Theme 3: Human Impacts on Catchments

Topic: Ocean Pollution

The land, river and sea connection

The land and sea are naturally connected to each other by rivers. Urban areas are directly connected to waterways by a system of gutters and drains on roads known as the stormwater system. Anything left lying on roads, driveways and other hard surfaces can be washed into the gutters then down the drains. Drains direct water into the nearest waterway, which in turn, run into the main river and then out to sea (or lakes or other water bodies in urban areas not on the coast). Water that enters the stormwater system is not treated.

In rural areas, land management practices can greatly determine what ends up in the river and sea. Erosion and excess fertiliser usage can result in soil and nutrients entering nearby creeks and river systems. Soil and nutrients remain in the water and flow downstream and out to sea.

Impacts of pollution on the marine environment

Seagrass die-back
Seagrass is different to seaweed. Seaweed (or macro algaes) do not have a true root system or leaves and are not a plant. Seagrasses are flowering plants but they are not a true grass because they do have leaves, roots, stems and flowers. Eleven species of seagrass are found in South Australia. Seagrass meadows in South Australia cover an area of 29,620 km. They are found growing on sandy or muddy bottoms in estuaries, coastal lagoons, bays and gulfs. Seagrass meadows located off the coast of metropolitan Adelaide have declined significantly in recent years. Human pollution has contributed the most to the die-back of seagrasses.

Seagrasses are an important feature of the marine environment. They oxygenate the water, recycle nutrients and provide shelter for marine animals and food for fish. Seagrass also play host to a diverse range of small organisms called epiphytes (plants) and epifauna (animals) which live and graze on the leaves, stems and root systems of the seagrass. Seagrass acts in the same way that trees do to prevent land-based erosion. Tree roots hold the soil together and the roots of the seagrass bind the sand particles together helping to reduce the movement of sand. They also form an important nursery area where many species of commercially important fish, such as the King George Whiting, can spend time growing before they move to the open ocean to live.

The two main threats to seagrass survival are:

• Increased nutrient levels - The marine environment generally has very low levels of nutrients contained in the water. Therefore seagrasses have adapted to living in a low nutrient environment and are sensitive to any increase in nutrient levels. Pollution of coastal waters from stormwater runoff, sewage discharge and oil spills put the habitats of seagrass communities at risk. Nutrients contained in these pollutants can cause algal blooms to form and also increase the growth rate of the epiphytes living on the seagrass. Both algal blooms and increased epiphytes can potentially block sunlight from penetrating the water's surface and reaching the seagrass. Without sunlight, seagrass are not able to grow.
• Sedimentation - Sediment can come from land development runoff, stormwater or through dredging. Boating may also stir up sediment. Suspended sediments in the water also reduce the ability of sunlight to reach the seagrass.

Introduced marine pests
Over 60 million tonnes of ballast water is deposited in Australian ports each year. Ballast water is carried in unladen ships to provide stability. It is taken onboard before a ship leaves port.

Living in the ballast water are small marine creatures. Many of these creatures die before they reach the next port, however, some still survive. When ships take on cargo at the next port, the ballast water is no longer needed and it is released. As this water is released, and marine creatures still living in this water are also released, some of these foreign creatures die in the new environment. However, a number of these creatures are also able to establish themselves in a new environment.

Over 100 known species have been introduced into Australian waters through ballast water. Many of these species have become pests because they compete with local native species for habitat and food. Many pest species also have the ability to reproduce very quickly. Others form colonies that can smother local species and kill them. There are many species of introduced marine pests that are threatening local marine life. However, many species have not yet reached Adelaide's waters. One species that has been recorded in Adelaide is the European Fan Worm Sabella spallanzanii. It was first recorded in Outer Harbour in 1985 and now can be found along the metropolitan coastline and across to Kangaroo Island. Another species found along metropolitan beaches is the European Shore Crab. This crab is now very commonly found on Adelaide beaches and is beginning to have an impact on local marine species.

Pollution and its impact on marine life
Much of the litter found in our oceans is from plastic materials, cigarette butts and fishing tackle. It is reported that there are approximately 46,000 pieces of bioplastic floating around in each square mile of ocean. This includes plastic bags, drink bottles, takeaway containers and 6-pack holders. Throughout the world, plastic kills up to 1 million sea birds, 100,000 sea mammals and countless fish every year.

Plastic bags pose the greatest threat to marine life because they are non-biodegradable, taking between 20 and 100 years to break down. Many marine animals, including birds, whales, seals and turtles often mistaken plastic bags as jellyfish and ingest them for food, eventually dying from intestinal blockages. To make matters worse, when the animal that digested the plastic bag dies, the animal decays at a much faster rate than the bag. As a result, the bag is released back into the environment more or less intact ready to be consumed by another animal.

Student Activity Ideas

• Research an introduced marine pest found in South Australia.
• Debate: People should be allowed to fish on South Australia's reefs.
• Debate: People should pay for the plastic bags they use when they go shopping.
• Scenario: Students own an advertising agency that has just landed an exclusive account from the South Australian government to sell the idea that humans need to look after the sea. Students can write a jingle or write a magazine, TV or radio advertisement to get their audience thinking about the value of the sea, and provide them with ideas on how they can help protect the marine environment.
• Students to choose a marine pollution issue and imagine they are an animal living in the affected area. They should think about some of the problems they would encounter. How would they overcome them? Would they survive? These issues can be explored further by writing a story about their adventures, or designing a poster to save their ecosystem from destruction by humans.
• Seagrass project: What animals live there? What products are made out of seagrass? Why is it important? What happens if the seagrass dies? Can too much seagrass be a bad thing?
• Discuss waste around the home and/or on a farm etc. List the types of waste and the method of disposal. Conduct a class survey, asking students to complete the survey with family members. How many of these waste items can end up in the ocean?

Enquiry Learning

• Describe the connection between water on land and the marine environment.
• How have land use changes in agriculture, human settlement, introduction of exotic plants and animals impacted on the health of Australian oceans?
• How have changes to catchments, from top to bottom, impacted on water quality, water quantity and biodiversity in oceans?
• What critical ecosystem services do oceans provide?
• How does stormwater pollution and sewage pollution impact on the health of ocean environments? Look at litter, nutrient pollution, faecal coliform, sediment, toxicants and other pollutants.
• Why are sea grasses an important feature of the marine environment?
• Why are plastics such a problem in the marine environment?

Internet Resources

Type	Description	Resources Covering the Topic
Easy	Natural Advantage: A Blueprint for Sustainable Australia. A comprehensive overview of sustainable development, including oceans and coastal issues.	Australian Conservation Foundation www.acfonline.org.au/asp/pages/ publicationtyp.asp?IdPublicationTyp=7
	Ocean pollution - a brief explanation.	Info Please www.infoplease.com/ce6/sci/ A0861891.html
	Sources and types of marine pollution. What we can do to help.	Australian Marine Conservation Society www.amcs.org.au/issues/facts/htm/ fcmpolln.htm
	Marine debris - what is it?	Australian Marine Conservation Society www.amcs.org.au/issues/facts/htm/ fcmrndeb.htm
	Beach-watch program in NSW. Website has information on beaches, how they become polluted and how to prevent beach pollution.	NSW EPA www.epa.nsw.gov.au/beach/ causes.htm
More Comprehensive	Lots of information about oil spills.	National Oceanic and Atmospheric Administration response.restoration.noaa.gov/kids/ kids.html
	A history of sea dumping in Australian waters.	Environment Australia www.ea.gov.au/coasts/pollution/ dumping/history/index.html
	What is water pollution? A comprehensive summary the different types of water pollution that enter the ocean.	VIC EPA www.epa.vic.gov.au/Water
	Oil spills.	Stop the Marine Pollution home2.pacific.net.sg/~oryanx/ index.html
	Seagrass decline and links to water quality off the Adelaide metropolitan coastline. A large downloadable PDF.	SA Government EPA www.dehaa.sa.gov.au/epa/pdfs/ seagrass.pdf

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