Environment & ecology. (Science News of the year: the weekly newsmagazine of science).

Frog woes At water concentrations found in the environment, the weed killer atrazine stripped male frogs of their masculinity, suggesting that the chemical is partly responsible for global amphibian declines (161: 243 *; 162: 275 *).

Troubled waters Several dozen organic contaminants were quantified in U.S. streams, and the chemicals' combined effects may be killing aquatic organisms (161:181).

Fish beware Pfiesteria microbes, implicated in fish kills and human illness along the mid-Atlantic U.S. coast, turned up in Norway (161: 39). Another study suggested that some types of Pfiesteria don't produce a toxin but kill by eating holes in a fish's skin (162: 84).

Polluting seas Chemical analyses of seawater provided the first direct evidence that the ocean may be a significant source of atmospheric gases--alkyl nitrates--that scientists had assumed trace mainly to industrial activity (162: 102).

Legal steroids Farm-field runoff containing hormones excreted by steroid-treated livestock appeared capable of harming aquatic life (161: 10 *).

Light blight Researchers found reason to suspect that artificial lighting at night disrupts the physiology and behavior of nocturnal animals (161: 248 *).

Teenage hold up A study of adolescents suggested that widespread environmental pollutants, such as polychlorinated biphenyls and dioxins, might be delaying young people's sexual development (162: 3).

Tougher weeds Tests on sunflowers showed that a lab-engineered gene from a crop plant, if introduced into its wild relative, can give the native plant a survival edge over other wild plants (162: 99 *).

Wasteful harvest New research and policy developments aimed to curb the practice of killing sharks solely for their fins, an Asian delicacy (162: 232 *).

Drugs afield Researchers found that antibiotics excreted by people and animals have the potential to poison plants and end up in food (161: 406 *).

Clay slays Scientists experimented with sprays of dirt particles to kill toxic algae in seawater (162: 344).

Mercurial foliage A study discovered that fallen leaves that collect in stagnant water can release toxic mercury, which can eventually accumulate in fish far downstream (161: 148).

Embryonic losses Minuscule amounts of over-the-counter weed killers impaired reproduction in mice (162: 228).

Dioxin's new target Scientists found indications that dioxin, a hormonelike pollutant, can trigger breast cancer in heavily exposed women (162: 77).

Killer cocktails Trace amounts of human-excreted drugs in waterways appeared to work together to deform and kill native microscopic organisms (162: 101).

Smoking gun Living with a smoker at least doubled a cat's risk of developing the feline analog of the cancer non-Hodgkin's lymphoma (162: 125).

Cold war Algae fight over nutrients, and one Swedish combatant under frozen lakes apparently prevails by poisoning its adversaries (161: 61).

Pollution magnet Atmospheric scientists learned that the Mediterranean Sea is a crossroads for pollution-laden air currents from Europe, Asia, and North America (162: 261).

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