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Sci­en­tists seek sea urchin’s secret to sur­viv­ing ocean acidification

pub­lished 15 April 2013 | mod­i­fied 19 March 2014

Sea urchin purpleOcean research reveals rapid evo­lu­tion­ary adap­ta­tions to a chang­ing cli­mate. Genetic vari­a­tion is the key to this abil­ity to deal with higher acid­ity.

Stan­ford sci­en­tists have dis­cov­ered that some pur­ple sea urchins liv­ing along the coast of Cal­i­for­nia and Ore­gon have the sur­pris­ing abil­ity to rapidly evolve in acidic ocean water — a capac­ity that may come in handy as cli­mate change increases ocean acid­ity. This capac­ity depends on high lev­els of genetic vari­a­tion that allow urchins’ healthy growth in water with high car­bon diox­ide lev­els.

The study, co-​authored by Stephen Palumbi, a senior fel­low at the Stan­ford Woods Insti­tute for the Envi­ron­ment and direc­tor of Stanford’s Hop­kins Marine Sta­tion, revealspre­vi­ously unknown adap­tive vari­a­tions that could help some marine species sur­vive in future acid­i­fied seas.

It’s like bet hedg­ing. Bet­ting on mul­ti­ple teams in the NCAA play­offs gives you a bet­ter chance of win­ning. A par­ent with genetic vari­a­tion for sur­vival in dif­fer­ent con­di­tions makes off­spring that can thrive in dif­fer­ent envi­ron­ments. In an uncer­tain world, it’s a way to have a stake in the Final Four.
(Stephen Palumbi)

Increas­ing acid­i­fi­ca­tion is a wor­ri­some ques­tion for the bil­lionpeo­ple who depend on the ocean for their sus­te­nance and liveli­hoods. Which sea crea­tures will sur­vive in waters that have had their chem­istry altered by global car­bon diox­ide emis­sions from fos­sil fuels? The authors, includ­ing col­lab­o­ra­tors at the Uni­ver­sity of Cal­i­for­nia Davis’ Bodega Marine Lab, spec­u­late in a research paper pub­lished on 8 April in the Pro­ceed­ings of the National Acad­emy of Sci­encesthat other marine species that have long dealt with envi­ron­men­tal stresses may have a sim­i­lar adap­tive capacity.

If true, these capa­bil­i­ties could pro­vide impor­tant clues about how to main­tain robust marine pop­u­la­tions amid the effects of acid­i­fi­ca­tion, cli­mate change, over­fish­ing and other human impacts.

Sci­en­tists have known for decades that high car­bon diox­ide emis­sions from fos­sil fuels are increas­ing the lev­els of car­bonic acid in the world’s oceans, lead­ing to increased acid­ity. Hun­dreds of stud­ies have shown that acid­i­fi­ca­tion at lev­els expected by the year 2100 can harm ocean life. But lit­tle is known about marine species’ capac­ity to adapt evo­lu­tion­ar­ily to this con­di­tion. The del­i­cate embryos of marine species are espe­cially sus­cep­ti­ble. The West Coast oys­ter farm indus­try nearly col­lapsed in 2007 because of oys­ter lar­vae sen­si­tiv­ity to increased acid­i­fi­ca­tion of coastal waters.

The study exam­ined how pur­ple sea urchins — crea­tures with the most well-​studied genome of any marine species — react to the acid­i­fi­ca­tion lev­els pre­dicted for 2100.

Why are sea urchin babies like ham­burg­ers?:

Sea urchin babies and ham­burg­ers? See how sci­en­tists use genet­ics to under­stand how sea urchins are able to with­stand increas­ingly acidic ocean water.

The researchers raised lar­vae in ocean water with either low or high car­bon diox­ide con­tent. They sam­pled the lar­vae at early and later stages in life and then used new DNA-​sequencing and ana­lyt­i­cal tools to deter­mine which ele­ments of the urchins’ genetic makeup changed through time in these con­di­tions. By look­ing at the func­tion of each gene that changed, researchers were able to pin­point which types of genes were crit­i­cal for sur­vival under future con­di­tions.

The high CO2 lar­vae showed almost no neg­a­tive effects, and that was a sur­prise,” said Melissa Pespeni, the study’s lead author and a for­mer Stan­ford post­doc­toral fel­low. “They didn’t suf­fer because among them were some indi­vid­u­als with the right genes to be able to grow well in those harsh con­di­tions.”

Pur­ple sea urchins, like other West Coast marine species, nor­mally live in cold water that wells up along the coast, bring­ing sea­son­ally higher CO2 lev­els. The study’s results sug­gest that this long-​term envi­ron­men­tal mosaic has led to the evo­lu­tion of genetic vari­a­tions enabling pur­ple sea urchins to reg­u­late their inter­nal pH level in the face of ele­vated car­bon diox­ide.

There are hun­dreds of West Coast species that sim­i­larly evolved in these con­di­tions. Maybe some of these have the genetic tools to resist acid­i­fi­ca­tion, too,” Palumbi said. “We need to learn why some species are more sen­si­tive than oth­ers.”

(Source: Stan­ford Uni­ver­sity press release, 08.04.2013)

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