To scientists who study lakes and rivers, it seems humans have embarked on a huge unplanned experiment. By burning fossil fuels, we have already raised the concentration of carbon dioxide in the atmosphere by 40 percent, and we’re on track to increase it by much more. Some of that gas may mix into the world’s inland waters, and recent studies hint that this may have profound effects on the species that live in them. Scientists began taking continuous measurements of carbon dioxide in the atmosphere in the 1950s, and today they have more than six decades of consistent readings. In the 1980s, oceanographers followed suit, developing carbon dioxide sensors and deploying them across the planet. Over the past three decades, they’ve chronicled a steady rise of carbon dioxide in seawater. The increasing concentration can harm marine life in many ways.
It lowers the pH of seawater, for one thing, making it more acidic and interfering with the chemistry that coral, for instance, use to build their calcium skeletons. Ocean acidification also thins the shells of oysters and other animals.Many marine organisms rely on chemical changes in water to find food and avoid danger. “Many fish are not able to detect their predators anymore,” said Linda C. Weiss, an aquatic ecologist at Ruhr University Bochum in Germany. “They can even get more bold.” Now that researchers have grown concerned about carbon dioxide levels, they’ve been developing ways to reconstruct their history.
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Humans, chimpanzees, elephants, and bottle-nosed dolphins can recognize themselves in a mirror, according to scientific reports, although as any human past age 50 knows, that first glance in the morning may yield ambiguous results. Mirror self-recognition, at least after noon, is often taken as a measure of a kind of intelligence and self-awareness, although not all scientists agree. Researchers have wondered not only about which species display this ability, but about when it emerges during early development. Children start showing signs of self-recognition at about 12 months at the earliest and chimpanzees at two years old, but dolphins start mugging for the mirror as early as seven months, earlier than humans.
Diana Reiss a psychologist at Hunter College, and Rachel Morrison, then a graduate student working with Reiss, studied two young dolphins over three years at the National Aquarium in Baltimore. Dr. Reiss said the timing of the emergence of self-recognition is significant, because in human children the ability has been tied to other milestones of physical and social development. Since dolphins develop earlier than humans in those areas, the researchers predicted that dolphins should show self-awareness earlier. Seven months was when Bayley, a female, started showing self-directed behavior, like twirling and taking unusual poses. Foster, the male, was almost 14 months when the study started. He had a particular fondness for turning upside down and blowing bubbles in front of the one-way mirror in the aquarium wall through which the researchers observed and recorded what the dolphins were doing. The animals also passed a test in which the researchers drew a mark on some part of the dolphin’s body it could not see without a mirror. In this so-called mark test, the animal must notice and pay attention to the mark. Animals with hands point at the mark and may touch it. |
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March 2018
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