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| GLOBAL WARNING |
Tanganyika
Kalalangabo, Tanzania
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| by Jori Lewis |
When the moon is not full, fishermen paddle out a few hundred meters on Lake Tanganyika, the longest freshwater lake in the world, in search of dagaa, a small nocturnal sardine. They dangle kerosene lamps over the sides of their wooden boats to attract zooplankton, dagaa's main food. Lure the zooplankton and the dagaa will follow.
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Although climate change threatens algae, algae also
may offer a solution. Some areas of the ocean have very little algae
growing in them, despite having plenty of nutrients, because they
are short on iron. Fertilizing the ocean with iron might spur the
plants to grow and absorb carbon dioxide. Any algae
that aren’t eaten would drift to the bottom of the ocean, carrying
their load of carbon to the watery deep. The late oceanographer John
Martin, a champion of the theory, once quipped, "Give me half a tanker
of iron and I will give you an ice age." But this kind of "global
engineering" is controversial, and practical experiments
have had mixed results.
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But many fishermen say nowadays the catch is way down. All along the Tanganyika basin, from Bujumbura in Burundi to Kalemie in the Congo to Mpulungu in Zambia, fishermen say the lake is changing, and with it, their way of life. Lake Tanganyika -- which holds 18 percent of the world's freshwater -- is getting warmer. Over the past 80 years, the temperature in the region has increased by .8 degrees Celsius. That doesn't seem like much, but two different studies in the journals Nature and Science report that the shift in temperature already is slowing down the growth rate of algae, which form the base of the food chain in Lake Tanganyika, and throughout the world's oceans. Fewer algae mean fewer zooplankton, which could mean fewer dagaa, which are the primary food of other fish living in the lake and villagers who live nearby.
When translated to the open ocean, this scenario could break down the food chain globally. Studies show phytoplankton -- free-floating marine plants, including algae -- are decreasing in the world's oceans. This not only affects the food chain but carbon dioxide levels as well. Phytoplankton currently suck up half the carbon dioxide in the world's atmosphere. Algae, in particular, are so useful as air scrubbers that forward-thinking power companies are building massive algae farms beside their smokestacks.
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