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The effects of lake browning on trophic functioning of planktonic food webs are not fully understood. We studied the effects of browning on the response patterns of polyunsaturated fatty acids and n−3/n−6 ratio in seston and compared them between boreal and temperate lakes. We also compared the regional differences and the effects of lake browning on the reliance of zooplankton on heterotrophic microbial pathways and the mass fractions of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) in zooplankton. Lake browning was associated with increasing phytoplankton biomass and concentrations of EPA and DHA in both temperate and boreal lakes, but the seston n−3/n−6 ratio was lower in temperate than boreal lakes, most likely due the differences in phytoplankton community composition. The browning-induced increase in phytoplankton biomass was associated with increased reliance of zooplankton on a heterotrophic microbial pathway for both cladocerans and copepods in boreal and temperate lakes. This increased reliance on the heterotrophic microbial diet was correlated with a decrease in the EPA and DHA mass fractions in temperate copepods and a decrease in the n−3/n−6 ratio in boreal cladocerans and copepods. Our results indicate that although phytoplankton responses to lake browning were similar across regions, this did not directly cascade to the next trophic level, where zooplankton responses were highly taxa- and region-specific. These results indicate that lake browning should be considered as an overarching moderator that is linked to, e.g., nutrient increases, which have more immediate consequences on trophic interactions at the phytoplankton–zooplankton interface.

Aspergillus spp. is the most common clinical pathogen of invasive fungal infection with high mortality. Existing treatments for Aspergillus spp. infection are still inefficient and accompanied by drug resistance, so it is still urgent to find new treatment approaches. The antiarrhythmic drug amiodarone (AMD) has demonstrated antifungal activity against a range of fungi. This study evaluated the efficacy of AMD in combination with triazoles for Aspergillus spp. infection. We tested the combined effect of AMD and three triazole drugs, namely, itraconazole (ITR), voriconazole (VRC), and posaconazole (POS), on the planktonic cells and biofilms of 20 strains of Aspergillus spp. via a checkerboard microdilution assay derived from 96-well plate-based method. Our results reveal that the combination of AMD with ITR or POS against Aspergillus biofilms has synergistic fungicidal effects. By contrast, the combination of AMD with VRC exhibits no antagonistic and synergistic effects. In this way, the use of AMD in combination with ITR or POS could be an effective adjunctive treatment for Aspergillus spp. infection.

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.

Complex assemblages of microbes in the surface ocean are responsible for approximately half of global carbon fixation. The persistence of high taxonomic diversity despite competition for a small suite of relatively homogeneously distributed nutrients, that is, 'the paradox of the plankton', represents a long-standing challenge for ecological theory. Here we find evidence consistent with temporal niche partitioning of nitrogen assimilation processes over a diel cycle in the North Pacific Subtropical Gyre. We jointly analysed transcript abundances, lipids and metabolites and discovered that a small number of diel archetypes can explain pervasive periodic dynamics. Metabolic pathway analysis of identified diel signals revealed asynchronous timing in the transcription of nitrogen uptake and assimilation genes among different microbial groups-cyanobacteria, heterotrophic bacteria and eukaryotes. This temporal niche partitioning of nitrogen uptake emerged despite synchronous transcription of photosynthesis and central carbon metabolism genes and associated macromolecular abundances. Temporal niche partitioning may be a mechanism by which microorganisms in the open ocean mitigate competition for scarce resources, supporting community coexistence.

Fjords in Svalbard are sensitive to the enhanced climate warming-induced glacial meltwater discharge (fresher, nutrient-rich, turbid) that influences its hydrography and biological processes. This study attempts to explain the impacts of underwater light environment and nutrient limitation on the phytoplankton biomass, composition, and light absorption in the sunlit zone of the Kongsfjorden (KG)–Krossfjorden (KR) twin fjord ecosystem during summer when the meltwater discharge is at maximum. Observations conducted in two phases in each fjord revealed pronounced spatial hydrographic variations between the phases and among the fjords. Intrusion of warm Atlantic water into both fjords and occurrence of subsurface chlorophyll maxima were observed. Meltwater-induced higher concentrations of optically active constituents in KG resulted in a comparatively shallow euphotic zone than KR. Nitrate and silicate limitation (N/P 1, Si/P

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.

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.

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.

Ocean dynamics in the equatorial Pacific drive tropical climate patterns that affect marine and terrestrial ecosystems worldwide. How this region will respond to global warming has profound implications for global climate, economic stability and ecosystem health. As a result, numerous studies have investigated equatorial Pacific dynamics during the Pliocene (5.3–2.6 million years ago) and late Miocene (around 6 million years ago) as an analogue for the future behaviour of the region under global warming1–12. Palaeoceanographic records from this time present an apparent paradox with proxy evidence of a reduced east–west sea surface temperature gradient along the equatorial Pacific1,3,7,8—indicative of reduced wind-driven upwelling—conflicting with evidence of enhanced biological productivity in the east Pacific13–15 that typically results from stronger upwelling. Here we reconcile these observations by providing new evidence for a radically different-from-modern circulation regime in the early Pliocene/late Miocene16 that results in older, more acidic and more nutrient-rich water reaching the equatorial Pacific. These results provide a mechanism for enhanced productivity in the early Pliocene/late Miocene east Pacific even in the presence of weaker wind-driven upwelling. Our findings shed new light on equatorial Pacific dynamics and help to constrain the potential changes they will undergo in the near future, given that the Earth is expected to reach Pliocene-like levels of warming in the next century. New proxy data for ocean pH and an ocean–atmosphere model show that a radically different ocean circulation led to decoupling of ocean productivity and upwelling in the equatorial Pacific Ocean 3–6 million years ago.

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.

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.

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.

To explore temporal and spatial effects on the planktonic prokaryotic community composition (PCC) in the coastal region of the Bohai Sea, surface water samples were collected from 12 to 28 regularly distributed sites in Bohai Bay across 3 months from different seasons to characterize the PCC using high-throughput sequencing of the 16S rRNA V4 region. Prokaryotic α- and β-diversity showed significant temporal variation during the three sampling months. VPA analysis based on both weighted and unweighted UniFrac distances exhibited a shift of environmental and spatial effects on PCC variation with temporal variation. Quantification analysis of assembly processes on community turn over showed that “heterogeneous selection” dominated for PCC temporal variation, with basic abiotic parameters such as temperature, pH, ammonia nitrogen as the driving factors. Analysis of seasonal features showed that seasonal specific OTUs (ssOTUs) exhibited different seasonal attributions under the same phylum; meanwhile, the ssOTUs showed significant correlations with the driving environmental factors, which suggested that finer-level analysis was needed to more strictly reflect the temporal variation. Moreover, predicted nitrogen and sulfur metabolism were significantly shifted during the temporal variation. Our results clearly showed that seasonally varied environmental factors drive the “heterogeneous selection” process for PCC assembly in seawaters of Bohai Bay during different sampling seasons.

Global warming is rapidly warming seawater and introducing acidification that adversely affects marine ecosystems. Consequently, temperature-sensitive fishery resources are under great threat, and if the current situation continues, global marine ecosystems could turn into an ecological desert by the end of the century. In this paper, we first formulate a nonlinear dynamic mathematical model to illustrate the adverse effects of global warming and rapid concentrations of greenhouse gas (GHG) on marine ecosystems. We then develop a control system adopting coastal forestation and plankton nutrients as two control techniques. Here, coastal forestation is adopted to lessen the concentration GHGs by absorbing carbon dioxide through photosynthesis, whereas plankton nutrients are applied to improve planktonic diversity that can provide more food to marine fishes. The purpose of the control system is to increase fish population in marine ecosystems by providing a suitable environment, i.e., proper temperature, low acidity, and sufficient food. The control system and how it can balance the situation are verified by analysis. We confirm the results by examining different cases compared with other articles. Results disclose that the control system can improve marine ecosystems increasing plankton’s density and fishery resources and reduce global warming and GHGs concentration. The results further show that the system is more effective if both control strategies are applied together instead of just one. Overall, this study suggests that fish population in marine ecosystems can be increased and the adverse effects of global warming can be reduced by implementing adequate coastal forestation and plankton nutrients.

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.

We investigated the transfer of radiocesium and its behavior in living cells and cellular debris in a Chlamydomonas spp. bloom in a pond located approximately 5 km from the Fukushima Dai-ichi Nuclear Power Plant. A microalgal bloom in the pond was the dominant factor in determining the radiocesium concentration (Bq/L) of the > 0.45 μm pond water fraction. The water-to-algae transfer factor [(137Cs concentration Bq/kg>0.45 μm fraction) × (137Cs concentration Bq/L 0.45 μm) and water in rivers in Fukushima [(137Cs concentration Bq/kg>0.45 μm fraction) × (137Cs concentration Bq/L

To understand the community structure and the functional dynamics of phytoplankton over the long term, it is essential to identify rapid changes in the properties of Antarctic phytoplankton communities in relation to ongoing changes in environmental factors due to climate change. This study investigated short-term variability in the phytoplankton biomass and its composition over the summer of 2010 when the sea surface temperature was lowest and chlorophyll-a (chl-a) concentrations were the highest, relative to a 15-year monitoring period (1996–2011). We assessed the intraseasonal variability of the phytoplankton assemblage structure and its synchrony with changes in the main environmental variables in Marian Cove of King George Island, Antarctica. Chlorophyll-a concentrations in summer 2010 (January–February) were significantly higher (up to 24 μg L−1) when the high phytoplankton carbon biomass (603 μg C L−1) was dominated by the sympagic diatom Navicula glaciei, the benthic diatoms Licmophora belgicae and Fragilaria striatula, the planktonic diatoms Thalassiosira antarctica and Thalassiosira spp. (cell size

We inferred paleoenvironmental conditions in Lake Inawashiro-ko, Japan, over the past 1700 years, using diatom assemblages in the uppermost 2 m of sediment core INW2012. The core was characterized by three diatom zones: Zone 3 (302–1556 CE) was dominated by the planktonic taxon Aulacoseira nivalis; Zone 2 (1556–1991 CE) was predominantly planktonic Cyclotella radiosa and Aulacoseira subarctica; Zone 1 (1991–2012 CE) had highest relative abundance of Fragilaria neoproducta, accompanied by Cyclotella radiosa and Aulacoseira subarctica. Correlations between recorded diatom assemblages and water quality in previous studies enabled us to infer past environmental conditions, which indicate the lake became more eutrophic over the past ~ 30 years. Support for this inference comes from the predominance of benthic Fragilaria neoproducta in the limnetic assemblage of Zone 1. The habitat of F. neoproducta expanded from the littoral zone to offshore areas as a result of progressive eutrophication. The diatom record also suggests that alkalization of Lake Inawashiro-ko occurred over the past 1700 years. If, however, most production took place in the littoral zone, past pH values throughout much of the lake may have been lower than those indicated by the diatom assemblages. This points to the need for more diatom-based paleoenvironmental studies in lakes that display a broad range of environmental conditions across space, i.e. from the littoral to the limnetic zone.

The Gulf of Mannar (GoM), located between India and Sri Lanka, has astonishing faunal richness and diversity. Two oceanographic data sets supplemented with satellite remote sensing observations are discussed here to show the unique ecological setting in the GoM sustaining a rich and diverse fauna. We tested the hypothesis that a specific stretch of a large marine environment behaves differently from the rest of the region due to its peculiar geographical position. Primarily, unlike the adjacent Indian southwestern shelf in the Southeastern Arabian Sea, oxygen deficiency associated with coastal upwelling imparting physiological stress to marine fauna does not occur in the GoM. Secondly, the GoM along the Indian coastline receives an adequate amount of primary (plankton) food from the Arabian Sea and the Bay of Bengal through the advected water associated with the seasonally reversing surface currents. Thirdly, the GoM water has high transparency, aerated sandy seafloor conducive for the growth of diverse corals and much sensitive fauna. All these indicate that an astonishingly rich and diverse aquatic fauna in the GoM is a biological manifestation of a conducive geographical setting and propose that similar other environments worldwide, protected from oxygen deficiency, might also be functioning as a refuge for marine life.

As a consequence of difficulties in mass culturing dinoflagellates, there have been few ecological studies and little information on the interactions of microbial planktonic communities with species that cause harmful algal blooms (HABs). To address this problem, we used a water circulation culture system that provided in-water air bubbles to achieve active growth and mass cultivation of the dinoflagellate Alexandrium affine. This facilitated assessment in a large-scale mesocosm (1000 L) of the short-term response of the marine pelagic planktonic community to inoculation with A. affine under diatom-dominant conditions. Members of the pelagic planktonic community (bacteria and phytoplankton) varied in their response to A. affine addition, even over short time periods. Following nutrient depletion, the population of the dominant diatom (Chaetoceros debilis) rapidly declined, while the proportion of A. affine increased to more than 80% in both the low and high concentration treatment groups. The bacterial community was influenced by the population dynamics of phytoplankton, but a similar effect was not evident for the mesozooplankton community. Rhodobacteraceae dominated during the diatom-dominant stage in the mesocosms, and their numbers were positively correlated with most of the diatoms, including C. debilis. In contrast, the bacterial SAR11 clade and C. debilis showed markedly opposite patterns, and their occurrences were strongly negatively correlated. At the end of the experiment, there were similar time-series changes evident between the major bacterial group, and phytoplankton of the SAR11 clade and A. affine, but these groups were not directly correlated in association network analysis, indicating that the SAR11 clade was more associated with the decline in diatom populations rather than having a stimulatory effect on dinoflagellates. The results indicate that when a large population of A. affine is introduced into an environment dominated by diatoms, it predominately contributes to changing the phytoplankton community by maintaining its own population under low nutrient conditions, rather than affecting the entire planktonic community.

The studied transgressive deposits record the imprints of the coastal upwelling affecting the distribution of the shallow-water benthic assemblage in the early Priabonian Central Carpathian Paleogene Basin (CCPB). Our inferences are based on the study of benthic and planktonic assemblages, with special emphasis on the coralline algal (CRA) system, and the facies development at the Strba locality. We have observed the development of cool-water carbonates on warm-water carbonate platforms. Coralline algal assemblage predominated through hapalidialids, rhodalgal and bryomol grain associations; specific microborings and calcareous nannoplankton in the Strba locality are indicative of cool-water, while nummulite banks and hermatypic corals from adjacent and distant sites within the basin are indicative of warm-water carbonates. The last mentioned are indicative of oligotrophic and oligophotic settings, while nannoplankton, bryozoans and mollusks suggest mesotrophic conditions. Given the above, our results show the heterogeneous distribution of sea water temperature and nutrients that are characteristic for recent seasonal wind or eddy-driven coastal upwelling ecosystems (e.g. in the Mediterranean Sea). Upwelled cold and nutrient-enriched water enhanced the expansion of suspension feeders and favoured the growth of cool-water CRA with gametophytic phases. In the seasons without upwelling, nummulits could thrive in warm-water settings. This mechanism well explain why extensive nummulit banks were developed in adjacent sites but were not in the Strba locality. The section is topped by bryozoan marlstone with glaucony. This lithofacies indicates the deepening of the basin. Here we were not able to discriminate between agents causing nutrification (e.g. upwelling, river plumes or gradual cooling) and the associated mesotrophication of the environment during the climatic deterioration documented across the CCPB.

The interface between lotic and lentic ecosystems is often a zone of intense metabolic activity, as primary production in streams and rivers can be light limited whereas nutrients often limit primary production in lake ecosystems. Our objective was to model the influence that rivermouths (the lotic-lentic interface) could have on the loads of soluble reactive phosphorus (SRP) and dissolved inorganic nitrogen (N) passing from the tributary to the nearshore zone of a lake. To achieve this objective, we modeled the combined role of water column nutrient transformation rates with sediment nutrient flux rates. For sensitivity analysis, we picked plausible parameter ranges based on values previously measured in the Fox rivermouth (a tributary to Lake Michigan). Sensitivity analysis of the model demonstrated that overall the importance of water column processing rates increases with increasing nutrient concentration and discharge. We then applied the model to the Fox rivermouth, simulating the change in nutrients on four dates where all of the necessary parameters had been estimated. This modeling suggests that the Fox rivermouth is often a net sink for SRP and source for ammonia (NH4), with water column processing driving SRP removal and both water column and sediment flux driving NH4 dynamics. Removal of SRP in the water column means conversion to particulate and/or organic P, and those P pools are generally considered to be less bioavailable than SRP, so it may be that rivermouths disconnect upstream sources of nutrients from nearshore food webs. These results demonstrate that the interface zone between lotic and lentic systems has the potential to substantially alter the load and character of nutrients as river waters pass through rivermouths to adjacent nearshore areas.

The Western Antarctic Peninsula (WAP) is experiencing rapid climate warming, resulting in affecting the marine food web. To investigate the microzooplankton spatial distribution and to assess how climate change could affect the tintinnids community, sea water samples were collected during late summer 2018 at 19 stations in three different areas: Deception Island, Elephant Island and Antarctic Sound. The microzooplankton community comprised mainly tintinnids, aloricate ciliates, heterotrophic dinoflagellates and micrometazoans. Microzooplankton abundance varied between 3 and 109 ind. L−1 and biomass ranged from 0.009 to 2.55 µg C L−1. Significant differences in terms of abundance and taxonomic composition of microzooplankton were found among the three sampling areas. Deception Island area showed 44% of tintinnids and the rest were heterotrophic dinoflagellate, aloricate ciliates and micrometazoans. In Elephant Island and Antarctic Sound areas, tintinnids reached, respectively, 73% and 83% of the microzooplankton composition, with all the other groups varying between 20 and 30%. Tintinnids were the most representative group in the area, with the species Codonellopsis balechi, Codonellopsis glacialis, Cymatocylis convallaria and Cymatocylis drygalskii. The highest amounts of tintinnids were found at the surface and 100 m depth. The above mentioned species may be considered key species for the WAP and therefore they can be used to track environmental and hydrographical changes in the area. In late summer, microzooplankton presented low abundances and biomass, nevertheless they represented an important fraction of the planktonic community in the area.

In this study, bacteria from a microbial fuel cell (MFC) and isolates were evaluated on their Fe

The upper reaches of the Han River are the source region of water for the Middle Route of China’s South-to-North Water Diversion Project, mainly for household, industrial, and irrigation purposes. Planktonic bacteria are more sensitive than macroorganisms to water physical and chemical properties and play a critical role in biogeochemical processes in river ecosystems. In November 2017 and April 2018, a systematic and methodical survey was carried out to evaluate the water quality and bacterial communities, on the mainstem of the Han River and its five main tributaries. In this study, high-throughput sequencing technology has been employed to investigate the bacterioplankton community composition. The results indicated that: 1) Diversity increased downstream, especially in the upper reaches of the Han River. 2) The relative abundance of Actinobacteria increased with the increase of river length, while that of Bacteroidetes decreased slightly. 3) Five tributaries were found to be importance sources of taxa to the Han River, however in both months a large proportion of OTUs (37.84% and 36.34%, respectively) had unknown sources. 4) Finally, redundancy analysis (RDA) and Bioenv analysis showed that environmental parameters (pH, TN, Cond, NH4+-N, DO, NO2−-N, Chl-a and T) had a great influence (p ≤ 0.05) on the bacterioplankton community. These research results are beneficial for the managing the ecological system, protecting the tributary biodiversity, and conserving the mainstem and tributaries of the Han River basin.

Pico- and nano-eukaryotic plankton are important members of marine ecosystems. To understand their community structure and spatio-temporal variations in the Beibu Gulf, and to study the impact of Changjiang Nuclear Power Plant (CNPP) located in the northwest coast of the Hainan Island on the eukaryotic plankton, we studied these issues in the coastal water near CNPP bimonthly from February 2018 to January 2019 via 18S Illumina sequencing. The results reveal a higher genetic alpha-diversity and less beta-diversity of the plankton community in small-size (0.45–5 µm and 5–20 µm) fractions than in large-size (20–200 µm and >20 µm) fractions. The small-sized phytoplankton, including Micromonas (Chlorophyta) and Minutocellus (Bacillariophyta), as well as heterotrophic plankton, including Paraphysomonas (Chrysophyceae), Ellobiopsis (Dinoflagellates), and Syndiniales (Dinoflagellates), took up a considerable proportion in eukaryotic plankton community. In addition, it showed a slight temperature increase and no significant difference in eukaryotic plankton community between the outfall of CNPP and other sampling sites, suggesting that the impact of the thermal discharge from the CNPP on local eukaryotic plankton community was limited.

Objective The aim of this study was to evaluate the effect of nystatin on the efficacy of chlorhexidine against Streptococcus mutans in planktonic cells and mixed biofilm with Candida albicans. Material and methods S. mutans ATCC 25,175 in suspension and also combined with C. albicans ATCC 18,804 in biofilm were cultured. Minimum inhibitory concentration (MIC), crystal violet colorimetric assay, and colony-forming unit counting (CFUs/mL) were performed. Results An increased MIC of chlorhexidine against S. mutans was observed when the drugs were administered mixed in a single formulation and with time intervals in between, except for the 30-min interval. The biofilm optical density (OD) in treatments using chlorhexidine and nystatin combined did not significantly differ from chlorhexidine alone. Either in biofilm colorimetric assay or determination of CFUs, the combined treatments with nystatin administered before chlorhexidine had less effect on chlorhexidine efficacy. Conclusions Nystatin interferes with the action of chlorhexidine against S. mutans. The antimicrobial effectiveness of the combined drugs depends on their concentration, time interval used, and the planktonic or biofilm behavior of the microorganisms. Clinical relevance In view of the great number of patients that can receive a prescription of chlorhexidine and nystatin concomitantly, this study contributes to the knowledge about the effect of the combined drugs. Given the high prevalence of prescriptions of chlorhexidine and nystatin in dentistry, dental professionals should be aware of their possible antagonistic effect.

An experiment was conducted to study the influence of environmental parameters and stocking density on growth, survival, feed utilization, and economic feasibility of a high value butter catfish, Ompok bimaculatus in floating cages in a large tropical reservoir of India for 180 days. The fingerlings (11.44 ± 1.33 cm; 8.05 ± 3.27 g) were stocked at three stocking densities, viz., 15, 25 and 35 fingerlings m-3 in GI cages (32m3) in triplicates. Commercial floating pellets were fed to fish at 5–3% of fish biomass. The results indicated that the fishes at the lowest stocking density of 15 fingerlings m-3 had significantly higher (p 0.05) between stocking densities of 15 fingerlings m-3 and 25 fingerlings m-3. The condition factor was insignificantly higher at lower densities and its values close to 1 indicated congeniality of reservoir ecosystem for cage culture of the species. The coefficient of variation of weight was significantly higher (24.19 ± 1.20) at 35 fingerlings m-3. The highest economic gains in terms of benefit cost ratio (1.77) were achieved at the lowest stocking density. The present study indicated better growth and economic returns at lower stocking densities of 15–25 fingerlings m-3. The nutrient load and plankton abundance were higher at culture site, however, did not vary significantly from reference sites throughout the culture period. Although most of the environmental parameters showed significant seasonal variations, dissolved oxygen showed significant positive relation (r = 0.86) with the growth of the fish. This is the first study reporting feasibility of cage culture of this highly renumerative species in open waters. The cage culture of this species will not only ensure better economic returns to the marginal cage farmers but will aid in the conservation of this species in natural ecosystem. Being a low volume high value species, the impact on environment will be less compared with high volume low value species. This study will serve as baseline for standardization of its grow-out protocol in cages and will be a step towards much needed species diversification for sustainable small scale cage farming in tropical reservoirs of Asia.

Compared with deep oligotrophic waters, the distribution and geochemical processes of polycyclic aromatic hydrocarbons (PAHs) in shallow eutrophic waters are more complicated. The fourth largest freshwater lake in China (Lake Hongze) was taken as an example to study distribution, sources, bioaccumulation, and air–water exchange of PAHs in shallow eutrophic waters. Eighty samples of surface sediments, air, water, and plankton were collected simultaneously from 15 sampling sites in November 2018. PAHs were extracted, concentrated, and analyzed using GC–MS. Average concentrations of ∑PAH16 in the surface sediments, atmosphere, water, phytoplankton, zooplankton, and suspended particle matter were 511 ± 212 ng g−1, 119 ng m−3, 232 ± 91.2 ng L−1, 12,500 ± 70,000 ng g−1, 102,000 ± 83,600 ng g−1, and 35,100 ± 24,700 ng g−1. Log BCF of PAHs in phytoplankton ranged from 6.7 ± 7.8 to 16.0 ± 4.4. Log BAF of PAHs in zooplankton ranged from 8.2 ± 8.1 to 16.8 ± 3.9. Log BMF of PAHs from phytoplankton to zooplankton varied from − 0.25 ± 0.39 to 0.25 ± 0.55. Combustion of petroleum and coal was the main source for the PAHs in the surface sediments of Lake Hongze. Concentrations of PAHs in phytoplankton and zooplankton were negatively correlated to the trophic level index. Bioaccumulation of PAHs by plankton was observed. No biomagnification occurred from phytoplankton to zooplankton for most PAHs during this sampling period. The net air–water flux of low molecular weight PAHs was from water to air. The net air–water flux of high molecular weight PAHs was from air to water.

Elucidating the mechanisms of fluctuations in fish populations are key to sustainable fisheries management. However, limited data combined with climate variability and fishing further constrain our understanding of fish population dynamics. Fortunately, marine sedimentary archives of fish abundance and environmental changes in the past, may provide new insights into long-term fish population fluctuations. Here, we used 150-year sediment records of the abundance of Japanese anchovy (Engraulis japonicus) scales, phytoplankton, and zooplankton biomarkers, and δ15N data previously reported from the central Yellow Sea (YS). We discussed the linkages of the anchovy abundance to ecosystem structure and sea surface temperatures (SSTs). Principal component analysis (PCA) identified negative effects of strong stratification (higher δ15N) and high abundance of haptophytes (higher alkenone content) on the anchovy stock through our analytical period (~1860–2005 AD). In addition, we found positive relationships between the anchovy abundance and plankton productivity in proxies before the period of intense fishing (1860–1980 AD), indicating bottom-up processes affecting the anchovy stock. However, the bottom-up processes became unclear under excessive fishing. This was possibly due to overfishing becoming a major driver after 1980, thereby altering the cascading of the marine ecosystem towards a different structure. Climate variability seems to indirectly influence the anchovy stock through bottom-up control via a cascading effect from the changes in the North Pacific Gyre Oscillation (NPGO) or the Pacific North American pattern (PNAP). The impacts of these changes on the hydrodynamic features of YS in turn influence the productivity of plankton prey for the anchovy. Collectively, our findings suggest that synergistic effects of climate and fishing on the anchovy need to be paid greater attention. Our results also contribute to an improved understanding of fish population fluctuations in other seas.

The benthic and planktonic foraminiferal assemblages of the Upper Eocene Beni Suef and Maadi formations of three exposed sections at northeastern part of the Nile Valley of Egypt were studied in detail to detect the paleoenvironment and the biostratigraphy. One hundred and fifty-four species of benthic foraminifera belonging to 63 genera and 40 families were identified. Thirty-six planktonic species belonging to 13 genera and 5 families were also identified. The vertical distribution of the recorded foraminifera species in the studied Eocene succession leads to construct six benthic and two planktonic foraminifera zones in the Upper Eocene succession. The benthic zones were arranged from base to top as follows: Bulimina jacksonensis zone, Cancris auriculus var. primitivus zone, Neoeponides schreibersi zone, Elphidium ancestrum zone, Cibicidina carinatus zone, Anomalinoides trinitatensis–Textularia fahmyi zone. Moreover, the planktonic foraminifera zones include the E14.Globigerinatheka semiinvoluta zone and E15.Globigerinatheka index zone. These zones were discussed and correlated with those in Egypt and the neighboring Middle East countries. The faunal content and the facies are used to determine the environmental conditions that controlled the deposition in the Upper Eocene platform of the studied area. Accordingly, the Beni Suef Formation was deposited in an open marine, middle to outer neritic environment, while the Maadi Formation was deposited in shallower environment. Based on the microfacies analysis, three main facies types are determined including inner, mid and outer ramp facies.

Zooplankton is an important community in aquatic ecosystems due to its linkage between primary producers and secondary consumers, and by their key role in cycling organic materials. However, a low number of studies were performed in small lotic systems, mainly in savanna Cerrado headwater systems. Therefore, our objective was to investigate α and β diversities of the zooplankton community along 21 headwater streams in relation to micro-basin and sub-basin spatial scales and the water physicochemical parameters. Our hypotheses are that α diversity is negatively related to the increase on spatial scale and β diversity is positively related to the increase on scale. Zooplankton samples were taken using a bucket and filtered 200 L by a 64 µm mesh plankton net and preserved for subsequent identification. Water temperature, dissolved oxygen, pH, electrical conductivity, ions, and anions (nutrients) were measured. A total of 2650 individuals (m−3) from 19 taxa were collected. The most abundant taxa were Cyclopoida (copepodite; 24.4%) and rotifer Tricocerca cylindrica (17.7%). The lower spatial scale was the most important factor driving the α diversity. However, the richness of the zooplankton community did not change among sub-basins and micro-basins. Changes on species composition by nested spatial organization between habitat patches drove the β diversity. The communities from the same sub-basin and micro-basin were more structurally related than those from different basins. Finally, closer points show similar environmental characteristics and electrical conductivity concentration increases the species richness. Therefore, patterns of species diversity are essential to understand community ecology, as well as to provide information for conservation planning on savanna Cerrado streams.

Invasive alien species often affect native ecosystems worldwide. In Japan, the channel catfish Ictalurus punctatus is an invasive species in rivers. However, information regarding its feeding habits in rivers around dam reservoirs is still scarce. Thus, in this study, we assessed the feeding habits of I. punctatus collected from the Nunome River, a secondary tributary of the Yodo River, downstream of the Nunome Dam reservoir. Standard length and weight of the collected individuals were measured, and their stomach contents were analyzed under a stereomicroscope to identify prey species. Moreover, stable isotope analysis was conducted to determine their trophic niche. Overall, I. punctatus was shown to feed on a variety of food resources derived from the riparian forest and river ecosystem; in particular, algae represented 78.8% of its stomach contents. However, stable isotope analysis suggested that I. punctatus depended on benthic insects and fish to ensure adequate body composition, whereas algae were not assimilated by I. punctatus. Among benthic insects, I. punctatus relied on trichopteran larvae such as Macrostemum radiatum, which appears downstream of the dam reservoir and utilizes plankton algae from the dam. In conclusion, these findings provide additional clues for a better understanding of I. punctatus feeding activity and its relationship with its surrounding ecosystem.

The Laptev Sea and the East Siberian Sea are remote areas of the Arctic region where detailed data on phytoplankton composition and spatial distribution remain limited. In the context of the ongoing environmental changes (increasing warming and ice melting) and prospective exploration activities (oil and gas production) on the Arctic shelves, understanding of the seasonal and interannual phytoplankton community dynamics is of critical importance. Our study provides new specifying data on species composition of phytoplankton over the vast area of the Laptev Sea shelf and the East Siberian Sea shelf. We found that the outer shelf of the Laptev and East Siberian seas was characterized by typical late spring diatom species (Chaetoceros furcellatus, Chaetoceros diadema, Chaetoceros debilis, Chaetoceros constrictus). On the inner shelf of the Laptev Sea, which is strongly affected by the Lena River water masses, the phytoplankton were characterized by the transition from the summer to an autumn stage of development. Local algal assemblages were composed by mixo- and heterotrophic dinoflagellates (Dinophysis and Protoperidinium genera) together with marine and brackish water-marine diatoms (Thalassiosira hyperborea, Thalassiosira baltica, Thalassiosira gravida, Thalassiosira nordenskioeldii) accompanied by sporadically occurring freshwater riverine planktonic diatom species (Aulacoseira granulata, Aulacoseira italica, Asterionella formosa). These variations in species composition over the Laptev Sea shelf were attributed to differences in the hydrography, marine chemical conditions, and the sea-ice regime.

Caranx caninus, C. sexfasciatus, Chloroscombrus orqueta, Selene brevoortii, S. peruviana, and Selar crumenophthalmus are species with economic importance for local artisanal fisheries and are regular components of the fish assemblage at Barra de Navidad coastal lagoon in the Pacific coast of Mexico. The working hypothesis was that carangid species in the lagoon share a common food base but the proportion of main food categories in the diet will be different for some groups of species due to differences in key morphological characteristics of the carangids. A total of 1251 individuals were used for diet analyses. Stomach content analyses showed that five species feed on benthic invertebrates and small fish while one species was mostly a plankton feeder. A partial sharing of main food resources was found for most of the studied species, but significant differences in the proportion of food categories in the diet were identified for several groups of species. Another aspect of diet variation was associated with predator size whereby larger individuals tended to consume the largest prey. A plausible explanation for the variation observed in feeding habits is based on morphological differences among groups of species which favor piscivory or planktivory in some cases. This paper is the first published report on the feeding habits of all six species in any Mexican estuarine habitat and of four species in Eastern Pacific estuarine waters.

The sea potato Acaudina spp. is a species of sea cucumber, belonging to the class Holothuroidea under Phylum Echinodermata. It becomes blooming recently in the East Sea of China, causing serious ecological problems. However, until now there are no molecular data for its larval identification and population genetic analysis. In this study, we firstly screened a mtDNA fragment and demonstrated that it was the species-specific molecular marker for the identification of Acaudina spp. We then developed a quantitative polymerase chain reaction (PCR) method to evaluate the larval density of Acaudina spp. based on this molecular probe. Utilizing this method, we examined 116 plankton samples collected in four seasons from 13 stations along the coastal region in Fujian province, China. The results showed that the high larval density was presented at stations 1, 2, and 3, which were near a quay in the coast. The larval density increased from April and reached the highest value in June and July, suggesting temperature might be the main environmental factor on the effects of its population distribution and density. Our work provides an important molecular tool for species identification and risk evaluation of a potentially invasive species.

Many benthic animals begin life with a planktonic larval stage during which coastal currents may move individuals far from shore. This trait is believed to allow individuals to develop away from nearshore predators and sibling competition, based on the assumption that mortality rates are weaker offshore. However, larvae developing offshore often fail to locate suitable coastal habitats. This results in a trade-off between nearshore mortality and offshore wastage with consequences for larval delivery to adult habitats that have not been fully appreciated. We use a reaction-diffusion model to show that when the nearshore larval mortality rate is high, larval supply can vary more than 10-fold with the offshore mortality rate. If this offshore rate is weak, then larval supply is maximized by an intermediate diffusion rate or larval duration. While a low-diffusivity coastal boundary layer typically improves the larval supply by decreasing wastage, it can also reduce the larval supply by preventing individuals from exploiting low offshore mortality rates. Finally, the cross-shore structure of the mortality rate may influence the alongshore transport of larvae by determining how far offshore they reside prior to settling, and, consequently, the alongshore currents they experience. Our observations contrast with the prior argument that larval supply decreases with diffusivity and larval duration due to wastage, and challenge the widespread decision to omit cross-shore heterogeneity from studies of alongshore movement. Scenarios in which spatial variability in the mortality rate has a large effect on recruitment are important both for understanding the biological consequences of the larval stage and from a modeling perspective.

In recent years, marine hypoxia has frequently occurred in global coastal and estuarine waters with detrimental impacts on marine fauna. In this work, we examined the impact of hypoxia on the mortality, growth, reproduction, and enzyme activities of the mysid Neomysis awatschensis. The mortality rate of adult mysids increased by 100% within 4 h under the hypoxia treatment (2 mg/L), while that of juveniles was 53.33 ± 5.77% after 96 h. The long-term low dissolved oxygen (DO) treatment (5 mg/L for 30 d) significantly reduced the fatty acid content of mysids. A significant reproductive inhibition was also observed: the total juvenile productions in the treatment with DO at 4, 5, and 6 mg/L were only 6.5%, 24%, and 60% of the control group (DO at 8.5 mg/L), respectively. The total superoxide dismutase activity increased significantly in low oxygen treatments. Catalase and lactate dehydrogenase activities first increased and then decreased with the dropping DO concentrations. These results suggest that hypoxia has multiple impacts on marine zooplankton. This may adversely affect higher trophic level organisms and the structure and function of marine ecosystems.

We combined a high-resolution acoustic telemetry array with presence/absence receivers to conduct a preliminary study of the seasonal movements, activity patterns, and habitat associations of the newly described Deacon Rockfish (Sebastes diaconus). Eleven mature female Deacon Rockfish were tagged and monitored during an 11-month period, at a nearshore rocky reef off Seal Rock, Oregon, USA, an area of recurring seasonal hypoxia (defined as dissolved oxygen concentration [DO] −1). Two tags were detected leaving the study area by day 35, indicating predation or emigration. Three tags became inactive within the array, indicating tag loss or fish death. Six “resident” fish inhabited the array for 246–326 days. Resident fish exhibited high site fidelity, small home ranges (mean 95% KDE = 4907 m2), and consistent activity patterns for the duration of the summertime high-resolution array (5 months), except during seasonal hypoxia. Resident fish were strongly diurnal in summer, with high levels of daytime activity above the bottom in relatively rugose habitat, followed by nighttime rest periods in deeper, less rugose habitat. During summertime hypoxia, resident fish exhibited less daytime activity during daytime hours with no rest periods at night, inhabited shallower water depths, and moved well away from their core activity areas on long, erratic forays. During the winter, diel patterns were less evident with higher activity levels at night (than in the summer) and lower activity levels in the day (than in the summer). We propose that some Deacon Rockfish continuously inhabit nearshore reefs throughout the year, but that daily/seasonal movement patterns, seasonally occurring hypoxia, and prey preferences for planktonic organisms influence relocation.

Many studies using surface plankton data from the Continuous Plankton Recorder (CPR) have suggested that micro- and meso-sized zooplankton species/taxa can serve as indicators of environmental change. But while regular CPR sampling would allow for the detection of changes in zooplankton communities, few intra-annual CPR surveys have been undertaken along single transects. We report the temporal variability of zooplankton community structure using CPR data collected along the Japanese monitoring transect (110° E) in December 2014, January 2015, and March 2015. We found zooplankton abundances in both the Polar Frontal Zone (PFZ) and Antarctic Zone (AZ) to increase from December to January, and mean AZ abundance to peak abruptly in January (381.9 ind. m−3) before decreasing to about 25% of that value in March. We attribute changes in total zooplankton abundance to fluctuations in the numbers of the two small dominant copepods, Oithona similis and Ctenocalanus citer. High AZ phytoplankton concentrations in December likely increased surface food availability, influencing population growth, and/or the timing of copepod seasonal ascension. We recommend future CPR surveys include sampling with finer mesh for more accurate determination of abundances of small-sized zooplankton, to better understand the ramifications of climate change on Southern Ocean trophic structure.

Trace element supplementation to the freshwater environment can influence the plankton density and species diversity, contributing to the nutrition of aquaculture species, especially during the juvenile stage. An experiment was conducted under laboratory conditions to evaluate the effects of supplementing different mixtures of manganese, silica and phosphorus on the plankton density and species diversity and their impact on cultured juvenile marron (Cherax cainii, Austin and Ryan, 2002). Manganese, silica and phosphorus in concentrations of 0.0024, 0.41, 0.05 mg*L-1; 0.0041, 0.82, 0.12 mg*L-1; and 0.0058, 1.26, 0.25 mg*L-1 respectively termed as low, medium and high were supplemented to tank water containing a phytoplankton density of 3.77 ± 0.16 × 106 cells*L-1 and 292.9 ± 17.6 individuals*L-1 of zooplankton, and plankton growth was observed every 24 h for 6 days. Afterwards, a 3-month trial was conducted studying the effects of these trace element concentrations and resulting plankton densities on marron growth, survival, moulting, gut microbiota and health indices. Silica supplementation at high concentration increased the diatom abundance, silica and phosphorus supplementation at higher concentration that resulted in a significant increase in plankton density and species diversity, leading to improved marron health indices than the control and the tanks receiving a low concentration. Marron-specific growth rate, weight gain and dissolved copper concentration in haemolymph were significantly higher in tanks with higher supplementation and higher plankton density. Marron survival, moult interval and total haemocyte count were not affected by the supplementation. Marron gut microbiota at higher trace element concentration supplementation showed a significant increase in abundance of phosphate solubilizing bacteria.

Studies that associate environmental parameters with aquatic organisms in man-made lakes remain limited by accessibility and interest particularly in many Asian countries. With missed opportunities to monitor environmental transitions at Lake Kenyir, our knowledge of lake transition is restricted to the non-mixing shallow waters only. Triplicate monthly benthic invertebrate samples were collected concurrently with various environmental parameters at three locations (zones A-C) of Kenyir Lake, Malaysia. Our results affirmed that the northeast part of Lake Kenyir is oligotrophic. Abundance of phytoplankton, total suspended solids, phosphate, nitrite and nitrate drive the abundance of various groups of benthic invertebrates. All of these extrinsic variables (except phosphate) negatively influenced the density of Trichoptera and positively influenced (P

Microplastic pollution has become a global concern due to its distribution, high abundance, and negative impacts on aquatic ecosystems. These particles enter aquatic systems through the inadequate management of solid waste and wastewater generated from socioeconomic and domestic activities. In Colombia, about 65% of the solid waste generated in coastal populations is improperly managed and discharged into natural water bodies, contributing to microplastic pollution. The present study aimed to determine the abundances, distribution, and physical and chemical characteristics of microplastics in coastal surface waters of the Colombian Caribbean and Pacific. Samplings were carried out at 41 stations distributed across nine study areas during the rainy season of 2017, using a 500-μm mesh plankton net. The microplastic abundances ranged from 0.01 to 8.96 items m-3, with the coastal waters of the Caribbean areas being the most polluted. Microplastics with shapes of fragments, filaments, and foams, composed of polyethylene, polypropylene, and polystyrene, were the most common. A baseline of microplastic pollution in Colombian coastal water was generated, which will serve to evaluate the effectiveness of the environmental measures implemented to significantly reduce this pollution type, within the sustainable development goals.

Thirteen mountain lakes, originally fishless, at 1325 and 2150 m a.s.l., with the maximum depths ranging from two to 15 m, and areas of 0.3 to 4.5 ha, were monitored between 1991 and 2012 in the Triglav National Park (Slovenia, Central Europe). The lakes are located on limestone bedrock, with no surface inflow or outflow. They range from ultra-oligotrophic to hypertrophic. They were stocked with fish between late 1920s and 1996. The zooplankton samples were collected as composites from the bottom to the surface at the deepest point of the lake, for both qualitative and quantitative analyses. In situ physical parameters in the water column were measured, and the samples for chemical analyses were collected in parallel with the zooplankton sampling. Thirty-two species, including Copepoda, Cladocera, Rotifera and Ciliata, were recorded. They belonged to three ecological groups: (1) constitutive, (2) scout and (3) benthic species. In some of the lakes, the species composition remained stable over the study period, but in lakes stocked with fish, significant changes occurred, in both species composition and biomass. Large-bodied species of Copepoda and Cladocera were eliminated by fish allowing small-bodied planktonic species of Copepoda, Cladocera and Rotifera to dominate the community, along with benthic species, associated with algal mats. The lake, stocked with fish in the 1920s, was hit by two strong consecutive earthquakes, in 1998 and 2004, after which a significant change in species composition and biomass was recorded.

Comparison of activity of antibiotics against Staphylococcus aureus strains in their plankton form and in biofilms of varying maturity showed that the concentrations of antibiotics causing death of 90% S. aureus strains (MIC90) in their plankton form was 0.07-2.80 μg/ml and significantly (p

Planktonic ciliates are major components of pelagic food webs in both marine and freshwaters. Their population dynamics are controlled ‘bottom-up’ by prey availability and ‘top-down’ by microcrustacean predators. In oceans, copepods are the main ciliate predators while in lakes cladocerans are the typical predators. The efficacy by which these functionally different predators control ciliate population dynamics is debated. We, therefore, investigated experimentally the grazing of three microcrustacean predators with different feeding modes on five freshwater ciliates. We then performed a meta-analysis to assess if our findings can be generalised for aquatic ecosystems. We hypothesized that top-down control is stronger in lakes than in the ocean. We find that: (i) average ingestion rates of marine and freshwater microcrustaceans do not differ; (ii) clearance rates of freshwater cladocerans decrease with ciliate size but increase with ciliate size in freshwater copepods; (iii) clearance rates of the marine microcrustaceans is unrelated to ciliate cell size. These findings have implications for the functioning of freshwater and marine food webs: (i) the ciliate—microcrustacean link is stronger in lakes than in the ocean, and (ii) globally top-down control of ciliates is unlikely in the ocean.

Fluorescence is highly prevalent in reef-building corals, nevertheless its biological role is still under ongoing debate. This feature of corals was previously suggested to primarily screen harmful radiation or facilitate coral photosynthesis. In mesophotic coral ecosystems (MCEs; 30-150 m depth) corals experience a limited, blue-shifted light environment. Consequently, in contrast to their shallow conspecifics, they might not be able to rely on photosynthates from their photosymbionts as their main energy source. Here, we experimentally test an alternative hypothesis for coral fluorescence: a prey-lure mechanism for plankton. We show that plankton exhibit preferential swimming towards green fluorescent cues and that compared to other morphs, higher predation rates are recorded in a green fluorescing morph of the mesophotic coral Euphyllia paradivisa. The evidence provided here - that plankton are actively attracted to fluorescent signals - indicates the significant role of fluorescence in amplifying the nutritional sink adjacent to coral reefs.