Also rivers and lakes acidify dangerous not only in oceans but also in inland waters increases the concentration of carbon dioxide. Scientists warn that this can be dangerous for many fish species. You change their behavior. Salmon hatch in rivers from the eggs - and later swim in the sea. Already in their first weeks of life can change their behavior significantly too high pH. The acidification of the oceans is explored in detail by researchers. It could be problematic for many fish and shellfish species, if the pH of sea water continues to fall, according to the unanimous opinion. Now, however, warn biologists warning that an important ecosystem has been almost completely forgotten: It is not only the oceans, but also the lakes and rivers acidify. While doing fresh for only about one percent of global surface water, but live in it, so the Canadian researchers, almost 40 percent of all fish species.
By acidification of freshwater is the development of smolt for example, could be affected. The increased carbon dioxide concentrations in the river water change, growth and behavior of juveniles.
The researchers led by Michelle Ou from the University of British Columbia in Vancouver examined in their study, the effects of it on humpback salmon (Oncorhynchus gorbuscha). These live in the sea and migrate only to spawn in freshwater. The juveniles spend their first months of life near their place of birth and feed on the body's yolk sac. If this is empty, it is time to swim in the sea for the little fish. Switching from fresh to salt water is a critical moment for the young fish.
Young salmon in the laboratory
For their study, researchers pink salmon breeding, they had fished out of the Campbell River (Vancouver Iceland) set out in the laboratory for a period ten weeks different atmospheric carbon dioxide concentrations. So some animals grew up under conditions that correspond to the current carbon dioxide concentrations increased under other, projections of future carbon dioxide concentrations. Then the researchers exposed the animals in seawater, also at different atmospheric carbon dioxide concentrations.
A dead frog floating in Lake Titicaca.
The researchers observed the effects on growth, metabolism and behavior of the fish. "Our results suggest that an increase of carbon dioxide effects on growth, the sense of smell and the flight behavior of the salmon will have" the researchers write.
The latter could be a danger to the fish: When a fish prey is, it is usually a messenger from which to warn his cousins. The humpback salmon but which had grown under elevated carbon dioxide concentration, fled immediately after they had perceived the messenger. They stayed longer in the danger zone than fish in the control group.
Inland waters are taken into account
"What have found Ou and her colleagues, should be a warning that we need to consider the potential impact of carbon dioxide induced freshwater acidification on fish, especially those species that even as a very young animals migrate into the sea", the Australian scientist Philip Munday writes in Commenting on the study. "Some of these fish may be more sensitive to rising levels of carbon dioxide than we previously thought."
There are animals in which one really wonders why only nature is so wasteful. Phyllodesmium acanthorhinum is a, a worm that lives in the sea off Japan. Tiny 17 millimeters it is large and shimmers in bright colors in front of him. The people living in large populations humpback salmon have the advantage that they are highly fertile and their life cycle completed in just two years. Thus there is a high genetic variability that may allow them to adapt to rising carbon dioxide levels.
Katrin Premke from the Leibniz Institute of Freshwater Ecology and Inland Fisheries (IGB) confirmed an increase in carbon dioxide concentration in German rivers. Currently being studied even more salt water, she explains, among others, the size of the oceans and the associated visibility. "Straight from the deep sea is so little known, such as by any other ecosystem on earth. This naturally arouses curiosity again," she says. At the same time the policy would, however, respond to the findings of science and take account of inland waters in their climate models.