摘要:

Expendable bathythermograph (XBT) and salinity observations were made along a north‐south section across the South Fiji Basin in March 1976, and XBT observations only were made in May 1976, January‐February 1977, and July 1978. The salinity section showed a tongue of low salinity (less than 34.75%c) surface water associated with the intertropical convergence zone of winds, near 20°S. The corresponding temperature section indicated the presence of weak eddies; a warm‐core eddy near 28°S, 176°E was encountered in February 1977. The main feature of the subsurface temperature structure was a thermal front between 25CS and 26°S at depths between 100 and 400 m: the temperature at 200 m was over 18°C north of the front and below 18°C to the south of it. This front, observed on all the temperature sections, was strongest from January to March. It is ascribed to the flow of a subtropical counter‐current similar to that encountered in the South Indian Ocean at about the same latitude.

ISSN:0028-8330    

DOI:10.1080/00288330.1981.9515925

出版商:Taylor & Francis Group    

年代:1981

数据来源: Taylor

摘要:

Water samples taken at 19 locations in the Mawheraiti River catchment at weekly intervals during 1979–80 were analysed for sodium, magnesium, potassium, calcium, phosphate, nitrate, and ammonium ion concentrations and for electrical conductivity. Seasonal discharge effects were apparent, and lithology and land management practice also influenced solute concentrations. Solute concentrations were generally very low; nitrate and soluble phosphate were rarely greater than 0.05 mg.L‐1and ammonium was rarely greater than 0.01 mg.L‐1. The 4 major cations (Na, Mg, K, and Ca) usually summed to less than 6 mg.L‐1much of which was supplied by precipitation. Forest management (clearfelling and slash‐burning) caused significant increases in solute concentrations, but concentrations declined rapidly during succeeding months and approached pretreatment levels after 2–3 years. The higher concentrations associated with forest management in small experimental catchments were rapidly diluted downstream; together with the low natural solute concentrations this suggests that harmful downstream effects of management practices are unlikely under low flow conditions.

ISSN:0028-8330    

DOI:10.1080/00288330.1981.9515926

出版商:Taylor & Francis Group    

年代:1981

数据来源: Taylor

摘要:

New Zealand stream ecosystems differ from many of their North American counterparts, on which general stream ecosystem models are based, in several ways. In New Zealand, large particle detritivores (shredders) are poorly represented, and the dominant invertebrates are browsers which feed on fine particulate organic matter and stone‐surface organic layers. In contrast with the river continuum concept of Vannote et al. (Canadian Journal of Fisheries and Aquatic Sciences 37:130–137, 1980), representation of functional feeding groups shows little change downstream and a temporal continuum of synchronous species replacements is not found. Many common benthic invertebrates are ecologically flexible species with poorly synchronised life histories. These differences appear to be associated with the non‐retentive, climatically unpredictable nature of the stream environment. The idea that stream communities are highly structured entities is questioned, as is the generality of the river continuum concept.

ISSN:0028-8330    

DOI:10.1080/00288330.1981.9515927

出版商:Taylor & Francis Group    

年代:1981

数据来源: Taylor

ISSN:0028-8330    

DOI:10.1080/00288330.1981.9515928

出版商:Taylor & Francis Group    

年代:1981

数据来源: Taylor