2008 Funded Access to the Sea Proposals

Exploring Microbial Phosphorus Cycling in the Red Sea
Benjamin Van Mooy

Phosphorus (P) is an essential nutrient for all marine organisms, and the role of this element in controlling the productivity and diversity of marine ecosystems is becoming increasingly well-recognized, particularly in the tropics and subtropics.  However, unlike the oceans at these latitudes, the phosphorus dynamics of the Red Sea have almost completely escaped characterization. We are seeking support to participate on an R/V Oceanus cruise to the Red Sea, which will provide us access to conduct what we expect will be the first comprehensive study of phosphorus in this tropical sea. This cruise represents a rare opportunity for true exploration, one that we might not expect to have again during our careers.  Furthermore, fluctuations in the amount and chemical makeup of phosphorus are known to have adverse effects on coral reef environments, one of the Red Sea’s most significant natural resources. Future coastal development and global environmental change are certain to result in changes in phosphorus, and thus our study will provide a valuable benchmark dataset against which to monitor environmental change and to direct the management of coral reef resources.

Field Evaluation of a New Method for Examining Microbial Rhodopsin
Samuel Laney, Robert Olson

WHOI support from a Cecil H. and Ida M. Green Technology Innovation Award, and from the Edwin W. Hiam Endowed Fund for Ocean Science and Technology, is funding the development of a seagoing instrument for detecting rhodopsin in seawater.  Rhodopsin is a pigment that certain microbes use to obtain metabolic energy from sunlight, and in the last few years genes for different rhodopsin variants have been found in many ocean regions. This has generated considerable speculation regarding a second, more primitive form of light-driven metabolism in the ocean, one not dependent on chlorophyll but on rhodopsin instead. The ecological importance of rhodopsin-based light harvesting in marine ecosystems remains largely speculative because almost all of what is known about marine microbial rhodopsin comes from laboratory or genomic studies, not from direct spectroscopic analyses of environmental samples. Little is known about rhodopsin’s actual ecological role or distribution in the ocean. The method and instrument currently being developed with WHOI support measures rhodopsin’s presence in seawater directly, allowing its functional behavior to be assessed in live organisms in natural assemblages at sea, with minimal experimental manipulation. 

Funding from WHOI’s Access to the Sea Endowment is being sought to test and evaluate this new instrumentation outside of the laboratory, on R/V Oceanus’ return transit from Saudi Arabia in Nov-Dec 2008. Field assessment of this instrumentation is necessary to provide a comprehensive assessment of this instrument’s capabilities beyond what can be determined with the few available laboratory strains of microbial rhodopsin. In addition to providing a rigorous demonstration of this new instrumentation’s potential for providing at-sea measurements of rhodopsin, this particular transit will also cross ocean biomes where no information on rhodopsin has yet been collected. This transit also passes through two ocean regions where much of the previous genomic effort on rhodopsin has been focused (the eastern Mediterranean and the North Atlantic around Bermuda), presenting a unique opportunity to prove or refute with direct observations several current genome-based hypotheses about rhodopsin’s role in these regions. Distributions of rhodopsin measured with this instrument during this transit, or even the lack of a detectable signal, would provide important insight into rhodopsin’s prevalence and the oceanographic methods needed to understand its ecological relevance better.

High Range CTD for Exploration of Red Sea Deep Brine Pools
Raymond Schmitt, Robert Petitt

The hot brine pools of the Red Sea may well be the hottest and saltiest natural waters to be found on Earth. As such they present a unique challenge for sampling with regular oceanographic instruments. The physical structure of these fluid pools is of particular interest, as they involve double-diffusive mixing in which thin high-gradient regions are formed that separate well mixed layers above and below. Greater thermal diffusion across the interfaces occurs because of the great difference in the molecular diffusivities of heat and salt (Schmitt, 1994). The buoyancy flux due to the heat diffusion drives convection that keeps the mixed layers stirred. We are interested in the detailed structure of these convectively-driven layered systems. High-resolution data on the interfacial gradients will allow estimates of heat and salt fluxes, and mapping of the extent and water properties of the layers will permit budgets and estimates of heat and salt supply to the deep brine pools. This proposal seeks support for development of a high-range CTD to enable this exploration which will be partially underwritten by KAUST.

Cooperative Investigations of Deep-Sea Brine Areas in the Red Sea
Timothy Shank, S. Adam Soule, Maurice Tivey

We seek modest funding to conduct preliminary analyses of biological, geological and geophysical data resulting from towed deep-sea digital camera (TowCam) surveys to be conducted in and across brine pool rifts in the Red Sea as part of the joint KAUST/WHOI collaborative cruises in Fall 2008.  TowCam data will be acquired during Leg 2 (A. Bower, Chief Scientist) and has largely been funded by KAUST as an add-on to the overall project, which includes three days of KAUST ship time funding for work in the brine pool areas.  Analysis of these data have important and broad implications for better understanding linkages between global hydrothermal vent communities and the specific nature of hydrothermal venting in brine pool settings within a nascent mid-ocean ridge forming in a young continental rift.

PALflux-New Tools to Study Particle Cycling off the Antarctic Peninsula
Kenneth Buesseler, Andrew McDonnell

Nowhere in the world perhaps is global change as evident as near the poles, where changing temperatures, sea ice, winds and circulation are having measurable impacts on ocean ecosystems and biogeochemistry. Logistically, to work in these remote regions requires specialized equipment and considerable effort. Perhaps then with such limited access, it is no wonder that despite over a decade of study off the western Antarctic Peninsula (WAP), and unmistakable evidence of dramatic climate change in this region, there is still no clear understanding of processes that lead to consumption and transport of particles from the productive surface waters to the WAP shelf sediments. Current estimates of the fate of biologically derived particulate organic matter (POM) suggest that only a small percent of net primary production is reaching the sea floor after the seasonal ice melt. Yet this is a mystery since the WAP ecosystem is more likely than others to be highly efficient at exporting POM based upon our current understanding of cold water polar ecosystems. So just how this ecosystem works and how it is changing remain key unknowns in our observations of the WAP.

This proposal seeks funds to address these questions by participating in the first process study cruise ever conducted as part of the Palmer Long Term Ecological Research (PAL) program.  Lead scientist for PAL, Hugh Ducklow, has generously offered us two remaining berths and logistical support, so we might be able to bring new technologies and tracers to study POM cycling at this remote site in Jan/Feb 2009. We propose to deploy new in situ respiration chambers recently designed and built at WHOI (J. Valdes, PO Dept.) to measure the rates of microbial degradation of sinking particulate matter. We will also utilize an underwater imaging system, the Video Plankton Recorder (VPR, developed at WHOI), and measurements of the particle-tracking tracer, thorium-234, to quantify and map particle export and decomposition across the WAP.  Funds are requested to support Ken Buesseler and JP student Andrew McDonnell to participate in this cruise and to help purchase a VPR for use on this cruise and in other similar and subsequent studies. We anticipate that particle export and remineralization rates at PAL will contrast to the Bermuda site we are currently studying, providing an important set of end members for quantifying possible variability in the ocean’s “biological pump”. We also plan to submit a more ambitious and long term funding request to NSF-OPP in June 2008, and hope to use the independent research opportunity described here to jump start the collection of data needed to document change, and to help greatly in the development of new in situ technologies that are a unique aspect of our POM studies and JP thesis efforts of McDonnell.

Meteor Cruise to Investigate Nitrogen Cycling at the Oxygen Minimum Zone Off Peru
Richard Camilli

Di-nitrogen, N₂, is the end-product of Anammox and denitrification. This is a fundamental removal process of fixed nitrogen in the water column and the seafloor sediment. Although N₂ is not a greenhouse gas, fixed nitrogen is a limiting nutrient and changes in the relative rate of denitirfication can affect marine productivity and the ocean’s ability to biotically sequester atmospheric CO₂. The effects of these processes are thought to be globally significant, and particularly intense in productive low oxygen waters. Current estimates of mass transfer rates of total nitrogen suggest source/sink imbalance of as much as 195 million tons per year. Novel pathways of nitrogen turnover have recently been discovered but it is still uncertain whether the present estimates of fixed nitrogen input need an upward revision or whether the oceanic N cycle is far from steady state.

To better understand these aspects of the nitrogen cycle, we propose to quantify N₂ fluxes across the sediment water interface along transects at 10°S and 12°S in the oxygen minimum zone (OMZ) at the Peruvian continental margin. The OMZ in this region strongly influences nitrogen cycling and pathways of nitrogen loss in the water column. Our program will use a WHOI TETHYS in-situ mass spectrometer deployed on an IFM-GEOMAR benthic lander system. During these deployments the TETHYS mass spectrometer will continuously record levels of N₂ and Ar as well as other biologically active dissolved gases (i.e., H₂ CH₄ O₂ H₂S CO₂) within a water reservoir enclosed by the benthic chamber. By integrating the TETHYS mass spectrometer into the lander, continuous in-situ measurement of dissolved gases will be possible.  This data set will enable highly resolved temporal observations (~2,500 measurements/day) of bottom water oxygenation states inside the benthic chamber and their effects on nitrogen fluxes, without the risk of atmospheric contamination bias. By this means thresholds driving nitrogen turnover and speciation can be identified. This information will yield better quantitative estimates of nitrogen cycling rates, and may provide useful information for modeling ocean productivity and marine CO₂ sequestration.