abundance of parasites throughout the culture cycle months, with peak abundance in the months with low concentrations of dissolved oxygen in the water.

23 pages, 9 figures, 7 tables.-- This is an open access article distributed under the Creative Commons Attribution License, The Galician shelf (northwestern Iberian Peninsula) is a highly dynamic area with an important multi-species fisheries industry that exploits resources from several habitats, characterized by being not only highly diverse, rich, and productive but also seasonally and interannually variable. Early life stages of different species are distributed throughout the year, with fluctuating abundances and community composition. Likewise, the influence of environmental factors and processes on larval production and survival remains unknown. Sampling was carried out in July 2012, and all the larvae obtained were identified to establish the specific composition of the community in a summer upwelling scenario. The results show no zonation in the species distribution, a consequence of the mixing effects of the upwelling and eddies, with high diversity but low abundance, which render in a slight predominance of a few species. Due to the dependence of planktonic populations on upwelling events, which was not highly pronounced in 2012, we cannot conclude that this was a typical conformation of the Galician summer larval fish community, but it is a first approach to comprehend the community composition, This work was funded by the Spanish research project CRAMER (CTM2010-21856-CO3-02), the Galician research project ECOPREGA (10MMA602021PR), and the “Mobility grant (Research, innovation and growth plan 2011-2015, I2C) from the Innovation agency of the Xunta de Galicia. File 20/2014”

The article presents the analysis of biological parameters of parthenogenetics of Artemia crustaceans of the hypergaline reservoirs of Kazakhstan. In the lakes under study there are shown the changes of the total crustacean biomass decreasing from high-productive to low-productive. Most of the reservoirs with Artemia in Kazakhstan are characterized by the presence of Artemia parthenogenetic populations with the absence or extremely small presence of males. The aggregation of males in significant numbers may indicate the tension of the ecological situation in the reservoirs and the desire of the population to increase the survival and stability of the offspring. It has been stated that all age periods of crustacean maturation are found in the reservoirs. At the same time, the basis of Artemia populations in all studied lakes are the youngest stages - nauplius, which form 53-86% of the total number of Artemias. In lakes Artemia crustaceans are presented by bisexual parthenogenetic race, with all age stages of development during the summer - autumnal period of observations. The hydrochemical mode of hypergaline lakes of Karabassky floods is favorable for activity of Artemia Branchiopoda crustaceans. The size of crustacean biomass populations in Lake Balhash change on seasons ranging from low to very high. Lake No. 1 is highly productive in Artemias in the summer, and lake No. 2 - in the spring. Such difference in temporary aspect is caused by existence of various generations in the populations of the crustaceans on seasons. The data obtained prove the high potential of the studied small reservoirs of the Balkhash region in relation to autumn plankton cysts

Bu çalışma da Çanakkale Boğazı'ında (Dardanel) müsilaj oluşumu sırasında planktonik toplulukların kompozisyonları metagenomik yaklaşımla araştırılmıştır. Müsilaj örnekleri, Çanakkale Boğazı'nın üç farklı istasyonunda (İstasyon 1: 40°15'22.53"K, 26°40'43.58"D; İstasyon 2: 40°10'59.21"K 26°37'81.17"D; İstasyon 3: 40°11'15.67"K, 26°39'90.81"D) yoğun müsilaj oluşumu gözlemlenen Mayıs 2021'de toplanmıştır. Filum düzeyinde toplam sekans sayısının 86.68% ini kapsayan baskın planktonik ökaryotlar, Dinoflagellata (%38.57), Protalveolata (%15.03), Diatomea (%12.41), Nematozoa (%8.44), Apicomplexa (%6.79) ve Chlorophyta (%5.43) olarak belirlenmiştir. En baskın OTU'ler (>%10), Alexandrium ve Syndiniales_Group_II olup, diğer baskın OTU'lar (>%2) ise Viscosia sp., Lankesteria, Arcocellulus, Thalassiosira ve Nannochloris olmuştur.Bu çalışma, Türkiye'de meydana gelen bir müsilaj olayı sırasında Çanakkale Boğazı'nda planktonik toplulukların durumunu netleştirmiştir. Sonuç olarak, en baskın cinsin müsilaj üretme kabiliyeti olduğu bilinen Alexandrium olduğu belirlenmiştir. Bazı Alexandrium türleri toksin üretebilir, insan sağlığı üzerinde ciddi etkilere neden olabilir ve çift kabuklu, karides ve balık ölümlerine yol açabilir. Bu nedenle müsilaj yapısındaki Alexandrium toksinlerinin belirlenmesi için daha detaylı bir çalışmaya ihtiyaç vardır. Ayrıca elde edilen müsilajın ağır metal içeriği araştırılmıştır. Müsilajın yapısındaki As ve Cr konsantrasyonları atıklar için belirlenen düzenli depolama sahalarına bertaraf etme sınırlarının üzerindedir. Bu nedenle deniz yüzeyinden toplanan müsilajın düzenli depolama sahalarına gönderilmeden önce ağır metal içeriği kontrol edilmelidir.

In order to complete the information related to the little studied deep-sea planktonic fauna of western Mexico, samples from a wide depth range (surface to 1550 m depth) were obtained using different gear. Six species and 108 individuals of hyperiid amphipods of the family Amphithyridae were collected at 26 localities, including a new species of Amphithyropsis Zeidler, 2016, which is herein described based on an adult male and a gravid female. Other species include Amphithyrus bispinosus Claus, 1879, the most abundant and frequently collected species (70 specimens at 17 localities), A. muratus Volkov, 1982 (11 specimens at 8 localities), A. sculpturatus Claus, 1879 (14 specimens at 7 localities), Paralycaea gracilis Claus, 1879 (10 specimens from 6 localities), and P. hoylei Stebbing, 1888 (one specimen from one locality). Worldwide and regional distributions are provided for each species.

Polar cod and saffron cod are dominant components of the fish community in the Chukchi Sea and are ecologically important forage fishes linking plankton to upper-level consumers. In 2017, we conducted a study as part of the Arctic Integrated Ecosystem Research Program to characterize the distribution, abundance, and growth of polar cod and saffron cod early life history stages (ELHS) in late spring and late summer in the Chukchi Sea. Ship-based plankton tows showed that polar cod and saffron cod larvae were centered in Kotzebue Sound in the late spring. By late summer, polar cod juveniles were most abundant in the offshore areas of the northern Chukchi Sea, whereas saffron cod were distributed nearshore in the southern Chukchi Sea around Cape Lisburne. Empirical fish collections were paired with an individual-based biophysical transport model to examine connectivity and relate changes in seasonal distribution to potential environmental variables. Modeled drift trajectories and growth in spring for polar cod and saffron cod matched well with empirical observations, especially along the northern coastline of Kotzebue Sound, offshore of Point Hope/Cape Lisburne. Given the coherence between modeled and observed distributions, Kotzebue Sound is likely a source of gadid ELHS in the nearshore areas of the Chukchi Sea and offshore of Cape Lisburne/Point Hope, although it is not the likely source of polar cod over Hanna Shoal in the late summer. This is the first study to examine seasonal distribution, abundance, and growth of polar cod and saffron cod in the US Arctic and provides data necessary to evaluate the impacts of climate change on forage fishes in the Arctic.

According to the study of summer phytoplankton of the Ob River, 153 new species and intraspecific taxa(SIT) of algae from 8 divisions were found, including Cyanoprokaryota – 14, Dinophyta – 2, Chrysophyta – 17, Xantophyta –6, Euglenophyta – 34, Bacillariophyta – 2, Chlorophyta – 72, Charophyta – 6. New taxa are dominated by small-cell greenalgae, phytoflagellates and non-heterocyst cyanoprokaryotes. The intensive succession of the phytoplanktocenosis speciescomposition and the taxonomic structure of the new SIT algae are signs of anthropogenic eutrophication.

Over the past decades, two key grazers in the Southern Ocean (SO), krill and salps, have experienced drastic changes in their distribution and abundance, leading to increasing overlap of their habitats. Both species occupy different ecological niches and long-term shifts in their distributions are expected to have cascading effects on the SO ecosystem. However, studies directly comparing krill and salps are lacking. Here, we provide a direct comparison of the diet and fecal pellet composition of krill and salps using 18S metabarcoding and fatty acid markers. Neither species’ diet reflected the composition of the plankton community, suggesting that in contrast to the accepted paradigm, not only krill but also salps are selective feeders. Moreover, we found that krill and salps had broadly similar diets, potentially enhancing the competition between both species. This could be augmented by salps’ ability to rapidly reproduce in favorable conditions, posing further risks to krill populations.

Background Wetlands are transition zones between aquatic and terrestrial environments of Opa Reservoir Obafemi Awolowo University, Ile-Ife, Nigeria, threatened by increase in agricultural practices and urbanization within the catchment area. A critical appraisal of the current ecological integrity of the wetlands using planktonic composition and community structure which are formidable to sustaining wetlands is essential, hence this study. Result A total of 104 plankton species comprises of 68 species of phytoplankton and 36 species of zooplankton were recorded from the wetlands. In each sampled location and during the sampling period, Bacillariophyta had the highest occurrence among the phytoplankton, while Rotifera recorded the highest occurrence among the zooplankton. Generally, Synedra ulna and copepod (cyclopoid) Nauplius, respectively, were the most common phytoplankton and zooplankton recorded during the period of study. Analyses also showed that the phytoplankton had a higher species occurrence and abundance (65.3% and 98.18%, respectively) than the zooplankton (34.6% and 1.82%, respectively). Diversity indices (Shannon–Wiener, Margalef, and Simpson) analyses of both plankton groups revealed that the wetlands were generally polluted. Conclusion The study concluded that the ability of the wetlands to support and maintain a balanced adaptive community of plankton with species composition and diversity is being eroded due to anthropogenic activities in the wetland areas. This could have some ecological and socioeconomic implications considering the fact that they are intrinsically a part of the adjoining reservoir which provides many ecosystem services.

The Rashrashiyah Formation of the Sirhan Basin in northern Saudi Arabia contains diverse assemblages of planktonic foraminifera. We examined the biostratigraphy, stratigraphic range and preservation of upper Eocene planktonic foraminifera. Assemblages are well-preserved and diverse, with 40 species and 11 genera. All samples are assigned to the Priabonian Globigerinatheka semiinvoluta Highest Occurrence Zone (E14), consistent with calcareous nannofossil biostratigraphy indicating Zone CNE17. Well-preserved planktonic foraminifera assemblages from the lower part of the upper Eocene are rare worldwide. Our study provides new insights into the stratigraphic ranges of many species. We find older (Zone E14) stratigraphic occurrences of several species of Globoturborotalita previously thought to have evolved in the latest Eocene (Zone E15, E16) or Oligocene; these include G. barbula, G. cancellata, G. gnaucki, G. pseudopraebulloides, and G. paracancellata. Older stratigraphic occurrences for Dentoglobigerina taci and Subbotina projecta are also found, and Globigerinatheka kugleri occurs at a younger stratigraphic level than previously proposed. Our revisions to stratigraphic ranges indicate that the late Eocene had a higher tropical–subtropical diversity of planktonic foraminifera than hitherto reported.

To reconstruct the climatic fluctuations that occurred in the middle latitudes of the Northern Hemisphere in the Atlantic Ocean in the Campanian Age, the systematic composition of the shells of planktonic foraminifera was studied from core samples from seven deep-water drilling holes. The identified foraminiferal assemblages are assigned to two types (boreal and intermediate) and one subtype (warm boreal) thanatocenosis. On the basis of their spatial distribution, the position of climatic zones for sections of the early, middle, beginning and end of the late Campanian was determined. Different climatic zones were characterized by different types of water masses. Within the studied water area, during most of the studied age interval, two climatic zones were developed: intermediate and boreal. In the Early and Middle Campanian, the boundary between them was in the southern part of the region under consideration. At the beginning of the late Campanian, this border sharply shifted to the north. A short-term Late Campanian warming began. At the end of the late Campanian, the temperature dropped sharply. An intermediate type of thanatocenosis has not been identified. Even in the southernmost part of the water area, the warmboreal subzone prevailed. The obtained reconstructions are confirmed by our own and published data of oxygen isotope analysis.

Background Coastal aquatic ecosystems include chemically distinct, but highly interconnected environments. Across a freshwater-to-marine transect, aquatic communities are exposed to large variations in salinity and nutrient availability as tidal cycles create periodic fluctuations in local conditions. These factors are predicted to strongly influence the resident microbial community structure and functioning, and alter the structure of aquatic food webs and biogeochemical cycles. Nevertheless, little is known about the spatial distribution of metabolic properties across salinity gradients, and no study has simultaneously surveyed the sediment and water environments. Here, we determined patterns and drivers of benthic and planktonic prokaryotic and microeukaryotic community assembly across a river and tidal lagoon system by collecting sediments and planktonic biomass at nine shallow subtidal sites in the summer. Genomic and transcriptomic analyses, alongside a suite of complementary geochemical data, were used to determine patterns in the distribution of taxa, mechanisms of salt tolerance, and nutrient cycling. Results Taxonomic and metabolic profiles related to salt tolerance and nutrient cycling of the aquatic microbiome were found to decrease in similarity with increasing salinity, and distinct trends in diversity were observed between the water column and sediment. Non-saline and saline communities adopted divergent strategies for osmoregulation, with an increase in osmoregulation-related transcript expression as salinity increased in the water column due to lineage-specific adaptations to salt tolerance. Results indicated a transition from phosphate limitation in freshwater habitats to nutrient-rich conditions in the brackish zone, where distinct carbon, nitrogen and sulfur cycling processes dominated. Phosphorus acquisition-related activity was highest in the freshwater zone, along with dissimilatory nitrate reduction to ammonium in freshwater sediment. Activity associated with denitrification, sulfur metabolism and photosynthesis were instead highest in the brackish zone, where photosynthesis was dominated by distinct microeukaryotes in water (Cryptophyta) and sediment (diatoms). Despite microeukaryotes and archaea being rare relative to bacteria, results indicate that they contributed more to photosynthesis and ammonia oxidation, respectively. Conclusions Our study demonstrates clear freshwater–saline and sediment–water ecosystem boundaries in an interconnected coastal aquatic system and provides a framework for understanding the relative importance of salinity, planktonic-versus-benthic habitats and nutrient availability in shaping aquatic microbial metabolic processes, particularly in tidal lagoon systems.

Deep-sea hemichordates Torquaratoridae gen. sp. reach high abundance up to 12 spec. m–2 at the depths of 1830–2130 m on the slope of the Volcanologists Massif in the south-western part of the Bering Sea, dominating in the benthic community at these depths. Their abundance exceeds by two orders the values recorded earlier. In order to clarify this phenomenon, we examined the gut contents of Torquaratoridae gen. sp. The detritus particles and frustules of planktonic diatoms Thalassiosira, Coscinodiscus, Actinocyclus, Chaetoceros, Neodenticula, and Grammatophora were the most common in the gut, as well as the remains of skeletons of benthic invertebrates with little admixture of mineral particles. According to obtained data, Torquaratoridae gen. sp. are mobile deposit feeders with high selectivity to fresh phytodetritus, able to compete with holothurians occupying similar trophic niche. Unusually high abundance of acorn worms is apparently related to high organic matter flux to the seafloor as a result of spring phytoplankton bloom in the surface water layer of the Bering Sea.