Riccardo Liguori A new study, published in Communications biology, shows how environmental stress is altering their behavior, putting the balance of the marine ecosystem at risk
@Canva
Coral reefs represent an important ecosystem for the balance of our oceans, but at the same time are among the most sensitive to climate change and ocean acidification, overfishing, and pollution. Now, a new study, published in Communications Biology, warns that these stressors have dramatic consequences for the species inhabiting these reefs, such as is the case with grey reef sharks (Carcharhinus amblyrhynchos).
The study: eight years of observation in the Chagos archipelago
A team of international researchers, led by marine scientists at Lancaster University and the Zoological Society of London, fitted 120 sharks with acoustic trackers and installed receivers around the coral atolls to monitor their movements inside the reefs of the Chagos Archipelago in the Indo-Pacific between 2013 and 2020.
In collaboration with Earth observation scientists at King’s College London, over 714,000 acoustic detections were combined with satellite data to understand the sharks’ behavior in response to environmental changes.
Findings: environmental stress drives sharks away from reefs
This study illustrates an increased environmental stress on coral reefs through bleaching events and changes in water temperature, which leads to a substantial reduction in residency by the grey reef sharks. These are the predators that move away from more damaged reefs by shifting to less stressed areas or even abandoning the reefs for periods.
Due to this rather unnatural process, sharks have begun to range further and longer from their shallow water habitats where feeding and reproduction generally occur.
The consequences: an ecosystem at risk
The grey reef sharks are very important in terms of maintaining healthy coral reefs. These marine predators spend most of their day cruising around the reefs, keeping the populations of herbivorous fish down, which maintains a balance between the corals and algae. Their presence is also crucial for preserving fish population genetic diversity, thereby underpinning the resilience of the ecosystem.
If sharks remain absent for long periods, herbivore populations could get out of control, causing degradation of coral and loss of biodiversity. Sharks also help in the process of nutrient transference across different areas of the ocean, a process vital to the health of coral reefs.
Their reduced presence, as noted in the study, would further weaken the resilience of these already fragile ecosystems and hasten their destruction.
