Primary Productivity Sample Clauses

Primary Productivity. Phytoplankton production was assessed by measuring chlorophyll a. Chlorophyll a composite samples were taken from the epilimnion, metalimnion, and hypolimnion at three established water quality sites. One site was the water quality sampling location established at the deepest point (northern end) in the lake. Two additional sites were established at the deepest points in the middle and southern parts of the lake. For the middle and southern chlorophyll sampling sites, the Hydrolab was used to measure water temperatures every 5m of depth to establish the epilimnion, metalimnion, and hypolimnion. Water samples were again taken from the surface to the bottom at 5m intervals in the epilimnion and metalimnion and 10m intervals in the hypolimnion using a Xxx Xxxx sampling bottle. Composite samples were made for each stratum by taking an equal amount of water from each depth sampled in the stratum. Water samples were stored on ice until analyzed.

Primary Productivity. Chlorophyll a is often used as a trophic state indicator for primary production (Xxxxxxx 1977). Chlorophyll a in Xxxxxxxx Lake was low, averaging 0.60 µg/l, compared to 1.5 µg/l - 20 µg/l in more productive lakes. In addition, Secchi disk transparency was deep (average 13m), allowing for a large euphotic zone, indicating a system with dispersed phytoplankton production throughout the large euphotic zone. It also indicates a lake with very low primary productivity. Chlorophyll a was relatively steady in the lake over the study period, which is consistent with results found by Nine and Xxxxxx (2005). Chlorophyll a in Outlet Creek was even lower than in the lake, averaging 0.35 µg/l. However, chlorophyll a in Outlet Creek was undetectable in the summer, increased dramatically in October, then declined somewhat in November (Figure 8). This increase in chlorophyll a in Outlet Creek appears to have coincided with the drawdown of Xxxxxxxx Lake, which began approximately October 1.