Increased regulation, connection of river networks, and enhanced shipping transport during the twentieth
century have augmented the transport of aquatic organisms across the world. Successful colonization of habitat by invasive species has had substantial consequences for food-web structure and ecosystem functioning. In North America's Great Lakes, the settlement of zebra mussels (Dreissena poly-morpha) has greatly enhanced the benthic filtering capacity and thus probably assisted in countering the eutrophication symptom of high algal densities. The completion of the Main-Donau canal has opened up the Rhine network for colonization by a Ponto-Caspian fauna from the Black Sea region, and vice versa. Several species are now greatly expanding their ranges and alter benthic communities. The arrival of the water hyacinth (Eichhor-nia crassipes) in Lake Victoria (East Africa) has precipitated major changes in the littoral and impeded access to the lake for riparian human communities. This was brought to a standstill by a combination of biological control (introduction of the weevil Neochetina) and an unprecedented severe El Nino event.
See also: Aquatic Ecosystem Services; Biomanipulation of Aquatic Ecosystems; Eutrophication of Lakes and Reservoirs; Lake and Reservoir Management; Lake Management, Criteria; Littoral Zone.
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