Sea Urchins Adapting to Increased Oceanic Acidification

Sea urchins have already started adapting to the increasing sea-acidification, according to a new study.

Ocean acidification is an unfortunate consequence of the industrial revolution. Burning of fossil fuels has resulted in billions of tons of carbon dioxide being released in the environment. This has lead to a drop in the sea-surface pH. The increase of carbonic acid in the oceans inhibits growth and development of marine life. However, according to a new study, certain creatures have started adapting to the changes in the oceans.

Sea urchins can be found around the world and are considered a keystone species - meaning that their population directly affects many other organisms that live in the oceans. Sea urchins are spherical in shape and have prickly barbs all over them. There are about 950 species of sea urchins in the world.

"What we want to know is, given that this is a process that happens over time, can marine animals adapt? Could evolution come to the rescue?" said Morgan Kelly, from UC Santa Barbara's Department of Ecology, Evolution and Marine Biology.

Rising oceanic acidification can inhibit growth of sea-urchins and other organisms like them that require calcium to maintain their exoskeleton. Increase of carbonic acid in water can lead to low levels of calcium in water. This can lead to sea-urchins having short, thin spines and other creatures being really short and having thin shells. "It gives them osteoporosis," added Kelly.

For the study, researchers exposed sea-urchins to various acidity levels. Currently, carbon dioxide levels are at CO2 levels top off at about 400 parts per million and are expected to rise up to 700 parts per million by the end of this century. "We exposed them (sea urchins) to 1,100 parts per million of carbon dioxide," Kelly said in a news release.

The region of California has fluctuating oceanic acidity due to cold wave upwelling, which brings in more acidic waters.

The sea urchins used in the study were taken from two locations near the California coast - one that had greater upwelling and another that had lower upwelling.

The males from one site were crossed with females from the other site. Their larvae were then bred in conditions that mimicked oceanic acidity of the future.

Researchers found that some larvae had reduced size, showing the detrimental effects of high oceanic acidity on the organisms. However, few larvae grew to average adult size despite being in acidic water.

Size is important since it directly relates to the organisms' feeding abilities and it's survivability in the oceans. Researchers say that in time, larger sea urchins with greater tolerance to acidic oceans will produce more larvae and outnumber the weaker sea urchins.

"This is what allows us to predict that this species will evolve increased tolerance -- as CO2 rises, urchins that have greater tolerance will have a better chance of survival, and they will pass on their greater tolerance to their offspring," said Kelly.

Their ability to survive can also be good news for creatures that feed on them, researchers added.

The study is published in the journal Global Change Biology.