Environmental Engineering Reference
In-Depth Information
California ponds
. Two studies on fates and effects of CPY were conducted in
outdoor experimental ponds at Riverside, California (Hurlburt et al.
1970
;
1972
). In
the fi rst study, ponds were sprayed four times at 2-wk intervals at initial concentra-
tions from 2 to 200
g L
−1
. In the second study, ponds were sprayed three times at
2-wk intervals to produce concentrations of 7.2
μ
g L
−1
. In both
studies, the dominant zooplankton species,
Cyclops vernalis
and
Moina micrura
,
were reduced, while
Diaptomus pallidus
and rotifers (especially
Asplanchna bright-
welli
) increased. The increases in
D. pallidus
and rotifers were attributed to reduced
predation and competition.
C. vernalis
and
M. micrura
recovered in 1-3 wk at
7.2
μ
g CPY L
−1
and 72
μ
g L
−1
. Predaceous insects (notonectids and corixids)
were affected and recovered slowly, while herbivorous insects were less affected
and recovered more quickly. No effects were observed on the mosquitofi sh
(
Gambusia affi nis
).
μ
g L
−1
and in 3-6 wk at 72
μ
Minnesota littoral enclosures
. In situ enclosures in the littoral region of a pond in
Duluth, Minnesota were sprayed once with CPY to produce initial concentrations of
0.5, 5, and 20
g L
−1
(Brazner and Kline
1990
; Siefert et al.
1989
). Cladocerans (fi ve
species) and ostracods (
Cyclocypris
) decreased 4 d after treatment. Densities of
copepods were slightly reduced in treated enclosures but were not signifi cantly less
than controls. Rotifers were reduced at 0.5
μ
g L
−1
, but were unaffected (or increased)
at the greater concentrations. Chironomids (the dominant insect group) were
reduced 4 d after treatment; they recovered within 16 d at 0.5
μ
g L
−1
, but remained
less abundant than controls after 32 d at the greater concentrations. Other insects
and the amphipod,
Hyalella azteca
, were reduced. Snails, planaria, and protozoa
were unaffected or increased. Survival of bluegill sunfi sh (
L. macrochirus
) decreased
at 5 and 20
μ
g L
−1
. Survival of fathead minnows (
Pimephales promelas
) was unaf-
fected, but the study authors reported that
P. promelas
growth was reduced due to a
reduction in invertebrate abundance. As discussed by Giesy et al. (
1999
), the data
from the study do not support this interpretation, and the effect on growth of
P. promelas
, if real, remains unexplained.
μ
Kansas outdoor cosms
. Outdoor pond cosms in Kansas were treated with CPY with
initial concentrations of 0.03, 0.1, 0.3, 1, and 3
g L
−1
(Biever et al.
1994
; Giddings
1993a
,
b
; Giddings et al.
1997
; Giddings
2011
). In separate series of cosms, applica-
tions were made as a single surface spray, three CPY-treated slurry applications at
2-wk intervals, and a combination of the two. Results were similar in all three series,
and only the single spray treatment will be summarized here.
The total abundance of copepods was reduced for 3 d at 0.3
μ
μ
g CPY L
−1
(recov-
ery by d-15), for 29 d at 1
μ
g L
−1
(recovery by d-43), and for 22 d at 3
μ
g L
−1
(recov-
ery by d-29). No effects were observed at 0.1
g L
−1
. The calanoid copepod
D. pallidus
was a notable exception to the general sensitivity of the copepods: at the
highest treatment level (3
μ
g L
−1
)
D. pallidus
increased soon after the chlorpyrifos
application. An increase in
D. pallidus
after chlorpyrifos treatment was also
observed by Hurlbert et al. (
1972
), who noted that the increase took place only after
numbers of
C. vernalis
had decreased. The numbers of cyclopoids, as well as most
calanoids other than
D. pallidus
, were also reduced in the Kansas cosms.
μ
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