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Economic Impacts of Zebra Mussels on Drinking Water Treatment and Electric Power Generation Facilities



Invasions of nonnative species such as zebra mussels can have both ecological and economic consequences. The economic impacts of zebra mussels have not been examined in detail since the mid-1990s. The purpose of this study was to quantify the annual and cumulative economic impact of zebra mussels on surface water-dependent drinking water treatment and electric power generation facilities (where previous research indicated the greatest impacts). The study time frame was from the first full year after discovery in North America (Lake St. Clair, 1989) to the present (2004); the study area was throughout the mussels' North American range. A mail survey resulted in a response rate of 31% for electric power companies and 41% for drinking water treatment plants. Telephone interviews with a sample of nonrespondents assessed nonresponse bias; only one difference was found and adjusted for. Over one-third (37%) of surveyed facilities reported finding zebra mussels in the facility and almost half (45%) have initiated preventive measures to prevent zebra mussels from entering the facility operations. Almost all surveyed facilities (91%) with zebra mussels have used control or mitigation alternatives to remove or control zebra mussels. We estimated that 36% of surveyed facilities experienced an economic impact. Expanding the sample to the population of the study area, we estimated 267 million dollars (BCa 95% CI = 161 million dollars - 467 million dollars) in total economic costs for electric generation and water treatment facilities through late 2004, since 1989. Annual costs were greater (44,000 dollars/facility) during the early years of zebra mussel infestation than in recent years (30,000 dollars). As a result of this and other factors, early predictions of the ultimate costs of the zebra mussel invasion may have been excessive.
Economic Impacts of Zebra Mussels on Drinking Water
Treatment and Electric Power Generation Facilities
Nancy A. Connelly Æ Charles R. O’Neill Jr. Æ
Barbara A. Knuth Æ Tommy L. Brown
Received: 16 August 2006 / Accepted: 23 February 2007
Springer Science+Business Media, LLC 2007
Abstract Invasions of nonnative species such as zebra
mussels can have both ecological and economic conse-
quences. The economic impacts of zebra mussels have not
been examined in detail since the mid-1990s. The purpose
of this study was to quantify the annual and cumulative
economic impact of zebra mussels on surface water-
dependent drinking water treatment and electric power
generation facilities (where previous research indicated the
greatest impacts). The study time frame was from the first
full year after discovery in North America (Lake St. Clair,
1989) to the present (2004); the study area was throughout
the mussels’ North American range. A mail survey resulted
in a response rate of 31% for electric power companies and
41% for drinking water treatment plants. Telephone inter-
views with a sample of nonrespondents assessed nonre-
sponse bias; only one difference was found and adjusted for.
Over one-third (37%) of surveyed facilities reported finding
zebra mussels in the facility and almost half (45%) have
initiated preventive measures to prevent zebra mussels from
entering the facility operations. Almost all surveyed facil-
ities (91%) with zebra mussels have used control or miti-
gation alternatives to remove or control zebra mussels. We
estimated that 36% of surveyed facilities experienced an
economic impact. Expanding the sample to the population
of the study area, we estimated $267 million (BCa 95% CI =
$161 million–$467 million) in total economic costs for
electric generation and water treatment facilities through
late 2004, since 1989. Annual costs were greater ($44,000/
facility) during the early years of zebra mussel infestation
than in recent years ($30,000). As a result of this and other
factors, early predictions of the ultimate costs of the zebra
mussel invasion may have been excessive.
Keywords Aquatic nuisance species Economic impacts
Invasive species Zebra mussels
Invasions of nonnative species are one of the leading
mechanisms of global environmental change, especially in
freshwater ecosystems (Garcia-Berthou and others 2005).
Human-mediated introductions are among the most impor-
tant impacts affecting ecosystems (Mack and others 2000).
Damage can be both ecological and economic, with zebra
mussels and quagga mussels (Dreissena polymorpha and
Dreissena bugensis) serving as excellent examples (for the
purposes of this paper, the two species of dreissenids are
hereafter referred to generically as ‘‘zebra mussels’’). While
ecological impacts are being debated elsewhere (e.g., Rai-
kow 2004, Strayer and others 2004, Winkler and others
2005), economi c impacts of zebra mussels have not been
examined in detail since the mid-1990s, although predictions
have ranged as high as $1 billion per year (Pimentel 2005).
Zebra mussels were first observed in North America in
June 1988 (O’Neill and MacNeill 1989). The zebra mussel
can now be found in 23 states (AL, AR, CT, IL, IN, IO, KS,
N. A. Connelly B. A. Knuth T. L. Brown
Human Dimensions Research Unit, Department of Natural
Resources, Cornell University, Ithaca, NY 14853, USA
C. R. O’Neill, Jr.
Cornell University, New York Sea Grant Extension,
Morgan Hall, State University College,
Brockport, NY 14420, USA
N. A. Connelly (&)
126 Fernow Hall, Cornell University, Ithaca, NY 14853, USA
Environ Manage (2007) 40:105–112
DOI 10.1007/s00267-006-0296-5
VT, WI, WV) and two Canadian provinces (Ontario [ON],
Quebec). All five of the Great Lakes are infested, as well as
Lakes St. Clair and Champlain and inland lakes in Michigan,
Missouri, New York, Ohio, Oklahoma, Pennsylvania, Ver-
mont, Wisconsin, and Ontario. The Allegheny, Arkansas,
Cumberland, Detroit, Genesee, Hudson, Illinois, Niagara,
Mississippi, Missouri, Mohawk, Monongahela, Ohio,
Oswego, Rideau (ON), St. Clair, St. Lawrence, Susquehan-
na, Tennessee, Vertigris (OK), and Wabash rivers are also
home to zebra mussel populations. It is likely that they will
continue to spread into additional rivers and inland lakes
(Ram and McMahon 1996) that are currently uninfested but
within the range of the invasion. GARP (genetic algorithm
for rule-set production) analysis of the current distribution of
zebra mussels in North America based on 11 important
environmental and geological variables indicates that much
of New England that is currently uninfested, as well as some
areas of the Southeast and the West Coast, may be at con-
siderable risk; however, much of the American West will
likely be uninhabitable for zebra mussels (Drake and Bos-
senbroek 2004).
Zebra mussels have affected surface water-dependent
electric power generation and drinking water treatment
facilities since their arrival in North America by fouling
intake pipes and other equipment, resulting in severely
impeded flows of water into these facilities (MacIsaac
1996). Such infestations, once discovered, must be reme-
diated and measures taken to prevent future fouling. This
can involve construction of new intakes, physical removal
of mussel accumulations, and/or chemical treatments of
affected intake components. Preventive actions are possible
as well; these generally include physical barriers, chemical
treatments, and educational programs for recreational
boaters to prevent introduction of mussels to new waters.
The economic impact of zebra mussels was studied most
comprehensively in 1995 by two groups of researchers. A
study conducted by Ohio Sea Grant estimated zebra mussel
impacts in the Great Lakes Basin at $120 million for 1989
to 1994 (Park and Hushak 1999). That study was limited to
municipal water plants, electric generation facilities, and
other industries using surface water from the Great Lakes
or its tributaries. A more comprehensive study, undertaken
by New York Sea Grant for the National Zebra Mussel
Information Clearinghouse (now the National Aquatic
Nuisance Species Clearinghouse) , covering the entire
North American range of the mussels at that time (Great
Lakes plus other water bodies), estimated zebra mussel-
related expenditures in excess of $69 million for the period
1989 to 1995 (O’Neill 1997). The latter study included
additional water uses beyond drinking water and electric
generation, such as navigation locks, and institutional uses
such as at universities, golf courses, and fish hatcheries.
These uses, although affected negatively by zebra mussels,
did not suffer economical ly to the extent experienced by
municipal/industrial water users (O’Neill 1997). Both of
these stud ies relied on small sample sizes, thus explaining
the difference in estimates between the two. Ex trapolations
to overall population estimates should be considered ten-
tative at best. No comprehensive study of the economic
impact of zebra mussels in terms of control and prevention
costs and lost production costs has been conducted since
1995. The New York Sea Grant coauthor, however,
extrapolated forward the 1995 results, positing a cumula-
tive impact from 1989 through 2005 of approximately $1
billion (taking into account additional infested waters,
additional impacted facilities, and additional years of
treatment expenses) (unpublished data).
The purpose of this study was to quantify the annual and
cumulative economic impact of zebra mussels, from the first
full year after their introduction (1989) to the present (2004)
throughout the mussels’ North Amer ican range, on surface
water-dependent drinking water treatment and electric
power generation facilities (as these were the facilities most
impacted previously). (The study does not estimate other
economic impacts of the invasion, such as on fisheries and
recreational boating.) Research questions addressed in-
cluded comparisons with the previous New York Sea Grant
study to examine how closely current estimates match past
estimates and predictions. With the expansion of the zebra
mussels range, have costs expanded proportionally? Also,
are there differences in the impacts on drinking water treat-
ment and electric power generation facilities? Are there
differences in costs as facility size increases? Given the
importance of this species for water resources management
throughout the central United States, an updated, compre-
hensive economic assessment of zebra mussel impacts was
needed to inform decision mak ing.
We used a mail questionnaire to gather information on the
costs of implementing zebra mussel control or prevention
measures as well as estimates of the economic value of lost
production. We sought information for the period beginning
in 1989, the first full year of possible infestation, to the fall of
2004, when the survey was implemented. We also obtained
information on the history of infestation and the types of
prevention and control measures used. We designed the
questionnaire so that results would be comparable with those
of the 1995 New York Sea Grant survey (O’Neill 1997).
We surveyed all identifiable electric generation and
drinking water treatment companies which might use surface
water in U.S. states and Canadian provinces within the range
where zebra mussels were known to be present. We devel-
oped a list of 708 electric generation companies from Platts
106 Environ Manage (2007) 40:105–112
2003 UDI Directory of Electric Power Producers and Dis-
tributors (Giles and Brown 2003) and a list of 876 drinking
water treatment providers from EPA listings and contacts at
health departments in states where zebra mussels exist.
Identifying raw water intake from surface water was
important because zebra mussels might be present in surface
water sources and not groundwater. We generated a listing of
water treatment facilities with surface water sources from the
EPA records, but water source information was not known in
advance for electric generation facilities.
We sent the mail questionnaire to all identified compa-
nies (1584) in the fall of 2004. We used the standard three
follow-up reminder process advocated by Dillman (2000)
to encourage response. We were aware that electric com-
panies in particular might be reluctant to provide economic
data, so we emphasized confidentiality in our correspon-
dence. We conducted nonrespondent telephone interviews
with 50 electric and 50 water companies to assess differ-
ences between respondents and nonresponde nts.
Because companies could be responsi ble for more than
one facility, we asked mail survey respondents to photocopy
the questionnaire and respond for each facility for which they
were responsible. In the nonrespondent telephone survey, we
asked interviewees how many facilities they were respon-
sible for but asked them to provide answers for the one
facility they knew best. From this information we estimated
the number of facilities in the study area.
We entered data on the computer and analyzed it using
SPSS. Chi-square and t-tests were used to test for statistical
differences between respondents and nonrespondents and
between drinking water and electric generation facilities.
To calculate a 95% confidence interval for the estimate of
economic costs, the bootstrap bias-corrected accelerated
(BCa) interval using 5000 resamples in S-PLUS was used
because the distribution was not normal (Hesterberg and
others 2006).
We conducted site visits at five facilities of different
types to allow for a more in-depth examination of pre-
vention and control methods used. During the site visit the
questionnaire filled out previously by the facility manager
was discussed in more detail to determine how he or she
developed estimates of costs. This information was used to
help interpret the findings from the mail survey.
Response Rates and Population Size
Of the 708 electric generation companies contacted, 61
questionnaires were undeliverable and 81 responded, for an
adjusted response rate of 13%. Of the 876 drinking water
treatment companies contacted, 70 questionn aires were
undeliverable and 321 responded, for an adjusted response
rate of 40%. However, during the survey process (mail and
telephone follow-up), we found that many companies,
particularly those providing electric power generation, did
not obtain their raw water from surface water but used
wells and groundwater instead (Table 1). From the mail
survey process we found that 34% of electric generation
companies that contacted us either by responding to the
questionnaire or via e-mail were using groundwater. These
companies were not part of the intended population for the
study and, therefore, were removed from our estimates of
population size and response rate. We als o assumed that
mail survey nonrespondents we contacted via telephone
were representative of all nonrespondents, and we removed
nonrespondents according to the percentage not using
surface water (66% for electric, 2% for water). The result is
an estimated population of 259 electric and 787 drinking
water companies that use surface water. The effective re-
sponse rate, therefore, based on surface water users, was
31% for electric and 41% for drinking water.
Assuming that we began with a complete list of all
electric and drinking water companies in the study area, we
estimated that the population of companies that used sur-
face water was 1046 and they were responsible for 1297
facilities. Our data were collected on a facility basis (n =
447 facilities), so we report data by facility and multiply by
2.9 to expand our estimates to population estimates
reflecting the total costs borne by all companies and all
Nonresponse Bias
Nonrespondents contacted by phone (n = 100) did not
differ from respondents (n = 447) on most variables com-
pared. Nonrespondents were just as likely as respondents to
have zebra mussels in their facility. The year when zebra
mussels arrived at the specific facility did not differ be-
tween respondents and nonrespondents. The mussels were
equally likely to have caused problems in the facility for
respondents and nonrespondents. Nonrespondents were just
as likely as respondents to have engaged in prevention and
control of zebra mussels. Based on past research in which
nonrespondents were found to be less interested in the topic
being studied (Connelly and Knuth 2002), we expected
nonrespondents would be less likely to have zebra mussels
in their facility, but this was not the case.
The only variable for which we could detect a difference
between respondents and nonrespondents was the per-
centage experiencing an economic impact due to zebra
mussels. Almost half (46%) of the respondents spent
money or had an economic loss, compared to one-third
(31%) of nonrespondents. Estimates of economic impact
discussed later are adjusted for this bias. The sample size
Environ Manage (2007) 40:105–112 107
for nonrespondents reporting an economic impact was too
small (n = 9) for comparison of average impacts experi-
enced by nonrespondents in 2003 or 2004 vs. impacts
experienced by respondents.
Facility Characteristics
Most responding facilities (76%) primarily provided public
drinking water. These were sufficient in number to permit
data analysis by facility size (as measured by million gal-
lons per day of drinking water produced). A similar number
of facilities (37% and 38%, respectively) produced £ 1
million or 2 million–10 million gallons per day; the
remaining 25% produced 11 million gallons per day.
Fifteen percent of facilities surveyed provided electric
generation, with just over half (58%) being publicly owned
as opposed to privately or investor-owned. Most of these
facilities generated ener gy using fossil fuels (63%), fol-
lowed by hydroelectric (32%) and nuclear (5%). The
remaining facilities (9%) were some combination of
drinking water, electric generation, and industrial facilities.
We received responses from facilities in 19 states and 2
Canadian provinces, thus covering almost the entire range
of zebra mussels in North America. The top 10 water
bodies used as a raw water source by respondents were (in
descending order) Lake Michigan, Lake Erie, St. Lawrence
River, Ohio River, Lake Superior, Lake Ontario, Tennessee
River, Lake Champlain, Mississippi River, and Lake Hur-
Zebra Mussel Prevention and Control Activities
Over one-third of responding facilities reported finding
zebra mussels in their facility (Table 2). Most discoveries
occurred between 1989 and 1998, but some occurred in
every year from 1989 to 2004. Most respondents thought
the zebra mussels had been in the facility 6 months to 1
year before discovery. Only one-fifth of responding facil-
ities had preventive measures in place prior to their dis-
covery. About half are currently monitoring for zebra
mussels. Over two-fifths have a plan in place for prevention
and/or control. No significant differences were found be-
tween drinking water and electric power generation facil-
ities for any of these com parisons.
Almost half of responding facilities have initiated pre-
ventive measures to prevent zebra mussels from entering
the facility operations (Table 2). This was more oft en the
case for drinking water facilities than for electric power
generation facilities. The most commonly used preventive
measures included sand filt ration, restricting access to the
water source, and oxidizing chemicals such as sodium
hypochlorite, chlorine gas, and potassium permanganate.
The vast majority of surveyed facilities with zebra
mussels have used control or mitigation alternatives to
remove or control zebra mussels (Table 2). Proportionately
fewer electric power generation facilities had used such
alternatives, but their sample size was too small to support
statistical comparisons. The most commonly used control
measures included mechanical removal by divers and the
use of oxidizing chemicals such as sodium hypochlorite,
chlorine gas, and potassium permanganate. The chemicals
were viewed as the most effective control measures.
Economic Impact of Zebra Mussels
About half (46%) of the responding facilities had some
expenditures between 1989 and 2004 for controlling/pre-
venting zebra mussels or had suffered lost production and
revenues due to zebra mussels. The percentage reporting
expenditures was lower for electric power generation
facilities (32%) than for drinking water facilities (49%) (v
= 5.5, df = 1, p = 0.02). Adjusting for nonresponse bias in
the percentage of facilities reporting a loss, we estimate
that 36% of surveyed facilities (or a total of 468) experi-
enced an economic impact. Each of these facilities indi-
cated total mean expenditures or costs of $500,000 between
1989 and the time they completed the questionnaire in
October or November 2004. (These numbers were not
Table 1 Estimating the
population of electric generation
and drinking water treatment
companies using surface water
as their raw water source
Electric generation
Drinking water
treatment companies
Initial population 708 876
Undeliverable questionnaires 61 70
Responded ‘‘Not using surface water’’ 42 10
Responded to mail questionnaire 81 321
Nonrespondents to mail questionnaire 524 475
% ‘‘not using surface water’’
(based on nonrespondent phone interviews)
66% 2%
Nonrespondents using surface water 178 466
Estimated population using surface water 259 787
108 Environ Manage (2007) 40:105–112
adjusted for inflation, because of our desire to compare
them with the results of other studies.) Expanding the
sample to the population of the study area, we estimated
$267 million in total economic costs for electric generation
and water treatment facilities through late 2004. Using
bootstrap methods, we estimated the BCa 95% confidence
interval to be $161 million to $467 million. Costs were
greater during the early years of zebra mussel infestation
than in recent years (Table 3).
Analysis of expenditures by category (e.g., prevention,
retrofit, chemical treatment) shows that most costs were
associated with prevention efforts (Table 4). Lost produc-
tion and revenues contributed significantly to the overall
estimate of impacts. Expenditures for facil ities producing
electricity appeared to be greater than for those providing
drinking water treatment, but the sample size for electric-
only facilities was too small to support statistical compar-
As facility size increased, so did costs related to zebra
mussels (Table 5). Affected facilities that produce £ 10
million gallons of drinking water per day spent on average
$100,000 to $150,000 between 1989 and 2004, compared
with $500,000 for affected facilities that produced >10
million gallons per day. The average expenditures for
prevention, planning, and filtration were particularly high
for larger facilities compared with those producing £ 10
million gallons.
Future Concerns
In response to an open-ended question about emerging is-
sues for their facility, over one-third (37%) indicated at
least one issue, most common ly algal blooms (32%) and
taste and odor concerns (30%). Other topics mentioned by
more than 10% of these respondents were toxic bacteria,
disinfectant by-pro ducts, and possible new species or
threats of which they were not yet aware.
This study attempted to identify all surface water-depen-
dent drinking water treatment and electric generation
facilities within the current range of zebra mussels in
North America. Using state/provincial lists, we included
some facilities outside the zebra mussels’ current range ,
choosing to err on the side of being inclusive rather than
exclusive in our list of facilities. Thus, not all of the
facilities surveyed had zebra mussels. However, many of
these facilities anticipate problem s in the future and are
monitoring or taking preventive actions. Approximately
one-third of all facilities had spent money on prevention
or control measures.
The methodology used in this study gives us confidence
in our estimate of the number of facilities affected. How-
ever, a caution about the lower response rate for electric
power generation facilities is in order. With the advent of
deregulation, many electric power generation facilities
experienced a large turnover in staff and an increased
concern for confidentiality of financial information.
Although we went to greater lengths than usual in our
survey implementation to assure respondents of the confi-
Table 2 Zebra mussel occurrence, prevention, and control in responding facilities.
Characteristic Overall Electric generation
Drinking water
treatment facilities
Facilities with zebra mussels 37% 41% 37%
Monitoring for zebra mussels 47% 47% 49%
Plan in place for prevention and/or control 44% 39% 46%
Preventive measures in place
45% 50% 20%
Of those with zebra mussels
Preventive measures in place prior to discovery 22% 37% 19%
Control measures in place
91% 76% 94%
Statistically significant difference between electric generation facilities and drinking water treatment facilities, v
= 19.9, df = 1, p < 0.01
The sample size for electric generation facilities was too small for statistical comparisons with drinking water treatment facilities
Table 3 Mean and total economic impacts caused by zebra mussels
by year
Year of expenditure Mean per facility with
some type of expenditures
Estimated total
for study area
1989–1995 $312,424 ($52,070/yr) $146,214,432
1996–2000 $144,984 ($28,996/yr) $67,852,512
2001 $26,493 $12,398,724
2002 $29,106 $13,621,608
2003 $33,673 $15,758,964
2004 to
date (Oct.–Nov.)
$24,328 $11,385,504
Total $571,009 $267,232,212
Environ Manage (2007) 40:105–112 109
dentiality of their responses, it is likely that our lower
response rates for these facilities can be attributed to this
change in management culture. Thus, ou r findings (par-
ticularly economic impacts) regarding electric power gen-
eration facilities are more limited than for water treatment
Based on our estimate of the total number of facilities
affected, we estimated a cumulative economic impact to
drinking water treatment and electric generation facilities
in North America of $267 million between 1989 and 2004.
The 95% confidence interval ($161 million to $467 mil-
lion) was large primarily because of the wide range of
estimates of economic costs. This $267 million estimate
does not account for all costs related to the zebra mussel
invasion because it does not include costs associated with
other infrastructure impacts on industry and navigation,
natural resources impacts such as those to fisheries, or
economic impacts related to recreational boating and
The average costs per facility have remained steady in
recent years at approximately $30,000 per year. This differs
from costs in the early years, which were roughly $44,000
per facility per year. Since none of the estimates have been
adjusted for inflation, the disparity between early years and
more recent times is even greater. It is probable that more
money was spent in earlier years cleaning out facilities that
were infested and developing control procedures than in
more recent years, in part because staff at many facilities
have learned from earlier experiences at other facilities what
to do and how to be more proactive. From discussions with
Table 4 Mean and total
economic impacts caused by
zebra mussels, 1989–2004 by
expenditure category
Expenditure category Mean per facility with some
type of expenditures
Estimated total
for study area
Prevention efforts $186,557 $87,308,676
Lost production and revenues $124,110 $58,083,480
Chemical treatment $63,049 $29,506,932
Planning, design, and engineering $58,459 $27,358,812
Retrofit and/or reconstruction $48,314 $22,610,952
Filtration or other mechanical exclusion $22,061 $10,324,548
Monitoring and inspection $21,398 $10,014,264
Mechanical removal $13,897 $6,503,796
Nonchemical treatment $9,786 $4,579,848
Research and development $4,208 $1,969,344
Personnel training $2,976 $1,392,768
Customer education $1,831 $856,908
Other $14,360 $6,720,480
Table 5 Mean economic
impacts caused by zebra
mussels, 1989–2004 by
expenditure category, for
drinking water treatment
facilities with different
Note. MGD, million gallons per
Expenditure category Mean per facility with some type of expenditures
£ 1 MGD 2–10 MGD 11 MGD
Prevention efforts $17,078 $59,144 $152,468
Lost production and revenues $0 $1,453 $0
Chemical treatment $26,618 $21,981 $64,736
Planning, design, and engineering $17,429 $13,140 $85,934
Retrofit and/or reconstruction $20,989 $30,283 $53,916
Filtration or other mechanical exclusion $2,893 $2,906 $47,352
Monitoring and inspection $17,615 $11,387 $27,388
Mechanical removal $2,956 $4,567 $19,179
Nonchemical treatment $211 $0 $0
Research and development $11 $0 $8,173
Personnel training $911 $1,780 $3,036
Customer education $3,571 $94 $3,443
Other $0 $0 $39,836
110 Environ Manage (2007) 40:105–112
electric generation facility managers outside the context of
this study, we learned that after the initial early years of trial
and error control implementation, managers found that
continuous chemical treatment was not needed to control
zebra mus sels, only periodic treatment. This would decrease
the costs for those facilities. However, continuous chemical
treatment still would be used in drinkin g water treatment
facilities because the chemicals served other purposes be-
sides zebra mussel control .
We found no difference in the rate of infestation of
electric power generation versus drinking water treatment
facilities but did find that drinking water treatment facilities
were more likely to be implementing preventive measures
and spending some money on control. Perhaps this is an-
other case of electric power generation facilities being
reluctant to report financial information. However, among
facilities reporting spending money, it appears that electric
power generation facilities were spending more per facility
than drinking water treatment plants (but we could not
substantiate this statistically due to small sample sizes for
electric power generation facilities).
We also found that as facility size increases, so do costs.
We demonstrated this by comparing drinking water treat-
ment plants that produced more versus less than 10 million
gallons per day. Larger plants’ costs were three to five
times greater than those of smaller facilities.
Comparisons of data from the current study for the time
period 1989–1995 with data collected from the same time
period by O’Neill (1997) show the current estimates ($146
million) to be much larger than previous estimates ($69
million). The difference is similar when comparing mean
expenditures per facility for drinking water treatment
plants (Table 6). (Comparisons could not be made for
electric power generation facilities due to insufficient
sample sizes.) Even though current survey respondents on
average are associated with smaller facilities than 1995
survey respondents, the average cost per facility during the
1989–1995 time period was greater for current survey
respondents. Some differences in the opposite direction
appear by expenditure category; expenditures for 1995
survey respondents were greater than for 2004 survey
respondents (Table 6). The differences in these numbers
may be explained by the more complete listing of facilities
obtained for the current study compared with the lists
available in 1995.
Early predictions of the ultimate costs of the zebra
mussel invasion may have been overblown (e.g., Roberts
[1990] estimated $4 billion over 10 years in the Great
Lakes, including impacts to sportfishing). Using data from
the 1995 Sea Grant study (O’Neill 1997), our Sea Grant
coauthor predicted impacts of approximately $1 billion,
well in excess of the $267 million estimate from this study
(and its associated confidence interval of $161 million–
$467 million). Several reasons may explain this difference.
First, as suggested earlier and borne out by our data,
facilities infested in the early years had to spend more
money cleaning out their facilities and developing control
procedures than facilities that were infested later. Second,
facility staff may have learned what to do from the earlier
infested facilities and are being more proactive now and
therefore spending less than originally anticipated. For
example, an unanticipated cost savings cam e in the change
from continuous to periodic chemical treatments for elec-
tric generation facilities. Third, zebr a mussels did not ex-
pand into new waters, particularly smaller inland lakes, as
rapidly as anticipated.
Table 6 Comparison of mean
economic impacts caused by
zebra mussels in 1989–1995
overall and by expenditure
category for drinking water
treatment facility respondents
who responded to the 1995
survey vs. 2004 respondents
Note. IS, insufficient sample;
MGD, million gallons per day.
Source: O’Neill (unpublished
Expenditure category Mean per facility with expenditures in that category
2004 survey respondents 1995 survey respondents
Total $261,311 $214,356
Prevention efforts $248,306 IS
Lost production and revenues IS IS
Chemical treatment $39,476 $194,421
Planning, design, and engineering $76,883 $113,263
Retrofit and/or reconstruction $93,776 $182,445
Filtration or other mechanical exclusion IS IS
Monitoring and inspection $12,922 $11,435
Mechanical removal IS IS
Nonchemical treatment IS IS
Research and development IS IS
Personnel training IS $4,257
Customer education IS IS
Other IS IS
Avg. production capacity (MGD) 36.8 56.8
Environ Manage (2007) 40:105–112 111
The discrepancy between the predictions of costs and
the current estimates also may be explained by information
gathered in the site visits. Interviewees noted how difficult
it was to separate costs associated with zebra mussels from
other costs as they completed the questionnaire. For
example, chlorine is used to kill zebra mussels at many
intake pipes. However, chlorine is used normally as a
disinfectant even without concerns about zebr a mussels,
perhaps not at the mouth of the intake but at some point in
the treatment process. Interviewees indicated that they did
their best when completing the questionnaire, but the dif-
ficulties reported in distinguishing specific costs attribut-
able to zebra mussels suggests uncertainty about the
magnitude of ongoing maintenance costs that should be
attributed to zebra mussels vs. other operational require-
The focus of research efforts on costs and control may
now naturally shift to new invasive species . Clearly more
are on the way (Mack and others 2000; Roberts 1990).
Facility operators expressed concern about them, how they
would control them, and what the costs will be. This
analysis suggests that costs will most likely be highest in
the beginning years of dealing with a new invader, then
level off over time, and perhaps be incorporated as part of
the ongoing maintenance budget for normal operations.
Acknowledgments Development of this publication was supported
by the National Sea Grant College Program of the U.S. Department of
Commerce’s National Oceanic and Atmospheric Administration un-
der award NA16RG1645-020122 to the Research Foundation of the
State University of New York for New York Sea Grant. The views
expressed herein do not necessarily reflect the views of any of those
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112 Environ Manage (2007) 40:105–112
... To a large extent, this scarcity is due to the fact that data are sparse, and assessments of the economic impacts are complex and often very imprecise (Hui and Richardson 2017;Hanley and Roberts 2019). However, many of those attempted suffer from several flaws, and some of the most ambitious exercises in this area (Perrings et al. 2001;Pimentel et al. 2005;Pimentel 2011) have been heavily criticized for their inconsistencies, misapplication of economic methods, poorly substantiated figures, and unfounded assumptions and extrapolations (Reaser et al. 2003;Connelly et al. 2007;Davis 2009;Thompson 2014;Guiaşu 2016;Jernelöv 2017). Further, some of the highest figures are explained to a large extent by the inclusion of human diseases, in particular influenza (Thompson 2014;Guiaşu 2016). ...
... For example, glyphosate-based herbicides are by far the most intensively used for weed control worldwide, especially in agriculture (Wagner et al. 2017), where they eliminate both alien and native plants that compete with the crop species (Sesin et al. 2021). In drinking water treatment and power plants chlorine is used both as a disinfectant and to control biofouling, such as invasive mussels, even in the absence of the NIS (Connelly et al. 2007). ...
The economic costs of non-indigenous species (NIS) are a key factor for the allocation of efforts and resources to eradicate or control baneful invasions. Their assessments are challenging, but most suffer from major flaws. Among the most important are the following: (1) the inclusion of actual damage costs together with various ancillary expenditures which may or may not be indicative of the real economic damage due to NIS; (2) the inclusion of the costs of unnecessary or counterproductive control initiatives; (3) the inclusion of controversial NIS-related costs whose economic impacts are questionable; (4) the assessment of negative impacts only, ignoring the positive ones that most NIS have on the economy, either directly or through their ecosystem services. Such estimates necessarily arrive at negative and often highly inflated values, do not reflect the net damage and economic losses due to NIS, and can significantly misguide management and resource allocation decisions. We recommend an approach based on holistic costs and benefits that are assessed using likely scenarios and their counter-factual.
... Moreover, the quagga mussel can colonize hard and soft substrates in deep waters, down to 200 m (Nalepa et al. 2014), causing economically-impactful biofouling of water pipes and other infrastructure (Connelly et al. 2007). After the rst observation in the Rhine River, the quagga mussel was discovered in Lake Geneva in 2015 and in Lake Constance in 2016 (Haltiner et al. 2022). ...
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The dreissenid quagga mussel, Dreissena rostriformis bugensis , is an invasive species native to the Black Sea region that has recently spread to Western Europe. This organism has recently colonized Swiss northern perialpine lakes, causing major changes to aquatic ecosystems and impacts on human activities. Due to its competitiveness, the quagga mussel takes advantage of human mediated transport to reach new environments. Therefore, the management of quagga mussel should seek to prevent further spread and minimize its negative impact. With this aim, the early detection by environmental DNA (eDNA) methods is increasingly applied in freshwater systems. Here, an approach based on species-specific primer targeting the quagga mussel from eDNA was applied to Lake Lugano and Lake Maggiore, two large perialpine lakes at risk of invasion due international tourism. Our results are the first to show that the quagga mussel has spread south of the Alps and suggest that in both the lakes the colonization is in the early stages. Additionally, they indicate that the eDNA approach is a powerful tool for the early detection of quagga mussel invasions, and may be applied to reduce the resulting ecological and economic impacts.
... Dreissenid musselszebra mussel (Dreissena polymorpha) and quagga mussel (Dreissena rostriformis bugensis)are notorious invasive, epifaunal bivalves in many European and North American freshwater ecosystems, including the Laurentian Great Lakes (Strayer, 2009;Higgins and Vander Zanden, 2010). These mussels have caused enormous economic losses due to severe fouling of infrastructure (Connelly et al., 2007;Strayer, 2009). They have also reengineered invaded ecosystems through numerous effects, such as increased water transparency due to filtration of suspended matter (MacIsaac, 1996;Hecky et al., 2004;Strayer, 2009;Higgins and Vander Zanden, 2010;Burlakova et al., 2021;Li et al., 2021). ...
FULL TEXT: ABSTRACT: Invasive dreissenid mussels have reengineered many freshwater ecosystems in North America and Europe. However, few studies have directly linked their filter feeding activity with ecological effects except in laboratory tests or small-scale field enclosures. We investigated in situ grazing on lake seston by dreissenid mussels (mainly quagga mussel Dreissena rostriformis bugensis) using a ‘control volume’ approach in the nearshore of eastern Lake Erie in 2016. Flow conditions were measured using an acoustic Doppler current profiler, surrounded by three vertical sampling stations that were arranged in a triangular configuration to collect time-integrated water samples from five different depths. Seston variables, including chlorophyll a, phaeopigment, particulate organic carbon and nitrogen, and particulate phosphorus, along with stoichiometric ratios and water flow over mussel colonies, were considered when estimating grazing rates. We observed suboptimal flow velocity for mussel grazing, i.e., 0.028 m s⁻¹ at 0.1 m above bottom (mab), and resuspension was deemed minimal. Water temperature (mean: 25.1 °C) and an unstratified water column were optimal for grazing. Concentration of seston was low (mean: 0.2 mg L⁻¹ particulate organic carbon) and decreased from surface to lakebed where noticeable depletion was observed. Grazing rates calculated at discrete depths varied substantially among trials, with maximum rates occurring at 0.25 or 0.5 mab. Positive grazing rates were restricted to 0.5 mab and below, defining an effective grazing zone (0.1–0.5 mab) in which the flow velocity, seston concentration, and water depth were consistently and positively correlated with grazing rates of different lake seston variables. Horizontal changes in stoichiometric ratios of seston were strongly associated with grazing rates, revealing higher uptake of particulate phosphorus than nitrogen and carbon. Our study supports the nearshore phosphorus shunt hypothesis, which posits that dreissenid mussels retain phosphorus on the lake bottom and contribute to a wide range of ecological effects on freshwater ecosystems.
... Individuals at the invasion fronts have larger bodies and greater body condition than those in already established areas due to weaker intraspecific competition and greater food availability at the invasion fronts . Although invasion impacts to aquatic ecosystems may be apparent after short time periods (Janssen and Jude 2001; Lauer et al. 2004;Britton et al. 2007;Connelly et al. 2007), it is necessary to assess impacts at longer post-invasion intervals to ultimately understand both how the invader will influence the ecosystem and how impacts are related to the invasion stage (Downing et al. 2013;Pelicice et al. 2014;Havel et al. 2015). Fish community diversity metrics and abundances of Round Goby and Percidae species will have been influenced by habitat conditions, which are integral in shaping fish communities within streams (Moyle and Light 1996). ...
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Numerous fish species in the Laurentian Great Lakes have been negatively impacted by the establishment of the invasive Round Goby ( Neogobius melanostomus ). However, limited understanding exists as to how Round Goby has impacted small-bodied native benthic fishes after its secondary invasion into tributaries of the Laurentian Great Lakes. To investigate Round Goby impacts on darter species (family Percidae) in tributary ecosystems, catch per unit area (CPUA) of native and non-native fishes from two riverine ecosystems in Southwestern Ontario (Ausable River, Big Otter Creek) were analyzed. Spatial analyses indicated Round Goby CPUA was highest proximate to the Great Lakes, with a sharp decline in CPUA at sites upstream from each lake (Round Goby CPUA approached zero after 18 and 14 km in the Ausable River and Big Otter Creek, respectively). There was some evidence of a negative relationship between the CPUA of Round Goby and several darter species along the tributary gradients, with moderately negative co-occurrence between Round Goby and Rainbow Darter in the Ausable River and Johnny Darter and Percidae species overall in Big Otter Creek. However, overwhelming evidence of negative associations between Round Goby and all darter species was not found. The negative relationship between the CPUA of Round Goby and some darter species was observed over similar time periods since establishment but greater spatial scales than in previous studies, and therefore has important implications for understanding the ecological impacts of Round Goby in tributary ecosystems.
... Dreissenids in shallow area are predated heavily by waterbirds which contributes to an increase in numbers of overwintering waterbirds and nutrient flows from waterbirds' feeding areas to resting areas (Werner et al. 2005). Furthermore, dreissenid mussels are also a source of major economic impact due to biofouling of water pipes and other infrastructure (Marsden and Lansky 2000;Connelly et al. 2007), damage to recreational and commercial boats, and overall negative effects on fisheries (Oreska and Aldridge 2011;Rudstam et al. 2016). ...
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The dreissenids, quagga mussel Dreissena bugensis and zebra mussel D. polymorpha, are invasive freshwater mussels in Europe and North America. These species strongly impact aquatic ecosystems, such as the food web through their high abundance and filtration rate. They spread quickly within and between waterbodies, and have the ability to colonize various substrates and depths. The zebra mussel invaded and established in Swiss lakes in the 1960s, whereas the quagga mussel was not detected until 2014. We collected all available data from cantonal as well as local authorities and other institutions to describe the colonization pattern of quagga mussels in perialpine lakes north of the Alps. We also collected data regarding the distribution of larval stages of the mussels, the so-called veliger larvae. We observed that in lakes colonized by the quagga mussel, veligers are present the whole year round, whereas they are absent in winter in lakes with only zebra mussels. Additionally, we present detailed information about the invasion and colonization pattern of quagga mussels in Lake Constance. Quagga mussels colonized the lakeshore within a few years (~ 2016-2018), outcompeted zebra mussels, and have reached densities > 5000 ind. m-2 in the littoral zone, even at 80 m densities above 1000 ind. m-2 were found at some locations. At the end of the article, we discussed possibilities on how the spread of quagga mussels within and among northern perialpine lakes should be monitored and prevented in the future.
... Indeed, many non-native species have become targets for fisheries, [18][19][20] and several Mediterranean fisheries have become dependent on the economic returns from the fishing of these species [18,21,22]. Many studies highlight the negative effects caused by the expansion of non-native invasive species, such as pest introduction [23,24], economic damage [25,26], and health risks [27][28][29]. Simultaneously, although rarely documented, non-native species can also contribute to the local economy by becoming a new resource, e.g., food [30]. ...
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Climate change affects the shift range distribution of species, especially among mobile species, and this phenomenon can alter ecosystems and impacts human activities. Fishing is an anthropic activity that undergoes the effect not only of the introduction and increase of non-native species but also of native thermophilic ones. Some of these species can become a commercially exploitable resource. However, this information is often obscured by the negative effects these species can cause to the environment. We investigated how the thermophilic species Caranx rhonchus, neglected in Italy, could become a relevant resource. We studied the nutritional profile and the presence of heavy metal contamination and compared these traits with those of a similar common Mediterranean species, namely Trachurus trachurus. The proximate composition was determined following the AOAC procedure, while the fatty acid profile was determined by GC/MS, and the mineral component was obtained by mass spectrometer (ICP-MS). Caranx rhonchus is a nutritionally good species, although it is little consumed and exploited. Increasing the market supply with new commercially exploitable emerging species would benefit local communities and the environment. Therefore, it is necessary to investigate how a shift of the range caused by climate change can provide benefits within the human dimension.
... Other invasive species have been costly to the region; sea lamprey, a species that began to take hold in the Great Lakes in the 1940s and 1950s, is blamed for the collapse of native populations of lake trout (Salvelinus namaycush) and lake whitefish (Coregonus clupeaformis) and costs the region approximately $20 million annually to control (Great Lakes Commission and St. Lawrence Cities Initiative, 2012; Koonce et al., 1996). Dreissena mussels have changed nutrient dynamics, decreased lake pelagic productivity and are known for clogging intakes for power plants and drinking water treatment plants (Connelly et al., 2007); are estimated to annually cost the region $300-$500 million in damages and control (Great Lakes Commission and St. Lawrence Cities Initiative, 2012). The economic damages of Asian carp have not been studied with the same level of detail, but proposals have been made to re-structure the Chicago Area Waterway System (CAWS) at costs ranging from $7 billion to $18 billion in 2014 dollars; in 2010 a chain-link fence was installed at a cost of $200,000 to prevent passage of carp between the Wabash and Maumee Rivers during flood events (Hebert, 2010;U.S. Army Corps of Engineers, 2014). ...
Feedbacks between the ecosystem and the economy are important to consider when measuring impacts from a disturbance but are often omitted from general equilibrium bioeconomic models. These models usually focus on how humans respond to ecological change, but do not consider that in adapting to changed conditions, humans can further affect the ecosystem. We present a framework that couples a regional computable general equilibrium model with an Ecopath with Ecosim food web model with bidirectional feedbacks between the two systems. Our bioeconomic model uniquely represents a comprehensive mapping of the entire regional economy, including recreational and commercial fishing, harvest quotas, and fish biomass in the economic system. We simulate the bioeconomic impacts of a potential Asian carp invasion of Lake Erie's food web and regional economy with and without bidirectional feedbacks between the economy and the ecosystem. When feedbacks are omitted there are large ecological variations in the projected biomass levels of many target species, with differences in biomass of up to 80 percentage points. Results demonstrate the need to reflect bidirectional feedbacks between the economy and the ecosystem; omission of these feedbacks in this case may appear to be economically trivial yet have large ecological consequences.
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An overview of the knowledge of the invasive feshwater golden mussel (Limnoperna fortunei) is presented, with particular emphasis on the voids of our current understanding of its ecology and its effects on the systems invaded. L. fortunei started spreading northwards in China after 1960, and ~ 1990 it invaded Japan and South America. These invasions fostered a strong increase in the interest in the mussel. However, coverage of its biology, ecology, and impacts has been very uneven. Geographic distribution and spread, seasonal dynamics and methods for controlling its fouling in industrial plants and other human-made facilities have received most of the attention, while many other important issues (e.g., multiannual density changes, competition with native organisms, predation by invertebrates, reptiles, birds, and mammals) lag far behind. The effects of the golden mussel on environmental traits and resident organisms have been investigated almost exclusively in laboratory or mesocosm settings, but extrapolation of these results to waterbody scales is contentious, mainly because system-wide densities are largely unknown. The information available suggests that most environmental impacts of L. fortunei are mixed, context- and stakeholder-dependent, with both positive and negative effects. In contrast, its impacts on human-made facilities and infrastructure are clearly always negative and costly.
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The ecosystem services approach to conservation is becoming central to environmental policy decision making. While many negative biological invasion-driven impacts on ecosystem structure and functioning have been identified, much less was done to evaluate their ecosystem services. In this paper, we focus on the often-overlooked ecosystem services provided by three notable exotic ecosystem engineering bivalves, the zebra mussel, the quagga mussel, and the golden mussel. One of the most significant benefits of invasive bivalves is water filtration, which results in water purification and changes rates of nutrient cycling, thus mitigating the effects of eutrophication. Mussels are widely used as sentinel organisms for the assessment and biomonitoring of contaminants and pathogens and are consumed by many fishes and birds. Benefits of invasive bivalves are particularly relevant in human-modified ecosystems. We summarize the multiple ecosystem services provided by invasive bivalves and recommend including the economically quantifiable services in the assessments of their economic impacts. We also highlight important ecosystem disservices by exotic bivalves, identify data limitations, and future research directions. This assessment should not be interpreted as a rejection of the fact that invasive mussels have negative impacts, but as an attempt to provide additional information for scientists, managers, and policymakers.
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Food web interactions between native larval bluegill (Lepomis macrochirus), exotic invasive zebra mussels (Dreissena polymorpha), and zooplankton were examined with a mesocosm experiment. Hatchling larval bluegill collected from nests were reared in the presence of size-structured populations of zebra mussels in 1500-L limnocorrals suspended in an artificial pond for 2 weeks. Chlorophyll a, other limnological variables, and zooplankton abundance and biomass (including copepod nauplii and rotifers) were monitored over time. During their first 2 weeks of life, larval fish reared in the presence of mussels grew 24% more slowly than fish reared alone. Differential growth rates can be explained by competition between mussels and bluegill for food in the form of microzooplankton. Also likely was an indirect competition via starvation of the zooplankton community as zebra mussels consumed phytoplankton. Either direct or indirect trophic competition between zebra mussels and obligate planktivores may result in ecological harm as zebra mussels spread throughout inland lakes of North America.
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Despite predictions that the zebra mussel (Dreissena polymorpha) invasion of North America would damage fisheries, analyses of actual effects on fish have been few and equivocal. We analyze 26 years of data on fish populations in the Hudson River to quantify changes associated with the zebra mussel invasion. Based on our measurements of changes in the lower food web, we predicted that populations of open-water fish species (e.g., Alosa spp.) would suffer and populations of littoral fish species (e.g., Centrarchidae) would prosper from the zebra mussel invasion. We found that the median decrease in abundance of open-water species was 28%, whereas the median increase in abundance of littoral species was 97%. Populations of open-water species shifted downriver away from the zebra mussel population, whereas those of littoral species shifted upriver. Median apparent growth rates fell by 17% among open-water species and rose by 12% in the single littoral species studied. Many of the observed changes were large and involved species of commercial or recreational importance (e.g., American shad (Alosa sapidissima), black basses (Micropterus spp.)). The influence of zebra mussels on fish should vary widely across ecosystems as a function of system morphology, factors that limit primary production, and diets of the fish species.
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Large numbers of the filter-feeding larval stage of zebra mussels (Dreissena polymorpha) (veligers) have been advected into the estuarine transition zone (ETZ) of the St. Lawrence River. In 1994, they became the dominant member of the tidal freshwater zooplankton assemblage of the ETZ (and subsequently the true estuarine assemblage) during summer months. These changes in community structure have not, however, been reflected in changes in the abundance of preinvasion taxa. Abundance of potential planktonic competitors such as rotifers and the cladoceran Bosmina longirostris fluctuated between years but did not decline following the invasion. Only densities of the copepod Eurytemora affinis declined in 2000 and 2001, but this could not be definitively associated with the invasion. Synchronous variation among different zooplankton groups suggests that environmental forcing related to or correlated with temperature anomalies is the major cause of interannual variation in the abundance of zooplankton taxa. The negative correlation between veliger abundance and salinity indicates that the ETZ acts as a sink for the larval stages of the zebra mussel. Their precise fate remains uncertain, but our study suggests that this invasion has had little or no impact on this pelagic community in spite of the numerical dominance of veligers. © 2005 NRC Canada.
This report is the first product of the Status and Trends Program in the National Biological Service. It is the first of a series of reports on the status and trends of the nation's plants, animals, and ecosystems. The report compiles information on many species and the ecosystems on which they depend. It provides information about causes for the decline of some species and habitats. It also gives insight into successful management strategies that have resulted in recovery of others. The report represents an effort to bridge the gap between scientists and resource managers, policy makers, and the general public.
The range expansion of zebra mussels (Dreissena polymorpha) in North America has been rapid and costly in both economic and ecological terms. Joint social, political, and scientific ventures such as the 100th Meridian Initiative aim to reduce the spread of zebra mussels by eliminating the unintended transport of the species and preventing its westward expansion. Here we forecast the potential distribution of zebra mussels in the United States by applying a machine-learning algorithm for nonparametric prediction of species distributions (genetic algorithm for rule-set production, or GARP) to data about the current distribution of zebra mussels in the United States and 11 environmental and geological covariates. Our results suggest that much of the American West will be uninhabitable for zebra mussels. Nonetheless, some catchments along the West Coast and in the southeastern United States exhibit considerable risk of invasion and should be monitored carefully. Possible propagule dispersal to these places should be managed proactively.
We compared the views of community leaders in the Hudson River Valley, New York State, to identify different perspectives on ecosystem restoration of the Hudson River estuary. We found three distinct types of community leaders. All thought ecosystem restoration was important, but they varied on which specific actions were more important to implement. We used the coorientation model to examine the degree of agreement, accuracy, and congruency between community leaders' views and local residents' views. Community leaders were not in complete "agreement" with residents, but two of the three community leader groups had some views in common with them. In general, community leaders could not predict accurately the views of local residents. Community leaders consistently underestimated the importance residents placed on actions related to protection of the environment. They overestimated the importance of economic development to residents. Congruency was low between community leaders' views and their perception of residents' views.