Sources:

1. sewage, industrial wastes, agricultural wastes

2. ocean dumping

3. oil spills

Coastal areas most affected by sewage :

 Bangladesh. India Pakistan. Indonesia, Malaysia, Thailand and Philippines – NO TREATMENT

 Latin America - 98% not treated

 Mediterranean basin -85% not treated

 US - 35% not treated

Toxic Chemicals and Plastics

         toxic chemicals kill/harm marine organisms especially fish and shellfish affect fishery

         whales, seals, dolphins, sea lions sea turtles die when they ingest/become entangled in plastic

wastes and plastic rings

Eutrophication:

~ nitrogen and phosphorous rise sharply in coastal waters (from sewage and agriculture)

fast reproduction of microscopic algae, i.e. algal bloom (or red tides)

oxygen m water used up

other marine organisms suffocate

some algae produce toxins

kill marine organisms

- oceans can dilute, disperse and degrade large amounts of wastes especially in deep water areas

- the dilution and renewal capacity of the ocean is limited.

Controversy over ocean dumping

- affect coastal tourism industry and fishing industry

- safer and cheaper than land dumping (landfill) and incineration

Oil Pollution ~ Sources:

1.     tanker accidents 10-15%

2.     blowouts at drilling rigs

3.     waste oil dump onto land oceans

4.     washing tankers with seawater

5.     environmental terrorism/ wars

Effects:

1. toxic components kill marine organisms

2. floating oil coats feathers of birds and fur of mammals die from drowning / cold

3. heavy components sink kill bottom dwelling organisms e.g. crabs, shrimps (not fit for human consumption)

Working with nature to purify sewage:

1. Channel sewage into holding ponds solids fall to bottom, bacteria decompose them after 20-30 days; water used for irrigation, raising fish in ponds

2.Divert sewage to natural wetlands (marshes or mangroves)

- decompose organic matter decomposed

- nitrogen and phosphorous nutrients absorbed

- toxic materials filtered out

3. Artificial wetlands used in some towns in N. America

4. Green houses containing rows of large tanks of aquatic plants

-   organic matter decomposed by bacteria into nutrients

-      nutrients absorbed by plants

-      toxic metals absorbed into trees

-      water passes to aquariums:

microorganisms snails and zooplankton fish for sold

Compared with sewage treatment plants:

- cheap

- easy to maintain

- but require more land