Coral reefs may have less time than expected due to ocean acidification and bleaching

Picture this: you are visiting a tropical paradise known for their brightly colored coral reefs, unique aquatic life, and crystal-clear water. After diving into the water, the only emotion going through your head is a sense of feeling underwhelmed. The coral is all but colorful, the white ghostly skeletons of the coral covering the ocean floor.

This devastating change is called bleaching which is caused by ocean acidification.

Ocean acidification is the decrease in the pH of the ocean due to the absorption of carbon dioxide from the atmosphere. With the increasing carbon dioxide levels in the atmosphere through the continuously expanding emissions of fossil fuels, it is predicted that about 90% of all coral reef locations are going to experience severe bleaching by the year 2055. Scientists believe that dire actions need to be taken after receiving the results from this study, showing a bleak future for the coral reefs.

The bleaching of the coral reefs is caused by various factors, the main one being the increasing temperature of the ocean. As carbon dioxide is released into the atmosphere through human activities including car emissions and fossil fuels, the heat is trapped inside the ozone layer which in turn heats the oceans. It is predicted that nearly 30% of all carbon dioxide emissions since the industrial revolution have been absorbed by the earth’s oceans. These levels of CO2 far exceed the levels that scientists had predicted as the “worst case scenario” which should be worrying even if you don’t have a trip planned to the Great Barrier Reef.

One of the main concerns for scientists is the declining levels of aragonite. Aragonite can be considered the cells of the reefs, as it is the building block for coral reef habitat. It is a mineral that strengthens the coral reefs and is often used to measure ocean acidification due to the fact that it is a measure of carbonate ion concentrations. Declining levels of aragonite mean a decline in calcification rates of coral or simply coral reef growth.

Factors such as light, temperature, and nutrients all influence the calcification rates of coral reefs just as those variables have an effect on familiar plants on land. Scientists accurately predicted changes in calcification by using the relationship of the declining aragonite and the levels of the calcification. The results that they received were worrying no doubt.

To accurately calculate the levels of aragonite and the sea surface temperature, data was collected monthly for measures of sea surface temperature, the surface pressure of carbon dioxide, pH, and salinity to produce the projections. The research includes the effect of Sea Surface Temperature (SST) and salinity on the coral reefs. They used the pH and levels of carbon dioxide to calculate the other parts of the carbonate system and the aragonite.

After the data was collected and examined, many results and predictions were created. Nearly 90% of all reef locations are projected to experience annual severe bleaching prior to 2055. Tests indicate that many reefs are close or already at net erosion so small declines in calcification could tip reefs off the edge.

When severe bleaching occurs two or three times per decade it is predicted to result in great reductions in coral growth possibly greater than the declines in the calcifications. This data portrays the significance of the bleaching, and how many reefs it will actually affect.

While doing the tests, the coral reefs around the world were divided into six different latitudinal zones. This shows that the changes in aragonite and temperatures will not be uniform across the globe. The reefs at higher latitudes are expected to experience bleaching later than those closer to the equator by 10 to 15 years. Because of the fact that the higher latitude reefs are expected to last longer, they are predicted to have a greater decline of aragonite as well as more time to be exposed to acidification.

Another factor differentiating the high and low latitude reefs is the occurrence of tropical storms and cyclones. With the storms arising in the higher latitude areas, the coral will have a harder time surviving the weather because of the declining levels of aragonite.

Although some reefs have a better chance at surviving than others, the data shows that there is a bleak future for all coral reefs. Both ocean acidification and the bleaching caused by increasing sea temperatures reduce reef growth and resilience. With 90% of all reefs projected to experience severe bleaching by 2055, immediate action needs to be taken to have any hope for the future of the coral reefs.

The research was conducted in locations that had a high density of coral reefs, chosen through a research projection to receive the most accurate representation of all coral reefs.

Claire Kindsvater, 9 February 2019. Blog.

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