2015 Participants

Uranium-Thorium Age Model of Yucatan Carbonate Sediments
Collaborator: Dr. Adi Torfstein

Climate change is expected to alter where and how often rain falls across regions of the world with some locations receiving more rain and flooding hazards and others receiving less rain and drought.  Precipitation forms an important piece of the water resource puzzle, and understanding how it may change better prepares us to manage resources wisely.  In the Caribbean tropics, the Yucatan Peninsula draws its freshwater from groundwater recharged by rainfall.  This project aims to understand how rainfall in Yucatan Peninsula varied over the last 5,000 years of the late Holocene.  The frequency of droughts may increase with a warming climate, so understanding the natural variability and trends in the recent past help climate modelers predict how the hydrologic cycle may change in this region over the coming century.  Pinning these variations to specific time periods requires a good age history for the sediments along the Yucatan coast.  This may be accomplished with a technique known as uranium-thorium dating; these elements radioactively decay and produce a "clock" for when they were buried.  By looking at the age of sediments and how their chemistry changes, we can determine groundwater input as a proxy for rainfall, how it varies, and thus understand how water resources might be impacted in the near future.

Impacts of Dry Atmospheric Deposition on trace metal and Pb isotopic composition in Seawater, Particulate Matter and Sediment in Gulf of Aqaba, Red Sea
Collaborator: Dr. Adi Torfstein

Dry atmospheric deposition (DAD) is an important source of pollution to water bodies. The Gulf of Aqaba (GoA) lacks river input and precipitation during the summer period thus DAD may contribute major pollution to the ocean. While papers discussing how DAD influences seawater chemistry in the GoA are available only few include discussion of particulate matter in the water column. Specifically, we have a limited understanding of how DAD alters water and particulate matter chemistry on relatively short time scales. In this study I want to assess the relationships between DAD fluxes, DAD chemical characteristics, and its impact on water and particulate matter chemistry by collecting and analyzing chemical properties of aerosol, water, particulate matter and sediment in the GoA. We will collect total suspended particulate (TSP) samples by high volume TSP sampler daily. Profiles of seawater samples will be collected on research vessels, sinking particles (SP) will be obtained from sediment traps, suspended particulate matter with high volume pumps and surface sediments will also be obtained. Trace metal (Al, Mn, Fe, Co, Ni, Cu, Zn Cd and Pb) and Pb isotopic composition in DAD, seawater, SP sediments will be analyzed to determine impacts from DAD. An atmospheric deposition model base on meteorology and particle sizes will be applied to estimate flux of trace metals and particularly Pb input into the gulf, and a mass balance model used to obtain a mechanistic understanding of Pb cycling in the GoA. Obtaining these data can improve our understanding about atmospheric pollutants input and cycling in the Gulf of Aqaba.

Gene Expression Changes of Red Sea Coral in a Combined High Temperature Low pH Laboratory Experiment
Collaborator: Dr. Maoz Fine 

During the IRES program, I am going to research the combined effects of global warming and ocean acidification on Stylophora corals. The release of carbon dioxide to the atmosphere through the burning of fossil fuels and deforestation ultimately result in an increase in seawater temperature and ocean acidity. These processes may result in coral bleaching and reduced calcification. During two months, I am going to carry out a laboratory experiment with Stylophora coral nubbins which will be grown in aquaria at different pH and temperatures to simulate future ocean conditions. I am going to collect tissue samples to look for differences in gene expression and symbiotic algae health during the experiment. Negative impacts on corals may have significant consequences to the whole ecosystem: corals serve as food and shelter for other organisms and they take part in the formation and preservation of coastal relief and sand beaches. Therefore, a decline in the number, size or health of these calcifiers may have cascade effects throughout the food web. Moreover the biodiversity in reef systems is important since coral reef ecosystems provide many nature’s services to coastal communities such as erosion protection from storms and economic activities like fisheries and tourism. The results of this study will help to better understand how corals may cope with climate change, and may provide useful information for the design of management and conservation plans.
Quantifying Residence Times in the Coastal Aquifer via Lab and Field Methods

Concentrations of nitrate, silica, carbon dioxide, all of which are important to ocean chemistry, are subject to chemical transformations within the coastal groundwater aquifer in addition to metals, and other solutes.  The degree to which many chemical transformations can occur within the coastal aquifer is limited by the residence time of seawater within the coastal aquifer.  Seawater enters the coastal aquifer through a variety of mechanisms; the most common of which are wave and tidal action.  Residence time (how long water remains in a certain reservoir) of seawater in the coastal aquifer is a dominant factor controlling the biogeochemistry of the coastal aquifer. Shorter residence times of seawater in the coastal aquifer translates to less time for seawater to react and mix with groundwater and aquifer substrate, while longer residence times translate to more time for mixing and reactions to occur.  Yet, little is known about how short or long the residence times of seawater in the coastal aquifer typically are.  I will use short-lived radium isotopes (Ra-224 and Ra-223) to quantify residence times in a coastal aquifer in the Gulf of Eilat, using novel lab experiments combined with field observations. 

Joseph Murray
Constraining the Nitrogen Budget of the Gulf of Aqaba: A Nitrogen Isotope Approach
Collaborator: Prof. Ilana Berman-Frank 
 
The Gulf of Aqaba is a long, semi-enclosed ocean basin located at the northeastern end of the Red Sea.  The local climate is extremely arid, with little to no rainfall and no riverine input, with very high rates of surface water evaporation. This situation causes the Gulf to exhibit a reverse estuarine circulation pattern, where surface waters from the Red Sea pass through the Straits of Tiran, bringing north large volumes of low nutrient surface seawater into the Gulf.  To balance this inflow, deep, relatively nutrient rich waters flow south back through the Straits out into the Red Sea.  By simple mass balance, this circulation pattern results in a net loss of important nutrients, including inorganic nitrogen, from the Gulf, and yet the basin appears to be roughly in steady state with respect to its nitrogen balance.  Therefore there must be at least one, if not several, significant external sources of new nitrogen to the Gulf in order to support primary productivity in the Gulf.  Recent work by a number of different scientific research groups has attempted to quantify potential inputs of new nitrogen to the Gulf of Aqaba.  These sources include dry aerosol deposition, biological nitrogen fixation, remineralization of deep sea sediments, submarine groundwater discharge, and anthropogenic activity.  However, a full accounting of these estimates still shows an imbalance in the overall nitrogen budget for the Gulf.  Here, we propose to use a combination of past approaches, along with several new nitrogen isotopic methods, in order to attempt a full understanding of the sources, sinks and processes important for the marine nitrogen cycle of the Gulf of Aqaba.

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