Unveiling the ecological status of the Arabian Gulf's marine ecosystem: Insights from benthic community analysis.

This study assessed the ecological health of waters within the Saudi Arabian Exclusive Economic Zone, by utilizing benthic biotic indices with a marine monitoring dataset covering the years 2013 to 2018. This comprehensive evaluation covered a vast expanse, encompassing 67 distinctive sampling locations characterized by a wide range of depth and salinity gradients. The study examined spatial fluctuations in the benthic community and assessed potential correlations with environmental variables, including salinity, depth, sediment texture, total organic carbon, and other relevant factors. The macrobenthic density varied across the study sites, with an average density of 566 ± 120 ind.m-2. The Shannon diversity index ranged from 3.21 and 5.90, with an average of 4.70 ± 0.52. Based on the average AMBI values, all the locations were categorized as either slightly disturbed or undisturbed. Additionally, the M-AMBI analysis indicated that 95.5 % sites were in good or high ecological status.

Carbon stock in biomass pool of fragmented mangrove habitats of Kochi, Southern India.

Even though, the blue carbon ecosystems are gaining keen research interest around the globe, the carbon stock of South-West coast of India was poorly reported, and this study is a pioneer attempt and will be an important document for filling the gaps in uncertainties in global carbon stock assessment and also will increase knowledge on biomass variability among mangrove species and mangrove habitats. The study also highlighted the vital role of biomass carbon pool for long-term soil carbon burial. We estimated the above and below-ground biomass carbon stock of 13 mangrove species using two common allometric equations and species-specific equations and reported a very high mean total living biomass carbon stock of Kochi mangroves at 237.19 ± 113.82 Mg C ha-1, 295.78 ± 143.14 Mg C ha-1, and 272.42 ± 132.78 Mg C ha-1 according to Chave's, Komiyama equation and species-specific equation respectively corresponding to carbon dioxide equivalent (CO2e) of approximately 4,37,774.51 Mg CO2e. The biomass stock was significantly differed between the stations (p = 0.000) and also within species (p = 0.020). Among the mangrove species, Avicennia officinalis contributed highest and Bruguiera sexangula contributed least. Variation was observed for biomass stock of mangroves with large trunk diameter while comparing different allometric equations and therefore projected the need for the development of site- and species-specific equations for solving the uncertainty in global mangrove carbon stock. The study observed that dominant mangrove vegetation type, salinity and also the geomorphology of mangrove habitat had strong influence on variability in biomass stock within a small regional area. The study also suggests that understanding the structure and biomass carbon storage of each regional mangrove habitats can be wisely used in mangrove restoration and conservation programmes and in turn for nature-based solutions for climate change mitigation efforts.

A multibiomarker approach to assess lead toxicity on the black clam, Villorita cyprinoides (Gray, 1825), from Cochin estuarine system (CES), southwest coast, India.

The southwest coast of India along the Cochin region is seriously affected by metal contamination from increasing industrial activities. This contribution pertains to the chronic toxicity effects of lead and its biomarker responses on the black clam, Villorita cyprinoides, largely endemic to Southern India. The metal concentration (lead (Pb), copper (Cu), zinc (Zn), cadmium (Cd), nickel (Ni), and chromium (Cr)) and contamination indices such as geoaccumulation index and contamination factor suggests that the Cochin estuarine system (CES) is moderately to heavily polluted with metals. The 96 h effective median lethal concentration (LC50) for Pb was 12.08 mg L-1 at 95% confidence level, whereas the NOEC (no observed effect concentration) and LOEC (lowest observed effect concentration) were 0.46 mg L-1 and 0.83 mg L-1 respectively. The chronic toxicity value for Pb was 0.64 mg L-1. Accumulation of Pb in V. cyprinoides after chronic toxicity test was several-fold higher than exposure concentration. On exposure to sublethal concentrations of lead, gills showed prominent pathological lesions such as damaged lateral cilia, congested hemolymph sinus, damaged abfrontal cilia, damaged ciliary filaments, fusion of gill lamellae, and reduced inter lamellar space. Filtration rate of clams exposed to Pb (86.69 ± 1.98 ml clam-1 h-1) was lower than that in control experiments (191.86 ± 6.48 ml clam-1 h-1). Antioxidant enzymes such as esterase (EST), superoxide dismutase (SOD), and malate dehydrogenase (MDH) exhibited different patterns in isoenzyme activity. Neutral red retention time (NRRT) showed a decrease from control to higher concentrations indicating membrane stability of hemocytic lysosomes decreased with the increasing metal exposure concentration. At LOEC and higher concentrations lysosomes showed enlargement and fragmentation. Lysosomal responses in V. cyprinoides can be used as a key cellular stress biomarker in assessing lead and other metal contamination.