Predicting plant nutrient concentrations from temperature and sigma- t in the upper kilometer of the world ocean

Abstract

A National Oceanographic Data Center data set comprised of 230,202 oceanographic stations representing all regions of the world ocean was analyzed statistically for temperature and sigma- t ( σ t ) relationships with nitrate, phosphate or silicic acid concentrations in the upper kilometer of the water column. Six cubic regressions were computed for each 10° square of latitude and longitude containing adequate data. World maps display the locations that allow the prediction of plant nutrient concentrations from temperature or σ t within the limits of selected subjective and objective criteria. Geographic coverage improves along the sequence: nitrate, phosphate and silicic acid, and is better for σ t than for temperature. A percentile analysis of the temperature or σ t at which less a selected amount of plant nutrient occurs provided a method to examine incipient nutrient limitation. Contour maps display the approximate temperatures above or σ t values below which nitrate, phosphate or silicic acid routinely approach unmeasurable concentrations in the world ocean as determined by classical plant nutrient analyses. The results summarize the global potential to predict plant nutrient concentrations from remotely sensed temperature or σ t and emphasize the latitudinally and longitudinally changing phytoplankton growth environment based on temperature, σ t and plant nutrients in present and past oceans.