Environmental Engineering Reference
In-Depth Information
Dutch ditch cosms
. CPY has been the subject of several studies in indoor and
outdoor cosms representing Dutch ditches at the Winand Staring Center, The
Netherlands. The indoor cosms (Brock et al.
1992
;
1993
;
1995
; Cuppen et al.
1995
;
van den Brink et al.
1995
; Van Donk et al.
1995
) were sprayed once, with an initial
concentration of 35
g CPY L
−1
. Direct effects were observed on cladocerans, cope-
pods, amphipods, isopods, and insects. An algal bloom occurred, as had also been
observed in the California ponds (Hurlburt et al.
1970
;
1972
) and in the Minnesota
enclosures (Siefert et al.
1989
). The researchers documented the recovery of the
cosm-invertebrates as concentrations of CPY declined. Copepods and some cladoc-
eran populations recovered when concentrations of CPY reached 0.2
μ
μ
g L
−1
; other
cladocerans recovered when concentrations fell to 0.1
g L
−1
. Taxa with no recolo-
nization sources (such as insects, amphipods, and isopods) did not recover, but cage
studies showed that
Asellus aquaticus
could survive when concentrations decreased
to 1.3
μ
g L
−1
; and
Chaoborus obscuripes
,
Cloeon dipterum
,
Gammarus pulex
could
survive when concentrations reached 0.2
μ
g CPY L
−1
.
The outdoor ditch enclosures were sprayed once with CPY concentrations of 0.1,
0.9, 6, and 44
μ
g L
−1
(van den Brink et al.
1996
; van Wijngaarden et al.
1996
). No
effects were observed at 0.1
μ
g L
−1
. At greater concentrations, numbers of macroin-
vertebrates were reduced and shifts were observed in the relative abundance of dif-
ferent functional groups (reductions in the proportion of gatherers, increases in the
proportions of fi lter feeders and shredders). Most taxa, other than
G. pulex
, recov-
ered rapidly at all concentrations.
G. pulex
could not recover because there was no
source of recolonization.
In further studies, macrophyte-dominated outdoor Dutch ditch cosms were
treated with CPY under three different exposure regimes: a single application of
0.9
μ
μ
g L
−1
, three applications of 0.3
μ
g L
−1
at 7-d intervals, and continuous applica-
tion of 0.1
g L
−1
for 21 d using a pump (Zafar et al.
2011
). The three exposure
regimes were designed to produce similar 21-d time-weighted averages of 0.1
μ
g L
−1
.
Under all exposure regimes, cladocerans and copepod nauplii were the most sensi-
tive taxa of zooplankton, while numbers of rotifers increased.
C. dipterum
and
Chaoborus
sp. were the most sensitive taxa of macroinvertebrates. In both the zoo-
plankton and insect communities, effects were observed immediately after the sin-
gle application of 0.9
μ
g L
−1
but occurred more slowly in the other treatments.
Overall, effects on both the zooplankton and macroinvertebrate communities were
more or less the same under all exposure regimes.
μ
Indoor cosms simulating Mediterranean environments
. Indoor, plankton-dominated
microcosms were used to compare the responses of aquatic communities to CPY
under conditions pertaining to Mediterranean regions (higher temperature and
greater amounts of nutrients) with conditions representing cool temperate regions
(van Wijngaarden et al.
2005a
). CPY was applied once to give concentrations from
0.01 to 10
g L
−1
in water of microcosms. CPY dissipated more rapidly under
Mediterranean than temperate conditions. As in previous studies, cladocerans and
copepod nauplii were among the most sensitive taxa of zooplankton, while numbers
of rotifers and adult copepods generally increased as the other groups declined.
μ
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