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Effectiveness of EarthTec (R) for killing invasive quagga mussels (Dreissena rostriformis bugensis) and preventing their colonization in the Western United States


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Quagga mussels (Dreissena rostriformis bugensis) have created economic and ecological impacts in the western United States since their discovery in 2007. This study focuses on chemical control for preventing the spread of these mussels. The effectiveness of EarthTec® in killing quagga mussels (adults, juveniles, and veligers) in Lake Mead, Nevada-Arizona, was evaluated over time across six concentrations: 0, 1, 5, 10, 17, and 83 ppm. One hundred percent mortality of adult and juvenile mussels was achieved after 96 h with 17 ppm and 5 ppm (respectively), and 100% veliger mortality occurred within 30 min at 3 ppm. From December 2010 to February 2011, the effectiveness of EarthTec® in preventing veliger colonization was also evaluated and the results showed that 2.8 ppm was effective in preventing veliger colonization on fiberglass panels. This study indicates that EarthTec® has the potential to be an effective control agent against the invasive quagga mussel, and more specifically, in preventing the colonization of veligers.
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Effectiveness of EarthTec® for killing invasive
quagga mussels (Dreissena rostriformis bugensis) and
preventing their colonization in the Western United
Ashlie Watters a , Shawn L. Gerstenberger a & Wai Hing Wong a b
a Department of Environmental and Occupational Health, University of Nevada Las Vegas,
4505 Maryland Parkway, Las Vegas, NV, 89154-3064, USA
b Department of Biology, State University of New York at Oneonta, 108 Ravine Parkway,
Oneonta, NY, 13820, USA
To cite this article: Ashlie Watters , Shawn L. Gerstenberger & Wai Hing Wong (2013): Effectiveness of EarthTec® for killing
invasive quagga mussels (Dreissena rostriformis bugensis) and preventing their colonization in the Western United States,
Biofouling: The Journal of Bioadhesion and Biofilm Research, 29:1, 21-28
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Effectiveness of EarthTec
for killing invasive quagga mussels (Dreissena rostriformis bugensis)
and preventing their colonization in the Western United States
Ashlie Watters
, Shawn L. Gerstenberger
and Wai Hing Wong
Department of Environmental and Occupational Health, University of Nevada Las Vegas, 4505 Maryland Parkway, Las Vegas,
NV 89154-3064, USA;
Department of Biology, State University of New York at Oneonta, 108 Ravine Parkway, Oneonta, NY
13820, USA
(Received 16 May 2012; final version received 25 October 2012)
Quagga mussels (Dreissena rostriformis bugensis) have created economic and ecological impacts in the western
United States since their discovery in 2007. This study focuses on chemical control for preventing the spread of these
mussels. The effectiveness of EarthTec
in killing quagga mussels (adults, juveniles, and veligers) in Lake Mead,
Nevada-Arizona, was evaluated over time across six concentrations: 0, 1, 5, 10, 17, and 83 ppm. One hundred
percent mortality of adult and juvenile mussels was achieved after 96 h with 17 ppm and 5 ppm (respectively), and
100% veliger mortality occurred within 30 min at 3 ppm. From December 2010 to February 2011, the effectiveness
of EarthTec
in preventing veliger colonization was also evaluated and the results showed that 2.8 ppm was
effective in preventing veliger colonization on fiberglass panels. This study indicates that EarthTec
has the
potential to be an effective control agent against the invasive quagga mussel, and more specifically, in preventing the
colonization of veligers.
Keywords: Dreissena rostriformis bugensis; quagga mussel; EarthTec
; copper sulfate; molluscicide; chemical
control; biofouling
The zebra (Dreissena polymorpha) and the quagga
mussel (Dreissena rostriformis bugensis) have become
arguably the most serious nonindigenous biofouling
pests introduced into North American freshwater
systems (LaBounty & Roefer 2007). The economic
impact of zebra and quagga mussels in North America
has been estimated at $1 billion a year (United States
Army Corps of Engineers 2002). The speed at which
the quagga mussel has spread throughout the south-
western United States is unprecedented (Benson 2011;
Wong & Gerstenberger 2011). In addition to invading
the Great Lakes region, the quagga mussel was
subsequently discovered in Lake Mead in 2007
(LaBounty & Roefer 2007), and following establish-
ment has resulted in significant economic impacts. For
example, the mussels clog water intake pipes and
disrupt water filtration in electric generating plants and
water treatment facilities. They also affect boat motors,
damage recreational equipment, and once established
in the lake, routine maintenance is necessary to avoid
additional impairment. The cost in the western United
States will be significant with the further spread to
uninfested bodies of water (Turner et al. 2011). Quagga
mussels also alter the ecosystem by increasing water
clarity and bioaccumulating contaminants. With their
efficient filtering capabilities, quagga mussels remove
suspended food particles from the water column,
including detritus, phytoplankton and bacterioplank-
ton, reducing availability for native filter-feeding
aquatic species (Claudi & Mackie 1994; Strayer et al.
1999; Karatayev et al. 2007; Nalepa et al. 2009).
Chemical means are the most commonly used
methodology in both the United States and Europe to
control zebra and quagga mussel macrofouling (Claudi
& Mackie 1994). Following the introduction of
nonindigenous zebra and quagga mussels to North
America, a number of chemicals with unknown and
known molluscicidal properties were proposed for use
in controlling invasive molluscs (Sprecher & Getsinger
2000). The most popular and least expensive chemical
used for control of invasive mussels is chlorine, where
it is added as chlorine gas or as liquid sodium
hypochlorite (Claudi & Mackie 1994; Rajagopal
et al. 1996; Sprecher & Getsinger 2000). Chlorine is
beneficial because it is effective at low concentrations
and efficient against all fouling categories ranging from
bacteria to molluscs. It not only kills adult quagga
mussels, but is effective in preventing embryonic forms
(ie veligers) from settling in raw water piping systems
*Corresponding author. Email:
Biofouling, 2013
Vol. 29, No. 1, 21–28,
Ó2013 Taylor & Francis
Downloaded by [State University College], [Wai Hing Wong] at 20:37 30 November 2012
which can increase the efficiency of the water facility
(Jenner & Janssen-Mommen 1993). Chlorine controls
mussels through an oxidation process either directly on
the adults or through inhibition of settlement and
growth of the veligers. Adult mussels can sense the
presence of chlorine in low doses to which they
respond by shutting their valves resulting in cessation
of filter-feeding and dependence on anaerobic meta-
bolism (Rajagopal et al. 1997, 2002). Because mussels
try to avoid the chemical, they may die from
asphyxiation or metabolic acidosis induced by anae-
robic metabolism over a prolonged period (Van
Benschoten et al. 1995). Trihalomethanes (THMs)
are formed as by-products of chlorination when it is
used to disinfect drinking water. These byproducts are
formed when chlorine reacts with organic or inorganic
material already present in the water being treated.
THMs are linked to adverse health effects and can be
carcinogenic to animals (Cotruvo & Regelski 1989).
The US Environmental Protection Agency (US EPA)
set a standard for the maximum allowable annual
average concentration level of total THMs of 80 ppb
(US EPA 2010). Water treatment facilities that use
chlorine as a preventative measure against veliger
colonization must monitor total THM production to
avoid hazardous limits. In cases where THM exceeds
the US EPA’s limit, an alternative form of chemical
control needs to be implemented.
is a proprietary copper chemical that
may be used as a chemical control method for quagga
and zebra mussels. It is formulated by blending copper
sulfate pentahydrate with Earth Science Laboratory’s
base acid. EarthTec
is registered with the US EPA as
an algicide/bactericide and certified as a drinking water
additive. It is commonly used in lakes, ponds,
reservoirs, and municipal drinking and wastewater
systems. The biologically active ingredient in Earth-
is the cupric ion form of copper (Cu
Quagga mussels have been threatening the local
ecosystem and environments since their introduction,
and currently there is not a single method that will
eliminate the problem. The objective of the present
study was to determine the lethal dose of EarthTec
for quagga mussels, and to test the effectiveness of this
agent in preventing settlement by quagga mussel
veligers. This information will be useful as an added
option for the management of quagga mussel
Materials and methods
Lethal effects of EarthTec
on quagga mussels
Specimen collection and holding conditions
In November, December, and January 2010–2011,
adult, juvenile, and veliger specimens of D. rostriformis
bugensis were collected from Lake Mead, Nevada-
Arizona, USA (3681050.690N; 114846012.950W). Adults
and juveniles were collected from rope substrata at
depths of 10–20 m, and veligers were collected at 30 m
using a 64 mm pore size plankton net (Gerstenberger
et al. 2011). A National Park Service permit was
obtained, granting permission to collect quagga
mussels. Immediately following collection, the samples
were brought back to the Nevada Department of
Wildlife’s (NDOW) hatchery in Boulder City, NV to
acclimate for 5 days, in 10 gallon (¼37.9 1) tanks. The
aquaria used to acclimate adult and juvenile mussels
contained water taken from a flow through system
carrying water pumped directly from Lake Mead. The
water in the aquaria was continuously aerated with air
stones and the temperature was recorded daily. Adults
(411 mm) and juveniles (511 mm) were divided and
placed into twenty four, 800 mm fine media mesh bags
with 12–15 mussels per bag. Veligers were divided into
small, glass Petri dishes for the toxicity experiment, or
divided into the 10 gallon tanks for the colonization
experiment. Twelve tanks equipped with air stones
were used and filled with 25 l of raw Lake Mead water.
Adult, juvenile, and veliger toxicity tests
Six concentrations of EarthTec
solution were tested
for the adult, juvenile, and veliger toxicity: 0 (control),
1, 5, 10, 17, and 83 ppm with corresponding Cu
concentrations of 0 (control), 0.06, 0.3, 0.6, 1, and
5 ppm, respectively. Only healthy mussels in the fine
media mesh bags were used for experimentation. The
duration of both the adult and juvenile portions of
the toxicity tests was 7 days (168 h). Four replicates of
the six treatment groups (including controls) were used
for the toxicity tests. In total, for each adult and
juvenile test, 240 mussels of roughly equal size
(*11 mm 723 mm) were used for the toxicity experi-
ments (10 mussels 66 treatment groups 64 repli-
cates ¼240 total mussels). Each replicate was placed
in a 800 mm mesh bag and immersed in a beaker with
raw Lake Mead water and the appropriate dose of
. Each beaker was aerated with an air stone
and kept in a 228C water bath to mimic the epilimnion
water temperature of Lake Mead. Each group was fed
daily with 0.1 ml of Instant Algae
Isochrysis 1800
(Reed Mariculture, Campbell, CA) at a concentration
of 1 610
cells ml
For the veliger toxicity portion of the experiment,
the Ecological Effects Test Guidelines for bivalve acute
toxicity test was followed (US EPA 1996). Unlike the
adult and juvenile tests, this portion of the experiment
did not exceed 48 h (US EPA 1996). Quagga mussel
veligers (n¼10–20) were pipetted into small, glass
Petri dishes and examined under a stereo microscope
22 A. Watters et al.
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(Olympus Stereo Zoom, model SZ4045ESD) to assess
viability. Both dead and living veligers were counted
and documented for each Petri dish.
Adult, juvenile, and veliger mortality
Mortality was checked every 24 h from the beginning
of the experiment for adults, and at 6 h and 12 h
followed by every 24 h for the juveniles. To test for
mortality, gaping mussels were first gently prodded on
their shell valves with forceps; those individual mussels
that did not respond by immediate shell closure were
stimulated in the area of their siphons. Mussels that still
did not respond to siphon stimulation, had their shell
valves forcibly closed with forceps. The mussel was
considered dead if it immediately reopened upon
release of the forceps (Harrington et al. 1997; Morse
2009; Comeau et al. 2011). Dead mussels were removed
from the beaker, their shell length recorded to the
nearest 0.1 mm with digital calipers (Model 62379-531:
VWR International, Inc) followed by placement into a
different mesh bag. They were then transferred to a flow
through system and mortality was confirmed 24 h later.
The experiments for both adult and juvenile mussels
lasted 7 days (168 h). The shell lengths of mussels that
were still alive at 168 h were similarly recorded.
Determination of mortality using cross-polarized
light (CPL) microscopy immediately followed the
addition of EarthTec
to each Petri dish containing
viable veligers. When veligers stopped moving or
internal organs appeared to cease movement under a
microscope for a 2-min observation period, they were
documented as dead (Britton & Dingman 2011). If
100% mortality was not observed within 3 h, the Petri
dish was set aside and examined every 12 h thereafter,
until 36 h was reached. Prior to each treatment, the
control groups were examined to evaluate viability.
The effectiveness of EarthTec
for preventing veliger
The colonization experiment was performed in two
phases on veligers that were collected as described
previously. Both phases lasted 30 days, with six
controls (0 ppm) and six treatments of 1 ppm
(0.06 ppm of Cu
) of EarthTec
in Phase I. Phase
II consisted of four controls, four treatment groups of
2 ppm (0.12 ppm of Cu
), and four treatment groups
of 3 ppm (0.18 ppm of Cu
). Fiberglass panels
(79 66861.66 mm) were hung in each tank with
fishing line from the shelf above. Five days before the
experiment, the fiberglass panels soaked in fresh Lake
Mead water to form a biofilm. The panels were used to
measure colonization of veligers. The veligers were fed
twice daily with 0.375 ml of Instant Algae
1800 (Reed Mariculture, Campbell, California)
(1.54 610
cells). Every week, half the water in the
tanks was exchanged and replaced with fresh Lake
Mead water. To prevent the loss of the veligers, the
water being removed was filtered in the cone portion of
the plankton net with 64 mm pore size and the veligers
were placed back into the corresponding tank. Each
tank received a minimum of 25 veligers l
of water.
After veligers were added to an aquarium, the
appropriate amount of Earth Tec
was added to the
medium to attain the appropriate test concentration.
Because EarthTec
is considered a low pH product,
the pH of the water in all tanks was analyzed (YSI
EcoSense pH100), and the average pH in the treatment
tanks was 8.25 (range ¼8.24–8.26).
Panel analysis
After 30 days, the fibreglass panels were removed from
all tanks and were brought back to UNLV’s Environ-
mental and Occupational Health Laboratory. CPL
microscopy was used to assess the colonization status
of attached quagga mussel juveniles. Each mussel was
then photographed with the Zeiss Discovery V8 stereo
microscope (Carl Zeiss, Inc., Peabody, MA). To mea-
sure the amount of colonization, all six surfaces of the
panel were observed. To determine the number of
mussels per m
, the total number of colonized juveniles
was divided by 0.01.
Statistics and data interpretation
Analysis of covariance (ANCOVA) was used to
examine the effectiveness of different doses of Earth-
on killing mussels at different time intervals (Zar
1996). Analysis of variance (ANOVA) was used to
evaluate if there was any significant difference in
minutes to reach 100% veliger mortality among
different treatment groups in the veliger toxicity test.
Student-Newman-Keuls post hoc multiple comparisons
test was conducted to determine if the difference was
significant. For the colonization experiment, t-test and
ANOVA were used to determine if there was
significant difference among treatments in Phase I
and Phase II, respectively. Linear regression was
performed to estimate the concentration of EarthTec
at which a zero colonization rate was reached. The
significance criterion was set at a¼0.05. All statistical
analyses above were performed using SAS
(version 9.2, SAS Institute Inc. Cary, NC).
The concentration of EarthTec
significantly affected
the survival of adult mussels with time as a significant
Biofouling 23
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covariant (p50.0001). Higher concentrations of and
increased exposure times to Earth Tec
resulted in
greater levels of mussel mortality. No mortality
occurred in control groups of adult mussels. The
time to 100% mortality of adult quagga mussels
decreased with increasing EarthTec
(Figure 1A). Similar results were found among juvenile
mussels (Figure 1B): higher concentrations of Earth
and/or increased time of exposure led to higher
levels of mortality (ANCOVA, p50.0001).
In the adult and juvenile toxicity tests, the control
groups and the 1 ppm of EarthTec
groups showed no
or little mortality. In the adult toxicity test, 50% of the
mussels in the 83 ppm group of EarthTec
were dead
by 30 h. By 96 h, 450% of the mussels in the group
with 5 ppm were dead, 450% of the mussels in the
group with 10 ppm were dead, and all the mussels in
the 17 and 83 ppm groups were also dead. By 168 h,
95% of the mussels in the 5 ppm group were dead and
92.5% in the 10 ppm group were also dead (Figure
In the juvenile toxicity test, 98% of the mussels in
the 5 ppm group were dead by 72 h, and 3% were dead
in the 1 ppm group. Mortality was confirmed by 96 h
for all the mussels except the controls and the 1 ppm
group (Figure 1B).
Based on the acute toxicity of EarthTec
adult and juvenile quagga mussels, their 96 h LC
values were estimated to be 3.42 ppm and 1.40 ppm,
Veliger toxicity
Doses of 3, 5, 10, 17, and 83 ppm of EarthTec
effective for killing 100% of the veligerswithin
minutes. Mortality occurred in 510 min for mussels
treated with 83, 17, and 10 ppm. For mussels treated
with 5 ppm and 3 ppm, mortality occurred in 530
and 20 min, respectively (Table 1). The experiment was
completed after 36 h, and all the controls and
individuals in the groups with 1 ppm were still alive.
The time required for 100% mortality to occur varied
significantly between treatments (ANOVA, p50.001;
¼372,022). As anticipated, Student-Newman-
Keuls multiple comparisons showed that the time to
100% mortality was significantly longer when treated
with 3 ppm and 5 ppm than with higher doses such as
10 ppm, 17 ppm, and 83 ppm (Table 1).
Colonization experiment
For data obtained in Phase I of the colonization
experiment, a pooled t-test was performed. The groups
with 1 ppm of EarthTec
had a lower colonization
rate compared to the control group (p50.01) (Figure
2A). In Phase II of the colonization experiment, the
treatments with 3 ppm of EarthTec
had a zero
colonization rate (Figure 2B). The groups treated
with 2 ppm and 3 ppm were less colonized than the
control group (ANOVA, p50.01) (Figure 2B) while
there was no significant difference between 2 ppm and
3 ppm (p40.05).
Assuming the control (0 ppm) treatment had a
100% colonization rate in Phase I, an average 32%
colonization rate was found for 1 ppm. The same
assumption was applied for the Phase II experiment
where the colonization rates for 0 ppm, 2 ppm, and
Table 1. Time for quagga mussel veligers to reach 100%
mortality at different doses of EarthTec
Minutes (Mean +SD) Replicates
0 ppm Mortality was 0 8
1 ppm Mortality was 0 6
3 ppm 27.5 +7.5 4
5 ppm 20.3 +8.1 3
10 ppm 6.0 +2.0 3
17 ppm 6.0 +1.0 3
83 ppm 5.7 +4.5 3
Figure 1. Cumulative mortality of quagga mussel adults
(A) and juveniles (B) at different EarthTec
n¼240, mean +1 SD.
24 A. Watters et al.
Downloaded by [State University College], [Wai Hing Wong] at 20:37 30 November 2012
3 ppm treatments were 100%, 7%, and 0%, respec-
tively. Therefore, EarthTec
with 1 ppm, 2 ppm, and
3 ppm had reduced colonization rates of 68%, 93%,
and 100%, respectively. Because both control treat-
ments had a 100% colonization rate, least square fit
regression was used to determine the relationship
between colonization rate (%) and dose (ppm).
Because of zero values in both dependent variable
(colonization rate) and independent variable (dose), an
exponential curve is not developed. Therefore, the
colonization data were log(y þ1) transformed and
this also addresses the heteroscedasticity of limited
data (Zuur et al. 2007). A linear regression was pro-
duced to elucidate the dose-response relationship
(Figure 3). The following relationship was found:
Log (Colonization Rate% þ1) ¼70.70 6Dose þ
2.00 (R ¼0.98, p50.01). Therefore, to result in zero
colonization, it is estimated that 2.8 ppm (95%
confidence level: 1.0–3.0 ppm) of EarthTec
necessary for winter months (December to February).
The corresponding Cu
concentration is 0.17 ppm
(95% confidence level: 0.06–0.18 ppm).
The first portion of the study showed that EarthTec
was lethal to quagga mussels. Higher concentrations of
and longer exposures were required for
100% mortality in adult mussels compared to juveniles
or veligers. To kill 450% of the mussels by 96 h, at
least 5 ppm of EarthTec
(0.30 ppm Cu
) was
needed. For 100% mortality of adult mussels, 5 ppm
was administered over 168 h. Depending on the
location and the current amount of copper already in
the water source, 5 ppm (0.3 ppm of Cu
) of Earth-
may be too high to use in a facility that treats
drinking water. Therefore, control methods may be
better targeted towards veligers compared to adult or
juvenile mussels.
The results of this study suggest that EarthTec
more effective for killing adult and juvenile quagga
mussels than another algicide/bactericide/cyanobacter-
icide, Cutrine
-Ultra. Cutrine
-Ultra is a chelated
copper formulation that is effective in penetrating thick
cell walled algae and vascular aquatic plants (Applied
Biochemists 2002). When adult zebra mussels (D.
polymorpha) were exposed to 1,214 mgCul
(1.2 ppm Cu) for 48 h, 50% mortality was achieved
(Kennedy et al. 2006). This amount of copper is below
the US EPA’s maximum containment level (MCL) of
1.3 ppm. After continuous exposure for 96 h, it took
almost two times the maximum allowable dosage of
-Ultra to kill most of the adult zebra mussels.
Another study examined the toxic effects of copper
sulfate (CuSO
) on adult zebra mussels, and found
them to be resistant to copper, resulting in a 48 h LC
of 5.3 ppm Cu l
, but the LC
fell to 2.5 ppm Cu l
after continued assessment of survival (Waller et al.
In the juvenile toxicity segment of the present
study, most of the mussels were dead by 48 h when
5 ppm of EarthTec
was used. These results are
similar to those found in the adult toxicity segment.
However, time was reduced by 50%. It took 72 h for
100% mortality for juvenile mussels exposed to 5 ppm
of EarthTec
0.3 ppm). Waller et al. (1993)
found the LC
for juvenile zebra mussels (shell length
Figure 2. Colonization density of quagga mussels treated
with 0 and 1 ppm (A) and 0, 2, and 3 ppm (B) of EarthTec
Mean +1 SD; values shown on top of the bars are means.
Figure 3. Relationship between the percentage colonization
rates and EarthTec
dose in quagga mussel colonization.
Mean +1 SD. Note that the data on y-axis are log (y þ1)
Biofouling 25
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5–8 mm), after continuous exposure for 48 h to
be 42 ppm of CuSO
. This amount exceeds the
MCL set by the US EPA at 1.3 ppm of copper.
was found to be toxic to quagga mussel
veligers, presumably because at this early life-stage
they do not have a thick protective shell and
membrane function is less well developed, therefore
making them more susceptible to copper ions. In the
present study, 2.8 ppm of EarthTec
(0.16 ppm Cu
was found to be effective for killing quagga mussel
veligers in minutes. Based on personal observation,
was effective on all life stages of veligers,
from trochophores to pediveligers. Kennedy et al.
(2006) found the highest 24 h LC
value for the early
life stages (trochophores) of veligers to Cutrine
was 13 mgCul
(0.013 ppm Cu). The study showed
that this chemical is effective for killing the earliest life
stage, trochophores. However, it did not investigate its
toxicity to later, more developed veliger stages.
The second segment of the study examined the
effects of EarthTec
on preventing quagga mussel
veligers from colonizing fiberglass substrata. In Phase I
and Phase II, EarthTec
was effective in preventing
veliger colonization. Phase I of the colonization
experiment showed that a greater density of mussel
colonization occurred in the control groups whereas
there was far less colonization in the 1 ppm group
(p50.01). Mussel colonization was successfully
deterred when veligers were exposed to 1 ppm of
(0.06 Cu
). Phase II of the colonization
study was conducted in January, where water tem-
peratures were lower (range ¼9.68C–13.38C) com-
pared to Phase I where water temperatures were
warmer (range ¼12.38C–13.38C). It was found that
there was very little colonization in the 2 ppm groups
compared to the control groups, while no colonization
occurred in the 3 ppm groups. The data are in
agreement with the previous experiment that showed
3 ppm was lethal to quagga mussel veligers (Table 1).
The 3 ppm experimental value is also very close to the
statistically predicted value of 2.8 ppm (Figure 3).
Therefore, it is recommended that 2.8 ppm of Earth-
can prevent quagga mussel colonization.
Presently, chlorine is the most commonly used
chemical for prevention of veliger mussel colonization.
One study that was conducted in a field laboratory
found that an intermittent 2 h daily treatment with 1
mg l
chlorine reduced mussel settlement by 91%
compared with the controls. Although, chlorine is
effective in preventing quagga mussel veligers from
settling, densities of up to 6000 m
still occurred
compared to the control settlement monitors which
reached 147,100 m
(Bidwell et al. 1999). The same
study also looked at using half the amount of chlorine
(0.5 mg l
) for 4 h day
, and similar reductions in
mussel colonization were found. The 2 to 4 h chlorine
treatments did cause a reduction in settling, but the
breaks in treatment were sufficient for the veligers to
feed and grow (Bidwell et al. 1999). The intermittent
chlorine schedule in this study may work for a short
time; however, it will not prevent 100% of mussels
from fouling.
Recommendations for further study
Chemical management strategies targeting early larval
stages of quagga mussels are more likely to be cost
efficient and less prone to non-target environmental
impact than strategies aimed at controlling adults and
juveniles. The toxicity experiment was conducted from
late November to early February when the veligers are
competent in colonization in Lake Mead (Gerstenber-
ger et al. 2011). Therefore, a lower dose, such as
1 ppm, may still be effective in preventing colonization
in other seasons when veligers were less competent.
Since veliger dynamics in Lake Mead vary by season,
further studies on the impacts of different seasonal
temperature regimes on the effectiveness of Earth Tec
in preventing quagga mussel settlement may be
required to determine the lowest effective dose required
to prevent any mussel settlement or fouling.
may be most effective in the summer
time when water temperatures are higher. Copper
toxicity increases with an increase in temperature and
decreases at lower temperatures. Rao and Khan (2000)
examined the toxicity of CuCl
on zebra mussels (D.
polymorpha) with increasing water temperatures. The
ambient water temperature was set at 158C, and then
tested at 208and 258C. A 48 h LC
of 0.78 ppm CuCl
at 208C decreased to 0.24 ppm CuCl
at 258C. A
similar effect occurred during a 96 h exposure to
. The 208C 96 h LC50 of 0.5 ppm CuCl
declined to 0.11 ppm at 258C. Because summer surface
water temperatures in Lake Mead approach 28–308C,
the concentration of Earth Tec
required to prevent
mussel fouling may be greatly reduced during warm
summer months. Thus, the concentrations of Earth
required to prevent mussel fouling may have to
be reevaluated relative to temperature conditions
during the application period.
More research needs to be done in Lake Mead to
understand better the lethality of EarthTec
to the
various larval development stages so the appropriate
lethal dose to prevent pediveliger settlement can be
determined. Research also needs to examine the lethal
doses to different stages of veligers in different seasons
when environmental factors, such as temperature and
food quantity and quality are a challenge. It has been
documented that quagga mussel veligers are present
year-round in Lake Mead, with the percentage of
26 A. Watters et al.
Downloaded by [State University College], [Wai Hing Wong] at 20:37 30 November 2012
settlement competent veligers peaking at 460% dur-
ing the fall and declining to 55% in February when
surface water temperatures are at their lowest (Ger-
stenberger et al. 2011). The veliger abundance in Lake
Mead was found to be strongly associated with the
water temperature in the metalimnion (Gerstenberger
et al. 2011). Therefore, experiments need to be
designed to examine different chemical doses to
prevent settlement over a wide range of seasonal
temperatures at which settlement occurs. In that case,
chemical control may be implemented in low doses
and/or for a reduced amount of time when the water
temperature is low in winter time. This would reduce
the amount of chemical that is necessary for applica-
tion; hence, reducing cost and the adverse impact on
the surrounding ecosystem. The significantly higher
chemical sensitivity of veligers compared to adult and
juvenile mussels has pertinent implications in the
design and use of the chemical. Application of
chemical controls in the environment is dependent on
a two major factors. Firstly, the chemical needs to be
effective against the target organism (ie quagga
mussels) and secondly it must not have adverse effects
on non-target species in the environment. Further-
more, chemical control plans need to be safe, practical,
easy to implement, and cost effective. Therefore,
because of the elevated toxicity of Earth Tec
quagga mussel larval stages relative to juveniles and
adults and its capacity to prevent mussel settlement at
relatively low application doses, prevention of mussel
settlement and fouling may be the most cost-effective
and environmentally acceptable Earth Tec
tion technology.
Apart from chemical control, there are other
alternative treatment methods in quagga/zebra mussel
control and management, such as physical and
mechanical cleaning, freezing, desiccation, and biolo-
gical control. Among these alternative methods,
thermal control is an optimistic and more environmen-
tally benign method to control mussel fouling that has
been tested and adopted by many water treatment
plants and power industry (Perepelizin & Boltvskoy
2011; Grutters et al. 2012 and references therein), as
well as agencies that decontaminate boats to prevent
the overland dispersal of invasive mussels (Morse 2009;
Comeau et al. 2011).
For the toxicity portion of the study, 5 ppm of
0.3 ppm) killed 100% of quagga
mussel adults by 168 h and juveniles by 72 h, while for
veligers, 3 ppm was effective in 530 min. For the
colonization portion of the study, 1 ppm of EarthTec
0.06 ppm) reduced veliger colonization on
fiberglass panels. However, the present study was
conducted in a laboratory setting, and it cannot be
assumed that the same results would occur if con-
ducted in the field because of uncontrolled conditions.
While chemical control of quagga mussels has been
proven effective in laboratory studies and closed
systems, the recommended higher doses required for
adult and juvenile eradication restricts the use of harsh,
chemical-based strategies in field studies. The best way
to combat this issue with chemical control, is to
determine the most sensitive life stage and tailor
management techniques to that specific life stage, and
in this case, the veliger. This would optimize target
efficacy while minimizing chemical release into the
environment, risk to non-target species, and cost that
would be required.
This study was supported by National Park Service and
Earth Science Laboratories, Inc. This study would not have
been completed without the help and support from the staff
at the Nevada Department of Wildlife’s Fish Hatchery, along
with the many people who reviewed this manuscript.
Constructive comments from three anonymous reviewers
were helpful in improving the quality of a previous version of
this manuscript.
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... EarthTec QZ.-EarthTec QZ, a USEPA-registered, copper-based molluscicide, is also used to control dreissenid mussels. In laboratory studies, EarthTec QZ applied at 1 mg/L reduced the colonization of quagga mussel veligers on fiberglass panels (Watters et al. 2013). Additionally, quagga mussel veligers were more sensitive to the chemical than were juvenile or adult life stages (Watters et al. 2013). ...
... In laboratory studies, EarthTec QZ applied at 1 mg/L reduced the colonization of quagga mussel veligers on fiberglass panels (Watters et al. 2013). Additionally, quagga mussel veligers were more sensitive to the chemical than were juvenile or adult life stages (Watters et al. 2013). Exposure of zebra mussel adults to EarthTec QZ at 1 mg/L for 72 h resulted in 100% mortality (Claudi et al. 2014), and the exposure of juvenile quagga mussels to 5 mg/L for 72 h resulted in 98% mortality (Watters et al. 2013). ...
... Additionally, quagga mussel veligers were more sensitive to the chemical than were juvenile or adult life stages (Watters et al. 2013). Exposure of zebra mussel adults to EarthTec QZ at 1 mg/L for 72 h resulted in 100% mortality (Claudi et al. 2014), and the exposure of juvenile quagga mussels to 5 mg/L for 72 h resulted in 98% mortality (Watters et al. 2013). ...
Full-text available
Chemical controls ranging from natural products to synthesized chemicals are widely used in aquatic pest management activities. Chemicals can be used to lure organisms to traps or can cause direct mortality by altering the physiological function of an organism. Much of what is known about controlling pests with chemicals is from research done on terrestrial pesticides. This paper focuses on how chemicals might be used as aquatic pesticides to control or eradicate aquatic invasive species. Current control tools are described, as are new technologies designed to selectively target the pest to reduce risks to nontarget organisms and the environment.
... According to the product summary, the molecular structure of QZ (copper sulfate pentahydrate combined with a base acid) maintains copper in the cupric ion form (Cu 2+ ), rendering it more biologically available and less likely to precipitate out of the water column (; Hammond and Ferris 2019). Cupric ions bind to negatively charged organic molecules within the cell and prevent normal function of biologic processes (Watters et al. 2013), making Cu 2+ lethal to almost all aquatic life forms. QZ has been used successfully on both quagga Dreissena bugensis and zebra Dreissena polymorpha mussels (Iwanyckyj et al. 2017;Watters et al. 2013;Hammond and Ferris 2019) in both laboratory and lake settings. ...
... Cupric ions bind to negatively charged organic molecules within the cell and prevent normal function of biologic processes (Watters et al. 2013), making Cu 2+ lethal to almost all aquatic life forms. QZ has been used successfully on both quagga Dreissena bugensis and zebra Dreissena polymorpha mussels (Iwanyckyj et al. 2017;Watters et al. 2013;Hammond and Ferris 2019) in both laboratory and lake settings. QZ has also been shown to be toxic to gastropod embryos and has potential as a means to control invasive faucet snails Bithynia tentaculata; (Carmosini et al. 2018). ...
... The dosage of QZ used in this study was much lower than what has been reported as effective for both Dreissenid mussels and other species of snail. However, exposure times in previous studies (4-7 days) were shorter than in this study and non-target fish species were not a concern (Watters et al. 2013;Iwanyckyj et al. 2017;Carmosini et al. 2018). Conversely, effects were observed on non-target fish species in addition to non-target invertebrate species during this study. ...
Full-text available
The New Zealand mud snail (NZMS) Potamopyrgus antipodarum, is an invasive species of freshwater snail that has become established in the United States. Where they establish, NZMSs can achieve very high densities and have negative ecological impacts. The discovery of NZMSs at Page Springs Hatchery (PSH) in 2019 triggered a need for treatment options in a hatchery that would not result in eradication of fish stocks. The effects of a low-dose (30 ppb) treatment of EarthTec ® QZ on NZMSs, Page springsnails Pyrgulopsis morrisoni and pond snails Physella virgata were evaluated for 39 days. Pond snails fell to zero live individuals 15 days before NZMSs, which fell to zero live individuals 36 days into treatment. Page springsnails fell to zero live individuals three days after NZMSs. It appears that EarthTec ® QZ may be an effective treatment for NZMSs under the conditions tested within PSH. Additional testing needs to be performed to evaluate the potential effects on other non-targets under varying environmental conditions.
... Prevention and mitigation of macrofouling by mussels have focused primarily on chemical tools, especially oxidizing chemicals (e.g., chlorine), potassium compounds (permanganate, potassium hydroxide, potassium chloride; Mackie and Claudi 2010;Chakraborti et al. 2014;Davis et al. 2018), copper-based compounds (Claudi et al. 2014;Watters et al. 2013), and the biopesticide Zequanox® (Whitledge et al. 2015;Rackl and Link 2015). These tools are efficacious, but not without ecological and/or economic costs. ...
... However, chlorine can produce toxic byproducts, such as trihalomethane, poses a human safety concern in some forms, and must be neutralized before discharge into the environment (Mackie and Claudi 2010). Potassium and copper-based compounds have been used in both closed systems (Watters et al. 2013;Chakraborti et al. 2014) and open water (Offutt Air Force Base 2009;DFO 2014;Fernald and Watson 2014;Lund et al. 2017;Hammond and Ferris 2019). When used in open water, potassium and copper-based compounds can persist in the environment and may be toxic to other aquatic life at levels used in dreissenid control treatments (Offutt Air Force Base 2009;Fieldseth and Sweet 2016;Densmore et al. 2018). ...
... One potential control option is EarthTec QZ, which uses a proprietary formulation that is claimed to maintain copper in solution and to increase its bioavailability. 28,29 The California Department of Water Resources trialed of a number of copper based products and found that EarthTec QZ provided better control of both Dreissena species within the trial timeframe. 30 The product's formulation is reported to allow stable copper residuals to be achieved, and unlike chlorine, without the formation of chlorinated DBPs. ...
... Previous investigations concerning the efficacy of this copper product for adult mussels focused upon short-term exposures, with a greater focus on copper doses above 300 μg L −1 . 28,30 This has left a data gap regarding doses that would be more economically feasible for a water utility. Prior testing has also been undertaken with water quality and test conditions that are not representative of the Great Lakes Region. ...
Full-text available
Pilot scale experiments were conducted to test the copper-based EarthTec QZ molluscicide for killing adult quagga mussels. The work was done in Lake Ontario water with average water temperatures ranging between 10.4-6.7°C. Trials consisted of eight copper concentrations varying between 30-500 μg/L in triplicate under continuous and cyclical flow regimes. A 1 mg/L total chlorine trial was used to provide a comparative standard. Complete control was achieved in all test groups ranging within 7 to 28 days for the copper trials, while the chlorination group required 41 days. The efficacy of the copper product was not impacted by continuous versus cyclical flow regime. Results from this study indicate that the copper based product is a viable molluscicide option for adult control with possible advantages over chlorine in cyclical flow regimes and at colder water temperatures.
... However, the proprietary EarthTec® QZ formulation extends the period of time that Cu 2+ remains bioavailable in water, thereby prolonging organismal exposures and potential efficacy. Work by Watters et al. (2013) and Lund et al. (2018) demonstrated that EarthTec® QZ can have strong impacts on mollusk pests such quagga and zebra mussels; however, its usefulness against other invasive mollusks, such as B. tentaculata, remains unknown. ...
... Bithynia tentaculata embryo mortality in our experiments reflected trends observed by Watters et al. (2013), who examined the effectiveness of EarthTec® QZ on the survival of invasive quagga mussels. They found that the early developmental stage of these mussels (veliger) was the most susceptible to the compound exhibiting 100% mortality after just minutes of exposure to 0.6 mg/L Cu 2+ . ...
Full-text available
We used a comparative approach to investigate the effects of a copper-based pesticide (EarthTec® QZ) on embryos of an invasive snail (Bithynia tentaculata) and a native snail (Physa gyrina). Embryos were exposed to one of three treatments: control (0 mg/L Cu2+), low-dose (0.1 mg/L Cu2+), or high-dose (0.6 mg/L Cu2+), which reflect manufacturer-recommended low and medium 4-day molluscicide treatment concentrations. Exposure to 0.6 mg/L Cu2+ over 4 days generated 100% mortality in both invasive and native snail embryos; however, reducing the exposure time from 4 to 1 day resulted in 100% mortality in B. tentaculata but some hatching (7%) in P. gyrina. In contrast, embryos of both species exposed to 0.1 mg/L Cu2+ treatment for 4 days showed almost 100% survivorship. Further manipulations of Cu2+ concentrations and exposure times may yield regimes that maximize mortality in B. tentaculata while minimizing negative impacts on native species.
... EarthTec® QZ is a copper (Cu) molluscicide that delivers the active metal ingredient (Cu 2+ ) with proprietary components that reduce its complexation with aquatic ligands, thereby lengthening the time the metal remains bioavailable. Past work has shown that EarthTec QZ can reduce the establishment of nuisance mussel larvae and the survival of adult mussels under semi-natural conditions (Watters et al. 2013). Field applications have also shown promise for controlling mussels in partial-and whole-lake applications (Hammond and Ferris 2019;Lund et al. 2017). ...
Full-text available
The faucet snail, Bithynia tentaculata, is an invasive snail that facilitates outbreaks of waterfowl disease in the Upper Mississippi River of the United States. In response, there is interest in identifying strategies that mitigate its population and spread. In this study we assessed the effects of a copper (Cu) molluscicide, EarthTec® QZ, at three concentrations (0, 0.1 and 0.6 mg/L Cu) on adult B. tentaculata and a coexisting native species, Physa gyrina. We found that in the 0.6 mg/L Cu treatment, ~ 68% of B. tentaculata snails remained alive after a 4-day exposure whereas all P. gyrina snails died. In contrast, a majority of both snail species remained alive and active after 4 days in the control and 0.1 mg/L Cu treatments. Although B. tentaculata demonstrated higher survivorship, it bioaccumulated more Cu than P. gyrina. Additionally, examination of B. tentaculata individuals revealed that females tended to exhibit higher mortality than males.
... These results could have implications for management because removal could be beneficial or counter-productive depending on density thresholds and conditions. The cost of controlling zebra mussel populations is generally high (Adams and Lee, 2012) and while different eradication methods have been tested in the laboratory (Costa et al., 2011;Watters et al., 2013;Claudi et al., 2014;Luoma et al., 2015) these are not always successful in the field ( Table 1). The development of more efficient eradication methods should benefit from insights into natural factors regulating population growth (Lund et al., 2018). ...
Full-text available
The control of the highly invasive zebra mussel (Dreissena polymorpha) has been flagged as a priority but success has been variable. A better understanding of the growth and drivers of settlement of zebra mussel is necessary for a more efficient management of this invasive species, but seasonal data are still relatively scant. We monitored the seasonal changes in settlement rates, density, and growth of zebra mussel in artificial substrates over 1 year in Cardiff Bay (United Kingdom), an artificial amenity lake invaded by zebra mussels in 2004, where the species is rapidly expanding. Mean settlement rates varied from 4,200 to 6,200 mussel m–2 over June to September mirroring changes in water temperature, and peaked at 17,960 mussels m–2, the highest density reported in Britain. Density was highest at the deepest panels (3 m). Growth varied significantly among sampling stations, taking place during the summer and ceasing during winter and spring. Mixture analysis reveals the existence of multiple cohorts displaying different growth and settlement rates that follow different density dependent mechanisms, being positive density-dependent at low densities, and negative density-dependent at high densities. We suggest this creates the conditions necessary for source and sink metapopulations to develop which may need to be considered in management. Targeting mussels for removal in deep waters during the summer and early autumn might prove beneficial, but the existence of contrasting density-dependent mechanisms suggests that removal may be beneficial or counterproductive depending on local conditions.
... The United States Environmental Protection Agency (U.S. EPA) has registered two pesticides for use as open-water zebra mussel toxicants: EarthTec QZ, a copper-based product; and Zequanox, a killed-cell bacteria-based product. EarthTec QZ has demonstrated toxicity to both zebra and quagga mussels (D. bugensis Andrusov, 1897); however, limited information is available regarding the influence of water temperature on toxicity (Watters et al. 2013;Claudi et al. 2014). Research by Rao and Khan (2000) indicates temperature influences the toxicity of copper to zebra mussels. ...
Full-text available
Zebra mussels (Dreissena polymorpha) have continued their spread within inland lakes and rivers in North America despite diligent containment and decontamination efforts by natural resource agencies and other stakeholders. Identification of newly infested waterways by early detection surveillance programs allows for rapid response zebra mussel eradication treatments in some situations. Previous eradication treatments have occurred over a broad range of water temperatures which have influenced the efficacy of molluscicides. Natural resource managers will benefit from knowledge regarding the impacts of water temperature and exposure duration on the toxicity of molluscicides to zebra mussels. In particular, temperature specific data are needed to inform the selection of an effective molluscicide and the proper dose that will induce 100% zebra mussel mortality. We evaluated the influences of temperature and exposure duration on the toxicity of two U.S. EPA-registered (EarthTec QZ and Zequanox) and two nonregistered (niclosamide and potassium chloride) molluscicides to zebra mussels at water temperatures of 7, 12, 17, and 22 °C. Our results indicate that treatment options for the eradication of zebra mussels in waters ≤ 12 °C include 336 h or longer treatments with EarthTec QZ and KCl as well as treatments with niclosamide ≥ 24 h in duration. In waters ≥ 17 °C, multiple toxicant and exposure duration combinations are potentially effective for zebra mussel eradication. On-site or in situ zebra mussel bioassays are a useful tool for the evaluation of treatment efficacy.
We tested concentration-dependence of selected gene transcripts (cat, gst, hsp70, hsp90, mt and sod) for evaluation as biomarkers of chemical stress. Contrary to the common approach of factorial designs and few exposure concentrations, we used regression across a high-resolution concentration series. Specifically, freshwater mussels (Anodonta anatina) were acutely (96 h) exposed to Cu (13 nominal concentrations, measuring 0.13 – 1 600 µg/L), and transcripts were measured by RT-qPCR. In digestive glands, cat, hsp90 and mt decreased with water Cu (p<0.05), but response magnitudes saturated at < 2-fold decreases. In gills, gst, hsp70, hsp90 and mt increased with water Cu (p<0.05). While hsp70, hsp90 and mt exceeded 2-fold increases within the exposure range, high Cu concentrations were required (38 - 160 µg/L). Although gill responses were generally more robust compared to digestive glands, overall small response magnitudes and moderate sensitivity may set limit for potential application as general biomarkers of chemical stress.
Prechlorination is the most common strategy for zebra and quagga mussel control in drinking water treatment plant intakes in the Great Lakes region. Although effective and inexpensive, chlorine can form regulated disinfection byproducts. Two potential alternatives to prechlorination were evaluated for mussel control: peracetic acid (PAA) and EarthTec QZ, a copper-based product. Pilot-scale experiments were conducted to test EarthTec QZ for veliger control and to evaluate the efficiency of PAA and EarthTec QZ for adult mussel control. EarthTec QZ doses of 30, 60, and 120 μg/L as copper ions demonstrated dose-dependent veliger control at 12 C. PAA doses of 5, 10, and 25 mg/L were effective for adult mussel control at the low water temperatures tested (4 C). Results from this study indicate that PAA and EarthTec QZ may be an alternative to prechlorination.
Full-text available
Ongoing economic globalization has resulted in accelerated rates of introductions of invasive alien species (IAS) in Europe and worldwide with deleterious consequences to biological diversity (Genovesi and Shine 2004; DAISIE 2009). The serious challenges posed by mass human-mediated introductions of invasive alien species induced the strengthening of inter-national cooperation in research, information exchange and management of invasive species during the last two decades, specifically targeting biological invasions in aquatic ecosystems (see Panov et al. 2002, Panov and Gollasch 2004, Gollasch 2007 for reviews). The International Society of Limnology (
Full-text available
Wildland firefighting equipment moves large volumes of raw water during fire incidents in order to extinguish flames or control fire growth. This water movement may serve as pathways for aquatic invasive organisms to be moved between water bodies and watersheds. The equipment used may become contaminated and serve as vectors for future invasions across large geographic areas. New guidelines used by federal firefighting agencies recommend the application of sanitation solutions using quaternary ammonium compounds for decontaminating wildland fire equipment to prevent the spread of aquatic invasive species that may foul the equipment. While quaternary ammonium compounds have been tested on other aquatic organisms, the effectiveness of such compounds has not been systematically tested on dreissenid mussels. We tested the survival of quagga mussel veligers after exposure to a 3% solution of Sparquat 256® for 5 and 10 minutes. We assessed survival immediately after treatment and then after 60 minutes in fresh water. We found that a 5 minute exposure duration was insufficient to kill 100% of tested veligers. However a 10 minute exposure, as prescribed in the interagency operational guidelines for preventing spread of aquatic invasive species, was effective in killing all tested veligers, but not immediately after treatment. An additional 60 minutes were required after the quaternary ammonium solution was removed before 100% mortality was achieved. This work highlights the need for more rigorous evaluation of the effectiveness of various sanitation solutions in killing quagga and zebra mussels under different ambient temperatures in order to validate and refine the sanitation protocol for firefighting equipment and other applications.
Increase in water temperature from an ambient of 15 degrees C to 20 and 25 degrees C increased the respiration rate in zebra mussels, Dreissena polymorpha, by 50 and 175%, respectively, and increased the toxicity of copper; a 48-hour lethal concentration to kill 50% of the organisms (LC50) of 775 mu g/L at 20 degrees C decreased to 238 mu g/L at 25 degrees C, and a 96-hour LC50 of 487 mu g/L at 20 degrees C reduced to 107 mu g/L at 25 degrees C. The oxygen consumption rate in the presence of 150 mu g/L copper decreased by 16% at 20 degrees C and by 50% at 25 degrees C. Thus, high temperatures may increase the toxicity of copper, and possibly other metals, to zebra mussels. Similar increases in heavy metal toxicity may also accompany global warming, which is expected to raise surface water temperature by 2 to 3 degrees C. Such temperature and heavy metal combinations may also be useful in designing field trials to control this nuisance species.
Introduction.- Data management and software.- Advice for teachers.- Exploration.- Linear regression.- Generalised linear modelling.- Additive and generalised additive modelling.- Introduction to mixed modelling.- Univariate tree models.- Measures of association.- Ordination--first encounter.- Principal component analysis and redundancy analysis.- Correspondence analysis and canonical correspondence analysis.- Introduction to discriminant analysis.- Principal coordinate analysis and non-metric multidimensional scaling.- Time series analysis--Introduction.- Common trends and sudden changes.- Analysis and modelling lattice data.- Spatially continuous data analysis and modelling.- Univariate methods to analyse abundance of decapod larvae.- Analysing presence and absence data for flatfish distribution in the Tagus estuary, Portugual.- Crop pollination by honeybees in an Argentinean pampas system using additive mixed modelling.- Investigating the effects of rice farming on aquatic birds with mixed modelling.- Classification trees and radar detection of birds for North Sea wind farms.- Fish stock identification through neural network analysis of parasite fauna.- Monitoring for change: using generalised least squares, nonmetric multidimensional scaling, and the Mantel test on western Montana grasslands.- Univariate and multivariate analysis applied on a Dutch sandy beach community.- Multivariate analyses of South-American zoobenthic species--spoilt for choice.- Principal component analysis applied to harbour porpoise fatty acid data.- Multivariate analysis of morphometric turtle data--size and shape.- Redundancy analysis and additive modelling applied on savanna tree data.- Canonical correspondence analysis of lowland pasture vegetation in the humid tropics of Mexico.- Estimating common trends in Portuguese fisheries landings.- Common trends in demersal communities on the Newfoundland-Labrador Shelf.- Sea level change and salt marshes in the Wadden Sea: a time series analysis.- Time series analysis of Hawaiian waterbirds.- Spatial modelling of forest community features in the Volzhsko-Kamsky reserve.