Microplastic pollution in high-altitude Nainital lake, Uttarakhand, India.

Microplastics (MPs) contamination has been reported in all environmental compartments, but very limited information is available at higher-altitude lakes. Nainital Lake, located at a high altitude in the Indian Himalayas, has various ecosystem services and is the major source of water for Nainital town, but the MP abundance is still unknown. This study presents the first evidence of the abundance and distribution of MP in Nainital Lake. Surface water and sediment samples were analysed from 16 different sites in and around the catchment area of Nainital Lake. The MP were observed in all the samples, and their abundance in surface water was 8.6-56.0 particles L-1 in the lake and 2.4-88.0 particles L-1 in hotspot sites. In the surface sediment, MP abundance ranged from 0.4-10.6 particles g-1, while in the hotspot sediment, the mean abundance was 0.6 ± 0.5 particles g-1. Fibers were the dominant MP, while 0.02-1 mm were the predominant size of MP particles. The results of chemical characterization showed the presence of six polymers, among which high-density polyethylene was the most abundant. The Polymer Hazard Index assessment classified the identified polymers as low-to high-risk categories, with a higher abundance of low- (polypropylene) and medium- (polyethylene)-risk polymers. Tourist activities and run-off catchments can be considered the major sources of MP, which can affect the ecosystem. Minimal concentrations of MP were observed in the tube well and drinking water, which depicts the direct risks to humans and, thus, the need for remedial measures to prevent MP contamination in drinking water. This study improves the knowledge of MP contamination in the higher-altitude freshwater lake, which can be the major pathway for the transport of MP to the rivers, and also emphasizes the need for waste management in Nainital town.

Interaction of climate change and marine pollution in Southern India: Implications for coastal zone management practices and policies.

Climate change and marine litter are inextricably linked, and their interaction manifests differently depending on the specific environmental and biological characteristics, and other human activities taking place. The negative impacts resulting from those synergistic interactions are threatening coastal and marine ecosystems and the many goods and services they provide. This is particularly pervasive in the coastal zone of the Indian subcontinent. India is already experiencing severe climate change impacts, which are projected to worsen in the future. At the same time, the country is gripped by a litter crisis that is overwhelming authorities and communities and hindering the country's sustainable development goals. The coastal environment and communities of the southern states of Kerala and Tamil Nadu are particularly vulnerable to the impacts of climate change. While these state governments and authorities are stepping up efforts to improve the management of their coastal zones, the scale and severity of these issues are mounting. Here we review the combined effects of climate change and marine litter pollution in Southern India, focusing on the Gulf of Mannar Reserve in Tamil Nadu and the Malabar Coast in Kerala. Finally, we discuss effective management options that could help improve resilience and sustainability.

Distribution and dynamics of particulate organic matter in Indian mangroves during dry period.

The distribution and possible sources of particulate organic carbon (POC) and particulate nitrogen (PN) in seven mangroves ecosystems along the east and west coast of India were examined, to understand their contribution to coastal biogeochemistry. Suspended particulate matter (SPM) concentration in mangrove waters were about ~ 1.6-fold higher in west coast (Gulf of Kachchh (GOK), Mandovi-Zuari (MA-ZU) and Karwar-Kumta (KR-KU)], whereas the mean POC content in SPM along east coast [Sundarbans (SUN), Bhitarkanika (BHK), Coringa (COR) and Pichavaram-Muthupet (PI-MU)] was nearly two times higher than the west coast (1.97 ± 0.91% and 1.06 ± 0.29%), respectively. The results indicated that the influence of the land-based contaminants on the water quality parameters (dissolved oxygen, pH, salinity, nutrients and chlorophyll-a, etc.), which primarily regulated the distribution and transformation of organic carbon in these mangrove waters. Among the studied systems, an extremely high DOC/POC ratio (5.72 ± 1.64) with low pH and DO in COR waters clearly indicated the labile nature of the organic matter influenced by anthropogenic stress. Strong correlation between POC and PN indicated a similar origin in particulate organic matter. The ratios of POC/PN and POC/Chl-a showed significant spatial variation ranging from 5.5 to 18.7 and 126 to 1057, respectively. The results indicated that significant fraction of in-situ primary production contributed to particulate organic matter (POM) pool in all Indian mangrove waters except the GOK and the SUN waters, where sediment resuspension and mangrove derived organic matter were the dominant POM sources.

Biological evaluation of gallic acid and quercetin derived from Ceriops tagal: insights from extensive in vitro and in silico studies.

Gallic acid (PubChem CID: 370) and quercetin (PubChem CID: 5280343) are major phenolic compounds in many mangrove plants that have been related to health cure. In the present study, the active fractions namely gallic acid (1) and quercetin (2) were isolated from the methanolic extract of leaves of Ceriops tagal in a Tropical mangrove ecosystem of Andaman and Nicobar Island (ANI), India. The chemical structures were determined by spectroscopic analysis: Fourier-Transform Infrared spectroscopy (FT-IR), 1H, 13C Nuclear Magnetic Resonance (NMR) spectroscopy, and High-resolution mass spectrometry (HRMS). The anticancer activity of isolated compounds (1) and (2) were evaluated by in vitro assays against two human cancer cell lines namely, HeLa (Cervical) and MDA-MB231 (Breast) cancer cells revealed that IC50 values of gallic acid (HeLa: 4.179197 ± 0.45 µg/ml; MDA-MB231: 80.0427 ± 0.19 µg/ml at 24 h) and quercetin (HeLa: 99.914 ± 0.18 µg/ml; MDA-MB231: 18.288382 ± 0.12 µg/ml at 24 h), respectively. Antioxidant properties of gallic acid (1) and quercetin (2) are found to be IC50 value of 0.77 ± 0.41 µg/ml and 1.897 ± 0.81 µg/ml, respectively. Molecular docking results explained that gallic acid (1) and quercetin (2) showed estimated binding free energy (ΔG) of -5.4 and -6.9 kcal/mol towards drug target Bcl-B protein, respectively. The estimated inhibition constant (Ki) for these two molecules are 110 and 8.75 µM, respectively. The MD simulation additionally supported that quercetin molecule is significantly improved the structural stability of Bcl-B protein. The present study provides key insights about the importance of polyphenols, and thus leads to open the therapeutic route for anti-cancer drug discovery process.Communicated by Ramaswamy H. Sarma.

Identifying the natural compound Catechin from tropical mangrove plants as a potential lead candidate against 3CLpro from SARS-CoV-2: An integrated in silico approach.

SARS-CoV-2, a member of beta coronaviruses, is a single-stranded, positive-sense RNA virus responsible for the COVID-19 pandemic. With global fatalities of the pandemic exceeding 4.57 million, it becomes crucial to identify effective therapeutics against the virus. A protease, 3CLpro, is responsible for the proteolysis of viral polypeptides into functional proteins, which is essential for viral pathogenesis. This indispensable activity of 3CLpro makes it an attractive target for inhibition studies. The current study aimed to identify potential lead molecules against 3CLpro of SARS-CoV-2 using a manually curated in-house library of antiviral compounds from mangrove plants. This study employed the structure-based virtual screening technique to evaluate an in-house library of antiviral compounds against 3CLpro of SARS-CoV-2. The library was comprised of thirty-three experimentally proven antiviral molecules extracted from different species of tropical mangrove plants. The molecules in the library were virtually screened using AutoDock Vina, and subsequently, the top five promising 3CLpro-ligand complexes along with 3CLpro-N3 (control molecule) complex were subjected to MD simulations to comprehend their dynamic behaviour and structural stabilities. Finally, the MM/PBSA approach was used to calculate the binding free energies of 3CLpro complexes. Among all the studied compounds, Catechin achieved the most significant binding free energy (-40.3 ± 3.1 kcal/mol), and was closest to the control molecule (-42.8 ± 5.1 kcal/mol), and its complex with 3CLpro exhibited the highest structural stability. Through extensive computational investigations, we propose Catechin as a potential therapeutic agent against SARS-CoV-2. Communicated by Ramaswamy H. Sarma.

Environmental DNA reveals aquatic biodiversity of an urban backwater area, southeast coast of India.

Strong conservation management needs comprehensive data on biodiversity. Rapid methods that document aquatic biodiversity or assess the health condition of an ecosystem remain scarce. Herein, we have performed a metagenomics study on environmental DNA (eDNA) collected from an urban backwater area - Muttukadu, located in the southeast coast of India. Shotgun metagenomics approach using Illumina®NextSeq500 sequencing yielded 88.4 million raw reads. The processed data was assigned as 80% prokaryotes, 0.4% eukaryotes, ~2% viruses, and ~17% remain unknown. This approach has the potential to identify small micro-eukaryote, unseen species from both estuarine and marine environments. We have identified 156 eukaryote organisms represented from 21 phyla and 112 families, including those that are of conservational significance and ecological importance. Furthermore, our data also demonstrated the presence of pathogenic microorganisms due to sewage mixing with the backwaters. Given its sensitivity, we suggest this approach for an initial assessment of biodiversity structure in an ecosystem for the biomonitoring program.

Assessment of bioavailable nitrogen and phosphorus content in the sediments of Indian mangroves.

Efficient nutrient cycling and adequate sediment bioavailable nutrient supply are considered to be the two most important factors regulating the high productivity and subsequent carbon sequestration by mangrove ecosystems. We assessed spatial variability and the possible regulating factors of sediment bioavailable nutrients (nitrogen (N) and phosphorus (P)) and surface water-dissolved nutrients (N, P and silicate (Si)) in the five ecologically important mangrove ecosystems along the east and west coast of India during dry season. Higher bioavailable nitrogen concentrations in the sediments were recorded in Coringa mangroves (36.27 ± 14.7 µg g-1) and Bhitarkanika (18.54 ± 5.9 µg g-1) mangroves in the east coast followed by Karnataka (15.51 ± 8.26 µg g-1), Goa, (10.18 ± 9.96 µg g-1) and Kerala (6.36 ± 5.05 µg g-1) mangroves in the west coast. The dissolved inorganic nutrients in the mangrove waters ranged between 5.1 and 220.9 µmol l-1 for N and 0.07 and 3.9 µmol l-1 for P. These results indicated that terrestrial inputs, in situ remineralization and prevalent anoxic conditions regulated sediment nutrient content in these ecosystems, whereas the higher ammonium in the sediments was attributed to the greater nutrient adsorption by finer particles. The stoichiometry of the bioavailable nutrients (N, P) in the mangrove sediments deviated drastically from the Redfield ratio, and strong P limitation was recorded in most of the ecosystems. The results highlighted the potential role of sediment particle size and physiochemical (salinity and pH) properties in regulating bioavailable nutrient dynamics in mangrove sediments.

First record of the heart urchin Metalia persica (Mortensen, 1940) (Spatangoida: Brissidae) from the Chennai coast, India.

The irregular urchin, Metalia persica (Mortensen, 1940), a heart urchin of the family Brissidae, is reported for the first time from the southeastern coast of India. A single specimen was collected from fishing by-catch at Chinna Neelankarai (12º 56' 29.7" N, 80º 15' 36.6" E),  Chennai on April 5, 2018. Metalia persica was previously recorded only from the Persian Gulf (Arabian Gulf). This study records Metalia persica for the first time from Indian waters, in the Bay of Bengal, and elucidates features of the anal fasciole.

Seagrass and macrophyte mediated CO2 and CH4 dynamics in shallow coastal waters.

Seagrass meadows are among the most important coastal/ marine ecosystems for long-term carbon storage and conditioning of coastal waters. A combined air-water flux of CO2 and CH4 from the seagrass meadows was studied for the first time from Asia's largest brackish-water lagoon, Chilika, India. Ecosystem-based comparisons were carried out during two hydrologically different conditions of dry and wet seasons in the seagrass dominated southern sector (SS); macrophyte-dominated northern sector (NS); the largely un-vegetated central sector (CS) and the tidally active outer channel (OC) of the lagoon. The mean fluxes of CO2 from SS, NS, CS and OC were 9.8, 146.6, 48.4 and 33.0mM m-2d-1, and that of CH4 were 0.12, 0.11, 0.05 and 0.07mM m-2d-1, respectively. The net emissions (in terms of CO2 equivalents), considering the global warming potential of CO2 (GWP: 1) and CH4 (GWP: 28) from seagrass meadows were over 14 times lower compared to the macrophyte-dominated sector of the lagoon. Contrasting emissivity characteristics of CO2 and CH4 were observed between macrophytes and seagrass, with the former being a persistent source of CO2. It is inferred that although seagrass meadows act as a weak source of CH4, they could be effective sinks of CO2 if land-based pollution sources are minimized.

An updated checklist of Echinoderms from Indian waters.

Species checklists enlist the species available within the defined geographical region and thus serve as essential input for developing conservation and management strategies. The fields of conservation biology and ecology confront the challenge of inflated biodiversity, attributed to non-recognition of taxonomic inconsistencies such as synonyms, alternate representation, emendations etc. Critical review of the checklists and distributional records of Phylum Echinodermata from Indian waters and subsequent validation of species names with World Register of Marine Species (WoRMS) database, revealed that the current literature included 236 incorrect entries comprising of 162 synonyms, 15 emendations, 5 nomina dubia, 1 nomen nudum, 40 species under alternate representation, 9 species with author misnomer, 1 subspecies and 1 unaccepted. The 226 species found to be mixed with valid names and a revised checklist was prepared. The revised and updated checklist holds 741 species of echinoderms comprising of 182 asteroids (24.56%), 70 crinoids (9.45%), 138 echinoids (18.62%), 179 holothuroids (24.16%) and 172 ophiuroids (23.21%), placed under 28 orders and 107 families. This paper discusses the cause for taxonomic inflation and argues that such taxonomic inconsistencies alter our interpretations of a species including its inaccurate distribution and, could possibly impede the country's conservation and management efforts.

Seagrass metabolism and carbon dynamics in a tropical coastal embayment.

Net ecosystem metabolism and subsequent changes in environmental variables were studied seasonally in the seagrass-dominated Palk Bay, located along the southeast coast of India. The results showed that although the water column was typically net heterotrophic, the ecosystem as a whole displayed autotrophic characteristics. The mean net community production from the seagrass meadows was 99.31 ± 45.13 mM C m-2 d-1, while the P/R ratio varied between 1.49 and 1.56. Oxygen produced through in situ photosynthesis, exhibited higher dependence over dissolved CO2 and available light. Apportionment of carbon stores in biomass indicated that nearly three-fourths were available belowground compared to aboveground. However, the sediment horizon accumulated nearly 40 times more carbon than live biomass. The carbon storage capacities of the sediments and seagrass biomass were comparable with the global mean for seagrass meadows. The results of this study highlight the major role of seagrass meadows in modification of seawater chemistry. Though the seagrass meadows of Palk Bay are increasingly subject to human impacts, with coupled regulatory and management efforts focused on improved water quality and habitat conservation, these key coastal ecosystems will continue to be valuable for climate change mitigation, considering their vital role in C dynamics and interactions with the overlying water column.

Megacities and large urban agglomerations in the coastal zone: interactions between atmosphere, land, and marine ecosystems.

Megacities are not only important drivers for socio-economic development but also sources of environmental challenges. Many megacities and large urban agglomerations are located in the coastal zone where land, atmosphere, and ocean meet, posing multiple environmental challenges which we consider here. The atmospheric flow around megacities is complicated by urban heat island effects and topographic flows and sea breezes and influences air pollution and human health. The outflow of polluted air over the ocean perturbs biogeochemical processes. Contaminant inputs can damage downstream coastal zone ecosystem function and resources including fisheries, induce harmful algal blooms and feedback to the atmosphere via marine emissions. The scale of influence of megacities in the coastal zone is hundreds to thousands of kilometers in the atmosphere and tens to hundreds of kilometers in the ocean. We list research needs to further our understanding of coastal megacities with the ultimate aim to improve their environmental management.