Impact of Coral Bleaching in Cabo Pulmo

By: BCI (Based on the presentation by Dr. Héctor Reyes and M.Sc. Alejandra Robles Payán, “Impact of the El Niño Phenomenon on the Coral Communities of Cabo Pulmo National Park 2023-2024”)

You may have heard that coral reefs are bleaching in Cabo Pulmo and other parts of the world, but why is this happening? How does bleaching affect corals and the animals that live in these ecosystems?

Causes of Coral Bleaching in Cabo Pulmo

According to data from the National Oceanic and Atmospheric Administration (NOAA), in 2023, the Eastern Tropical Pacific experienced a significant increase in sea temperatures. It is estimated that the temperature rise in the region resulted from the combination of the 2022 volcanic activity of Hunga Tonga-Hunga Ha'apai in the Indo-Pacific, the 2023 El Niño phenomenon, and the cumulative effects of climate change. These conditions led to high ocean temperatures, and in Cabo Pulmo (located in BCS, Mexico), they exceeded the critical threshold of 29.3°C (which equals 84.74 °F) from July to October 2023, causing coral bleaching and mortality in the region.

Corals can endure heat stress for a few weeks, but if high temperatures persist, the damage is irreversible, causing significant mortality. In 2023, elevated temperatures lasted for more than 20 weeks in many parts of the world. In Mexico, mass mortality was reported, with millions of corals dead along the coasts of the Pacific, the Caribbean, and the Gulf of Mexico, devastating entire reefs.

Cabo Pulmo: An Ecosystem in Danger

Cabo Pulmo, known for its impressive marine biodiversity, is facing an alarming crisis. The rise in sea temperature is severely affecting coral reefs in this region, which are essential for marine life and the local economy. In 2023, due to unusually high water temperatures, 65% of corals were bleached along with a 36% mortality. Although the corals showed great resilience compared to other regions in Mexico and the world, this phenomenon not only threatens the marine ecosystem but also long-term economic activities dependent on tourism and fishing.

The Impact of Coral Bleaching in Cabo Pulmo

Dr. Héctor Reyes, a prominent researcher at the Autonomous University of Baja California Sur, has been monitoring coral health in Cabo Pulmo since 1987. According to his data, the Cabo Pulmo reef has experienced four bleaching events, and each event has caused a significant decrease in coral cover:

Impact on Marine Fauna in Cabo Pulmo

During 2023 and 2024, an exhaustive analysis of the impact of coral bleaching on invertebrates and fish in Cabo Pulmo was conducted, revealing significant results about the marine fauna's response to this phenomenon.

For invertebrates, an initial decrease in species abundance was observed due to the mortality of those directly dependent on coral for food. This initial loss raised concerns about the future of biodiversity in the area. However, recent observations indicate that species richness and diversity are gradually recovering. This recovery process suggests a remarkable adaptive capacity of the invertebrate community to stress events caused by temperature increases, although continuous monitoring will be necessary to assess its long-term evolution.

Initially, a decrease in fish numbers was recorded, but unlike invertebrates, the fish community rebounded once sea temperatures returned to normal conditions (some species moved but returned). This indicates that fish were not directly affected by the bleaching phenomenon but rather by the elevated temperatures. Researchers suggest continued monitoring for a more comprehensive evaluation of these changes in Cabo Pulmo.

The Recovery Process: A Long Journey

Coral recovery is a slow process. After the 2015 bleaching event, in 2023 corals had recovered 5 % of their recorded cover, meaning it took 8 years (0.6% cover per year) to regain their previous cover. However, due to the severity of the 2023 event, recovery could take up to 10 years, especially if cyclones or other adverse events occur.

Actions for Conservation and Restoration

In light of this situation, several measures are proposed to protect and restore corals:

1. Improvements in park management: Reducing the number of tourists and human activities in different diving sites to lessen additional stress on the corals.

2. Restoration actions: Aiming to assist in the recovery of these ecosystems by implementing restoration projects using corals that have shown higher survival rates under high-temperature conditions.

3. Education and awareness: Informing the community and visitors about the importance of using biodegradable sunscreens and avoiding practices that harm the marine ecosystem.

The study by Dr. Héctor Reyes and M.Sc. Alejandra Robles Payán offers a valuable glimpse into the future of marine ecosystems in the face of the ongoing challenge of climate change and global warming. With CO2 and other greenhouse gas emissions persisting in the atmosphere, environmental conditions will likely continue to change in the coming decades. What has been witnessed and documented in Cabo Pulmo could very well reflect what awaits us in 2040 and beyond. Those species and communities that have demonstrated resilience and adaptability have a higher chance of persisting in this uncertain future, while those that failed to withstand the challenges face a grimmer reality. 

It is imperative that we act now to implement conservation and restoration measures that help protect these valuable marine ecosystems and ensure their long-term survival. Without decisive and coordinated action, we risk irreparably losing the vast biodiversity and important ecosystem services these marine habitats provide us.