Science Center Objects

This study is part of the USGS Coral Reef Project.

Illustration looking obliquely at the textured seafloor off an island, and colors have been used to designate different areas.

Oblique onshore view of sea floor characterization map off Puʻukoholā Heiau National Historic Site and Kawaihae Harbor, Hawaiʻi.

The Problem

One of the strategic goals of the USGS Pacific Coral Reefs Project is to assist land-use managers in their protection efforts by establishing the geologic framework for ecosystem structure and function. Mapping of coral reefs provides important information about a number of reef characteristics, such as overall structure and morphology, abundance and distribution of living coral, and distribution and types of sediment. 

To document evidence of change in any ecosystem, one must first have a starting point—a "baseline" inventory of resources. Thematic maps providing this baseline inventory are an important tool for assessing changes in coral reef ecosystems, allowing scientists to spatially document changes in coral location, percentage of cover, and relative overall health of the system. In the past two decades, scientists and managers have recognized the lack of thematic maps for coral reefs worldwide.

Two men on stern of fishing vessel work on video camera equipment, preparing it to be launched into water.

USGS researchers prepare vertical-drop and oblique-towed video camera systems on F/V (fishing vessel) Alyce C to collect digital imagery for ground-truthing habitat maps derived from remotely-sensed data.

No single mapping approach is effective for evaluating the overall health of a reef or to determine the cause of its demise. It is only through combining techniques that scientists can establish the most complete view of a reef, one that can be used for evaluating current reef health and providing a baseline to detect future change.

The Approach

We first aim to identify innovative mapping methodologies to find the most efficient methods of mapping and remote sensing that can be used to address coral reef issues of distribution, morphology, benthic cover, and history of existing U.S. coral reef systems in the Pacific Basin. We then conduct scientific mapping of critical coral reef environments, including pristine reefs, sediment- or pollutant-impacted reefs, or those of special significance and concern such as reefs in State or National Parks, National Wildlife Refuges, or National Marine Sanctuaries. Our goals are to determine the spatial variability of the following parameters at high resolution:

Underwater photo of corals taken from a video feed, where the camera displays text on the image like date and location.

Geo-referenced underwater image of Porites species corals and navigation information from a digital-towed camera system during a ground-truthing cruise in Kaloko-Honokōhau National Historical Park, Hawaiʻi.

1. Reef tract structure, including overall morphology, rugosity, and complexity

2. Benthic habitat, including bottom type (for example, limestone or volcanic pavement, sand, mud), bottom cover (for example, coral, algae, macroalgae), and biodiversity

3. Transitions between colonized coral reef habitat and adjacent depauperate environments

The approach to these efforts relies on a combination of field measurements and laboratory studies in order to characterize coral reef habitats. We use a wide range of tools, including in-water observations made by scuba divers, high-resolution bathymetry from airborne LIDAR (LIght Detecting And Ranging, e.g., laser range-finding), airborne and space-based multispectral remote sensing imagery, underwater towed digital photo/video mapping systems, and swath acoustic seabed mapping systems.