Here are some of the projects we're working on...
Trace metal analyzers
Iron cycling in the northern Red Sea
Application of 230Th to paleoceanography of ocean margins
Iron in coastal upwelling systems
Trace metal analyzers
There is a growing need to quantify the concentration and variability of toxic trace metals in the coastal ocean. In situ, autonomous instrumentation offers the advantage over discrete sampling of low cost, fewer chances for sample contamination, and greater temporal resolution of metal concentrations. As part of an NSF-funded project, we are designing and field-testing autonomous sensors for three important marine pollutants- copper, zinc and cadmium. Objectives for the sensors include the ability to accurately measure concentrations in the range of 0.5-250 nM with a precision of at least 6%.
These analyzers (the appropriate term, rather than sensor) are based on the well-tested DigiSCAN technology developed in the Chemical Sensors lab at the Monterey Bay Aquarium Research Institute (MBARI) and currently marketed by YSI. This is a versatile, compact sensor system for in situ wet chemistry that uses micro solenoid pumps for sample uptake and reagent dispensing.
Ultimately, the improved understanding of toxic metal concentrations in coastal waters afforded by these instruments will (1) enable us to quantify the extent of anthropogenic impacts, (2) help identify sources of pollution, (3) provide a warning system for coastal users, and (4) increase our understanding of the biogeochemical fate of metal pollutants in the marine environment.
You can learn more about this project by visiting Chris Holm's web page
This work is funded by the National Science Foundation
Iron cycling in the northern Red Sea
The Gulf of Aqaba (Eilat) is a unique oceanic ecosystem, in that it is definitely coastal, being surrounded on all sides by desert, but yet it is also an oligotrophic sea, with clear blue water most of the time. I am collaborating on a poject lead by Adina Paytan at Stanford, to look broadly at biogeochemical cycling within the Gulf. You can read more about the project at Adina's very nice website. My interest is primarily in the iron cycle, and in combining measurements of iron in seawater with measurements of iron input through dust.
This work is funded by NASA
Application of 230-Th to paleoceanography of ocean margins
Ocean margins are an important component of the global carbon cycle. Reconstructing past variations in the productivity of ocean margins, and their link to climate change, is therefore a high priority. However, paleoproductivity proxies typically perform poorly at ocean margins, due to poor preservation, large terrigenous inputs, and sediment redistribution processes, among others. The use of the naturally-occuring, long lived radionuclide, 230Th, as a constant flux proxy, has proven very useful in reconstructing patterns of particle flux and productivity in the open ocean. Its more limited use in the coastal ocean derives in part from the difficulty of separating scavenged Th and from detrital and authigenic sources, both of which are abundant in ocean margins. Currently, these components are assessed indirectly and uncertainties can be significant. We are trying to improve the application of the 230Th proxy in ocean margins by developing a novel flow through leaching technique designed to remove scavenged and authigenic Th, and authigenic U.
Ultimately we hope to apply these methods to some fascinating records recovered from the Chilean margin as part of ODP Leg 202. In collaboration with Jim McManus and Alan Mix, we're going to reconstruct the history of intermedaite waters in the South Pacific, and try to understand whether changes in oxygenation were driven by circulation or by productivity, or both.
This work is funded by the Petroleum Research Fund and by NSF
