Find­ing Nemo may be harder be­cause of global warm­ing

USA TODAY International Edition - - NEWS - Doyle Rice @us­ato­day­weather USA TO­DAY

The clown­fish, made world­fa­mous by lov­able Nemo, could be harder to find be­cause of global warm­ing, ac­cord­ing to a study pub­lished Tues­day.

While coral bleach­ing is a well­known re­sult of un­usu­ally warm ocean wa­ter, it turns out that sea anemones also can be bleached, which in turn af­fects the clown­fish that live in and around the anemones.

In fact, the fish show much higher stress lev­els and a dra­matic de­crease in off­spring — as much as 73% less — when their home sea anemones are bleached in warmer wa­ters, the study found.

“While no ef­fects on adult anemone sur­vival were ob­served, the ef­fects of bleach­ing on re­pro­duc­tion and pop­u­la­tion de­mog­ra­phy were likely even greater than demon­strated here,” the study’s lead au­thor, Suzanne Mills of the French univer­sity Ecole Pra­tique des Hautes Etudes, told the Daily Mail.

She added that the find­ing is alarm­ing, since man-made stres­sors and the rate of change in en­vi­ron­men­tal con­di­tions are ex­pected to mul­ti­ply in the com­ing decades, “with bleach­ing and habi­tat degra­da­tion be­com­ing more fre­quent.”

Us­ing the nat­u­ral El Niño warm­ing phe­nom­e­non as a stand-in for what fu­ture man­made warm­ing might bring, re­searchers vis­ited 13 pairs of clown­fish and their host anemones in the coral reefs near Moorea Is­land in French Poly­ne­sia from Oc­to­ber 2015 to De­cem­ber 2016.

Sci­en­tists cap­i­tal­ized on that op­por­tu­nity to mea­sure the stress and re­pro­duc­tion of the fish be­fore, dur­ing and af­ter their host anemone un­der­went bleach­ing.

It turned out that the clown­fish cou­ples from bleached anemones spawned far less fre­quently and pro­duced far fewer vi­able young than those that were not bleached.

This study, which ap­peared in the peer-re­viewed Bri­tish journal Na­ture Com­mu­ni­ca­tions, un­der­scores the nu­mer­ous cas­cad­ing ef­fects of warm­ing oceans on the res­i­dents of coral reefs.

The clown­fish are not an iso­lated case: In all, 12% of the coastal fish in French Poly­ne­sia de­pend on anemones or corals to feed or to pro­vide pro­tec­tion from preda­tors.

In cases of pro­longed bleach­ing, such as that of the Aus­tralian Great Bar­rier Reef in 2016 and 2017, the re­newal of all of these pop­u­la­tions could be af­fected, and with them the sta­bil­ity of the ecosys­tems, the sci­en­tists said.


Clown­fish snug­gle in anemones in French Poly­ne­sia. The golden color of the anemones is be­cause of the mi­croal­gae present in their ten­ta­cles.

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