Periodic Reporting for period 1 - POPAMA (Effects of nutrient pollution on parrotfish in Mayotte : From physiological to microbial scales)
Reporting period: 2023-01-01 to 2024-12-31
Coral reefs are in precipitous decline worldwide due to a number of global stressors and local human impacts. Nutrient pollution emanating from sewage outfalls and coastal runoffs is often associated with the deterioriation in the health of coral reef organisms. However, the mechanisms underlying the ecological impacts of pollution remain poorly understood, while they are critical to develop meaningful conservation strategies to preserve reef ecosystems. There is especially a need to investigate how nutrient pollution can affect the microbiomes of ecologically and economically important reef fishes such as parrotfishes, which are suggested to vector microbes to corals and enhance coral dysbiosis susceptibility when coupled with pollution. The Research Action POPAMA led by a multidisciplinary team within MARBEC laboratory (CNRS & UM) integrates approaches from microbial ecology and physiology to investigate to what extent nutrient pollution alter parrotfish microbiomes, whether these changes result in differences in parrotfish physiology, and the potential cascading effects on coral microbiomes and health.
This Action entailed one major field campaign which was conducted in Mayotte (Indian Ocean, France) at the end of the 2023 rainy season. Mayotte is home to > 330 000 citizens, with 1/3 lacking access to proper sanitation systems. We targeted 6 reef sites characterized by a gradient of nutrient pollution. Our sampling effort included 48 individuals of the widely distributed parrotfish species Chlorurus sordidus, ensuring all necessary samples were collected for comprehensive physiological and microbial assays on each fish. Beside fish samples, we collected additional samples to characterize environmental microbiomes, such as water, sediment, turf algae along with tissue samples of Porites colonies. Our findings provide novel insights into the impacts of nutrient pollution on coral reefs, including drastic shifts in the diversity and structure of bacterial planctonic and benthic communities as well as in the gut microbiomes of parrotfish. In addition, our results underline habitat (fringing versus barrier reefs) as important driver of parrotfish gut microbiota and physiological traits, including mineral content in fish tissue and cortisol level – further highlighting the relevance of comprehensive studies for a deeper understanding of organism health.
The complementary approaches linking community ecology, microbial analyses and physiology pave the way for quantitative predictions regarding the health of key organisms in coral reef ecosystems. Our research highlights the importance of conducting surveys on all the key ecosystem compartments (water, sediment, algae, corals and fishes) to get a broader view of the impacts of nutrient pollution on the reef ecosystems – from macro to microbial scales. Moreover, these findings highlight the importance of conducting studies involving both physiology and microbiology to assess the impacts of stressors on animals. Beyond understanding these effects, such an approach also provides deeper insights into coral and fish biology, offering a comprehensive perspective on the overall health of individuals.
Our findings will be of direct relevance and interest to a broad range of scientists concerned with biodiversity and ecosystem functioning, fisheries management and nutrition as well as conservationists, ecosystem managers seeking to understand the role of trophically-mediated microbial dynamics within increasingly degraded ecosystems. Upon publications of our research, our findings will be communicated to the Indian Ocean Health Agency and appropriate stakeholders (i.e. Parc Marin de Mayotte, FRB). Importantly, Mayotte was recently struck by Hurricane Chido in mid-december 2024. In response, the French government, through the Office National de la Biodiversité (OFB) and the Parc Marin de Mayotte, is planning to assess its impact on lagoon biodiveristy. Our data from 2023 will be useful to establish a pre-hurricane baseline.
Our findings will be of direct relevance and interest to a broad range of scientists concerned with biodiversity and ecosystem functioning, fisheries management and nutrition as well as conservationists, ecosystem managers seeking to understand the role of trophically-mediated microbial dynamics within increasingly degraded ecosystems. Upon publications of our research, our findings will be communicated to the Indian Ocean Health Agency and appropriate stakeholders (i.e. Parc Marin de Mayotte, FRB). Importantly, Mayotte was recently struck by Hurricane Chido in mid-december 2024. In response, the French government, through the Office National de la Biodiversité (OFB) and the Parc Marin de Mayotte, is planning to assess its impact on lagoon biodiveristy. Our data from 2023 will be useful to establish a pre-hurricane baseline.