Pine Lake Summary Report for Oct 1994 - Sept 1995

Level I data were collected beginning in October 1994 through September 1995 by Kate Bradley as shown in the Level I data summary graphs for Pine Lake. During this monitoring period, lake surface temperature averaged 14.4°C. During the 1994-95 monitoring season, lake level fluctuated by 0.78 meters. Lake level increased rather dramatically between September and December and then remained high through April before gradually dropping. Generally, the peaks in lake level during the winter, were preceded by several days of heavy rainfall. Total precipitation was 1245 millimeters during 1994-95. Secchi depth averaged 4.0 meters with a maximum value of 6.3 meters observed in April and May of 1995. The water varied from clear to light green in color as observed by Ms. Bradley.

Level II data were collected during May through October of 1995 by Kate Bradley. The Level II data summary graphs for Pine Lake show the winter monthly and summer bimonthly measurements of Secchi depth, chlorophyll a, total phosphorus, and total nitrogen for Pine Lake. The lake data were compared with one standard deviation about the median value of the combined data collected for all the level II participating lakes. Based on these seasonal data, Secchi depth averaged 4.7 meters for 1995. Chlorophyll a concentrations averaged 3.9 µg/L for 1995. Peak chlorophyll a concentrations of 32 µg/L and 25 µg/L were observed in February 1994 and 1995. Summer total phosphorus concentrations averaged 17 µg/L, while total nitrogen concentrations averaged 419 µg/L for 1995.

For the most part, Secchi depth, chlorophyll a, total phosphorus, and total nitrogen values fell within or on the low end of those values observed on other lakes in King County. Blue-green algal blooms were reported by Ms. Bradley and other lake residents during February 1995 and January 1996. Algal samples were taken during February 1995 and January 1996 to evaluate them for blue-green toxicity. The results of the testing showed that the bloom was non-toxic. The bloom species for both events was Aphanizomenon flosa—quae.