Ecological data has several special properties: the presence or absence of species on a semi-quantitative abundance scale; non-linear relationships between species and environmental factors; and high inter-correlations among species and among environmental variables. The analysis of such data is important to the interpretation of relationships within plant and animal communities and with their environments. In this corrected version of Data Analysis in Community and Landscape Ecology, without using complex mathematics, the contributors demonstrate the methods that have proven most useful, with examples, exercises and case-studies. Chapters explain in an elementary way powerful data analysis techniques such as logic regression, canonical correspondence analysis, and kriging.
1. Pore water chemistry in peaty sediment was monitored for a year at two representative locations of the eutrophic shallow Loosdrecht lakes. The Netherlands. Phosphorus fluxes over the sediment-water interface were calculated using measured concentration gradients in the pore water and compared to flu.xes measured under laboratory conditions. Results were analysed with Redundancy Analysis to detect pattems of variation in pore water chemistry and in measured and calculated fluxes, that could be ascribed to environmental variables.2. It was demonstrated that phosphorus fluxes measured in long-term laboratory incubations were not correlated to any of the pore water characteristics.3. Initial phosphorus fluxes measured in sediment columns, which varied between -7,7 and 1330 jimol m" day ', were correlated significantly to the calculated phosphorus flux over the sediment-water interface, 4. The high correlation between calculated fluxes of ammonia, phosphorus and methane and measured initial flux of phosphorus, conclusively pointed to mineralization of organic matter as the driving force for phosphorus release from the sediment.5. Redundancy Analysis demonstrated that the rates of mineralization and phosphorus release were only weakly related to temperature. They appeared to be especially stimulated by the autumnal decrease in temperature which was probably related to an extra input of organic matter.
The growth rates of larval and juvenile roach (Rutilus rutilus) were measured in the laboratory at different temperatures under conditions of excessive food supply. Using these data, the maximum growth rate of 0+ roach in relation to size and water temperature could be adequately described with an equation of the type: dW/dt = amax∙Wb∙(T−c) (W = weight, T = temperature, t = time). Using this equation the growth of larval and juvenile roach in Tjeukemeer was predicted for 12 successive years. The predicted growth rates were about 20% lower than the observed growth rates. Reasons for this bias are discussed. The results indicate that food is not limiting growth of roach in Tjeukemeer.
The paper summarizes the results of a ten-year (1981)(1982)(1983)(1984)(1985)(1986)(1987)(1988)(1989)(1990)(1991) zooplankton research on the Lake Loosdrecht, a highly eutrophic lake. The main cause of the lake's eutrophication and deteriorating water quality was supply up to mid 1984 of water from the River Vecht. This supply was replaced by dephosphorized water from the Amsterdam-Rhine Canal in 1984. The effects of this and other restoration measures on the lake's ecosystem were studied. Despite a reduction in the external P-load from ca. 1.0 g P me2 y-l to ca. 0.35 g rnp2 y-l now, the filamentous prokaryotes, including cyanobacteria and Prochlorothrix, continue to dominate the phytoplankton.Among the crustacean plankton Bosmina spp, Chydorus sp. and three species of cyclopoid copepods and their nauplii are quite common. Though there was no major change in the composition of abundant species, Daphnia cucullata, which is the only daphnid in these lakes, became virtually extinct since 1989. Among about 20 genera and 40 species of rotifers the important ones are: Anuraeopsis j?ssa, Keratella cochlearis, Filinia longiseta and PoZyarthra. The rotifers usually peak in mid-summer following the crustacean peak in spring. The mean annual densities of crustaceans decreased during 1988-1991. Whereas seston (< 150 pm) mean mass in the lake increased since 1983 by 20-60%, zooplankton (> 150 pm) mass decreased by 15-35x.The grazing by crustacean community, which was attributable mainly to Bosmina, had mean rates between 10 and 25% d-'. Between 42 and 47% of the food ingested was assimilated. In spring and early summer when both rotifers and crustaceans have their maximal densities the clearance rates of the rotifers were much higher. Based on C/P ratios, the zooplankton (> 150 pm) mass contained 2.5 times more phosphorus than seston (< 150 pm) mass so that the zooplankton comprised 12.5 y0 of the total-P in total particulate matter in the open water, compared with only 4.5% of the total particulate C. The mean excretion rates of P by zooplankton varied narrowly between 1.5 and 1.8 pg P l-' d -', which equalled between 14 and 28% d-' of the P needed for phytoplankton production. The lack of response to restoration measures cannot be ascribed to one single factor. Apparently, the external P-loading is still not low enough and internal P-loading, though low, may be still high enough to sustain high seston levels. Intensive predation by bream is perhaps more important than food quality (high concentrations of filamentous cyanobacteria) in depressing the development of large-bodied zooplankton grazers, e.g. Daphnia. This may also contribute to resistance of the lake's ecosystem to respond to rehabilitation measures. 70
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