AOML's Ocean Chemistry and Ecosystems Division

Nutrient Biogeochemistry

All life on earth requires nutrients to survive. Nitrogen and phosphorus are essential macronutrients for the growth of aquatic plants and animals. Some phytoplankton (such as diatoms) also requires silicon for building their cell walls. Metals, such as iron and molybdenum, are needed in much smaller amounts and are considered micronutrients. Excess input of nutrients to the environment, often induced by human activity, can cause algae blooms resulting in eutrophication in the aquatic ecosystem.

The OCED's nutrient biogeochemistry program utilizes state-of-the-art equipment and techniques, many of which were developed in-house to study nutrient dynamics in coastal and open ocean environments. The field programs focus on the nutrient dynamics coupled with carbon and oxygen cycles in open oceans. In coastal environments, we study the role of nutrient availability in ecosystem functioning.

Current projects being conducted by the Nutrient Biogeochemistry program are:

1. In collaboration with the PMEL nutrient group, we conducted high-quality shipboard nutrient measurements for the GO-SHIP/CO2 Repeat Hydrography program. Nutrient data are essential in estimating anthropogenic carbon in the ocean and in studying global biogeochemical cycles. The two figures show recent measurements of phosphate, nitrate, nitrite and silicate along the 2013 A16N cruise track and display the remineralization signals increasing with the age of the deep water masses. Biological uptake results in low nutrients in surface waters. Recently ventilated Labrador Sea water and Upper North Atlantic Deep Water occupy much of the section and have relatively lower nutrient contents. The sub-surface (~ 1000 m) phosphate and nitrate maximum in the tropics is due to remineralization in Antarctic Intermediate Water. The highest nutrient bottom water just south of the Mid-Atlantic Ridge around the equator is old Antarctic Bottom water in the western basin of the South Atlantic. Concurrent measurements of DIC, nutrients, oxygen and CFC, as well as physical parameters in the repeat hydrography program, provide valuable information on ocean circulation and biogeochemical process in the region.

2. We have performed, in collaboration with the Florida Bay and FACE programs, high quality nutrient measurements for the the water quality monitoring program in south Florida coastal waters.

3. Utilizing sequential extraction technique and sorption isotherm experiments, the nutrient group studied the sediment-water exchange of phosphorus in the Florida Bay and the role of sediment resuspension in controlling this limiting nutrient. A solid understanding of phosphorus cycling between water and sediment is needed in order to predict the effect it will have on ecosystem function and the consequences on environmental change.

4. We have developed analytical methods for low-level nutrient measurements using liquid waveguide and other novel techniques. Such capability are needed because standard methods do not achieve the detection limits required for measurements in oligotrophic waters (e.g., typical coral reef habitat, open ocean surface waters) or the high spacial resolution underway measurements required for oceanic surface process study (e.g., tracer tracking, plum mapping).

Contact Information for OCED Biogeochemistry Researchers:

Selected Nutrient Biogeochemistry Publications:

Zhang, Jia-Zhong, Charles J. Fischer, and Peter B. Ortner, (2004). Potential availability of sedimentary phosphorus to sediment resuspension in Florida Bay, Global Biogeochemical Cycles, 18, GB4008, doi: 10.1029/2004GB002255.

Zhang, Jia-Zhong and Xiao-Lan Huang (2007). Relative importance of solid-phase phosphorus and iron in sorption behavior of sediments. Environmental Science and Technology, 41(8): 2789-2795, DOI: 10.1021/es061836q.

Huang, Xiao-Lan and Jia-Zhong Zhang (2009). Neutral persulfate digestion at sub-boiling temperature in an oven for total dissolved phosphorus determination in natural waters. Talanta, 78:1129-1135.

Zhang, J.-Z., C. Kelble, C. Fischer and L. Moore (2009). Hurricane Katrina induced nutrient runoff from an agricultural area to coastal waters in Biscayne Bay, Florida. Estuarine Coastal and Shelf Sciences, 84:209-218. doi:10.1016/j.ecss.2009.06.026.

Zhang, Jia-Zhong, Xiao-Lan Huang (2011). Effect of temperature and salinity on phosphate sorption on marine sediments, Environmental Science & Technology, 45: 6831-6837. DOI: 10.1021/es200867p.