A new deep-water coral species Telestula ridgensis sp. nov (Scleralcyonacea: Sarcodictyonidae) from the seamount of the Central Indian Ridge.

Telestula ridgensis sp. nov. is a deep-sea octocoral species collected from the Central Indian Ridges (CIR) seamount. The megabenthic communities were sampled from the depths between 1917 and 2053 m using a benthic sledge. It forms part of a baseline environmental and benthic ecological assessment. All these data will be functional in assessing the impact of future massive sulfide mining in the Indian Ocean. We describe a new octocoral species based on integrative taxonomic methods through morphological comparison and molecular phylogenetics. The sclerome of the new species consists of short, stellate plates, crosses, and irregularly shaped and branching forms with dense tubercular ornamentation. The polyp sclerites are arranged in longitudinal rows underneath the tentacles. Two mitochondrial DNA genes (mtMutS and COI) and one ribosomal nuclear DNA gene (28S rRNA) were sequenced to separate the new species. The phylogenetic analyses strongly support the placement of new species in the genus Telestula clade.

Two new deep-water species of squat lobsters (Crustacea: Anomura: Galatheoidea) from the Central and Southwest Indian Ridge.

The high diversity and endemism of benthic species on seamounts are extensively documented. Although the number of squat lobster species from seamount habitats has increased, species from the Central Indian Ridge (CIR) and Southwest Indian Ridge (SWIR) systems remain largely unknown. The hydrothermally active Indian Ridge system harbours potential sites for future Seafloor Massive Sulphides (SMS) mining. Since seabed mining may create a long-lasting impact on the deep-sea ecosystems, it could harm the unique deep-sea life associated with mineral deposits. This study identified two undescribed squat lobster specimens: one from the genus Munidopsis Whiteaves, 1874 from the CIR system in water depths ranging from 1981 to 2033 m, and one from the genus Typhlonida Macpherson & Baba in Machordom, Ahyong, Andreakis, Baba, Buckley, Garcia-Jimenez, McCallum, Rodriguez-Flores & Macpherson, 2022 from the SWIR system in depths ranging from 2070 to 2404 m. Both new species may be distinguished morphologically and genetically based on the partial mitochondrial (mtCOI) gene. To generate baseline environmental and biodiversity data, efforts for accurate sampling and correct identification of biological species are required.

A multi-metric fish index to measure the ecological quality of tropical predominantly open estuaries along the western coast of India.

Defining the ecological quality of estuaries is challenging because of the inadequacy of available methods and indices to characterise the ecosystem. In Indian estuaries, there are no scientific attempts to establish multi-metric fish index to determine the ecological status. A multi-metric fish index (EMFI) was customised for twelve predominantly open estuaries on India's western coast. The index was established at the individual estuary level to ensure uniformity and contrast from sixteen metrics that designate the fish community and diversity, composition and abundance, estuarine use and trophic integrity from 2016 to 2019. A sensitivity study was followed to measure the responses of the EMFI under different metric varying scenarios. There were seven metrics identified as the most prominent for the EMFI in metric alteration scenarios. We also deduced a composite pressure index (CPI) based on the anthropogenic pressures described for the estuaries. The ecological quality ratios (EQR) defined based on EMFI (EQRE) and the CPI (EQRP) for all the estuaries were positively correlated. The EQRE values calculated based on the regression relationship (EQRE on EQRP) showed the divisions from 0.43 (bad) to 0.71 (high) for the Indian west coast estuaries. Similarly, the standardised CPI (EQRP) values for different estuaries indicated that the values range from 0.37 to 0.61. Our results based on the EMFI suggest four estuarine systems (33%) as 'good', seven (58%) as 'moderate' and one (9%) as 'poor'. Generalised Linear Mixed Model for EQRE showed that EQRP and estuary influenced EQRE; however, the effect of year was not significant. This comprehensive study based on the EMFI is the first record for predominantly open estuaries along the Indian coast. Therefore, the EMFI established in this study could be reliably advocated as a sound, effective and composite tool of ecological quality for tropical open transitional waters.

Reef on the edge: resilience failure of marginal patch coral reefs in Eastern Arabian Sea under recurrent coral bleaching, coral diseases, and local stressors.

Marked by strong El Niño-Southern Oscillation (ENSO) effects during 2014-2016, global coral reefs underwent mass bleaching. Here, we conducted a comprehensive (2014-2019) study, coinciding with the 2014-16 ENSO, to investigate the response and resilience potential of marginal coral communities to the combined impact of recurrent thermal anomalies and multiple anthropogenic stressors before, during, and after the mass bleaching episodes. Our result unveiled that thermal-stress-driven back-to-back annual coral bleaching episodes caused coral mortality and significantly decimated coral cover, primarily in 2015 and 2016. Subsequent benthic regime shifts toward macroalgal and algal turf colonization, followed by an increase in coral disease prevalence and recruitment failure was observed after the recurrent bleaching episodes. Algal cover increased from 21% in 2014 to 52.90% in 2019, and a subsequent increase in coral disease occurrence was observed from 16% in 2015 to 29% in 2019. The cascading negative effect of multiple stressors magnified coral loss and decreased the coral cover significantly from 45% in 2014 to 20% in 2019. The corals in the intensive recreational diving activity sites showed higher disease prevalence, concurring with high mechanical coral damage. The present study demonstrates that consecutive thermal bleaching episodes combined with local stressors can cause declines in coral cover and promote an undesirable regime shift to algal dominance in marginal coral reef habitats within a short duration. These results are of particular interest given that marginal reefs were traditionally perceived as resilient reef habitats due to their higher survival threshold to environmental changes. The present study indicates that mitigation of local stressors by effective management strategies, in conjunction with globally coordinated efforts to ameliorate climate change, can protect these unique coral reefs.

Coral reef-associated brachyuran fauna (Crustacea: Decapoda: Brachyura) from Angria Bank off the west coast of India.

Underwater sampling via SCUBA and grab at the Angria Bank coral reefs off the central west coast of India in January 2014 revealed 11 species of Brachyura. Seven species, namely, Thusaenys irami (Laurie, 1906), Tanaocheles bidentata (Nobili, 1901), Portunus convexus De Haan, 1835, Xiphonectes macrophthalmus (Rathbun, 1906), Thalamita gatavakensis Nobili, 1906, Serenius ceylonicus (Laurie, 1906), and Soliella flava (Rathbun, 1894) are reported for the first time from Indian waters. Furthermore, the geographical distribution of T. irami and S. ceylonicus is extended westwards of hitherto known ranges.

Is the North Atlantic Geodia barretti (Porifera, Tetractinellida, Geodiidae) present on the Southwest Indian Ridge?

There are currently 163 species of Geodia Lamarck, 1815 described worldwide, many of which are found in deep waters, but none of which have been recorded from the Southwest Indian Ridge (SWIR). Spicule morphology and barcodes (Folmer COI, 28S (C2D2), partial 18S) suggest that a specimen of Geodia collected on the SWIR at a depth of 2236 m is closely comparable to Geodia barretti Bowerbank, 1858. Geodia barretti is the most studied and thus well-known deep-sea Geodia species, due to its wide North Atlantic distribution and key role in boreal sponge grounds. This unexpected and markedly disjunct record would extend the distribution range of this species considerably, consequently challenging our knowledge about interoceanic deep-sea sponges.

Three New Carnivorous sponge species (Demospongiae: Cladorhizidae) from the Seamounts of the Central Indian Ridge.

Deep-sea sponges are an imperative component of benthos. They accumulate the suspended organic matter by filtering large quantities of water and, with their intricate structures, provide the most suitable habitats for various associated organisms. We describe three new cadorhizid sponges from the Central Indian Ridge (CIR), Indian Ocean. The sponges are part of the benthic sledge collection conducted onboard the MGS Sagar in the CIR region. A detailed taxonomic description of two novel species, Asbestopluma (Asbestopluma) indiyansis sp. nov., and Asbestopluma (A.) bharatiyae sp. nov. are provided based on the morphological and molecular (mtCOI and 28S) markers. In addition, another new carnivorous species Chondrocladia sagari sp. nov. is described based on the morphological and mtCOI marker. The systematic and descriptions of new species are discussed based on the structural and phylogenetic analysis. Our study shows that the cladorhizid fauna of the seamounts from the CIR are unique and represent regionally endemic benthic habitats.

A new deep-sea sponge Fibulia occiensis sp. nov. (Poecilosclerida: Dendoricellidae) from the 25 South Oceanic Core Complex in the Central Indian Ocean Ridge.

We describe a new deep-sea sponge species, Fibulia occiensis sp. nov., from the Central Indian Ocean Ridge (CIOR) at Rodrigues Triple Junction (RTJ), of the family Dendoricellidae Hentschel, 1923. Two sponge specimens were collected between 19822079 m depth using a benthic sledge in the 25 South Oceanic Core Complex (OCC) region. The megabenthic fauna was collected to establish a baseline of environmental and benthic ecological data. This data will be handy in assessing the impact of sulfide mining in the near future. Fibulia occiensis sp. nov. is fragile and stalked, has a single type of oxea, and no sigma. The new species is different from the congeneric Fibulia species by its larger oxeas and the strongly curved isochelae.

Modelling the mixed impacts of multiple invasive alien fish species in a closed freshwater ecosystem in India.

Invasive alien species (IAS) influence the trophic organisation and food web structure in an invaded ecosystem, and therefore, it is imperative to quantify the resultant ecological impacts. The globally recognised ecosystem modelling platform, Ecopath with Ecosim, was used to delineate the impacts of IAS on a tropical freshwater pond ecosystem in India. We analysed the trophic interactions, consumption patterns, prey overlap and mixed trophic impacts of three co-existing invasive alien fish species, African catfish (Clarias gariepinus), suckermouth catfish (Pterygoplichthys pardalis) and Mozambique tilapia (Oreochromis mossambicus), on other functional groups in the ecosystem. Together, the three IAS shared 11% of the total energy consumption and about 50% of the energy consumption by the fish species/groups. There was no predation mortality for African catfish and suckermouth catfish, and a very low estimate for the same was recorded for tilapia (0.64 year-1). The IAS shared high mean prey overlap with the native fish groups (Garra sp., Etroplus suratensis, Systomus sarana, Chanda nama and various small species of the cypriniform genera Puntius, Rasbora and Devario) indicating a substantial competition between alien and native species in the ecosystem. Consequently, the three IAS exhibited higher mean negative mixed trophic impacts on these functional groups. A very high Finn's cycling index (39.59%), a low relative ascendency (28.5%) and a very low system robustness (0.07) were observed compared to similar ecosystems, and the baseline values. These indices exposed the vulnerability of the ecosystem towards perturbations, which could be due to the presence of multiple alien invasive species. Mitigating the impacts of IAS should involve a combination of approaches, including eradication through draining and harvesting, high-density stocking of similar trophic level fish in the pond, and local and national level policy interventions.

A new report on the deep-sea sponge-associated Spongicoloides weijiaensis Xu, Zhou & Wang, 2017 (Decapoda: Spongicolidae) from the Southwest Indian Ocean Ridge.

The sponge-associated benthic shrimp Spongicoloides weijiaensis Xu, Zhou & Wang, 2017 is reported for the first time from the Southwest Indian Ridge (SWIR). A single female specimen of S.weijiaensis was associated with the hexactinellid sponge belonging to Dictyaulus sp. that was collected using a benthic sledge from the southwest Indian Ridge at a water depth of 2358 m. The spongicolid shrimp is reported using both classical taxonomic and molecular tools (cytochrome c oxidase subunit 1-COI). The S. weijiaensis specimen from the SWIR appears to represent a morphological variant that has pigmented eyes, telson with thirteen spines, and a broadly rounded setiferous posterior margin. This new report at a latitude of nearly 26° South on the seamount provides the first Mid Ocean Ridge sector record for stenopodidean shrimp known to date.

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.

Bacterial diversity associated with a newly described bioeroding sponge, Cliona thomasi, from the coral reefs on the West Coast of India.

The bacterial diversity associated with eroding sponges belonging to the Cliona viridis species complex is scarcely known. Cliona thomasi described from the West Coast of India is a new introduction to the viridis species complex. In this study, we determined the bacterial diversity associated with C. thomasi using next-generation sequencing. The results revealed the dominance of Proteobacteria followed by Cyanobacteria, Actinobacteria and Firmicutes. Among Proteobacteria, the Alphaproteobacteria were found to be the most dominant class. Furthermore, at the genus level, Rhodothalassium were highly abundant followed by Endozoicomonas in sponge samples. The beta-diversity and species richness measures showed remarkably lower diversity in Cliona thomasi than the ambient environment. The determined lower bacterial diversity in C. thomasi than the environmental samples, thus, categorized it as a low microbial abundance (LMA). Functional annotation of the C. thomasi-associated bacterial community indicates their possible role in photo-autotrophy, aerobic nitrification, coupling of sulphate reduction and sulphide oxidization. The present study unveils the bacterial diversity in bioeroding C. thomasi, which is a crucial step to determine the functions of the sponge holobiont in coral reef ecosystem.

Molecular identification of deep-sea blind lobster Willemoesia forceps (Crustacea: Decapoda: Polychelidae) from the Central Indian Ridge.

The deep-sea blind lobster Willemoesia forceps A. Milne-Edwards, 1880 was collected at a water depth of 3433 m and is reported for the first time from the Central Indian Ridge (CIR). The species was identified based on morphological examination and supported by mitochondrial Cytochrome Oxidase Subunit I (mtCOI) gene. The phylogenetic analysis shows that W. leptodactyla is sister species of W. forceps. Our findings expand the distributional range of the specimen in the southern hemisphere.

Coral damage by recreational diving activities in a Marine Protected Area of India: Unaccountability leading to 'tragedy of the not so commons'.

Globally, coral reefs have drastically degraded due to local and global environmental stressors. Concurrently, coral reef tourism is rapidly growing in developing economies, which is one of many anthropogenic stressors impacting reefs. At the Malvan Marine Sanctuary, a Marine Protected Area (MPA) on the West coast of India, we investigated the impact of recreational diving on the reef from 2016 to 2019. To evaluate the diver's underwater behavior, a novel approach was used, wherein the video-log broadcasting website www.youtube.com was perused. Evidential proof substantiates heavy physical damage to corals because of recreational diving activity, which may lead to the collapse of coral habitat if it continues unabated. This resource depletion ironically elevates the economy of dependents averting consequences due to lost corals, thus making this a 'tragedy' for corals which are not meant to be 'commons'. The study asserts need for proactive conservation efforts with stringent implementation and restoration initiatives in this MPA.

Coral reef restoration - A way forward to offset the coastal development impacts on Indian coral reefs.

Globally, coral reefs are degrading rapidly due to the combined impact of wide-scale anthropogenic activities and climate change. Similarly, coral reefs in India are facing an existential threat because of intensified environmental degradation, which challenges reef ecosystem resilience and socio-ecological stability. Recently, Govt. of India has taken up the 'SagarMala Programme' aiming to increase its port capacity by the expansion of existing ports, construction of several new ports and allied infrastructure development by 2025. Synergistic impact of coastal development coupled with the on-going environmental changes is deemed to accelerate coral reef degradation in Indian reefs. Therefore, the present article aims to highlight the urgency of positive intervention and initiation of long-term holistic coral reef restoration program as an active reef management tool. Along with conventional management practices, reef restoration program could curtail further reef degradation and will ensure the persistence of Indian coral reefs and the services they provide.

Genetic variation of reef-building polychaete Sabellaria chandraae in the south-eastern Arabian Sea based on mitochondrial COI gene sequences.

The honeycomb worm Sabellaria chandraae is the most common reef-building polychaete in the intertidal area along the south-eastern Arabian Sea. We used the mitochondrial cytochrome c oxidase subunit I (mtCOI) gene to examine the levels of genetic variation the population. The samples were collected from seven intertidal areas along the south-eastern Arabian Sea. The hierarchical Analysis of Molecular Variance (AMOVA) and conventional population statistics (FST ) showed a low level of genetic differentiation (FST = 0.0864, p < .05), indicating no geographical patterning among seven populations. The present results were able to provide a reference for the single stock population along the south-eastern Arabian Sea.

18S rDNA sequencing data of benthic polychaetes from the Eastern Arabian Sea.

The limited DNA sequence data of the polychaetes species are available from the Eastern Arabian Sea. We have sequenced 18S rDNA gene from 54 polychaetes species and 37 species identified up to the species level. The DNA bar-coding data provides for molecular identification of benthic polychaetes that will provide imminent into drivers of species diversity in the Eastern Arabian Sea. The 18S rDNA sequence data set is made publicly available to enable critical or extended analyzes of DNA bar-coding.

Global Carbon Cycling on a Heterogeneous Seafloor.

Diverse biological communities mediate the transformation, transport, and storage of elements fundamental to life on Earth, including carbon, nitrogen, and oxygen. However, global biogeochemical model outcomes can vary by orders of magnitude, compromising capacity to project realistic ecosystem responses to planetary changes, including ocean productivity and climate. Here, we compare global carbon turnover rates estimated using models grounded in biological versus geochemical theory and argue that the turnover estimates based on each perspective yield divergent outcomes. Importantly, empirical studies that include sedimentary biological activity vary less than those that ignore it. Improving the relevance of model projections and reducing uncertainty associated with the anticipated consequences of global change requires reconciliation of these perspectives, enabling better societal decisions on mitigation and adaptation.

Genotoxicity of two heavy metal compounds: lead nitrate and cobalt chloride in Polychaete Perinereis cultrifera.

The present study explores the in vivo and in vitro genotoxic effects of lead nitrate, [Pb(NO3)2] a recognized environmental pollutant and cobalt chloride (CoCl2), an emerging environmental pollutant in polychaete Perinereis cultrifera using comet assay. Despite widespread occurrence and extensive industrial applications, no previous published reports on genotoxicity of these compounds are available in polychaete as detected by comet assay. Polychaetes were exposed in vivo to Pb(NO3)2 (0, 100, 500, and 1000 µg/l) and CoCl2 (0, 100, 300, and 500 µg/l) for 5 days. At 100 µg/l Pb(NO3)2 concentration, tail DNA (TDNA) values in coelomocytes were increase by 1.16, 1.43, and 1.55-fold after day 1, day 3, and day 5, whereas, OTM showed 1.12, 2.33, and 2.10-fold increase in in vivo. Pb(NO3)2 showed a concentration and time-dependent genotoxicity whereas CoCl2 showed a concentration-dependent genotoxicity in in vivo. A concentration-dependent increase in DNA damage was observed in in vitro studies for Pb(NO3)2 and CoCl2. DNA damage at 500 µg/L showed almost threefold increase in TDNA and approximately fourfold increase in OTM as compared to control in in vitro. Our studies suggest that Pb(NO3)2 and CoCl2 have potential to cause genotoxic damage, with Pb(NO3)2 being more genotoxic in polychaete and should be used more carefully in industrial and other activities. Graphical abstract.

Biological responses to disturbance from simulated deep-sea polymetallic nodule mining.

Commercial-scale mining for polymetallic nodules could have a major impact on the deep-sea environment, but the effects of these mining activities on deep-sea ecosystems are very poorly known. The first commercial test mining for polymetallic nodules was carried out in 1970. Since then a number of small-scale commercial test mining or scientific disturbance studies have been carried out. Here we evaluate changes in faunal densities and diversity of benthic communities measured in response to these 11 simulated or test nodule mining disturbances using meta-analysis techniques. We find that impacts are often severe immediately after mining, with major negative changes in density and diversity of most groups occurring. However, in some cases, the mobile fauna and small-sized fauna experienced less negative impacts over the longer term. At seven sites in the Pacific, multiple surveys assessed recovery in fauna over periods of up to 26 years. Almost all studies show some recovery in faunal density and diversity for meiofauna and mobile megafauna, often within one year. However, very few faunal groups return to baseline or control conditions after two decades. The effects of polymetallic nodule mining are likely to be long term. Our analyses show considerable negative biological effects of seafloor nodule mining, even at the small scale of test mining experiments, although there is variation in sensitivity amongst organisms of different sizes and functional groups, which have important implications for ecosystem responses. Unfortunately, many past studies have limitations that reduce their effectiveness in determining responses. We provide recommendations to improve future mining impact test studies. Further research to assess the effects of test-mining activities will inform ways to improve mining practices and guide effective environmental management of mining activities.