Lecture 25- Human impacts on estuaries

Question 1

How many Australians live near the coast?

Answer 1

-80%

Question 2

How many Australians live in major cities on estuaries?

Answer 2

-65%

Question 3

Why do so many people live around estuaries? (3)

Answer 3

1. sheltered environment
2. drinking water
3. waterway for transport

Question 4

In what ways are estuaries important?

Answer 4

1. Transport
2. Food
3. Water supply
4. Recreation

Question 5

What is an example of an estuary being used for transport?

Answer 5

• Port Melbourne
• 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

Question 6

How are estuaries important for food?

Answer 6

• 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
• increasingly important
• estuaries are important for the life cycle of many organisms that we eat

Question 7

What is an example of an estuary being important for water supply?

Answer 7

• 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

Question 8

How are estuaries used for recreation?

Answer 8

-fishing, boating, sailing, water skiing, canoeing, bird watching

Question 9

What are the human impacts on estuaries? (4)

Answer 9

1. Habitat modifications (mangroves, seagrasses, rivers)
2. Water quality
3. River mouth management
4. Introduced species

Question 10

How have humans impacted in the mangrove estuarine habitat?

Answer 10

-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!

Question 11

How have humans impacted the estuarine habitat of seagrasses?

Answer 11

• 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

Question 12

How have humans impacted the rivers in estuaries, give an example?

Answer 12

• Nagaragawa Estuary Barrage
• big wall separating the sea and river
• stops saltwater intrusion upstream
• ensures municipal water supply
• controls flooding
• has fishways in the barrage= so the fish can migrate (catadramous and anadramous)

Question 13

How have humans impacted the water quality in estuaries?

Answer 13

-affected by inputs of nutrients, contaminants and sediments (changes in pH, fertilizers= 34%, animal waste,point sources etc.)

Question 14

What happened in Cockburn Sound and Western Port?

Answer 14

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!

Question 15

What is artificial river mouth management?

Answer 15

• 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

Question 16

What are the factors included in making the decision to open/not open a river mouth? (7)

Answer 16

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)

Question 17

Why is opening of the river mouth so important?

Answer 17

• 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

Question 18

Why are estuaries more likely to have introduced species?

Answer 18

-often have ports and international shipping

Question 19

What effects brought about by climate change will/ are impacting estuaries? (4)

Answer 19

1. Changes in river flow
2. Rising sea level
3. Increased air temperature
4. Extreme weather events

Question 20

How does climate change brought change in river flow affect estuaries?

Answer 20

1: Reduced flow= increased salinity, reduced nutrients/contaminants from catchment, less flushing
2: Increased flow=reduced salinity, more sediment, more contaminants, more nutrients

Question 21

How is the climate change induced rise in sea level going to affect mangroves and seagrasses?

Answer 21

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)

Question 22

How is the climate change induced rise in air temperature going to affect mangroves and seagrasses?

Answer 22

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)

Question 23

How will the coastal habitats be impacted by extreme weather events? (due to climate change)

Answer 23

• coastal habitats may be damaged

- coastal habitats provide some protection to human assets (e.g. mangroves may reduce impact of storm surge or tsunami)

Question 24

What is the Port Kembla Harbour example?

Answer 24

• 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

Question 25

What is Port Kembla Harbour?

Answer 25

-big port
-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
artificial harbour
-bad water quality, somewhat better now

Question 26

What was the water quality like in Port Kembla Harbour?

Answer 26

-very bad
-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
-nothing alive!

Question 27

How is Port Kembla Harbour a sink for contaminants?

Answer 27

• sediments act as sinks for contaminants
• contaminants remobilised by dredging
• the bioavailable again (kills fish etc.)
• can be accumulated by oysters

Question 28

What used to be done with ballast water and what has that caused in Port Kembla Harbour?

Answer 28

• used to just let it go wherever
• now controlled
• caused introductions of species
• 35 introduced, 14 cryptogenic

Question 29

What is seiching?

Answer 29

• The key requirement for formation of a seiche is that the body of water be at least partially bounded, allowing the formation of the standing wave.
• the Port Kembla Harbour example= outer harbour is susceptible to it, inner harbour= benthic infauna reduced in the middle of the Inner HArbour