Standardised methodologies for assessing reef-derived sediment generation rates do not presently exist. This represents a major knowledge gap relevant to better predicting reef-derived shoreline sediment supply. The census-based SedBudget method introduced here generates estimates of sediment composition and grain-size production as a function of the abundance and productivity of the major sediment-generating taxa at a reef site. Initial application of the method to several reefs in the northern Chagos Archipelago, Indian Ocean, generated total sediment generation estimates ranging from (mean ± SE) 0.7 ± 0.1 to 4.3 ± 1.3 kg CaCO3 m−2 yr−1. Sediment production was dominated by parrotfishes (>90% at most sites), with site-variable secondary contributions from sea urchins (up to 20%), endolithic sponges (~1–7%) and benthic foraminifera (~0.5–3.5%). These taxa-level contributions are predicted to generate sediments that at all sites are coral- (83–94%) and crustose coralline algae-dominated (range ~ 5–12%). Comparisons between these estimates and sedimentary data from proximal reef and island beach samples generally show a high degree of consistency, suggesting promise in the SedBudget approach. We conclude by outlining areas where additional datasets and revised methodologies are most needed to improve rate estimates and hope that the methodology will stimulate research on questions around sediment production, transport and shoreline maintenance.

Coasts are undeniably regions of critical importance for a range of environmental, sociocultural, and economic reasons. Yet they are also areas of intense anthropogenic impact and are particularly susceptible to climate change-related concerns. As such, it is imperative that we have the means to monitor and manage them in a sustainable manner. Drone technology has emerged as providing a unique value proposition in coastal environments to support data-driven monitoring and management decisions. With their highly detailed data capture capability, drones are particularly well suited to map the spatial heterogeneity, structural complexity, and temporally dynamic nature of coasts. Further, they are readily accessible to coastal populations and can promote grassroots action by the very people whose lives and livelihoods the coasts support. Herein, we cover several of the leading innovations in using aerial drones to map coastal ecosystems. We then consider how general trends and technology projections including artificial intelligence, as well as cloud and edge computing offer opportunities for the future of drone mapping and monitoring in a coastal context. While the challenge of change is inevitable, embracing the opportunities it provides will allow us to better understand and live sustainably with and within our coastal ecosystems.

Cleaning mutualisms are important interactions on coral reefs. Intraspecific variation in cleaning rate and behaviour occurs geographically and is often attributed to local processes. However, our understanding of fine-scale variation is limited, but would allow us to control for geography and region-specific behavioural patterns. Here, we compare the cleaning activity of Pederson's cleaner shrimp (Ancylomenes pedersoni) on two neighbouring, yet ecologically dissimilar, reef systems in Honduras: Banco Capiro, an offshore bank close to significant land runoff with high coral cover but a depleted fish population, and an oligotrophic fringing reef around the island of Utila, with lower coral cover but high fish abundance and diversity. The proportion of realized to potential fish clientele was <60% at both sites, and the composition of clientele was neither reflective of the demographics of the resident assemblages at each site nor similar between sites. Parrotfishes represented 13–15% of total fish abundance at both sites yet accounted for >50% (Banco Capiro) and 10% (Utila) of all cleans. Conversely, the schoolmaster snapper (Lutjanus apodus) represented ~1% of total fish abundance at both sites yet accounted for 40% (Utila) and 1% (Banco Capiro) of all cleans. After standardizing our cleaning rate data by clientele abundance, we find that clientele at Banco Capiro engage in over four times as many cleaning encounters per hour with A. pedersoni than at Utila. Our study highlights the variable nature of coral reef cleaning interactions and the need to better understand the ecological and environmental drivers of this biogeographic variation.

Coral reefs have experienced extensive degradation across the world over the last 50 years as a result of a variety of stressors operating at a range of spatial and temporal scales. In order to assess whether declines are continuing, or if reefs are recovering, detailed baseline information is required from across wide spatial scales. Unfortunately, for some regions this information is not readily available, making future reef trajectories difficult to determine. Here we characterized the current benthic community state for coral reefs in the Wakatobi region of Indonesia, one of the most biodiverse marine regions in the world. We surveyed 10 reef sites (5, 10 and 15 m depth) to explore spatial variation in coral reef benthic communities and provide a detailed baseline. Previous data (2002–2011) were available for coral, sponges, algae and soft coral at six of our study sites. Using this information, we determined if any changes had occurred in dominance of these benthic groups. We found that benthic assemblage composition differed significantly over relatively small spatial scales (2–10 km) and hard coral cover was highly variable, ranging from 7–48% (average 19.5% ± 1.5 SE). While coral cover appears to have declined at all sites where data were available since 2002, we found little evidence for widespread increases in other benthic groups or regime shifts. Our study provides a comprehensive baseline dataset for the region that can be used in the future to determine rates of change in benthic communities.

The island of Bonaire is a long-established Marine Protected Area (MPA), the reefs of which were extensively mapped in the early 1980s. Satellite remote sensing techniques were used to construct reef maps for 2008–2009. Metrics describing the spatial structure of coral habitat at the landscape scale – including coral cover, fragmentation, patch size and connectivity between patches – were calculated and compared between these two time periods. Changes were evaluated in and out of the MPAs and in areas exposed and sheltered from storm damage. Overall, coral cover has declined during the past three decades, being replaced by sand, but the decline has not been as drastic as elsewhere in the Caribbean. Fragmentation of the reef habitat has occurred, resulting in smaller and more disparate patches, but these changes were not associated with exposure along the coastline. However, total coral cover was maintained in sheltered areas, whereas it declined along exposed shorelines. Human protection of reefs by marine reserves had variable effects on coral cover and fragmentation. One of two no-diving marine reserves showed increases in coral cover accompanied by decreases in the number of patches of coral and an increase in the size of individual patches over the time period, while the second reserve exhibited the opposite trend. Advances in satellite remote sensing techniques allow for a more rapid assessment of changes in reefs at the landscape level, which can be used to identify spatial changes in the reef environment, including areas of coral decline.

New coral microatoll data allow presenting an updated late Holocene sea-level curve for the Gilbert Islands of Kiribati. Examination of build-up elevation and spatial distribution of microatolls, along with radiocarbon age data from coral samples, suggest an approximately 1 m sea-level high stand, possibly lasting from ~3500 to 1900 cal yr BP. Our sea-level curve, which is similar to the one reported from the Marshall Islands, is a baseline to reconstruct the evolution of reef flats and reef islands. In addition, it provides important contextual data to infer human settlement on islands in the west-central Pacific.

Small-scale mariculture of high-value species for trade in remote islands can offer valuable alternative livelihoods to local communities. The endangered giant clam species Tridacna maxima is naturally abundant in some atolls in French Polynesia (FP) and has been the focus of commercial mariculture activities since 2012. Shortly after spat collectors became operational in two atoll lagoons, FP rose to become one of the main exporters of giant clams for the aquarium trade. However, this activity has been threatened recently by a mass clam-bleaching event triggered by the 2015–2016 El Niño. This study reviews the roles that international (Convention on International Trade in Endangered Species of Wild Fauna and Flora) and national regulatory frameworks play in the development of this activity in a small island context, and how they can indirectly promote better science and monitoring in order to inform adaptive management strategies. The links between the nine main groups of stakeholders show the necessary adaptation measures required to mitigate climate-driven mortalities. While this case study remains specific to giant clam farming in FP, general lessons are provided that could help in mitigating economic impacts from climate-related events on other islands.

Coral microatolls have been long used as precise indicators of past sea level, but their use for precise definition of detailed sea-level fluctuations is still rare. Here we report twelve high-precision thermal ionization mass spectrometric 230Th ages for twelve rims of five mid-Holocene microatolls from an emerged reef terrace at Leizhou Peninsula, northern South China Sea. This is a tectonically stable area, enabling us to reconstruct both the timing and trajectory of local sea-level fluctuations accurately. The elevations of these microatoll rims and cores were accurately determined relative to the surface of modern living microatolls at the same site. The results indicate that the sea level during the period of 7050–6600 yr bp (years before AD 1950) was about 171 to 219 cm above the present, with at least four cycles of fluctuations. Over this 450 yr interval, sea level fluctuated by 20–40 cm on century scales.

Rapid population growth and economic change on the tropical islands of Mauritius have led to one of the highest rates of urban build-out in the world. Pressure on many of the island's natural features and resources increasingly risks further degradation to the environmental services that they provide to the country. Fourteen types of marine and terrestrial environmentally sensitive areas (ESAs) are critical to the nation's sustainable development. Twelve of these ESA types are currently at risk of degradation, owing to their spatial proximity to built-up areas (BUAs) and current use designation. There was a bimodal distribution in proximity; eight of the 12 ESA types analysed had an area-weighted modal peak < 500 m from the nearest BUA, and four ESAs had a modal peak 2–3 km from the nearest BUA. Six coastal and marine ESAs had limited protection from urban expansion and over-use. The Mauritian experience reflects trends that are emerging across many tropical developing countries, where the bulk of future global growth in urban area is expected to occur. The approach detailed in this case study is replicable and may be useful in assessing degradation risk as a result of urban expansion in other island countries.

We report 37 species of heterobranch sea slugs from the National Park Alacranes reef, located in the Campeche Bank, at the south-eastern Gulf of Mexico, of which 18 species are reported for the first time in this reef. With this contribution, the species richness in this national park increases to up to 67. The species Nakamigawaia felis, Petalifera sp., Elysia flava, Elysia pratensis and Bulbaeolidia sp. are reported in the Gulf of Mexico for the first time. The geographical distribution ranges for Oxynoe azuropunctata, Elysia ornata, Placida kingstoni, Aphelodoris antillensis and Tritonia hamnerorum are extended westward. Those for Elysia flava, Pleurobranchus areolatus and Felimare ruthae are extended both northward and westward.

The species of Glycerella share a prostomium with four rings bearing four distal appendages, and proboscis with rod-like aileron. They also have the first two parapodia uniramous, while the following are biramous, with dorsal and ventral cirri; the notopodia bear simple capillaries chaetae. The neuropodia are provided in the upper part with compound spinigerous chaetae while those in the lower part are falcigerous. Glycerella magellanica has been reported in the south-west Indian Ocean, south and north-west Pacific Ocean, and north and central Atlantic Ocean. Herein, the first record of this species is reported in the south-west Atlantic, specifically off the north-east coast of Rio de Janeiro, in the Campos Basin. A single specimen of this species was collected during the ECOPROF project coordinated by CENPES/PETROBRAS, although this species has been recorded elsewhere in muddy sediments. In this study the specimen was collected in a dead fragment of the coral Solenosmilia variabilis, at 745 m depth. Morphologically the specimen is very similar to that used in the original description. However, some morphological differences were found related to the appearance of the compound chaetae and aileron. These differences may indicate either that in the original description these features were overlooked, or rather a case of intra-specific variation.

Two reef fish species, Pseudolabrus guentheri and Chromis nitida, traditionally restricted to the central and southern Great Barrier Reef (GBR) were observed in the northern GBR. This range extension is unusual as it runs contrary to the general expectations of poleward range shifts associated with climate change.

Many reef-building corals photoacclimate by increasing levels of chlorophyll per microalgal cell with depth, but mechanisms of photoacclimation in coral reef sea anemones remain poorly understood. We determined variation in ambient irradiance and patterns of abundance, microhabitat use, chlorophyll and microalgal cell concentrations in clownfish sea anemones Entacmaea quadricolor from 0 to 43 m depth on a coral reef at Aqaba, Jordan, northern Red Sea. In shallow areas, anemones occupied shaded reef microhabitats exposed to significantly lower irradiance than in the adjacent open water, but on the deep reef slope they occupied unshaded habitats. Anemone abundances were the highest observed thus far in the Red Sea, and peaked at mid depth on the reef slope. Microalgal abundance in anemone tentacles increased four-fold from the shallow to deep reef, while chlorophyll-a concentrations per algal cell did not vary significantly with depth. We conclude that E. quadricolor photoacclimates using two major mechanisms: (1) occurrence in shaded microhabitats when shallow, thus reducing exposure to high irradiance, and (2) increasing microalgal abundance with depth, thereby enhancing photosynthetic efficiency at low irradiance.

This paper reports on the first record of the hydroid Eudendrium carneum in India near Poshitra, on the coast of Gujarat. The hydroid was identified by its colony characters, reproductive structures, polyp morphology and nematocysts.

Many tropical biodiversity projects seek to combine development and conservation goals. Here, we assess the performance of a revolving fund, established by Fauna & Flora International (FFI), in delivering sustainable and equitable benefits to coastal community livelihood groups and individuals while ensuring that it did no apparent harm to the environment. Semi-structured interviews were conducted with 103 loan recipients to determine changes in attitude, perception and behaviour. After a 9 month preparation phase the project succeeded in changing a community view towards the fund from being overwhelmingly pessimistic to overwhelmingly optimistic and then loaned IDR 602,977,400 (USD 66,261), with near perfect repayment rates thereafter (indicating financial sustainability). Most (92%) respondents thought that the fund had been a success, mainly (56%) because it had increased their perceived daily income. Even though most (59%) of the loan recipients met with FFI staff at least once per month on average during the project, the linkages between conservation and development were only understood by some (40%). Nevertheless, understanding was highest amongst the project's main target group, fishermen. Furthermore, nearly half of all respondents said they now acted if they found people fishing with spear guns or throwing litter into the sea (a violation of customary law), indicating a positive change in behaviour. Although this study cannot unambiguously demonstrate that this change was purely due to the fund, as FFI was conducting other conservation activities, it helped to develop a strong relationship with the community and create an enabling environment for implementing this broader set of activities.

Despite dating back over 400 years the relevance of traditional fisheries management in Aceh, Indonesia, still remains high. Aceh was, however, greatly affected by the December 2004 Indian Ocean tsunami that claimed an estimated 167,000 lives, including 14,000 fishermen and 59 of the 193 traditional marine leaders (Panglima Laot). This tragic loss of life was accompanied by a substantial loss of local knowledge, such as the locations of hazardous fishing grounds. In this study we describe an innovative project that sought to rebuild a post-tsunami fisheries sector by re-engaging and empowering the Panglima Laot. During April–June 2008 GPS (global positioning system) sounding devices were installed on 53 local fishing boats and hazardous fishing areas mapped based on local knowledge, and shared amongst fishermen. During July–December 2008 nearly five million GPS data points were collected, from which detailed bathymetric maps were produced and shared between fishermen and Aceh government officials. Significant project outputs included a map of fishing areas over 20,000 km2, which included three new seamounts, one of which expanded Aceh's provincial boundary by > 1.3 million ha, and a Panglima Laot decree that reduced fishing in hazardous areas of high coral density by 23.3%. Our findings have wide applicability. Locally, the introduction of GPS technology and sharing of traditional knowledge resulted in fishermen developing and implementing their own management strategies and demonstrating their ability to stay out of restricted areas. Provincially, this project provided a framework through which government agencies and academic institutions could effectively engage with local customary leaders and their fishing communities.

Groupers and reef octopus are economically and ecologically important predators on Indo-Pacific coral reefs and known as solitary hunters. Here we describe a highly unique and unusual observation of a behavioural non-random association between the highfin grouper (Epinephelus maculatus) and the reef octopus (Octopus cyanea) in the Great Barrier Reef. Such an observation is highly novel given that the association crosses both the phyla and the invertebrate to vertebrate divide. The present study hypothesizes that the association is non-random and potentially the result of cooperative hunting but as such this requires further evidence and testing.

Globally, introductions of non-indigenous species have caused dramatic economic and ecological damage. Most research on marine invasions has occurred in locations easily accessible by researchers, but much less is known about introductions to remote islands. In the central Pacific, Palmyra Atoll represents one of the last remaining quasi-pristine reef systems left in the world. In the 1940s the Atoll underwent extensive military modifications, potentially making it susceptible to invasive species. Here we describe the presence of five non-indigenous invertebrate and algal introductions at Palmyra, including two sponges, Haliclona (Sigmadocia) caerulea and Gelliodes fibrosa; one bryozoan; Zoobotryon verticillatum; one hydroid, Pennaria disticha and one macroalga, Acanthophora spicifera. The Hawaiian Archipelago is the most likely source of the introductions via shipping or yachting activity to the Atoll. Currently, the impacts of these introductions remain unknown although future monitoring will assess the influence of these non-indigenous species on this remote reef system.

The distribution and ecology of scleractinian corals on reef ecosystems along the coast of the State of Alagoas, north-east Brazil, were characterized. The scleractinians comprised 13 species in nine families, with five endemic corals, on the Alagoas coast. All of these species were found on reef ecosystems of two distinct geological origins. Coral reefs are predominant on the northern and central coast with banks near the beach line and distributed along the coast line, with many platform surfaces emerging during low tide. Sandstone reefs are more common along the south coast of Maceió city and the southern coast of Alagoas. These reefs were formed by old sand banks solidified through sedimentation starting from chemical reactions with calcium carbonate or iron oxide from the Quaternary period, and are generally in rows parallel to the coastline and near the outlets of rivers and estuaries. A few species including Favia gravida and Siderastrea stellata were found in the intertidal zone on top of the reef platform of both types of reefs. The other scleractinian species were observed on the reef borders where there were some inlets and channels. A larger number of coral species occur on the northern coast where the seawater is clearer throughout the year.