Alongside climate change and habitat degradation, eutrophication poses a significant threat to coral ecosystems worldwide.  The influx of land-based pollutants into the sea leads to increased nutrient content and decreased salinity. This decreases coral health and increases their susceptibility to disease, while promoting the growth of macroalagae, causing ecosystem phase shifts from biodiverse, oligotrophic reef communities to eutrophic macoalgae-dominated reefs. Despite these threats facing coral, there are generalist species that seem to be remarkably resistant to such anthropogenic stressors and thrive in suboptimal habitats where no other corals are found. Oulastrea crispata, the zebra coral, is tolerant to low temperatures and low-light, turbid environments and can be found in near-shore, low salinity environments. While its native range is in the central-Indo-Pacific, its distribution stretches to temperate non-reefal habitats. Its flexibility in feeding and reproductive strategies, as well as ability to colonise various substrates, including artificial reefs means that it is a successful coloniser and has been recorded as an invasive species in Korea and the Mediterranean Sea. As O. crispata encounters diverse and often harsh environments, this makes it ideal model for studying the impacts of human-induced stressors on coral adaptation and responses to climate change, and their corresponding effect on the ecosystem. O. crispata have a wide distribution along the high urbanised coastlines in Hong Kong and have been found to exist in across a broad eutrophication gradient, due to influence of effluent from the Pearl River estuary as well as the influx of oligotrophic oceanic waters. To identify how O. crispata can be successful in disturbed environments, we investigated their genomic responses to eutrophication and other anthropogenic stress across their gradient of environmental conditions in Hong Kong. We used RAD sequencing to obtain information about their genome-wide variation and assessed their genetic diversity and population structure. In addition, we used seascape genomics approaches to detect putative adaptive genetic loci that allow them to cope with adverse conditions. By understanding the adaptive potential of this generalist species to polluted environments, we can better predict their responses to future anthropogenic changes and the subsequent impacts on the ecosystem. Insight from such regional studies can be used to inform conservation strategies to mitigate the impacts of habitat loss and improve ecosystem resilience as anthropogenic stressors become increasingly pronounced in coastal reef ecosystems globally.
 

eutrophication, seascape genomics, coral reefs, genetic diversity, anthropogenic changes