By Kedric Nutt

During the warm season, ponds and lakes commonly get choked up with grass, moss, slime, weeds - whatever you call it - it can be a mess. It can make fishing unpleasant or virtually impossible. The most common weed problem this time of year is not really a weed - it is an algae. Algae can be single or multi-cell forms which float freely in the water - known as phytoplankton - or they can be long, stringy chains of cells known as filaments. This last form is called filamentous algae.

Many different species of filamentous algae commonly grow in southern ponds and lakes. Most of these are easy to control while some are rather tough. However, all the native types can be controlled or eradicated with normal integrated management - a combination of fertilization, grass carp and herbicides.

However, a new and terrible scourge is making it's way across the south and this is the time of year when it becomes noticeable. Be on the lookout for a filamentous algae which looks like none you've seen before. It typically grows in large, solid mats and is most distinguishable by it's dark color - it usually appears nearly black. This filamentous algae is an exotic species which, although not yet officially assigned a scientific name, is known as Lyngbya woolii.

Lyngbya woolii is in the blue-green algae group, named for the dark, blue green color of the cells and filaments. Lyngbya woolii is actually blue green but is so dark that it appears black to the human eye. The texture of this algae is responsible for the name. It is extremely coarse, rough to the touch, fibrous and tough - much more so than any other filamentous algae. A handful is tough to pull apart into fragments. It also has a sheath which surrounds and protects each filament.

One other very distinctive characteristic is it has a strong, earthy-musty, 'pond water' odor. This is from the same chemicals (geosmin and MIB), produced by the algae, which gives catfish what is known as 'off-flavor'. This is sometimes detectable through the air around the pond.

The problem with Lyngbya woolii is that it is not sensitive to our aquatic herbicides. None of the EPA approved aquatic herbicides are highly effective at killing this algae. Heavy, strong doses can temporarily kill it or 'burn it back'. However, it typically grows back in 2 to 6 weeks and requires repeated treatments for adequate control - 'chemical mowing'. The other difficulty is that the legal aquatic herbicides have no lasting or residual effect.

Even large organizations, with significant resources, like Alabama Power, the TVA and some large research Universities have not been able to determine an effective control for this algae.

As with all weeds and algae, water depth is a limiting factor on Lyngbya woolii. It does grow in fairly deep water, compared to other algae. We have observed it growing in 5 to 6 feet of water, even in the presence of a good plankton bloom. This emphasizes the importance of minimizing shallow areas in your pond during construction or renovation. Also, it underlines the importance of establishing a good plankton bloom as early in the spring as possible.

It is apparently impossible to eradicate this algae once it is established. No field experience or research results have reported success at eradicating Lyngbya.

As far as achieving consistent control, we have had moderate success with an aggressive plan of heavy fertilization, a high stocking rate of grass carp (20 to 30/acre) and regular herbicide treatment as needed. It becomes a process of containment and control, but not eradication - much like Kudzu.

What can a pond owner do to protect their pond or, at least, reduce the chances of infestation ? Given that the source of the introduction is most likely waterfowl (ducks, wading birds like herons, cormorants, etc.) or other varmints, not much, unfortunately. A pond is an ecosystem which is open to the environment. You cannot control - completely - what gets in. Lyngbya also reproduces by hard spores - essentially seeds - which may become air borne.

However, if you fish from a boat, wash the boat and trailer before launching in your pond or any other lake. Be careful to remove even the smallest fragments from the boat and trailer. Drain water from the livewells and bilge before launching the boat. Also, if you fish in a pond with a particularly tough and dark colored algae, clean all fragments from your gear before fishing in your pond or another lake.

Be on the lookout, early detection and early treatment can help control and may prevent this problem algae from developing into a full blown infestation.

Kedric Nutt is a fisheries biologist with Southeastern Pond Management. He works in the company's Opelika office.