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

Larger Than Life

Limacina Helica IV Artist/Photo: Kavanagh/Bessler

Limacina Helicina IV
Artist/Photo: Kavanagh/Bessler

When one thinks of marine life, especially when it comes to endangered marine life, the mind naturally turns to the poster children of conservation: polar bears, whales, dolphins. The big guys. Maybe some of us think of our favorite fish – tuna, for example, or salmon.

Not many spare a thought for the tiny shelled pteropod Limacina. But Limacina makes up in pure grace what it lacks in cute eyes, haunting songs, bottle-nosed grins or delectability.

Limacina helicina  Photo: Alexander Semenov

Limacina helicina
Photo: Alexander Semenov

Known as sea butterflies, they make up a giant link in the food chain between plankton and larger animals. Tiny as they are, they are also a key part of the global carbonate cycle – their shells make up an estimated 12% of the carbonate flux that determines ocean acidity and helps stabilize carbon levels in the atmosphere.

A report, due to be presented at Conference of the Parties (COP 19) to the 1992 United Nations Framework Convention on Climate Change (UNFCCC) in Warsaw next week states with high confidence that ocean acidification is increasing due to carbon dioxide emissions, and that this acidification will have major ramifications.

Limacina Helica V Artist/Photo: Kavanagh/Bessler

Limacina Helicina V
Artist/Photo: Kavanagh/Bessler

According to this article, “the world needs to prepare for major losses of ecosystem services” and all the benefits to human life and activity which those services provide, from food and clean air to reef protection and economic livelihoods.

The sea butterflies, seen here in sculptures by Corneila Kubler Kavanagh, are losing their shells, which are dissolving in acidic waters. Working together with ocean acidification researcher Gareth Lawson, Kavanagh created aluminium visions of Limacina that magnify the fragile creatures by 400 times their natural size of 1 cm (0.4″).

Maybe that size, combined with the UNFCC meeting, is just about big enough to focus attention on the challenge of ocean acidification.

Limacina Helica II Artist/Photo: Kavanagh/Bessler

Limacina Helicina II
Artist/Photo: Kavanagh/Bessler

Krill Gratitude

Via: OneYearNovel

Massive ocean krill swarms – hundreds of millions of tons of them – are a keystone of one of the great planetary life cycles.

A new Australian study published in the journal Nature Climate Change called Risk maps for Antarctic krill under projected Southern Ocean acidification, looks at the threshold at which krill – specifically, their eggs – no longer survive acidification levels caused by CO2 emissions. Krill eggs, as it turns out, are more resistant that some other calcifying creatures such as oysters and sea butterflies. Like the sea butterfly, krill shells are critical to the global carbonate cycle, part of which is the deep-sea calcium carbonate sediment formed by the shells of krill – these shells bind carbon and carry it to depths of the ocean.

But even krill have their limits and those are rapidly approaching.

The impact of higher acidification comes with an increase in fishing – krill are industrially harvested for food products, health supplements, and as feed for fish farming.

Researchers for the study estimate that by 2300, unless drastic measures are undertaken to reduce carbon emissions, the world’s krill might be gone. But they state these estimates might be conservative – a tipping point could be reached earlier.

One proposal underway is the creation of a protected Antarctic zone.

What would really help is the same old answer: a move away from a carbon-based fuel economy.

Krill (watercolor) Source: Wikipedia

Krill (watercolor)
Source: Wikipedia


The Guardian articleAntarctic krill face unhappy Hollywood ending if fossil fuel emissions keep rising by Graham Readfearn