6.7b oceans

Question 1

ocean acidification

Answer 1

it is the ongoing decrease in the pH of the Earth’s oceans caused by the uptake of CO2 from the atmosphere

the top layer of the ocean mixes with the atmosphere so as the concentration of CO2 in the atmosphere increases, more CO2 is absorbed by oceans –> leading to ocean acidification

as the CO2 breaks into ions including hydrogen ions combine with carbonate ions in the ocean to form bicarbonate –> reducing the concentration of carbonate ions in the ocean

Question 2

why is ocean acidification disadvantageous

Answer 2

a disadvantage for marine species:
- they require carbonate ions to build and maintain calcium-based structures e.g. coral

a more acidic ocean dissolves and disintegrates coral reefs and makes the shells built by marine animals weaker and more fragile

Question 3

trend since the 1800s

Answer 3

since the 1800s, there has been a 30% drop in the pH of the ocean down to 8.1

coral reefs stop growing below a pH of 7.8!!!!

Question 4

impact of climate warming

Answer 4

climate warming means that coral bleaching is becoming more prominent –> hinders the growth of coral reefs in the future

Question 5

why are coral reefs important

Answer 5

coral reefs have vital ecosystem services:

• sheltering 25% of marine species
• protecting shorelines from waves, floods and storms, preventing loss of lives, property damage and erosion
• provide an income from tourism and support the fishing industry
  FOR EXAMPLE
  the Great Barrier Reef provides the Australian economy with 1.5 billion dollars each year

Question 6

critical threshold

Answer 6

whether the critical threshold is reached depends on the extent of climate warming

if changes are slow, organisms may be able to adapt and become more resilient