2008 Report on the Health of the Norway Lakes

The Lakes Association of Norway, with support from the Town of Norway, continued to monitor the health of the four Norway Lakes in 2008. Water quality monitoring was a combined effort of volunteers and lake professionals. Monitoring of the lakes takes place from early May through September, during the time of year when lakes and ponds are the most biologically productive, and water quality problems are most likely to occur. In addition to monitoring lake water quality, LAON also conducted a screening survey for invasive aquatic plants on the four lakes.

The weather that occurs during and preceding lake monitoring can have a strong influence on indicators of lake water quality, and is likely responsible for some of the variability that is measured within individual seasons and from one year to the next. The 2008 monitoring season was characterized by heavy snow melt during the spring, followed by heavy rain, which was extreme at times, from mid summer through the end of the monitoring season. In fact, according to National Weather Service data, Portland Maine experienced the 3rd wettest summer in 138 years (period of record)!

Rain and snow produce stormwater runoff, which is the primary means by which phosphorus and other pollutants are carried into lakes from their watersheds. One might expect that for years when excess precipitation has occurred during the spring and summer period, lakes might be less clear. Although that is often the case, each lake responds uniquely to the many factors that influence water quality. In 2008, the Maine Volunteer Lake Monitoring Program and Maine Department of Environmental Protection monitored the water clarity of 418 Maine lakes, which includes data from volunteers, agency personnel and other professionals. The four Norway Lakes are included in this group.

Nearly an equal number of lakes in the group were clearer than, and less clear than they have been historically, and approximately 13% of the lakes were as clear as their long-term average water clarity in 2008.

 Source: 2008 Maine Lakes Report

Maine VolunteerLake Monitoring Program

However, even though the numbers were nearly evenly split in 2008, the overall clarity of Maine lakes dropped in 2008, compared to 2007. The average water clarity for all Maine lakes monitored for individual years for the past four decades (which includes data collected for the Norway Lakes since the mid 70’s). The 2008 average of 5.34 meters for all Maine lakes was within the 5.0-5.5 meter range where it has fallen for many years since this information has been tracked. It is likely that the overall effect of the heavy rain in 2008 was to lower water clarity to drop slightly (average for all lakes).

 Source: 2008 Maine Lakes Report (Maine Volunteer Lake Monitoring Program)

Pennesseewassee Lake :

Pennesseewassee Lake was slightly less clear in 2008, when compared to the historical average for the lake. Water clarity averaged 5.4 meters during the five month period, ranging from a high reading of 6.0 meters, to a low reading of 4.2 meters. This compares to 5.6 meters in 2007, 5.9 meters in 2005, and the historical average for the lake of 5.8 meters.   

The concentration of phosphorus (the nutrient that is responsible for the growth of algae in lakes) averaged 9 parts per billion (ppb) in 2008, compared to 9 ppb in 2007, 7 ppb in 2006, 8 ppb in 2005, and the historical average of 9 ppb.

Chlorophyll-a (CHL) is a pigment that is measured to determine the concentration of algae in lake water. The 2008 average concentration measured 4.4 ppb, compared to 4.3 ppb in 2007, 4.4 ppb in 2006, and the 2005 average of 4.1 ppb The 2008 average was the same as the historical average of 4.4 ppb.

Two of the three primary indicators of water quality were average (phosphorus and chlorophyll-a), and one (water clarity) was slightly below average.

Late July, and August and September dissolved oxygen levels were very low in the deepest region of the lake, as has been the case for a number of years. In August, the deepest six meters of water, measured at the deepest point in the lake, were completely devoid of dissolved oxygen. By September, conditions had improved only slightly, as water temperatures cooled. Low concentrations of late summer dissolved oxygen serve as a warning that the lake is sensitive and vulnerable to a decline in water quality, regardless of conditions near the surface, where wind and wave action keep oxygen levels high throughout the summer.  

Natural water color levels were average in 2008, as were pH and total alkalinity. All were within the normal range of values for the lake.

No invasive aquatic plants were found in the screening survey of Pennesseewassee Lake in 2008. A native species of Milfoil is known to occur in this lake. However, this plant is not invasive.

A species of non-native, invasive snail, referred to as the “Chinese Mystery Snail” has been documented in the lake. This snail has now been observed in all four of the Norway lakes, as well as in a number of area waterbodies, including Thompson, the Range Ponds, and others. The ecological significance of this invader has not been determined. However, from a nuisance perspective, the large, dark green snails are offensive to the nose when they wash up on the shoreline, and there has been at least one report of oxygen depletion in a pond when a large number of the snails died over a short period of time.

Gleotrichia is a colonial blue-green algae that occurs naturally in many Maine lakes. Looking down into the water, “Gleo” has the appearance of tiny off-white dots, often likened to tapioca. In recent years, this algae has become problematic on some Maine lakes and ponds, and it may be on the increase throughout Maine. Moderate gleotrichia growth was observed in the surface water during the months of July and August.

Hobbs Pond (Little Penn):

Hobbs Pond (Little Penn) was relatively clear again in 2008, although not nearly as clear as it was in 2007. The water clarity average for the summer was 5.4 meters, compared to 6.1 meters in 2007 and 2006. The historical water clarity average for Hobbs Pond is 5.2 meters. In 2005, the average was 5.6 meters, and 5.9 meters in 2004. Hobbs has been significantly clearer than it’s historical average for a number of years. This is due primarily to an overall improvement in the clarity of the water in this pond during the past decade, compared to the previous two decades, during which water clarity was significantly lower.

Phosphorus levels were also lower than the average for this pond in 2008, averaging  8 ppb, which was also the 2007 average. This was substantially lower than the historical average of 11 ppb, and the 2006 average of 10 ppb!  The average concentration of chlorophyll-a (algal concentration in the pond) was 4.9 ppb, which is the historical average for the pond. The average for the summer would have been lower had it not been for a particularly high reading during the month of September.  

During the past decade, the water quality of Hobbs Pond has improved quite notably. Back in the late 1970’s and early 80’s, the annual water clarity was nearly always in the mid 4 meter range (about 15 feet). At times, individual water clarity readings were as low as 2.0 meters (about 6 feet). LAON took the initiative to work with landowners in the watershed to implement conservation practices, which resulted in a nearly immediate turnaround in water quality.

However, the same words of caution apply with Hobbs as with Penn and Sand: Late summer oxygen levels near the bottom of the pond were very low, and phosphorus samples taken near the bottom of the lake were moderately high (20 ppb) compared to surface concentrations. This means that, despite the fact that things look good near the surface, this pond is sensitive and vulnerable, and water quality could easily decline if continued efforts are not taken to protect the very good water quality that has been documented in recent years.

Other water quality indicators that are measured to help support the primary data (color, pH, and total alkalinity) were within the normal range of readings for Hobbs in 2007.

No invasive aquatic plants were detected in Hobbs Pond in the 2008 screening survey, however, as indicated above, the Chinese Mystery Snail was documented in the pond.

Sand Pond:

Sand Pond experienced a slightly above average year in all respects, and an improvement over conditions in 2007. Water clarity averaged 7.8 meters, compared to 7.0 meters in 2007, 7.7 meters in 2006, 8.5 meters in 2005, and the historical average of 7.4 meters. Sand Pond is the clearest of the four Norway Lakes, and in general, the water quality of this small pond is above average, compared to other Maine lakes. Consider that the average for all Maine lakes in 2008 was 5.3 meters.

The average total phosphorus concentration in Sand Pond last summer was 4 ppb, compared to the historical average of 7 ppb for the pond. The phosphorus average for Sand Pond in 2008 was the lowest that it has been for several years, and it was consistent with the very good water clarity last summer.

Chlorophyll-a levels were also lower in 2008 (2.5 ppb) than the historical average (2.7 ppb) for the pond. This was also consistent with the low phosphorus and excellent water clarity for Sand Pond in 2008.

Late summer (August) dissolved oxygen levels in 2008 were similar to those documented in 2007, which represented a slight improvement for Sand Pond, compared to conditions in late August, 2006. However, by September 21, there was virtually no oxygen in the water below 10 meters depth. The maximum depth of Sand Pond is approximately 17 meters (56 feet). Phosphorus samples taken near the bottom of the deepest area of the pond in late summer were four times as high (20 ppb) as samples taken near the surface (5 ppb). This suggests that the pond is in a very sensitive state, and that water quality could change if conservation measures are not employed for both existing and new development in the watershed. The potential for phosphorus from the bottom of Sand Pond to become available to algae growing near the surface is moderate.

All additional support indicators of water quality were within normal ranges in Sand Pond during the 2008 monitoring season.

No invasive aquatic plants were detected in the 2008 screening survey of Sand Pond. Although the Chinese Mystery Snail has been documented in the pond in the past, none were observed during the 2008 survey.

North Pond:

North Pond is relatively shallow, having a maximum depth of less than 15 feet. The shallow depth can limit the value of water clarity readings that are taken with a Secchi disk, because often the disk reaches the bottom of the pond before it disappears from view. In the 1970’s and 1980’s, the Seechi disk was nearly always visible on the bottom of North Pond. However, when the pond started to experience algal blooms, the situation changed. Often the disk would disappear in the algae-laden water before it reached the bottom at only 12-13 feet.

In 2008, the Secchi disk was visible on the bottom of North Pond throughout the five month monitoring period, which was also the case for most of 2007 and all of 2006.

The average phosphorus concentration for the year was 18, which is also the historical average for North Pond, but it was higher than the averages for 2007, 2006 and 2005. This was very likely due to the heavy rainfall in 2008.

The concentration of algae in the water, as indicated by chlorophyll-a levels,  was 5.0 ppb, which is considerably lower than the historical average for North Pond.

Phosphorus levels in North Pond are often higher than might be expected, based on water clarity and the actual concentration of algae in the water. This is most probably due to the fact that the very soft bottom sediments in this pond are easily resuspended in the overlying water, especially following periods of strong wind. The sediments raise the phosphorus levels in the water and reduce water clarity. But much of the phosphorus in the suspended sediment is not biologically available to the algae in the water.

Overall, North Pond experienced an average year, with relatively good water clarity, average phosphorus levels and slightly lower than average algae growth. No invasive aquatic plants were detected in the 2008 screening survey of North Pond, which included the extensive attached wetland areas that drain to Pennesseewassee. The Chinese Mystery Snail has existed in North Pond for more than a decade.

Summary:

We encountered mixed conditions in the four Norway Lakes in 2008. Overall, Pennesseewassee and North Pond were average, compared to the historical data for each, while Sand and Little Pennesseewassee (Hobbs) were above average.

Each lake and pond responds in a unique way to the influences of weather, changes in land use in the watershed, and other forces upon the ecosystem. This is because of the wide range of physical, chemical and biological characteristics of each lake basin and its watershed.

The following is a summary of findings for Pennesseewassee Lake, and Hobbs (Little Penn), Sand and North Ponds.

Special thanks are due to certified volunteer lake monitors Patti Ann Douglas on Sand Pond, and Warren Bryant on Pennesseewassee, and Ray Snedeker on Hobbs, who contributed additional Secchi disk transparency (water clarity) data in 2008. Their efforts substantially improve our confidence in the monitoring results for last summer.

Prepared by Scott Williams, Aquatic Biologist

Lake & Watershed Resource Management Associates

P.O. Box 65; Turner, ME 04282; 207-336-2980;  lwrma@megalink.net