Terrestrial pollution versus global warming: what drives coral annual extension in the Anthropocene era? - A case study in Chuuk lagoon, Micronesia

Abstract

Terrestrial pollution and CO2-driven global warming are main threats to coral reefs ecosystems. Previous studies revealed the contrasting responses of reef building coral species to human-led changes. Increased sea surface temperature (SST) reduced coral annual extension in the Red Sea, whereas, terrestrial pollution increased extension in Indonesia. These two concurrent threats raise some questions about coral annual extension in the Anthropocene. Coral reefs in Chuuk lagoon have suffered from high anthropogenic impacts through the WWII and subsequent population growth, additionally, the SST increased by about 0.5 °C over the same period. To assess the relative importance of these two factors in coral annual extension, we collected two coral cores of Porites sp. at Newman and Nepukos which are located at Weno island in Chuuk lagoon, Federated States of Micronesia. Age estimation based on band counts of x-radiograph indicated the first core encompasses the time-period 1938-2013 and the second core is estimated to include the entire 20th century. According to correlation analyses, coral annual extension showed no correlation with SST and population density, however, significantly correlated with precipitation on the most recent half of the record. While the second core is still being analyzed, the preliminary results indicate increased human population and concomitant deforestation caused an influx of terrestrial pollutants and subsequently affect coral annual extension rather than global warming nearshore reef.