Grantee Research Project Results

Phosphorus Cycling in the Gulf of Maine: A Multitracer Approach

EPA Grant Number: U914959
Title: Phosphorus Cycling in the Gulf of Maine: A Multitracer Approach
Investigators: Benitez-Nelson, Claudia R.
Institution: Massachusetts Institute of Technology
EPA Project Officer: Hahn, Intaek
Project Period: January 1, 1996 through September 10, 1998
Project Amount: $102,000
RFA: STAR Graduate Fellowships (1996) RFA Text | Recipients Lists
Research Category: Fellowship - Oceanography , Fellowship - Aquatic Ecology and Ecosystems , Academic Fellowships

Objective:

The objective of this research project is to utilize several naturally occurring, short-lived radionuclides (³²P, ³³P, ²³⁴Th) within the Gulf of Maine to quantify: (1) uptake and regeneration rates of nutrients in dissolved, suspended, and large particulate phases; (2) zooplankton grazing rates; and (3) export of carbon, nitrogen, and phosphorus from the euphotic zone.

Approach:

If the atmospheric input of cosmogenic ³²P, ³³P, and ⁷Be is known from direct measurement, the ratio of ³²P and ³³P to ⁷Be can be directly related to: (1) the known decay rates of these tracers; (2) the particle reactivity of ⁷Be; (3) physical mixing and advection; and (4) the uptake ratio of phosphorus into particulate pools (i.e., the biological cycle of nutrient uptake and remineralization). Essentially, ⁷Be is used as both a tracer of upper-ocean mixing and as a constraint on the input flux of the ³²P and ³³P isotopes. Additionally, if ²³⁴Th is measured, estimates of particle export can be obtained for ⁷Be, organic carbon, and the major nutrients. Seasonal sampling in Wilkinson Basin in the Gulf of Maine will enable accurate temporal resolution of nutrient turnover rates and export.

Supplemental Keywords:

fellowship, phosphorus, carbon, nitrogen, phosphorus cycling, Gulf of Maine, nutrient uptake, remineralization, nutrients., RFA, Scientific Discipline, Ecosystem Protection/Environmental Exposure & Risk, Aquatic Ecosystem, Aquatic Ecosystems & Estuarine Research, Ecological Indicators, Ecological Risk Assessment, Ecosystem Protection, Ecology, Ecosystem/Assessment/Indicators, Oceanography, Ecological Effects - Environmental Exposure & Risk, Ecology and Ecosystems, nutrient loading, radionuclides, Gulf of Maine, phosphorus, eutrophication, nitrogen, zooplankton

Progress and Final Reports:

The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.