Nearshore Water Quality and Coral Health Indicators Along the West Coast of the Island of Hawaiʻi, 2010–2014

Open-File Report 2020-1128
Prepared in cooperation with the National Park Service
By: , and 


  • Document: Report (20 MB pdf)
  • Data Releases:
    • Data Release - Coral cover and health determined from seafloor photographs and diver observations, West Hawai'i, 2010-2011
    • Data Release - Nearshore water properties and estuary conditions along the coral reef coastline of west Hawaii Island (2010-2014)
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Coral reefs worldwide are experiencing rapid degradation in response to climate and land-use change, namely effects of warming sea-surface temperatures, contaminant runoff, and overfishing. Extensive coral bleaching caused by the steady rise of sea-surface temperatures is projected to increase, but our understanding and ability to predict where corals may be most resilient to this effect is limited owing to a lack of knowledge of nearshore habitat conditions and the role of compromised coral health in preconditioning bleaching vulnerability. On high islands and most atolls, fresh to brackish groundwater discharges to the coast through the beach face and seafloor, where it mixes with marine waters and commonly creates cool estuarine nearshore waters that are important to wildlife and ecosystem services that benefit people. Here, we summarize results of a study to evaluate the ecosystem services and effects of groundwater on coral reef health and the potential role of groundwater to maintain cold-water refugia that can buffer corals from thermal stress during temperature maxima. Across 75 kilometers of the west coastline of the Island of Hawaiʻi, paired time-series and discrete measurements of water quality, coral-community and colony size structures, and coral health indicators, including bleaching, at 33 stations grouped into 12 study areas were made from July 2010 to December 2013. The results show that nearshore water temperatures are depressed by groundwater across extensive areas of the nearshore. Persistent cold-water refugia ranging from 1 to 5 degrees Celsius below surrounding marine water temperatures are shown to be associated with identified groundwater inputs. Significant correlations were found between metrics of coral health and water temperature. Because areas of temperature refugia were notable along the west coast of the Island of Hawaiʻi and are identified by ecologists as increasingly important to valued wildlife, improved understanding of groundwater flux to the long-term resilience of coral reefs is likely important. In particular, evaluating the extent that the magnitude and timing of groundwater discharge across the nearshore mitigate thermal bleaching stress may help inform the fate of coral reefs projected to experience rising sea-surface temperatures worldwide.

Suggested Citation

Grossman, E.E., Marrack, L., and vanArendonk, N.R., 2021, Nearshore water quality and coral health indicators along the west coast of the Island of Hawaiʻi, 2010–2014: U.S. Geological Survey Open-File Report 2020–1128, 45 p.,

ISSN: 2331-1258 (online)

Study Area

Table of Contents

  • Abstract
  • Introduction
  • Methodology
  • Results and Discussion
  • Summary
  • References Cited
  • Appendixes
Publication type Report
Publication Subtype USGS Numbered Series
Title Nearshore water quality and coral health indicators along the west coast of the Island of Hawaiʻi, 2010–2014
Series title Open-File Report
Series number 2020-1128
DOI 10.3133/ofr20201128
Year Published 2021
Language English
Publisher U.S. Geological Survey
Publisher location Reston, VA
Contributing office(s) Pacific Coastal and Marine Science Center
Description Report: vii, 45 p.; Data Releases
Country United States
State Hawaii
Other Geospatial Island of Hawaii, Kaloko-Honokōhau National Historical Park, Puʻuhonua O Hōnaunau National Historical Park
Online Only (Y/N) Y
Google Analytic Metrics Metrics page
Additional publication details