Hawaii’s Main Island Coral Reefs’ resilience to bleaching due to low DIN levels in local waters
Coral reefs are biologically important to both humans and marine organisms due to their biodiversity. Over 15% of the world’s population lives within 100 km of coral reef ecosystems, deriving critical economic benefits through tourism and fishing (Hoegh-Guldberg 1999). Unfortunately the corals are under threat from rising temperatures and more frequent bleaching events. In September 2010 scientists predicted a worldwide bleaching event and monitored sites including Hawaii. Through constant monitoring, the reefs in Hawaii had minimized bleaching in comparison to other reefs such as the Great Barrier Reef (GBR). Studies show that corals have an increased chance of recovery after a bleaching episode if the surrounding waters are cleaner and contain fewer nutrients which could explain the difference between Hawaii and GBR corals.
In this study, analysis of dissolved inorganic nitrogen (DIN) will be used to compare the water quality at a diverse range of locations around the main Hawaiian Islands. I hypothesize that the corals in Hawaii are more resilient to coral bleaching because of lower DIN levels in the surrounding waters. To test this, DIN will be compared across different environments to determine if lower levels correlate with lower coral mortality rates. Saltwater samples will be taken from bays where coral reefs reside, both in popular tourist locations and in locations that experience less human impact. Samples will also be taken from the deep ocean far from the main islands to measure the background levels of DIN. On the island of Oahu, one freshwater sample will be taken from two rivers on either side of the island to quantify the contribution of DIN from human activity. In addition to water samples, photographic images will also be gathered and analyzed using imager analysis software. Images will be used to collect data quantifying number and relative frequency of bleached corals, coral coverage, and other visual indicators of health such as color. Results of this study will contribute towards estimating the overall DIN level of water surrounding the main Hawaiian Islands.