SECCHI DISC, TEMPERATURE AND OXYGEN                GLOEOTRICHIA                   PHOSPHORUS
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The photo shows a highly magnified single gloeo colony. Observed in the water, gloeo colonies appear to be the size of the head of a small pin.
 
Gloeotrichia (pronounced “glee-oh-tricky-ah”) echinulata is a colonial bluegreen algae that forms tiny spheres, which can be seen without magnification in lake water. “Gloeo” has been known to exist in Maine lakes for over 100 years.  It has typically been observed in late summer, in relatively low densities.  However, during the past decade, gloeo appears to have been on the increase in lakes throughout much of New England. Gloeo blooms have occurred earlier in the summer, and in higher densities. Research on the life cycle of this alga has suggested that gloeo may play a role in declining water quality of otherwise clear, low nutrient lakes.  It is a species of concern for lake managers, as it has been shown to push lakes towards eutrophication and produce deadly toxins.  PPA partnered with Bates Professor Holly Ewing to monitor gloeo at several sites on the lake from 2011 - 2019.  The study has ended for now, but it is becoming clear that the more phosphorus released by the bottom sediments, the more nutrients available for the phosphorus hungry gloeo. 
Factors that Affect Gloeo Abundance:
  • Light Like many other species, gloeo take biological cues from the intensity and duration of sunlight. They can only grow on sediments that are exposed to light.  The shape and contours of the lake bottom will control the area of the lake that is shallow enough for light to reach the bottom. Lake clarity and color also impact how deep light can penetrate. Low clarity and/or high color mean that less of the lake bottom is exposed to light.
  • Temperature Cyanobacteria, including Gloeo, have higher optimum temperatures than other algae types. Comparison of the population peak and seasonal temperature peak suggest that high temperatures influence the timing of Gloeo blooms. Climate change is causing temperatures to rise over time, which could explain why Gloeo may be becoming more prevalent in the Northeastern US.
  • Nutrients The quality and availability of nutrients within the sediment strongly influences Gloeo growth. Most cyanobacteria do not thrive in low-nutrient lakes because they rely on high phosphorus levels within the water. Unlike most algae, Gloeo cells divide primarily on lake sediments rather than in the water itself. Sediments contain relatively large amounts of phosphorus, which Gloeo use to grow before floating from the sediment into the water column when they mature. The algae cells can also store excess phosphorus which is used to reproduce once they are buoyant.
Researchers are concerned that Gloeo may be increasing nutrient levels and algae growth within lakes by moving phosphorus from the bottom of the lake up into the water column, where it can be used by other algae. Gloeo blooms are generally short-lived, lasting only about 2 weeks in late July and early August. Smaller amounts of the algae can be seen in early July and persist into September. Anecdotal reports indicate an increase in Gloeo abundance within New England over the last decade or two. While it has always been a part of the algae community in many lakes, increasing temperatures due to climate change may be accelerating growth. 

 

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