Questions and Answers About Algae

Algae Expert Mark VanderBorgh answers questions from river watchers about algae.

Question from River Watcher Maria Hitt, Morgan Creek:

As I mentioned in my report last month, there is a lot of algae in the creek, a long stringy/hairy brown algae that I don’t remember seeing so much of before. I was also noticing there were NO gilled snails and was reading in the new book on macroinvertebrates that they are quite sensitive and also that they eat algae so I’ve been wondering if there is a connection, what do you think? I would be curious to discuss this.

Answer from Mark Vanderborgh, algae expert:

This sounds like diatoms, which are known as the golden algae.

Some diatoms grow on filamentous green algae and become so dense that you cannot see the green filaments under them. These diatoms are called epiphytes. Other diatoms grow in long filamentous chains, they are slippery to touch and will also be covered with epiphytes.

These are called as periphyton. In slow moving streams both filamentous greens and diatoms get covered with detrital matter and this can give them a hairy like appearance. If the brown floccullent matter easily falls off, it is probably detrital in nature.

Diatoms are the preferred food source of grazers, such as snails. Often, a grazer will only eat the epiphytic diatoms and leave the green filament. Therefore, I do not believe there is a correlation between the stringy hairy stuff and not seeing snails.

Question about copper-colored scum from several river watchers:

From Sandy Bisdee: I monitor the New Hope Creek in Orange county. I hike there, too. I have noticed a spot along the creek where a spring(of sorts) or a run off, comes into the creek and it is growing orange fuzzy looking stuff. It looks different there than anywhere else that I walk. Any ideas? I wondered if there was a garage or house up hill that regularly put something in the ground that filters down…..

From Carolina Environmental Students Alliance team on Bolin Creek: We’ve seen a strange copper-colored growth on a tiny very slow moving sidestream on Bolin Creek. There was a small bit of oily sheen. Is this scum a fungus, algae, or what? Do you know what it indicates? Does it come from natural sources or does it indicate pollution?

Answer from Mark Vander Borgh, algae expert:

I think Sandy’s and the Student alliance team’s questions are the same. It sounds like they are describing iron bacteria. Actually, they are describing the iron oxide deposits that form after the bacteria reduces ferrous iron to ferric iron. The blue oil noted by the student alliance is also a byproduct of iron bacteria metabolism.
Iron bacteria is common throughout the state and is not known to pose any human or environmental health risk. I will attach a fact sheet we created to help address questions about iron bacteria.

Iron Bacteria Fact Sheet

Iron Bacteria (Ferrobacillus, Gallionella, Thiobacillus, Leptothrix and Sphaerotilus) are a group of small (0.5 to 1.5 um), unicellular, organisms which grow in chains and excrete a mucilaginous sheath. (Image 1) This sheath becomes light brown from iron oxide (Fe (OH)3) and appears as a fuzzy coating on any available substrate (Image 2). Iron oxide is formed as the bacteria oxidizes ferrous iron (Fe2) to ferric iron (Fe3). The ferric iron becomes iron oxide when it is exposed to air (O2) and water (H2O). It is the oxidation of ferrous to ferric that produces the energy needed for the bacteria to survive. This makes them autotrophic, or self feeding, as opposed to heterotrophic. Heterotrophic organisms require a food source produced by others, like animals do.

Ecological Implications:
Iron Bacteria can be found in streams, lakes, ponds and ditches throughout the North Carolina. They are indicative of iron rich water, ground water seeps and low flow conditions. These waters are often acidic or in contact with an anaerobic sediment layer because ferrous iron is favored in these conditions. Although unsightly, Iron Bacteria are not known to pose any environmental or human health risk.

Question from HRA Executive Director Elaine Chiosso:

As part of the ongoing TMDL process for Jordan Lake, Michelle Woolfolk asked us to answer some questions about different nitrogen and phosphorus reduction stategy scenarios. The answers she received included a few that seem to indicate that there is some confusion within the stakeholder group about how nitrogen affects blue green algae (some seemed to be saying that phosphorus not nitrogen is the limiting factor for blue-greens). Can you clarify?

Answer from Mark Vander Borgh, algae expert:

It is generally believed that nitrogen limited systems favor blue greens. A great deal of work on this has been done by Val H. Smith. The reason for this belief is that some blue green algae, such as Aphanizominon, Anabaena and Cylindrospermopsis, have unique cells called heterocysts. Heterocysts can “fix” N2, (nitrogen gas as it exists in air) to biologically consumable forms of nitrogen (NOx). Therefore, if they can use nitrogen that other algae cannot, they can out compete other algae when nitrogen is limited. However, that is only one reason why blue greens may dominate an algal assemblage. Blue greens are well adapted to many environments. They regulate their buoyancy and will float to the surface to hog the light, functionally shading out other algae They can store phosphorous, so even when phosphorous runs out, they have their own supply. They thrive in warm water and are the only algae found in the boiling waters of thermal springs. They do not taste good so grazers will selectively other algae eat first. In essence, there are many factors which can lead to blue green dominance of the algal assemblage.

I hope that helps, here are a few other resources that may be of interest.

Question from Lake Watcher:

At Jordan Lake, I experienced this green substance with bad odor, causing burning eyes, on August 14, 2006, up the channel from the dam towards Robeson creek, where the Haw River and Robeson meet. First saw a large green (color of antifreeze) liquid floating on the surface around the exit of Robeson Creek, this was on Monday 8-14, accidently swam in it, stung my eyes and smelled, coated the boat with green particulates. Heard from a friend it had been that same way the previous 2 days. Went back out Fri 8-18, thought it was gone, but when you put the boat in reverse it churned up water from a few feet under that showed the same green color. Areas affect also had green bubbles, on Fri. there were still bubbles but the green color was much less noticable. I did take samples of the water on the Friday. I had initially thought this was a chemical spill, but after looking at the samples I took, I think it could be algae, however I have been going to lakes for years and never seen anything like this at all. Could this be algae?

Answer from Mark Vander Borgh, algae expert:

From the sample of lake water provided, we can identify the organism causing the green color and odor as the alga Euglena. Euglenoids are known to form surface blooms that often described as “spilled paint” for their unusual appearance. Attached is an Algal Information Sheet (.PDF,61KB) to give you a little bit more on their ecology and ecological implication. I think it is worth noting that around the time of this bloom, there was euglena surface film/bloom on High Rock Lake, which was also reported by a concerned citizen…As always, we appreciate your commitment to the environment and maintaining our water quality.

Mark Vander Borgh
North Carolina Department of Environment and Natural Resources
Division of Water Quality
4401 Reedy Creek Rd
Raleigh NC 27607
Phone: (919) 733-9960 ext 239
Fax: (919) 733-9959

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