Phosphorus Cycling in the Gulf of Maine: A Multi-Tracer Approach
Abstract
Knowledge of temporal and spatial nutrient turnover and export rates is of great importance for a variety of investigations, ranging from nutrient limitation to contamination uptake and removal. However, there are few methods which allow for the in situ elucidation of these processes. In this thesis research, in situ phosphorus turnover rates and upper ocean export were determined within the southwestern Gulf of Maine using the naturally occurring radionuclides phosphorus-32 (t1/2 = 14,3 d), phosphorus-33 (t1/2 = 25.3 d), Thorium-234 (t1/2 = 24.1) and beryllium-7 (t1/2 = 53.3 d). New techniques were developed for the extraction, purification and measurement of P-32 and P-33 in rainwater and in inorganic, organic and particulate pools in seawater. In order to Constrain the input ratio of P-33/P-32, rain samples were collected and measured continuously for P-32 and P-33, as well as Be-7 and Pb-210, from March 1996 to March 1998 at Woods Hole, MA, and from March 1997 to October 1997 at Portsmouth, NH. The average P-32/P-32 ratio was 0.88 +/- 0.14. P-32, P-33, Be-7 and Pb-210 were further used to determine aerosol residence times and as possible tracers of stratospheric/tropospheric exchange, during severe Storm events. Four cruises were conducted in Wilkinson Basin, in the Gulf of Maine, during the spring and summer of 1997. Th-234 was used to estimate advection and diffusion using ID steady state and multi-dimensional non-steady state models. Export ratios (export/primary production) were found to range between 0.11 and 0.37. Vertical eddy diffusivity found using Be-7 varied from 0.5 to 1.5 cm2/sec. Significant changes in phosphorus turnover rates within the reservoirs which contained P-32 and P-33 activity were found between the spring and summer months. In late summer, bacterial activity was substantial, significantly affecting the residence times of dissolved inorganic and organic phosphorus pools.
Document Details
- Document Type
- Technical Report
- Publication Date
- Sep 01, 1998
- Accession Number
- ADA363529
Entities
People
- Claudia R. Benitez-nelson
Organizations
- Massachusetts Institute of Technology