Algal Blooms and Common Loons in Maine

Maggie Denison

Maine's Lakes and Ponds

 Maine has over 6,000 lakes and ponds. These waterbodies are home to a wide range of wildlife and plant species. Maintaining high water quality in Maine’s lakes and ponds is essential to protect the health of these habitats and the species that use them.

Maine Lakes

Maine's Loons

A family of 4 loons can consume about 1,000 lbs of fish in 3 months. (Photo credit: Ray Yeager)

Many of Maine's lakes and ponds provide breeding habitat or feeding areas for the common loon (Gavia immer). Loons hunt by sight, chasing their prey underwater. Consequently, loons need clear water. While the common loon’s diet primarily consists of fish, they will also eat crustaceans and aquatic and marine invertebrates. A family of 4 loons (2 adults and 2 chicks) consume approximately 1,000 lbs of fish and other prey during the 3 months it takes to raise the chicks from hatching to fledging.

Map of Common Loon Range from Cornell Lab of Ornithology (allaboutbirds.org)

Common loon breeding range has shrunk in recent decades, moving northward across the U.S. and Canada as human-driven climate change causes a rise in average temperatures. Human activity can impact loons in other ways too. As shorelines are developed, loons may be less successful in locating suitable nesting sites. Mercury, lead, acid rain and oil spills are all harmful to loons across their summer and winter ranges. Increased nutrient loads in lakes can cause non-toxic algal blooms which reduce water clarity, potentially reducing fishing success for loons. Several types of cyanobacteria found in algal blooms produce neurotoxins, which are harmful to many species of animals including loons, fish, and humans.

This map shows the density of common loons surveyed in 2018. Explore the map using the +/- arrows in the lower right. Click on the purple circles for more information.

Algal Blooms

What are they and why do they matter?

Photo Courtesy of the NYSDEC HAB Photo Gallery

Algal blooms occur when there is an over-abundance of nutrients in a waterbody. Excess phosphorus (P) and nitrogen (N) in the water or sediment are the leading causes of algal blooms, but as P is usually the limiting nutrient for algal growth it can serve as a more accurate indicator than N of bloom potential. Like fertilizer on a garden, these excess nutrients in the water encourage algal growth. As algae are photosynthetic organisms, they need light in order to grow - so in lakes with lower "color" (lower organic acid content) light can penetrate farther into the water column resulting in higher rates of algal growth. Once the algae dies, the process of decomposing such a large mass of plant matter can deplete lake oxygen levels causing die-offs of fish and other aquatic species.

Photo Credit: Jennifer L. Graham - USGS

Some algal blooms are caused by toxin-producing cyanobacteria (commonly called blue-green algae). These cyanobacteria can produce neurotoxins that can have harmful or even lethal effects on people, domestic animals and wildlife.

Loons may be especially susceptible to harmful effects of algal blooms due to food scarcity, as blooms cause fish-die offs, and reduced visibility inhibiting foraging efficiency. Loons could also be directly harmed by the toxins produced by cyanobacteria. Researchers at University of New Hampshire have recorded increased levels of bacterial  neurotoxins in loon chick feathers .

Locating Potential Algal Blooms in Maine

The map below shows lakes that could have either non-toxic or toxic algal blooms. Using the most recently available Maine Department of Environmental Protection (DEP) annual water quality summary data, lakes were grouped by: year (2018); mean color of less than 30 SPU; amount of total phosphorus (sampled from the epilimnion - upper level of water column) in parts per billion (ppb). Please note: this map represents potential blooms and is not meant to show bloom history or to guarantee future bloom presence.

This map shows potential bloom risk for Maine lakes using the most recently available DEP water quality data (2018). Explore the map and click lakes for more detailed water quality information. If the lakes all appear blue, zoom in further to activate the layer with total phosphorus (ppb). Click on the lakes for additional water quality information.

Loons and Bloom Risk

Putting it all together:

Given their resource needs and biology, common loons may be highly susceptible to the harmful effects of algal blooms.

As you explore the map consider where in the state loons are most exposed to potential algal blooms. Consider lake size and potential bloom risk. You can change the base map to look at satellite imagery of shorelines and consider why certain lakes might be more susceptible to blooms than others?

Exploring the Map:

At the moment, the map shows only the total phosphorus layer. If you zoom in farther (using the +/- icons in the upper left) purple circles will appear indicating loon presence and density.

You can use the swipe tool in the upper left of the map to swipe the loon layer over the lakes.

If you get lost in the map, the house icon on the left will return you to the map of Maine.

Click on the lakes for more information.

Note: Pop-ups may have more than one page of information. You can navigate through these pages using the right arrow icon below the lake name. If the pop-ups only show headers, click the circled arrow on the right side of the header bar to see full pop-up information.

In 2018, the annual Maine Audubon Loon Count recorded 3,269 adults and 406 chicks across their survey area. It is worth noting that as the Audubon loon count does not survey every lake in the state, these numbers are likely a conservative estimate of the state's total population.

DEP water quality data was not available for every lake in 2018. These maps represent the available 2018 data.

Climate Change & Algal Blooms

Climate Change is Likely to Increase Bloom Occurrence

Image Courtesy of the Northeast Climate Impact Assessment (Maine Summary).

Algal blooms occur during summer months when temperatures are higher. As the climate changes and average yearly temperatures climb, algal blooms may become more frequent. As the  Maine Climate Council Report  states, average lake surface water temperature in Northern New England increased by 1.4 degrees Fahrenheit each decade (1984-2014). This means that these lakes (including Maine's) are warming at a higher rate than the worldwide average!

Average Maine lake water temperatures have warmed at almost double the rate of air temperature over recent decades making it likely that Maine's lakes could see even more drastic warming in the future.

Climate change is also likely to bring increasingly severe weather events which will result in more nutrients like phosphorus and nitrogen entering lakes via storm water runoff. Longer periods of drought can lower lake levels, reduce flushing rates and concentrate nutrients in the water column - further exacerbating the potential for large-scale algal blooms.

What now?

Keeping excess nutrients from entering streams, rivers, lakes and ponds can help reduce the chance of large algal or cyanobacteria blooms. Maintaining or creating multi-layer vegetative buffers around lakes can help slow runoff and decrease the amount that enters lakes and ponds. Buffers can also provide shade along shorelines which could help mitigate some of the effects of rising water temperatures in shallow areas.

Loons in Maine, and across the continent, are already vulnerable to the risks posed by lead poisoning, boat strikes, fishing line entanglement, injury, and disease. Increased algal bloom frequency is an additional threat that could put them in an even tougher position.

Photo Credit: Ray Yeager

This Storymap was made using ESRI

Maine Lakes

A family of 4 loons can consume about 1,000 lbs of fish in 3 months. (Photo credit: Ray Yeager)

Map of Common Loon Range from Cornell Lab of Ornithology (allaboutbirds.org)

Photo Courtesy of the NYSDEC HAB Photo Gallery

Photo Credit: Jennifer L. Graham - USGS

Image Courtesy of the Northeast Climate Impact Assessment (Maine Summary).

Photo Credit: Ray Yeager

This Storymap was made using ESRI

This map shows the density of common loons surveyed in 2018. Explore the map using the +/- arrows in the lower right. Click on the purple circles for more information.

This map shows potential bloom risk for Maine lakes using the most recently available DEP water quality data (2018). Explore the map and click lakes for more detailed water quality information. If the lakes all appear blue, zoom in further to activate the layer with total phosphorus (ppb). Click on the lakes for additional water quality information.