North Temperate Lakes LTER: Color - Trout Lake Area 1989 - current

Color is measured four times a year in the seven northern study lakes (Allequash, Big
Muskellunge, Crystal, Sparkling, and Trout lakes, unnamed lakes 27-02 [Crystal Bog] and
12-15 [Trout Bog]) in water samples that are filtered in the field through 0.45 um
nucleopore membrane filters. A spectrophotometer is used to quantify color in the lab as
absorbance (unitless) at 1 nm intervals between the wavelengths of 200 and 800 nm (Note:
Prior to August 2008, samples were initially run in 10cm cuvettes. Starting in Aug 2008,
samples are initially run in 5cm cuvettes. Absorbance data are considered suspect for values
greater than 2. Lakes with suspect data (typically, the bog lakes) are re-analyzed in the
200-400 nm range in 1 cm cuvettes. The data values are linear with respect to cuvette size.
I.e, data from the 1cm cuvettes should be multiplied by 5 to be comparable with 5cm cuvette
data and multiplied by 10 to be comparable with 10cm cuvette data. Data from 5cm cuvettes
should be multiplied by 2 to be comparable with the older 10cm cuvette data. Sampling
Frequency: 4 times annually Number of sites: 7