摘要:

Empirical models of zooplankton biomass (rotifer, crustacean, and rotifer + crustacean biomass) in relation to selected morphometric (depth, surface area, flushing rate, and watershed area) and chemical variables were developed for 20 Adirondack lakes. The chemical variables were selected to characterize acidity status (pH, acid neutralizing capacity, and aluminum concentrations), trophic status (total phosphorus, chlorophylla, phytoplankton biovolume, and Secchi depth), and humic influences (with dissolved organic carbon and color serving as surrogates of humic materials). Additional independent variables included major cations and anions (Ca++, Mg++, Na+, K+, Cl−, and SO4−), specific conductance, dissolved oxygen, and temperature. Zooplankton biomass averaged 85.2 mg/m3in the study lakes. Crustacean biomass accounted for an average of 65.9 mg/m3and rotifer biomass for 19.4 mg/m3. Rotifer biomass was a significant component of zooplankton biomass in many circumneutral as well as acidic Adirondack lakes. The relative importance of rotifer biomass–as a percentage of total zooplankton biomass–could be predicted from an empirical relationship including the log of chlorophylla, the log of monomeric aluminum, and true color as independent variables (R2= .70). Rotifer biomass was particularly important in acidic lakes largely as a result of crustacean zooplankton loss rather than enhanced rotifer biomass. The best fit rotifer biomass empirical model included the log of total phosphorus and maximum depth as predictor variables (R2= .69). Crustacean biomass was best described by a relationship that included the log of monomeric aluminum, the log of chlorophylla, and the log of dissolved organic carbon (R2= .70). The best fit empirical model for total zooplankton biomass was a combination of the above models including all the above independent variables except total phosphorus. This model, reflecting the interactions of acidity and productivity status and humic influences, accounted for 74 percent of the lake to lake variability in mean zooplankton biomass.

ISSN:1040-2381    

DOI:10.1080/07438148909354403

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

Laboratory algal bioassays using both cultures ofAnkistrodesmus bibraianusand natural phytoplankton, and large, in-lake, container assays with natural populations, were used to determine the factor most limiting phytoplankton production in Lake Chapala, México. Both types of laboratory culture assays showed that nitrogen was the principal limiting nutrient at each station across this very large lake in all seasons. The growth response of natural phytoplankton was similar to that ofA.bibraianus. However, management practices to regulate the lake's productivity based solely upon this laboratory information would be inappropriate because the natural population assays showed that the ultimate limiting factorinsituis illumination controlled by the high clay turbidity. Rarely, if ever, was phytoplankton production controlled by the laboratory-determined limiting nutrient, nitrogen, expressed in the lake. The importance of performing algal assays extensively through time and space also was demonstrated. The nitrogen-augmented increase over controls inA.bibraianusbiomass ranged from less than 50 percent at the end of the dry season to greater than 1,000 percent in the middle of the rainy season. The average annual percent response at different sampling stations ranged from 438 percent to 541 percent. Also, the sample to sample variation was different for different stations. The variation coefficient was only 35 percent for the mid-lake station, but greater than 84 percent for the station nearer the source of river inputs.

ISSN:1040-2381    

DOI:10.1080/07438148909354404

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor