Search Results (241)

This study covers a large area around the Kuril Islands, one of the longest island arcs in the world, crossing several climatic zones, which allows for observations of longitudinal shifts in planktonic species’ ranges following shifts in the boundaries between the climatic zones. We analyzed spatial and vertical changes in the zooplankton community structure and the associated environmental factors from Yuri Island to Onekotan Island both in Pacific and Sea of Okhotsk waters, which are influenced by cold and warm water masses. Species diversity in the Pacific waters was higher than in the Sea of Okhotsk waters, with a peak of diversity recorded from warm waters off the southern Kuril Islands associated with the Soya Current and the Kuroshio Extension. Zooplankton abundance and biomass above the thermocline were higher in the Pacific waters compared to the Sea of Okhotsk area, showing a tendency to increase with higher latitude and lower water temperatures and generally to decline with depth. The water temperature and salinity below the thermocline were the most important explanatory environmental variables responsible for zooplankton abundance variations. The distribution patterns of the large-sized copepods were strongly correlated with temperature and salinity, as well as with dissolved oxygen and chlorophyll a levels. In contrast, small-sized copepods were adapted to or thrived in the areas with elevated temperature and salinity values and a reduced chlorophyll a concentration. Full article

The emergence of antimicrobial resistance and the increasing demand for a healthier lifestyle have set new goals for science and industry. In the search for new, more effective, and environmentally friendly antimicrobial agents, special attention is being paid to natural resources. In this regard, essential oils derived from plants, which are widely used in the cosmetic, food, and pharmaceutical industries, are one of the solutions. In view of the above, this study aims to investigate the biological effects of Abies alba essential oil (AAEO). The chemical profile of AAEO was evaluated by GC/MS analysis, which revealed a high abundance of limonene (52.2%) and α-pinene (36.2%). Antioxidant activity evaluation showed a higher potential of AAEO in scavenging ABTS radical species with an IC₅₀ value of 1.18 ± 0.05 mg/mL. In vitro antimicrobial activity was determined by disc diffusion and minimum inhibitory concentration assays and showed that AAEO was more efficient in inhibiting the growth of G⁺ bacterial species. On contrary, in situ evaluations of antimicrobial effects of AAEO on different food models (strawberry, kiwi, white radish, and beetroot) resulted in more efficient suppression of G⁻ bacterial species. Although AAEO showed low effects on yeasts determined by in vitro methods, in situ investigations showed its higher potential in eradication of Candida yeast. The antibiofilm properties of the AAEO matrix were determined by means of crystal violet assay and MALDI-TOF MS Biotyper analysis against biofilm-forming Salmonella enterica. The analysis performed led to the conclusion that AAEO, when applied prior to biofilm formation, may contribute to the removal of planktonic cells and alter the abiotic surface, thereby reducing the suitability of Salmonella enterica for microbial attachment. Full article

This study compiles and updates data to construct the phosphorus budget of the Archipelago Sea (northern Baltic Sea, Europe), with a particular focus on estimating phosphorus pools associated with fish populations. Biomass data and species-specific phosphorus content were utilized, and a bioenergetic modeling approach was applied to Baltic herring (Clupea harengus membras) and European perch (Perca fluviatilis) to estimate species-specific food consumption and nutrient excretion. Between 2001 and 2024, average total phosphorus concentrations were 28% higher than during the baseline period of 1983–1989. From 1998 to 2023, the annual average fish catch in the Archipelago Sea was 15,516.5 tons (16.3 kg/ha), with 73.1% consisting of commercially harvested herring. Other abundant catch species included, for example, pikeperch (Sander lucioperca), northern pike (Esox lucius), and European smelt (Osmerus eperlanus). On average, the annual catch contained 83.4 tons of phosphorus. Fishing may have annually removed an amount of phosphorus equivalent to approximately 0.6% of the total phosphorus pool in the water column and surface sediment, or 1.4% of the estimated total phosphorus load to the Archipelago Sea. The contribution of fish to phosphorus turnover is minor, as nutrient recycling is dominated by plankton. Planktivorous fish and their prey recycle nutrients already present in the water column and are therefore not the primary drivers of eutrophication. Full article

Abundant large organic aggregates, which form mucous webs up to a few decimeters in length, have been observed in Baía de Todos os Santos (BTS), northeastern Brazil. This communication presents preliminary results from field (February 2015) and laboratory (June 2015) experiments that aimed to determine preliminary values for respiration and near-maximum photosynthesis and the impact of macroaggregates on respiration rates. The experiments included the determination of respiration in controls, with the mechanical removal and addition of macroaggregates. The field experiment during a flood tide presented the lowest respiration rate (−7.0 ± 0.7 µM L⁻¹ d⁻¹), average net primary production (8.9 ± 4.5 µM L⁻¹ d⁻¹), and gross primary production (16.0 ± 10 µM L⁻¹ d⁻¹), with a ratio of gross primary production to respiration of 2.3. The control experiments during an ebb tide showed a mean respiration rate of 8.7 ± 2.3 µM L⁻¹ d⁻¹, whereas, after macroaggregate removal, this was 9.5 ± 4.5 µM L⁻¹ d⁻¹. In the laboratory experiments, the control sample respiration rate of 18.4 ± 1.4 µM L⁻¹ d⁻¹ was slightly increased to 20.6 ± 0.1 µM L⁻¹ d⁻¹ after aggregate removal. The addition of aggregates to the control sample increased the respiration rate by approximately 3-fold, to 56.5 ± 4.8 µM L⁻¹ d⁻¹. These results indicate that macroaggregates could have an important role in pelagic and benthic respiration, as well as in the whole bay’s metabolism. Full article

Mangrove forests are vital ecosystems along tropical coasts, playing crucial roles in water purification and biodiversity conservation. Diatoms, as sensitive ecological indicators, were employed in this study to evaluate the health of the mangrove forests along the Sanya River. The research involved analyzing the community structure of planktonic diatoms and water physicochemical properties during spring and winter, as well as carrying out a comprehensive assessment of the ecological health of the region in terms of four seasonal–spatial–environmental–biological indices. A total of 22 genera of planktonic diatoms were identified. In winter, Melosira sp. (34.94%), Skeletonema sp. (25.50%), and Chaetoceros sp. (15%) were dominant, with relative abundances of 34.94%, 25.50%, and 15.00%. In spring, Melosira sp. became the absolutely dominant species, averaging 70.16%. Diatom cell abundance shows both significant seasonal and spatial variation. In winter, it ranged from 0.53 to 17.4 × 10⁹ cells-L⁻¹, peaking in the midstream region, whereas in spring, it ranged from 2.48 to 21.0 × 10⁹ cells-L⁻¹, peaking at the mouth of the estuary. A higher abundance of diatoms in spring strengthens primary productivity and supports the subsequent functioning of the food chain. Diatom indices (Shannon–Wiener index H’, Pielou evenness index J, and Margalef richness index D) indicated an intermediate ecological health level for the Sanya River mangrove forests. Diversity was higher in winter than in spring, with the lowest values recorded in the midstream region. Redundancy analysis (RDA) indicated that T, pH, and PO₄³⁻ were the primary environmental drivers of diatom community succession. In spring, pH was positively correlated with T and PO₄³⁻, respectively. They drove the succession of diatom communities from diverse assemblages in winter to a single dominant species. Full article

Integrated facies and micropaleontological analyses of the late Piacenzian to early Gelasian, middle shelf to lower shoreface succession of the Strongoli area, southern Italy, reveal a hierarchy of transgressive–regressive sequences. In particular, higher rank sequences up to ca. 40 m thick, composed of transgressive systems tract, highstand systems tracts and falling stage plus lowstand systems tracts, are composed of 10–11 lower rank sequences 2.5–4 m thick. Some micropaleontological parameters were defined: distal/proximal (D/P; ratio between distal and proximal benthic foraminifera); fragmentation (Fr; percentage of fragmentation of benthic foraminifera); P/B (ratio between planktonic and benthic foraminifera); abundance (total count of individuals); diversity (sum of the recognized species). Among these parameters, the D/P and Fr are suitable, if used in conjunction, to recognize uncertainty intervals containing the maximum flooding surface (between the D/P maxima and Fr minima) and the maximum regressive surface (between D/P minima and Fr maxima). Moreover, combining these parameters with the sedimentological evidence, it is possible to recognize transgressive and regressive trends of different hierarchical ranks. The present results are an example illustrating how an integration of different types of data allows the recognition of high-frequency sequences in shelf settings associated with minor shoreline shifts, which would otherwise have been unrecognized on the basis of only one kind of data. The present integrated approach, therefore, provides a way to improve the resolution of sequence stratigraphic analyses. Full article

Olyokma Nature Reserve, where we conducted our research, is in Eastern Siberia in the middle taiga zone in an area characterized by continuous permafrost. This is the only protected area in the region with a complete reserve regime, where there is no human activity. Here, we studied 14 different types of water bodies located along the Olyokma River valley, 13 of which were studied for the first time. For some of the studied water bodies, a high content of biogenic elements was noted, which may be associated with the characteristics of permafrost water bodies, which are under nutrient release from permafrost thaw. The concentration of several biogenic elements, including ammonium, nitrates and phosphates, increases in the water of the lakes toward the bottom of the river valley. In the composition of various communities of these water bodies, including both planktonic and non-planktonic, we identified 246 species and varieties of microalgae. The abundance and biomass of phytoplankton, as well as the number of species, decreased down the river valley. At the same time, at the upper stations there were more diatoms; while at the stations down the valley, green algae came to the fore; and even lower down, cyanobacteria prevailed. At the lower stations, the indicators of microalgae development were minimal. In accordance with the bioindicative properties of microalgae, a decrease in the trophic status of water bodies was noted down the river valley, which, in our opinion, is a characteristic feature of the waters of an undisturbed catchment basin in the permafrost area. This indicates that the studied aquatic ecosystem changes within a set of environmental and biological indicators, that is, it exists in natural conditions for this catchment basin. Research on the territory of Olyokma Nature Reserve allowed us to obtain information on natural transformation and removal of nutrients in permafrost catchments, while excluding the likelihood of anthropogenic impact on these processes. Full article

This study investigates phytoplankton and zooplankton assemblages and their relationships with environmental factors along trophic gradients in 50 lentic ecosystems across Thailand. Field sampling was conducted at 264 points in April and May 2024. Physical, chemical, and biological parameters were measured both in the field and the laboratory. Plankton samples were identified and quantified to assess species richness, abundance, and community composition. The results revealed that lentic water bodies could be classified into four trophic states: 1 oligotrophic, 6 mesotrophic, 17 eutrophic, and 26 hypereutrophic systems. This study found that phytoplankton density peaked in hypereutrophic waters, while species richness was highest in oligotrophic conditions. Nutrient-rich environments favored Cyanophyta dominance, whereas Dinophyta were more abundant in nutrient-poor systems. Zooplankton assemblages, particularly Rotifers and Copepoda, showed higher abundance in eutrophic and hypereutrophic ecosystems, while diversity was greater in mesotrophic and oligotrophic waters. Statistical analyses indicated that environmental factors, especially nutrient concentrations, played a significant role in shaping plankton assemblages along the trophic gradients. Cyanophyta showed strong positive correlations with total dissolved solid (TDS) (r = 0.383, p < 0.01) and electrical conductivity (EC) (r = 0.403, p < 0.01), while Dinophyta showed a strong positive correlation with dissolved oxygen (r = 0.319, p < 0.05). Zooplankton, particularly Rotifers, exhibited significant correlations with total phosphorus (TP) (r = 0.358, p < 0.05) and TDS (r = 0.387, p < 0.01). Multidimensional Scaling (MDS) analysis and Principal Coordinate Analysis (PCoA) confirmed that water quality variables strongly influenced community structure. This study provides important insights into how environmental factors drive phytoplankton and zooplankton assemblages across trophic gradients in Thai lentic ecosystems, contributing to the improved understanding and management of freshwater bodies and eutrophication. Full article

This study focused on microplastic pollution in the Bohai Sea, employing bibliometric analysis and meta-integration methods to systematically analyze its pollution characteristics and ecological risks. The results indicated that microplastics primarily originated from land-based inputs (62%) and marine activities (23%). Microplastic concentrations in the Bohai Sea’s coastal areas were significantly higher than in deep waters, and the abundance of microplastics in aquaculture sediments was three to five times that in non-aquaculture areas. Bioaccumulation demonstrated a significant trophic magnification effect, with top predators containing much higher microplastic concentrations than plankton. The combined toxicity of microplastics and pollutants severely impacted key species, leading to a 92% decrease in Chinese shrimp populations and a significant reduction in benthic biodiversity. To address this issue, a “four-in-one” prevention and control system was proposed, encompassing source reduction, intelligent monitoring, targeted treatment, and regional collaboration, with measures including policy, technological innovation, and ecological restoration. This aims to provide scientific evidence for Bohai Sea ecological security management and offer a reference for microplastic management in globally semi-enclosed seas. Full article

Lake Maggiore is a deep subalpine lake that has been well studied since the last century thanks to a monitoring program funded by the International Commission for the Protection of Italian–Swiss Waters. The monitoring program comprises both abiotic and biotic parameters, including zooplankton pelagic organisms. In this study, we present a dataset of 15,563 records of population densities and standing stock biomass for zooplankton pelagic taxa recorded over 43 years (1981–2023). The long-term dataset is valuable for tracing changes in trophic conditions experienced by the lake during the last century (eutrophication and its reversal) and the impact of global warming. Zooplankton samples (Crustacea and Rotifera Monogononta) were collected within 0–50 m depth by vertical hauls with an 80 µm light plankton sampler. The sampling frequency was monthly, with the exception of the 2009–2012 period, which employed seasonal frequency. The estimation of zooplankton taxon abundance and of its standing stock biomass is crucial in order to quantify the flux of matter, energy, and pollutants up to the upper trophic levels of the food web. The dataset provided is also suitable for food web analysis because the zooplankton taxa have been classified according to their ecological roles (microphagous organisms; primary and secondary consumers). Full article

Understanding the trophic interactions and community structure of zooplankton is essential for assessing energy transfer in marine ecosystems. This study investigates the spatial and seasonal variations in stable carbon (δ¹³C) and nitrogen (δ¹⁵N) isotopes of dominant mesozooplankton groups across three sub-basins of the Eastern Mediterranean (North Aegean, Cretan, and South Ionian Seas) during two seasonal surveys (October 2014 and May 2015). Zooplankton samples were collected using a WP-2 net and analyzed for taxonomic composition, abundance, biomass, and stable isotopic signatures to assess trophic positioning. The results indicate that copepods dominated the zooplankton community at all stations, with Clausocalanus and Oithona juveniles being the most abundant taxa. Salps contributed significantly at certain stations, reflecting regional variations in the planktonic food web structure. Zooplankton δ¹⁵N values exhibited pronounced spatial and seasonal differences, with higher enrichment observed in 2014 compared to 2015. The calculated trophic positions highlight the variability in feeding strategies among copepod species, with Calanus helgolandicus occupying the highest trophic position (TP = 3.34) and Lucicutia spp. the lowest (TP = 1.22). Isotopic niche analysis identified two distinct feeding guilds: a group relying on phytoplankton and microzooplankton and another exhibiting broader trophic plasticity, including omnivorous and carnivorous taxa. These findings underscore the complexity of zooplankton trophic interactions in the Eastern Mediterranean and the role of regional hydrographic conditions in shaping the food web structure. This study provides essential baseline data for future research on the impacts of climate change and nutrient variability on Mediterranean marine ecosystems. Full article

In order to understand the diel vertical migration and transport pattern during their early life stages, the vertical distribution of larvae and juveniles of the small yellow croaker (Larimichthys polyactis) in the Yangtze River estuary was investigated. Four sampling cycles were carried out at the station (122°39′ E, 31° N) during May and June 2015. The samples were collected by vertically discrete plankton hauls in three strata of the water column: surface (0~2 m depth), middle (8~10 m depth), and bottom (18~20 m depth). The total number of small yellow croaker larvae was 5523, of which 65.2% and 25.8% were postflexion larvae and juveniles, respectively. Most of the individuals were collected in mid-May, and the sum of the quantity in May accounted for 94.8%. In all cruises, the highest abundance occurred at the bottom, while the surface maintained the lowest abundance. The flexion larvae, postflexion larvae and juveniles moved up to the surface and middle at night, but there was no significant difference between night and daytime for preflexion larvae in each stratum. The postflexion larvae and juveniles showed low temperature responses and a preference for the bottom habitat, respectively, while the preflexion and flexion larvae had weaker selectivity to the water layer and occurrence time. The abundance of larvae and juveniles in the middle layer was significantly higher at flood tide than at ebb tide, and it was more dominant at night than during the day. The study indicates that larvae and juveniles of the small yellow croaker change their located depth with diel vertical migration and utilize the faster speed of the mid-upper layer, which contributes to their ingress into the Yangtze River estuary nursery ground. Full article

The present dataset served to evaluate the plankton community composition and abundance in Nuevo Gulf (42°42′ S, 64°30′ W), a World Heritage Site in Argentinian Patagonia and part of the Valdés Biosphere Reserve. It reports zooplankton abundance (>300 µm) and phytoplankton concentration (10–200 μm) during the spring and summer seasons from 2019 to 2021. Special attention was given to the taxonomic classification of zooplankton, leading to the first identification of jellyfish species within the Gulf and the detection of an unreported copepod for the area (Drepanopus forcipatus). Samples were collected at two depths—a surface and a deeper layer—to assess vertical distribution patterns of plankton communities and explore potential environmental drivers influencing their variability. This dataset provides a valuable baseline for future studies analyzing temporal variations in the Gulf’s plankton communities. Moreover, it encourages the local scientific community to contribute data and promote open access to marine biodiversity records in the region. Full article

Liangzi Lake, a typical shallow lake in the middle reaches of the Yangtze River, is important for water resource and biodiversity conservation. With the development of urbanization, anthropogenic activities have posed serious threats to the water quality and biodiversity of Liangzi Lake. To assess the aquatic ecosystem health of Liangzi Lake, the structure, the environmental response, and the interactions of plankton were investigated in 2022 and 2023. The results indicated that water temperature was a pivotal factor regulating plankton dynamics, with the assemblage patterns predominantly shaped by the phytoplankton species, which were Bacillariophyta in spring and Chlorophyta in summer. In terms of the phytoplankton, dissolved oxygen and the N:P ratio significantly affect cyanobacteria distribution. The high biomass and abundance of cyanobacteria in summer highlight the potential risk of harmful algal blooms. In contrast to the phytoplankton, the zooplankton exhibited enhanced resilience to changes in the surrounding environment. Rotifera was the dominant group in summer in terms of both abundance and biomass. Most core genera of plankton were jointly identified by eDNA metabarcoding and microscopical analysis, and eDNA metabarcoding had advantages in revealing a higher diversity. However, some taxa among rotifers such as Liliferotrocha were only identified using microscopical analysis. Therefore, a combination of both the methods is recommended to better understand the structuring mechanisms of plankton assemblages in lake ecosystems. Full article

Fishponds are regarded as hypertrophic systems accompanied by low biodiversity. We focused on the phytoplankton diversity of 15 fishponds located in Austria. Of the 15 fishponds, 12 waterbodies are aquaculture ponds stocked with common carp, which converted to organic farming some years ago with grain as supplementary feed, and 3 ponds are used for recreational fishing. The trophic state index increased from 59 to 71 in spring to 80 to 93 in autumn and classified the ponds as mid-eutrophic to hypertrophic. The taxa number was surprisingly high (taxa richness up to 100 taxa per pond). The phytoplankton resource use efficiency was in the upper range of eutrophicated waters and did not show seasonal differences (median Chlorophyll-a/total phosphorus = 1.94, Chlorophyll-a/total nitrogen = 0.12). Linking environmental data with the algal community resulted in a distinct temporal community pattern with a significant seasonal shift from the cooler season dominated by Ochrophyta taxa to green algae as the most abundant group in summer and autumn. Our findings challenge general assumptions regarding low phytoplankton diversity with long-lasting Cyanobacteria blooms and conform to the algal dynamics described in the plankton ecology group (PEG) model for temperate shallow lakes. These man-made systems are an ecological asset, highly connected to terrestrial habitats in their vicinity and significantly contributing to the ecological health and long-term sustainability of the region. Full article