A review of selected indicators of particle, nutrient and metal inputs in coral reef lagoon systems

This review presents environmental and biological indicators of the impact of three major categories of inputs in coral reef lagoons i.e. particles, nutrients and metals. Information was synthesized to extract well established indicators together with some interesting new concepts currently under development, and to provide the reader with an assessment of their respective advantages and drawbacks. The paper has been organized according to the capacity of three categories of indicators to respond either in a specific or a non specific way to a given source of input. The first section focuses on abiotic indicators which main interest is to respond instantaneously and in a truly specific way to a given source of input. The second and third sections present informations on bioindicators either at the sub-individual level or at the individual to community level, indicator specificity generally decreasing as a direct function of biological or ecological complexity. This review showed that even though significant work has already been done on coral reef ecosystems, much more scientific studies are still needed to answer the growing local demands for simple and truly validated tools to be used in environmental surveys. It is further stressed that, due to the biological and environmental diversity of coral reef lagoons, a preliminary step of on-site validation must be considered as an absolute prerequisite when indicators are planned to be used in the frame of a local environmental monitoring programme

Macroalgae exhibit diverse responses to human disturbances on coral reefs

Scientists and managers rely on indicator taxa such as coral and macroalgal cover to evaluate the effects of human disturbance on coral reefs, often assuming a universally positive relationship between local human disturbance and macroalgae. Despite evidence that macroalgae respond to local stressors in diverse ways, there have been few efforts to evaluate relationships between specific macroalgae taxa and local human-driven disturbance. Using genus-level monitoring data from 1205 sites in the Indian and Pacific Oceans, we assess whether macroalgae percent cover correlates with local human disturbance while accounting for factors that could obscure or confound relationships. Assessing macroalgae at genus level revealed that no genera were positively correlated with all human disturbance metrics. Instead, we found relationships between the division or genera of algae and specific human disturbances that were not detectable when pooling taxa into a single functional category, which is common to many analyses. The convention to use percent cover of macroalgae as an indication of local human disturbance therefore likely obscures signatures of local anthropogenic threats to reefs. Our limited understanding of relationships between human disturbance, macroalgae taxa, and their responses to human disturbances impedes the ability to diagnose and respond appropriately to these threats

Méthodes d’estimation des surfaces développées de coraux scléractiniaires à l’échelle d’une colonie ou d’un peuplement

This study presents an original method for the determination of the actual surface area of Scleractinian corals at colony-scale and at the scale of a whole reef. Firstly, at colony-scale, the technique consists of dipping coral colonies in a liquid paraffin bath and measuring the weight of the coral before and after the dipping. It is based on the relationship between the weight and the surface area of paraffin deposited and allows one to obtain the actual surface area of coral colonies in the laboratory. The main advantages of this method compared to others is that it uses easily obtainable materials and it is adaptable to all colony shapes. It was used on coral colonies representing the six most frequently seen colony shapes on the reefs of the island of Moorea (French Polynesia). It is shown that, within a wide range of sizes of any given shape, the relationship between vertical projection surface area and actual surface area is linear for most of the colony shapes. The shapes tested were: branching (Synaraea rus), encrusting (Montipora aequituberculata), massive (Porites lobata), sub-massive (Pocillopora verrucosa), mushroom (Fungia scutaria) and tabular (Acropora hyacinthus). Conversion indices for each shape (vertical projection surface area versus actual surface area) were determined from this preliminary study. Secondly, to estimate the actual surface area of coral colonies at the scale of the reef for nine different coral communities, the conversion indices determined above were used to convert vertical projection percent cover to actual surface area. Because of differences in shape composition among the studied coral communities, differences between communities in classical planar percentage cover are not proportional to differences observed in actual coral surface area. These results show that actual surface area may provide a more appropriate measure than planar percentage cover for future quantitative studies of coral communities.Une méthode de calcul des surfaces développées des coraux scléractiniaires est présentée. Les principaux avantages de la technique utilisée sont sa mise en œuvre à partir de matériaux d’accès facile et son adaptabilité à toutes les formes de colonies. Elle est appliquée sur les formes de colonies coralliennes les plus fréquemment rencontrées sur les récifs de l’ı̂le de Moorea (Polynésie française). Pour une gamme de taille étendue et pour chaque forme de colonies, une relation linéaire lie la surface projetée et la surface développée des colonies. Des coefficients de conversion (surface corallienne en projection plane et verticale – surface corallienne développée) sont déterminés pour chacune de ces formes. Ils sont utilisés pour évaluer le recouvrement développé de l’ensemble des colonies vivantes à l’échelle de neuf peuplements distincts. Les résultats montrent que, dans les études quantitatives des peuplements coralliens, la mesure des surfaces réelles est mieux adaptée que le classique pourcentage de recouvrement plan

Detecting the effects of natural disturbances on coral assemblages in French Polynesia: a decade survey at multiple scales.

Coral reefs in French Polynesia, just like many others throughout the world, have been subjected to several natural disturbances including 15 cyclones, seven major bleaching events, and several Acanthaster planci outbreaks since the 1980s. In order to document the effects of these perturbations on coral assemblages, we initiated a long-term monitoring program that extended over both local and regional scales. Coral cover was quantified at 20 sites situated on the outer reef slope of 13 islands. The results from the first decade (1992-2002) are analyzed and the adequacy of our approach is discussed in the context of identifying potential indicators of coral reef health. Among 13 islands in French Polynesia, only two were unaffected by natural disturbances. We found important local and regional variation in the impacts of coral bleaching and cyclones, and three major temporal trends were distinguished: 1) 10 sites where coral cover decreased in relation to the occurrence of major disturbances; 2) nine sites where coral cover increased, despite the occurrence of disturbances affecting seven of them; and 3) a site where no significant variation in coral cover was found. The responses to perturbations were different among coral genera: Acropora species were particularly susceptible to bleaching events, whereas physical damages induced by cyclones concerned mainly branching species of Acropora and Pocillopora. Thus, monitoring surveys could be improved by selecting different and complementary indicators (one on the variation in diversity, one estimating changes in the abundance/cover, and one estimating the potential for recovery), by integrating several spatial scales, and by including at least the most informative species. High frequency recordings of environmental parameters (e.g. sea surface temperature) may be also a complementary tools for identifying causal relationships between changes in coral reef community structure and the factors causing the changes

Ecological evaluation of a marine protected area network: a progressive-change BACIPS approach

International audienceMarine protected area (MPA) networks, with varying degrees of protection and use, can be use ful tools to achieve both conservation and fisheries management benefits. Assessing whether MPA networks meet their objectives requires data from Before the establishment of the network to better discern natural spatiotemporal variation and preexisting differences from the response to protection. Here, we use a Progressive-Change BACIPS approach to assess the ecological effects of a network of five fully and three moderately protected MPAs on fish communities in two coral reef habitats (lagoon and fore reef) based on a time series of data collected five times (over three years) Before and 12 times (over nine years) After the network’s establishment on the island of Moorea, French Polynesia. At the network scale, on the fore reef, density and biomass of harvested fishes increased by 19.3% and 24.8%, respectively, in protected areas relative to control fished areas. Fully protected areas provided greater ecological benefits than moderately protected areas. In the lagoon, density and biomass of harvested fishes increased, but only the 31% increase in biomass in fully protected MPAs was significant. Non-harvested fishes did not respond to protection in any of the habitats. We propose that these responses to protection were small, relative to other MPA assessments, due to limited compliance and weak surveillance, although other factors such as the occurrence of a crownof-thorns starfish outbreak and a cyclone after the network was established may also have impeded the ability of the network to provide benefits. Our results highlight the importance of using fully protected MPAs over moderately protected MPAs to achieve conservation objectives, even in complex social–ecological settings, but also stress the need to monitor effects and adapt management based on ongoing assessments

Community composition predicts photogrammetry-based structural complexity on coral reefs

International audienceThe capacity of coral reefs to provide ecosystem services, to keep their diversity and their productivity are related to their three-dimensional structural complexity. This parameter is also correlated to total fish biomass, to the general reef resilience to external stresses and to their ability to dissipate wave energy. However, information on structural complexity (also defined as reef rugosity) has been uncommonly assessed in historical monitoring programs, with the result that the long-term trend of this variable is generally unavailable. In this study, we show that it is possible to predict and hindcast the three-dimensional complexity of coral reefs by combining photogrammetry, statistical modeling and historical benthic community data. We calibrated a lasso generalized linear model to predict structural complexity obtained by 57 photogrammetry transects recorded at 13 sites around the island of Moorea (French Polynesia). Our model was able to predict structural complexity with high accuracy (cross-validated R2 = 0.81 ± 0.12). We then used our model to hindcast historical trends in 3D structural complexity using community composition data collected in Moorea from 2004 to 2017. The temporal analysis highlighted the dramatic effect of a crown-of-thorns outbreak in 2006-2009 and Cyclone Oli in 2010. These two events together reduce coral cover from ~50% to almost zero. Our model captured these effects, confirming the possibility to predict structural complexity on the basis of assemblage composition

Production of procalcitonin (PCT) in non-thyroidal tissue after LPS injection

Procalcitonin (PCT) is one of the precursors in the synthesis of calcitonin in thyroidal C-cells and other neuroendocrine cells. PCT, among other calcitonin precursors, is elevated in the serum of many conditions associated with a systemic inflammatory response syndrome, even in the absence of the thyroid gland. The aim of our study was to identify PCT-producing extrathyroidal tissues in primate sepsis. In order to induce PCT production, we treated four olive baboons ( papio cynocephalus anubis) with the endotoxin lipopolysaccharide (LPS) from s. typhimurium. We found an increase in serum PCT 3 to 5 hours after LPS injection to levels of 0.2 ng/ml, attaining a peak above 4 ng/ml PCT at 10 hours. In contrast, the untreated baboon had no detectable circulating PCT in the serum. In one animal, additional LPS boosting after 24 hours did not increase serum PCT further. Soluble proteins were extracted from different organs, fractionated by C18 extraction, and PCT was measured in an immunoluminometric assay (ILMA), which was specifically developed for this study. PCT concentrations above 0.2 ng/g of wet tissue were found in a variety of organs in LPS treated baboons, but not in the control baboon. Organs and tissues with the highest PCT concentration included liver, kidney, aorta, fat, ovaries, bladder and adrenal gland. RT-PCR confirmed an extrathyroidal origin of PCT. Importantly, CT-mRNA expression was found in liver, lung, kidney, adrenal, colon, skin, spleen, brain and pancreas. In conclusion, our data confirm previous findings in hamsters, indicating an extrathyroidal origin for PCT in sepsis. Our primate model offers a valuable tool for further investigation of PCT's pathophysiological role and its immunoneutralization as a therapy for sepsis

Contrasting patterns of mortality in Polynesian coral reefs following the third global coral bleaching event in 2016

In 2016, many tropical corals worldwide were exposed to anomalously high temperatures due to one of the strongest El Nino events ever recorded. Bleaching impacts were reported on 23 islands within three archipelagos of French Polynesia (Tuamotu, Society and Marquesas archipelagos). A detailed study on the effects of elevated temperatures on corals was performed on five islands (Mo'orea, Makemo, Hikueru, Marutea and Katiu) and revealed contrasting patterns of coral bleaching responses between Mo'orea (Society Archipelago) and the four islands of the Tuamotu Archipelago. While some reefs from the Tuamotu lost more than half of their coral cover, in Mo'orea, less than 1% mortality was recorded 6 months after bleaching. During the 2016 bleaching event, certain reefs at 12 m depth in the outer reef habitats were not exposed to sufficiently long high-temperature periods (heat stress not exceeding 1.1 degrees C weeks in Mo'orea) to cause large-scale bleaching-related coral mortality. In contrast, other reefs in the Tuamotu Archipelago had DHW reaching up to 9.2 degrees C weeks and experienced severe mortality (up to 71%). Our study showed how differential heat stress exposure across reefs of French Polynesia led to different impacts on corals. Until now, Mo'orea reefs have been spared abnormally high temperatures leading to mortality and should be considered an important source of larvae to help maintain reefs on the surrounding islands