Microplastic pollution and its ecotoxicological impact: Evidence from Vembanad Lake and zebrafish studies

The American brackish water mussel, Mytella strigata (Hanley, 1843), is an invasive species with a growing global footprint, recently recorded in the Indian coastal ecosystems. Despite its rapid spread and potential ecological impact, no genetic data are available for Indian populations. We assessed the genetic diversity and population structure of M. strigata with a 683 bp fragment of the mitochondrial cytochrome b (cyt b) gene from 71 individuals collected from six locations along the Arabian Sea and the Bay of Bengal. Sixteen haplotypes were identified. The Vembanad lake and Ennore creek populations on the Kerala/West Coast and Tamil Nadu/East Coast, respectively, had the highest haplotype and nucleotide diversity, whereas otherWest and East Coast populations had very low diversity. AMOVA indicated that 16.7% of the genetic variance occurs among populations, which contrasts with the expectation for a species with a high dispersal of planktonic larvae. The haplotype network includes both shared and population-specific haplotypes, consistent with multiple introduction events and restricted gene flow rather than range expansion from a single source. Neutrality and mismatch analyses showed no significant evidence of demographic expansion, which likely reflects the limited resolution of the short cyt b fragment. The invasion history of M. strigata in India is complex, and is characterized by independent introductions, local diversification, and constrained post-settlement dispersal.

Water pollution is a growing concern for aquatic ecosystems worldwide, with threats like plastic waste, nutrient pollution, and oil spills harming biodiversity and impacting human health, fisheries, and local economies. Traditional methods of monitoring water quality, such as ground sampling, are often limited in how frequently and widely they can collect data. Satellite imagery is a potent tool in offering broader and more consistent coverage. This review explores how Multispectral Imagery (MSI) and Synthetic Aperture Radar (SAR), including polarimetric SAR (PolSAR), are utilised to monitor harmful algal blooms (HABs) and other types of aquatic pollution. It looks at recent advancements in satellite sensor technologies, highlights the value of combining different data sources (like MSI and SAR), and discusses the growing use of artificial intelligence for analysing satellite data. Real-world examples from places like Lake Erie, Vembanad Lake in India, and Korea’s coastal waters show how satellite tools such as the Geostationary Ocean Colour Imager (GOCI) and Environmental Sample Processor (ESP) are being used to track seasonal changes in water quality and support early warning systems. While satellite monitoring still faces challenges like interference from clouds or water turbidity, continued progress in sensor design, data fusion, and policy support is helping make remote sensing a key part of managing water health.

Polycyclic aromatic hydrocarbons (PAHs) in surficial sediments of Vembanad wetland ecosystem, southwest coast of India: An integrated assessment of dissemination, source apportionment, ecological and public health implication.

Loss of soil from river basins by water is a concerning issue for India which is an agricultural country. The particular distribution of quantitated soil erosion must be obtained to propose effective soil conservation practices. Revised Universal Soil Loss Equation (RUSLE) is a tool to estimate soil erosion distribution spatially. The properties of Vembanad lake that supports large biodiversity and ecosystem is altered by the sediments of Muvattupuzha River. The river, originating from the Western Ghats drains into Vembanad lake, has undergone many changes. In this work, an attempt has been made to determine the soil erosion in the Muvattupuha River basin through the years. Annual sediment loss from the basin is obtained for three consecutive decades. Maps of soil yield, sediment delivery ratio and sediment transportation index of the basin for 2021 are also developed.

This paper represents the first report of manglicolous lichens from Central Vembanad Lake, documenting a total of 31 species belonging to 23 genera and 14 families. Among these, 13 species are identified as new distributional records to Kerala, namely Anisomeridium biforme (Schaer.) R.C. Harris, Arthonia simplicascens Nyl., Bactrospora myriadea (Fée) Egea and Torrente, Cresponea proximata (Nyl.) Egea and Torrente, Enterographa tropica Sparrius, Graphis caesiella Vain., Graphis furcata Fée, Graphis handelii Zahlbr., Graphis librata C. Knight, Graphis modesta Zahlbr., Herpothallon cinereum G. Thor, Porina tetracerae (Ach.) Müll. Arg., and Pyrenula thelomorpha Tuck. The genus Cresponea is a new generic record to Kerala.

Impact of Extreme Weather Events and Land use on Leptospira Distribution in Vembanad Lake and Associated Disease Outbreaks in Near Shore Areas

Characterization and risk assessment of microplastics accumulated in sediments and benthic molluscs in the mangrove wetlands along the south-west coast of India.

Identifying plastic pollution hotspots of Vembanad lake, Kerala, India: an integrated approach using artificial intelligence and spatial analysis

Seasonal impact of river influx on the textural characteristics of Vembanad Lake sediments, Kerala, India

This study investigates the spatio-temporal distribution of brachyuran larvae in Vembanad Lake, a tropical estuarine ecosystem. The research categorizes the estuary into three salinity zones: polyhaline, mesohaline, and oligohaline. It analyzes larval abundance in relation to key environmental factors, including temperature, salinity, pH, and dissolved oxygen. Data collected across multiple seasons showed that larval abundance peaked during the pre-monsoon season and significantly declined during the monsoon season. The mesohaline zone exhibited the highest larval abundance, indicating that it was a crucial habitat for brachyuran larval development. The findings emphasized the impactof seasonal freshwater influx during the monsoon, which transformed the estuary into a freshwater system, posing significant challenges for marine larvae. These results contributed to the understanding of larval distribution in tropical estuaries and have implications for the conservation and management of these critical habitats.

Microplastics, smaller plastic particles less than 5mm in size, pose a significant threat to the environment and human health due to their widespread presence, persistence, and potential harm to living organisms. The extensive use of plastics in human life has led to the release of substantial quantities of microplastics into the environment, resulting in widespread pollution. Microplastics are detected in diverse aquatic environments, including freshwater lakes, rivers, and marine ecosystems. Once in aquatic ecosystems, microplastics can be ingested by a wide range of aquatic organisms, including zooplankton, shellfish, and fishes. This study investigated microplastic contamination in fish (Pseudetroplus maculatus) and clam (Villorita cyprinoides) samples collected from Vembanad Lake, a Ramsar wetland in southern India. Microplastics were identified in both species using stereo zoom microscopy and Fourier-Transform Infrared Spectroscopy (FT-IR), with fibers being the dominant type. The present study highlights the occurrence of MPs in 60-80% of analysed samples with fibers being the foremost type followed by fragments. The microplastic contamination was higher in clams compared to those in fish samples. MPs such as Fibers and fragments were extracted from both the species collected from the marine influenced and riverine influenced sites of Vembanad lake. Clams are considered as ecological indicators, henceforth, the comparatively higher MP load in clams stands indicative of microplastic pollution, alarmingly disrupting the food chain and posing risks to human consumption. The urgent need for investigating the sources and pathways of microplastic pollution is emphasised by observing the similarity in the type and shapes of microplastics in both fish and clams. FTIR analysis of the samples revealed MPs with polyethylene, polypropylene, and nylon as the primary polymer types found in samples.

Conservation implications of anthropogenic disturbances on island spider diversity: A case study from the Islands of Vembanad Lake – A Ramsar site in Kerala, India

The fast degradation in bathymetry, floodwater retention capacity, and changes in salinity regimes of Vembanad-the largest wetland system in South India-and its impacts on the ecosystem services are assessed using high-resolution data sets on bathymetry and hydrography. Strengthening the outer banks of Kuttanad polders to promote paddy cultivation led to a sharp decline in its sediment (suspended) filtration potential, promoting heavy siltation and depth shrinkage of Vembanad Lake. With an area of 315 sq.km and an average depth of 8.5m (south sector)/7.87m (central sector), the lake had a retention capacity of 2617.5 MCM floodwaters in 1930 which was reduced to 384.7 MCM by 2020 (85.3% loss in retention capacity) due to area (162.5 sq.km) and depth (average 1.8m in the south sector and 2.87m in the centralsector) shrinkages. This resulted in the prolonged inundation of low-lying areas and increased incidences of flash floods. Both sectors of the lake maintain limnetic and well-mixed conditions during the monsoon whereas during non-monsoon season, the central sector turns to polyhaline/mesohaline and oligohaline conditions with stratified, partially mixed, and well-mixed salinity stratifications unlike the south sector which perennially remain limnetic and well mixed. The observed shift in salinity regimes appears to promote hypertrophic conditions, biodiversity loss, and a sharp reduction in the black clam abundance of the south sector, which before the commissioning of Thannermukkom Barrage (TMB) was a major clam ground.

Assessment of Potentially Toxic Elements Contamination in Water and Sediments from Vembanad Lake, Kerala, India: In Accounts with the Influence of its Major In Flow Rivers

Abstract Providing nursery habitats to a number of marine fish larvae that recruit after prolonged pelagic larval duration, has been identified as one of ecosystem services rendered by estuaries and protected inshore water bodies like mangroves, mudflats, swamps, and marshes. Larval fish congregation and survival are largely dependent on abiotic and biotic potential of such systems and many migrant marine fishes are adapted to them. However, occurrences of larval forms of tropical reef-associated vagrant species which are known for extensive range adaptations generate considerable academic interest. The present study provides the first report of ontogenic habitat utilization of yellow fin surgeon fish, Acanthurus xanthopterus Valenciennes 1835 in a tropical microtidal positive estuary, the Vembanad lake, South India. Surface plankton collections from the downstream part of the estuary revealed considerable proportions of acanthurid larvae in post monsoon (mean 354 ± 180 numbers/100 m3) and pre monsoon (mean 217 ± 120 numbers/100 m3) while they were absent in monsoon season. These acronurus larval forms were morphologically identified and sorted before being subjected for DNA barcoding. Mitochondrial DNA COI sequences developed from morphologically characterized acronurus larvae exhibited genetic congruency to sequence of A. xanthopterus which was evident from phylogram (bootstrap support of 100) and genetic distance data (intraspecific distance of 0%). The study indicates that Acronurus larvae of A. xanthopterus, after extensive cross-habitat dispersal, utilize the estuarine habitat to promote potential growth.

Abstract Water hyacinths have become a significant issue at the Selorejo Dam in recent years. The invasive nature of this plant and the dam’s location, surrounded by rice fields, make predicting the growth of water hyacinths at the Selorejo Dam challenging. Several studies have applied passive remote sensing satellite technology, such as Sentinel-2A/B, to observe water hyacinth growth as a substitute for in-situ observations, which are limited by time and area coverage. However, considering that rainfall in the Selorejo Dam area can reach up to 3000 mm/year, passive satellites alone may not sufficiently accommodate the need for comprehensive water hyacinth monitoring. The first successful research utilizing Sentinel-1 for monitoring water hyacinths was conducted in 2021 at Vembanad Lake, India. This research addresses the limitations of passive satellites in identifying water hyacinths due to weather conditions. It integrates passive satellite data from Sentinel-2 and active satellite data from Sentinel-1 to provide a more complete identification of water hyacinths in the Selorejo Dam. The results of this research indicate that both Sentinel-1 and Sentinel-2 can differentiate between vegetation and water areas using DPSVIm for Sentinel-1, with an overall accuracy of 0.8, and NDVI for Sentinel-2, with an overall accuracy of 0.84. These findings represent a preliminary step in the process of identifying water hyacinths in the Selorejo Dam.

Detailed knowledge of food and feeding habits is essential for the thriving culture of a fish species. The present study analyses the food and feeding habits of an indigenous bagrid catfish, Mystus gulio, from Vembanad Lake, southern Kerala’s most extensive wetland system. The main objective is to check the feasibility of utilizing Mystus gulio as a bioremediation agent for kitchen waste recycling. From the Vembanad Lake, 779 specimens were sampled from fishery catches during July 2015 to June 2017. The gut contents of 318 specimens were analyzed to summarize the species’ diet components and food preferences. Gastro somatic index, relative length and fullness of gut, feeding intensity, food components, and index of preponderance for various food items were calculated. The results showed that the fish is an omnivorous bottom feeder, feeding mainly on fish offal, plant matter, filamentous algae, prawns, and polychaetes. The results points to the possibility of considering this species a bioremediation agent for recycling kitchen waste.

Ecological impact of artificial barrage on calanoid copepods in the Vembanad Lake, Southwest Coast of India

Large scale screening and quantification of micropollutants in fish from the coastal waters of Cochin, India: Analytical method development and health risk assessment