@article {128073, title = {Carbonate budgets in Lakshadweep Archipelago bear the signature of local impacts and global climate disturbances}, journal = {CORAL REEFS }, year = {2023}, month = {04/2023}, abstract = {

Predicted sea-level rise and increased storm frequency caused by climate change drastically threaten low-lying inhabited coral atolls. Coral reef frameworks are the atolls{\textquoteright} primary defence from these changes. The growth and integrity of these frameworks is reflected in their carbonate budgets, a dynamic balance between biogenic accretion through coral growth and erosional forces, both of which are affected by factors acting at different spatial scales. We explored how carbonate budgets, estimated using the ReefBudget methodology, vary between three inhabited atolls that face differing anthropogenic stressors in the Lakshadweep Archipelago in the Northern Indian Ocean. We surveyed ten reefs, at two depths each, across the three islands. Overall, net carbonate budgets of reefs across all atolls were below optimal production rates needed to continue protecting shorelines (5 G measured on healthy reefs). This was a result of repeated mass bleaching events as well as local impacts. Carbonate production was influenced by a recent mass bleaching event in 2016 and a cyclone in 2018, and varied between depths and exposures, potentially due to differential recovery and mortality dynamics. Erosional processes were locally mediated with both urchin and parrotfish density showing large differences between islands, possibly linked to nutrient outflow and fishing intensity. We also find that by the year 2100, a large proportion of shallow sites will experience an increase in water depth above half a metre under moderate and high emissions scenarios, but none will breach this threshold under a low emissions scenario. Our results show that patterns of carbonate production were largely mediated by the history of global/regional disturbances, while erosional rates were much more dependent on local factors.

}, doi = {10.1007/s00338-023-02374-8}, author = {Patel, Farai Divan and Pinto, Wenzel and Dey, Mayukh and Alcoverro, Teresa and Arthur, Rohan} } @article {133185, title = {Tolerance to aerial exposure influences distributional patterns in multi-species intertidal seagrass meadows.}, journal = {Mar Environ Res}, volume = {191}, year = {2023}, month = {2023 Aug 19}, pages = {106146}, abstract = {

Multi-specific seagrass meadow assemblages dominate most tropical intertidal regions but the relative role of environmental stress in determining distribution patterns is still uncertain. Here we combine observational and experimental approaches to examine aerial exposure as a factor driving species occurrence patterns in intertidal meadows of the Andaman archipelago, where up to 6 seagrass species co-occur. In the studied meadow, patterns of exposure did not map onto distance from the coast, instead creating a patchy matrix of exposure, based on fine-scale bathymetric differences. Distributional surveys showed that seagrass species were similarly patchy, often tracking the degree of aerial exposure during low tide. While some species (Halophila ovalis, Halophila minor, and Thalassia hemprichii) frequently occurred in submerged or subtidal areas and were rarely found in completely exposed areas, other species (Cymodocea rotundata, Halophila beccarii, and Halodule uninervis) also occupied areas that were subject to partial or complete aerial exposure during low tide. To confirm this pattern, we used field-based transplant experiments, employing a natural gradient of tidal exposure to subject six seagrass species to different desiccation exposure times. After a month, H. beccarii and H. uninervis transplants survived in areas that sustained more than 3\ h of aerial tidal exposure without significant mortality, compared with other species (H. ovalis, H. minor, T. hemprichii, C. rotundata) that showed dramatic shoot mortality at the same exposure regimes. For all species, 4\ h represented the upper limit of exposure, in both experimental and distributional studies. However, despite their wider tolerance of exposure to air, H. beccarii and H. uninervis did not dominate the entire meadow. This could be a result either of their poor tolerance to other environmental factors or their lower competitive abilities among other mechanisms. This suggests that in tropical multi-specific meadows, strong environmental filters could override clear intertidal zonation to create patchy matrices based on species tolerances.

}, issn = {1879-0291}, doi = {10.1016/j.marenvres.2023.106146}, author = {Rao, Rachana and Alcoverro, Teresa and Kongari, Phoolmani and Yoayela, Saw and Arthur, Rohan and D{\textquoteright}Souza, Elrika} } @article {78163, title = {Wave exposure reduces herbivory in post-disturbed reefs by filtering species composition, abundance and behaviour~of key fish herbivores.}, journal = {Sci Rep}, volume = {10}, year = {2020}, month = {2020 Jun 19}, pages = {9854}, abstract = {

Harsh environmental conditions limit how species use the landscape, strongly influencing the way assemblages are distributed. In the wake of repeated coral bleaching mortalities in Lakshadweep, we examined how wave exposure influences herbivory \ in exposed and sheltered reefs. We used a combination of i. field observations of fish herbivore composition, abundance and activity across 6 exposed and 6 sheltered reefs; ii. experimental manipulations in a subset of these reefs (herbivore exclosures); and iii. opportunistic observations of fish recruitment, to determine how exposure influences herbivore biomass and herbivory. Species richness, biomass, abundance, total bite rates and species-specific per capita bite rates were lower in exposed compared to sheltered reefs, linked to strong environmental filtering of species composition, abundance and behaviour. For some critical species, this environmental filtering begins with differential recruitment and post-recruitment processes between exposures. Bite rates at sheltered sites were dominated by just a few species, most being laterally compressed surgeonfish that may find it difficult accessing or surviving in wave-battered shallow reefs. Exclosure experiments confirmed \ that exposed reefs \ were less controlled by herbivores than sheltered reefs. In post-disturbed reefs like Lakshadweep, environmental gradients appear to be key mediators of critical functions like herbivory by determining species composition, abundance and behaviour.

}, issn = {2045-2322}, doi = {10.1038/s41598-020-66475-y}, author = {Karkarey, Rucha and Rathod, Pooja and Arthur, Rohan and Yadav, Shreya and Theo, Anne and Alcoverro, Teresa} } @article {3570, title = {Choice and destiny: the substrate composition and mechanical stability of settlement structures can mediate coral recruit fate in post-bleached reefs}, journal = {Coral Reefs}, volume = {35}, year = {2016}, month = {March 2016}, pages = {211-222}, abstract = {

Increasingly frequent and intense ocean warming events seriously test the buffer and recovery capacities of tropical coral reefs. Post-disturbance, available settlement structures on a reef (often dead coral skeletons) vary considerably in their mechanical stability and substrate composition, critically influencing coral recruit settlement choice and fate. In the wake of a coral mass mortality in the Lakshadweep archipelago, we examine (1) the relative availability of recruit settlement structures (from stable to unstable: reef platform, dead massive coral, consolidated rubble, dead corymbose coral, dead tabular coral, and unconsolidated rubble) in 12 recovering reefs across three atolls in the archipelago, (2) the substrate composition [crustose coralline algae (CCA), mixed turf, macroalgae] of these structural forms, and (3) whether the choice and fate of young coral are mediated by the substrate and stability of different structural forms. For this, we measured the abundance and distribution of recruit (\<1 cm), juvenile (1{\textendash}5 cm), and young adult (5{\textendash}10) corals of 24 common coral genera. Four years after the mass mortality, reefs differed considerably in composition of settlement structures. The structures themselves varied significantly in substrate cover with dead tables largely covered in CCA [60 {\textpm} 6.05 \% (SE)] and dead corymbose coral dominated by mixed turf (61.83 {\textpm} 3.8 \%). The youngest visible recruits (\<1 cm) clearly preferred CCA-rich structures such as dead massives and tables. However, older size classes were rarely found on unstable structures (strongly {\textquotedblleft}avoiding{\textquotedblright} tables, Ivlev{\textquoteright}s electivity index, E = -0.5). Our results indicate that while substrate cover might mediate coral choice, the mechanical stability of settlement structures is critical in determining post-settlement coral survival. The composition and availability of settlement structures on a reef may serve as a characteristic signature of its recovery potential, aiding in assessments of reef resilience.

}, doi = {10.1007/s00338-015-1358-z}, url = {http://link.springer.com/article/10.1007\%2Fs00338-015-1358-z}, author = {Yadav, Shreya and Rathod, Pooja and Alcoverro, Teresa and Arthur, Rohan} } @article {11609, title = { For traditional island communities in the Nicobar archipelago, complete no-go areas are the most effective form of marine management }, journal = { OCEAN \& COASTAL MANAGEMENT }, volume = {133}, year = {2016}, month = {12/2016}, pages = {53-63}, abstract = {

The ability of local communities to sustainably manage natural resource harvests in coral reefs ecosystem depends heavily on the strength of traditional institutions. Coastal communities have evolved a suite of restrictive practices to control marine offtake and there is considerable recent evidence of their effectiveness in protecting and enhancing resource stocks. However, traditionally imposed restrictions can vary considerably in their complexity and in their functional effectiveness. The indigenous communities of the Nicobar Islands are dependent on marine resources for sustenance, managing them with a range of traditionally imposed restrictions. These include limited entry to certain locations, closed seasons and areas, and restrictions on species, size-classes of fish and fishing methods. We tested the relative effectiveness of protection in areas managed under different traditional control regimes by comparing the abundance and biomass of targeted fish groups in managed and unmanaged areas. Our results indicate that reef sites with the strictest form of restriction essentially no-go areas had significantly higher abundance and biomass values of most functional groups of fishes compared with partially protected and control locations. In contrast, targeted food fish stocks did not differ from control locations in partially protected sites managed with even complex forms of traditional management. Ensuring that traditional harvest rules are complied is critical to the success of any management system, and our results suggest that they can be most strictly enforced in traditional no-go areas. Our work highlights the importance of critically evaluating the factors influencing traditional management systems to strengthen their ability to protect these reefs from unsustainable overharvest. (C) 2016 Elsevier Ltd. All rights reserved.

}, doi = {10.1016/j.ocecoaman.2016.09.003}, author = {Patankar, Vardhan and D{\textquoteright}Souza, Elrika and Alcoverro, Teresa and Arthur, Rohan} }