Adyar Estuary Research Articles

Heavy metals toxicity in edible bivalves and risk exposure to humans through its consumption from Adyar Estuary, Tamilnadu, India – A baseline study

The Adyar estuary, situated at the heart of Chennai city, India, has been subjected to significant anthropogenic pollution over the past decade due to rapid urbanization and industrialization.This study endeavored to explore the bioaccumulation patterns of heavy metals within bivalve species including Perna viridis, Mercenaria mercenaria, and Lamellidens marginalis. Additionally, it aimed to assess the concentrations of heavy metals present in water samples obtained from ten discrete stations within the Adyar estuary across different seasonal periods. To better understand the dynamics of contamination, metal pollutants including Cd, B, Cu, Fe, Mn, Pb, and Zn were analyzed in the soft tissues (Gill, Kidney, and Muscle) of the bivalves using Atomic Absorption Spectrophotometer (AAS) (ELICO's SL- 176). The study also investigated the seasonal changes in biochemical constituents affecting the nutritional quality of these edible bivalves following conventional methods, and estimated the risk (both carcinogenic and non-carcinogenic) to consumers. Results showed that the biochemical constituents of Perna viridis and Mercenaria mercenaria were comparatively lower than those of the freshwater bivalve Lamellidens Marginalis (p > 0.05). Heavy metal accumulation in the mussels followed the order Mn > Zn > Cu > Pb > Fe > Cd > B. The highest uptake of metals by the bivalves occurred during the post-monsoon season, while the least uptake was observed during the monsoon season. The overall metal burden for the studied species followed the descending order M. mercenaria >P. viridis >L. marginalis. The study indicated that both carcinogenic and non-carcinogenic risks to humans from consuming these mussels were higher due to the excessive accumulation of metals Zn and Mn in all three studied bivalves.

Heavy metal pollution causes mass mortality of fish in a tropical estuary in the southwestern Bay of Bengal

A massive fish mortality of the major species, viz., Mugil cephalus, Chanos chanos, and Oreochromis mossambicus, occurred on November 27, 2017 in the Adyar estuary. This catastrophe followed a spell of heavy rainfall and flash floods. A detailed study of water quality parameters (pH, water temperature, salinity, total suspended matter, dissolved oxygen, biochemical oxygen demand, and nutrients) and heavy metals, i.e., chromium (Cr), copper (Cu), cadmium (Cd), nickel (Ni), lead (Pb), and zinc (Zn), in the sediment and fish tissues were analyzed. Pollution indices like the enrichment factor (EF), geo-accumulation index (Igeo), contamination factor (CF), pollution load index (PLI), potential ecological risk index (PERI), and biota sediment accumulation factor (BSAF) were used to measure heavy metals. The pollution indices revealed that metals were significantly enriched in the sediments. The Igeo indicates that there was moderate contamination by Cd (2.27–3.25), whereas CF shows high contamination by Cd (7.22–9.72) and moderate contamination by Pb (2.5–3.25). The PLI (1.04–1.13) suggests that heavy metal contamination of sediments has occurred. Results showed that high concentrations of the toxic metals Pb and Cd were found in the sediment as well as in fish tissues. Length and weight of fish are significantly correlated (r2 = 0.98, p < 0.05). The study revealed that the mass fish kill was due to impulsive changes in the water quality and heavy metal pollution from untreated urban sewage discharges in this region.

Status of important coastal habitats of North Tamil Nadu: Diversity, current threats and approaches for conservation

Coasts are among the most vulnerable ecosystems to the effects of climate change and the impacts of strong weather events. At the same time, they are also crucial buffers of these phenomena around the world. The current study describes the is ecological and geomorphological uniqueness of North Tamil Nadu’s coast. Five important coastal wetlands were identified in this region, namely Pulicat Lagoon, Adyar Estuary, Kovalam-Muttukadu Backwaters, Odiyur-Mudhaliyarkuppam Lagoon and Kaliveli Lake, which were survyed. The variety of habitats found here include mangroves, backwaters and creeks, estuarine areas, oyster reefs, sandy beaches and sand dunes, seagrass beds, salt marshes, and tropical dry evergreen forests. A total of 913 species from eight animals’ classes were recorded from these hotspots, of which 709 species were recorded during the study. Species recorded as bycatch have also been identified and marked so in the checklist The hotspots were assessed using a detailed criteria matrix. This study also highlights the ecological importance of these wetlands, discusses the current threats to them and explores conservation challenges and approaches from a socio-ecological and legal-policy framework.

Bioaccumulation of heavy metals in water, sediment, and tissues of major fisheries from Adyar estuary, southeast coast of India: An ecotoxicological impact of a metropolitan city

Heavy metal content in water, sediment, and tissues of six commonly used edible fishes from Adyar estuary, southeast coast of India, was assessed for metal bioaccumulation. The enrichment of metals in estuarine sediment is due to the discharge of contaminated water from the Chennai Metropolis. The enrichment factor indicated that metals such as Cr (EF=30.9) and Cu (EF=31.9) are highly enriched and fall under the very severe category. Bioaccumulation factor (BAF) revealed that the concentration of heavy metals viz. Ni, Cr, Pb, Cu, Co, Zn, Fe, and Mn in different tissues of fishes was several times higher than their concentrations in water. Moreover, high concentration of heavy metals, especially Cu and Cr was noticed in the muscle and liver tissues of the fishes which are higher than the WHO standards. Among the studied fishes, Arius parkii and Gerres oyena showed higher levels of bioaccumulation in terms of toxic metals.

Mass mortality of fish and water quality assessment in the tropical Adyar estuary, South India.

Mass mortality of fishes was reported at the Adyar estuary, South India, during November 2017. The probable reasons for fish mortality are analyzed in this paper. Critical assessments on water quality parameters including the metal concentrations, nutrients, and histology of gills and liver of fish (Mugil cephalus) isolated from the impact zone were performed. Among the metals observed, chromium showed levels (3.64 ± 0.001 mg L-1) much above the average permissible limits (0.1 mg L-1). The measured values of physico-chemical parameters in the impact zone are as follows: dissolved oxygen 4.7 ± 0.22 mg L-1, total alkalinity 132 ± 4 CaCO3 mg L-1, salinity 5.3 ± 0.3 PSU, temperature 27.8 ± 0.16 °C, nitrate, 1.66 ± 0.48 mg L-1, nitrite 0.01 ± 0.0008 mg L-1, ammonia 0.03 ± 0.001 mg L-1, phosphate 1.52 ± 0.002 mg L-1, and silicate 13.85 ± 3.1 mg L-1. The low salinity could have escalated the toxicity of the metal. In addition, histology of gills and liver showed cellular necrosis, epithelial lifting, hyperplasia, edema, mucous cell proliferation in the gills, cytoplasmic vacuolation of hepatocytes, and degeneration of liver which reveal that chromium toxicity is the most probable cause for mass mortality.

Post-restoration ecological assessment on the zooplankton dynamics of the Adyar creek and estuary

The Adyar estuary is one of the highly productive transitional zones of southeast India, situated in the southern part of Chennai city and acts as a nursery ground for several endemic flora and fauna. Since few decades, due to anthropogenic activities,indiscriminate dumping and discharge of domestic and industrial wastes and pollutants has environmentally damaged the Adyar estuary lowering many of its ecological and socio-economic attributes. In order to mitigate further environmental damage and to restore it to its earlier pristine condition, the Government and several non-Governmental agencies have undertaken ecological restoration measures to enhance its ecology and diversity. In order to evaluate the restoration process, our present study attempts to assess the diversity and abundance of zooplankton population in the restored and non-restored parts of the Adyar creek and estuary. 34 species belonging to 12 zooplankton groups from 4 stations of the Adyar creek and estuary were recorded. Copepods and rotifers were the dominant groups of zooplankton in Adyar estuary. The overall density of zooplankton from 4 stations ranged between 11.5 ± 4.39 and 23,046.67 ± 2872.68 Ind l−1. In general, Adyar estuary recorded higher zooplankton abundance than creek. The relative percentage composition was maximum for rotifers with 85.67% at Station-IV. Copepods dominated Station-I, whereas rotifers dominated the other 3 stations. Overall results indicate that the restoration activities had beneficial effect on the hydrological parameters and in increasing the diversity of zooplankton in the restored part of the Adyar creek and estuary compared to the non-restored part. Ecological indices have been used to assess the present status of the restored and non-restored parts in the Adyar creek and estuary.

Analysis and Seasonal Variation of Heavy Metals in Water and Sediment from Adyar Estuary.

Levels of heavy metal pollution in coastal environment are increasing continuously due to human activities and various studies have been conducted. The main objective of this study was to determine the selective physico-chemical properties of water, heavy metal concentration (As, Pb and Hg) and its seasonal variation in water and sediment sample collected from Adyar estuary located in Chennai, Tamilnadu state, India. The results revealed that the heavy metal concentration was higher during pre-monsoon season in water and the order of concentration Pb>As>Hg. In sediment sample the concentration of Pb and As was higher during Pre-monsoon and Hg was higher during monsoon season, the order of accumulation was Pb>As>Hg. The result shows that the physico-chemical properties were higher during monsoon, however the results were within the permissible level recommended by EPA.

Ecological restoration assessment of Adyar creek and estuary using meiofaunal communities as ecological indicators for aquatic pollution

The Adyar estuary has lost its pristine condition and is under great ecological stress due to urbanization, discharge of untreated sewage, solid waste disposal, industrial effluents and encroachments for the past two decades. As a result of degradation, many vital attributes of Adyar estuary such as clean water, faunal and floral diversity and its role as spawning and nursery ground of commercially important finfish and shellfish were lost. In order to restore the ecology of Adyar estuary, Govt.of Tamil Nadu has taken up restoration measures. The present paper deals with the diversity of meiobenthic fauna in the eco-restoration part and non-restoration part to assess the ecological status of Adyar creek and estuary with the help of their ecological indices and physicochemical parameters. In the present study, a total of thirty-nine species belonging to twenty groups of meiofauna were recorded from four stations of Adyar creek and estuary. The Number of meiofaunal species recorded in stations I, II, III and IV were 21, 22, 29 and 34, respectively. Nematodes and rotifers occurred in higher diversity than other meiofaunal groups. The overall density of meiofauna from four stations were ranged between 30±8.33 to 3264.44±378.65 Ind. /10 cm2. In general, higher density of meiofauna was recorded in estuary than the creek. Percentage composition of individual meiofauna groups ranged from 0.01% (gastrotrichs) to 54.9% (rotifers) in all the four stations. Monthly variations in the ecological indices of diversity, dominance and evenness of meiofauna of the four stations of Adyar creek and estuary showed variations in different stations, months and seasons. Results indicate restoration process of the Adyar creek enhanced the physicochemical parameters and meiofaunal diversity. These measures have helped to assess the eco-restoration of the Adyar estuary and are reflected in the favourable diversity of pollution indicator species of meiofauna. The ecological diversity indices and colonization of the restored station provide base-line data for estuarine ecosystem.

Ichthyofaunal diversity of the Adyar Wetland complex, Chennai, Tamil Nadu, southern India

Most parts of the Adyar wetland complex—Chembarampakkam Tank, Adyar River, Adyar Estuary and Adyar backwater (including a wetland rehabilitation site)-—were sampled for ichthyofaunal diversity from March 2007 to June 2011. A total of 3,732 specimens were collected and 98 taxa were identified. Twenty-two new records are reported from the estuarine reach. Forty-nine species were recorded at Chembarampakkam Tank. In the upriver stretch 42 species were recorded. In the middle stretch 25 species were encountered. In the lower stretch only five species were recorded. This lack of diversity in the lower stretch of the river can be directly linked to pollution, especially the lower reaches from Nandambakkam Bridge to Kotturpuram which exhibit anoxic conditions for most of the year. In brackish, saline and marginal waters of the estuarine reach 66 species were recorded, of which 47 occurred in the estuary proper, 34 at the point of confluence with the Bay of Bengal and 20 in the backwater which forms the creek. At the rehabilitation site, popularly referred to as the Adyar Eco Park, which is the westernmost region of the backwater, 28 species were recorded in 2011 which is a sharp increase from just four in 2007 when the area was an environmental disaster. A significant finding was Mystus cf. gulio which showed a marked morphometric difference concerning its maxillary barbels and efforts are on to discern its taxonomic status.

An assessment of angiosperm diversity of Adyar estuary, Chennai — a highly degraded estuarian ecosystem, Tamil Nadu, India

Estuaries are coastal ecosystems which are commonly known to support unique flora and fauna. The Adyar estuary is a severely damaged ecosystem due to developmental activities in the urban city of Chennai, Tamil Nadu, India. Botanical explorations were conducted in and around Adyar estuary during 2008 to 2010 to document the diversity and distribution of angiosperms. A total of 252 species and 2 varieties of angiosperms belonging to 196 genera, distributed in 64 families from 27 orders and 10 clades/groups were recorded and are arranged according to Angiosperm Phylogeny Group III Classification. It is observed that the flora of Adyar estuary also harbours a high level of non-native species. Anthropogenic threats to the estuary and its flora are identified and conservation strategies are briefly discussed.

Historical environmental pollution trend and ecological risk assessment of trace metals in marine sediments off Adyar estuary, Bay of Bengal, India

Geochemical, mineralogical and textural analyses were carried out in core sediments off Adyar estuary, Bay of Bengal, India to record the contamination trend from urban and industrial activities during the historical past. Quartz, feldspar, kaolinite, chlorite and illite were the main lithogenic and clay minerals; carbonate was the predominant biogenic mineral. Trace metals (Fe, Al, Cu, Cr, Ni, Pb and Zn) indicate more enrichment in the surface sediment layers due to recent anthropogenic activities. The mean anthropogenic factor (AF) values for trace metals in core sediments decreased in the following order: Cr > Ni > Zn > Cu > Pb. The pollution load index (PLI) values in Adyar core sediments ranged from 1 to 1.25 with an average of 1.07. Based on AF, PLI, and sediment quality guidelines values for trace metals, significant metal enrichment and ecological risk were obtained in upper-most sediment layer. Multivariate statistical methods such as correlation matrix, principal component analysis and cluster analysis were carried out to find the relationships among the texture size, metals and minerals. The pollution of Adyar estuarine sediments was started in the 1960s, responding to the rapid economic development in Chennai coastal and Adyar estuarine region in the last five decades. Despite these high concentrations in the upper layer, development and expansion of industries are still continuing. The stricter regulations for the discharge and remediation of sediments are urgent for the conservation of environments and human health.

Antimicrobial potential of Actinomycetes species isolated from marine environment

ObjectiveTo evaluate the antimicrobial activity of Actinomycetes species isolated from marine environment. MethodsTwenty one strains of Actinomycetes were isolated from samples of Royapuram, Muttukadu, Mahabalipuram sea shores and Adyar estuary. Preliminary screening was done using cross-streak method against two gram-positive and eight gram-negative bacteria. The most potent strains C11 and C12 were selected from which antibacterial substances were extracted. The antibacterial activities of the extracts were performed using Kirby-Bauer disc diffusion method. Molecular identification of those isolates was done. ResultsAll those twenty one isolates were active against at least one of the test organisms. Morphological characters were recorded. C11 showed activity against Staphylococcus species (13.0±0.5 mm), Vibrio harveyi (11.0±0.2 mm), Pseudomonas species (12.0±0.3 mm). C12 showed activity against Staphylococcus species (16.0±0.4 mm), Bacillus subtilis (11.0±0.2 mm), Vibrio harveyi (9.0±0.1 mm), Pseudomonas species (10.0±0.2 mm). 16S rRNA pattern strongly suggested that C11 and C12 strains were Streptomyces species ConclusionsThe results of the present investigation reveal that the marine Actinomycetes from coastal environment are the potent source of novel antibiotics. Isolation, characterization and study of Actinomycetes can be useful in discovery of novel species of Actinomycetes.

Assessment of the levels of coastal marine pollution of Chennai city, Southern India

The levels of hydrological pollution of Chennai coastal zone in the southeastern part of India have been increased in the recent years by an uncontrolled disposal of wastewater and pollutants due to human activities. This study gave a special emphasis on the determination of the levels of pollution, the identification of vulnerable zones and providing some probable remedial measures for severely impacted coastal zone of Chennai city. During the period from September to November 2002, sampling was carried out along the shore in two traverses running in the seaside (surf zone) and landside (coastal aquifer). When sampling efforts took place the middle of the above period experienced a monsoonal storm over Chennai coast that significantly influenced large variations in the pollution level at both traverses in seaside and landside. Analysis of physical, chemical and biological parameter determinations indicated that the concentrations of dissolved oxygen (DO), biochemical oxygen demand (BOD), chemical oxygen demand (COD), nutrients (nitrate, nitrite and phosphate), turbidity, maximum probable number (MPN) and chlorophyll a (Chl a) reached notably high levels at all sample locations before monsoonal storm prevailed over these areas during October 2002, which resulted in large fresh water input to the coastal system reducing the levels of pollution to some extent. Analysis of water samples collected during November apparently indicated that the concentrations of above parameters attained abnormal level and often exceeded the permissible limit of international standards. The concentrations of trace/toxic metals such as manganese, copper, nickel, lead, cadmium and cobalt also reached very high levels as a result of their sub-aqueous disposal to these areas, leading to further habitat and ecological destruction. On the other hand, analysis of groundwater samples collected from coastal aquifer for determination of certain chemical parameters such as Ca2+/Mg2+, Cl−/(CO2−3+HCO3-) and the ratio of total alkalinity (TA) and total hardness (TH) revealed that coastal groundwater appeared to be severely contaminated by saltwater intrusion as a result of overexploitation and enormous pressure imposed by monsoonal storm of October. Higher concentrations of toxic elements, for example, lead, nickel, cobalt and cadmium from the influence of industrial wastes and contaminated coastal waters, were also found to deteriorate the quality of coastal aquifer system. Based on detailed examination, four sites including Cuvum estuary, Adyar estuary, Kannikoil and Bharathiyar nagar are identified as highly venerable zones because of receiving a large quantity of municipal and industrial wastes. To reduce severe pollution levels in these areas it is therefore necessary to design and construct the submarine pipeline system to transport and disperse such a large quantity of waste materials to the deep open ocean areas.

Human impacts on methane emission from mangrove ecosystems in India

This study deals with the emission of methane in relation to changing environmental conditions and human impact, in three mangrove ecosystems of south India. Time-varying fluxes of methane adopting the close chamber technique were used to estimate CH4 emission from an unpolluted site (Pichavaram mangroves) and two polluted sites viz. (1) Ennore Creek mangroves (affected by fertilizer effluents and crude oil discharges) and (2) Adyar estuary mangroves (affected by the discharges of organic and industrial wastes), covering monthly and seasonal variations. The results indicate annual average CH4 emissions of 7.4, 5.02 and 15.4 mg m−2 h−1 from the sediment–water interface of the Pichavaram, Ennore Creek and Adyar estuary respectively. Emission characteristics obtained at Pichavaram mangroves represent a natural variability with changing physico-chemical factors, whereas the emission characteristics at Ennore Creek and Adyar estuary mangroves show anthropogenic influence. Several environmental factors such as oxygen availability, organic matter, soil physical and chemical properties, in addition to human-mediated interventions have been identified as influencing emission rates in the mangrove ecosystems. Preliminary CH4 emission estimates for the mangrove ecosystems along the Indian sub- continent and the tropical and subtropical coastline of the world by linear extrapolation based on surface area range from 0.05 to 0.37 and 2.8 to 19.25 Tg CH4 year−1 respectively. Our results also highlight the impact of human activities on future emission of methane from the mangrove ecosystems.

Natural and Anthropogenic Effects On Phytoplankton Primary Productivity in Mangroves

Spatial and temporal variations and the factors influencing primary production have been studied in three different mangrove waters (Pichavaram, Ennore Creek and Adyar Estuary) of South India characterised by different anthropogenic impacts. the gross primary productivity in the unpolluted Pichavaram mangrove was 113 g Cm−2yr−1 exhibiting natural variability with the environmental forcing factors. Human activities have elevated primary productivity in the Ennore Creek mangrove (157g Cm−2yr−1) primarily through the direct discharge of fertilizer effluents. By contrast, a combination of domestic and industrial effluent discharges into the Adyar Estuary mangrove has considerably reduced phytoplankton primary productivity 83g Cm−2yr−1 the Redfield N: P ratio varies from 0.96 N: 1P at Ennore Creek, 1.75N: 1P at Adyar Estuary to 15.2 N: 1P at Pichavaram mangroves. This suggests that the Pichavaram mangroves represent a well equilibrated ecosystem with N: P ratio close to steady-state values in contrast to the anthropogenically altered mangrove ecosystems studied. Results show a significant temporal variability in nutrient concentration in the three mangrove areas. Distinct differences in nutrient concentrations between the dry and the wet seasons have been observed.

Development of Asymmetry and Handedness in the Fiddler Crab UCA (&lt;i&gt;Celuca&lt;/i&gt;) &lt;i&gt;Triangularis bengali&lt;/i&gt; Crane, 1975 inhabiting the Adyar Estuary and Backwater

Development of Asymmetry and Handedness in the Fiddler Crab UCA (&lt;i&gt;Celuca&lt;/i&gt;) &lt;i&gt;Triangularis bengali&lt;/i&gt; Crane, 1975 inhabiting the Adyar Estuary and Backwater

Heavy Metal Concentrations in the Fiddler Crabs inhabiting the Adyar Estuary and Backwater

Heavy Metal Concentrations in the Fiddler Crabs inhabiting the Adyar Estuary and Backwater

Droving Behaviour Observed in the Fiddler Crabs Inhabiting the Adyar Estuary and Backwater

Droving Behaviour Observed in the Fiddler Crabs Inhabiting the Adyar Estuary and Backwater