Environmental Pollution 141 (2006) 402e408
Identifying primary stressors impacting macroinvertebrates
in the Salinas River (California, USA): Relative effects
B.S. Anderson , B.M. Phillips , J.W. Hunt , V. Connor , N. Richard ,
a Department of Environmental Toxicology, University of California, Davis, CA 95616, USA
b Division of Water Quality, State Water Resources Control Board, 1001 I. Street, Sacramento, CA 95814, USA
Received 8 April 2005; received in revised form 15 August 2005; accepted 26 August 2005
Pesticides are the primary stressor impacting macroinvertebrates in sections of the lower Salinas River.
Laboratory doseeresponse experiments with organophosphate and pyrethroid pesticides, and doseeresponse experiments with increasing
particle loads were used to determine which of these stressors were likely responsible for the toxicity and macroinvertebrate impacts previouslyobserved in the Salinas River. Experiments were conducted with the amphipod Hyalella azteca, the baetid mayfly Procloeon sp., and the midgeChironomus dilutus (Shobanov, formerly Chironomus tentans). The results indicate the primary stressor impacting H. azteca was pesticides,including chlorpyrifos and permethrin. The mayfly Procloeon sp. was sensitive to chlorpyrifos and permethrin within the range of concentrationsof these pesticides measured in the river. Chironomus dilutus were sensitive to chlorpyrifos within the ranges of concentrations measured in theriver. None of the species tested were affected by turbidity as high as 1000 NTUs. The current study shows that pesticides are more importantacute stressors of macroinvertebrates than suspended sediments in the Salinas River. Ó 2005 Elsevier Ltd. All rights reserved.
Keywords: Pesticides; Macroinvertebrates; Toxicity; Suspended particles
tests, chemical analyses and toxicity identification evaluations(TIEs), we recently showed that organophosphate pesticides
The Salinas River is the largest of the three coastal rivers
associated with agriculture drainwater were responsible for sed-
flowing into the Monterey Bay National Marine Sanctuary in
iment and water column toxicity in samples collected in the Sal-
central California. Large areas in this watershed are cultivated
inas River downstream of one of these tributaries (
year-round, primarily in row crops such as lettuce, strawberries,
artichokes, and crucifer crops. Studies have shown that ambient
throid pesticides might also be partially responsible for sedi-
water samples from the river and specific tributaries are toxic to
ment toxicity to the amphipod Hyalella azteca, but these
standard test species in laboratory tests
results were inconclusive due to a lack of pyrethroid analyses
in river samples and limited doseeresponse information forselected pyrethroids using Hyalella (Our previous study also demonstrated
* Corresponding author. c/o Marine Pollution Studies Laboratory, 34500
drainwater impacts on a number of macroinvertebrate commu-
Highway 1, Monterey, CA 93940, USA. Tel.: C1 831 624 0947; fax: C1
nity metrics. There were significant negative correlations
between the number of Ephemeroptera taxa, taxonomic
0269-7491/$ - see front matter Ó 2005 Elsevier Ltd. All rights reserved. doi:10.1016/j.envpol.2005.08.056
B.S. Anderson et al. / Environmental Pollution 141 (2006) 402e408
richness and the percentage Chironomidae and concentrations
three times, with each replicate containing five animals (7e14 days old),
of diazinon and chlorpyrifos in the river. We also found signif-
and C. dilutus treatments were replicated 10 times with one organism per rep-licate (3rd instar). Survival was monitored daily. Dissolved oxygen (mg/L),
icant negative correlations between these metrics and sus-
pH, temperature ( C) were measured at the beginning and end of all experi-
pended particles (measured as turbidity) in the river. Thus, our
ments using meters and probes. These instruments were calibrated in the
results indicated that resident species might be impacted by
laboratory as per manufacturer’s recommendations. Alkalinity (total as
co-occurring stressors (i.e., multiple pesticides, and possibly,
CaCO3) and hardness (calcium as CaCO3) were measured in well water
suspended particles) associated with agriculture drainwater
controls. The test temperature was 23 C. Containers were not aerated.
(Our ability to resolve the relative influ-ences of these stressors on macroinvertebrates was constrained
by a lack of doseeresponse information for pesticides andsuspended particle effects on key resident species.
Mayfly larvae were collected from a reference station in the Salinas River
in May 2000 for diazinon and chlorpyrifos tests, and again in March 2004 for
The current study provides doseeresponse information for
bifenthrin and permethrin tests. This reference station has been used in our
the organophosphate pesticides diazinon and chlorpyrifos,
previous studies, is 11 km upstream of our current study area, and has been
and for suspended particles, using resident and surrogate mac-
demonstrated to have uniformly low pesticide concentrations in sediment
pyrethroid pesticides bifenthrin and permethrin. In terms of
was verified by a qualified taxonomist. Larvae were transported to the lab inriver water then transferred to 20 L plastic trays where they were held until
pounds per acre applied, diazinon, chlorpyrifos, and permethrin
testing. Culture tray water was renewed daily with well water, but mayflies
comprise the most commonly applied pesticides in the Salinas
were not fed. Minor larval mortality was observed during the holding period.
Valley. Bifenthrin is also among the more commonly used py-
Testing commenced within 4 days of the collection date. Larvae of unknown
rethroid pesticides in the Salinas Valley. Experiments were con-
age were used in these experiments. The approximate range of lengths of
ducted using three species: the amphipod H. azteca, the baetid
Proloeon sp. larvae tested was 0.5e1 cm (head to base of cerci). Water-onlydoseeresponse experiments with the organophosphate pesticides were 48 h
mayfly Procloeon sp., and the midge Chironomus dilutus.
exposures, renewed at 24 h. Tests with pyrethroid pesticides were 48 h static
These species were from genera or families that were shown
exposures. Tests were conducted in 200 ml glass bowls containing 100 ml test
to be impacted by agriculture drainwater in previous studies,
solution. Each concentration was replicated 3e5 times, with each replicate
but for which pesticide sensitivities or sensitivities to sus-
containing five animals. Survival was monitored daily. Water quality and tem-
pended particles are unknown. We compared LC50s from these
perature were measured as described above. The animals were not fed and thecontainers were not aerated.
experiments to the ranges and mean concentrations of thepesticides and suspended particles previously measured in the
Salinas River. Current results were combined with previousresults in a weight-of-evidence to determine which are the
Experiments to assess the effects of suspended sediments associated with
most important stressors impacting macroinvertebrates in this
agriculture drainwater were conducted using soil from a certified organic farm.
Approximately 400 L of topsoil was obtained from Blue Heron Farms inWatsonville, California. This farm has been a certified organic operation since
1974 (personal communication Tim Voss, Blue Heron Farms); no pesticideshave been applied to soil on this farm for 30 years. The soil was sun driedand dry sieved to 500 mm. The soil was then suspended in well water and
The pyrethroid pesticides bifenthrin and permethrin were tested with
sequentially wet-sieved to a final sieve size of 64 mm. For these experiments,
H. azteca, C. dilutus, and Procloeon sp., and the organophosphate pesticides
the wet-sieved soil was dissolved in well water in four 114 L plastic bins to
diazinon and chlorpyrifos were tested with Procloeon sp. Doseeresponse
approximate four nominal suspended sediment concentrations that spanned
data from the literature were used to determine the sensitivities of H. azteca
the range reported in Nominal suspended sediment
and C. dilutus to chlorpyrifos and diazinon. Stock solutions of permethrin
concentrations, measured as turbidity, were 0, 250, 500 and 1000 NTUs.
and bifenthrin (100 mg/L in methanol) were obtained from Accustandard
Sediments were kept in suspension by vigorously aerating each bin as their
(New Haven, CT, 100% purity). These were used to prepare nominal concen-
solutions were continuously pumped with a submersible pump (pump
trations of 0, 500, 1000, 5000, 10,000, and 20,000 ng/L for tests with C. dilu-
rate Z 60 L per min) to each of four 13 L head tanks that were also heavily
tus. Secondary stocks (100 mg/L in methanol) were prepared from the primary
aerated to keep the particles in suspension. Turbid water from the head tanks
stocks to give final nominal concentrations of 0, 5.6, 10, 18, 32, and 56 ng/L
flowed by gravity to a manifold fitted with five valves, each supplying water to
for tests with Hyalella and 18, 32, 56, 100, 180, 320, and 560 ng/L for tests
one of five replicate exposure chambers.
with Procloeon. Stock solutions of 250 mg/L chlorpyrifos and diazinon in
Exposure chambers were 1.7 L polyethylene plastic food dishes fitted on
methanol were prepared from pesticides obtained from ChemService
both ends with 2.5 cm diameter 500 mm mesh screens. Each of the replicates
(Westchester, PA, 99% purity). Secondary (2000 and 500 mg/L diazinon and
contained 10 animals (amphipods, chironomids, or mayflies). The water
chlorpyrifos, respectively) and tertiary (20 and 5 mg/L diazinon and chlorpyr-
flowed through the exposure containers and into a catch basin that returned
ifos, respectively) stocks were prepared from these to give final test concentra-
it to the bin supplying that suspended sediment treatment. Approximately
tions of 0.5, 1.0, 2.5, and 5.0 mg/L for diazinon, and 0.0625, 0.125, 0.25, and
300 ml of medium fine-grained sand was added to the exposure chambers
0.50 mg/L for chlorpyrifos. Responses of all animals to all pesticides were com-
for the Procloeon and C. dilutus experiments to provide substrate for these spe-
pared to both well water and methanol controls (1% methanol in well water).
cies. No substrate was used in the Hyalella experiments. The control water forthese experiments was well water and controls for the Procloeon and C. dilutus
2.1. H. azteca and C. dilutus 96-h survival tests
exposure contained a sand substrate as described above. Turbidity was moni-tored at the beginning and end of each day. To account for settlement of sus-
Water-only doseeresponse experiments with H. azteca (provided by
pended sediment during the course of the experiments, additional suspended
Aquatic Biosystems, Fort Collins, CO) and C. dilutus (provided by Chesa-
sediment was added to each treatment after turbidity measurements to return
peake Culture, Hayes, VA) were 96-h static exposures conducted in 20 ml
the concentration to the target nominal concentration. Turbidity was monitored
glass vials containing 15 ml solution. H. azteca treatments were replicated
with a model 2100 turbidimeter (Hach, Loveland, CO). Total suspended solids
B.S. Anderson et al. / Environmental Pollution 141 (2006) 402e408
were measured during one exposure in each nominal turbidity treatment for
comparison using EPA procedures (). Suspended sediment ex-posures were conducted for 96 h, at which time the contents of the chambers
were sieved through a 500 mm mesh screen and survival was recorded.
Measured concentrations of bifenthrin and permethrin were
considerably lower than nominal concentrations in all cases. For bifenthrin experiments with H. azteca, the bifenthrin re-
Selected concentrations of 1 L samples of bifenthrin and permethrin were
covery ranged from 19% to 56%, and average measured con-
measured for comparison to nominal concentrations. Samples for pyrethroid
centrations of bifenthrin were 37% of nominal concentrations.
analyses were prepared by mixing ten 100-ml samples (1 L total), each pre-
For bifenthrin experiments with Procoleon sp., recovery
pared from respective stock solutions of bifenthrin and permethrin. Each sam-ple was mixed at the time of test initiation in 100 ml Erlenmeyer flasks
ranged from 55% to 77%, and average measured concentra-
following the same procedures used for filling the exposure chambers. Pyre-
tions of bifenthrin were 65% of nominal concentrations. For
throid pesticides were measured using Gas ChromatographyeMass Spectros-
bifenthrin experiments with C. dilutus, recovery ranged from
copy (GCeMS; U.S. EPA method 1660) ECD-MS detector following methods
36% to 65%, and average measured concentrations of bifen-
developed by the California Department of Fish and Game Water Pollution
thrin were 54% of nominal concentrations. For permethrin ex-
Control Laboratory (reporting limit bifenthrin and permethrin Z 0.01 mg/Land 0.02 mg/L, respectively). Chlorpyrifos and diazinon were measured using
periments with H. azteca, recovery ranged from 0% to 61%,
two methods, Enzyme Linked Immunosorbent Assays (ELISAs
and average measured concentrations of permethrin were
scribed below), and GCeMS (U.S. EPA methods 8140 and 8141A). Standard
54% of nominal concentrations For permethrin ex-
quality assurance procedures including measurement of standard reference
periments with Procoleon sp., recovery ranged from 32% to
materials and quantification of surrogate recoveries and matrix spikes were
61%, and average measured concentrations of permethrin
used in all analyses. All chemical analyses met prescribed quality assuranceguidelines.
were 43% of nominal concentrations ). For permethrinexperiments with C. dilutus, recovery ranged from 61% to75%, and average measured concentrations of permethrin
were 68% of nominal concentrations Percent recov-eries of laboratory control spikes of bifenthrin and permethrin
All chlorpyrifos and diazinon concentrations were measured using Enzyme
in water during chemical analyses exceeded quality assurance
Linked Immunosorbent Assays (ELISAs) following procedures recommendedby . ELISA readings were compared to a five-pointstandard curve, using standards provided by the manufacturer. After analysisof a group of samples, accuracy of the ELISA method was determined by mea-
suring an external chlorpyrifos or diazinon standard. All standard measure-
Nominal and measured concentrations (ng/L) of diazinon, chlorpyrifos,
ments were within G20% of nominal. Precision of the ELISA method was
permethrin and bifenthrin in water-only doseeresponse experiments with
determined with duplicate measures of one sample by calculating the coeffi-
cient of variation. CVs were always less than 20. The lowest detectable
dose was 30 ng/L for diazinon and 50 ng/L for chlorpyrifos.
Median effect concentrations (LC50s) were calculated from mean mea-
sured organophosphate concentrations and nominal pyrethroid concentrations
using (ToxCalcÔ Statistical Software, Tidepool Software, McKinleyville,
CA), using the trimmed SpearmaneKarber method (
The doseeresponse information resulting from the pesticide and suspended
particle exposures was compared to data from our Salinas River study to de-
termine whether effect thresholds were within the range of pesticide or sus-
pended sediment concentrations measured in the river. For this comparison,
we used the mean and range of diazinon and chlorpyrifos concentrations mea-
sured at the station with the highest pesticide concentrations in our previousstudy. These concentrations were measured at Station #2, which was located
at the confluence of the agricultural drainage creek and the Salinas River
We also compared the turbidities from Station #2
in that study to those in the current doseeresponse experiments. Pyrethroid
pesticides were not measured in our previous study, so to investigate the likeli-
hood of exposure to these pesticides, we relied on pyrethroid concentrations
reported as part of a California Department of Pesticide Regulation studyThese authors reported concentrations of pyreth-
roids in water and sediments sampled weekly over 16 weeks from June
through September, 2003 from a station in the agriculture drainage creek
0.5 km upstream of our Station #2 from . The mean
and range of these measures were used to estimate the mean and range of con-
centrations of permethrin in the Salinas River at Station #2 (these authors didnot detect any bifenthrin in their study).
B.S. Anderson et al. / Environmental Pollution 141 (2006) 402e408
thresholds. The range of percent recoveries of bifenthrin was
bifenthrin and permethrin toxicity to Procloeon sp. were
89e116% (mean percent recovery Z 102%). The range of per-
84.3 and 89.6 ng/L, respectively ). The permethrin
cent recoveries of permethrin was 69e115% (mean percent
LC50s were within the mean and range of permethrin concen-
trations in water in this system reported by
Enzyme Linked Immunosorbent Assays (ELISAs) of diaz-
. The mean and range of permethrin concentration
inon and chlorpyrifos in the Procloeon sp. experiments
reported by these authors were 104.8, and 71.2e162 ng/L,
showed that nominal and measured concentrations were com-
respectively (These authors did not detect any
parable (Measured concentrations of diazinon in the
experiments with Procloeon sp. ranged from 118% to 127% of
H. azteca was more sensitive than Procloeon sp. to both
the nominal concentrations. Measured concentrations of chlor-
bifenthrin and permethrin. The mean LC50s for bifenthrin
pyrifos in the experiments with Procloeon sp. ranged from
and permethrin toxicity to H. azteca were 9.3 and 21.1 ng/L,
79% to 118% of the nominal concentrations ().
respectively (). The permethrin LC50 was also within
The LC50s for all diazinon and chlorpyrifos tests with
the mean and range of permethrin concentrations in water in
C. dilutus are based on measured concentrations. The LC50s
for all pyrethroid pesticides used in these experiments are pre-
The midge C. dilutus was relatively insensitive to bifenthrin
sented as nominal concentrations. For the experiments with
and permethrin. The mean LC50s for bifenthrin and permeth-
diazinon and chlorpyrifos we have shown that the nominal
rin toxicity to C. dilutus were 26,150 and 10,450 ng/L, respec-
concentrations were reasonable approximations of the mea-
tively (). The permethrin LC50 was well above the
sured concentrations. The actual LC50s and LOECs for bifen-
mean (104.8 ng/L) and range (71.2e162 ng/L) of permethrin
thrin and permethrin for Hyalella, Procloeon, and C. dilutus
concentrations in this system reported by
are probably considerably lower than those reported here.
Based on the fact that recoveries of spiked pyrethroids mea-
Published doseeresponse data for diazinon and chlorpyrifos
sured in the laboratory analyses were acceptable, it is likely
toxicity to C. dilutus were used to assess risk of these pesticides
that lower recoveries in samples collected at the initiation of
to chironomids in the Salinas River. The LC50 for chlorpyrifos
the tests were the result of loss of pyrethroids to the sides of
toxicity to Chironomus tentans (C. dilutus) reported by
was 70 ng/L, lower than the range of chlorpyrifosconcentrations we measured in our study (48e515 ng/L;
The 96-h LC50 for diazinon toxicity to C. tentans (C.
The mayfly Procloeon was sensitive to chlorpyrifos within
much higher than the range of diazinon concentrations we
the range of chlorpyrifos concentrations measured in the
measured in our previous study (190e790 ng/L; ).
Salinas River in our previous study. The mean LC50 for chlor-pyrifos toxicity to Procloeon was 81 ng/L. The mean concen-
tration of chlorpyrifos measured at the most contaminatedstation in the Salinas River in our previous study was
There were no apparent effects of suspended particles on
mayflies, amphipods, or midges in our experiments. Mean sur-
concentrations previously measured in the river was 48e
vival of Procloeon at the highest turbidity tested, 1000 NTUs
515 ng/L ). Procloeon was less sensitive to diazinon.
(nominal), was 86.7%, while mean survival in the controls was
The mean LC50 for diazinon was 1930 ng/L, which is greater
73.3% (). Mean survival of Hyalella at 1000 NTUs was
than the concentrations of diazinon we previously measured in
98%, while mean control survival was 90.3%. Mean survival
the river. The mean concentration of diazinon measured in the
of C. dilutus at 1000 NTUs was 94.3%, while mean control
Salinas River in our previous study was 460 ng/L, and the
survival was 94.7%. Survival of all species tested at all lower
range of concentrations measured was 190e790 ng/L.
turbidities was equal to or greater than their survival in the
Procloeon sp. were relatively sensitive to the pyrethroid
controls. Turbidities measured throughout the experiments
pesticides bifenthrin and permethrin. The mean LC50s for
Sensitivity of the amphipod Hyalella azteca to selected pesticides relative to
Sensitivity of the baetid mayfly Procloeon sp. to selected pesticides relative to
concentrations measured in the Salinas River in ng/L
concentrations measured in the Salinas River in ng/L
a Concentrations measured at the most impacted station, see text for
a Concentrations measured at the most impacted station, see text for
B.S. Anderson et al. / Environmental Pollution 141 (2006) 402e408
suspended sediment concentrations (as turbidity). When com-
Sensitivity of the midge Chironomus dilutus to selected pesticides relative to
bined with previous measures of pesticide concentrations,
concentrations measured in the Salinas River in ng/L
TIEs, and doseeresponse information from the literature, re-
sults from the current study help resolve the relative contribu-
tions of these stressors in this system.
Our previous data showed significant toxicity to the amphi-
pod H. azteca at stations downstream of an agriculture drain
where high concentrations of organophosphate pesticides
were measured, and where amphipod field densities were im-
Concentrations measured at the most impacted station, see text for
pacted. Toxicity identification evaluations showed that sedi-
ment toxicity was due to mixtures of the organophosphate
pesticide chlorpyrifos, and some other non-metabolically acti-vated pesticide ().
were somewhat lower than the nominal values, due to settle-
TIE evidence in these studies included increased mortality of
ment of particles throughout the night ). For example,
amphipods with the addition of the metabolic inhibitor piper-
measured turbidities in the 1000 NTU treatment ranged be-
onyl butoxide, which may suggest toxicity due to pyrethroid
tween 755.9 and 909.8. The mean measured turbidities in tests
pesticides (). Conclusive evidence of pyre-
with Procloeon sp., H. azteca and C. dilutus in the 1000 NTU
throid toxicity was constrained by a lack of doseeresponse in-
treatment were 840, 836 and 824 NTUs, respectively. Despite
formation with H. azteca for selected pyrethroids, and absence
the variability of suspended sediment in these experiments, the
of pyrethroid measurements in field sediments in our study
range of turbidities was comparable to the range we previously
measured in the Salinas River. The mean turbidity measured in
ent study, we found that H. azteca is sensitive to the pyrethroid
the river in the previous study was 521.4 NTUs, and the range
pesticide permethrin within the range of permethrin concentra-
tions measured in this system. The mean LC50 for permethrin
suspended solid (TSS) concentrations corresponded to the
toxicity to H. azteca in water is 21.1 ng/L California
measured turbidities in these experiments. The mean TSS
Department of Pesticide Regulation recently reported mean
measured in the 250 NTU treatment was 297.7 mg/L. The
water concentrations of permethrin in this system in 16 weekly
mean TSS in the 500 NTU treatment was 483 mg/L, and the
mean TSS in the 1000 NTU treatment was 848.7 mg/L ).
concentrations were measured in the agriculture drainagecreek approximately 0.5 km upstream of Salinas River Station#2, the station where our previous TIE work was conducted.
While we found strong negative correlations between turbidityand macroinvertebrate densities (), our
Our approach to identifying the primary stressors impacting
current data show that H. azteca tolerate concentrations of sus-
macroinvertebrate communities in the Salinas River followed
pended particles as high as those measured in the river (1000
an iterative process involving an initial toxicity assessment
NTUs; When data from these studies are considered
that described water column toxicity in selected agriculture
as a weight-of-evidence, they confirm that one of the primary
stressors impacting H. azteca in our study area on the Salinas
more detailed studies that demonstrated effects in the river
River was the organophosphate pesticide chlorpyrifos, and in-
dicate that the pyrethroid pesticide permethrin is also a likely
important stressor to amphipods in this system.
that Ceriodaphnia survival in toxicity tests and macroinverte-
Our results suggest that chlorpyrifos and permethrin also
brate densities were negatively correlated with the organo-
impact the baetid mayfly Procloeon sp. in this system.
phosphate pesticides diazinon and chlorpyrifos, and with
Procloeon sp. were sensitive to chlorpyrifos within the mean
Table 5Effects of suspended particles on survival of Procloeon sp., H. azteca, and C. dilutus in 96-h experiments (results from three experiments for each species)
Range concentrations measured in the rive
a Concentrations measured at the most impacted station, see text for explanation.
B.S. Anderson et al. / Environmental Pollution 141 (2006) 402e408
and range of concentrations measured at Station #2
drainwater, the consistency of the input during the growing
Procloeon sp. was also sensitive to permethrin within the
season constitutes chronic exposure. The acute LC50s used
mean and range of permethrin concentrations reported by
to determine risk of diazinon, chlorpyrifos and permethrin to
resident macroinvertebrates in the current study likely under-
tolerated turbidities as high as those measured in our previous
estimate chronic risk of these pesticides to Hyalella, Pro-
study, suggesting this is a less important acute stressor than
cloeon, and chironomids. In addition, pesticides in this
system may influence macroinvertebrate community structure
C. dilutus was used as a surrogate to assess the relative sen-
through behavioral or indirect mechanisms. These include
sitivity of chironomids to pesticides and suspended sediments
sublethal influences on drift and predator avoidance behavior
in this system. Previous results showed that chironomid densi-
ties declined downstream of the agriculture drain input and
exposures that only quantify mortality due to single chemicals
that their densities were negatively correlated with diazinon
may significantly underestimate sublethal risk due to mixtures
and chlorpyrifos concentrations and suspended sediment con-
of organophosphate and pyrethroid pesticides. The relative ef-
centrations. Doseeresponse data from the literature indicate
fects of suspended sediments on pesticide mixtures is beyond
chironomids are very sensitive to chlorpyrifos and less sensi-
the scope of this study, but previous work has shown that in the
tive to diazinon in laboratory studies. re-
case of more hydrophobic pesticides such as chlorpyrifos and
ported a 10-day LC50 for chlorpyrifos toxicity to C. tentans
pyrethroids, addition of sediment decreases toxicity of chlor-
(dilutus) of 70 ng/L. The mean chlorpyrifos concentration
measured in the Salinas River in our previous study was
) by reducing their bioavailability in water column toxic-
ity tests. In addition, pesticide impacts on macroinvertebrate
for diazinon toxicity to C. dilutus reported in
populations may be tempered by additional biotic factors
was 30,000 ng/L. The mean diazinon concentra-
such as development of chemical resistance after prolonged
tion previously measured in the river was 460 ng/L
exposure to pesticides, influences of habitat refugia allowing
Assuming C. dilutus is representative of other chironomids in
for recolonization, and reduced bioavailability of pesticides
the Salinas River, these results suggest that chlorpyrifos is
a potentially important stressor to midge larvae in this system.
Despite the limitations of the current study, the weight-of-
As with the other resident species we investigated, C. dilutus is
evidence of our lab and field work in the Salinas River
not acutely sensitive to suspended particles. Thus, although we
demonstrates that pesticides are important stressors of macro-
found strong negative correlations between macroinvertebrate
invertebrates in parts of this system. Based on the current
densities and turbidity in our previous study, this likely re-
work, we conclude that suspended sediments associated with
sulted from the co-occurrence of suspended particles and pes-
agriculture drainwater probably play a minor role in directly
ticides, in particular chlorpyrifos. Our current results show that
affecting key components of aquatic invertebrates communi-
C. dilutus is relatively insensitive to permethrin and bifenthrin.
ties in our study area, and that organophosphate and pyrethroid
The LC50s for permethrin was well above the mean and range
pesticides have a greater potential for impacting these
of concentrations measured in this system, and no bifenthrin
was detected (We could find no published data on
There is growing awareness of environmental problems
bifenthrin toxicity to this species, but data for permethrin sug-
associated with agriculture runoff in Central California, and
gest that C. dilutus (LC50 Z 10,450 ng/L) is considerably less
growers have organized to form watershed monitoring groups
sensitive to this pesticide than other species in this genus.
to better understand the extent and associated impacts of pes-
The LC50s for permethrin toxicity to the midges C. plumulo-
ticide pollution in this region. In addition, through cooperative
sus and C. salinarius were 560 and 73 ng/L, respectively
efforts of a number of stakeholders, on-farm practices to min-
imize pesticide runoff are being actively investigated. Ours
Our current data using three representative macroinverte-
and similar studies have been helpful in identifying the most
brates suggest that suspended particles are less important
important pesticides to target for reduction in drainwater
stressors in our study area in the Salinas River, and that macro-
runoff. Future monitoring will be used to determine which
invertebrate declines were caused by pesticides. These experi-
practices are most efficient at reducing these chemicals.
ments underestimated chronic and interactive effects ofpesticides and suspended sediments. In the case of diazinonand chlorpyrifos, previous reports have shown that toxicity
of these pesticides are additive in mixtures and others have shown interactive effects of pyrethroid
Anderson, B.S., Hunt, J.W., Phillips, B.M., Nicely, P.A., Gilbert, K.D., de
and organophosphate pesticides in mixtures (
Vlaming, V., Connor, V., Richard, N., Tjeerdema, R.S., 2003a. Ecotoxico-
logic impacts of agriculture drainwater in the Salinas River (California,
Our previous studies have shown that pesticide-contaminated
Anderson, B.S., Hunt, J.W., Phillips, B.M., Nicely, P.A., de Vlaming, V.,
agriculture drainwater enters the Salinas River on a daily basis
Connor, V., Richard, N., Tjeerdema, R.S., 2003b. Integrated assessment
of the impacts of agricultural drainwater in the Salinas River (California,
daily fluctuations in the concentrations of pesticides in the
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G A S T R O I N T E S T I N A L N U R S I N GEffect of nurse-led gut-directed hypnotherapy upon health-relatedquality of life in patients with irritable bowel syndromeGraeme D Smith BA, PhD, RGNLecturer, School of Health in Social Science, University of Edinburgh, Old Medical School, Edinburgh, UKSubmitted for publication: 29 July 2004Accepted for publication: 4 July 2005Journal of Clinical Nu
Gláuks v. 10 n. 1 (2010) 243-270 A Recontextualização da Informação sobre a “Pílula Anti-Barriga” nos S ites Folha e Minha Vida The Recontextualization of Information about the “Anti-Belly Pill” in “Folha” and “Minha Vida” Websites RESUMO: Este trabalho pretende analisar o tratamento linguístico-discursivo dado às informações de caráter c