August 4, 2016

Maps in The World Book Encyclopedia tend to show bodies of water in blue, and, despite the many colors of water we see every day—blue, brown, gray, green, white, clear, or even iridescent—we generally accept that blue represents water. Along the south coast of Western Australia, however, two naturally pink lakes challenge that color representation. The pink lakes lie on the rugged coast near Esperance and on nearby Middle Island in the Recherche Archipelago. The traditionally blue waters of the Great Australian Bight (a large bay in the southeastern Indian Ocean) contrast strongly against the vivid pinks of the lakes. (more…)

March 28

The U.S. Environmental Protection Agency (EPA) released the results of a study on March 26 that revealed that 55 percent of rivers and streams in the United States were in poor biological condition for aquatic life. Nutrient pollution–phosphorus and nitrogen runoff from cities and farms that enters into rivers and streams–formed the  major problem within the 1.2 million miles (1.9 million kilometers) of U.S. waterways.

Large amounts of nutrients in water lead to problems for many animals that live in water. Unnaturally high levels of nitrogen and phosphorus–which are the major components of fertilizer in agriculture and waste in sewage systems–leads to a process known as eutrophication. The excess nutrients benefit algae and allow them to grow much faster. But, an overgrowth of algae, called algal bloom–decreases the amount of oxygen in the water, which leads to the death of fish and other aquatic life. In addition, some algal blooms create poisons (toxins) that are harmful or even fatal to humans.

Excess nutrients from such sources as fertilizers and untreated sewage upset the balance in aquatic systems. This process is called eutrophication. The algae grow faster than the fish can eat them. As more algae grow, more also die and block light needed by aquatic plants. Bacteria use up much oxygen consuming the excess dead algae. The oxygen level of the water drops, causing many aquatic plants and animals to die and decay, using still more oxygen. (WORLD BOOK illustration by Michael Yurkovic)

According to the EPA, their study indicated that the western United States had the best stream and river quality, with 42 percent in good condition. In the East and the plains, only 17 percent and 16 percent, respectively, of waterways were in good condition.

Additional World Book articles:

• Environmental pollution (2008 back in time)
• Water pollution

A website of interest:

• United States Environmental Protection Agency: Nutrient Pollution

November 26, 2012

Animals often feed on plants, and some plants even feed on animals. But researchers have recently identified the first plants that feed on other plants. The cannibalistic plants are green algae, which scientists classify as Chlamydomonas reinhardtii. Although algae are not true plants, green algae are close relatives that ordinarily make their own food through photosynthesis. In photosynthesis, plants and similar organisms use the energy in sunlight to combine water and the gas carbon dioxide, forming sugar. However, the freshwater algae C. reinhardtii often live in the soil, where they may not have access to sunlight and carbon dioxide. Under those conditions, the algae switch to feeding on plant matter in the soil.

The plant matter the algae feed on is cellulose, a tough material in the walls of plant cells and many kinds of algae. Cellulose is a long chain of sugars. The algae release a chemical called an enzyme that can break cellulose apart into simple sugars. The algae then consume these sugars for food.

Microscopic algae often grow in bodies of water. Spherical colonies of the green alga Volvox (above) consist of many cells. Other kinds of algae have only one cell. (E. R. Degginger)

Scientists have identified many plants that live as parasites on other plants. These plants steal nutrients, often by taking the juices of another plant. But the green algae are the first plantlike organisms known to dissolve cellulose, which makes up the body of the plant itself. Previously, only certain bacteria and fungi were thought to have this ability. Researchers suspect that other kinds of algae may also be able to dissolve cellulose.

The discovery may prove useful in efforts to produce biofuels. Biofuels are fuels made from living things that can be regrown quickly. Thus, biofuels are renewable fuels, unlike such fossil fuels as coal and oil. Much research into producing biofuels has focused on growing algae. However, processing the algae into fuel requires using expensive chemicals to dissolve cellulose. An alga that can dissolve cellulose might make biofuel cheaper to produce, helping biofuels to compete with fossil fuels.

The research was led by Olaf Kruse of Bielefeld University in Westphalia, Germany. It was published in the November 20 issue of the journal Nature Communications.

Additional World Book articles:

• Lichen
• The Green Gold of Algal Biofuel (a Special Report)