Algal Overpopulation Linked to Coral Reef Death


Coral Reefs are considered to be one of the most diverse ecosystems on earth. Supporting a large variety of marine life ranging from cnidarians and mollusks to fish and echinoderms, the release of nutrients from this system is carefully balanced for the sustenance of all it’s forms. However, the overpopulation of even one of it’s members, especially algae can ruin the delicate balance of the food web it forms and result in the death of the reef.

(Read more on how environmental changes and humans are affecting the coral reefs)

Coral reefs across the world are dying due to ‘Microbialization’  (Photo credit- Brocken Inaglory)

According to the recent findings made by researchers at San Diego State University, over fishing near areas of reefs around the world have resulted in an uncontrollable increase in algal population resulting in widespread reef loss across marine ecosystems.

This study, published in the journal Nature Microbiology, reveals that a decline in the number of fish in these water bodies due to human activities has reduced the chances of Reef Algae from being preyed upon by their primary scavengers. This, in turn, has resulted in an explosion of fleshy algae that produces profuse amount of Dissolved Organic Carbon or DOC.

While the Algae itself does not promote the slow deterioration of the reef’s health, the excess DOC that it produces helps in nutritionally supporting a large variety of microbes in the reef, including potential pathogens, which consequently deprive it of the energy it requires to support all of its varied organisms.

“It no longer supports the variety of reef organisms which make up a healthy system anymore.” says Dr. Andreas F. Haas, the lead author of this study.

In order to test their theory, Dr. Haas and co-author Mohammed F.M Fairoz from Sri Lanka’s Ocean University along with their team collected and tested 400 water samples from 60 water bodies for corroboration of ‘Microbialization’ as they called it. These samples  were taken from the Atlantic, Pacific and Indian Oceans and were thoroughly examined deleterious microbes.

Through the course of their research, these group of scientists concluded that reefs with low algal cover exhibited higher DOC and vice versa. This can be explained by the fact that reefs with more algae can harbor a larger population of microbes than one with lesser algae. These microbes being voracious in nature, deprive other reef dependent organisms of the organic material they require for survival.

This hypothesis was proved true in all the sixty samples that were collected and through the use of meta-genomics, it was proved that over population of algae make reefs less efficient recyclers of carbon.

Since anthropogenic activities like over fishing and eutrophication are the root causes of algal overpopulation, strict regulations on the same can help impede, in a small way, worldwide Reef death.

To read the original article, click here.