How Green Is My River?
Tom Schrader, Vice President, Friends of the Fox River
Anyone living in the Fox River Valley knows what a hot, dry summer season the region has suffered through this year. Similarly, anyone who has fished or canoed or hiked along or even simply driven across the Fox River in recent days has noticed the incredibly low water levels in the river where many new “islands” of exposed river bottom have emerged as the drought continues. But this summer, more than any other in recent memory, has also seen a tremendous algae bloom on the river that has caused the Fox River to take on a “pea soup green” color that is reminiscent of the Chicago River on St. Patrick’s Day.
I know that as I cross the Fox River every day on my way to work, I’ve been shocked to see the intense, vivid green color of the river’s water. The sight raises a number of questions in my mind: What has caused this algae bloom? Are algae blooms like this natural? Are they harmful to fish? Do algae blooms have any effect on humans? Can anything be done to mitigate them? This article will address some of these questions.
What are algae?
The term “algae” describes a collection of different types of mainly aquatic, generally minute, non-vascular plant species. While the giant kelp of the Pacific Ocean is an alga and is far from minute, the algae we most often see in the Midwest in our lakes and streams (or ponds and aquaria) are members of the Chloraphyta or green algae class. Cyanobacteria or blue-green algae also occur in our area. Being plants (or photosynthetic bacteria in the case of blue-green algae), algae thrive on sunlight, warm water, and nutrients like nitrogen and phosphorous. Under normal circumstances, algae provide food for small organisms including fish and invertebrates and play a vital role in the food chain.
Too much of a good thing!
Under certain circumstances, algae grow profusely. These explosive growth events are referred to as “algae blooms.” This “bloom” phenomenon is what we are witnessing this year on the Fox River. Very favorable conditions have been present this summer for explosive algae growth: lots of sunshine; very low levels of slow-moving, warm water; and plentiful nutrients. These factors have combined to grow a bumper crop of algae in the river. Simply put, Mother Nature has provided ideal weather conditions for algae growth. Man, however, has provided the catalyst to fuel a real algae boom, er, bloom: excess nutrients in the form of nitrogen and phosphorous.
Nutrients like nitrogen and phosphorous enter the river from three main sources: municipal wastewater treatment plants, runoff from lawns and fields, and runoff of “dry-fall” phosphorous from impervious urban surfaces (rooftops and parking lots). The effects of the nutrients introduced by the effluent from wastewater treatment plants have been exacerbated this year by the very low volume of water flowing in the river. Under higher flow conditions, the effects of the nutrients are diluted by the sheer volume of water flowing in the river system. During low flow conditions, nutrients are more concentrated and therefore do a better job of fertilizing the algae growing in the river. Indeed, during low flow conditions in the Fox River, a relatively high percentage of the water flowing in the river is treated wastewater.
Runoff would seem to be a less serious problem (no rain = no runoff) in times of drought. However, when rare rain events do occur, they result in higher than normal concentrations of nutrients (and other materials) being washed into the river than would result from more regularly occurring rains. Infrequent rain events allow the buildup of fertilizers on lawns and fields and dry-fall phosphorous (airborne phosphorous from dust from both distant and local sources which has settled on urban rooftops and parking lots) which are then washed into the river all at once rather than being carried to the waterway more often, but less intensely, by regularly occurring rains. This phenomenon is why you may have noticed that the river seemed to become even greener after the rare rains we had this summer.
Are algae blooms harmful to aquatic life?
Now that we’ve examined some of the reasons why algae blooms occur and why they have been particularly intense on the Fox River this year, what are the potential effects of the blooms on the Fox ecosystem?
As noted earlier, algae utilize the process of photosynthesis to convert energy from sunlight into the chemical energy used to sustain itself. Part of the process of photosynthesis involves the release of oxygen into the environment during the daylight hours. In this case, the algae living in the Fox River release oxygen into the water during the daytime. However, at night, those same algae plants pull dissolved oxygen from the water. When algae concentrations are exceedingly high, wild swings in dissolved oxygen levels occur between the day and night time periods with extremely high (superoxygentated) levels occurring during the day and very low (hypoxic) conditions occurring during the night. If nighttime dissolved oxygen levels fall below critical levels, fish kills can result.
Even if dissolved oxygen levels don’t fall below the critical levels necessary to sustain fish life, the stress put on the fish by the wild swings in oxygen availability leave them more open to disease and infection which also can cause fish kills long after oxygen levels have stabilized. When algae blooms occur later in the summer into the early fall period, as is happening on the Fox River right now, the daily swings in dissolved oxygen that go along with them stresses the river’s fish and degrades their physical condition to a degree that might inhibit their ability to survive the winter.
Do algae blooms have any negative effects on people?
Outside of creating an ugly, smelly appearance and potentially killing fish that people enjoy catching and using for food, algae blooms on the Fox River cost people money and create potential public health problems. Over 250,000 people in the Fox River Valley get at least a portion of their drinking water from the Fox River. The 2004 State of the Fox River Report reports:
High levels of nutrients such as phosphorous can lead to increased algae populations. Increased algae populations, in turn, reduce drinking water quality. More specifically, most of the off tastes and odors that are associated with river water are due to algal biosynthetic compounds such as methyl-isoborneol (MIB) and geosmin. Odor and taste problems caused by algae can be controlled with treatment with carbon; however, it is not (accomplished) without substantial costs incurred at water treatment plants. . . Another unwanted by-product of algae is that they can release algal toxins into the water. High concentrations of potentially toxic cyanobacteria are present in raw water samples and these algae can produce liver toxins and neurotoxins that can affect the heart, brain, and respiration…
What can be done to mitigate the problem?
In the immediate term, we can’t do too much to control the current algae bloom outside of praying for rain…and lots of it at regular intervals. Over the longer haul, we can attempt to influence the conditions that make severe algae blooms possible. Since we can’t control the weather, we need to focus our efforts on limiting the inputs of nutrients, particularly nitrogen and phosphorous, into the river.
As citizens, we can make ourselves aware of the standards that wastewater treatment plants are held to regarding the quality of the effluent they discharge into the river and make sure that our legislators don’t relax those standards in the name of false economic savings.
We can encourage responsible growth in our area and ensure that additions in population are compensated by additional capacity at municipal wastewater treatment plants.
We can make ourselves aware of the types of chemicals we put on our lawns and fields and encourage their responsible, minimal use.
We can control the types of household detergents we use (always buy phosphate free soap) to minimize household discharges of algae promoting chemicals.
We can encourage the elimination of unnecessary dams on the river that provide pools of stagnant, warm water which is perfect for cultivating a bumper crop of algae.
Finally, we can make our neighbors aware of the problems listed above that are occurring within our watershed of which severe algae blooms are a symptom. Increasing awareness among our fellow citizens is probably the best way we can make a difference in improving the health of our river and in improving the quality of life for all residents of the Fox River watershed.
Let’s make a difference!