GEOG336_Campbell_Final_Draft

Ben Campbell 4/28/16
GEOG 336: ResearchPaperFinal Draft
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Range Dynamics of the Zebra Mussel (Dreissena polymorpha) in North America
The zebra mussel is native to the Caspian and Black seas and started spreading
throughout Europe in the early- to mid-1800s. As early as the mid-1980s, commercial shipping
vessels brought the zebra mussel, also known as Dreissena polymorpha, via bilge water to North
America, where they were able to populate and reproduce in Lake St. Clair, adjacent to Detroit,
Michigan. Since then zebra mussel has made a name for itself as one of the most prominent
invasive species to affect freshwater ecosystems in North America. Today, one can find the
species in most of the major river systems, such as the Mississippi, Ohio, Illinois, Tennessee, and
Hudson rivers. This invasive species has many deleterious side effects, such as blocking
pipelines (estimated cost of $1 billion) (Pimental et al, 2004); changing ecosystems dynamics of
streams and lakes; and driving several aquatic species towards extinction (Mackie, 1995)
(Aldridge et al, 2003).
Research has shown that the zebra mussel has been able to spread its distribution and
invade other bodies of water through a series of vectors, both natural and human mediated.
Range dynamics is defined as the way in which animals expand and contract their niche based on
birth and death rates, as well as dispersal rates through emigration and immigration (Schurr et al.,
2012). In the literature on the subject, there are seven hypotheses on the main drivers and
models of zebra mussel range dynamics. They are: (1) high frequency recreational boat use (2)
long distance relocation of residential boat use; (3) the role of dispersal within water bodies; (4)
environmental conditions (5) substratum limitation and food limitation; (6) the source sink
model; and (7) regulated rivers, dams and impoundments. It is very difficult to parse out the
causes of the range dynamics of zebra mussels relative to each cause. In this review, I hope to

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further clarify both the aforementioned hypotheses and understand the intersections and
interactions of the vectors as a composite forcing.
High frequency recreational boat use
Transient recreational boating is the most prominent overland vector of dispersal of zebra
mussels (Timar and Phaneuf, 2009). Phenomenon such as attachment to boat hulls and
entanglement with vegetation caught on anchors, engines or boat trailers, larvae trapped in bilge
water, and fishing gear are the primary sources of contamination through this vector. Although
zebra mussels are incorporated into the multiple trophic levels of the North American lake
ecosystems, the economic cost and loss of species diversity is believed to be greater than any
benefit to the ecosystem, such as increased water clarity. In order to predict the effect of
recreational boating on inland lakes, the authors utilized an economic and ecological model to
determine where and how zebra mussels would expand. In this case, the authors look purely at
human dispersal rather than the source-sink model that looked at natural vectors for dispersal,
which will be discussed later. Timar and Phaneuf found that in understanding human travel
patterns and behavior they were able to predict zebra mussel dispersal with a high degree of
accuracy.
Long distance relocation of residential boat use
In most literature on zebra mussels, human induced dispersal is largely determined as
being one of the primary causes of invasion of isolated lakes and water bodies. Although the
literature widely recognizes that high frequency, recreational boating was a major cause of
overland dispersal, Johnson et al. states that changing ownership or residencies of long-term
resident boats could provide a more dangerous, yet less frequent, mode of anthropogenic, long-

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distance dispersal. Since zebra mussels are ubiquitous in most eastern river basins, the real worry
is long distance dispersal via resident boats (boats that spend most of their time in one connected
water system) to unaffected water basins (i.e. western North America). He further claims that
gamete dilution, which decreases chances of fertilization, requires the introduced population to
be very large. Therefore, the coming and going of small recreational boats via bilge water is not
likely to result in large amounts of invasion. In fact, the attachment of adult zebra mussels to
macrophytes poses a much larger threat, due to the ability of adults to establish a colony
(Johnson et al., 2001).
Environmental limitations
Historically, the zebra mussel is invasive in Great Britain, but has been present in
controlled numbers in the Thames for one hundred and thirty years. However, there has been a
recent spike in zebra mussel observations in Great Britain. There are four major findings that the
cause of the increased populations and greater range distribution. Firstly, zebra mussel’s growth
and reproduction can be severely limited by low temperatures s and pollutants. In the recent past
hundred years, Great Britain’s has increased water quality, which has allowed for an increased
size of their niche. Secondly, the introduction of a different species of dreissinid mussel, the
quagga mussel (Dreissena bugensis), may have been mistakenly identified as a zebra mussel by
untrained parties. Thirdly, increased travel over the past 30 years could have resulted in
increased accidental dispersals caused by humans. Like the case in North America, the
interconnectivity of canal systems caused the original dispersal of zebra mussels. Most recently,
the transportation of boats from lake to lake could have resulted in increased invasion. Alone,
these phenomena cannot explain fully the rapidity of zebra mussel expansion, as well as the
recent explosion in population. Finally, the authors propose that ecophenotypic variation could

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explain for the recent explosion (Aldridge et al, 2004). Ecophenotypic variation is the
phenomenon where certain ecosystems may have created populations more suited to their
environment. Subsequently, the authors consider that the recent rapid invasions of North
America and Britain may be due to the introduction of mussels with varying degrees of climate
tolerances. In fact, studies have shown that zebra mussels taken from varying ecosystems have
different degrees of tolerance for temperature and salinity (Aldridge et al., 2004). Dressinids
have the greatest potential and productivity of any mollusks that have been introduced to North
America. The abundance of these zebra mussels is related to trophic type, and thrive the most in
meso- and eutrophic environments. However, Stanczykowska (1964) found that trophic level
has little to do with their recent colonization of North America. Dressinids have the most prolific
reproduction, where females produce one million eggs per year with a two to three year lifespan.
Albeit, there is a 99% mortality rate in the settling stage of their larval cycle due to lack of
suitable substrate to attach. In addition, zebra mussels are neither ovoviviparous, where young
are brooded inside the parent, nor oviparous, where the eggs are attached to the substrate. This
severely limits the ability for increased range, as zebra mussels’ reproduction is rather stochastic
and vulnerable to environmental conditions (Mackie, 1995).
Dispersal within interconnected bodies of water
Due to the zebra mussel’s vastly different natural habitat in Eastern Europe, it has
developed several adaptations that give it advantage over other mollusk species native to North
America. Firstly, the shell is perfectly adapted to life on hard substrates, whereas other mollusks
attach themselves to a substrate while also partially submerged in the benthos, or the floor of a
water body, also known as infaunal organisms. Secondly, its ability to attach itself to most
substrates provides an abundance of habitable lake and riverine ecosystems. Thirdly, zebra

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mussel’s sexual reproduction has the male and female reproductive organs in separate
individuals (read: dioecious), has high fecundities, and utilizes external fertilization rather than
internal, which were all unique to its species relative to other mollusks. Fourthly, the larvae life
cycle is four weeks long and the dispersal of the final larval stage of certain mollusks, or
veligers, is suspended in pelagic zone to be dispersed via water currents (Mackie 1995). Finally,
the zebra mussel achieves rapid reproductive maturity, which allows it the ability to establish
populations rapidly given the correct resources. Due to all these factors, the zebra mussel is able
to distribute itself at a rate of 250 km per year -1 and exist at different depths than bivalves due to
their epifaunal adaptation (Mackie 1995).
According to these factors, Johnson and Padilla claim that dispersal within connected
water bodies happens via three main vectors: downstream/overland dispersal, natural or human-
mediated methods, and the potential to disperse multiple life stages (larval and adult). Firstly,
zebra mussels are unable to disperse upstream or in lotic environments. After excretion by adult
mussels, larvae exist in pelagic zones and have no adaptations to exist in lotic environments.
Because of this, upstream and downstream dispersal were likely due to natural drift of larvae and
human mediated activities. Human mediated dispersal is deemed ‘limitless’ by the authors.
Human made canals bridging isolated bodies of water has proven to be extremely effective at
dispersing gametes due to low stream velocity, presence of backwater and lentic environments
(read: Erie Canal). Dispersal within water bodies is much slower because of the difficulty of
transporting mussels, poor survival rates, or the lack of demographic conditions needed for a
self-sustaining population. Demographic conditions include life cycle stage, mortality,
frequency, and the spatial patterns of the founding population. In both cases of dispersal within
bodies of water and between isolated bodies of water, demographics play a critical role in

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determining whether a population is established or not. Due to all the reasons described, there
are often very low odds of establishing a population between two connected lentic environments
if they are far enough away (Johnson & Padilla, 1996).
Food limitation vs. Substratum limitation
It is widely understood by most ecologists dealing with the range dynamics of zebra
mussels that one of the largest limiting factors for the expansion of its range is the abundance of
substrata to attach themselves too. In Strayer et al., the author attempts to understand the
limiting factor of the zebra mussel population in the Hudson River. The authors observe that the
Hudson River zebra mussel populations appear to be exhibiting self-limitation, as adults are
consuming the larvae after a rapid growth and not allowing for rapid recruitment. They found
this to be the case, as the distributions of any predator were low that year. In addition, they
found that control of larval survival was also in part due to competition for food. Strayer does
not indicate that this is a breakthrough discovery, and still accepts the substrata limitation, but he
hypothesizes that food can limit zebra mussel populations if the phytoplankton populations are
stressed or threatened. According to Cecala et al. (2008) and Idrisi et al (2001), when these
phytoplankton populations are reduced, benthic algal primary production increases in response,
which can affect the trophic organization. In addition, he claims that perhaps lacustrine
ecosystems might be limited by food, whereas riverine are limited by substratum. However, this
contradicts the source-sink model’s prediction that phytoplankton populations grow scarcer as
you move away from the source lake (Strayer et al. 1996).
Source-sink model

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In Horvath et al., the authors looked at three forms of dispersal models and compared
their predictions with actual observed zebra mussel data and distribution. Zebra mussel
colonization of downstream lotic ecosystems was entirely predicated on upstream lakes invaded
by them. Those lakes serve as a source of veligers. The purpose of the paper was to reject the
null hypothesis that zebra mussels were unlikely to colonize a stream less than 30 meters wide.
They looked at three types of dispersal models: the large river model, the source-sink model, and
the downstream march model.
According to these methods of dispersal, the large river model predicted that zebra
mussels could not colonize streams less than 30 meters wide. This was supported by evidence
from Strayer’s 1991 article, where stream width was correlated with physical characteristics,
such as current velocity, primary production, and suspended sediment load. In the source sink
model, dispersal was a product of larval development time and stream velocity (Mackie, 1995).
However, Horvath et al. claim that dispersal will likely be shorter because of several
environmental reasons detailed later. Finally, the downstream march model assumes that lakes
are the primary source of zebra mussel larvae, but downstream colonization was expected to be a
sequential colonization ‘ad infinitum’ throughout the entire basin. Horvath et al. found that the
source-sink model best fit the dispersal of zebra mussels. The limited dispersal was caused by
larval mortality associated with turbulence, food limitation, general distance, lotic environments,
lack of large pools or backwater areas, and lack of dams or impoundments. Originally, Strayer
found that stream size affected zebra mussel colonization. However, Horvath et al’s finding
showed that colonized streams in St. Joseph River basin had average widths of 7 to 20 meters,
which contradicts Strayer’s stream width hypothesis.
Regulated rivers, Impoundments and Dams:

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Regulated rivers, or rivers that are controlled by manmade structures, such as dams or
impoundments, pose an opportunity to expand the range of invasive species. By creating an
unnatural lentic environment, it allows for the development of zebra mussel populations. As we
saw in the source-sink model, zebra mussels are best suited for lentic environments, and these
impoundments can allow for demographics and environmental conditions to be ideal for zebra
mussel invasion. In fact, impoundments may provide more shoreline development, an opportune
habitat for zebra mussels. Their planktonic larval stage is an effective dispersal mechanism;
however, it is not a good method of sustaining an adult population in streams because young
cannot maintain their positions upstream. Subsequently, this artificial environment allows for
increased range for zebra mussels, as they are unable to thrive in most fast moving lotic
ecosystems. However, reservoirs provide the environment necessary for these mussels to thrive
(Mackie, 1995).
Conclusion:
The drivers that affect zebra mussel dynamics are not only numerous, but also dependent
on scope, temporality, and environmental conditions. The recent increase in population and
range expansion of the zebra mussel in North America is a complex issue. The majority of the
literature attributes anthropogenic vectors, such as recreational boating, to be the cause of this
invasive species crisis. However, much of the discourse disagrees on several aspects, including
the anthropogenic magnitude of dispersal and models that predict range expansion, to name just
a few contentions. What this analysis shows is that the range dynamics of the zebra mussel are
highly dependent on not just human activity, but also trophic organization, resource limitations,
and zebra mussel reproduction.

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Citations:
1. Aldridge, D. C., Elliott, P., & Moggridge, G. D. (2004). The recent and rapid spread of
the zebra mussel (Dreissena polymorpha) in Great Britain. Biological
Conservation, 119(2), 253- 261. Retrieved March 27, 2016.
2. Cecala, R. K., Mayer, C. M., Schulz, K. L., & Mills, E. L. (2008). Increased Benthic
Algal Primary Production in Response to the Invasive Zebra Mussel (Dreissena
polymorpha) in a Productive Ecosystem, Oneida Lake, New York. Journal of
Integrative Plant Biology, 50(11), 1452-1466. Retrieved February 15, 2016, from
http://onlinelibrary.wiley.com/doi/10.1111/j.1744-7909.2008.00755.x/full
3. Horvath, T. G., Lamberti, G. A., Lodge, D. M., & Perry, W. L. (1996). Zebra Mussel
Dispersal in Lake-Stream Systems: Source-Sink Dynamics? Journal of the North
American Benthological Society, 15(4), 564-575. Retrieved March 27, 2016.
4. Idrisi, N., Mills, E. L., Rudstam, L. G., & Stewart, D. J. (2001). Impact of zebra mussels (
Dreissena polymorpha ) on the pelagic lower trophic levels of Oneida Lake, New
York. Can. J. Fish. Aquat. Sci. Canadian Journal of Fisheries and Aquatic
Sciences, 58(7), 1430-1441. Retrieved March 28, 2016.
5. Johnson, L. E., & Padilla, D. K. (1996). Geographic spread of exotic species: Ecological
lessons and opportunities from the invasion of the zebra mussel Dreissena
polymorpha. Biological Conservation, 78(1-2), 23-33. Retrieved March 28, 2016.
6. Johnson, L. E., Ricciardi, A., & Carlton, J. T. (2001). Overland Dispersal of Aquatic
Invasive Species: A Risk Assessment of Transient Recreational Boating.
Ecological Applications, 11(6), 1789-1799. Retrieved February 15, 2016, from
http://onlinelibrary.wiley.com/doi/10.1890/1051-
0761(2001)011[1789:ODOAIS]2.0.CO;2/abstract
7. Mackie, G. L. (1991). Biology of the exotic zebra mussel, Dreissena polymorpha, in
relation to native bivalves and its potential impact in Lake St. Clair.
Environmental Assessment and Habitat Evaluation of the Upper Great Lakes
Connecting Channels, 219, 251-268. Retrieved March 28, 2016.
8. Mackie, G. L. (1995). Adaptations of North American exotic mollusca for life in
regulated rivers and their potential impacts. The Center for Field Biology, 39-78.
Retrieved March 28, 2016.
9. Schurr, F. M., Pagel, J., Cabral, J. S., Groeneveld, J., Bykova, O., O’Hara, R. B., . . .
Zimmermann, N. E. (2012). How to understand species’ niches and range
dynamics: A demographic research agenda for biogeography. Journal of
Biogeography J. Biogeogr., 39(12), 2146-2162. Retrieved March 28, 2016, from
http://www.wsl.ch/staff/niklaus.zimmermann/papers/JBiogeogr_Schurr_2012.pdf
10. Strayer, D. L., Powell, J., Ambrose, P., Smith, L. C., Pace, M. L., & Fischer, D. T.
(1996). Arrival, spread, and early dynamics of a zebra mussel ( Dreissena
polymorpha ) population in the Hudson River estuary. Can. J. Fish. Aquat. Sci.
Canadian Journal of Fisheries and Aquatic Sciences, 53(5), 1143-1149. Retrieved
March 28, 2016.
11. Strayer, D. 1991. Projected distribution of the zebra mussel, Dreissena polymorpha, in
North America. Canadian Journal of Fisheries and Aquatic Sciences 48: 1389-
1395.

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12. Stanczykowska, A. 1964. On the relationship between abundance, agggregations and
"condition" of Dreissena polymorpha. (Pall.) in 36 Masrian lakes. Ekol. Pol.
24:103-112
13. Timar, L., & Phaneuf, D. J. (2009). Modeling the human-induced spread of an aquatic
invasive: The case of the zebra mussel. Ecological Economics, 68(12), 3060-
3071. doi:http://dx.doi.org/10.1016/j.ecolecon.2009.07.011

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