Determining the source and fate of organic carbon
in coastal waters

Coastal marine ecosystems generally receive nutrients from the influx of nutrient-rich bottom water through upwelling and/or terrestrial run-off. The Hauraki Gulf, off northeast New Zealand, is one of the most productive fisheries in that country. With no major rivers in the Hauraki Gulf, the main nutrient source there is believed to be marine-based rather than terrestrially derived. In collaboration with Dr. Maria Uhle (now at the National Academy of Science) and Dr. Scott Nodder (NIWA, Wellington New Zealand) we are using biomarker compounds as well as the δ13C signals of these compounds to trace marine versus terrestrial inputs and clarify the controls that local circulation has on inputs, transport, and cycling of organic carbon in the Hauraki Gulf. These compounds serve as tracers for the marine and terrestrial inputs and a proxy record of microbial re-working of sedimentary organics. Our results suggest that although terrestrial inputs may be more significant on the outer shelf than assumed from previous studies, microbial degradation is processing terrestrial organic material at a higher rate than marine components. We are presently applying for funding to conduct similar studies to examine the degradation and transport of terrestrial organic matter through the Hudson River estuary and on the shelf of the Mid-Atlantic Bight.

Hauraki Sites Map 
Map of study area in the Hauraki Gulf. We are studying sources of organic carbon in the Hauraki Gulf off northern New Zealand. The study is investigtaing the competing influences of marine flow into the Gulf from the north against terrestrial input to the south Rangitoto off bow.

View of Rangitoto Island

An extinct volcano which is a landmark in the Hauraki Gulf.

Multicorer

The multi-coring device used to collect short cores without disturbing surface sediments for this project