Song Lake Watershed and Environment Committee
Excerpts from
NYS Department of Environmental Conservation, Division of Water
Song Lake, 2008 Citizen’ Statewide Lake Assessment Program *
4/9/2010
From Page v, General Comments and Questions:
Based on these data, what should be done to improve or maintain Song Lake?
Given the moderately high lake productivity, management of water quality conditions in Song Lake
should focus on reducing nutrient loading to the lake, through maintaining septic systems, shoreline
buffer zones, limited use of lawn fertilizers, minimizing land disturbances in the near-lake watershed,
and localized stormwater management. The lake association is also advised to minimize introductions of
exotic plants and animals from public and private launching areas into the lake, particularly given their
abundance in many nearby lakes.
From pages 2 and 3, CSLAP Sampling Parameters:
Trophic Status Indicators for Song Lake
Phosphorus (Still mesotrophic, but higher 0.020 is considered eutrophic ) (mg/l)
Average for 2008 0.016 (0.015 in 2007)
Chlorophyll a ( eutrophic category this year, as over 8 is considered eutrophic ) (μg/l)
Average for 2008 8.2 (7.4 in 2007)
Secchi Disk (Still mesotrophic, but degraded. Less than 2 is considered eutrophic )
Clarity (m) Average for 2008 2.7 (2.9 in 2007)
By the Secchi disk transparency and total phosphorus trophic standards described above, the lake
would be considered mesotrophic, or moderately productive, while by the chlorophyll a standards the
lake would be considered eutrophic, or highly productive. The most appropriate trophic designation for
the lake is probably mesoeutrophic, or moderately to highly productive. The trophic classification for the
lake has been consistent for the three CSLAP sampling seasons at the lake.
Pages 35, 38, 40, 41 and 43:
What Happened at Song Lake in 2008?
Water clarity readings were consistently lower than normal throughout the 2008 sampling
season, and these readings decreased as the summer progressed. This appeared to be more in response to
higher algae levels than higher water color—the lowest clarity occurred when algae levels were highest
(and color readings were lower than normal).
What Happened at Song Lake in 2008?
Phosphorus readings were higher than normal throughout the summer, consistent with the higher
chlorophyll a readings and lower water transparency during much of the year. These readings also
increased over the course of the summer.
Detailed Discussion #7- Phosphorus
...
There are several factors at play. Increased use of the lake occurs during the summer,
taxing the septic systems and creating a more significant hydraulic and nutrient load to
the leach field and ultimately the lake. This is consistent with a seasonal increase in
conductivity (see Figure 11c), a pattern generally not observed in deeper lakes. Both
shallow and deep lakes exhibit aerobic sediment release, a lesser phenomenon than
nutrient release under anoxic conditions, but more substantial in shallow lakes with few if
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*The full report is available on request
Song Lake Watershed and Environment Committee
Excerpts from
NYS Department of Environmental Conservation, Division of Water
Song Lake, 2008 Citizen’ Statewide Lake Assessment Program *
4/9/2010
any zones of poorly oxygenated water. Nutrients and nearly all other materials in lakes
are concentrated by evaporation, which increases substantially during the summer. For
many lakes, the senescence of macrophytes occurs in early to mid summer, particularly
when plant communities are dominated by Potamogeton crispus (curly-leafed
pondweed). This early season macrophyte will usually die out by early July, resulting in a
release of nutrients into the water. It should be noted that most of the nutrients
encompassed in the plant stems and leaves comes from the sediments, not the water
column, and these nutrients usually go back into the sediments later in the year.
This seasonal increase in phosphorus in shallow lakes appears to be the primary cause
of the seasonal increase in algae levels in these shallow lakes (as is apparent in Figure
19c), and as discussed below.
What Was Expected in 2008?
Chlorophyll a levels cannot be well predicted in dry years, as observed in Figure 19a. However,
chlorophyll a readings are occasionally higher than normal during wet years. Since at least the winter
and spring of 2008 was wet in most of the state, algae levels in New York state could be expected to be
higher than normal.
What Happened at Song Lake in 2008?
Chlorophyll a readings were close to normal in the beginning of the 2008 CSLAP sampling
season, but were higher than normal in mid- to late-summer, consistent with the lower water clarity
readings.
HOWEVER, the report goes on:
How closely connected are phosphorus and chlorophyll a?
As is apparent from the plot on the upper left, which shows the average chlorophyll a
(Chl.a) reading for each CSLAP lake plotted against the average total phosphorus (TP)
levels for the lake, there is a strong correlation between phosphorus and chlorophyll a.
This plot shows that nearly 75% of the variability in chlorophyll a readings is explained
by changes in phosphorus concentrations. This relationship is less clear when considering
only lakes with slightly lower phosphorus concentrations, as seen in the plot to the upper
right. This plot shows that phosphorus levels below about 2 ppb (=0.002 mg/l) are
insufficient to produce measureable algae levels. This corresponds to the lower analytical
detection limit for phosphorus.
Pages 59 and 60: Summary:
The CSLAP dataset indicates that Song Lake is a mesoeutrophic, or moderately to highly
productive lake, based on Secchi disk transparency, phosphorus (both mesotrophic) and
chlorophyll a (eutrophic) readings in the lake. The productivity of Song Lake was higher in
the last two years than in 1988. It is not yet known if this represents normal variability or an
actual increase in nutrient and algae levels and decrease in water clarity. This may become
clearer with additional data. There is a strong correlation between changes in clarity and
algae, and a lesser connection between changes in phosphorus and algae and between
changes in clarity and water color. However, it is likely that lake management activities
2
*The full report is available on request
Song Lake Watershed and Environment Committee
Excerpts from
NYS Department of Environmental Conservation, Division of Water
Song Lake, 2008 Citizen’ Statewide Lake Assessment Program *
4/9/2010
directed toward increasing water clarity and reducing algal blooms in the lake should target
nutrient loading to the lake. Water clarity readings decrease through late summer, coincident
with seasonally increasing algae and nutrient readings. The limited deepwater nutrient
readings indicate that some nutrients may come from deepwater sediment during the
summer, but that the primary lake nutrients come from the watershed. Phosphorus readings
are only occasionally above the state guidance value for lakes used for contact recreation
(swimming), and Secchi disk transparency readings at all times exceed the minimum
recommended water clarity for swimming beaches (= 1.2 meters). In short, Song Lake
exhibits characteristics of a mesoeutrophic lake. The lake was more productive in the last two
years than in 1988, but it is not yet known if this reflects the influence of wetter weather,
normal variability, or an actual increase in lake productivity. Additional data will be needed
to evaluate any long-term trends.
Water transparency readings are more strongly influenced by algae than color, although water color
may limit water clarity when algae levels are very low. Color readings have been higher in
the last two years than in 1988, an increase seen in many other CSLAP lakes in response to
wetter weather (and perhaps the change in laboratories). Nitrate, ammonia and total nitrogen
readings are low, and none of these nitrogen indicators appears to represent a threat to water quality.
Total nitrogen is comprised primarily of organic nitrogen. The nitrogen-to phosphorus
ratios indicate that algae growth is controlled by phosphorus.
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*The full report is available on request