Big­ger Pic­ture

From its first dis­cov­ery 30 years ago in P.E.I., am­nesic shell­fish poi­son­ing has be­come a baf­fling global scourge. A new study says ocean warm­ing is the cause.

Canadian Wildlife - - FEATURES - By Alanna Mitchell

From its first dis­cov­ery 30 years ago in P.E.I., am­nesic shell­fish poi­son­ing has be­come a baf­fling global scourge. A new study says ocean warm­ing is the cause

The odd symp­toms started in Prince Ed­ward Is­land on Novem­ber 11, 1987, and con­tin­ued show­ing up for a month: vom­it­ing, di­ar­rhea, mem­ory loss and con­fu­sion, dis­ori­en­ta­tion, seizures, coma. By the time the out­break was over, 153 peo­ple had fallen ill, and three peo­ple were dead.

Quickly, in­ves­ti­ga­tors dis­cov­ered that all the vic­tims had feasted on blue mus­sels farmed off the is­land’s east coast. Still, they were baf­fled: the ill­ness didn’t match the symp­toms of any shell­fish poi­son known any­where in the world. A task force ap­pointed by the fed­eral gov­ern­ment swiftly sprang into ac­tion. Just five days later, it iden­ti­fied a po­tent neu­ro­toxin called domoic acid.

It was the first time it had been found in shell­fish and the first re­port of ill­ness in those who ate it. How had it got­ten into the mus­sels? The in­ves­ti­ga­tors sus­pected that the mus­sels, too, had eaten some­thing toxic. So they got out their plank­ton tow-nets and hit the wa­ter. Their find­ings were shock­ing: the toxin was be­ing pro­duced by a type of di­atom, a mi­cro­scopic marine plant with a hard sil­ica shell. There is no an­ti­dote. Its poi­son is un­af­fected by cook­ing. They dubbed its ef­fects am­nesic shell­fish poi­son­ing.

Today, 30 years later, the toxic al­gae (in the genus Pseudo-nitzschia) have been found all over the world. In North Amer­ica, fish­ery clo­sures to avoid domoic acid poi­son­ing have be­come rou­tine. In March, high domoic acid lev­els closed com­mer­cial shell­fish­ing off Bri­tish Columbia and Rhode Is­land. Cal­i­for­nia has had clo­sures nearly every year since 2000.

Domoic acid has been found to af­fect many species, mov­ing up the food chain from the crea­tures that eat the toxic plank­ton to the suc­ces­sive crea­tures that eat them. Among the vic­tims: ra­zor clams, Dun­geness crabs, lob­sters, sar­dines, an­chovies, mus­sels, fin­fish, brown pel­i­cans and cor­morants. Mass die-offs of sea lions and north­ern fur seals in Cal­i­for­nia are tied to the toxin. Ne­crop­sies show that the hip­pocam­pus sec­tions of the mam­mals’ brains, used for nav­i­ga­tion and mem­ory, have le­sions, much as they have in hu­mans who have Alzheimer’s disease. Fur­ther, a re­cent pa­per sug­gests domoic acid may be re­spon­si­ble for mass strand­ings of long-finned pilot whales in Tas­ma­nia that have lost their abil­ity to find their way. And a ret­ro­spec­tive study in 2012 proved that Al­fred Hitchcock’s 1963 hor­ror movie The Birds was inspired by an in­ci­dent near his home two years ear­lier when masses of sooty shear­wa­ter birds, driven crazy by domoic acid, at­tacked the shores in North Mon­terey Bay, Cal­i­for­nia, vom­it­ing an­chovies.

De­spite all the im­pli­ca­tions for public and wildlife health, sci­en­tists have strug­gled to find out pre­cisely which en­vi­ron­men­tal con­di­tions make the al­gae ap­pear. Now, a study led by Mor­gaine Mck­ibben of Ore­gon State Univer­sity that was re­ported on in the Jan­uary 2017 edi­tion of the Pro­ceed­ings of the Na­tional Academy of Sci­ences has found the an­swer. They dis­cov­ered it by div­ing back through the records of out­breaks (domoic acid has been mon­i­tored among shell­fish along the west coast of the U.S. since 1991) and match­ing them against ocean con­di­tions.

The anal­y­sis re­vealed for the first time that out­breaks of domoic acid in shell­fish along the west coast of North Amer­ica were re­lated to wa­ter tem­per­a­ture, pos­si­bly lead­ing to changes in cel­lu­lar and meta­bolic pro­cesses in the plank­ton. The warmer the wa­ter, the more likely the toxin is to ap­pear at harm­ful lev­els and the more dan­ger­ous and wide­spread the poi­son be­comes. Among the phe­nom­ena that af­fect the Pa­cific Ocean along the west coast of North Amer­ica are two re­cur­ring ones: the Pa­cific Decadal Os­cil­la­tion and the El Niño South­ern Os­cil­la­tion. From 2013 to 2015, there was an ad­di­tional phe­nom­e­non known as a North­east Pa­cific warm anom­aly. Each of th­ese pro­duce huge shifts in wa­ter tem­per­a­ture, ocean cur­rents and the dy­nam­ics of marine food webs that can last for months or even years. The weird warm­ing through the North­east Pa­cific in 2015 led to an un­prece­dented, record-set­ting episode of domoic acid poi­son­ing in marine life.

The larger prob­lem is the ocean is on track to get much warmer. We have burned so many fos­sil fu­els, load­ing the at­mos­phere with so much heat-trap­ping car­bon-based gas, that the ocean is soak­ing up some of the ex­tra heat. The un­avoid­able im­pli­ca­tion is that, over time, domoic acid poi­son­ing will be­come yet more com­mon and per­sis­tent, rip­pling re­morse­lessly through the ecosys­tem.

This is one of those un­fore­seen fall­outs from cli­mate change. A warmer world trig­gers a tiny change in the in­ner work­ings of com­mon al­gae, and as a re­sult vast swathes of sea life are at risk from a poi­son un­known just three decades ago. It makes you won­der: what else can we ex­pect?a


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