Nearshore water properties and estuary conditions along the coral reef coastline of west Hawaii Island (2010-2014)

Spatial and continuous time-series measurements of water properties, including temperature, salinity, pH, and dissolved oxygen, from a range of depths and distances from shore, were collected along the west coast of the Island of Hawaii. These data and associated analyses help characterize the variability of coral reef habitats, and in particular, the influence of low temperature and low salinity groundwater entering the nearshore on coral health. Colder, fresher groundwater helps maintain estuarine conditions across extensive areas of nearshore reefs by depressing seawater temperatures and salinities, which may affect coral health and vulnerability to bleaching. These data also establish important baseline information with which to track and identify changes owing to climate and land use change, including changes in terrestrial runoff and contaminants that can affect the quality of habitat for corals, fish, and other wildlife of concern. Along the arid west coast of Hawaii Island, runoff consists primarily of groundwater as opposed to surface runoff. This study focused on examining the extent that groundwater inputs to the coast influence nearshore water properties, coral health, and help maintain cold-water refugia where corals may find resilience to the growing threat of bleaching associated with rising sea surface temperatures.