MGGD Research Areas


Tropical watershed and coastal zone biogeochemistry / pollution

Revovery of buoy thumbnail photo.Hawaii’s stunning scenery includes majestic volcanic mountains covered with tropical rainforests and contrasting white sandy beaches and coral reefs that rim each island. Beyond, one finds some of the clearest marine waters found on Earth. It is therefore not surprising that the health and protection of marine ecosystems are of vital interest the State of Hawaii. This is true both from a purely economic perspective and, probably much more importantly, from the cultural perspective of our native population.

Unfortunately, beaches and nearshore environments in Hawaii are very sensitive to environmental degradation. High rainfall and the consequent abundant storm runoff in the steep watersheds of the Hawaiian Islands lead to the delivery of pulses of material to coastal waters that can quickly affect nearshore water quality. The runoff carries freshwater and natural sediment but often also contains a variety of pollutants. Thus, material transfers at the land-ocean interface in Hawai‘i have potentially important repercussions on coastal ecosystems that may adversely impact public use and recreation. This is particularly true in semi-enclosed embayments, such as Kane‘ohe Bay, O‘ahu, where water has a relatively long residence time compared to more open coastal areas of the islands. Other coastal areas that are more exposed to ocean waves and currents are nonetheless potentially impacted by runoff owing to the high frequency of rainstorms over the islands.

Research carried out by various members of the Marine Geology and Geochemistry Division at the land-ocean inteface is multifaceted. Active areas of study by our faculty include investigations of how short term changes in water quality in Kane‘ohe Bay following rain events impact coastal productivity and CO2 exchange between the ocean and the atmosphere (DeCarlo, Mackenzie), nutrient cycling in shallow sedimented environments and traditional Hawaiian fishponds (Ruttenberg, Glazer), how physical processes (waves, currents and tides) impact benthic productivity and exchange between sediment (and reefs) and the overlying water column (Sansone, De Carlo, Glazer), how runoff contributes to the microbial diversity and ecology of coastal waters (Cowen, Glazer), as well as how urban and agricultural land use impact marine water quality De Carlo). This work is conducted through a combination of observational and experimental approaches and often includes continuous in-situ measurements and adaptive synoptic sampling carried out on a variety of temporal and spatial scales. MGGD faculty work closely with many other researchers with complementary expertise (e.g., Physical Oceanographer M. McManus and Ocean Engineer/fluid dynamics G. Pawlak).

[ ABOVE ] CRIMP -CO2 Buoy upon recovery, following a 10 months deployment in Kane‘ohe Bay. The instrument frame of the buoy and cable are heavily colonized by sea fans, sponges, barnacles, algae and other biota in spite of the presence of strong antifoulant coatings. The buoy is equipped with a variety of instruments that measure physical and chemical properties (conductivity, temperature and pressure, pH, CO2 and O2 concentrations, turbidity/particle size distributions, pH, Chlorophyll-a). Data from most of these instruments are telemetered via Iridium satellite to NOAA/PMEL every three hours.

Installing sampling wells thumbnail photo. Divers installing porewater sampling wells at the Kilo Nalu Nearshore Reef Observatory offshore of Honolulu, O‘ahu, as part of a study of sediment-seawater exchange processes in sandy marine sediments.

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