Inside and Out

Green sea urchins
Photo: R. Wollocombe

Ocean acidification has been studied in relation to marine animals with calcium carbonate shells. Oysters, sea butterflies, shrimp – all are affected by acidification when their outer shells don’t develop properly.

According to this article, ocean acidification has increased by 25-30% since the beginning of the Industrial Revolution.

A new study published in Nature Climate Change looks at a different key species in kelp forests in temperate and subpolar oceans, green sea urchins. But it’s not their shells that are at risk.

In a first demonstration that ocean CO2 levels can affect the digestion of a marine creature, German and Swedish researchers showed that the larval stage of green sea urchins (Strongylocentrotus droebachiensis) have difficulty digesting in water with higher levels of acidity.

Green sea urchin Source: OhDeer

Green sea urchin
Source: OhDeer

The sea urchins compensate by eating 11-33% more, but if additional food is unavailable, their growth, fertility and survival can be compromised.

So while some studies have shown that ocean acidification varying levels of impact on different marine life.

Unlike the effects on oysters and sea butterflies, increased acidity (up to a given threshold) has less of an effect on certain marine animals with substantial shell coverings – like the temperate sea urchin.

Unfortunately, being protected by a thick shell may not be all that’s necessary to survive in an acidified ocean.

Green sea urchin endoskeleton Photo: galewhale/Project Noah

Green sea urchin endoskeleton
Photo: galewhale/Project Noah

Something Rich and Strange

Antarctic southern Minke whale fallPhoto: Natural Environment Research Council

Antarctic southern Minke whale fall
Photo: Natural Environment Research Council

Scientists exploring an undersea crater near the South Sandwich Islands have come across a whale skeleton, that of a southern Minke whale, a mile beneath the ocean’s surface near Antarctica. Finding a ‘whale fall’ is a rare enough occurrence, since whales sink to the ocean floor when they die (beached whales account for only an estimated 3% of whale deaths). For humans, finding a whale fall requires a large amount of undersea equipment and even more serendipity.

Whale carcasses provide a bounteous feast for other sea creatures wherever they land. From the quick and lithe scavengers, like sharks and hagfish, to the meticulous crabs,  to slower mollusks and crustaceans, to the thorough bacteria and bivalves, a whale can provide nutrition for up to a century. There are up to 30 species that are exclusive to whale falls. The newly-found Antarctic whale fall alone has revealed at least nine new species of tiny deep-sea creatures.

Where have humans found one of the largest whale falls? In Chile’s Atacama Desert, during the course of a 2011 highway expansion project. More than a kilometer from the ocean, road workers came across a mass graveyard with more than 75 fossilized whales and other creatures, including a tusked dolphin and an aquatic sloth. The site has been dated at between 2-7 million years old. Included among the many intact whale skeletons that were located directly next to one another was a single family group resting together, a sort of aquatic Pompeii scene.

It might be that sea scavengers are so plentiful that a body is quickly discovered, or that the detecting organs of whale fall species are extremely sensitive. Still, I found myself wondering why, if whale fall scavengers seem to be able to locate a feast, we have to simply stumble across them, either by sea or by land. There’s a fascination with what happens to the world’s largest animals when they die. Their fate after death remains almost as mysterious as their movements during life.

Atacama desert site Photo: Danielle Pereira/Flickr

Atacama desert  Photo: Danielle Pereira/Flickr


Original study published in Deep Sea Research Part IITopical Studies in Oceanography on The discovery of a natural whale fall in the Antarctic deep sea, by

  • D.J. Amon,
  • A.G. Glover,
  • H.Wiklund,
  • L. Marsh,
  • K. Linse,
  • A.D. Rogers,
  • J.T. Copley

Mother Nature Network article: Mysterious mass whale graveyard unearthed in the Chilean desert