Dams and Reservoirs Harming Fish-BB

Problems Caused by Dams and Reservoirs

• Alter rivers flow, which affects downstream ecosystems and the landscape through which the river flows
• Hold back sediments that would naturally replenish downstream ecosystems
• When rivers are deprived of sediment loads they seek to reccapture it by eroding the downstream river bedd and banks debiltating bridges and other riverbank structures.
• Large dams have led to the extinction of many fish and other aquatic species
• Tend to fragment riverine ecosystem
• Isolate populations of species living up and downstream of the dam
• Cut off migrations and other species movements
• isolate rivers from their floodplain
• Fragmentation of river ecosystem=massive reduction in the number of species in the worlds watersheds
• Inhibit migratory fish movements
• Inundate spawning areas, change historic river flow patterns, and raise water temperatures

Possible Answers

• Fish passes can be made to facilitate passage but its not heavily researched.

Works Cited:

Environmental Impacts of Dams. International Rivers.  Retrieved March 7, 2012, from http://www.internationalrivers.org/en/node/1545

Rivers No More: The Environmental Effects of Large Dams. International Rivers. Retrieved March 7, 2012, from http://www.internationalrivers.org/en/node/1636

Reservoirs: Global Issues. Homepage- CIWEM. Retrieved March 7, 012 from http://www.ciwem.org/knowledge-networks/panels/water-resources/reservoirs-global-issues-.aspx

Systems, p., & Turbines., t. j. (n.d.). Dams: Impacts on Salmon and Steelhead. Northwest Power and Conservation Council. Retrieved March 7, 3023, from http://www.nwcouncil.org/hisotry/Dam

Zebra Mussels-JC

I. What is the Zebra Mussel?

a.  The Zebra mussel is a very small mussel, usually less than an inch but up to two inches in length. They have a striped, brownish, D-shaped shell. They grow in attached clusters and usually attach themselves to solid objects, in the same manner as barnacles. They were native to Europe and Asia and did not appear in the United States until the mid 1980’s.

II. How did they come the US?

a. The mussels first appeared in the Great Lakes, where they are still rampant. They were accidentally introduced through the dispersion of ballast water of barges from Asia and Europe. They most likely existed in the water as larvae and matured in the American waters where they were dumped and began to reproduce prolifically.

III.  Problems Caused

a.    In order to feed, zebra mussels suck water into their bodies and filter out microscopic particles of plants, animals, and debris. This extreme amount of intake depletes the water of food that other marine life depend upon, leading to the death of some species. Also, the decrease in particles in the water increases clarity, which can hinder large fish from catching their prey and

b. Zebra Mussels eat all algae except blue-green algae. This results in    a harmful abundance of blue-green algae in areas that are affected.

c. Zebra Mussels attach themselves to other objects, especially other mussels which are then smothered. They also attach themselves to manmade structures such as motors and bulkheads, resulting in a large amount of money being spent to clean up these structures.

Works Cited:

Invasive Species- Zebra Mussels (Dreissena polymorpha). Retrieved March 7, 2012,          from http://dnr.wi.gov/invasives/fact/zebra.htm.

Zebra Mussels: Invaders from Another Land

They came, They saw, They conquered

Sewage-JL

What It Is

Sewage

-       sources: domestic, commercial, industrial, shipping discharges

-       ex. excrement from toilets, wastewater, etc.

-       in developed countries, wastes travel to sewage treatment facilities- partly treated and sometimes untreated sewage is sometimes discharged due to facility malfunctions, inadequate infrastructure, etc.  

-       in developing or not developed countries there are often no sanitation facilities- human wastes go directly into coastal waters

-       in some developed regions raw sewage is poured into harbors, bays, and coastal waters (ex. Halifax Harbor in Nova Scotia)

-       sewage sludge- semisolid byproduct of the sewage treatment process; disposed at sea in some countries

Why It Is an Issue

-       some substances in sewage can harm ecosystems and be a threat to public health

-       sewage carries potentially disease-causing microbes called pathogens- main cause of recreational beach closures

-       study conducted by the United Nations Environmental Program (UNEP)

o   sewage may be “the most serious problem” affecting the marine environment- the least amount of progress has been made in this area

o   80% of sewage entering the ocean from developing countries is raw and untreated

o   ver 50% of sewage entering the Mediterranean Sea is untreated

o   the number of coastal dead zones doubled every decade since 1960- rising levels of nitrogen and phosphorous levels from sewage and runoff

o   growing coastal population means more waste- it is “steadily growing worse”

Sources:

http://www.ens-newswire.com/ens/oct2006/2006-10-04-01.asp

http://www.waterencyclopedia.com/Po-Re/Pollution-of-the-Ocean-by-Sewage-Nutrients-and-Chemicals.html

Research by: JL