Sampling Stations Research Articles

Distribution characteristics of microplastics in the surface mixed layer of the western Indian Ocean

The abundance, characteristics, and distribution of microplastics in almost all aquatic environments have been well documented. However, the distribution of microplastics in open oceans, especially in the western Indian Ocean, is rarely studied. Hence, for the first time, we determined the meridional distribution characteristics of microplastics in the surface mixed layer of the western Indian Ocean during the boreal summer monsoon in 2017. We used the multiple opening and closing nets and environmental sampling system to collect microplastics from 11 stations between 5°N and 16°S along 67°E in the western Indian Ocean; the surveyed stations with similar temperature and salinity profiles were clustered into four groups. Microplastics were detected at all sampling stations. The mean abundance of microplastics in the study area was 0.23 ± 0.04 particles/m3, and black-colored polyester fibers 1.0–5.0 mm in size were the most abundant type of microplastics among the samples collected. However, the mean abundance of microplastics differed among the clustered groups due to the influence of different ocean currents associated with each group, indicating meridional heterogeneity in the distribution of microplastics in the surface mixed layer of the western Indian Ocean. These findings provide reliable information for a better understanding of the characteristics of microplastics in the surface waters of the western Indian Ocean.

Impacts of fish pond effluent on the water quality of an afrotropical stream: a comprehensive evaluation using the water quality index

This study highlights the importance of managing fishpond effluent to minimize its impact on aquatic environments. Fish effluents are a major concern worldwide in aquatic environments. It also provides information on the impacts of effluents on the water quality index of streams when released into aquatic environments. Streams and fishponds were sampled bimonthly for two annual cycles, covering different sampling stations both upstream and downstream of the fishpond effluents at 50-m intervals. Water quality parameters associated with in situ conditions were determined in the field. In the laboratory, other physicochemical parameters were determined via proper standard protocols. The results of the study revealed that water quality parameters such as turbidity, total suspended solids, total solids, conductivity, total dissolved solids, dissolved oxygen, biological oxygen demand and organic matter recorded in water samples collected from 50 m upstream at the point of effluent discharge were significantly (p < 0.05) different from those recorded at other sampling stations. The WQI value of the discharge point was higher than the WQI recorded in both the upstream and downstream sections of the stream. The findings of this study showed that the point of discharge of fishpond effluents is particularly concerning for the receiving stream compared with other sampling points. This localized area has experienced marked deterioration in water quality, posing significant threats to the health and biodiversity of aquatic ecosystems. The effluent's impact, though slight when dispersed in the receiving waterbody, underscores the necessity for adequate management practices to mitigate its adverse effects. Effective strategies, including regular monitoring, effluent treatment, and sustainable pond management, are imperative to ensure the long-term health and resilience of the aquatic environment.

Aerobiology of Olive Pollen (Olea europaea L.) in the Atmosphere of the Iberian Peninsula

Olea europaea L. pollen is one of the main causes of pollinosis and respiratory diseases in the Iberian Peninsula (IP). The aim of this study was to provide a pollen calendar in different regions of the IP, which could help allergists and allergic patients in the management of Olea europaea allergic diseases, and to update/complement what has already been reported on olive trees’ aeropalynology in this region. Airborne Olea pollen dynamics were analyzed over a period of 8 years in a total of 21 localities, 7 in Portugal and 14 in Spain. Airborne pollen monitoring was carried out using the Hirst-type spore trap method and following the recommendations of the Quality Control Working Group of the European Aerobiology Society. The daily pollen count, the annual pollen profile, the Annual Pollen Integral (APIn), the Seasonal Pollen Integral (SPIn) and the Pollen Peak, all expressed in number of pollen grains per cubic metre of air, together with the main pollen season and its characteristics, the Start Day, the End Day and the length of the pollen season, were calculated for each sampling station. Differences in mean Olea pollen concentration between odd and even years were also analyzed. On average, the main pollen season (MPS) started in April/May and ended in June, with Pollen Peaks recorded in May, except in Burgos, where it was recorded in June. The longest MPS occurred in Lisbon, Oviedo and Valencia (53 days) and the shortest in Vitoria (25 days). A high daily pollen concentration (i.e., &gt;200 grains/m3) was recorded between 1 and 38 days along the year in all sampling stations of the southwest quadrant of the IP and in Jaén. A biannual pattern, characterized by alternating years of high and low pollen production, was found in the southwest of the IP. In conclusion, the study provided a deeper understanding of the pollination behaviour of olive trees in the IP and allowed the establishment of a representative Olea pollen calendar for this region. In addition, our results suggest the usefulness of investigating more detailed relationships between annual Olea pollen, allergen sensitization and symptoms, both for allergists involved in the study and management of allergic respiratory diseases caused by this species and for the self-management of disease in allergic subjects.

Microplastics in surface seawater of Kongsfjorden, Svalbard, Arctic

Microplastics have now become an emerging contaminant with high concern in the Arctic and Sub-Arctic Region. Here, the Kongsfjorden system in the Arctic has been investigated for abundance, distribution, and characteristic of microplastics in surface seawater. Eighteen samples were collected using an in-situ filtration sampling method, and then analyzed by Fourier-transform infrared spectroscopy. The average abundance of microplastics in surface seawater was 3.6 items m−3, with an abundance range of 0.0—10.0 items m−3. The highest abundance of microplastics was located adjacent to the eddy in Kongsfjorden, where a microplastic accumulation zone might have formed. Microplastics transported by ocean currents and those from local discharges might converge in this zone. Two sampling stations were set up at the wastewater treatment plant outfall, which showed an abundance range of 4.0—6.0 items m−3, slightly higher than the average abundance. Of the six polymer types identified, rayon, polyester and polyamide were the most common composition. Proportions in fiber form in surface water was 84.6 %, and blue (28.2 %) and transparent (25.6 %) were predominant colors. Most microplastics (>90.0 %) were less than 1 mm in the longest dimension. This study provided important baseline data as well as a practical microplastic sampling method for polar marine environments.

Seasonal Variations in Physico- chemical Parameters of the Sediment of Thengapatnam Estuary, South-coastal Region of India

The tremendous biodiversity and ecological processes that depend on freshwater and marine environments are essential to human survival. The physicochemical parameters in both surface waters and sediments are important to understand estuarine dynamics. The present study was carried out to determine how the seasonal variation will affect the physicochemical parameters of sediments of five stations in Thengapatnam estuary. Sediment samples were collected for a period of one year from June 2014-May 2015 from five different sampling stations. The parameters such as pH, temperature, Nitrogen, Phosphorous, Potassium, Copper, Zinc, Iron and Manganese were analysed using standard procedures. The result expose that, soil sediment have high amount of potassium in all five stations. Sediment temperature varied from 25.7- 30.1°C. Hydrogen ion concentration ranged between 6.9 to 8.3, concentrations of nutrients viz. nitrate (2.4 – 6.4 mg/100g), phosphate (1.5 - 15.25 mg/100g) potassium (138 – 560 ppm) and concentration of metals like iron, zinc and manganese were found to be higher during monsoon season and lower during premonsoon seasons The overall findings highlight the need for a scientific solution to reduce the use of harmful chemicals and heavy metal contamination from the river system in order to preserve the biodiversity of freshwater and marine ecosystems.

Insight into the diet of early stages of mesopelagic fishes in the Indian Ocean using DNA metabarcoding

Despite playing a critical role in oligotrophic ocean food webs, relatively little is known about the diet of mesopelagic fishes in the Indian Ocean. These fishes are an abundant component of the micronekton assemblages and are a major energy- and nutrient-rich food source, linking the plankton which they feed on to marine predators at higher trophic levels. DNA metabarcoding, a molecular method to identify species from mixed assemblages, has not been commonly used in studies of mesopelagic fish diet, but using it to analyse gut contents can greatly improve the understanding of mesopelagic fish feeding ecology. In this study, we apply DNA metabarcoding (18S rRNA and COI) to gut contents from Stomiiformes and Myctophiformes species from 20 sampling stations covering 30 ˚ of latitude on the 110 ˚ E meridian in the Indian Ocean. In total, 174 fish specimens from 13 genera were examined. Differences in the gut contents among fish families, geographic areas and fish stages were identified. Specimens within the family Myctophidae had the most diverse diet, more so in the northern sampling stations than the south. Gonostomatidae had the least diverse diet. Overall, the most frequently identified prey items from the gut contents were calanoid copepods and halocyprid ostracods. The proportion of halocyprids were also identified to be significantly different among Myctophidae larvae and juvenile specimens, which is a potential ontogenic shift in diet towards a higher ostracod contribution in juveniles as mouth gape increases. In comparison with other plankton abundance data, Copepoda were the most abundant plankton in the gut contents of all fishes sampled throughout the latitudinal gradient, allowing them to be a potential food resource through the region. There are indications that other less abundant plankton, such as like Ostracoda and Malacostraca, may be preferentially targeted by some mesopelagic fish families.

GIS-Based Mapping of the Water Quality and Geochemical Assessment of the Ionic Behavior in the Groundwater Aquifers of Middle Ganga Basin, Patna, India

The study implemented Geographic Information System (GIS) techniques and multivariate hydrogeochemical analysis to evaluate the spatial-temporal and seasonal variation in the groundwater quality of Patna, India. For this purpose, sixty groundwater samples were collected and analyzed for major anions and cations during the pre-monsoon, monsoon, and post-monsoon seasons of 2019-2020. The physicochemical parameters such as pH, EC (Electrical Conductivity), TDS (Total Dissolved Solids), TH (Total Hardness), Ca2+, Mg2+, Na+, K+, HCO3-, Cl-, SO42- were considered to evaluate the water quality index. The result revealed degradation in groundwater quality from pre-monsoon (49.21) to post-monsoon (74.48). EC, TDS, TH, Mg2+, Na+, Ca2+, K+, and HCO3- ions were found accountable for high WQI values at various sampling sites during different seasons. Spatial maps showed that 45 % of the sampling stations exhibited poor quality in all three seasons, where the eastern part of the studied region was revealed to be the most affected area. The application of multivariate statistical methods and hydrogeochemical investigation has clearly defined the dominant role of the weathering process, and reverse ion exchange mechanism in controlling the aquifer’s ionic chemistry. Moreover, poor seepage system, and waste leachate from the surface have been found as the main cause of high levels of Na+, K+, and Cl- in the eastern part of Patna.

Occurrence, distribution and risk assessment of phthalate esters in dust deposited in the outdoor environment of Yazd industrial park using Monte Carlo simulation

In this study, the distribution of eight phthalate esters (PAEs), namely (dimethyl phthalate (DMP), diethyl phthalate (DEP), di-n-butyl phthalate (DBP), butyl benzyl phthalate (BBP), bis (2-ethylhexyl) phthalate (DEHP), and di-n-octyl phthalate (DnOP)) were examined across fifteen sampling stations in Yazd industrial Park. All the PAEs in dust deposited in the outdoor environment were analyzed using a Gas-mass chromatography (GC-MS/MS) device. Both probabilistic and deterministic approaches were utilized to assess the non-carcinogenic and carcinogenic health risks for adult occupational population groups. These risks were associated with three exposure pathways: inhalation, ingestion, and dermal exposure to six phthalates in the dust samples. The findings revealed, among the fifteen sampling stations, highest and lowest concentrations of the PAEs in dust deposited in the outdoor environment were observed in S8 and S6, with BEHP (326.21 ± 4.35) μg/g and DMP (0.00 ± 0.02) μg/g, respectively. The total hazard index (HI) values were below one in all samples, indicating that the combined non-carcinogenic health risk from exposure to phthalates via inhalation, ingestion, and dermal pathways is within acceptable levels in each studied area. The total cancer risk (CR) values for BBP across all exposure routes were consistently low, with magnitudes ranging from 10- x 10−15to 10 x 10−11. The order of cancer risk from phthalate exposure in outdoor environments was ingestion > dermal > inhalation. The sensitivity analysis (SA) results indicated that the influential parameters in the carcinogenic risk in adult occupational population groups were concentration for inhalation and dermal pathways, as well as ingestion rate for the ingestion pathway. The result of this study provides new insight in to PAEs pollution and risk assessments related to the dust deposited in the outdoor environment of industrial Park. Furthermore, this finding is beneficial to the controlling the exposure and promoting steps to reduce PAEs contamination and manage health in the industrial area.

Geospatial Mapping and Health Status of Some Important Ornamental Fish Habitats of Upper Assam, India

To conserve and manage water resources, it is crucial to create a record of water bodies and their catchments, which can be accomplished through digitized maps. The research focused on five rivers - River Dibru, River Sessa, River Burhidihing, River Brahmaputra, as well as two wetlands of Upper Assam - Maguri Beel, and Mer Beel. These water bodies were chosen based on their abundant fishery resources. Each selected water body was divided into three segments, and one sampling station from each segment was selected for monitoring water quality and recording fish species. The distribution of the catchment area was analyzed in the form of raster maps and geomorphology maps. Based on fish landings, the water bodies were identified and classified, and fish samples were collected through regular field surveys. Over the period from January 2021 to December 2022, eleven physicochemical parameters of the selected water bodies were recorded seasonally to assess the health status of each water bodies. Similarly, the health status and growth coefficient of each fish specimen was done. Water parameters were mostly within the standard limits and demonstrated only a narrow range of seasonal variation. In the studied water bodies, 49 ornamental fish species representing 32 genera under 18 families and 8 orders were found. Among the water bodies, River Dibru had the highest number of ornamental fish species at 46. The order Cypriniformes was dominant in all the studied sites.

Hindcasting Estuarine Bottom Salinity Using Observing Systems Data and Nonlinear Regression, as Applied to Oysters in Delaware Bay

Salinity is a major environmental factor that influences the population dynamics of fish and shellfish along coasts and estuaries, yet empirical methods for hindcasting salinity at specific sampling stations are not widely available. The specific aim of this research was to predict the salinity experienced by juvenile and adult oysters (Crassostrea virginica) collected at sampling stations in Delaware Bay. To do so, empirical relationships were created to predict salinity at five oyster bed stations using observing systems data. These relationships were then applied to construct indices of salinity exposure over an oyster’s lifetime. Three independent salinity data sources were used in conjunction with observing systems data to construct and validate the predictive relationships. The root mean square error (RMSE) of the models ranged from 0.5 to 1.6 psu when model predictions were compared with the three independent data sets. Results demonstrated that data from an observing system near the head of Delaware Bay could be used to predict salinity within ± 2 psu at oyster bed stations as far down-estuary as 39 km. When these models were applied to estimate low salinity exposure of 2-year-old oysters via the metric of consecutive days below 5 psu, the indices suggested that there could be as much as a 42-day difference in low salinity exposure for oysters at stations just 31 km apart. The approach of using observing systems data to hindcast salinity could be applied to advance understanding of salt distribution and the effect of low salinity exposure on organisms in other estuaries, especially bottom-associated species.

Physical Characterization of Microplastic Pollutants in Groundwater

The rapid urbanization and growth of the population have led to both the ever-increasing demand for water consumption and in tandem the levels of water pollution in Malaysia. Rapid development has produced great amounts of human waste including domestic and industrial which inevitably ends up in the water resources. Contamination of microplastic (MP) pollutants in groundwater has been a huge concern nowadays since groundwater often becomes a source of drinking water. Therefore, these MP (plastic particles &lt; 5 mm) are concerned with having a negative health impact on human health through the consumption of drinking water that has been contaminated. While MPs in groundwater likely affect human health, only a handful of studies have examined the abundance and movement of MPs in groundwater. Because of that, this study was done in two different sampling stations of groundwater that were sources of drinking water. This study indicates a total of 182 microplastics were found in the sampled groundwater. Physical characterization has been done and they were divided into four categories according to their shapes. Fibers clearly prevailed in all water samples. Despite 10 different colors of the microplastics being identified, most of the MPs are comprised of transparent plastics. Moreover, polypropylene (PP) and polyethylene (PE) were found to be predominant in the water samples. This study contributes to filling the knowledge gap in the field of emerging microplastic pollution in drinking water sources specifically groundwater, which is of concern due to the potential exposure of MPs to humans.

Trend Analysis of Total Suspended Solids in Inland Waters Using the BFAST Algorithm on MOD09GA Products in Porto Primavera Reservoir – Brazil

Satellite remote sensing, particularly using the MODIS orbital platform, is crucial for large-scale lake monitoring, allowing the observation of optically active components with suitable spatial and temporal resolution for lakes with surfaces greater than 40 hectares. In this context, the objective of this article was to propose a methodology that improves the retrieval and monitoring of data related to Total Suspended Solids (TSS) in large lakes. The methodology employed involved defining a baseline to map the spatiotemporal dynamics of TSS using MODIS band 1, which generates information in the infrared spectrum and is centered at 645 nm. The method was tested in the Porto Primavera Reservoir (PPR), Brazil. To validate the model, two fieldwork campaigns were conducted in the PPR, where radiometric and water quality data were collected. An empirical model was fitted between reflectance and the TSS data set (r = 0.93, R2 = 0.85, p &lt; 0.01, n = 25). This empirical model was applied to a time series of MODIS images from May 2000 to April 2020. Using the spatial distribution maps, a time series was created from an average pixel of the sampling stations, and then this time series was analyzed to separate the trend and seasonality. The results showed that the average TSS values observed in the time series were 5.79 mg/L. The seasonality of the time series revealed that the highest concentration is recorded in the austral summer (December-February), the rainiest season. The trend component indicates that variations in TSS concentration coincide with exceptional events of increased precipitation and with a homogenization interval of the waters following the reservoir's construction.

First diatom-based assessment of Lower Hari Rud River (a transboundary system) in Afghanistan.

It is essential to determine the dominant/indicator species and their ecological preferences to develop a comprehensive bioassessment strategy for rivers. The objective of this work was to provide dependable ecological evaluation techniques for ecosystems that experience significant human-induced disruptions, with the Hari Rud River (a transboundary water resource) serving as a case study during the May (wet) and July (dry) periods of 2023. Canonical correspondence analysis revealed that electrical conductivity (EC), dissolved oxygen, ortho-phosphate (P ), and nitrate (N ) had substantial impacts on the spatial distribution of diatom species in the basin. Relatively pollution-tolerant species, including Nitzschia brevissima, N. capitellata, N. umbonata, N. palea, N. dissipata, and Navicula cryptocephala, had close relationships with EC and P , integrated with Joi Injil and Karbar streams. Of the sampling stations, especially Hari Rud River1 and Hari Rud River2, exhibited pollution-sensitive diatom species, Cymbella excisa, Achnanthidium minutissimum, Diatoma moniliformis, Cymbella affinis, and Meridion circulare. Various eco-regional diatom metrics exhibited distinct scores, indicating a range of ecological status from high to bad in the Lower Hari Rud River basin. European diatom indices revealed good ecological status for Hari Rud River 1 and 4, but poor or bad ecological statuses for Joi Injil and Karbar streams. The findings of the current study emphasize the requirements of autecological studies to understand the regional diatom compositions and their ideal survival ranges in different locations before considering using non-regional diatom indices to evaluate the ecological status of lotic systems.

Species composition and structural organization of the littoral zooplankton communities in the Oleksandrivka Reservoir (Ukraine)

Today, the issue of researching reservoirs, which are an important source of human water supply and are significantly affected by anthropogenic factors, is gaining more and more relevance. Research on the Oleksandrivka Reservoir is highly important since the safety of operation of the South-Ukrainian NPP depends on the functioning of this reservoir. The research material was samples of littoral zooplankton, which is a bioindicator of changes in the aquatic environment. During the research, both classical methods and the original method of standardizing the number and localization of zooplankton sampling stations within different types of reservoir were used. As a result of original research, the species composition and structural organization of littoral zooplankton communities in different parts of the Oleksandrivka Reservoir were analyzed for the first time. A total of 126 species of zooplankton were registered, of which 96 were observed in this reservoir for the first time. The rotifer Euchlanis dapidula was discovered for the first time in the fauna of Ukraine. The peculiarities of the formation of the faunal spectrum, trophic groups, complex of dominant species, distribution of biotopes, distribution in different parts of the reservoir, density, biomass, as well as seasonal and daily dynamics of littoral zooplankton groups were also clarified. It was established that the biomass of phytoplankton has a statistically significant effect on the density and biomass of zooplankton.

Some Physicochemical Parameters and Heavy Metals Concentration in Water and Organs of Oreochromis niloticus (Linnaeus, 1758) in Ajiwa Reservoir, Katsina State

Ajiwa Reservoir serves as a vital drinking water source and protein source to the nearby communities and Katsina metropolitan. Fishes are a great dependable source of protein and assessment to determine their safety or otherwise is very crucial. In this work, four vital organs (gills, gonads, liver and muscles) collected from Ajiwa reservoir in Katsina state were analyzed for some heavy metals (Cobalt, Copper, Manganese, Nickel, and Lead). This preliminary investigation was carried out between September to December (2023) to expose additional information on the concentration of heavy metals in both water and tissues of Oreochromis niloticus, four sampling stations were randomly chosen for the survey along the bank of the reservoir. Samples were collected fortnightly throughout the research. The mean physicochemical parameters of the Ajiwa reservoir were pH (7.10±0.48), Temperature (22.93±4.02), Transparency (12.61±2.46), Conductivity (113.97±10.63), DO (6.78±1.09), and BOD (3.52±0.88). Atomic Absorption Spectrometry (AAS) instrument was used to determine the heavy metal concentrations in the samples and their levels compared with the World Health Organization (WHO, 2020) specified maximum levels. The results showed the concentration of heavy metals in the water to be (mg/L) Co (0.45±0.23), Cu (0.05±0.03), Mn (0.06±0.09), Ni (0.10±0.07), and Pb (0.40±0.18). Co, Mn, Ni and Pb were higher than the set standards limits of WHO (2023). The results indicate that the concentration of heavy metals in the analyzed fish tissues are in (mg/L) Co (1.03±0.16), Cu (0.13±0.05), Mn (0.10±0.19), Ni (0.18±0.22) and Pb (0.21±0.66). The concentration of Co, Ni and Pb were above the set standards of WHO (2020). Co, Mn and Pb concentrations mostly in the liver and gills were higher than the maximum permissible limit recommended by standard bodies.

Distribution and Genesis of Aliphatic Hydrocarbons in Bottom Sediments of Coastal Water Areas of the Crimea (the Black and Azov Seas)

The aim of the article is to assess the level of aliphatic hydrocarbon (AHC) contamination in bottom sediments of the Azov–Black Sea coast of the Crimea, as well as to identify potential sources of its formation. Bottom sediment samples obtained from 19 stations during the research cruise of the R/V “Professor Vodyanitsky” (June 2020) were used as the material for this investigation. Sampling stations were located along the coast of the Crimean Peninsula and the Caucasus coastlines (the Black and Azov Seas). N-hexane extracts of sediments were studied by gas chromatography to determine the AHC amount and composition. It was established that AHC concentrations in the study area varied from 1.30 to 127.8 mg/100 g. Generally, bottom sediments of the Black and Azov Seas were characterized by low AHC contents, while increased AHC contents were found in the outer harbor of Sevastopol and Yalta regions. To identify potential hydrocarbon sources, various hydrocarbon markers were used. In most of the study areas, n-alkane composition was determined by similar sources of inputs and organic compound transformation. At the same time, oil pollution linked with use of fuel was recorded almost everywhere.

Response of benthic assemblages to heavy metal contamination from shipbreaking operations in a tropical coastal area

The response of macrobenthic communities to both environmental and anthropogenic pressures serves as a valuable indicator of ecosystem integrity. This study aimed to unravel the benthic community structure, examine the heavy metal contamination status, and explore the response of the microbenthic community to heavy metals in a tropical shipbreaking region. For this, sediment and benthos samples were taken from different sampling stations of the shipbreaking area and the non-shipbreaking sites. The results showed the benthic community consisted of 23 taxa, including Polychaeta, Oligochaeta, Amphipoda, Decapoda, Gastropoda, Bivalvia, and Priapulida, with polychaetes being the predominant group. The benthic community and diversity values were significantly varied between the two sampling sites (p <0.05). Taxa richness was lower in the shipbreaking area, primarily characterized by the dominance of opportunistic benthic groups, particularly Capitella sp. The concentrations of heavy metals (µg. g−1) in the sediment varied within the following ranges: 35.54–258.021 for Zn, 4.84–132.08 for Pb, 22.82–75.25 for Cu, 198.74–764.16 for Mn, 14.57–42.13 for Cr, 4.03–42.23 for Ni, and 3.82–14.85 for Co. Based on concentration levels, Zn, Pb, and Cu were identified as major contaminants with moderate to high potential for adverse effects, particularly evident in the shipbreaking area compared to non-shipbreaking areas. Pollution indices, including enrichment factors and contamination factors, also highlighted contamination by Zn, Pb, and Cu. Among the benthic taxa, Polychaeta demonstrated a high degree of tolerance to elevated concentrations of these heavy metals. Amphipoda density was significantly negatively correlated with Zn, Pb, and Cu concentrations, with significant coefficients of determination (r2= 0.38, p <0.10; r2= 0.64, p <0.01 and r2 = 0.63, p <0.01, respectively). Multivariate analyses (cluster analyses, MDS and CCA) demonstrated both positive and negative relationships among heavy metals and benthic groups. Canonical Correspondence Analysis (CCA) showed the benthic community was negatively correlated with Zn, Pb, and Cu. This finding provided critical insights into the ecological health of aquatic ecosystems, aiding in the development of informed conservation and management strategies.

Estimating taxonomic and functional structure along a tropical estuary: linking metabolic traits and aspects of ecosystem functioning.

Microbial life forms are among the most ubiquitous on Earth, yet many remain understudied in Caribbean estuaries. We report on the prokaryote community composition of the Urabá Estuary in the Colombian Caribbean using 16S rRNA gene-transcript sequencing. We also assessed potential functional diversity through 38 metabolic traits inferred from 16S rRNA gene data. Water samples were collected from six sampling stations at two depths with contrasting light-penetration conditions along an approximately 100 km transect in the Gulf of Urabá in December 2019. Non-metric multidimensional scaling analysis grouped the samples into two distinct clusters along the transect and between depths. The primary variables influencing the prokaryote community composition were the sampling station, depth, salinity, and dissolved oxygen levels. Twenty percent of genera (i.e., 58 out 285) account for 95% of the differences between groups along the transect and among depths. All of the 38 metabolic traits studied showed some significant relationship with the tested environmental variables, especially salinity and except with temperature. Another non-metric multidimensional scaling analysis, based on community-weighted mean of traits, also grouped the samples in two clusters along the transect and over depth. Biodiversity facets, such as richness, evenness, and redundancy, indicated that environmental variations-stemming from river discharges-introduce an imbalance in functional diversity between surface prokaryote communities closer to the estuary's head and bottom communities closer to the ocean. Our research broadens the use of 16S rRNA gene transcripts beyond mere taxonomic assignments, furthering the field of trait-based prokaryote community ecology in transitional aquatic ecosystems.IMPORTANCEThe resilience of a dynamic ecosystem is directly tied to the ability of its microbes to navigate environmental gradients. This study delves into the changes in prokaryote community composition and functional diversity within the Urabá Estuary (Colombian Caribbean) for the first time. We integrate data from 16S rRNA gene transcripts (taxonomic and functional) with environmental variability to gain an understanding of this under-researched ecosystem using a multi-faceted macroecological framework. We found that significant shifts in prokaryote composition and in primary changes in functional diversity were influenced by physical-chemical fluctuations across the estuary's environmental gradient. Furthermore, we identified a potential disparity in functional diversity. Near-surface communities closer to the estuary's head exhibited differences compared to deeper communities situated farther away. Our research serves as a roadmap for posing new inquiries about the potential functional diversity of prokaryote communities in highly dynamic ecosystems, pushing forward the domain of multi-trait-based prokaryote community ecology.

Seabed Geoacoustic Analysis Using Scientific Single Beam Echosounder

Graphical Abstract Highlight Research Geoacoustic quantification. Sediment identification. Sediment classification. Geoacoustic characteristic. Sediment type spatial distribution in Lancang Island. AbstractHydroacoustic technology was able to quantify the seabed substrate and can be estimated accurately and near real time on the acoustic characters of each substrate. The purpose of the research was to identify the geoacoustic characteristics and spatial mapping of the seabed substrate in Lancang Island. Acoustic data was acquired using a Simrad EK-15 Single Beam Echosounder instrument operating at 200 kHz. Sediment samples were taken using an Ekman grab, which will be used to validate the acoustic data. The results of this study indicated that the acoustic backscatter values of the seabed substrate based on the surface backscattering strength value and sediment particle size at fourteen sampling stations are -28.03 decibels to -20.02 decibels divided into 9 sediment type groups, namely medium and very coarse sand mixture; medium sand; medium, fine and coarse sand mixture; medium and fine sand mixture; fine and medium sand mixture; medium and very fine sand mixture; very fine and medium sand mixture; fine and very fine sand mixture; and fine sand. The accuracy level of k-Nearest Neighbour and Random Forest computational used has very good accuracy of 98.21 % and 96.43 % and Naevi Bayes has a lower accuracy of 58.93 %. The identified geoacoustic characteristics included the mean grain size, sound speed, density, acoustic impedance, and reflection coefficient. Faster, more effective, and efficient computational processes with high accuracy make k-Nearest Neighbour and Random Forest models the best alternative to be used as geoacoustic computational models of seafloor substrates.

Insights into the physiology, biochemistry and ecological significance of the red seaweed Tricleocarpa fragilis in the Andaman Sea

The present study focused on the physiological and biochemical aspects of Tricleocarpa fragilis, red seaweed belonging to the phylum Rhodophyta, along the South Andaman coast, with particular attention given to its symbiotic relationships with associated flora and fauna. The physicochemical parameters of the seawater at the sampling station, such as its temperature, pH, and salinity, were meticulously analyzed to determine the optimal harvesting period for T. fragilis. Seaweeds attach to rocks, dead corals, and shells in shallow areas exposed to moderate wave action because of its habitat preferences. Temporal variations in biomass production were estimated, revealing the highest peak in March, which was correlated with optimal seawater conditions, including a temperature of 34 ± 1.1 °C, a pH of 8 ± 0.1, and a salinity of 32 ± 0.8 psu. GC‒MS analysis revealed n-hexadecanoic acid as the dominant compound among the 36 peaks, with major bioactive compounds identified as fatty acids, diterpenes, phenolic compounds, and hydrocarbons. This research not only enhances our understanding of ecological dynamics but also provides valuable insights into the intricate biochemical processes of T. fragilis. The established antimicrobial potential and characterization of bioactive compounds from T. fragilis lay a foundation for possible applications in the pharmaceutical industry and other industries.