OCEANS ON THE EDGE 3 Unsustainable use of marine ecosystems Key words: unsustainable food web nutrient eutrophication Starter: Why is the animal in the picture so important? Learning Objective: To be able to identify processes that disrupt marine food webs

Unsustainable uses include: Overfishing – where oceans are fished at a greater rate than they stock of fish can be replenished by breeding Habitat destruction Pollution

Krill under threat Krill populations have decreased by 80% since 1980. Krill are under threat from ‘suction harvesting’ to meet growing demand for krill Omega 3 health supplements Food for fish farms Onboard processing and fast-freeze means ships can take even bigger harvests!

Marine food webs Southern Ocean Explain why krill are important to the food web in the Southern Ocean in Antarctica. Explain why the krill are under threat Food web = several food chains that link together

Nutrient Overloading Pollution causes disruption to the nutrient cycles. Nutrient overloading is called eutrophication, it is creating dead zones. Dead zones are critically low in oxygen and are unable to support life. Now common offshore from developed and over populated countries. Increase in extreme storms (due to climate change) may mean more flooding, and so more flushing of nitrates and phosphates into the sea. Mention eutrophication – more detail on following slides

Marine Eutropthication

Marine Eutrophication Copy and complete the following (the words you need are at the bottom to help) Marine Eutrophication _____ and sewage wash into the oceans. Toxic ‘blue algal blooms’ grow on all the extra _____. Marine bacteria feed on _____ in the blooms. When they die they sink to the _____ and decay. The blooms also block _____ from marine plants, which causes many to die and decay. This uses up _____ dissolved in the oceans. Highly _____ conditions result, which asphyxiate bottom-dwelling organisms like worms and shellfish as other marine life dies due to lack of _____ and oxygen. In turn this affects fish, and even us who may _____ the poisonous fish nutrients oxygen food algae Fertilisers bottom poisonous eat light Asphyxiate: die from lack of oxygen

And finally ... In the back of your book write down 3 key words ... ... now pass them to the person next to you, can they define them?