New evidence from the Australian Marine Conservation Society highlights the severity of coral bleaching in the southern Great Barrier Reef due to unprecedented marine heatwaves.
Causes and Effects of Coral Bleaching
- Cause: Coral bleaching occurs when corals undergo stress from extreme conditions like temperature, light, and nutrients, leading them to expel symbiotic algae (zooxanthellae) and turn white.
- Effect: Prolonged bleaching or stress can lead to coral mortality.
Temperature Trends
- March 2024 saw global sea surface temperatures reach a record high of 21.07°C, following February’s 21.06°C.
- Marine heatwaves, previously unseen in the reef, have caused extreme temperatures, with some parts experiencing up to 14.5-degree heating weeks, surpassing the 2020 record of 11.8 heating weeks.
Degree Heating Weeks (DHW)
- DHW, an indicator of thermal stress on corals, reached unprecedented levels during the current event, with the southern reef recording a new high of 17.7 DHW.
- DHW is calculated using long-term temperature data and remote sensed sea surface temperature data.
Expert Observations
- Marine biologist Terence Hughes describes the ongoing event as the most severe, with the highest heat exposure on record for the southern region.
- Coral expert Selina Ward notes extensive bleaching across all 16 sites she visited in the southern section, surpassing any event witnessed since 1992.
- Great Barrier Reef Campaign Manager Lissa Schindler reports extensive and severe bleaching in central and northern parts, surpassing previous events in 2020 and 2022.
Impact and Consequences
- The ongoing event marks the fifth mass coral bleaching in eight years.
- Aerial footage reveals 75% of the Great Barrier Reef impacted, with much falling under high to extreme bleaching categories.
- Mass mortality has been observed since February and is expected to continue in the coming months.
Urgent Call to Action
- Experts emphasize the urgent need to reduce greenhouse gas emissions to mitigate further damage to coral reefs.
- The severity of the current bleaching event underscores the dwindling time to address climate change impacts.
Multiple Choice Questions (MCQs):
- What is the primary cause of coral bleaching?
- A) Overfishing
- B) Nutrient pollution
- C) Extreme conditions like temperature, light, and nutrients
- D) Oil spills
- Answer: C) Extreme conditions like temperature, light, and nutrients
- What is the significance of Degree Heating Weeks (DHW) in estimating coral bleaching?
- A) It measures the depth of affected corals.
- B) It predicts the severity of marine heatwaves.
- C) It estimates the thermal stress on corals.
- D) It calculates the rate of coral regeneration.
- Answer: C) It estimates the thermal stress on corals
- Which event is considered the worst bleaching in the history of the Great Barrier Reef?
- A) 2016
- B) 2020
- C) 2022
- D) 2024
- Answer: A) 2016
- What percentage of the Great Barrier Reef has been impacted by the current bleaching event?
- A) 25%
- B) 50%
- C) 75%
- D) 100%
- Answer: C) 75%
- According to experts, what urgent action is needed to address the ongoing coral bleaching events?
- A) Increase tourism to generate awareness
- B) Initiate coral transplantation programs
- C) Reduce greenhouse gas emissions immediately
- D) Implement stricter fishing regulations
- Answer: C) Reduce greenhouse gas emissions immediately