Ac. Benke et Di. Jacobi, PRODUCTION DYNAMICS AND RESOURCE UTILIZATION OF SNAG-DWELLING MAYFLIES IN A BLACKWATER RIVER, Ecology, 75(5), 1994, pp. 1219-1232
We quantified production dynamics, determined the trophic basis of pro
duction, and assessed the overlap in resource utilization within a div
erse assemblage of mayfly larvae from the submerged woody (snag) habit
at of a Coastal Plain blackwater river (Ogeechee River). Total annual
production (as dry mass) was among the highest reported for mayflies,
ranging from 20.8 to 42.2 g/m(2) of snag surface (7.4 to 12.3 g/m(2) o
f channel bottom) in two consecutive years. Relatively little change o
ccurred between years for four out of six families. Biomass turnover r
ates (annual production/biomass) were generally high, ranging from 8 (
single generation per year) to 96 (multiple generations per year) for
individual taxa. Distinct types of temporal production patterns occurr
ed: (1) concentration in winter (Ephemerella argo, E. dorothea, Eurylo
phella sp., and Isonychia), (2) concentration in summer (Baetis ephipp
iatus, Tricorythodes sp., Caenis spp.), or (3) spread throughout the y
ear and peaking in summer (Baetis intercalaris, Stenonema modestum, S.
integrum, S. exiguum, and Hexagenia sp.). Temporal overlap of product
ion, using the proportional similarity index, was highest among closel
y related taxa (>0.60), with the least overlap (<0.15) among taxa in d
ifferent families. Overlap based upon the amount that various food typ
es contribute to production was high among all species, suggesting eve
n less resource partitioning for food than for time. Of the. annual fo
od consumption (as dry mass) by mayflies per unit snag surface area (4
23 g.m(-2).yr(-1)), approximate to 87% consisted of amorphous detritus
that is rapidly replenished on snags from floodplain-derived seston.
This food source accounted for approximate to 70% of total mayfly prod
uction. We suggest that a fluctuating habitat (snags), a continuously
replenished food supply, high biomass turnover, and high drift densiti
es help perpetuate a persistent, resilient, and diverse mayfly assembl
age with little resource partitioning.