Wc. Wolfinbarger, Influences of biotic and abiotic factors on seasonal succession of zooplankton in Hugo Reservoir, Oklahoma, USA, HYDROBIOL, 400, 1999, pp. 13-31
I measured water quality variables, primary productivity, biomass of phytop
lankton palatable to zooplankton and zooplankton abundance in mesotrophic H
ugo Reservoir, Oklahoma (U.S.A.) at weekly to biweekly intervals between Ma
rch and September, 1996. Canonical Correspondence Analysis (CCA) was used t
o estimate the influence of abiotic factors and resource availability in st
ructuring the zooplankton assemblage over the season. Repeated Measures Ana
lysis of Variance (ANOVA) was used to determine spatial and temporal variat
ion in zooplankton abundances and to make comparisons between repeated meas
ures ANOVA and CCA in analyzing the zooplankton assemblage. In addition, I
analyzed relationships among cladoceran reproductive parameters (egg ratio,
instantaneous birth rate, reproductive ratio and mean brood size) and envi
ronmental factors over the season using product moment correlation. Results
showed little evidence of bottom-up control of the zooplankton assemblage.
CCA and correlations suggested temperature was the most important factor r
egulating assemblage structure over the season. Several inverse relationshi
ps were seen among cladoceran reproductive parameters and temperature. Decl
ines in Holopedium gibberum Zaddach, Bosmina longirostris Muller and Ceriod
aphnia lacustris Birge during June corresponded with increases in mean temp
erature to above 25 degrees C. Increases in birth rates at the time of popu
lation declines suggested that population declines were a result of increas
ed mortality rates (likely due to high water temperature or predation). Spa
tial variation in the zooplankton assemblage coincided with differences in
both temperature and turbidity among sites. Lower abundances of Daphnia par
vula Fordyce and C. lacustris and a higher abundance of rotifers at the up-
reservoir site coincided with higher mean temperature of the water column a
nd higher turbidity than down-reservoir sites. CCA and ANOVA showed similar
results for the spatial and temporal variation in the zooplankton assembla
ge while CCA provided a more clear approach for analyzing the effects of en
vironmental variables on the assemblage.