Nutrient Biogeochemistry Laboratory
Performing critical nutrient analysis to monitor water quality and changes in ocean chemistry across coastal and open ocean ecosystems
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What We Do
The AOML Ecosystem Assessment group leads the Nutrient Biogeochemistry lab with 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 and in coastal environments to study the role of nutrient availability in fueling ecosystem functioning. Many of our projects focus on land-based sources of pollution to understand the impact of humans on the marine environment.
We conduct liquid gas segmented flow colorimetric analytical methods for low-level nutrient measurements. Such capabilities 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 spatial resolution underway measurements required for oceanic surface process study (e.g., tracer tracking, plum mapping).
Who We Are
Key Impacts
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 require 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 contribute to or exacerbate algae blooms resulting in eutrophication in the aquatic ecosystem and in extreme scenarios, lead to hypoxic conditions and dead zones.
These elements support bacteria and phytoplankton, which form the base of the ocean food web. Bacteria take inorganic forms of nutrients and transform them into organic compounds that can be used by other marine organisms. Phytoplankton rely on these nutrients to support photosynthesis, the process where phytoplankton take up CO2 and produce half of the world’s oxygen. Phytoplankton and bacteria are also consumed by larger organisms, which in turn support all ocean life. Therefore, analyzing how nutrient levels fluctuate across coastlines, bays and pelagic ecosystems is how we gain valuable insights into the health and status of key environments and natural resources.
Nutrient Autoanalyzer
The Nutrient Autoanalyzer is used to analyze dissolved inorganic nutrients within seawater samples. Specifically, we can analyze silica, phosphate, ammonia, nitrite and nitrate with high accuracy and precision. This system enables us to identify nutrient levels in coastal and open oceans with seagoing cruises as well as local waterways and bays with small boat operations.
Analyzing Water Quality and Nutrient Concentrations Across South Florida
We’re leveraging the Nutrients lab to perform critical water quality analysis and monitoring across South Florida. Explore the Ongoing projects here:
Biscayne Bay
The Biscayne Bay field sampling trips are conducted monthly during the third week of each month (weather dependent). These are done in conjunction with sampling trips performed by the Department of Environmental Resources Management (DERM) and Florida Department of Environmental Protection (FDEP) two weeks prior in order to have bimonthly resolution of the water quality tracking land-based sources of pollution in Biscayne Bay. This dataset is used to inform and validate hydrodynamic water quality models in Biscayne Bay.
South Florida Ecosystem Restoration (SFER)
The South Florida Ecosystem Restoration (SFER) cruises are conducted bimonthly aboard a coastal class research vessel for the collection of nutrient and chlorophyll samples, in addition to other parameters collected by partner organizations, from inshore and offshore sites along the southern coast of Florida. The project aims to track freshwater inputs into Florida Bay, the Florida Keys and the West Florida Shelf from Lake Okeechobee, as well as areas of concern for Red Tide along the west coast.
Halozone Project
The EPA Halozone project is a sampling addition to the South Florida Ecosystem Restoration cruises to study the water quality dynamics, connections, and impacts of the very near-shore “halo zone”, defined as the region within approximately 500 meters of the shoreline, in the Florida Keys. The project involves collection of microbial, nutrient, and chlorophyll-a samples along four transects off a small boat.
Analyzing Nutrient Levels Across Open Ocean Environments
27N Role of Overturning Circulation in Carbon Accumulation (ROCCA)
The Western Boundary Time Series hydrographic surveys are conducted at 27N in the Florida Straits aboard the R/V Walton Smith to study how the Florida Current is changing over time. The Role of Overturning Circulation in Carbon Accumulation (ROCCA) project was added in 2024 to assess anthropogenic carbon fluxes across the 27N section and includes collecting dissolved inorganic carbon (DIC), total alkalinity (TA), and nutrient samples.
Global Ocean Ship-based Hydrographic Investigations Program (GO-SHIP)
In collaboration with NOAA’s Pacific Marine Environmental Laboratory’s (PMEL) nutrient group, we conduct high quality shipboard nutrient measurements supporting the Global Ocean Ship-based Hydrographic Investigations Program (GO-SHIP)Go-Ship/Repeat Hydrography program. Nutrient data are essential in estimating anthropogenic carbon in the ocean and in studying global biogeochemical cycles. Biological uptake results in low nutrients in surface waters.
Concurrent measurements of dissolved inorganic carbon (DIC), nutrients, oxygen and chlorofluorocarbons (CFC) as well as physical parameters in the repeat hydrography program provide valuable information on ocean circulation and biogeochemical processes in the Atlantic Ocean.
Examining the Cycling of Key Nutrients in the Atlantic Ocean
The figure here shows measurements of phosphate, nitrate and silicate along the A16 GO-SHIP cruise track from the surface to the seabed (max depth of 6,000 meters) and display of the remineralization signals increasing with age of deep water masses. Biological uptake results in low nutrients in surface waters.
Ventilated Labrador Sea water and Upper North Atlantic Deep Water have relatively lower nutrient content because of younger water masses (~ 100 years). Antarctic Intermediate Water is evident as a high nutrient tongue extending to 25 degrees N at approximately 1000 m depth. The old Antarctic Bottom water in the South Atlantic has the highest nutrient content and reaches the Mid-Atlantic Ridge around the equator.
Featured Publications
Examining the Cycling of Key Nutrients in the Atlantic Ocean
Palacio-Castro, A., et al. (2025). Elevated temperature decreases stony coral tissue loss disease transmission, with little effect of nutrients. Nature 15:22261. https://doi.org/10.1038/s41598-025-06322-0