Joaquim I. Goes

Basin scale estimates of sea surface nitrate and new production from remotely sensed sea surface temperature and chlorophyll

The highly variable nature of T-N relationships in oceanic waters has restricted nitrate (N) measurements from remotely sensed sea surface temperature (SST) to small time and space domains. Here we show that if changes in T-N relationships resulting from phytoplankton (chlorophyll a) are taken into account, remote sensing can be exploited to provide high resolution maps of sea surface nitrate (SSN) that are valid over much larger scales than has been previously possible. We illustrate the potential of the method for monitoring basin scale, interannual variations in SSN in the north Pacific Ocean using co-registered imagery of SST and chl a and demonstrate the usefulness of such data for estimating basin scale annual new production.

A method for estimating sea surface nitrate concentrations from remotely sensed SST and chlorophyll a-a case study for the north Pacific Ocean using OCTS/ADEOS data

Proposes a method to estimate sea surface nitrate (N) from space using satellite measurements of sea surface temperature (SST) and chlorophyll a (chl a). The procedure relies on empirical relationships between shipboard measurements of N and its predictor variables, temperature (T) and chl a in surface and near surface waters. Although N appears to be controlled primarily by T, the addition of the biological variable chl a helps improve N prediction by reducing local and regional differences in the character of the temperature-nitrate (T-N) relationship. The authors have applied these empirical algorithms to SST and chl a data from the Ocean Color and Temperature Scanner (OCTS) on board the Advanced Earth Observation Satellite (ADEOS). The results clearly suggest that measurements of SST and chl a now possible by modern-day ocean satellites could be exploited usefully to extend the resolution of shipboard N measurements over large spatial and temporal scales. Systematic errors in estimates of N that could result from errors in satellite estimates of SST and chl a are examined through sensitivity analyses.

Particulate absorption properties from MODIS ocean color and four in-situ transects in the southeastern Bering Sea shelf during July, 2008

Measurements of particulate absorption, namely absorption by phytoplankton and non-algal particles (NAP) are important components in bio-optical models; only a few studies have been reported for the southeastern Bering Sea. This study analyzes variability in spectral particulate absorption (aP(λ)) including phytoplankton (aPHY(λ)) and NAP absorption (aNAP(λ)) from in-situ data in conjunction with ocean color satellite data (MODIS - Moderate Resolution Imaging Spectroradiometer) along four transects in the southeastern Bering Sea shelf during a cruise in July 2008. Results obtained indicate that surface aPHY(λ) at 443 nm is higher in middle shelf near the Pribilof Islands with aNAP(λ) decreasing from north to south across the shelf. Greater than 90% of variability in aP(λ) could be explained by aPHY(λ) indicating biogenic matter dominates changes in particulate absorption. Good correlations were found between aP(λ), aPHY(λ) at 443 nm and chlorophyll-a (R2 = 0.65 and 0.80, respectively). aPHY(λ) spectra were highly variable, with larger variability in blue than red part of the spectrum, indicating change in pigment composition or package effect. MODIS satellite derived aPHY(λ) using quasi-analytical algorithms (QAA) revealed patterns similar to in-situ absorption data for a major part of the study area. Inconsistencies seen between in-situ absorption and QAA retrieved satellite absorption could probably be attributed to temporal differences between in-situ data collection and satellite overpass.

Effect of UV-B radiation on the pathways of carbon biosynthesis in marine phytoplankton and its implications for the marine ecosystem

The threat of enhaneed solar ultraviolet-B radiation (UVBR) on rhe aquatie environment resulting from reeeding levels of stratospherie ozone is now being pereeived as real (MADRONICH 1994). Alrhough evidenee in support o f this pereeption is overwhelming, efforts at exrrapolating rhese findings, to allow aeeurate and unambiguous predietions of the likely eonsequenees of UVBR o n the marine eeosystem, have been eonfounded with uneertainty (l<ARENTZ er al. 1994). The siruation demands that we systematieally investigate the effeets of UVBR o n various aspeets of aquatie biologieal proeesses, espeeially in areas that are of immediate relevanee to the aquatie food ehain and biogeoehemieal eycles. During the last few years we have been investigating ehanges in rhe patterns of earbon metabolism aeeompanying UVBR-mediated deereases in phytoplankton produetion (GOES er al. 1994, 1995, 1996). The motivation for these studies stemmed from the reeognition that rhe rates of synthesis of individual bioehemieal compounds, rather than bulk earbon produerion within phytoplankton, may provide important clues for assessing the impaets of enhaneed UVBR on rhe aquatie eeosystem. This eonrribution summarizes the results of this study and diseusses their implieations for the marine food ehain and biogeoehemieal proeesses in the sea.