Phosphorous cycling in the Gulf of Maine : a multi-tracer approach
Benitez-Nelson, Claudia R.
MetadataShow full item record
LocationGulf of Maine
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 that 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 (t_= 14.3 d), phosphorus-33 (t_ = 25.3 d), thorium-234 (t_ = 24.1) and beryllium-7 (t_ = 53.3 d). New techniques were developed for the extraction, purification and measurement of 32p and 33p in rainwater and in inorganic, organic and particulate pools in seawater. In order to constrain the input ratio of 33p/32p, rain samples were collected and measured continuously for 32p and 33p, as well as 7Be and 21OPb, from March 1996 to March 1998 at Woods Hole, MA, and from March 1997 to October 1997 at Portsmouth, NH. The average 33p;32p ratio was 0.88 ± 0.14. 32p, 33p, 7Be and 210Pb were further used to determine aerosol residence times and as possible tracers of stratospheric/tropospheric exchange during severe storm events. F our cruises were conducted in Wilkinson Basin, in the Gulf of Maine, during the spring and summer of 1997. 234Th was used to estimate advection and diffusion using 1D 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 7Be varied from 0.5 to 1.5 cm2 sec-I. Significant changes in phosphorus turnover rates within the reservoirs which contained 32p and 33p 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. Our results clearly show that 32p and 33p can provide much needed information regarding the biogeochemical cycling of P in marine systems and can be of use in the development of ecosystem models which seek to address mechanisms which affect primary production in the ocean.
Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution September 1998
Showing items related by title, author, creator and subject.
Nadakuditi, Rajesh Rao (Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 2007-02)The first part of the dissertation investigates the application of the theory of large random matrices to high-dimensional inference problems when the samples are drawn from a multivariate normal distribution. A longstanding ...
Alpert, Alice (Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 2016-09)Paleoclimate archives place the short instrumental record of climate variability in a longer temporal context and allow better understanding of the rate, nature and extent by which anthropogenic warming will i ...
Christeson, Gail L. (Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 1994-02)This thesis is concerned with understanding how oceanic crust is emplaced at mid-ocean ridges. The emphasis is upon fast-spreading ridges, and the use of seismic techniques to image the uppermost several hundred meters ...