Identification of potential breeding ground of flathead grey mullet, Mugil cephalus (Linnaeus, 1758), along the Mumbai coast, India, for ecological monitoring and conservation strategies

Identifying the breeding grounds of fishes is crucial for the sustainable management of fisheries resources. The present study is aimed at identifying the potential breeding ground of Mugil cephalus along the estuary of the North Mumbai coast. A total of 1197 specimens of M. cephalus, including 546 eggs, 271 larvae, 235 juveniles, and 235 adults, were collected from four sampling stations in the Karanja estuary between January to October 2022. Water quality parameters, plankton dynamics in the estuary, and the reproductive and feeding biology of M. cephalus were also examined. The eggs, larvae, juveniles, and adults were identified using traditional morpho-meristic and DNA barcoding techniques. The results revealed a potential spawning ground of M. cephalus in the Karanja estuary. The results of reproductive biology also confirmed the occurrence of matured fishes during May-July. The abundance of eggs and larvae at the estuary's mouth and the presence of juveniles and mature individuals of M. cephalus dominantly in the Karanja estuary from May to July infer the presence of a spawning site. It is also recorded that M. cephalus spawn in higher salinity (35 ppt) and seawater temperature (33 °C) where the hatching of offspring takes place successfully. This study emphasizes the significance of DNA barcoding in guiding routine monitoring surveys and demonstrates its usefulness when combined with these techniques in identifying fish spawning grounds. The study findings will serve as baseline information to develop effective conservation and management strategies and protect the ideal spawning stock.

Seasonal distribution and abundance of microplastics in the coastal sediments of north eastern Arabian Sea

The present study reports site-specific data on the seasonal variation in microplastic abundance and characteristics in coastal sediments along the North Eastern Arabian Sea, India. The abundance of MP in coastal sediments ranged from 4400 to 15,300 items/kg dry weight (DW), with the dominance of the size ranging between 100 and 500 μm. In the studied sediment samples, fibers were the most dominant form, followed by fragments. Ten different microplastics polymers were recorded during the study with dominance of polyethylene, polyester, polyamide and all the recorded plastic items in the sediments were denser than water, except polyethylene. The mean abundance of MP in sediments was significantly higher in the monsoon season. During this season, freshwater flow increases to the sea, which brings a higher concentration of microplastics from catchment areas. For a better insight, more time-series data and research are required to assess the source of MP pollution, understand spatial-temporal variations in MP abundance and their possible hazardous impacts on marine organisms and the environment.

Microplastic pollution in coastal ecosystem off Mumbai coast, India

Microplastics (MPs) are anthropogenic pollutants which can adsorb toxic substances from surrounding water and absorb into the fish body. During the present study, MPs were observed in water, sediment, and gastrointestinal tracts of marine biota samples collected from the coastal waters of Mumbai, India. The mean abundances of MPs recorded in water samples 372 ± 143 items/liter and 9630 ± 2947 items/kg dry weight (DW) in sediment samples. The mean abundance of MPs in pelagic fish species varied from 6.74 ± 2.74 to 9.12 ± 3.57 items/individual and in the demersal species the values ranged from 5.62 ± 2.27 to 6.6 ± 2.98 items/individual. Shape-wise, four type of MPs were observed in the surface waters, sediments and all studied species, predominantly fibers, followed by fragments, pellets/beads, and films. Seven different colors of MPs (red, blue, black, translucent, brown, green, and yellow) were observed from studied samples. MPs of size below 250 μm formed the dominant size in the surface water, sediments, and biota samples except Bombay duck and Malabar sole fish. Based on Raman spectroscopy analysis, eleven types of plastic polymers identified from all studied samples. Thus, presence of MPs in studied biota indicates the transfer of MPs through interlinked food chain/web to higher trophic levels and the occurrence of MPs in the fish gut underlines the necessity of more studies on processing interventions for reducing the microplastic contamination in fish for human consumption.

Anthropogenic pressure on mangrove ecosystems: Quantification and source identification of surficial and trapped debris

The mangroves are well known for their ecological services and livelihood support to humankind. The mangrove forest is experiencing extreme pressure due to anthropogenic activities, mainly the debris pollution posing great harm to the mangrove ecosystems. The abundance, sources, and composition of surficial and trapped debris items in the six contiguous mangrove regions of Mumbai were studied by the belt-transect and quadrats method. A total number of 3526 surficial debris items (368 kg) were collected from twenty belt transects. The estimated mean surficial debris was 8.8 ± 3.4 pieces/m² with a weight of 920 ± 317 g/m². The mean trapped debris was 35 ± 10 pieces/tree and 2514 ± 758 g/tree. Plastic (62.4%) includes carry bags and food wrappers mainly. Shoreline/recreational activity-based debris (38.9%) and other items (32.7%) contributed significantly to the total debris pollution. The study provides evidence that the mangrove ecosystem acts as a natural filter and trap for coastal water debris. The trapped debris is a potential risk to the mangroves due to the barrier created on the canopy surface for the incident solar radiation utilized for photosynthesis. By conducting the cleaning programs in the mangrove vegetation stretches, the ecological disturbances to the mangrove ecosystems can be minimized. Further, the regular removal of trapped debris will complement coastal pollution management. The data generated from this study will help the policymakers and resource managers about the effective control and management of debris pollution in the mangroves region.

Adsorption-biodegradation coupled remediation process for the efficient removal of a textile dye through chemically functionalized sugarcane bagasse

Textile dye effluents have many deleterious effects; therefore, it is essential to remove before releasing into waterbodies. This study developed a two-step process for decolorization of textile dye using sugarcane bagasse (SCB). The first step of the process involved functionalization of SCB with alginic acid and applying as packing material in column and assessing its performance for adsorptive removal of Drimarene red. The designed column showed 90% removal of the dye in dye-aqueous solution whereas 80% removal in dye-house wastewater. Adsorption capacity was increased at first 10 min and then gradually decreased with time. Breakthrough point was not achieved during the 60 min of experiment. Three non-equilibrium models were applied to understand the column bed properties. In the second step, the adsorbed dye molecules in SCB were degraded using an edible fungus Pleurotus sp. to obtain a dye-free nitrogen-rich bagasse. The fungus-treated SCB showed no residual toxicity and a considerable improvement in nitrogen content (from 0.14% to 0.62%) was noticed after the study of elemental profile. New design of the column bed, the processes of the chemical functionalization of the SCB, and bioremediation of dye treated bagasse through Pleurotus sp. offer a novel solution for efficient and safe disposal of textile dyes. PRACTITIONER POINTS: Two-step process for remediation of a textile dye using an agrowaste and Pleurotus sp. Chemical functionalization of an agrowaste for enhanced dye removal. New process of adsorption-fungal degradation for safe disposal of the dyes. Novel technology for a sustainable use of the agrowaste for environmental safety.

Microplastics in shrimps: a study from the trawling grounds of north eastern part of Arabian Sea

Accumulation of microplastics (MPs) in marine organisms poses an imminent environmental threat and health risk due to the possibility of trophic transfer of accumulated MPs in ecologically important food chains. In this context, a field-level study was conducted on the fishing grounds of the north eastern part of the Arabian Sea through experimental fishing, and the gastrointestinal tracts (GT) of three different species of shrimps (n=180) were examined for the incidence of microplastics. The results showed that all shrimp caught from the fishing grounds had significant levels of MPs in the gastrointestinal tracts. A total number of 1220 microplastic items were recorded from the pooled samples, with an average of 6.78 ± 2.80 items per individual. The gastrointestinal tract showed an average number of 70.32 ± 34.67 MPs per gram of the gut material. The MPs with the size range of 100-250 μm were the most abundant form found in the shrimp species analyzed. Among the colored MP particles, black color was the most dominant (30.16%) form of MP. Fibers, fragments, pellets, beads, and films were the common morphotypes; however, fibers showed an occurrence of 39.40%, 47.39%, and 41.89% in the GTs of Metapenaeus monoceros, Parapeneopsis stylifera, and Penaeus indicus, respectively. In the present study, six types of plastic polymers were identified from the GTs of the studied samples. The findings confirm the presence of microplastics in the natural habitats of shrimps beyond the coast and indicate that shrimps caught from these coastal fishing grounds contain MPs in their gut. The findings underline the immediate scientific intervention for the microplastic reduction in the marine environment.

Incidence of microplastics in gastrointestinal tract of golden anchovy (Coilia dussumieri) from north east coast of Arabian Sea: The ecological perspective

Anthropogenic marine litters or microplastics (MPs) accumulation in marine organisms is an emerging environmental threat. In this background, the gastrointestinal tract of Coilia dussumieri (n = 150) was studied in the samples collected from the fishing grounds of the north east coast of Arabian Sea through experimental fishing. Out of the total 150 specimens collected, all showed the incidence of microplastic particulates in the guts. The average abundance of MPs was found to be 6.98 ± 2.73 items/individual whereas gastrointestinal tract recorded with an average number of 28.84 ± 10.13 MPs/g in the gut material. The dominant MPs were found in the size range of 100-250 μm and of fibers type mostly blue in color. The prevalence of MPs in Coilia dussumieri is a matter of serious concern due to its ecological consequences due to trophic transfer in the connected food chains and probable threats to the health of human beings consuming the fish.

Toxicity Evaluation of Six Textile Dyes on Growth, Metabolism and Elemental Composition (C, H, N, S) of Microalgae Spirulina platensis: The Environmental Consequences

A concentration-dependent decrease in growth rate and pigment concentration of the blue-green alga Spirulina platensis was recorded after the exposure to graded (5-40 ppm) concentration of six textile dyes. The profile of vital elements (C, H, N, S) also showed a significant variation due to dye toxicity. The algal population showed up to 50% decrease in protein content after exposure to the dyes. Among the pigments, the dye exposure resulted in > 90% decreases in phycocyanin however, total chlorophyll and carotenoids exhibited up to a 50% decrease compared to control. The findings indicate that the unregulated discharge of textile dyes will directly impact the photoautotrophic organisms leading to ecological imbalance in aquatic ecosystems. Overall observations of the report provide baseline information about the toxicity of textile dyes and giving a better insight into the little-understood mechanisms of dye toxicity.

Toxic Effects of Selected Textile Dyes on Elemental Composition, Photosynthetic Pigments, Protein Content and Growth of a Freshwater Chlorophycean Alga Chlorella vulgaris

Toxicity of three textile dyes-Optilan yellow, Drimarene blue and Lanasyn brown, was evaluated in a green alga Chlorella vulgaris. The unialgal populations of the alga showed a concentration-dependent decrease in specific growth rate and pigments after exposure to graded concentrations of above dyes. The elemental profile (C, H, N, S) of the treated and untreated cells showed a change which was evident from a significant decrease in the quantity of elements after exposure to the dyes. The observations provide convincing evidence that the textile dyes inhibited the growth, pigment and elemental composition of the algal cells. The findings of the present investigation will contribute to gaining a better understanding of the impacts of textile dyes on ecologically important aquatic organisms.

Intertidal biodiversity and health status of Bandstand shore (Bandra), Mumbai, India

A study was carried out to assess the biodiversity status of the intertidal region of rocky shore of Bandstand (Bandra), Mumbai. Among 42 species recorded, Euchelus asper was maximum in density during December (123/m2). However, maximum biomass was recorded for Nerita oryzarum in November (146.94 g/m2). ANOVA revealed no variation in the occurrence of organisms according to transects, but the variation was recorded according to months and quadrates. Shannon and Simpson's diversity index, Margalef's richness index and Pielou's evenness index indicated different level of ecological state of the shore in different months. Dendrogram from Bray-Curtis similarity matrix and non metric Multi-Diamentional Scaling (MDS) revealed maximum closeness of occurrence between N. oryzarum and Planaxis sulcatus. Shepard diagram and abundance/biomass comparison (ABC) curve method revealed light to moderately polluted status of the shore. However, in spite of such condition, this shore is still rich in intertidal biodiversity that should be conserved.