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The Great Lakes and St. Lawrence Seaway
A Fragile Ecosystem
Previously discussed:
 The Great Lakes contain about 1/5th or 20% of the world’s fresh surface water
 The construction of the seaway and locks allows ships to connect from the
Atlantic Ocean all the way up to Lake Superior
 Approximately 40 million people live in this region (including both the USA side
and the Canadian side)
 Many factories/industries are located in this region
 Locks and dams have been constructed to raise/lower ships and control water
Impacts of Human Activities on this Fragile Ecosystem:
1. Invasive Species (See Fig. 1 and 2)
- Species from other places arrive in the ballast water of boats (the water used
to balance out the cargo load)
- Once here, they disrupt the food chain and become over-populated
2. Water Pollution (See Fig. 3)
- Output from factories or spills from ships can release harmful materials and
chemicals into the water
- This can cause mutations or death in marine organisms (e.g. fish, plants etc.)
3. Urbanization/Development
- The constant building of homes, factories, condos, sky-scrapers, malls,
parking lots etc. is reducing the “buffer zone” along the water (a buffer zone
is natural vegetation like grasses that can filter the water running off the
ground from a city into the lake or river)
- The more people that move into the region, the less vegetation there will be
Fig. 1 – Zebra Mussel
Fig. 2 – Round Goby
Fig. 3 – Mutated Fish
Round Goby - wikipedia
Range/Habitat
Widspread in the Sea of Marmara and rivers of its basin. In the Black Sea and Sea of Azov along all
coasts and fresh waters of their basins. In the coastal lakes and lagoons. In the rivers of Crimea and
Caucasus: Mezib, Pshada, Vulan, Kodori, Çoruh. In the Caspian Sea presented by subspecies
Neogobius melanostomus affinis. Since 1990 the round goby registered as introduced in the North
American Great Lakes as an invasive species. [1] and different parts of Europe.
Round gobies are euryhaline (salt-tolerant) and are found in both freshwater and marine ecosystems. In
habits the water with mineralization of 18-24%, presented in fresh waters. Rather common on shelfs
with sandy and rocky bottoms with low silting, on the depth from 1-2 to 10–17 m.
Feeding
Round gobies usually feed nocturnally (but have been observed to feed diurnally as well) and are
believed to detect prey only while stationary. The primary diet of round gobies includes mollusks,
crustaceans, worms, fish eggs, zebra mussels, small fish, and insect larvae.
Reproduction
Round gobies exhibit male parental care. Females can spawn up to six times during the spawning
season, which spans April to September. Males will migrate from the deeper water, where
overwintering occurs, into shallower breeding grounds during the beginning of the mating season. The
males are territorial and will guard nests of eggs and newly hatched young, resulting in successful
hatch rates of up to 95%. Its eggs are 4 mm by 2.2 mm in size. Female round gobies reach sexual
maturity in 1 to 2 years while males do so in 3 to 4 years. Gobies in the Laurentian Great Lakes
typically mature up to 1 year earlier than in their native habitat in Europe
species [edit]
Round goby from the Great Lakes, USA
The species was accidentally introduced into the North American Great Lakes by way of ballast water
transfer in cargo ships. First discovered in North America in the St. Clair River in 1990, the round
goby is considered an invasive species with significant ecological and economic impact;[7] the
consequences are quite complex as the fish both competes with native species and provides an
abundant source of food for them while consuming other invasive species.[8] In other words, the round
goby behaves much like most biological invasive controls. An aggressive fish, the round goby
outcompetes native species such as the sculpin and logperch for food (such as snails and mussels),
shelter and nesting sites, substantially reducing their numbers. Round gobies are also voracious
predators of eggs of native fish, many important to the angling industry. The goby's robust ability to
survive in degraded environmental conditions has helped to increase its competitive advantage
compared to native species.