Lake Sammamish Research Articles

Enriching effects of Urban runoff on the productivity of a mesotrophic lake

Sewage was diverted from Lake Sammamish in September, 1968, and since then there have been no significant responses by trophic indicators which indicate the lake is beginning to recover. To explain this delay in response, extensive urban development in the lake's watershed was considered as a factor which might be acting to inhibit the lake's recovery. In vitro uni-algal experiments with water from 13 streams which drain urban and undeveloped areas showed that about half of the streams stimulated algal growth significantly, but these streams constitute less than 14 per cent of the lake's total water income. Of these six streams only two drain urban areas and account for less than 2 per cent of the water income. In situ experiments showed that no streams were significantly stimulatory to natural populations of phytoplankton. Other in situ studies showed that one urban stream and two from undeveloped areas caused substantial increases in periphyton growth after a 12-day period, although these increases were not statistically significant. Additional in situ nutrient limitation experiments in August of 1970 and 1971 revealed that P and N were limiting only in combination. Results from these studies do not support the contention that urban runoff is seriously enriching the limnetic region of Lake Sammamish.

Chemical Control of the Carrot Rust Fly, Psila rosae (F.), in Western Washington1

The carrot rust fly (Psila rosae (F.)) is normally controlled in Washington by soil and surface applications of chlorinated hydrocarbons. In 1957 a strain of Psila rosae highly resistant to the chlorinated hydrocarbons appeared in the Lake Sammamish region in northwestern Washington. The carrot crop was destroyed despite repeated soil and surface treatments with chlorinated hydrocarbons. Twenty-two compounds, including chlorinated hydrocarbons and organic phosphates, were tested as soil or furrow treatments. Am. Cyanamid 18133 (0,0-diethyl 0-2- pyrazinyl phosphorothioate), dicapthon, and parathion gave fair control when used as furrow treatments. Diazinon® (0,0- diethyl 0-(2-isopropyl-4-methyl-6-pyrimidinyl) phosphorothioate gave outstanding control as a furrow treatment when used at rates of 1, 2, 3 or 4 1bs. of active ingredient per acre. Diazinon was ineffective at 5 pounds per acre when used as a total soil treatment. All other compounds tested were ineffective when used as soil or furrow treatments.