Global warming and corals: How the past informs the present

The importance of coral reefs in aquatic ecosystems cannot be underestimated. They are the engineers of the deep sea, creating habitat and helping to secure the survival of many species on the ocean floor. 

Yet, these heroes of the ocean are not invincible. Coral survival is impacted by changes in their environment, such as fluctuations in temperature, acidity, oxygen, and food availability. Any of these factors can affect the health of corals and the survival of the creatures who depend on them. 

Researchers at the Center for Marine Environmental Sciences of the University of Bremen (MARUM) wanted to know more about how corals are affected by environmental change. To investigate, they examined the cold-water coral species Lophelia pertusa. 

“We looked back into the past to understand how Lophelia pertusa reacted to environmental changes,” said study first author Rodrigo da Costa Portilho-Ramos.

The study considered the most crucial environmental parameters over the last 20,000 years. This time period represents the warming of the planet since the last glaciation. 

The experts found that L. pertusa would disappear and then reappear from an area when the oxygen content or food supply changed. They also discovered that temperature and salinity did not seem to affect the ability of the coral to survive or reproduce. 

“We therefore assume that food supply and availability of oxygen are the primary factors that determine the life or death of cold-water corals,” said Portilho-Ramos.

The research team could not determine the effect of acidification over the long term because it was not possible to measure the history of acidification in the ocean.  

Deep-sea corals affect many aspects of the marine ecosystem, from nutrient cycles to fish reproductive success. The team believes the information gathered in their study will help inform future marine conservation in an ever-changing climate. 

“Here, we present the synthesis of 6 case studies from the North Atlantic Ocean and the Mediterranean Sea, revealing that food supply controlled by export production and turbulent hydrodynamics at the seabed exerted the strongest impact on coral vitality during the past 20,000 years, whereas locally low oxygen concentrations in the bottom water can act as an additional relevant stressor,” wrote the study authors. 

“The fate of cold-water corals in a changing ocean will largely depend on how these oceanographic processes will be modulated. Future ocean deoxygenation may be compensated regionally where the food delivery and food quality are optimal.”

The study is published in the journal PLoS Biology.

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By Erin Moody , Earth.com Staff Writer