It's late spring in Central California's wine country, and the wedding is just a few weeks off. The former cattle ranch now owned by a well-known film and television star has been transformed, with a slate-roofed chateau suitable for the Loire Valley of France sitting above a sweeping lawn which goes all the way down the hill to the edge of the 2-acre lake. For the sake of his bride-to-be, an entertainer of even wider renown, an extensive private vineyard has been planted which runs from half the lake's edge up over the surrounding ridge line. One day, these chatelaines will be able to serve their own vintages to their guests.

It's a seeming paradise, but trouble is brewing in the depths of the lake. Over the past year or so, the rancher's former bass fishing pond has absorbed fertilizers, herbicides, and pesticides, as well as some unburned hydrocarbons, all by-products of construction, landscaping and the new agricultural venture. The weather is increasingly warm, which causes the temperatures of the surface and the bottom to vary widely.

One morning, the couple is talking with the caterer, and notices some patches of filamentous algae around the edges of the lake, which have seemingly appeared overnight. Oh well, it can always be scooped out, or something, except that the patches continue to grow over the next few days, as the weather warms. The actor is alarmed to see that a couple of the smaller bass are now floating belly-up, and some of the larger ones seem to gulp air at the surface. In the years he's owned the place, he's never seen this kind of thing.

It can't be passed off as a humanitarian project to develop sustainable protein sources for the third world from the algae; you know, like Paul Newman's salad dressing, strictly a charitable venture. No, the dead fish would blow that move. Even if they could be scooped out, the miasmic odor of rotten eggs rising from the lake would clash with the caviar and other culinary delights planned for the occasion.

What can they do? Do what has benefitted hundreds of decorative lakes for housing developments, resorts, private estates and corporations, golf courses, and agricultural operations. Call the Pond Scum Patrol -- aeration and lake ecology specialists.

Recognize the Environmental Factors and the Symptoms

Although the story above is slightly fictionalized, it's fundamentally true. In more than a dozen years of direct experience in treating lakes, ponds, and other water features, we have seen a wide range of problems, and identified a myriad of contributing factors and causes of those problems. We could never say we've seen it all, though, because each body of water develops its own personality, its own ecology, just as every individual human does.

Why does a lake which has never had problems before suddenly develop them on a massive scale? Well, why does your teen-ager develop acne, or suddenly start bringing home poor grades? While it's possible that your real child was abducted by aliens and replaced with a changeling with a passion for body piercings and unfiltered cigarettes, it's more likely that environmental influences, nutrition, oxygenation, and the simple evolution of maturation can provide many of the answers, for a pond or a person.

In the case of our semi-fictional ranch, the small lake in question had developed its own ecology over the years, as any body of water left to its own devices will do. There were some reeds and rooted weeds at the edges, ideal for the bass the rancher had stocked. A healthy sludge layer was full of microorganisms, worms, and crayfish. Nutrients from transient waterfowl and decaying plant matter were consumed by all those beneficial life forms in the primordial ooze and the plants in the littoral zone around the edge.

When the environment changed, as a result of extensive construction, new landscaping and the planting of the vineyard, the ecology of the pond changed. Winter rains had poured quantities of phosphates, hydrocarbons, and other nutrients into the water. Most of this material sank into the sludge layer, where it would normally be consumed by all those beneficial life forms, although it might take some time because of the sheer quantities.

Unfortunately, as happens in bodies of water deep enough that sunlight doesn't penetrate all the way to the bottom, the increasingly warm weather warmed the surface layer of the lake to a temperature more than 3 degrees Celsius above that of the benthal layer, just above the sludge. A thermocline formed an impenetrable cold layer which prevented natural movement of water between the surface and the lower layers. This condition is called thermal stratification, and is the greatest single cause of the eutrophic conditions indicated by heavy algae growth and fish kills.

Because the vast majority of dissolved oxygen (DO) recharge in a body of water takes place at the surface, through wind and wave action, the thermal stratification meant that the water in the lower levels of our small lake wouldn't eventually rise to the surface and be recharged. The life forms in the sludge, the benthal and other layers below the thermocline would have busily been consuming nutrients and each other, as the food chain progressed, but those processes require oxygen.

The mere presence of certain chemicals, or metals like iron and manganese, consumes oxygen, as those chemicals or metals are oxidized. The combination of chemical substances and life forms creates a Biochemical Oxygen Demand (BOD) which must be met in any body of water, just as oxygen is required to burn the fuel in our bodies.

A lake is not tractable to persuasion. In a sequestered body of water, especially one without natural inlets and outlets, when thermal stratification or nutrient overload occurs, the lower levels in the water column are rapidly depleted of oxygen.

When the environment changes as a result of extensive construction, oxygenation, the simple evolution of maturation or new landscaping, the ecology of ponds change as well. Each body of water develops its own personality and its own ecology just like every human being.

The organisms which consume the oxygen die. In many cases, this can go right up the food chain to the fish, resulting in large-scale fish kills. Fish generally prefer the cool depths of a pond or lake. If they're at the surface, gulping air, you have a good indication of a serious DO problem.

Like gasping fish, or outright fish kills, large filamentous algae blooms are a symptom of thermal stratification and/or significant oversupply of nutrients. Eutrophic actually comes from Greek words meaning "well-nourished", but eutrophy in a pond or lake is an unpleasant condition which indicates the BOD of the water body is not being met. There are simply too many nutrients. In addition, DO levels of below 2 parts per million in the benthal layer can cause nutrients (chemicals, decaying organic matter, etc.) to be released into the water column, increasing the nutrients for the filamentous algae.

The rotten egg smell, produced by hydrogen sulfide and propelled by methane gas, is most often the result of decaying organic matter in a body of water. It's also a symptom of a serious ecological imbalance.

If your 10-year-old comes out from behind the garage looking greenish and smelling of burned tobacco, it's a safe bet there's been some experimentation going on. Odor and color, as we've noted, are a couple of the things anyone responsible for a lake or pond needs to be on the lookout for.

No Predictions Are Possible

Let's say you're starting fresh, with the construction of a brand-new lake. Better yet, for purposes of our discussion, the construction of a pair of lakes, of similar size, and in close proximity. They're dug out, lined with an impermeable membrane of PVC or a special rubber compound, and even equipped with state-of-the art aeration systems.

Without a doubt, in a matter of days, weeks, or months, life forms will begin to take hold. In some locations, the transformation of the pond may take years, but it will happen. Many organisms might be brought in by birds, particularly migrating water fowl. Many are windborne, as spores or seeds, for example.

Of course, these evolutionary developments are on-going. New things will move in, sometimes displacing life forms which have been there for a long time. Not only that, but the two lakes in close proximity, of similar size and depth, may very well develop quite different personalities. One may be more subject to small, nuisance algae blooms, the other may not.

Oregon nurseries must recapture their irrigation water. The nursery above illustrates how nutrient overloads, limited exchange of water between surface and bottom and lack of oxygen produces eutrophic conditions. A small housing development, below, and a golf course drains into this lake in Oregon.

Why? It's as well to ask why two brothers (or sisters) can turn out so differently, one obtaining a Ph.D. in physics from Cal Berkeley, the other playing tambourine with a street band in North Beach, even though they grew up in the same home, with the same set of parents, and are close in age. Sometimes, the difference is just unexplainable.

In our years of treating problems with bodies of water, large and small, the best that can be done is to understand the many factors affecting lake and pond ecology, and undertake a logical form of treatment, or, in the case of planning and building new water features, preventive measures. It may seem like the Pond Scum Patrol emerges from the nearest phone booth in full super-hero attire, and flies without assistance to combat the problem, but it rarely works like that.

In fact, a Patrol member is much more likely to be found wading up to his chin in a golf course lake full of algae, in order to break a path to lay the air-diffusion tubing, because the algae is so thick that even keel-weighted tubing won't sink. Or using square shovels to paddle a dinghy around a pair of decorative lakes for a very upscale estate development in the Santa Monica Mountains. The shovels were necessary because rooted water weeds had grown up from depths of eight feet or more, and the propeller of the electric trolling motor which is usually more than sufficient to unreel tubing or drop in aeration disks kept fouling every couple of feet.

A Word About Aeration

The goal of aeration should be to promote consistent dissolved oxygen (DO) levels throughout the water column, bring the temperatures of the surface and the lower levels more closely into balance, and prevent thermal stratification. Some delivery systems inject air and oxygen into the water, and a certain amount of oxygen transfer may take place during this process.

However, it's important to remember that the majority of oxygenation takes place at the surface. Therefore, the strategy is to move the water from the benthal layer, just above the sludge, to the surface, and let that newly oxygenated water return to the lower depths. This is called "turning" the water, and systems for a given body of water, generally based on depth and volume, should be designed to turn all the water in the lake or pond a minimum of 8 times per day.

On very large and relatively deep lakes, a minimum of 4 turns per day might be sufficient, but the difference is a matter of experience. In any case, it's extremely important not to disturb the sludge layer while bringing the water to the surface. Roiling the sludge will inject nutrients into the water column, and disturb water clarity, as well as the organisms which live there.

The BOD of each body of water must be met, and usually eight or so turns per day should be enough. Understand that, just on a standard golf course lake of an acre or so, for example, it's usually necessary to move more than 20 million gallons per day from the bottom to the surface in order to achieve that number of turns.

It's also necessary to consider environmental factors: how is the lake situated? Are fertilizers and other nutrients likely to drain regularly into the pond? Will there be fish? Are waterfowl, like coots, ducks, and -- worst of all, from a biological load perspective.

Other factors which can affect the ability of an aeration system to be effective are depth and design of the water feature. A depth of six feet or more throughout most of the lake is optimum, in part because of cooler temperatures at the lower levels, and less likelihood that sunlight will penetrate to the bottom, encouraging the growth of rooted plants.

Another aspect of depth, as it applies to lake design and aeration equipment, is that relatively level lake bottoms are desirable. Because aeration, and the movement of water molecules to the surface, only occurs from the point of bubble release upward, holes deeper than the rest of the bottom can become under-oxygenated nutrient sinks. The Prairie Farm Rehabilitation Administration of the Canadian government recently completed an extensive study which confirms this fact.

In the last decade or so, many lake designers, particularly for golf courses and recreational areas, have designed lakes with relatively shallow shelves around the edges. This has been done for safety reasons, to prevent golfers and children from drowning. It should be recognized, however, that shallow areas, where the sunlight does penetrate, are ideal for filamentous algae growth. Your aeration system might be working fine throughout the whole body of water, but that filamentous algae around the edges may make you think it's not.

However, a relatively shallow shelf area might be constructed with the idea of creating a littoral zone, of rooted aquatic plants and reeds. These plants can be excellent water filters, and provide habitat for a number of beneficial life forms.

An example of how a littoral zone, and the treatment of a lake as an ecosystem, a living organism, could be of benefit is the case of a corporation headquarters in the upper Midwest, which has quite a large lake in front of its headquarters building. Only lawn surrounds the lake. No beneficial life forms are encouraged. An aeration system was installed to get rid of persistent filamentous algae blooms. It succeeded for a time, but because there were few desirable organisms present, and the aeration system wasn't maintained, nature filled the vacuum with a pernicious water weed which is just as unsightly as the algae.

Learn to recognize the symptoms. Adopt preventive measures. Treat your water feature like a growing child, or other living thing. Give the Pond Scum Patrol a call, preferably before you need to. Just make sure there's a phone booth nearby.