Nutrient, chlorophyll and zooplankton seasonal variations on the southern coast of a subtropical saline lake (Mar Chiquita, Córdoba, Argentina)

A comprehensive, but simple-to-use software package for executing a range of standard numerical analysis and operations used in quantitative paleontology has been developed. The program, called PAST (PAleontological STatistics), runs on standard Windows computers and is available free of charge. PAST integrates spreadsheet-type data entry with univariate and multivariate statistics, curve fitting, timeseries analysis, data plotting, and simple phylogenetic analysis. Many of the functions are spe...

A numerical trophic state index for lakes has been developed that incorporates most lakes in a scale of 0 to 100. Each major division (10, 20, 30, etc.) represents a doubling in algal biomass. The index number can be calculated from any of several parameters, including Secchi disk transparency, chlorophyll, and total phosphorus.

A method by which the TN and TP in water samples can be determined simultaneously employing peroxodisulfate oxidation was developed. A solution of 0.074 mol 1−1K2S2O8–0.075 mol 1−1 NaOH was adopted for the oxidizer, which made it possible to carry out alkaline peroxodisulfate oxidation for TN and acid peroxodisulfate oxidation for TP in turn during a single autoclaving. The pH values changed from 12.57 to approx. 2.0 and the period of alkalinity was estimated at 1.42 min at 120°C. The products o...

Henry’s law constants ( k o ) and equilibrium concentrations ( C o *) of dissolved oxygen (DO) at 1 atm were measured in NaCl solutions of concentration ( S ) up to ∼260‰ and at temperatures ( T ) between 273 and 308K. An equation of the form urn:x-wiley:00243590:media:lno19913620235:lno19913620235-math-0001 was found to predict DO values to within the experimental uncertainty. An equation of the same form satisfactorily described the variation of ln k o over the same temperature and concentrati...

Historically, phosphorus has been considered to be the primary nutrient limiting phytoplankton growth in freshwater ecosystems. We tested this hypothesis in 19 Kansas reservoirs located within the Central Plains region, USA. Bioassay experiments were conducted to assess growth-rate limitation by nitrogen (N), phosphorus (P) and nitrogen and phosphorus (N and P). The addition of P alone rarely increased phytoplankton growth with only 8% of the total bioassay experiments indicating P-limitation. I...

Great Salt Lake (Utah, USA) is one of the world's largest hypersaline lakes, supporting many of the western U.S.'s migratory waterbirds. This unique ecosystem is threatened, but it and other large hypersaline lakes are not well understood. The ecosystem consists of two weakly linked food webs: one phytoplankton-based, the other organic particle/benthic algae-based. Seventeen years of data on the phytoplankton-based food web are presented: abundances of nutrients (N and P), phytoplankton (Chlorop...

During unusually wet years the salinity of the Great Salt Lake (Utah) decreased from above 100 g/L to 50 g/L. This allowed the predaceous insect Trichocorixa verticalis to invade the pelagic region of the lake and reach a mean summer density of 52/m3. Concurrent changes in the pelagic ecosystem were: a decrease in the dry biomass of the previously dominant filter-feeding brine shrimp Artemia franciscana from 720 to 2 mg/m3, the invasion of three other zooplankton taxa, a 10 × decrease in communi...

Physical, chemical and biological variables were measured in the Great Salt Lake during 1985–87, when salinity in the mixolimnion was near 50 g/L, much lower than the 250 g/L maxima recorded in 1963. Decreased salinity has been accompanied by a change in macrozooplankton from one species (Artemia franciscana), to an assemblage with one rotifer, two copepods, Artemia, and the corixid Trichocorixa verticalis. Predation by the corixid may now limit Artemia to low densities (<100∙m −3 ). The low ...