Fragmented mangroves are generally ignored in N2O flux studies. Here we report observations over the course of a year from the Mangalavanam coastal wetland in Southern India. The wetland is a ...fragmented mangrove stand close to a large urban centre with high anthropogenic nitrogen inputs. The study found the wetland was a net source of N2O to the atmosphere with fluxes ranging between 17.5 to 117.9 µmol m−2 day−1 which equated to high N2O saturations of between 697 and 1794%. The average dissolved inorganic nitrogen inputs (80.1 ± 18.1 µmol L−1) and N2O emissions (59.2 ± 30.0 µmol m−2 day−1) were highest during the monsoon season when the rainfall and associated river water inputs and terrestrial runoff were highest. The variation in N2O dynamics was shown to be driven by the changes in rainfall, water column depth, salinity, dissolved oxygen, carbon, and substrate nitrogen. The study suggests that fragmented/minor mangrove ecosystems subject to high human nutrient inputs may be a significant component of the global N2O budget.
Studies of marine tardigrades from Indian waters is very limited and relatively obscure. A new species of marine tardigrade is described from the southeast coast of India as part of an effort to ...better understand the marine tardigrade biodiversity of the Indian subcontinent. Batillipes kalami sp. nov. described from the sandy sediments of the mid littoral zone can be differentiated from all its congeners by the presence of unconstricted primary clavae, two pairs of lateral body projections between leg II and leg III, long and blunt ended lateral body projections between leg III and leg IV, shape of leg IV sensory organs and the presence of dorsal indentations in its head.
Copper (Cu) and zinc (Zn) play a vital role in the growth and development, however increased uptake causes deleterious effects in normal functioning of organisms. We have demonstrated in this ...contribution the tolerance limit of Cu and Zn on Etroplus suratensis (pearl spot) by Continuous Flow Through (CFT) bioassay and the biomarker responses. The accumulation for Cu, Zn and selected trace metals (Cr, Cd, Ni and Pb) from field conditions, as well Geo-accumulation index (I geo) and Contamination factor (C.F) suggested moderate to heavy pollution in the Cochin estuarine system. The 96 h LC50 values for Cu was 1.74 ± 0.04 mg L−1and that for Zn was 24.36 ± 0.58 mg L−1 at 95% confidence interval. No observed effect concentration (NOEC) and low observed effect concentration (LOEC) for Cu and Zn were derived based on the survival rates. Chronic toxicity values for Cu and Zn were 0.23 mg L−1 and 2.005 mg L−1 respectively for 30 days period. The histological, biochemical, hematological and behavioral parameters showed significant variations at sublethal concentrations. Lamellar hyperplasia in gills, vacuolation combined with necrosis in liver, increased occurrence of melanomacrophage centres in spleen were noticed at chronic levels for both Cu and Zn. Tissue specific bioconcentration was observed for zinc and copper in gill and liver respectively, with least rate of bioconcentration observed in muscle tissues. Malaonate Dehydrogenase (MDH), Super oxide dismutase (SOD), Nonspecific esterase (EST) activity significantly varied compared to control at NOEC and LOEC values in both the metals. The hematological and genotoxic alterations as decrease in erythrocyte count, lymphocytes, hemoglobin concentration and hematocrit percentage were significantly reduced (p < 0.05) and increased thrombocytes and neutrophils, increased frequency of micronuclei, lobed, blebbed and notched nuclei and binucleate cells were characteristic for the metals at the sublethal concentrations. The frequency of behavioral changes remained significantly higher at chronic level than the control group. Thus such CFT based studies are important for precisely mapping the toxicity changes in organisms and also to develop suitable water quality guidelines.
•Chronic toxicity values for Cu and Zn on Etroplus suratensis were 0.23 mg L−1 and 2.005 mg L−1 respectively.•Analysis of water and sediment samples from Cochin estuary showed contamination from Cu and Zn.•Tissue-specific pattern of bioaccumulation of Cu and Zn were observed during study.•Evident biomarker changes in Etroplus suratensis were observed on exposure to Cu and Zn.
There is growing awareness of the need to better constrain the contribution of atmospheric methane (CH4) fluxes from urbanized estuaries due to the high global warming potential of CH4 and the ...accelerating growth of urban expansion. This study undertook seasonal sampling campaigns to understand the impact of urbanization on atmospheric CH4 fluxes and their drivers in a large, tropical estuary in India. Overall, the study found that the Cochin estuary emitted large amounts of CH4 (398.8 ± 141.6 μmolm−2d−1) to the atmosphere with CH4 hotspots reaching up to 939.7 μmolm−2d−1 were identified. The strongest drivers of CH4 dynamics in different anthropogenically impacted zones were traced. The source of organic matter for CH4 production was revealed to be terrestrial C3 plants, autochthonous production, marine phytoplankton, and sewage inputs. The study suggests that monsoonal urbanized tropical estuaries may be an important but under-recognized element of the global CH4 budget.
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•CH4 fluxes increased thirty-two fold and were higher than in many European estuaries.•CH4 hotspots correspond to regions highly affected by anthropogenic interventions.•Urbanized tropical estuaries are an under-recognized element of the global CH4 budget.
Heavy metal contamination has threatened India’s biodiverse-rich coastal wetlands, backwaters, rivers, estuaries and mangroves due to unscientific industrial activities and urbanisation. Among the ...Indian states, the Cochin city is the commercial and economic hub of Kerala along the coastal belt of Arabian Sea. Mangroves located are on the backwater channels and along the banks of Cochin estuary are near victims of this commercialization. Therefore, a comprehensive analysis of the sediment quality focusing on heavy metal contamination and pollution problems are documented from the mangrove habitats of Cochin, considering their immense ecological services offered to the coastal communities with an insight for future restoration activities. Out of the 17 metals analysed, concentration of 6, largely exceeded NOAA effect range low (Cr (5.5–202), Cu (0.89–40.68), Cd (0–1.34), Hg (0–0.68)) and effect range medium (Ag (0–4.68), Ni (0.06–64.5)), which marks the probability of adverse biological effects on mangrove plants and animals. Enrichment factor analysis revealed extremely severe enrichment of Ag (EF = 133), Hg (18.8), Pb (17.8) and Cd (17) and was supported by PCA analysis, that clearly derived the anthropogenic influence of Ag, Cd and Hg in mangroves. Contamination factor, geoaccumulation index and pollution load index revealed that the mangrove sites of Cochin are nearly stressed due to contamination (CF = 66.8) and extreme pollution effects (
I
geo
= − 1.8–5.4) due to silver, and considerably contaminated (CF = 4.4) with Cd especially in Aroor and Vypin zones. However, Valanthakad zone was almost free from metal pollution having better sediment quality where mangrove vegetation had luxuriant growth.
Benthic biotic indices are important ecological tools extensively used to understand the ecological quality of coastal wetlands. The present study aimed to assess the ecological status of ...Kodungallur-Azhikode estuary for the first time by using widely used benthic indices such as species richness (
S
), Shannon diversity index (
H
′log
2
), BENTIX, benthic opportunistic polychaetes amphipods (BOPA), AZTI’s Marine Biotic Index (AMBI) and multivariate AMBI (M-AMBI). In the canonical correspondence analysis, salinity, dissolved oxygen, organic matter, sediment Eh, sediment pH and sand were identified as important variance descriptors. A single species of an opportunist,
Americorophium triaeonyx
, an amphipod belonging to the ecological group (EG) III, significantly contributed to the total macrofaunal density. Other dominant opportunistic species included
Obelia bidentata
(EGII),
Arcuatula senhousia
(EGIII),
Cirolana fluviatilis
(EGII),
Prionospio cirrifera
(EGIV) and
Capitella
sp. (EGV). The overall assessment indicated a ‘good to moderate’ condition in AMBI, ‘good to poor’ condition in M-AMBI, ‘high to moderate’ condition in BENTIX, ‘high to poor’ condition in BOPA and ‘moderate to poor’ condition in univariate Shannon diversity index. All the multivariate indices tested in the study were correlated with each other except BOPA and M-AMBI. The group of stations dominated with a sandy substrate and a moderate level of organic content indicated high to good conditions while other stations demonstrated moderate to poor conditions. However, no significant variation in indices tested between seasons was observed. The present study recommends long-term monitoring of benthic macroinvertebrate assemblages with proper taxonomic identification and functional trait analysis for better calibration of indices, which is the key factor for getting better results.
•High sediment carbon burial in semi-enclosed mangrove habitat with high NPP.•Low carbon burial in aquaculture converted mangrove habitat.•Biological factors like litterfall and crab density act as ...primary controls.•Secondary controls were sediment accumulation rates and grain size.
Tropical mangrove environments have high carbon sequestration potential and this ecosystem service is currently used in mitigating climate change. However, these environments are declining rapidly in developing countries, diminishing their carbon sequestration potential and may ultimately transforming them as carbon dioxide sources. This study investigated the carbon sequestration potential through sediment burial at three mangrove habitats of Cochin, South-West coast of India. High burial estimates were recorded at two mangrove stations (2.95 ± 0.79–10.41 ± 2.50 t C ha−1 yr−1), but consistent with other tropical mangrove areas. Lower burial rates were estimated at one station (0.57 ± 0.24 t C ha−1 yr−1). Eighty percent of the mangrove net primary productivity through litterfall (NPPL) was stored in the sediment at the station with the highest burial rate, which is demonstrative of a robust carbon sink. However, at a different site, which is subject to aquaculture, only 7.23 % of NPPL was buried in the sediment. A major portion of the fixed carbon at this site is presumably emitted back to the atmosphere or exported to adjacent water bodies. The median total regional mangrove carbon burial rate in this study was 2.95 t C ha−1 yr−1 and the organic carbon burial rate was 1.93 ± 0.75 t C ha−1 yr−1. Biological factors such as mangrove biomass, litterfall and crab density have played a major role in controlling the sediment carbon burial rate. Sediment texture and bulk sediment accumulation acted as secondary controlling factors. The carbon source characterisation in the sediment profile using stable isotope techniques revealed the organic carbon origin as mangrove litter. Gaining a better understanding of carbon sources, burial rates and their controlling factors in mangrove habitats aids in regional climate mitigation efforts and global efforts to increase the carbon sequestration potential of tropical mangrove systems.
Mangrove forests sequester organic carbon, nutrients and toxic metals sorbed to fine sediment, and thus restrict the mobility of pollutants through estuarine environments. However, mangrove removal ...and environmental degradation caused by industrial activity and urban growth can impact the ability of mangrove communities to provide these critical ecosystem services. Here, we use sediment profiles from an impacted tropical estuary in southwest India to provide a c. 70-year record of carbon, nutrient and trace metal burial in the context of rapid urban development and the systemic removal of mangrove communities. Our results show that carbon and nutrient accumulation rates increase sharply during the 1990's in accordance with the high rates of deforestation. Nitrogen and phosphorus accumulation rates increased fourfold and twofold, respectively, during the same period. Organic carbon accumulation was fivefold higher than the global average during this period, reflecting intense deforestation during the last three decades. The enrichment of Hg, Zn, Pb, Mo, Ni, Cu and Mn demonstrate clear anthropogenic impact starting in the 1950's and peaking in 1990. Mercury, the trace metal with the highest enrichment factor, increased sevenfold in the most recent sediments due to increased fossil fuel emissions, untreated water and incineration of medical waste and/or fertilizers used in aquaculture. Organic carbon isotope (δ13C) and C:N molar ratios indicate shifts to more terrestrial-derived source of organic matter in the most recent sediments reflecting growing deforestation of which may be prevalent in southeast Asia due to increasing development. This study emphasizes the critical role played by mangrove ecosystems in attenuating anthropogenically-derived pollutants, including carbon sequestration, and reveals the long-term consequences of mangrove deforestation in the context of rapidly developing economies.
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•Mercury enrichment has increased up to 7-fold since the 1950's.•Increasing carbon burial in a tropical estuary is related to deforestation.•Recent sediments show high rates of carbon and nutrient burial.•Tropical mangroves are important sinks for pollutants in areas of rapid development.
Microplastics are small plastic fragments less than 5 mm in diameter, and microplastic pollution is an emerging threat in our day to day life. Microplastic pollution was estimated in water, sediment ...and fish samples from selected stations along the Cochin estuary and nearby coastal areas in Kochi. The estuarine water and sediment samples recorded a larger number of microplastics than in beach samples with a mean abundance of 751.7 ± 452.21 particles/m3 and 1340 ± 575.22 particles/kg, respectively. Study stations near to the busiest city locations showed significantly high levels of microplastic pollution (p < 0.001). A total number of 46 fishes belonging to five species were dissected, from which nine microplastics were isolated. All of the isolated plastic materials were identified as secondary microplastics. Among different types, fibres were abundant in all the sampling sites. Selected particles were identified with Fourier Transform Infrared Spectroscopy analysis as cellophane, polystyrene, polyethylene, polypropylene, and nylon. The study found that the water and sediment samples from the Cochin estuary are seriously polluted with microplastics, and this is the first attempt to compare the microplastic pollution status of the Cochin estuary with the associated beaches.
Diatoms constitute one of the fundaments in the trophic food chains and are responsible for much of the bioaccumulation of heavy metals, in particular zinc, throughout the web of food chains. ...Chaetoceros calcitrans and Thalassiosira weissflogii are widely present as a dominant marine diatom in estuarine and coastal waters. The zinc uptake, its fractionation in subcellular structures and macromolecular compartments in two marine diatoms, C. calcitrans and T. weissflogii and trophic transfer under different macronutrient concentrations were investigated. The study reveals a significant interaction between macronutrients and metal uptake by the two diatom species. Increased cellular accumulation of zinc and N, P-limited condition were found to affect N, P and Si assimilation by diatoms negatively. Conversely, nitrogen (N) limitation inhibited the intracellular uptake of zinc. However, at higher concentration of zinc, the difference in zinc uptake between nutrient enriched condition (+NP) and nutrient limited (N or P) condition become smaller, indicating that the zinc uptake by diatoms is less dependent on N containing protein ligands at high Zn concentration. Nitrogen concentration in the medium was also found to affect the relative distribution of zinc in subcellular structures and macromolecular components. However, major portion of zinc was distributed in soluble substance and in the protein of the algal cells. The N limited condition facilitates the accumulation of zinc in cell organelles (insoluble substance) leading to increased toxicity. Trophic transfer of zinc was also measured by calculating percentage of metal retained in mussel, Perna viridis over the experiment period. Regardless of the algal species, the percentage of accumulation of zinc was found to be high in mussels fed with algal cells acclimated to nutrient enriched condition (31 and 38%). Our study therefore suggests that N enrichment may lead to an increase in Zn uptake and transfer in marine plankton.
•Ambient N concentration plays a pivotal role in uptake of Zn in C. calcitrans and T. weissflogii.•Increased cellular accumulation of zinc and N/P-limited condition negatively affect N, P and Si assimilation by diatoms.•Zinc uptake by diatoms is less dependent on N containing protein ligands at high Zn concentration.•Varying nutrient condition affects the Zn distribution in the subcellular compartments and macromolecular structures.•Nutrient enrichmnt may lead to an increase in zinc uptake and trophic transfer along the food chain.
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