Lake Agawam Health: A Balancing Act

2011 So Far

During the spring and summer of 2011, Lake Agawam continued a very hopeful trend of improving water quality.

Compared to 2010, temperatures were lower, not exceeding 26°C (Fig 7; 78.8°F).

Moreover, oxygen levels in the Lake remained high through the summer. Oxygen levels exceeding 5 mg /L are ideal for a healthy ecosystem, and these values were maintained throughout the monitoring period (Fig 4). The longer term trend for oxygen in Lake Agawam is good.

Chlorophyll and phycocyanin are proxies for algae and blue-green algae, respectively, present in Lake Agawam. Chlorophyll levels were in a very moderate range for much of the summer, fluctuating between 10 and 20 mg/L (Fig 1), significantly lower than past summers and lower than the US EPA standard of a lake over-enriched with algae (above 25 ug/L). Similarly, the phycocyanin levels also remained low compared to past years (Fig 2).

Real Time Monitoring With Sondes Device

In late August, real time monitoring (every 15-minute data collected) with a water quality sondes device commenced in Lake Agawam. The period of late August and September were marked by abnormally high levels of rainfall. Such rainfall delivers large volumes of run-off and nutrients to Lake Agawam. The effect of the rainfall and run-off on Lake Agawam during late August and September was clear from our real-time monitoring.

Chlorophyll levels that had been low spiked by more than 50% during this period (Fig 3) and the lake took on a green coloration due to these blue-green algal blooms that became visually obvious, particularly at the north end of the Lake. Some of the blue-green algae which grow in Lake Agawam can be harmful or toxic to the ecosystem. This observation emphasizes the need to improve stormwater abatement to Lake Agawam to reduce the frequency and intensity of algal blooms in Lake Agawam.

As the writing of this report in early October, the intense blue green algae bloom continued. More updates will be provided as they become available.

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The following data and analysis represents the work of Christopher J. Gobler, PhD and his students at the Stony Brook University School of Marine and Atmospheric Sciences.

• Chlorophyll and Phycocyanin In Lake Agawam
• Dissolved Oxygen in Lake Agawam
• Lake Temperature
• Blue Green Algae Blooms
• Nitrogen Budget for Lake Agawam
• Results of Experimental Decrease of Nutrients

Chlorophyll and Phycocyanin In Lake Agawam

2011 levels were low during the summer, but heavy rains in August and September demonstrated that rainwater run-off remains a major contributor to periodic algae blooms. Updated: October, 2011

Fig. 1: Chlorophyll concentrations between May and August, 2011.

Fig. 2: Phycocyanin levels between May and August, 2011.

Fig. 3: Real-time chlorophyll readings collected from the water quality sondes device during September, 2011.

Fig. 4: Average levels of chlorophyll in Lake Agawam during the spring, summer, and fall months of 2003 - 2010. (last updated July 2011)

Chlorophyll and phycocyanin levels are used as indicators of algae concentraions in lakes and oceans. Algae are also called phytoplankton or microalgae. They are microscopic plant cells which grow in all water bodies.

The US EPA defines the health of lakes based on their levels of chlorophyll because the overgrowth of algae can be problematic for aquatic ecosystems, leading to the loss of oxygen and fish. According to the US EPA, chlorophyll levels exceeding 25 micrograms per liter are considered hypereutrophic, meaning they have higher levels of nutrients and high levels of chlorophyll which can endanger aquatic ecosystems.

Dissolved Oxygen in Lake Agawam

Although levels are generally high, persistent algal blooms can cause rapid drops in oxygen levels which can be lethal to fish. Updated: October, 2011

Fig. 5: Dissolved oxygen levels between May and August 2011.

Fig. 6: Real-time dissolved oxygen levels collected from the water quality sondes device during September, 2011.

Fig. 7: Average levels of dissolved oxygen in Lake Agawam during the spring, summer, and fall months of 2003 - 2010. (last updated July 2011)

Dissolved oxygen is critical for the survival of all animals and levels above 5 milligrams per liter are required for robust health of fish. Although Lake Agawam has been in the hypereutrophic range with regard to chlorophyll, its oxygen levels have, on average, been good, partly due to day time photosynthesis by algae.

However, rapid declines in, or die-off of, algae can lead to a rapid reduction in oxygen levels. This was observed in the fall of 2006 when a "bloom" of algae died; oxygen levels rapidly decreased to less than 1 milligram per liter, and thousands of fish died in Lake Agawam. Reducing levels of nutrients entering Lake Agawam should reduce the levels of algae and decrease the likeihood of rapid declines in oxygen and fish kills in the future.

Lake Temperature

Fig. 8: Lake temperature between May and August, 2011.

Fig. 9: Real-time lake temperature readings collected from the water quality sondes device during September, 2011.

Blue Green Algae Bloom

The bright green coloration of the water and the accumulation of green material in surface waters of Lake Agawam are visable signs of a blue-green algae bloom. Such blooms are symptoms of too many nutrients entering a lake. At very high levels the algae are a health risk if consumed by animals and humans.

Nitrogen Budget For Lake Agawam

Lake Agawam's sources of nitrogen. (last updated April 11, 2009)

In 2007, Professor Chris Gobler and his graduate students Matt Harke and Tim Davis quantified the sources of nutrients entering Lake Agawam. They found that the largest sources of nitrogen entering the lake were from groundwater, sediments, and the storm drain at the north end of the lake. This finding is important because nitrogen stimulates blue-green algae in the lake. Future efforts to improve the water quality of Lake Agswam should focus on reducing levels of nitrogen and phosphorus entering the lake.

Reducing Nutrient Levels in Lake Agawam By Half: Cyanobacteria

This graphic depicts a series of experiments conducted by Professor Chris Gobler and his graduate students Matt Harke and Tim Davis. (last updated April 11, 2009)

It compares the levels of blue-green algae (as measured by phycocyanin) resulting from an experimental 50% decrease in the nutrients in Lake Agawam to doing nothing ("Business as usual"). The results suggest that a decrease in nutrients in Lake Agawam could decrease the abundance of blue-green algae in the lake, which would then boost the oxygen levels of the lake. This increase in oxygen levels could then improve the overall health of Lake Agawam.