Phylogenetic affiliation of Pedinomonas noctilucae and green Noctiluca scintillans nutritional dynamics in the Gulf of Mannar, Southeastern Arabian Sea.

The present investigation focused on studying the phylogenetic position of the green Noctiluca endosymbiont, Pedinomonas noctilucae, collected from the Gulf of Mannar, India. In this study, we re-examined the evolutionary position of this endosymbiotic algae using rbcL sequences. The phylogenetic analysis revealed that P. noctilucae is distantly related to the Pedinomonas species, and formed a monophyletic clade with Marsupiomandaceae. Based on the phylogenetic association of endosymbiont with Maruspiomonadales it was concluded that the endosymbiont belongs to an independent genus within the family Marsupiomonadaceae. At the site of the bloom, Noctiluca scintillans was found to exhibit a dense monospecific proliferation, with an average cell density of 27.l88 × 103 cells L-1. The investigation revealed that the green Noctiluca during its senescent phase primarily relied on autotrophic nutrition, which was confirmed by the presence of a high number of trophonts, vegetatively reproducing cells (1.45 × 103 cells L-1) and the absence of food vacuoles.

Moving beyond traditional macrofaunal community structure studies in the Indian Ocean continental shelf: a research synthesis based on research weaving.

The Indian Ocean (IO) continental shelf characterized by unique oceanographic and meteorological features and extreme habitat is a biodiversity hotspot region. Marine biodiversity provides valuable resources and services, in terms of economy, cultural, science, and education. Unsustainable exploitation and habitat degradation represent the greatest threat to biodiversity. Understanding how these services will change in the future requires knowledge of marine biodiversity. Although macrofaunal biodiversity is critical for the functioning of shelf systems, it has received much less attention, particularly in the IO, mainly due to logistics reasons precluding our ability to predict future changes. Here, we discuss the state of knowledge of macrofaunal ecology, to identify the knowledge gaps, which will allow for setting research priorities. The new framework in research synthesis, research weaving, that combines systematic mapping with bibliometric analysis was applied. The research weaving approach helps illustrate the evolution of research over time and identifies areas of current research interests and the performance of institutions and collaboration patterns. Data retrieved from the Web of Science were analyzed in the R and VOS Viewer software. The results highlight how macrofaunal research in IO is constrained by spatial and temporal scales, with the majority of studies focused on structural patterns. Moreover, most studies were conducted in a few countries (India, Australia, Saudi Arabia, Iran, and South Africa) using different sampling techniques hindering comparison within the IO habitats. Future studies investigating the macrofaunal community using a multidisciplinary approach and scientific collaboration (regional and international) can advance our efforts to close the marine biodiversity knowledge gaps.

Occurrence, characterization, and source delineation of microplastics in the coastal waters and shelf sediments of the central east coast of India, Bay of Bengal.

The present study investigates the abundance, distribution, and characterization (shape, size, colour, chemical composition) of microplastics (MPs) in surface water and sediment from the shelf region of the central east coast of India. The surface water and sediment samples were collected at varying depths (12.8-63 m) from 21 locations covering ∼1200 km. The mean abundance of MPs in surface water and sediments were 5.3 × 104 particles. km-2, 209 ± 99 particles. kg-1 of dry weight, respectively. Stereomicroscopy, Raman spectroscopy, and micro Fourier Transform Infra-red Spectroscopy (FTIR) were employed for the quantification and characterization of the polymers. Polyolefin (polyethylene and polypropylene) were the dominant polymers in both surface water and sediments indicating their source primarily land based. Surface water and sediment MPs were mostly blue coloured. Fibre (77%) and fragment (38%) were the dominant morphotypes in surface water and sediments, respectively. Surface characteristics studies using Scanning Electron Microscope (SEM) highlight the breakdown progress of the particles; Small MPs (<1 mm) account for >50% of the whole and dominant in the offshore region (10 km). The results reveal that the primary sources of MPs are most likely to be originating from riverine fluxes and fishing-based activities.

Litter and plastic monitoring in the Indian marine environment: A review of current research, policies, waste management, and a roadmap for multidisciplinary action.

Environmental contamination due to plastic waste mismanagement is a growing global concern. Plastic problem is of particular concern to the Indian Ocean nations as Asia currently contributes to the highest share of mismanaged plastic waste. Consequently, there is a worldwide interest to understand the distribution and transboundary movement of plastic from this region, which is crucial for implementing management measures. This review article focuses on current knowledge of plastic research, policies, waste management, socio-economics, challenges, and research opportunities. To date, marine plastic studies have focused on a few locations, providing an analysis of distribution and plastic-organism interactions in the Indian marine system. Along with scientific investigation, enforcement, improvisation, and, if necessary, framing new policies, integrated technologies to manage plastic waste, and behavioural changes are essential to mitigate plastic pollution. Such measures will be effective through a combination of actions among national and international researchers, industries, environmental managers, and the public.

Trait-based and taxonomic macrofauna community patterns in the upwelling ecosystem of the southeastern Arabian sea.

Coastal upwelling that occurs in the eastern Arabian Sea (EAS) drive the complex dynamics of the food chain. Macrofauna plays a key role in the functioning of coastal ecosystems, but few studies explored the taxonomic and functional patterns of macrofaunal communities under the influence of upwelling. These patterns have been investigated in this study by sampling macrofauna and environmental variables during March-December 2012 across six depths (13-100 m) over the continental shelf off Kochi, south EAS. Upwelling, set over outer shelf prior to March, occupies the entire shelf by May, peaked during June-July and withdrew rapidly by September. A total of 203 macrofaunal taxa were collected in this study. Multivariate analysis revealed that the macrofaunal composition showed a spatiotemporal variation. Taxonomic diversity increases from nearshore to mid shelf whereas abundance and biomass decreased. Macrobenthic functioning, assessed through Biological Trait Analyses, displayed similar trait modalities between depths and seasons but abundance driven differences in trait expression revealed important habitat filtering. Increase in organic matter and decrease in dissolved oxygen influenced by upwelling and the spatial variation in sediment texture were the strongest drivers of the macrofaunal taxonomic pattern. We suggest that taxonomic and biological trait information needs to be considered in ecological studies as it provides a better understanding of how biodiversity responds to and interacts with environmental changes.

Testing the efficiency of temperate benthic biotic indices in assessing the ecological status of a tropical ecosystem.

The objectives of the present study were to evaluate the ecological status of tropical coastal waters using the temperate benthic indices and examine the effect of seasonal variability on the performance of benthic indices. Macrobenthic samples were collected from northwest to southeast coast of India during 2003-2012 and we tested different univariate indices, ecological strategies, indicator species and multimetric indices. AMBI and multimetric indices performed satisfactorily in evaluating the ecological status. Seasonal variability on the biotic indices was observed during the southwest monsoon and fall intermonsoon period due to recruitment. Therefore, we recommended the non-monsoon period (January-May) as a suitable time of the year to use the indices for effective assessment of the Indian coastal waters. Results show that, the temperate benthic indices are efficient in assessing the tropical environmental status. However, complementary use of different indices is suggested for accurate assessment of the environmental status.