Big Base and Little Base Lakes are located on
Little Rock Air Force Base, Arkansas, and their close
proximity to a dense residential population and an
active military/aircraft installation make the lakes
vulnerable to water-quality degradation. The U.S.
Geological Survey (USGS) conducted a study from
June through August 2015 to investigate the effects of
water quality on phytoplankton species and density and
trophic state in Big Base and Little Base Lakes, with
particular regard to nutrient concentrations. Nutrient
concentrations, trophic-state indices, and the large part
of the phytoplankton biovolume composed of
cyanobacteria, indicate eutrophic conditions were
prevalent for Big Base and Little Base Lakes,
particularly in August 2015. Cyanobacteria densities
and biovolumes measured in this study likely pose a
low to moderate risk of adverse algal toxicity, and the
high proportion of filamentous cyanobacteria in the
lakes, in relation to other algal groups, is important
from a fisheries standpoint because these algae are a
poor food source for many aquatic taxa. In both lakes,
total nitrogen to total phosphorus (N:P) ratios declined
over the sampling period as total phosphorus
concentrations increased relative to nitrogen
concentrations. The N:P ratios in the August samples
(20:1 and 15:1 in Big Base and Little Base Lakes,
respectively) and other indications of eutrophic
conditions are of concern and suggest that exposure of
the two lakes to additional nutrients could cause
unfavorable dissolved-oxygen conditions and increase
the risk of cyanobacteria blooms and associated
cyanotoxin issues.
