Latitudinal relationships among temperature and selected plant nutrients along the west coast of North and South America

The relationships among temperature and selected plant nutrients (nitrate, phosphate and silicate) were determined in marine waters for 10° latitudinal (longitudinal) bands along the west coast of North and South America. Data within each 10° band were obtained from the U.S. National Oceanographic Data Center, the Canadian Oceanographic Data Center or major oceanographic institutions...

Role of iron, light, and silicate in controlling algal biomass in subantarctic waters SE of New Zealand

Phytoplankton processes in subantarctic (SA) waters southeast of New Zealand were studied during austral autumn and spring 1997. Chlorophyll a (0.2–0.3 μg L−1) and primary production (350–650 mg C m−2 d−1) were dominated by cells 1 nmol kg−1, there was little evidence of Fe-stressed algal populations, and Fυ/Fm approached 0.60 at the STC. In addition to these trends, waters of SA origin were occasionally observed within the STC and north of the STC, and thus survey data were interpreted with caution. In vitro Fe enrichment incubations in SA waters resulted in a switch from flavodoxin expression to that of ferredoxin, indicating the alleviation of Fe stress. In another 6-day experiment, iron-mediated increases in chlorophyll a (in particular, increases in large diatoms) were of similar magnitude to those observed in a concurrent Si/Fe enrichment; ambient silicate levels were 4 μM. A concurrent in vitro Fe enrichment, at irradiance levels comparable to the calculated mean levels experienced by cells in situ, resulted in relatively small increases (approximately twofold) in chlorophyll a. Thus, in spring, irradiance and Fe may both control diatom growth. In contrast, during summer, as mean irradiance increases and silicate levels decrease, Fe limitation, Fe/Si colimitation, or silicate limitation may determine diatom growth

Nutrient utilisation and particulate organic matter changes during summer in the upper mixed layer (Ross Sea, Antarctica).

The relationships among vertical stability, estimated nutrient utilisation and particulate organic matter in the Ross Sea are analysed from data collected during two cruises in the summers of 1987 - 88 and 1989 - 90. In the upper mixed layer (UML), identified through the vertical stability E(Z(UML)), nutrient consumption is calculated as the difference between the « diluted » nutrient value and the mean calculated from the integrated value in the UML. The nutrient utilisation ratio and E(Z(UML)) are linearly related for E(Z(UML)) 25, the distribution pattern is more scattered and independent of E(Z(UML)). For E(Z(UML)) > 25, utilisation values were > 4, 0.4 and 10 mmol m-3 for nitrate, phosphate and silicate, respectively. Significant relationships between nutrient depletion and both particulate organic carbon (POC) and particulate protein / particulate carbohydrate ratios (PPRT/PCHO) are found. The analysis of particulate matter distribution vs nutrient utilisation shows that the stations could be divided into two groups having different characteristics. The first group includes coastal stations, where high nutrient utilisation, POC and PPRT / PCHO are typical of areas with high production. In the second group (pelagic stations), nutrient utilisation, POC and PPRT / PCHO are lower. The vertical stability can be used to discriminate among the factors that influence primary production