Trait-based approaches reveal that deep reef ecosystems in the Western Indian Ocean are functionally distinct

Tropical deep reefs (>30 m) are biologically and ecologically unique ecosystems with a higher geographic reach to shallow (<30 m) reefs. Yet they are poorly understood and rarely considered in conservation practices. Here, we characterise benthic and fish communities across a depth gradient (10–350 m) in remote coral atolls in Seychelles, Western Indian Ocean. Using taxonomic and trait-based approaches we present the taxonomic and functional composition of shallow and deep reef communities, with distinct communities and traits dominating different depths. Depth-related changes in community metrics (taxa richness, abundance and biomass) and functional diversity metrics (richness, dispersion, and evenness) indicate complex relationships across different biological components (fish, benthos) that differ between shallow and deep reefs. These in turn translate into different patterns of reef resilience against disturbance or species invasions with depth. Notably, deep reefs host on average fewer and less abundant taxa but with higher functional contribution and originality scores, some of which are of conservation concern. Overall, the results highlight the unique nature of deep reefs that requires their explicit consideration in conservation and management activities

Review of fisheries and management of sea cucumbers in the Indian Ocean

Several sea cucumber species (Echinodermata: Holothuroidea) are fished, mostly for export of the dried product for Oriental consumers. Previous studies had analysed the historical trends at the world-scale until 2014. In the Western Indian Ocean (WIO) holothurian fisheries have a long history and several programmes have tried to ameliorate their management. Information has been recently gathered through a questionnaire and access to the most recent, yet unpublished available data (2015 to 2021) from different countries, through the evaluation of catches and/or processed product, present management systems, the imports of beche de mer and other products from Indian Ocean (IO) countries into the major market hub of Hong Kong SAR, and the Food and Agricuture Organisation (FAO) yearly statistics. The results are first presented for WIO countries, highlighting recent improvements in management. Imports from 16 WIO countries into the Hong Kong market (2017-2020 data) indicate the importance of the hub. The FAO world statistics are used to present the changes for the last few years, concentrating on the WIO countries. The recent trends show that demand for holothurians is still very high. Inconsistencies in the unit used in the reported statistics (fresh or dry weight) exist, and this needs to be addressed. The national data should be collected at the species level, to be able to follow the changes and the stock status. A regional approach is needed to encourage use of comparable management tools and follow future trends

Using Titration to Estimate Rate Law Parameters of the Reaction of Sodium Hydroxide and Ethyl Acetate

Determination of rate expression and rate law parameters i.e. rate constant and reaction orders of any reaction is an important step to design any type of reactors. In this research rate law parameters of the reaction of sodium hydroxide and ethyl acetate were determined using titration to measure final concentration of the limited reactant which is sodium hydroxide in this reaction, while the reaction was carrying out i.e. simultaneously. The standard solution used in the titration is hydrochloric acid. The usefulness of this technique is that the concentration at the time of measuring would be read and registered. Thus, accurate results could be obtained. After the final concentration being measured, rate of reaction was calculated as the difference between initial concentration and final concentration dividing by time of reaction. Then by extrapolating two rates at two different initial concentrations to zero time initial rate was calculated. Finally, several initial rates at different initial concentrations of sodium hydroxide and ethyl acetate were used to determine the rate law parameters using linearized least squares analysis method. According to this method the value of rate constant is about 0.11 L/mol.sec at 32◦C and the reaction is first order with respect to each reactant

The commercially important shoemaker spinefoot, Siganus sutor, connects coral reefs to neighbouring seagrass meadows

Spatial management of fish populations can potentially be optimized by determining the area of influence of a particular species. We performed an acoustic tagging study implemented on Denis Island in the Seychelles to assess the area of influence of the heavily targeted shoemaker spinefoot, Siganus sutor. We investigated whether this species acts as a mobile link between coral patches and seagrass meadows, and whether their movements differed between day and night. The study incorporated an array of 22 acoustic stations deployed within dense coral patches, seagrass meadows and mixed habitats of both seagrass and coral. Fifteen S. sutor carrying internal acoustic tags were monitored from November 2016 until May 2017. Detection patterns revealed them to be diurnal herbivores, with only rare nocturnal movements. Home-range estimates showed that individuals differed in their spatial range extents and habitats used, covering ~15% of the total shallow subtidal coastline of the island. However, they displayed very small daily movements

Long-term persistence of large dugong groups in a conservation hotspot around Hawar Island, Kingdom of Bahrain

1. Predictable aggregations of large marine mammals are valuable conservation targets, but aggregated populations can also be exposed to site-level threats.2. The globally vulnerable Dugong dugon has a wide distribution but is found in large numbers mainly in Australia and the Arabian Gulf. Though Australian dugong populations are well studied, much less is known of the dugongs in the Arabian Gulf.3. The spatial and temporal persistence of dugongs around Bahrain, with a focus on large dugong groups (>50 dugongs), was determined using an occupancy modelling framework supported by historical records, structured interviews, citizen science network reports, and small-scale boat and unmanned aerial vehicle surveys.4. Historical records and current distributional studies confirmed that large dugong groups have been reliably sighted around Hawar Island (Bahrain) since at least 1986, forming large, clumped groups that persist almost year round. The largest recorded so far in the world, these fluid groups (maximum of similar to 700 dugongs) account for similar to 60% of the dugongs found in Bahrain and similar to 12% of all dugongs in the Arabian Gulf.5. The delineated occupancy core area of large dugong groups (similar to 145 km(2)) straddles the Bahrain-Qatar border, reflecting the transboundary nature of these groups.6. Careful management of human-induced stressors (in particular, fishing, boating, and coastal development) combined with regular monitoring of Hawar Island's large dugong groups and their seagrass habitat is critical to safeguard this globally important population.7. The effectiveness of any conservation management is predicated on strengthening cooperation among all range states in the Arabian Gulf. A key recommendation of this study is to establish a regional network of marine protected areas encompassing core aggregation sites for dugongs, particularly the Hawar Islands in Bahrain, the north-western waters of Qatar, Marawah Island in the United Arab Emirates in addition to the shallow waters between Saudi Arabia, Qatar, and United Arab Emirates

Herbivory in a subtropical seagrass ecosystem: separating the functional role of different grazers

Seagrass meadows provide many important ecosystem services, but they are threatened by human activities and are in decline globally. In particular, eutrophication arising from human activities promotes algal growth, which negatively affects seagrass. Herbivores consume algae and can, therefore, reduce eutrophication effects, but they may also consume seagrass. Little is known, however, about grazer-epiphyte-seagrass interactions in subtropical seagrass in the Indo-Pacific. We used a 5 wk exclusion experiment to quantify the influence of different grazers in seagrass (dominated by Zostera muelleri) in Moreton Bay, eastern Australia. Our results show that herbivory does indeed affect seagrass-epiphyte dynamics in this region and that different grazers can exert different effects in seagrass ecosystems. In particular, exclusion of small mesograzers (i.e. amphipods and juvenile shrimp) caused epiphyte biomass to increase by up to 233%. Exclusion of medium mesograzers (i.e. small fish and prawns) resulted in increases of up to 10% in seagrass cover, 53% in shoot height and 29% in shoot density. Large mesograzers (i.e. adult fish) and macrograzers (i.e. turtles and dugong) did not appear to play a role in the study system. These results demonstrate that mesograzers can be important in controlling epiphytic algae in subtropical Indo-Pacific seagrass, and show that different mesograzers can affect seagrass-epiphyte dynamics in different ways. It is critical that the functional effects of different herbivores be considered when implementing programs for seagrass conservation and restoration

Climate impacts alter fisheries productivity and turnover on coral reefs

Alteration of benthic reef habitat after coral bleaching and mortality induces changes in fish assemblages, with implications for fisheries. Our understanding of climate impacts to coral reef fisheries is largely based on fish abundance and biomass. The rates at which biomass is produced and replenished (productivity and turnover) are also important to sustaining fisheries, yet the responses of these metrics following bleaching are largely unknown. Here, we examine changes in fish productivity and turnover after mass coral bleaching events in Seychelles, on reefs that were recovering to coral-dominated habitats and those that shifted to macroalgae-dominated regimes. Productivity of fish assemblages increased on all recovering reefs, particularly on fished reefs resulting in levels similar to protected reefs 19 years after bleaching. Herbivore-detritivores, such as scraping and excavating parrotfish, appeared to drive biomass production through increased abundance on recovering reefs. Productivity on regime-shifted reefs remained stable at 1994 levels in fished areas, with increases observed on protected reefs. Large increases in browser productivity (particularly on protected reefs), combined with increases for invertivores, maintained post-bleaching productivity on macroalgal reefs. For all diet groups, net turnover was generally higher on fished regime-shifted reefs than on recovering reefs, suggesting fish biomass is more readily replenished on macroalgal reefs. Reef structural complexity was a positive predictor of productivity for all diet groups. These findings indicate that post-bleaching reef fish productivity is strongly influenced by benthic recovery trajectories, and demonstrates the importance of herbivore and invertivore species in sustaining small-scale inshore fisheries following climatic disturbances