Assessments of reef sediments in the North Ari Atoll (Maldives) were conducted in 2015 and 2018 on reefs of three islands with different management strategies: community, resort, and uninhabited. Indices applied were the Foraminifera in Reef Assessment and Monitoring Index (FI) and the Sediment Constituents Index (SI). Both indices are based on shells or fragments of functional groups, which for the FI are foraminiferal shells and for the SI are sediment components. The FI is considered to be an indicator of water quality and the SI an indicator of water quality, community structure, and processes such as grazing and bioerosion. Both indices indicated that environmental deterioration occurred between 2015 and 2018, likely related to the intense temperature anomaly in March-June 2016 that caused widespread coral bleaching and mortality. Median FI declined from 5.1 to 4.0 overall, indicating that water quality still supports reef accretion, though the replacement of coral cover by algae and sponges likely provides more food sources for smaller, faster-growing foraminiferal species. The median SI values similarly declined from 3.8 to 3.0, reflecting a decrease in identifiable coral fragments and an increase in unidentifiable clasts, likely indicative of increased bioerosion. Although a minor component, molluscan fragments also increased by 25%, likely in response to more algal cover for grazers. In 2015, the FI and SI data indicated that the island management regime contributed to the reef health status. Uninhabited islands were associated with higher indices compared to resort and community islands. A clear distinction between management regimes was not observed in 2018, because a major decrease in FI (median: 4.9 in 2015, 2.9 in 2018) was recorded offshore from an agricultural settlement on the previously "uninhabited" island surveyed. These observations support the usefulness of these indices in reef assessment, and provide additional understanding that the FI can respond to a coral-mortality event that alters food sources in the benthic community. 1. Introduction Coral reefs are among the most diverse, complex and vulnerable ecosystems on Earth, and their status is influenced by a wide range of environmental variables (e.g.

Upper Triassic carbonate platforms from the Panthalassa Ocean remain less-understood and less-studied than their Tethyan equivalents. This imbalance is largely due to the poorer preservation state of Panthalassan carbonate rock successions in terms of rock quality and depositional geometries, which prevents good appreciation of depositional systems. In this context, carbonate exposures from Lime Peak (Yukon, Canada) represent an outstanding exception. There, the remains of an Upper Norian Panthalassan carbonate platform are well-exposed, show remarkably preserved depositional geometries and overall superior rock preservation. In this work, we analyse the carbonates from the Lime Peak area with particular attention to the vertical and lateral distribution of biotic assemblages and microfacies at the platform scale. Results demonstrate that the Lime Peak platform was surrounded by a basin with an aphotic sea bottom. The carbonate complex developed in warm waters characterized by high carbonate saturation. The area was also defined by moderate to high nutrient levels: this influenced the type of carbonate factory by favouring microbialites and sponges over corals. During its growth, Lime Peak was influenced by tectono-eustatism, which controlled the accommodation space at the platform top, primarily impacting the internal platform environments and the stability of the slope. Gaining better knowledge of the spatial distribution and dynamics of Upper Triassic organisms and sedimentary facies of Panthalassa in relation to tectono-eustatism lays the first foundations for reconstructing more robust platform models and understanding the evolution of other, more dismantled Upper Triassic Panthalassan carbonate systems through time.

This is a repository copy of Unravelling the paleoecology of flat clams: new insights from an Upper Triassic halobiid bivalve.

The Amphistegina Bleaching Index (ABI) was applied to three Maldivian reefs in the Rasdhoo and North Ari Atolls in 2018, during normal sea surface temperature conditions. This dataset was then compared with a 2015, pre-coral bleaching study. The results provide a context for the verification and application of the ABI in outlining the photoinhibitory stress status of coral reefs outside of the Florida Reef Tract where it was originally developed. The sampling periods encompass different seasons and temperature regimes. The 2015 field sampling preceeded the El Niño induced, mass coral-bleaching events of 2015 and 2016. It was carried out in late April and early May, during the dry season, when temperatures exceeded 31.5°C and photosynthetically active radiation (PAR) was high. The 2018 sampling took place near the September equinox, towards the end of the monsoon, when PAR was again high, though water temperatures were~30°C. Although there were slightly higher percentages of bleached Amphistegina in 2018, there were also higher percentages of juveniles, indicating either that (1) the chronic stress was insufficient to impact asexual reproduction or (2) the onset of stress was within the past few weeks; the latter hypothesis was supported by an increase in PAR and temperature coinciding with the time of sampling. From the ABI plots it is possible to distinguish between the 2015 (high data scatter), highly stressed pre-bleaching conditions with elevated photo-oxidative stress levels, and the near-baseline conditions represented by the 2018 dataset (tight data clustering). Overall, this study thus shows the potential of Amphistegina populations and the ABI in forecasting bleaching events, and contributing to the question of the resilience potential of the coral reefs as a whole. It also highlights the usefulness and suitability of the ABI, within Maldivian coral reefs, as an indicator of photo-inhibition through photo-oxidative stress that can increase susceptibility to coral bleaching as water temperatures approach or exceed the bleaching threshold.

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