(ORDO NEWS) — Coral reefs are of great importance both for the Earth’s biosphere and for human economic activity.
All the more alarming is the decline in their numbers, which is associated with global warming. In a new article, scientists make disappointing, but still not hopeless predictions about the future of corals.
Coral reefs look spectacular and are literally teeming with life, which is why their possible disappearance is alarming.
But reefs are also necessary for fishing, protect the shores and their inhabitants, taking on the blows of storms, and even withstand floods and rising sea levels. Their economic importance, in turn, is estimated at tens of millions of dollars.
However, now this important component of the Earth’s biosphere is under threat. Coral reefs could disappear completely in about 80 years, by the end of the 21st century, if global temperature rises continue at current rates. There is already a noticeable decline in these communities.
“Entire reefs where I used to scuba dive are completely lost. In others, you will no longer meet certain types of living beings. And these changes continue to happen, ” says Dan Holstein from the Department of Oceanography and Coastal Studies at Louisiana State University (USA).
What makes corals especially sensitive is their symbiosis with the microscopic algae necessary for the survival of these animals.
Coral polyps are of the stinging type (along with jellyfish or hydra) and feed on small living creatures that are caught by tentacles. At the same time, single-celled green algae live inside their tissues and are engaged in photosynthesis.
The relationship of these two types can be called mutualistic symbiosis, that is, mutually beneficial cohabitation. The polyp provides the algae with a safe and comfortable place to live, and in return it supplies it with oxygen, synthesizes sugars, and removes the waste products of its host.
However, this fine-tuned alliance is in jeopardy, as are other components of reef ecosystems. The gradual warming of the ocean deprives them of stability and makes them less balanced – something similar is happening on land in the meantime.
Dr. Golstein and his colleagues created a computer model that for the first time predicted the effects of rising water temperatures on corals in the North Atlantic Ocean, including the Florida Keys, the Bahamas and the Caribbean.
Based on a number of scenarios for rising temperatures, scientists have suggested what the coral ecosystems can expect in the coming decades.
The object for modeling was coral metapopulations, that is, many interacting, but separate populations. It was their stability that scientists evaluated.
According to the researchers, the connection between the accumulations of polyps is primarily provided by sexual reproduction and the dispersal of planktonic larvae, so they should be taken into account in modeling.
The basis for the new article was a special approach – Connectivity Modeling System, that is, modeling based on connectivity analysis. The required open source software was previously developed by one of the authors.
The worst-case scenario assumes the disappearance of all coral reefs within the current range. “According to the predictions of the model, an increase in ocean temperature will impede the migration of dispersing coral larvae and their ability to replace reefs that have become bleached (that is, they have lost their photosynthetic symbionts.
This is not to say that this model sounds like a death sentence for coral reefs, but it’s still a wake-up call,” says Holstein.
Despite their own complex forecasts, the authors do not fall into pessimism. They note that we still have the ability to make a difference by protecting surviving reefs, restoring damaged ones, and reducing carbon dioxide emissions.
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