Deeper zones of global coral reefs are currently safe from warming waters

Distinct coral reef zones

1. Coral reefs consist of distinct zones. Each zone has conditions tied to light levels, water temperature, and wave energy.
2. They also differ in aspects of warming and nutrient availability. These varying conditions shape the types of corals and other organisms that can thrive in each zone.

Shallow reefs

• The uppermost zone, bathed in sunlight, is where most people think of when they picture a coral reef. This area is crucial for photosynthesis, allowing corals to partner with algae for energy. However, this zone is most vulnerable to extreme heat events driven by climate change.

Mesophotic reefs

1. Scientists from the University of Exeter and the University of Queensland focused their research on a deeper zone called the “mesophotic coral reef.”
2. This region exists in a twilight zone roughly 30-50 meters below the surface. Dimmer light penetrates to this depth, but it’s significantly less than the shallow reefs receive.
3. Ocean water isn’t static – currents, tides, and winds affect how different layers interact. Warmer surface water, driven hotter by climate change, doesn’t always blend thoroughly with the naturally cooler water in deeper regions.
4. Fortunately, this incomplete mixing can create a temperature buffer, temporarily shielding mesophotic reefs from some of the immediate effects of surface-level warming.

The hope (and the catch)

• “Coral reefs are a stark indicator of the widespread damage climate change causes to ecosystems,” says Dr. Jennifer McWhorter of NOAA’s Atlantic Oceanographic & Meteorological Laboratory (AOML), who led the study. “Our study highlights a potential area of resilience within the reefs, but also a clear limit to that resilience if warming continues.”
• The news from the study isn’t all positive. There’s a crucial caveat: this natural buffer zone provided by incomplete water mixing won’t last indefinitely. The research team warns that if global warming surpasses 3°C above pre-industrial levels, the protective effect will disappear.

Maintaining coral reef zone temperature differences

1. As global temperatures rise, the difference in temperature between surface and deep water layers lessens. This weaker thermal gradient reduces the resistance to mixing, allowing warmer surface water to penetrate deeper.
2. The result? Mesophotic reefs, once shielded, would become exposed to the same harmful heat currently stressing shallow reefs.
3. The study suggests that if global warming reaches 3°C, temperatures in mesophotic zones of the Great Barrier Reef would surpass 30°C. This is a critical threshold for many coral species.
4. Extended exposure to such temperatures can trigger widespread coral bleaching and mortality events. These die-offs could significantly disrupt the reef ecosystem, impacting the entire food chain and potentially leading to reef collapse.

Deep coral reef zones and warming

• While the existence of mesophotic reefs zones offers a glimmer of hope to warming, it’s important to understand the limitations of this potential refuge. The shallow and deeper zones of a coral reef ecosystem are not interchangeable.
• Certain coral species are specifically adapted to the high light levels found in the shallows. These sunlight-dependent corals, often vibrantly colored and brimming with symbiotic algae, wouldn’t be able to survive in the dimmer environment of the mesophotic zone.
• Even if the deeper communities persevere through rising temperatures, the loss of these shallow-water species would still inflict a devastating blow on the overall biodiversity and health of the reef ecosystem.

Warming risks on mesophotic reefs

1. To assess the future risk to mesophotic reefs, scientists employed a multi-faceted approach. They weaved together climate change projections, which predict the overall rise in global temperatures, with specific details about how the ocean layers in this region typically mix.
2. Factors like currents, tides, and wind patterns complexly influence this water mixing phenomenon. By incorporating these layers and their mixing tendencies, scientists were able to create a more nuanced picture of how future warming might specifically affect the mesophotic zone of the Great Barrier Reef.
3. Their calculations paint a concerning scenario: even under the most optimistic outlook with reduced greenhouse gas emissions, these deeper zones are predicted to warm by at least 0.5°C by 2050-60.
4. This warming effect intensifies significantly if emissions remain high, with projections suggesting a temperature increase of 1.2-1.7°C in the mesophotic zone.

Study significance

• This research highlights the urgency of fighting climate change and the complex ways it disrupts ocean life. To save coral reef ecosystems, we need a multifaceted strategy:

1. The study reaffirms the non-negotiable priority of drastically reducing greenhouse gas emissions. Addressing the root cause of rising ocean temperatures is paramount for the survival of coral reefs, both shallow and mesophotic.
2. The longer we delay action on this front, the more widespread and severe the damage will be. By reducing emissions swiftly, we can buy precious time, allowing more areas of the reef to maintain the natural protection offered by their current temperature differences.

Conservation of reefs from warming

• Dr. Paul Halloran of Exeter’s Global Systems Institute (GSI) stresses the need for targeted conservation efforts. This means focusing resources and management strategies on the reefs that exhibit the best chances of survival in a warming world.

SDGs, Targets, and Indicators

SDGs	Targets	Indicators
SDG 13: Climate Action	Target 13.3: Improve education, awareness-raising, and human and institutional capacity on climate change mitigation, adaptation, impact reduction, and early warning	Indicator 13.3.1: Number of countries that have integrated mitigation, adaptation, impact reduction, and early warning measures into primary, secondary, and tertiary curricula
SDG 14: Life Below Water	Target 14.2: Sustainably manage and protect marine and coastal ecosystems to avoid significant adverse impacts, including by strengthening their resilience and taking action for their restoration, to achieve healthy and productive oceans	Indicator 14.2.1: Proportion of national exclusive economic zones managed using ecosystem-based approaches
SDG 15: Life on Land	Target 15.1: By 2020, ensure the conservation, restoration, and sustainable use of terrestrial and inland freshwater ecosystems and their services, in particular forests, wetlands, mountains, and drylands, in line with obligations under international agreements	Indicator 15.1.1: Forest area as a proportion of total land area

1. Which SDGs are addressed or connected to the issues highlighted in the article?

• SDG 13: Climate Action
• SDG 14: Life Below Water
• SDG 15: Life on Land

2. What specific targets under those SDGs can be identified based on the article’s content?

• Target 13.3: Improve education, awareness-raising, and human and institutional capacity on climate change mitigation, adaptation, impact reduction, and early warning
• Target 14.2: Sustainably manage and protect marine and coastal ecosystems to avoid significant adverse impacts, including by strengthening their resilience and taking action for their restoration, to achieve healthy and productive oceans
• Target 15.1: By 2020, ensure the conservation, restoration, and sustainable use of terrestrial and inland freshwater ecosystems and their services, in particular forests, wetlands, mountains, and drylands, in line with obligations under international agreements

3. Are there any indicators mentioned or implied in the article that can be used to measure progress towards the identified targets?

• Indicator 13.3.1: Number of countries that have integrated mitigation, adaptation, impact reduction, and early warning measures into primary, secondary, and tertiary curricula
• Indicator 14.2.1: Proportion of national exclusive economic zones managed using ecosystem-based approaches
• Indicator 15.1.1: Forest area as a proportion of total land area

4. SDGs, Targets and Indicators

SDGs	Targets	Indicators
SDG 13: Climate Action	Target 13.3: Improve education, awareness-raising, and human and institutional capacity on climate change mitigation, adaptation, impact reduction, and early warning	Indicator 13.3.1: Number of countries that have integrated mitigation, adaptation, impact reduction, and early warning measures into primary, secondary, and tertiary curricula
SDG 14: Life Below Water	Target 14.2: Sustainably manage and protect marine and coastal ecosystems to avoid significant adverse impacts, including by strengthening their resilience and taking action for their restoration, to achieve healthy and productive oceans	Indicator 14.2.1: Proportion of national exclusive economic zones managed using ecosystem-based approaches
SDG 15: Life on Land	Target 15.1: By 2020, ensure the conservation, restoration, and sustainable use of terrestrial and inland freshwater ecosystems and their services, in particular forests, wetlands, mountains, and drylands, in line with obligations under international agreements	Indicator 15.1.1: Forest area as a proportion of total land area

Behold! This splendid article springs forth from the wellspring of knowledge, shaped by a wondrous proprietary AI technology that delved into a vast ocean of data, illuminating the path towards the Sustainable Development Goals. Remember that all rights are reserved by SDG Investors LLC, empowering us to champion progress together.

Source: earth.com

 



Join us, as fellow seekers of change, on a transformative journey at https://sdgtalks.ai/welcome, where you can become a member and actively contribute to shaping a brighter future.