Flashcards in Lecture 25- Human impacts on estuaries Deck (29):
How many Australians live near the coast?
How many Australians live in major cities on estuaries?
Why do so many people live around estuaries? (3)
1. sheltered environment
2. drinking water
3. waterway for transport
In what ways are estuaries important?
3. Water supply
What is an example of an estuary being used for transport?
- about 3100 ship visits annually
-6.6 million tonnes exports annually
-37% of Australian container trade
-employs 13000 directly
-5.4 billion dollars revenue to Vic
How are estuaries important for food?
-e.g. Shrimp aquaculture, increased 300% from mid 80s to early 00's
-3/4 marine species harvested in the US use estuaries for part of their life cycle
-huge areas of land given over to aquaculture
-estuaries are important for the life cycle of many organisms that we eat
What is an example of an estuary being important for water supply?
-Sacramento: San Joaquin Delta
-738 000 acres
-drinking water for 22 million people
-1800+ agricultural users
-2 of the largest rivers in the US
-very manipulated ares
-environmental issues= in decline because of polution, introduced species and demand for water supply
-conflict between users
How are estuaries used for recreation?
-fishing, boating, sailing, water skiing, canoeing, bird watching
What are the human impacts on estuaries? (4)
1. Habitat modifications (mangroves, seagrasses, rivers)
2. Water quality
3. River mouth management
4. Introduced species
How have humans impacted in the mangrove estuarine habitat?
-more than 50% of mangroves worldwide have been cleared
-now used for intensive shrimp farming in tropics
-also for urban development
cleared for agriculture
- they are very productive areas= bad to get rid of them!
How have humans impacted the estuarine habitat of seagrasses?
-by coastal infrastructure=sea walls, so you get scour of sediment in front of the seawall and loss of seagrasses due to that
-boat moorings=clear patches, the chains drag on the ground
-dredging: e.g. channels
How have humans impacted the rivers in estuaries, give an example?
-Nagaragawa Estuary Barrage
-big wall separating the sea and river
-stops saltwater intrusion upstream
-ensures municipal water supply
-has fishways in the barrage= so the fish can migrate (catadramous and anadramous)
How have humans impacted the water quality in estuaries?
-affected by inputs of nutrients, contaminants and sediments (changes in pH, fertilizers= 34%, animal waste,point sources etc.)
What happened in Cockburn Sound and Western Port?
1. Cockburn Sound: seagrass loss due to increased nutrients
2. Western Port: seagrass loss due to turbidity
-not one cause of habitat loss, the water quality is important for plants and animals!
What is artificial river mouth management?
-control of river flow into the sea and vice versa
-often when the river mouth closes off (due to sediment deposition)
-surrounding development can affect natural opening and closing of the mouth
-decision whether or not to artificially open is a complex one
What are the factors included in making the decision to open/not open a river mouth? (7)
1. assets potentially impacted by decision
2. socioeconomic (roads and bridges, agricultural land, swimming, fishing, stormwater, human health)
3. environmental(fish, birds, plants)
4. cultural (cultural heritage, indigenous culture)
5. threat to those assets (could relate to opening or not)
6. threat modifiers (e.g. time since open, depth of oxygenated water)
7. mouth status (e.g. fluvial water flow, tidal flow)
Why is opening of the river mouth so important?
-part of a natural process
-many species need it
-makes the water and land healthy
-e.g,black bream- fish live permanently in estuaries, winter flushing of estuary is really important for its survival, movement of the salt wedge triggers spawning in bream
Why are estuaries more likely to have introduced species?
-often have ports and international shipping
What effects brought about by climate change will/ are impacting estuaries? (4)
1. Changes in river flow
2. Rising sea level
3. Increased air temperature
4. Extreme weather events
How does climate change brought change in river flow affect estuaries?
1: Reduced flow= increased salinity, reduced nutrients/contaminants from catchment, less flushing
2:Increased flow=reduced salinity, more sediment, more contaminants, more nutrients
How is the climate change induced rise in sea level going to affect mangroves and seagrasses?
1. Mangroves: migration landward where possible, as cannot survive permanents submersion, it will be complicated to migrate by possible increased sedimentation
2. Seagrasses: migration landward where possible, flooding and erosion= increased turbidity (bad for seagrasses)
How is the climate change induced rise in air temperature going to affect mangroves and seagrasses?
1. Mangroves: possible negative effects from increased soil salinity due to evaporation
2. Seagrasses: possible dieback if intertidal beds (as too high temperature when exposed)
How will the coastal habitats be impacted by extreme weather events? (due to climate change)
-coastal habitats may be damaged
-coastal habitats provide some protection to human assets (e.g. mangroves may reduce impact of storm surge or tsunami)
What is the Port Kembla Harbour example?
-heavy industry port
-water quality impacted as well as the biota
-then the water quality better but acts as a sediment sink for contaminants= when disturbed come up again
What is Port Kembla Harbour?
-24 million tonnes of cargo annually
-steelworks, copper smelter, coal loader, grain terminal, fertilizer plant
-extensively modified (used to be Tom Thumb Lagoon- now Inner Harbour)
-estuarine like circulation pattern discharge of heated effluent
-bad water quality, somewhat better now
What was the water quality like in Port Kembla Harbour?
-DO 20% lower
-cyanide 200x higher
-phenol 2x higer
-zinc 2-3x higher
-copper 7-9x higher
-lead 1.5-3x higher
=== this caused fish kills, and no macroscopic epibiota in upper Inner Harbour
How is Port Kembla Harbour a sink for contaminants?
-sediments act as sinks for contaminants
-contaminants remobilised by dredging
-the bioavailable again (kills fish etc.)
-can be accumulated by oysters
What used to be done with ballast water and what has that caused in Port Kembla Harbour?
-used to just let it go wherever
-caused introductions of species
-35 introduced, 14 cryptogenic