Ocean acidification may create an impact similar to extinction onmarine ecosystems, according to a study released today by theUniversity of California, Davis.
The study, published online in the journal Proceedings of theNational Academy of Sciences, found that ocean acidification candegrade not only individual species, as past studies have shown, butentire ecosystems. This results in a homogenized marine community,dominated by fewer plants and animals.
"The background, low-grade stress caused by ocean acidification cancause a whole shift in the ecosystem so that everything is dominatedby the same plants, which tend to be turf algae," said lead authorKristy Kroeker, a postdoctoral researcher at the Bodega MarineLaboratory at UC Davis.
"In most ecosystems, there are lots of different colorful patches ofplants and animals -- of algae, of sponges, of anemones," Kroekersaid. "With ocean acidification, you lose that patchiness. We call ita loss of functional diversity; everything looks the same."
In the waters surrounding Castello Aragonese, a 14th century castleoff the coast of Italy, volcanic vents naturally release bubbles ofcarbon dioxide gas, creating different levels of acidity among themarine-animal and plant communities there. These gradients of aciditygave the scientists a glimpse of what a future marked by increasinglyacidic ocean waters could look like, and how the creatures and plantsliving in those environments may react to it.
The researchers selected three reef zones--of low, high and extremelyhigh acidity, representing world ocean conditions for the presentday, 2100 and 2500, respectively. Then they removed animals andvegetation from the rocks there. Every few months for three years,Kroeker dived to the study plots to photograph them and watch how theplots in each zone recovered.
By examining how recovery differed among zones, the study found thatacidic water reduced the number and variety of species. In thenon-acidic plots, many different plants and animals, including turfalgae, would colonize and grow. Calcareous species, such as seaurchins and snails, would then eat them, allowing for variety throughtime.
However, in both the high and extremely high acidic plots, fleshyturf algae increased steadily and overtook the zones, as the urchinsand other grazers were either not present or did not graze on thealgae while in these zones.
Calcareous grazers play key roles in maintaining the balance withinmarine ecosystems. They are also considered among the most vulnerablespecies to ocean acidification.
"Our research is showing that if the role of these grazers changeswith ocean acidification, you might expect to see cascading effectsof the whole ecosystem," Kroeker said. "If the pattern holds forother calcareous grazers, this has implications for other ecosystems,as well."
Source: University of California - Davis