Threats + Management

Question 1

Value of coral reefs

Answer 1

• over 4000 species of fish + 800 species of coral currently identified only on reefs
• 1/4 of total fish caught support over 1 billion people in Asia alone
• total economic value = $56 billion, provides 64,000 jobs
• medical research - e.g. cytarabine from sea sponges is used by 500,000 people alone in US to treat leukaemia

Question 2

Threats to coral reefs

Answer 2

• coral bleaching
• El Niño
• land use
• invasive species

Question 3

Coral bleaching

Answer 3

• caused by rising sea temperatures associated with global warming (29°C +)
• 1°C above 29°C for 4 weeks trigger bleaching = zooxanthellae leave (gives coral colour), leaving polyp with an energy deficit + will die if not brief
• mass bleaching 2016-2020 damaged 30% of coral reef in 2016 alone

Question 4

El Niño

Answer 4

• periodic warming of sea temp in pacific
• intensifies temperature change due to warm water being transferred to the east due to the weakening of trade winds
• this causes a rising in temp of coral reefs in the east = greater risk of coral bleaching

Question 5

Land use

Answer 5

• unsustainable land-based human activity such as deforestation or poorly regulated agriculture
• causes the release of excess amounts of sediment + nutrients from agricultural waste
• these pollutants damages coral reefs with sedimentation choking coral + also reducing water quality + light availability
• e.g. mining activities have doubled in Queensland since 1990s = Curtis island causing industrial run off into sea

Question 6

Invasive species

Answer 6

• Crown of thorn starfish = important to ecosystem but outbreaks can lead to mass destruction
• one COTs can eat 10m2 of a coral a year