Mari­ne zoo­plank­ton more resistant against aci­di­fi­ca­ti­on of oce­an water than belie­ved?

The decre­asing pH-value of oce­an water or in other words the incre­asing aci­di­fi­ca­ti­on of the glo­bal seas is among­st tho­se con­se­quen­ces of glo­bal chan­ce that have, so far, recei­ved rela­tively litt­le public atten­ti­on, but are a major worry for sci­en­tists. The world’s oce­ans are important CO2 sinks, which means they absorb mas­si­ve amounts of CO2 from the atmo­sphe­re. The more CO2 in the atmo­sphe­re, the more will be stored in oce­an water, which is accor­din­gly beco­ming more and more aci­dic.

It is feared as a con­se­quence that mari­ne crea­tures, espe­ci­al­ly tho­se plank­ton spe­ci­es that use car­bo­na­te to build up a shell, will suf­fer sever­ely. This includes many spe­ci­es from sin­gle-cel­led plank­ton to mari­ne snails. The one thing that many of them have in com­mon is that they are very important for the mari­ne food web. Should the pH-value of the water fall below thres­holds that indi­vi­du­al spe­ci­es can tole­ra­te, then links of the food chain may break. The extre­me con­se­quence would be a col­laps of regio­nal food chains and eco­sys­tems. Also sea­bird colo­nies and ani­mals inclu­ding wha­les, polar bears and seals depend com­ple­te­ly on the mari­ne food chain for their sur­vi­val. The­re are signi­fi­cant indi­ca­ti­ons that such fears have to be taken serious­ly.

But the­re is now also a sci­en­ti­fic obser­va­ti­on that the mari­ne eco­sys­tem in Spits­ber­gen may be more resistant against aci­di­fi­ca­ti­on than assu­med so far. In Kongsfjord, sci­en­tists have car­ri­ed out a “meco­c­osm expe­rie­ment”: nine instal­la­ti­ons in the fjord whe­re CO2-enri­ched sea­wa­ter was added to the natu­ral envi­ron­ment to stu­dy the con­se­quen­ces. The result is sur­pri­sing: the sci­en­tists “found almost no direct effects of OA on micro­zoo­plank­ton com­po­si­ti­on and diver­si­ty …” This gives reason to hope that arc­tic eco­sys­tems may be more resistant against fal­ling pH-levels of oce­an water than belie­ved so far.

The­re is, howe­ver, no cer­tain­ty yet. The stu­dy covers only one fjord over a limi­t­ed peri­od of time. Obser­va­tions sup­port­ing dif­fe­rent results are still the­re and valid. As always, one of the con­clu­si­ons is: fur­ther rese­arch is nee­ded …

Source: CO2 Sci­ence

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