| dc.contributor.author | Pena Aguilar, Maria Angelica. | en_US |
| dc.date.accessioned | 2014-10-21T12:36:04Z | |
| dc.date.available | 1994 | |
| dc.date.issued | 1994 | en_US |
| dc.identifier.other | AAINN05151 | en_US |
| dc.identifier.uri | http://hdl.handle.net/10222/55011 | |
| dc.description | The amount of carbon exported from the surface layers of the world's oceans is strongly influenced by processes at low latitudes; it has been estimated that the export flux of carbon, or "new" production, in the equatorial Pacific could account for a significant proportion (25 to 50%) of the global total. In this study, rates of new production were estimated from discrete measurements of nitrate uptake along a transect across the equatorial Pacific region at 135$\sp\circ$W, and from an analysis of nitrate and heat balance in the warm waters of the tropical Pacific. | en_US |
| dc.description | Results from direct measurements of N (nitrate and ammonia) uptake and primary productivity showed higher rates of total and new production near the equator which coincided with higher concentrations of chlorophyll and nitrate. Despite significant variations in nitrate concentration, variability of phytoplankton biomass and production was low along the transect. Although nitrate was abundant at the equator, regenerated N was the major source of inorganic N used by phytoplankton. | en_US |
| dc.description | The average depth-integrated new production rate in the warm waters of the tropical Pacific was computed through a horizontal and vertical nitrate balance. The net turbulent flux of nitrate into the region was computed using the climatological net surface heat flux and the nitrate-temperature relationship. The net advective nitrate transport into the region was estimated using the mean nitrate distribution obtained from historical data and previous results from a general circulation model of the tropical Pacific. The rate of new production resulting from vertical turbulent nitrate fluxes (24 mg C m$\sp{-2}$ d$\sp{-1}$) is similar in magnitude as that due to advective transport (20 mg C m$\sp{-2}$ d$\sp{-1}$). | en_US |
| dc.description | A simple biological model of the mixed layer was used to study the effects of fluctuations in the input of nitrate on phytoplankton biomass and new production. The steady-state solutions of the model were analyzed to determine the influence of parameter values on model output and simulations were carried out varying the frequency and magnitude of the nitrate input. When phytoplankton was growing at its maximum capacity or when biomass was limited by grazing, phytoplankton biomass did not respond to variations in the nitrate input, even when the nitrate input to the euphotic zone was high. From the frequency response, it was found that periods equal to or less than 4 days did not influence phytoplankton biomass and new production. On longer time scales, the magnitude of the biomass increase depended inversely on the frequency. | en_US |
| dc.description | This thesis supports the suggestion that nitrate utilization or new production in the equatorial Pacific is controlled by zooplankton grazing. Alternatively, it has been suggested that the availability of iron could be limiting phytoplankton growth and nutrient utilization in this region. Results from the model indicate that iron limitation of phytoplankton growth alone is not sufficient to explain the maintenance of low chlorophyll and high nitrate concentrations. | en_US |
| dc.description | Thesis (Ph.D.)--Dalhousie University (Canada), 1994. | en_US |
| dc.language | eng | en_US |
| dc.publisher | Dalhousie University | en_US |
| dc.publisher | | en_US |
| dc.subject | Biology, Oceanography. | en_US |
| dc.title | New production in the tropical Pacific region. | en_US |
| dc.type | text | en_US |
| dc.contributor.degree | Ph.D. | en_US |
