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Invasive Species: Zebra Mussels

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by

Muneeza Sheikh

on 4 November 2014

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Transcript of Invasive Species: Zebra Mussels

What are Zebra Mussels?
Migration
Zebra Mussels are native to the Caspian sea bordering Iran, Turkmenistan, Kazakhstan, Azerbaijan and Russia
Habitat
Equilibrium Damage
Food Chain
Sighting a Zebra Mussel
Invasive Species: Zebra Mussels
Let's keep it simple...
They're small freshwater
mussels...
About the size of your fingernail!
And...
They're DANGEROUSLY INVASIVE!
But how did they end up in Canada?
They were most likely cycled from the "ballast water cycle" through a European transoceanic ship due to trade between Europe and the Caspian regions during the 17th and 18th centuries.
The Ballast water cycle
What is the path of its habitat from one ecosystem to another?
By the 1990's, they could be found in all of the Great Lakes. Soon, they had spread to some inland lakes and rivers like the St. Lawrence river and Lake Simcoe and other bodies of water in the states through the Great Lakes and the Mississippi watersheds.
There are a few factors that allow Zebra Mussels to dominate and spread from ecosystem to ecosystem:
Prolific reproduction
Similar ecosystems
The Reproductive Cycle
When Zebra Mussels are veligers (free-swimming larvae) they flow with the ocean current. This is another way they can spread; by drifting great distances with the current. At about 3-4 weeks, they develop shells which weigh enough to make them sink. In order to survive, they must attach onto a substrate using their byssal threads (tuft of fibers), which include sediments, rocks, pipes, parts of boats, other organisms and even each other! At a year, they reach sexual maturity and are able to reproduce.
Female Zebra Mussels can lay from 30,000 to 40,000 eggs each reproductive cycle, and up to one million eggs per year!
Zebra Mussels are able to dominate ecosystems by rapidly populating in very large numbers in a short amount of time. They are also able to reproduce a year after they are born. Their new habitats lack the same biotic and abiotic limiting factors that their native habitats had to keep their populations in check.
Similar Ecosystems
Since Zebra Mussels are freshwater species, they are able to thrive in other freshwater ecosystems including rivers, streams, lakes, ponds, wetlands, watersheds and estuaries. Zebra Mussels have found similar biotic and abiotic factors like their native ecosystems provided them. The Great Lakes are phytoplankton-rich, freshwater ecosystems.
How have the biotic and abiotic factors changed?
Change in biotic factors
Change in abiotic factors
Zebra Mussels attach onto substrates, including other organisms such as Unionidae Mussels which are native to Lake Erie. This will prevent the mussel from moving, breeding and feeding and will put them under a state of stress, causing death. This caused the dramatic reduction of native mussel populations in Lake St.Claire and Lake Erie. In 1990, 248 (17 species), in 1992, 99 (12 species) and in 1994, 6 (5 species) native mussels had been found in the three years. This data collected proves the decline in the population of native mussels. Soon, the native mussels will be extirpated from Lake Erie, since they are all ready endangered.
They were first discovered in Lake St.Claire, which connects Lake Erie and Huron, in 1988. European transoceanic ships must have discharged ballast water that contained larvae (called veligers) Zebra Mussels into Lake St.Claire. Adult Zebra Mussels have the ability to attach firmly onto substrates, like sediments. These Zebra Mussels would have survived and reproduced rapidly.

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By: Muneeza Sheikh
04/11/2014

Zebra Mussels negatively affect the abiotic factors in an ecosystem by:
Filtering water causing increased water clarity and light penetration resulting in toxic algal blooms
Decreasing oxygen levels by excreting psuedofeces affecting the energy flow, nutrient levels, biogeochemical cycles as well as other organisms
Zebra Mussels negatively impact the biotic factors in an ecosystem by:
Attaching onto substrates (this process is known as "biofouling'), including native mussels and other organisms causing suffocation and stress.
Consuming significant amounts of phytoplankton, causing its population to decrease.
Increasing competition for phytoplankton by consuming significant amounts of them and by filtering water containing phytoplankton and excreting them as pseudofeces.
Decreasing the biodiversity of the ecosystem.
Dense colonies of Zebra Mussels impact spawning areas of other organisms potentially resulting in decreased population of these organisms.
Impact on humans
Predator & prey relationship
If you spot a Zebra Mussel, you can:
Pick it up, preserve it in rubbing alcohol and report a sighting online or through an agency.
DO NOT put it back in the water because it can reproduce, only adding to the large population.
Also, they are invasive, but they are still animals and we should always treat them with respect
Zebra Mussels feed on phytoplankton by filtering them from the water, along with the most of the matter resulting in increased water clarity. Adult mussels filter a liter of water per day!
How do they dominate ecosystems?
Phytoplankton
Increased water clarity activates deeper light penetration allowing more photosynthesizing organisms, like blue-green algae, to photosynthesize. This promotes algal growth, which, some types in large amounts, can potentially be toxic. Since the nutrient levels are decreasing due to the increased water clarity, this changes our eutrophic ecosystems into oligotrophic which also contributes to stimulating the growth of aquatic vegetation but will also negatively affect the other organisms and biogeochemical cycles because their are less nutrients available in the water.
*(The native clams in this graph refer
to Unionidae Mussels)
Population distribution of Native And Invasive Mussels in Lake Erie, 1996
Zebra Mussels have colonized many areas in the Great Lakes. In some areas in Lake Erie, their population densities can reach over 100,000 per square meter! This large population is capable of filtering the freshwater in the Hudson River in only 2 to 4 days! The Unionid Mussels filtered the river every 2 to 3 months. At this increased rate, the water cannot recover from the nutrients lost to the Zebra Mussels. Zebra Mussels can also colonize in spawning areas of other organisms. These organisms, such as native fish and crab, will run out of space to lay their eggs and may also be forced to lay their eggs in Zebra Mussel colonies, where they may not survive, ultimately, decreasing the population of native species and the ecosystem's biodiversity as a whole.
Zebra Mussels consume significant amounts of phytoplankton, as well as release any uneaten phyto plankton, zooplankton and other particles in the form of feces known as "psuedofeces", which is the result of the reduction of some types of phytoplankton in Lake Erie of up to about 80%. This increases the competition for phytoplankton because since the population of the producers are decreasing, the primary consumer will have no other food source.

Direct Impact
Indirect Impact
Broken Zebra Mussel shells can be sharp, which may cause injuries.
When they decay in large amounts, they can release smelly odor.
When they firmly attach onto substrates like water intake structures and pipes causing build-up. This can also lead to clogging which costs millions of dollars to unclog
How have humans tried to help with the problem?
Well... we have tried a couple of things, but they were most likely unsuccessful because in order to completely eradicate Zebra Mussels altogether, everything else in the water must go too, including native species. This will basically destroy our freshwater ecosystems.

Scientists are trying to figure out a way to stimulate male hormones that make females release their eggs. This method will prevent fertilization of the egg which will drastically reduce, and maybe even prevent the reproduction of more Zebra Mussels.
They are also using mechanical control, such as using high pressure water and scraping to physically remove them from substrates.
Zebra Mussels only consume phytoplankton and some zooplankton, so what's the big deal?
Zebra Mussels greatly disrupt the aquatic food chain because they only consume phytoplankton in large amounts, and due to their high population they create competition in the food chain. Since the phytoplanktons are the producers, other primary consumers, like zooplankton, are forced to compete to consume the same food source
Zebra Mussels are bioaccumulators, meaning that any contaminant in the water gets multiplied up to 10 times the water concentration inside of them. This doesn't affect the Zebra Mussels directly, but it affects the consumers because the concentration of the contaminant increases in the food chain. This process will only increase as the Zebra Mussel population increases. More and more animals will consume them, and more and more harmful contaminants will be passed up the food chain, maybe even reaching humans from the fish we eat.
Some species of the blue-green algae that are growing due to the increased water clarity can be toxic. To add to this problem, Zebra Mussels are causing this over-growth of this algae, but they don't consume it either. So if they're not being eaten, this won't affect their increasing population, which may also contain types of blue-green algae that are toxic. As their population increases, more and more organisms will consume them and the contaminants will be passes up the food chain, possibly even reaching humans when we eat fish.
Zebra Mussels alter the nutrient cycle in the ecosystem by excreting the filtered phytoplankton and other matter into solid waste, called pseudofeces. Psuedofeces settle down on the bottom of the lake, thus, transferring the energy from the open water, (rest of the water) to the bottom of the lake.
When Zebra Mussels excrete psuedofeces, it collects at the bottom of the lake which changes the flow of energy, from the open water to the lake bottom. This has an affect on the food chain because the energy is not being transferred in the same direction.
Zebra Mussels consume phytoplankton and some zooplankton. These are the mussel's prey. As we go up the food chain, the top consumers are Largemouth Bass, Smallmouth Bass and Northern Pike. The Zebra Mussel has three predators, but the population of Zebra Mussels outnumber its predators. Due to this, the new predators in the Great Lakes cannot control the population of the Zebra Mussels.
Accidentally introducing a new species in an ecosystem, teaches us that there is a time and a place for everything
Zebra Mussels do not belong in our Great Lakes!
To prevent further invasion, you can look for mussels hiding on your boats, trailer and vehicles.
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