Climate Change and Land-use Histories

Science Center Objects

We are developing new and unique oceanographic and environmental archives from coral skeleton records to better understand the compounding effects of land-use and environmental change on coral reef health.

Underwater photograph of a coral reef.

Shimmering and bubbles indicate active freshwater discharging from the submarine groundwater vents along shallow reefs in west Maui.  Corals are degraded and there is very little evidence of live coral cover. Photo credit: Peter Swarzenski, USGS

The Problem

In addition to overfishing, physical damage, and coastal development, declining water quality is one of the most serious and sustained threats to coral reefs and is thought to be a primary cause of the global decline in shallow coral reefs. Isolating the effects of water quality stressors is difficult without determining the physical and biological controls on reef health. However, to evaluate recent trends and establish links to environmental and land-use change, there is a need to put these changes into a temporal and spatial context in order to identify thresholds and ranges of variability in the environment.

Computerized tomography image of a coral core section next to its corresponding plot of annual density values.

Coral core section (left panel) from Guam, showing annual growth bands and the corresponding annual density values (right panel) for the upper 24 years. In the core section, a high- and low-density couplet constitutes an annual growth band.
Image from Prouty et al., 2014

Our Approach

By measuring both physical changes (such as bioerosion, calcification, and growth rate) and chemical variations, records of climate change and land-use histories can be developed to supplement disperse observational networks and offer an accessible source of hydrologic, environmental, and land-use information in locations where instrumental records are not available. We are conducting innovative research to develop new and unique oceanographic and environmental archives from coral skeleton records to better understand the compounding effects of land-use and environmental change on coral reef health. 

CT scan and photograph of a coral core section, side-by-side.

Computerized tomography (CT) images and respective photographs of coral core showing the high degree of bioerosion and loss of calcium carbonate skeleton due to nutrient-driven bioerosion. Image from Prouty et al., 2017

Specifically, we are conducting applied research to strategically address scientific knowledge gaps that impede informed management decisions related to planning and implementing activities in priority coral reef ecosystems and associated watersheds, such as identifying the causes and sources of pollution or estimating load reductions expected from implementation of specific management measures. We apply recently developed nutrient proxies to provide pre-instrumental records of nutrient loading to coral reefs in impacted sites. When these results are coupled to records of reef growth, we can develop a matrix of susceptibility in the context of nutrient loading and changes to carbonate chemistry. We aim to introduce coral-derived time-series information into monitoring and future management decisions to reduce and prevent land-based sources of pollution, including forecasting future impacts and response to load reductions expected from implementation of specific management tactics.

Caption for large image at top of page: Photograph of Asan-1 core (1.17 m in length) taken for image analysis using a Geotek Multi-Sensor Logger (MSL) system.  Age dates were assigned based on year of collection, tissue layer, and band counting using annual density growth patterns captured in CT imagery. Image from Prouty et al., 2014

Please also see the associated efforts on the Coral Reef Ecosystem Studies (CREST) Project website: