The effect of nutrient and temperature changes on coral reef development in the Coral Sea over 12 Ma

点击翻译按钮获取中文摘要

Coral reefs support the most sophisticated low-latitude ecosystem and affect the lives of millions of people who depend on them for survival. However, coral reefs worldwide are experiencing a decline. Anthropogenically driven global changes, such as global warming, ocean acidification, and deteriorating water quality (eutrophication), have been identified as possible culprits in this demise. However, the interplay of these factors is unknown. As modern coral reefs developed over geological time scales, one issue is the lack of long-term records of SST and productivity from coral growing regions during the Neogene. Together with my co-workers I studied the history of corals reefs from the Coral Sea. It is published that coral reefs expanded until the Late Miocene (10-11 Ma). Then, between 10-6 Ma, the reefs disappeared and did not re-appear until the Mid-Pliocene warm period (3.0-3.5 Ma). Previous research hypothesized that the onset of cold, nutrient-rich conditions during the Late Miocene drove the loss of reefs. My research shows that instead of being a colder, nutrient-rich environment than during the Late Miocene, temperatures were warmer compared to the modern reef setting and nutrient poor. The initial project results show that it is necessary to understand what happened during the Mid-Early Miocene to understand the changes during the Late Miocene. To do this we will look at Site U1464 and outcrop samples from the NW Shelf of Australia. Beginning around 20-18 Ma one of the largest Neogene reef developed on the NW-Shelf before disappearing at 11-6 Ma. Changes in SST, nutrients and local conditions are thought to drive the coral reef loss. In this project we will use biomarkers (TEX86 and Aliphatic lipids) to reconstruct changes in SST between 18-6 Ma. Therefore, we will look both at the loss of one of the largest Neogene reef systems during the Late Miocene but also look at conditions during the start and apex of the NW Shelf barrier reef. By doing so we hope to understand a number of major questions (1) Did global changes cause the loss of coral reefs across the Indo-Pacific during the Late Miocene? Or was the loss of reefs driven by more local changes? (2) What was the magnitude of the SST change across the Mid-Miocene Climatic Optimum when the reefs were flourishing? Reconstructing numerous events when coral reefs appear and disappear will give us a greater understanding on what drives coral reef growth and retreat on geological timescales. This will help to better understand the impact of future climate change on the reef systems.