Current and Recent Projects and Collaborations

Cesium isotopes in the Pacific Ocean following the Fukushia Dai-ichi NPP accident

We have been studying the dispersion patterns of cesium isotopes released from Fukushima in the North Pacific Ocean. We have created time series cesium records at the Hawaiian Islands and spatial distribution maps in the west and central Pacific. Our results can be found here.

Within this project we developed two highly efficient methods for cesium separation from seawater. Please see work done by postdoc Jan Kamenik.

Submarine Groundwater Discharge

Submarine groundwater discharge is a flow of fresh groundwater and recirculated seawater from a coastal aquifer into the ocean and is recognized as a pathway of dissolved components from land to the coastal zone. This water often carries pollutants from anthropogenic sources, for example nutrients from sewer systems or agricultural activities on land. The distribution of these sources along the coastline is not uniform, and the same is true about the magnitude of groundwater discharge. Consequently we are confronted with variable non-point source pollution at the land-ocean interface.

Submarine groundwater discharge and associated nutrient fluxes and their coastal residence time in Honokohau Harbor and Kiholo Bay.

Our research focuses on the assessment of groundwater discharge into Honokohau Harbor, Kiholo Bay and additional sites in Kona. We use geochemical tracers to derive groundwater fluxes into the coastal zone, investigate its composition (salinity, nutrients, trace metals), impact on the coastal zone (chlorophyll and primary productivity), and coastal residence time of groundwater derived components such as nutrients. We are looking at short- and long-term variability in fluxes and composition. We performed several in situ short-term time-series measurements of groundwater discharge rates, calculated groundwater-derived nutrient fluxes, and coastal residence time of groundwater derived nutrients. We established a biannual sampling scheme in which we focus on late summer when precipitation rates are generally lower and biological production higher, and a spring sampling during/after the wet period when we expect high groundwater discharge rates and different biological response to groundwater-derived nutrient delivery. Among others we have interesting results showing changes in SGD after the March 2011 tsunami and findings on iron chemistry at the land-ocean interface. Graduate student Christine Waters made this great educational VIDEO explaining her research. Within this project we also constructed a new autonomous continuous radon monitor called SGD Sniffer - the newest technology for long-term SGD monitoring. See details here.

Sustainable ecosystem management: analysis of water resources and quality in a contemporary ahupua‘a.

Coastal communities in the Hawaiian Islands have a common set of problems related to global climate change and increased population growth including impacts on water resources, water quality and down-stream coastal ecological health. In this project we have been collaborating with a community organization Kako‘o ‘Oiwi, committed to the restoration of lo‘i kalo in He`eia to develop a framework for sustainable management that includes current scientific exploration. We have been working on constructing hydrological models based on measured and geochemical tracer-derived water fluxes and information collected from the community. We are assessing water resources and projected availability in the watershed with respect to current land-use and proposed restoration efforts within future climate projections. We combine hydrology, ecosystem function and indigenous politics in an integrated research and outreach plan. This way our project provides strong links between interdisciplinary researchers and offers a new approach to coastal management that incorporates community. The final product will be a culturally relevant model that incorporates both scientific and traditional ecological knowledge. The project is funded by the UH Sea Grant.

Assessment of Groundwater Derived Nutrient Inputs on Oahu and Maui, HI.

In several interdisciplinary projects we have been looking at SGD and corresponding nutrient fluxes at various locations around the islands. We combine thermal infrared imagery, natural radioactive tracers, nitrogen isotopes, hydrogen and oxygen stable isotopes, hydrological models and many other tools to assess land-ocean fluxes. Among others some of the most anthropogenically affected sites we studied are: Kihei, Lahaina, Pearl Harbor, Maunalua Bay.

Tracing shelf-derived component transport offshore

Natural Iron Fertiliztaion in the Southern Ocean: Investigating Horizontal Iron Transport and Vertical Carbon Flux Using Radium Isotopes and ²³⁴Th.

There are regions of the high nutrient-low chlorophyll (HNLC) Southern Ocean that appear to be naturally fertilized by iron sources other than atmospheric deposition. One such area is the Southern Scotia Sea, downstream of the Antarctic Peninsula and the Shackleton Fracture Zone (SFZ). Here, we used radium isotopes as tracers of water transport to investigate the possibility that shelf-derived Fe is fueling phytoplankton blooms. We used ²²⁴Ra to calculate the rate of shelf derived iron transport into the HNLC offshore waters where we calculated the corresponding vertical carbon flux using ²³⁴Th.

Sources of Iron to the Eastern Tropical Atlantic: Does the Continental Margin Supplement Saharan Dust?

On a cross-shelf transect near Mauritania we examined lateral source of Fe from the continental margin. We combined measurements of specific tracers to uniquely determine the importance of lateral transport vs. dust inputs and subsurface remineralization as Fe sources to the surface ocean.

Development of New Radiochemical Methods

Determination of ²²⁷Ac in Young Basaltic Samples.

²²⁷Ac can be used as a radiometric dating tool and tracer of melt transport rates and magma storage times. For this application I developed an extraction chromatographic method to separate ²²⁷Ac from the rock matrix. The actinium values will be used by Ken Sims (WHOI G&G) in combination with ²³¹Pa as a chronometer for dating of young mid-ocean ridge basalts in the time range of 10-100 years.

High-Sensitivity Method for ²²⁸Ra Determination in Water Samples.

Open ocean ²²⁸Ra values are very low and even pre-concentration of radium on Mn-fibers from 500 Liter samples does not provide enough activity for gamma-spectrometric determination. We are working on developing an extraction chromatographic method to separate radium from the sample matrix and its consequent measurement directly by beta-counting or via alpha-counting its grand-daughter ²²⁸Th.