Rapid Oceanic Response to Tropical Cyclone Oli (2010) over the South Pacific

International audienceThe effect of Tropical Cyclone Oli (2010) on the ocean is investigated using a variety of measurements. In situ temperature measurements on the cyclone track are available via the Centre de Recherches Insulaires et Observatoire de l'Environnement (CRIOBE) array of probes. This reflects an extreme fluctuation of the temperature some 18 h after the cyclone, lasting only 12 h and exceeding 38C in amplitude. This study interprets this extreme fluctuation in terms of enhanced mixing associated with the time-dependent inertial currents due to the cyclonic winds. The authors show, using Lagrangian simulations, that this rapid event is compatible with the severe length-scale shortening observed in Lagrangian simulations

Deep heat: a comparison of water temperature, anemone bleaching, anemonefish density and reproduction between shallow and mesophotic reefs

French Polynesia is experiencing increasing coral bleaching events in shallow waters triggered by thermal anomalies and marine heatwaves linked to climate change, a trend that is replicated worldwide. As sea surface thermal anomalies are assumed to lessen with depth, mesophotic deep reefs have been hypothesized to act as refuges from anthropogenic and natural disturbances, the ‘deep reef refugia hypothesis’ (DRRH). However, evidence supporting the DRRH is either inconclusive or conflicting. We address this by investigating four assumptions of the DRRH focusing on the symbiotic association between anemones and anemonefish. First, we compare long-term temperature conditions between shallow (8 m) and mesophotic sites (50 m) on the island of Moorea from 2011–2020. Second, we compare the densities of the orange-fin anemonefish, Amphiprion chrysopterus between shallow and mesophotic (down to 60 m) reefs across three archipelagos in French Polynesia. Finally, we compare the percentage of anemone bleaching, as well as anemonefish reproduction, between shallow and mesophotic reefs. We found that the water column was well mixed in the cooler austral winter months with only a 0.19 °C difference in temperature between depths, but in the warmer summer months mixing was reduced resulting in a 0.71–1.03 °C temperature difference. However, during thermal anomalies, despite a time lag in warm surface waters reaching mesophotic reefs, there was ultimately a 1.0 °C increase in water temperature at both 8 and 50 m, pushing temperatures over bleaching thresholds at both depths. As such, anemone bleaching was observed in mesophotic reefs during these thermal anomalies, but was buffered compared to the percentage of bleaching in shallower waters, which was nearly five times greater. Our large-scale sampling across French Polynesia found orange-fin anemonefish, A. chrysopterus, in mesophotic zones in two high islands and one atoll across two archipelagos, extending its bathymetric limit to 60 m; however, orange-fin anemonefish densities were either similar to, or 25–92 times lower than in shallower zones. Three spawning events were observed at 50 m, which occurred at a similar frequency to spawning on shallower reefs at the same date. Our findings of thermal anomalies and bleaching in mesophotic reefs, coupled with mainly lower densities of anemonefish in mesophotic populations, suggest that mesophotic reefs show only a limited ability to provide refugia from anthropogenic and natural disturbances

Very high resolution mapping of coral reef state using airborne bathymetric LiDAR surface-intensity and drone imagery

International audienceVery high resolution (VHR) airborne data enable detection and physical measurements of individual coral reef colonies. The bathymetric LiDAR system, as an active remote sensing technique, accurately computes the coral reef ecosystem’s surface and reflectance using a single green wavelength at the decimetre scale over 1-to-100 km2 areas. A passive multispectral camera mounted on an airborne drone can build a blue-green-red (BGR) orthorectified mosaic at the centimetre scale over 0.01-to-0.1 km2 areas. A combination of these technologies is used for the first time here to map coral reef ecological state at the submeter scale. Airborne drone BGR values (0.03 m pixel size) serve to calibrate airborne bathymetric LiDAR surface and intensity data (0.5 m pixel size). A classification of five ecological states is then mapped through an artificial neural network (ANN). The classification was developed over a small area (0.01 km2) in the lagoon of Moorea Island (French Polynesia) at VHR (0.5 m pixel size) and then extended to the whole lagoon (46.83 km2). The ANN was first calibrated with 275 samples to determine the class of coral state through LiDAR-based predictors; then, the classification was validated through 135 samples, reaching a satisfactory performance (overall accuracy = 0.75)

Les récifs coralliens: Un tiers des espèces marines sont-elles menacées?

International audienceDans la zone intertropicale des trois océans, les formations coralliennes couvrent actuellement quelques 600 000 km 2 . On estime qu’un tiers des espèces marines vivent dans les récifs coralliens. Mais cet écosystème marin serait le premier à souffrir du changement climatique. Qu’en est-il exactement ? Quels sont les risques de disparition d’espèces

Prevalence, persistence and impacts of residual fishing hooks on tiger sharks

International audienceWe used long-term observations of 55 individually identified tiger sharks (Galeocerdo cuvier) at a shark eco-tourism site off Tahiti to estimate the prevalence, retention times and impacts of residual hooks and trailing line resulting from fisheries interactions. Thirty-eight percent of tiger sharks had at least one fisheries interaction resulting in retained hooks during the 8-year observation period. Both stainless-steel and corrodible hooks had a retention half-life of less than 1year, and all corrodible hooks were shed within 2.5 years whereas firmly embedded stainless-steel hooks persisted for at least 7.6 years and are potentially retained for the lifetime of the shark. The presence of residual hooks and trailing line did not impact tiger shark growth suggesting that sharks were able to feed normally despite trailing gear. However, only a single internally-hooked sharks trailing line was observed suggesting their survival may perhaps be lower than externally-hooked individuals. Hook-retention data obtained from this study could be extrapolated to other warm water shark species that are difficult to observe in their natural habitats (e.g. oceanic whitetip shark, Carcharhinus longimanus)

Understanding the Spatio-Temporal Response of Coral Reef Fish Communities to Natural Disturbances: Insights from Beta-Diversity Decomposition.

Understanding how communities respond to natural disturbances is fundamental to assess the mechanisms of ecosystem resistance and resilience. However, ecosystem responses to natural disturbances are rarely monitored both through space and time, while the factors promoting ecosystem stability act at various temporal and spatial scales. Hence, assessing both the spatial and temporal variations in species composition is important to comprehensively explore the effects of natural disturbances. Here, we suggest a framework to better scrutinize the mechanisms underlying community responses to disturbances through both time and space. Our analytical approach is based on beta diversity decomposition into two components, replacement and biomass difference. We illustrate this approach using a 9-year monitoring of coral reef fish communities off Moorea Island (French Polynesia), which encompassed two severe natural disturbances: a crown-of-thorns starfish outbreak and a hurricane. These disturbances triggered a fast logistic decline in coral cover, which suffered a 90% decrease on all reefs. However, we found that the coral reef fish composition remained largely stable through time and space whereas compensatory changes in biomass among species were responsible for most of the temporal fluctuations, as outlined by the overall high contribution of the replacement component to total beta diversity. This suggests that, despite the severity of the two disturbances, fish communities exhibited high resistance and the ability to reorganize their compositions to maintain the same level of total community biomass as before the disturbances. We further investigated the spatial congruence of this pattern and showed that temporal dynamics involved different species across sites; yet, herbivores controlling the proliferation of algae that compete with coral communities were consistently favored. These results suggest that compensatory changes in biomass among species and spatial heterogeneity in species responses can provide further insurance against natural disturbances in coral reef ecosystems by promoting high levels of key species (herbivores). They can also allow the ecosystem to recover more quickly

A qualitative study on experiences of persons with schizophrenia in oral-health-related quality of life

International audienceOur study aimed to explore the views and experiences in oral health and oral-health-related quality of life (OHRQoL) of persons with schizophrenia (PWS) in order to expand the understanding of the factors that either limit or facilitate their healthcare pathway, which can ultimately optimize their oral health and/or OHRQoL. A qualitative study was conducted in France in the Côte d’Or department (530 000 in habitants) centered on PWS’s perceived meanings regarding oral health or OHRQoL, and semi-structured individual interviews were used. A conventional content analysis approach was chosen in order to highlight unrevealed themes. A sample of 20 PWS (12 males; 8 females) with a median age was 45.8 (± 9.5) were recruited to assess views and experiences regarding OHRQoL, which were focused on three dimensions: an individual dimension related to experience of “oral symptoms”, a second dimension related to experience of “stress and its management”, and a third related to “Autonomy dimension in oral health”. We showed that PWS clearly expressed their mental representations of oral health and OHRQoL. This study supports that PWS were able to define their needs and had the ability to discuss their oral health and OHRQoL. These finding could be used to support specific interventions for this population to better manage the negative impact of antipsychotics and help them to consult dentists on a regular basis

Anticholinergic drugs and oral health-related quality of life in patients with schizophrenia: a pilot study

The aim of this study was to explore, in a sample population of people with schizophrenia (PWS), the role of the anticholinergic burden on the perception of oral health-related quality of life (OHrQoL) in France

Anticholinergic drugs and oral health-related quality of life in patients with schizophrenia: a pilot study

International audienceAbstract Objective The aim of this study was to explore, in a sample population of people with schizophrenia (PWS), the role of the anticholinergic burden on the perception of oral health-related quality of life (OHrQoL) in France. Methods A pilot study was performed between March 2014 and January 2016. PWS were recruited from a population in Côte d’Or department in France. Dental status was investigated using the Decayed, Missing, or Filled Teeth (DMFT) index, the Xerostomia Index (XI), and the Global Oral Health Assessment Index (GOHAI) for OHrQoL. The anticholinergic impregnation score was recorded using the anticholinergic impregnation scale (AIS). Results A sample of 62 people was selected. The DMFT score was 16.5± 8.7, the XI score was 22.9±7.8, the GOHAI score was 43.0±8.8, and the AIS score was 3.1±2.8. In total, 169 drugs were prescribed to the people of our sample, and 114 different anticholinergic drugs were observed. The most frequently used anticholinergic drugs (51.40%), in the study had a low antimuscarinic potency (1 point according to AIS scale). The multiple linear regression model showed that the OHrQoL scores were significantly lower when the DMFT scores, XI score, and anticholinergic scores were high. Conclusions This pilot study highlighted the potential role of the anticholinergic burden on the OHrQoL of PWS. A study with a validated specific scale for the OHrQoL and a standard anticholinergic burden scale should be conducted to clarify the role of anticholinergic drugs on the OHrQoL for PWS

Synchrony patterns reveal different degrees of trophic guild vulnerability after disturbances in a coral reef fish community

International audienceAim: Chronic anthropogenic stressors are increasing in intensity, making ecosystems more vulnerable to acute disturbances. Recovery processes are not always well understood due to the complexity of ecosystems and the lack of appropriate indicators. Temporal synchrony is a valuable metric for assessing whether fluctuations in abundance of different species are homogeneous or heterogeneous over time. Theoretically, a great diversity of responses by species facing disturbances is associated with a stable ecosystem, with species turnover guaranteeing the persistence of key ecological processes. We analysed the fluctuations of synchrony of a fish community to assess its resilience in an ecosystem exposed to various disturbances.Location: Moorea (French Polynesia).Methods: Using one of the longest time series available for coral reefs (ca. 35 years), we examined the variations in substrate cover, and the abundance, synchrony and composition of different fish trophic guilds. Multivariate analyses involving synchrony were used to determine the stability of trophic guilds.Results: Changes in fish community composition indicated incomplete taxonomic resilience. However, community synchrony was lower during periods of low coral cover, indicating greater response diversity, while total fish abundance remained fairly stable. Synchrony drop was due to relationships with coral cover that differed by trophic guild, or the differences in species responses within guilds. Some guilds such as sessile invertebrate feeders exhibited a strong homogeneity of response over time, indicating a greater vulnerability. We also highlighted that various types of disturbances had different effects on the synchrony of particular guilds.Main conclusions: The fish community appeared functionally resilient, with stability of total abundance and most trophic guilds. This could be a factor explaining the rapid recovery of Moorea's coral reefs from disturbances. However, the homogeneous responses of some fish groups to disturbances may compromise the reef recovery potential on the long term if disturbances become more frequent