Eutrophic Conditions Research Articles

Identification and Composition of Cyanobacteria in Ecuadorian Shrimp Farming Ponds-Possible Risk to Human Health.

Toxic cyanobacterial blooms in various water bodies have been given much attention nowadays as they release hazardous substances in the surrounding areas. These toxic planktonic cyanobacteria in shrimp ponds greatly affect the survival of shrimps. Ecuador is the second highest shrimp producing country in the Americas after Brazil; and the shrimp-based economy is under threat due to toxic cyanobacterial blooms in Ecuador shrimp ponds. This study investigated the abundance of different cyanobacteria in the shrimp ponds at the Chone and Jama rivers (in Manabi province) at Ecuadorian pacific coast, focusing on different environmental factors, such as temperature, pH, salinity, and light. Temperature and pH were identified as key factors in influencing the abundance of cyanobacteria, with a significant positive correlation betweenRaphidiopsis raciborskiiand pH. The highest and lowest abundance of cyanobacteria found during the dry season in the shrimp ponds near the Chone and Jama rivers were > 3 × 106 and 1 × 106Cell.m-3, respectively. The Shannon-Wiener Diversity Index fluctuated between 0.41-1.15 and 0.31-1.15 for shrimp ponds of Chone and Jama rivers, respectively. This variation was linked to changes in salinity and the presence of harmful algal blooms, highlighting the importance of continuous monitoring. Additionally, the study areas showed eutrophic conditions with low diversity, underlining the need for additional spatiotemporal studies and expanded research in both rivers, to better understand these complex phenomena. The findings underscore the importance of continuous monitoring and expanded research in cyanobacteria ecology, with implications for public health and aquatic resource management.

Biotic regulation of phoD-encoding gene bacteria on organic phosphorus mineralization in lacustrine sediments with distinct trophic levels

Organic phosphorus (Po) mineralization hydrolyzed by alkaline phosphatase (APase) can replenish bioavailable P load in the sediment water ecosystem of lakes. However, the understanding about the interaction between P load and bacteria community encoding APase generation in the sediment are still limited. Different P pools in the sediments from Taihu Lake, China were measured using sequential extraction procedure. The APAase activity (APA) were obtained accompanying with enzymatic dynamical parameters Vmax and Km. The abundances and diversity of gene phoD-harboring bacterial communities were assessed using high throughput sequencing. The analysis results showed the decrease of potentially bioavailable P fractions including MgCl2-P and Fe-P along sampling gradient southwards together with active P concentrations in the water. Conversely, increasing APA and absolute abundance of phoD gene were found with the decreasing of P loads southwards. Positive correlation (p < 0.05) between absolute abundance and APA indicated that phoD-encoding bacteria manipulated the APA and Po mineralization. Negative correlation (p < 0.01) suggested that the APA was restrained by high P load and was promoted under low P condition. However, higher Vmax and Km values suggested that high mineralization potential of Po maintained the high concentrations of potentially bioavailable P even the APA was restricted. The abundance increase of predominant genus Cobetia (from 15.51 to 24.34 %) mirrored by the reduced Calothrix abundance (from 24.65 to 1036 %) was speculated to be responsible for the APA promotion under low P condition. Higher diversity indices in the high P scenario suggested that high P load stimulated the ecological diversity of gene phoD-encoding bacteria community. Generally, rare taxa such as Burkholderia having high connected degrees in bacterial communities together with abundant genera synergistically manipulated the phoD gene abundance and APase generation. Interaction between P fractions and bacteria encoding phoD gene determined the eutrophication status in the lacustrine ecosystem.

Ocean bottom-water oxygenation across the Late Miocene–Early Pliocene biogenic bloom

The Late Miocene–Early Pliocene biogenic bloom (ca. 9–3.5 millions of years ago, My) represents a period of globally heightened marine biological productivity. Paleoenvironmental studies across this interval show alternating phases of low-oxygen eutrophic and well-oxygenated oligotrophic conditions. Here, we focus on the bottom water oxygenation changes during the biogenic bloom to assess the validity of the enhanced Benthic Foraminifera Oxygen Index (EBFOI). The index was calculated for three ocean drilling sites: Ocean Drilling Program Site 1085 (southeast Atlantic), and International Ocean Discovery Program sites U1506 (southwest Pacific) and U1488 (equatorial Pacific). The quantitative study of benthic foraminiferal assemblages from Site 1488 allowed us to infer the paleoenvironmental evolution across the biogenic bloom. At this site, we document a shift from stable oxygen concentrations and seasonal input of phytodetritus (8.7–4.3 My) to short-term fluctuations between low oxygen eutrophic conditions and well-oxygenated oligotrophic conditions (4.3–3.0 My). The EBFOI calculated at sites 1085 and U1506 was cross-referenced with the published paleoenvironmental conditions. While the EBFOI proves to be a valuable tool to infer paleoenvironmental changes at the seafloor, it has limitations, as evidenced by comparisons with paleoenvironmental interpretations of Site U1488, where it does not consistently align with inferred oxygen conditions.

A four-season exploration of surface water quality and trophic status in the highly dynamic waters of Karun-4 Dam Lake, SW Iran

This study explores seasonal fluctuations in water quality and phytoplankton communities within Karun-4 Dam Lake, the largest double-arch dam in the Middle East situated in Iran. Employing a systematic approach, 26 sampling stations were strategically selected to collect surface water samples at a depth of 50 cm during the midpoints of each season throughout 2019. Significant seasonal variations in water quality parameters and phytoplankton composition were observed. Predominant species included Chrysophyceae (38%) and Bacillariophyceae (32%), indicative of nutrient-rich conditions, particularly during spring and summer, as evidenced by the eutrophic state (Carlson Trophic State Index: 59.43 and 53.96, respectively). Summer exhibited the highest diversity (Shannon–Wiener Index = 2.27) and lowest evenness (Pielou’s Evenness Index = 0.21). PCA and CCA analyses revealed season-specific preferences for nutrients and ions among phytoplankton species. Water temperature emerged as a crucial factor in spring and summer, while environments with elevated bicarbonate and alkalinity levels were less favorable during winter and fall. This study provides essential insights into Karun-4 Lake's dynamic ecological conditions, underscoring the necessity for ongoing monitoring to discern long-term trends and anthropogenic impacts for effective ecosystem management.

Stratigraphic and paleoceanographic alternations within a Mediterranean semi-enclosed, syn-rift basin during Marine Isotope Stage 5: The Gulf of Corinth, Greece

The Gulf of Corinth represents an ideal setting for studying the impact of sea level changes and regional climate on a semi-enclosed, syn-rift basin. Here we investigate the stratigraphic and paleoceanographic variability recorded in the sedimentary succession of the basin over the Marine Isotope Stage (MIS) 5 period when global sea level and climatic conditions along the eastern Mediterranean exhibited pronounced fluctuations. We used sedimentological (granulometry, composition), micropaleontological (planktic and benthic foraminifera), and isotopic (stable δ18O, δ13C, and clumped isotope) proxies on core samples from site M0079A (IODP Expedition 381) combined with additional data from the expedition overview and records from the surrounding area. The sedimentary succession comprises an alternating pattern of a) bioturbated, biogenic-rich deposits associated with increased hemipelagic sedimentation with b) partly bedded, detrital-rich sediments attributed to intercalated sediment gravity flows within the hemipelagic background under low oxic sea-surface conditions, and c) aragonite-rich laminated deposits, indicating either transitional conditions between marine and isolated environment or a highly stratified seawater column and low oxygen seafloor conditions. We find that the Gulf of Corinth lay under marine conditions for nearly the entire MIS 5 period, while the Rion sill would have been possibly shallower, even 10 m, than the current depth. Nevertheless, water exchange was restricted during the MIS 5a – MIS 4 transition when the sea level fluctuated very close to the sill height. The hydrological conditions within the Gulf during most of the highstands MIS 5a, 5c, and 5e reflect higher oxygen levels and/or increased nutrient availability compared to the Holocene and present-day regime. The combined effects of Ionian Sea inflows and enhanced riverine runoff led to increased water column stratification and low oxygen, eutrophic seafloor conditions in the Gulf of Corinth during times of high precipitation in southern Europe and deposition of sapropels S3, S4, and S5 throughout the eastern Mediterranean. In contrast, during periods of widespread cold and arid conditions in the eastern Mediterranean, water column mixing was intense within the Gulf. Prevalent marine conditions are also proposed during the MIS 5b and 5d lowstands, yet associated with predominately bedded-detrital sediments in the Gulf. A complementary investigation in the adjoining Patras Gulf is suggested to fully comprehend the dynamics of climate and sea level changes in complex rift systems.

Assessment of the eutrophication status at Mediterranean sub-basin scale, within the European Marine Strategy Framework Directive

The aim of this work is to define harmonized reference conditions and assessment thresholds for selected criteria elements of the Marine Strategy Framework Directive (MSFD) Descriptor 5 (Eutrophication) in the Eastern Mediterranean Sea and to test if a tool for integrated assessment of the status of marine systems can be used as a common methodological approach. In this frame, we tested two statistical approaches in order to set threshold values for four criteria of Descriptor 5: nutrients, chlorophyll a, transparency and dissolved oxygen in the bottom waters. It is noteworthy that this work revealed the need to apply common procedures in data treatment and assessment evaluation. This is the first attempt to set common methods for the assessment of eutrophication in the Eastern Mediterranean, which is essential in marine environments, especially those shared by several countries. To this end, we have applied common criteria and metrics and established thresholds “Good” and “Moderate” for nutrients, chlorophyll a, transparency and dissolved oxygen in the bottom waters for the different Water Types of the Adriatic and Aegean Seas (I, II, IIIW, IIIE), based on datasets provided by Italy, Slovenia, Croatia and Greece. The selected criteria elements were common for all countries, providing a unified approach to GES assessment of two case study areas: the Adriatic Sea and the Saronikos Gulf. Dissolved Inorganic Nitrogen (DIN) threshold values of 15.6, 6.85, 1.61 and 2.11 μmol L−1 were set for the Water Types I, II, IIIW and IIIE, respectively.We also tested if an aggregation tool for GES assessment, such as Nested Environmental status Assessment Tool (NEAT), could be used as a common methodological approach. The comparison of NEAT with TRIX showed good comparability. In this end, NEAT can be used as a useful and much needed assessment tool for assessing eutrophication status of the marine.

Taxonomic review, palaeoecological, and palaeobiogeographical significances of Campanian Tethyan oysters from the North Eastern Desert, Egypt

The Late Cretaceous was a time of high eustatic sea level that enabled extensive epicontinental seaways and carbonate platforms across the Tethyan Realm, providing favorable habitats for oyster communities to flourish. This study focuses on the Campanian Tethyan oysters from the North Eastern Desert of Egypt regarding taxonomy, palaeoecology, and palaeobiogeography. Three oyster species, Nicaisolopha nicaisei (Coquand, 1862), Pycnodonte (Phygraea) vesicularis (Lamarck, 1806), and Ambigostrea bretoni (Thomas and Peron, 1891), were identified from the Campanian succession in two studied sections. The sampled specimens of the genus Nicaisolopha have undergone a systematic palaeontological revision. As a result, N. tissoti (Thomas and Peron, 1891) is considered herein a junior synonym of N. nicaisei (Coquand, 1862). Palaeobiogeographically, the likely primary migration pattern of the studied oysters suggests an east–west trend along the Southern Tethys margin. All identified oysters in this study exhibit a Tethyan affinity and are primarily abundant in two main provinces: the Southern Tethys and the Western Tethys. The macrofaunal contents are categorized into two fossil associations: the Nicaisolopha nicaisei association of the middle-late Campanian age and the Pycnodonte vesicularis association of the late Campanian age. These macrofaunal associations indicate a deepening trend during the middle-late Campanian age, suggesting a transition from shallow inner neritic to middle neritic environments. Additionally, it is observed that Pycnodonteinae tend to grow larger under eutrophic conditions, low-energy environments, and nutrient-rich waters with high carbonate contents.

Synergy of lacustrine groundwater discharge and algal biomass on CH4 and CO2 pathways and emissions in a large shallow eutrophic lake

Inland lakes are known to be a significant component of the global carbon (C) cycle, with C pathways in these lakes potentially changing alongside their eutrophic states. One factor contributing to eutrophication is lacustrine groundwater discharge (LGD), which is also a key conduit for CH4 and CO2 to enter lakes. However, the regulation of LGD on CH4 and CO2 behavior in these lakes remains unclear. To address this gap, we conducted continuous monitoring of 222Rn, CH4 and CO2, and δ13C at two sites with distinct algal densities in Lake Taihu, a large shallow eutrophic lake in China, and aimed to investigate the synergy of LGD and algal biomass on CH4 and CO2 pathways and emissions. We found that organic matter (OM) degradation is the dominant factor controlling CH4 and CO2 production in the lake, and this process appears to be facilitated by the presence of ample OM and reduced oxygen level at the site with high algal density. In addition, LGD is found to be a significant contributor of CH4 and CO2 to the lake, and the nutrients derived from LGD play a crucial role in regulating the proliferation of algae in the lake. As algal density increases, gas emissions such as CH4 ebullition and CO2 diffusion are amplified, while processes such as CH4 oxidation and atmospheric CO2 exchange within lakes are attenuated. The contribution of LGD to CH4 and CO2 inventories in the lake also decreases as OM degradation becomes a more significant contributor. This study highlights LGD regulation on the C flux and underscores the importance of synergistical studies from both ecological and hydrogeological perspectives in comprehending lacustrine C flux dynamics.

Spatiotemporal Assessment of Water Pollution for Beira Lake, Sri Lanka

Beira Lake, located in Colombo, Sri Lanka, has suffered severe anthropogenic impacts, with previous restoration attempts failing due to a limited understanding of pollutant dynamics. Aiming to fill this gap, a comprehensive study was conducted during dry and wet seasons to assess the spatiotemporal water pollution of Beira Lake, employing key physicochemical parameters, numerical indices, and remote sensing analysis. The water pollution index (WPI) results categorize Beira Lake as highly polluted, with WPI values ranging from 2.38 ± 0.92 in the wet season to 2.53 ± 1.32 in the dry season. Comparatively higher COD levels recorded in the Beira Lake network, especially for Gangarama Lake show significant pollution levels during both the dry and wet seasons, e.g., the highest COD levels, at 306.40 mg/L, were observed during the wet season. The Trophic State Index (TSI) results indicate eutrophic and hypereutrophic conditions in Beira Lake, which are particularly pronounced during the wet season. The heavy metal pollution index (HPI) results suggest elevated heavy metal concentrations in Beira Lake, especially in the wet season. Combined with field investigation results, a remote sensing data analysis between 2016 and 2023 reveals significant improvements in water transparency, suggesting positive effects of recent management interventions. Parameters demanding attention include COD, nitrate, and total phosphate levels due to their consistent exceedance of permissible limits. The PCA results of indices correlations between wet and dry seasons offer valuable insights into the complex dynamics of Beira Lake’s water quality. The study makes recommendations for restoring Beira Lake, including stringent pollution controls, regular dredging, green infrastructure implementation, implementing new rules and regulations, and community engagement.

Community science approach reveals temporal and eutrophication-related spatial patterns in bladderwrack-associated invertebrate fauna

Coastal zones are affected by a variety of anthropogenic drivers. While scientific assessments of the large-scale impacts are often insufficient due to limited resources, community science approaches (i.e. engaging voluntary participation by the general public in scientific research) may allow studying processes on larger geographic and/or temporal scales. In this study, a community science campaign was launched to assess geographic and temporal patterns in subtidal bladderwrack (Fucus vesiculosus) -associated invertebrate fauna along the coastal eutrophication gradient of the Finnish Baltic Sea coast in 2020–2021. The data collected by the community scientists were quality-controlled and generally similar to scientist-collected data. However, most taxa had somewhat lower abundances than data collected with another, more established sampling method. The community composition of fauna differed between areas with varying eutrophication status, and the total abundances of fauna were highest in the areas with the lowest eutrophication impacts. The data also revealed spatial and temporal patterns of individual taxa. For example, the abundance of blue mussel (Mytilus edulis) was highest in less eutrophied areas, while the abundance of non-indigenous Harris mud crab (Rhithropanopeus harrisii) was highest in the areas with moderate eutrophication impacts. A two-fold increase in the abundance of isopods that graze on bladderwrack was observed between the study years, indicating a sizeable temporal variation in bladderwrack grazing pressure. The study provides novel information on bladderwrack-associated invertebrate fauna and the applicability of using community science in marine subtidal research. The results suggest that community science is an effective approach to assessing subtidal community-level patterns, and its continued use is recommended to complement data collection across large spatial and temporal scales in marine key habitats.

Unraveling ecological signals related to the MECO onset through planktic and benthic foraminiferal records along a mixed carbonate-siliciclastic shallow-water succession

The shallow-water Capo Mortola succession (Liguria, NW Italy) yields diverse assemblages of smaller benthic and planktic foraminifera, larger benthic foraminifera (LBF), and calcareous nannofossils. With the aim of improving the understanding of the Middle Eocene Climatic Optimum (MECO) impact on the shallow-water marine biotic communities due to global warming, we provide biostratigraphic and stable isotope data to achieve a reliable stratigraphic constraint of the MECO. The correlation of the stable isotope oxygen data with datasets of similar age from other regions suggests that only the onset of the MECO interval is recorded in the Capo Mortola section. Quantitative analyses of smaller benthic foraminiferal assemblages indicate that the shallow-water setting of Capo Mortola was not particularly affected by the onset of the MECO perturbance because no variation in nutrient supply or oxygen level were detected. A different scenario is recorded by the LBF genera Operculina and Discocyclina, which increased in abundance across the MECO onset, probably due to a rise in temperature and adapting to the increase in nutrient supply. In the upper water column, the variations in calcareous plankton communities appear to be controlled by both the MECO warming and a moderate increase in eutrophic conditions related to the enhanced hydrological cycle. Nutrients, mostly consumed in the upper water column, reached the seafloor in a limited amount, as benthic foraminifera record a meso-oligotrophic environment across the studied MECO interval.

Does water transparency control the banding in shallow water iron formations?

Abstract Iron formations (IFs) are marine chemical sediments that are conined to the Precambrian rock record and provide unique insights into the co-evolution of the atmosphere-hydrosphere and biosphere through almost three billion years of Earth’s history. IFs commonly appear throughout the Archaean until the Palaeoproterozoic ca. 1.8 billion years ago and re-appear during the “Snowball Earth” epoch in the Neoproterozoic. The formation and deposition mechanism(s) of IFs are, however, still incompletely understood, hindering unique interpretations of palaeoenvironments. Many IFs are banded iron formations (BIFs) with layer thickness of alternating Fe- and Si-rich layers ranging over several orders of magnitude from the nanometre to the metre scale. A second textural type, so called granular iron formations (GIFs) that form above storm wave base become widespread in the Palaeoproterozoic. Understanding the fundamental mechanisms that are responsible for the textural types and the periodicity of banding in BIFs is crucial to link these features to the environmental and geochemical evolution of the Earth. We here provide a conceptual model that highlights the role of changing light conditions and water transparency for Iron Formation (IF) precipitation. We show that the model is particularly feasible for IFs deposited in shallow waters but may also be applicable for some IFs deposited in deeper water settings. The model builds on other primary Banded Iron Formation (BIF) precipitation models postulating that Fe(III)-(oxyhydr)oxide production can be dominated by anoxygenic photoautotrophic Fe2+-oxidising bacteria. These so called photoferrotrophs are adapted to very low light levels corresponding to about 1% of the light level required by oxygen-producing phototrophs allowing them to thrive deep down in the water column. The depth of Fe(III)-(oxyhydr)oxide production is mainly controlled by water turbidity which controls how deep photosynthetically available radiation (PAR) penetrates the water column. Eutrophic conditions result in relatively shallow Fe(III)-(oxyhydr)oxide production depth due to turbidity either induced by the biomass itself and/or by particles that are actively or passively produced by microorganisms (e.g., Fe(III) and Mn(IV)-(oxyhydr)oxides, sulphides), triggering the formation of Fe-rich bands. During oligotrophic stages, Fe(III)-(oxyhydr)oxides are only produced relatively deep down in the water column, so that only silica-rich bands form in the Fe(III)-(oxyhydr)oxide free upper water column. Reactive transport modelling adopted from Ozaki et al., (2019) shows that besides upwelling and nutrient supply, alternating Fe(III) production depth is mainly associated with changing light conditions as a result of water transparency. Periodicities reflected by alternating Fe- and Si-rich bands in IFs in our model can thus be associated with: (1) nutrient supply patterns; (2) additional sources of turbidity in the water column such as Fe(III) and Mn(IV) oxide particles, sulphides, and wind-blown silicate particles; or (3) formation and clearing of organic haze in the atmosphere. One or all of these reasons for low light conditions seem to become more important in the Palaeoproterozoic (&amp;lt;2.4 Ga) and could be partly responsible for the more widespread occurrences of shallow marine granular IFs relative to former epochs, which is often assigned to the gradual oxidation of the ocean. Our model shows that variable water transparency should be considered as additional factor for IF deposition especially for shallow marine settings. This model also reasonably explains the prominent layering in BIFs as syn-depositional feature.

Environmental indicators of lake ecosystem health in Aotearoa New Zealand: current state and trends

Assessments of lake ecosystem health, based on indicators of physical–chemical water quality, ecological conditions, and human health risks, are needed to apprise the public and facilitate lake management. While unrefereed lake water quality reports exist, this is the first peer-reviewed study to report data processing and analysis methods and results for current state and recent trends in multiple environmental indicators in monitored lakes across Aotearoa New Zealand. Lake grading based on national criteria indicated that many lakes are failing to achieve statutory bottom lines for phytoplankton chlorophyll a, total nitrogen, and total phosphorus concentrations. In contrast, most monitored lakes had high grades for two human health risk indicators, E. coli and cyanobacteria concentrations, and for potential toxicity of ammonia for biological communities. We included 166 lakes and considered indicator state and trends for two lake classifications based on geomorphology and land cover. Elevated scores for an indicator of trophic state (the trophic level index; TLI) in most shoreline, riverine, peat, landslide, dam, and aeolian lakes indicated eutrophic conditions or worse. Lower TLI scores were indicative of oligotrophic conditions in most glacial lakes. Nutrient, E. coli and suspended sediment concentrations and TLI scores were positively correlated, and Secchi depths negatively correlated, with high-intensity agricultural land cover. Ten-year trend analyses indicated that lakes with increasing Secchi disk depth, chlorophyll a, dissolved reactive phosphorus, E. coli, ammoniacal nitrogen, TLI, total nitrogen, and total suspended solids trends outnumbered those with decreasing trends. Twenty-year trend analyses indicated that the numbers of lakes with increasing and decreasing trends in most of the indicators we assessed were comparable, but lakes with increasing 20-year trends in total nitrogen outnumbered those with decreasing trends, and lakes with decreasing 20-year trends in ammoniacal nitrogen, dissolved reactive phosphorus, total phosphorus, and nitrate nitrogen outnumbered those with increasing trends. This study presents clear data processing steps and trend analysis methods as applied to a nationwide dataset for Aotearoa New Zealand, while acknowledging data limitations. For example, the choice of trend periods is challenging and can greatly affect conclusions. The results of this empirical study and the collective results of preceding studies of lake ecosystem health indicate that eutrophication poses a threat to the ecological health of many if not most lakes in Aotearoa New Zealand. Recommendations include monitoring network expansion especially for the indicators bottom dissolved oxygen and cyanobacteria (toxic and total cyanobacteria biovolumes) and judicious selection of trend periods in lake-specific trend analyses to determine causes for increasing or decreasing trends in environmental indicators.

Study on water quality safety and microbial diversity of water source reservoirs in Daqing City

Water source reservoirs play a vital role in ensuring the drinking water safety. To explore the safety of water quality as the source of water supply projects in Daqing City, the chemical indexes of water quality in Daqing reservoir, Dongcheng reservoir and Hongqi reservoir were analyzed. The microbial diversity, community structure characteristics and Nitrogen metabolism functional bacteria were analyzed by high-throughput sequencing technology. Monitor the disinfection effect of three water source reservoirs after using sodium hypochlor disinfection. The results showed that, in 2021, the reservoirs water body was in a moderately eutrophic state, the main exceeding standard index was total nitrogen (TN) (1.25–1.57 mg/L). The microbial communities in water body and sediments were composed of 1048 genera. The microbial diversity in sediment was higher than that in water. Potential pathogenic microorganisms were detected in water and sediment samples. Although no coliform bacteria were detected, as a water source disinfection was also necessary. Redundancy analysis (RDA) showed that, the main water quality factors affecting microbial community structure in water samples were pH, in sediment samples were water temperature (WT), dissolved oxygen (DO), TN and total phosphorus (TP). Sodium hypochlorite has a good disinfection effect and can ensure the safety of drinking water.

Phytoplankton species and traits response to a gradient of urbanization in subtropical lowland streams

AbstractLotic environments are among the most vulnerable aquatic ecosystems, and changes occurring in them happen faster than our capacity to measure the impacts, with the choice of community attributes that best reflect these disturbances still unclear. In this study, we evaluated the response of phytoplankton species and species traits along a gradient of urbanization in lowland streams. To do this, we sampled nine streams in three areas classified as densely populated (DP), low populated (LP), and rural areas (RA) during the four seasons (n = 108), considering relevant limnological variables (including metals, herbicides, and inorganic nutrients) and phytoplankton. Phytoplankton was analysed using taxonomic and morpho‐functional traits approaches. We used several multivariate analyses to assess phytoplankton species and trait distribution among stream groups (DP, LP, RA) and identify their environmental drivers. We found that phytoplankton responded to the urbanization gradient at both taxonomic and functional levels. However, this response was mediated by the land use (urban vs. rural) rather than its intensity. The main stressors detected were eutrophic conditions and organic matter contamination, which differed among groups (DP‐LP and RA). Both approximations indicated eutrophic, organically enriched conditions, but the situation varied among seasons and stream groups. The response of the taxonomic approach was clearer than the traits‐based approach, showing differences in density only between stream groups in the summer and the spring. Phytoplankton was responding to the gradient of urbanization in these subtropical lowland streams, but the seasonality, especially temperature and changes in the water column mixing also mediate the effect.

Long-term prediction of algal chlorophyll based on empirical models and the machine learning approach in relation to trophic variation in Juam Reservoir, Korea

This study analyzed spatiotemporal variation and long-term trends in water quality indicators and trophic state conditions in an Asian temperate reservoir, Juam Reservoir (JR), and developed models that forecast algal chlorophyll (CHL-a) over a period of 30 years, 1993–2022. The analysis revealed that there were longitudinal gradients in water quality indicators along the reservoir, with notable influences from tributaries and seasonal variations in nutrient regimes and suspended solids. The empirical model showed phosphorus was found to be the key determinant of algal biomass, while suspended solids played a significant role in regulating water transparency. The trophic state indices indicated varying levels of trophic status, ranging from mesotrophic to eutrophic. Eutrophic states were particularly observed in zones after the summer monsoons, indicating a heightened risk of algal blooms, which were more prevalent in flood years. The analysis of trophic state index deviation suggested that phosphorus availability strongly influences the reservoir trophic status, with several episodes of non-algal turbidity at each site during Mon. Increases in non-algal turbidity were more prevalent during the monsoon in flood years. This study also highlighted overall long-term trends in certain water quality parameters, albeit with indications of shifting pollution sources towards non-biodegradable organic matter. According to the machine learning tests, a random forest (RF) model strongly predicted CHL-a (R2 = 0.72, p < 0.01), except for algal biomass peaks (>60 μg/L), compared to all other models. Overall, our research suggests that CHL-a and trophic variation are primarily regulated by the monsoon intensity and predicted well by the machine learning RF model.

Phytochemical Composition, Anti-Inflammatory Property, and Anti-Atopic Effect of Chaetomorpha linum Extract.

Utilizing plant-based resources, particularly their by-products, aligns with sustainability principles and circular bioeconomy, contributing to environmental preservation. The therapeutic potential of plant extracts is garnering increasing interest, and this study aimed to demonstrate promising outcomes from an extract obtained from an underutilized plant waste. Chaetomorpha linum, an invasive macroalga found in the Orbetello Lagoon, thrives in eutrophic conditions, forming persistent mats covering approximately 400 hectares since 2005. The biomass of C. linum undergoes mechanical harvesting and is treated as waste, requiring significant human efforts and economic resources-A critical concern for municipalities. Despite posing challenges to local ecosystems, the study identified C. linum as a natural source of bioactive metabolites. Phytochemical characterization revealed lipids, amino acids, and other compounds with potential anti-inflammatory activity in C. linum extract. In vitro assays with LPS-stimulated RAW 264.7 and TNF-α/IFN-γ-stimulated HaCaT cells showed the extract inhibited reactive oxygen species (ROS), nitric oxide (NO), and prostaglandin E2 (PGE2) productions, and reduced inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) expressions via NF-κB nuclear translocation, in RAW 264.7 cells. It also reduced chemokines (TARC/CCL17, RANTES/CCL5, MCP-1/CCL2, and IL-8) and the cytokine IL-1β production in HaCaT cells, suggesting potential as a therapeutic candidate for chronic diseases like atopic dermatitis. Finally, in silico studies indicated palmitic acid as a significant contributor to the observed effect. This research not only uncovered the untapped potential of C. linum but also laid the foundation for its integration into the circular bioeconomy, promoting sustainable practices, and innovative applications across various industries.

Temporal Assessment of Phosphorus Speciation in a Model Ramsar Lake System in Asia

This study focused on monitoring phosphorus (P) concentrations in the water of the Ramsar site, Lake Vembanad, with a special focus on the mouths of the river bodies draining into the lake, a known hotspot for eutrophication. Four phosphorus fractions—total reactive phosphorus (TRP), total acid hydrolysable phosphorus (TAHP), total organic phosphorus (TOP), and total phosphorus (TP)—were monitored during the pre-monsoon and post-monsoon seasons. The results revealed high levels of all monitored phosphorus fractions, with an average concentration exceeding 300 ppb P across both seasons, indicating a highly eutrophic state. Notably, TRP, TOP, and TP showed high concentrations in both the pre-monsoon and post-monsoon periods. These data suggest significant phosphorus input into the lake’s surface water, potentially triggering excessive algal growth and threatening the biodiversity of this rich wetland ecosystem.

Distribution of toxigenic cyanobacteria in Alpine lakes and rivers as revealed by molecular screening

The increasing frequency of cyanobacteria blooms in waterbodies caused by ecosystem eutrophication could endanger human health. This risk can be mitigated by effective monitoring incorporating molecular methods. To date, most molecular studies on toxigenic cyanobacteria have been limited to microcystins (MCs), disregarding other cyanotoxins, to freshwater planktic habitats while ignoring benthic habitats, and to limited geographic areas (usually one or a few specific waterbodies). In this study, we used PCR-based methods including PCR product sequencing and chemical-analytical methods (LC-MS/MS) to screen many plankton (n = 123) and biofilm samples (n = 113) originating from 29 Alpine lakes and 18 rivers for their cyanotoxin production potential. Both mcyE (indicating MC synthesis) and anaC (indicating anatoxin (ATX) synthesis) gene fragments were able to qualitatively predict MC or ATX occurrence. The abundance of mcyE gene fragments was significantly related to MC concentrations in plankton samples (R2 = 0.61). mcyE gene fragments indicative of MC synthesis were most abundant in planktic samples (65 %) and were assigned to the genera Planktothrix and Microcystis. However, mcyE rarely occurred in biofilms of lakes and rivers, i.e., 4 % and 5 %, respectively, and were assigned to Microcystis, Planktothrix, and Nostoc. In contrast, anaC gene fragments occurred frequently in planktic samples (14 % assigned to Tychonema, Phormidium (Microcoleus), and Oscillatoria), but also in biofilms of lakes (49 %) and rivers (18 %) and were assigned to the genera Phormidium, Oscillatoria, and Nostocales. The cyrJ gene fragment indicating cylindrospermopsin synthesis occurred only once in plankton (assigned to Dolichospermum), while saxitoxin synthesis potential was not detected. For plankton samples, monomictic and less eutrophic conditions were positively related to mcyE/MC occurrence frequency, while oligomictic conditions were related to anaC/ATX frequency. The anaC/ATX frequency in biofilm was related to the lake habitats generally showing higher biodiversity as revealed from metabarcoding in a parallel study.

Deciphering the intricate link between watershed-level land use changes and reservoir eutrophication in central Argentina over the 20th-21st century

In Anthropocene, unbalances of the water cycle have created a severe threat to the supply of this crucial element for current and future generations. In addition, water quality degradation has been promoted by the land-use change from natural ecosystems to urbanized and industrialized areas, favoring the nutrient input into water bodies. In the last two decades, the San Roque reservoir (SRr), situated in central Argentina, has become hypereutrophic. In this work, we proposed an integrated study strategy that included a multiproxy examination of the reservoir sedimentary record and a study of land-use changes, in order to: 1) link land-use change to primary productivity of the SRr over the last 100 years; and 2) identify the processes involved in the SRr's environmental evolution prior and after urban expansion occurred by 1980 CE. Results allow to recognize two distinctive scenarios: a) Pre-urban scenario (1898–1983 CE) reflected by a dominance of allochthonous organic matter in the sedimentary record derived from the catchment's deforestation and, b) A transition towards increasing lake internal productivity (1984–2018 CE), resulting in a eutrophic state with cyanobacteria dominance due to catchment urban densification, particularly in the peri-lacustrine area. This work constitutes a novel tool by combining a paleolimnological approach with demographic analysis to accurately track the consequences of land use change on the water body and, in addition, provide the basis for modeling future scenarios.