Anthropogenic noise inhibits the ability of coastal crabs to color masking and makes them slower to respond to the threat. The main source of such noise in the sea are the propellers of ships, with loud natural noise was virtually harmless. The results of the experiments published in Current Biology.
With the development of navigation in the ocean is gradually increasing and the level of human generated noise. According to estimates, since the mid-twentieth century it has been increasing by about three decibels per decade and negative impact on marine animals. We already know that it causes concern for humpback whales, the scientists also fear for the populations of mammals in the Arctic. Research in this area focused mainly on vertebrates, but the effects of noise on arthropods and molluscs potentially could be no less.
The European shore crab is able to change the color of your armor depending on the environment, like octopuses and chameleons. However, in contrast, change the color it takes not seconds, but hours and weeks, but this is sufficient for protection from predators while living in a relatively homogeneous landscape.
Emily Carter (Emily Carter) and her colleagues from Exeter University found that this ability to adaptive camouflage is suppressed by the noise of boat engines. Scientists selected a group of dark crabs, divided them into three groups and placed on artificial bottom in white, but in different conditions. In the pool, one of the three groups were played the recorded sound of propellers, and the other two through the speakers reproduce the natural backdrop of the sea, but for one of them, he was amplified to the volume of the drone ships. After eight weeks, the result was obvious: anthropogenic noise is almost completely suppressed pigmentation changes, while the increased volume of natural background had almost no effect.