An invasive species is a plant, animal or other organism that causes environmental, economic and/or human harm when introduced by humans into a new ecosystem from its native or original ecosystem.

Invasive species can displace native species, degrade habitat and the quality of outdoor recreation, harm public and private property, threaten human health and safety, and impact recreation-based economies.

Zebra mussels can alter aquatic food chains by displacing native species. They can clog drinking water intake pipes located in the lakes and increase water supply maintenance and costs. Their empty shells can accumulate and cover shorelines and be a hazard for walking with bare feet. Silver carp can be dangerous to boaters. Boat noise triggers their nervous system, causing them to jump high out of the water and potentially hit water skiers or boat passengers. Eurasian watermilfoil, an aquatic plant, can grow so aggressively it forms thick mats that can entangle boat props.

The rate of species introductions has increased dramatically in the past few centuries, as a result of human activities, such as global exploration, trade, and colonization. Species evolve and disperse naturally, but at a much slower rate without human influence.

Species introduction happens both intentionally and unintentionally. In the late 1800s Federal funding helped to introduce carp to the United States from Europe for their presumed culinary excellence and angling potential. By contrast, ocean going vessels from Europe accidentally introduced the zebra mussel to North America by dumping contaminated ballast water into the Great Lakes.

More recently, zerba mussels have dispersed into inland lakes, largely through the inter-lake movement of recreational and fishing boats. Mussels attach to boats, nets, docks, swim platforms, boat lifts, and can be moved on any of these objects. They also can attach to aquatic plants, making it critical to remove all aquatic vegetation before leaving a lake. Microscopic mussel larvae may be carried in water contained in bait buckets, bilges or any other water moved from an infested lake or river. Click here to learn more.

Only about 1 percent of all introduced species become invasive. Often a lack of predators and disease allow an introduced species to grow uncontrollably.

• Education: The OPA has been educating the public about the threat of Eurasian watermilfoil, zebra mussels, silver carp and other invasive species since the 1990s to prevent their spread. Because fishing tournaments and sailboat races often bring boats from other lakes with known or potential invasive species infestations, the OPA targets these audiences for education through the media.
• Legislation The OPA encouraged the passage of legislation making the transport of aquatic invasive species illegal and punishable by fine. Prior to this, law enforcement officials did not have any authority to remove invasive species if discovered on a boat trailer or prop or to fine the carrier.
• Electric Fish Barrier and Silver Carp: The OPA championed fundraising efforts for the electric fish barrier at the Lower Gar Outlet of the Iowa Great Lakes by raising $700,000 for the project.
• Boat ramp inspection and education: Since 2010 the OPA has cost shared extra Iowa Department of Natural Resources staff to monitor 12 boat ramps in the Iowa Great Lakes.

Follow the Iowa Department of Natural Resources guidelines. Clean your outdoor recreation gear to prevent the introduction and spread of invasive species. Do not release an unwanted pet or fish into the wild. Garden with native species. Learn which invasive plants threaten the ecosystems in your area, and control invasive plants on your property.

Algae are small, often microscopic organisms that use sunlight to feed themselves. They don’t bloom—rather, a sudden increase in the amount of algae found in a lake is known as a “bloom.” There are many species of algae. Not all of them produce blooms.

Some algae blooms can produce toxins that are harmful to people, pets and livestock. Cyanobacteria, or blue green algae, are the most notorious for creating nuisance conditions. They can cause rashes and other symptoms of an allergic reaction. When swallowed, algae can cause stomach upset, or in more extreme cases, liver poisoning or numbness in hands and feet or dizziness.

Excess nutrients in the lake and rising temperatures in late spring and early summer can trigger algae blooms.

Algae in normal amounts are the basis of the food web in the lakes and are essential for lake health. However, excessive algae are not only smelly, unhealthy, and unpleasant for lake users, they can also deplete the water of oxygen, which kills fish and plants.

The OPA is helping to prevent algae through wetland restoration. Wetlands can help slow run-off and absorb nutrients before rain enters the lakes. The OPA has also encouraged lake-friendly living through the use of low-phosphorous fertilizers. The OPA also encourages low-impact development by using techniques such as rain gardens and permeable pavers to help slow run-off.

Swimmer’s itch is an itchy rash caused by parasites that live in freshwater snails and certain waterfowl. When lake water is warm, these parasites can be released and burrow into a swimmer’s skin.

Swimmer’s itch isn’t dangerous. The rash is short-lived since the parasites will die after burrowing under the skin. However, if the rash lasts for more than a week or oozes pus, you should see your doctor.

Avoid swimming in areas where swimmer’s itch is known to be a problem or near the shoreline or in marshy areas, where snails are more likely to live. After swimming, be sure to rinse off with clean water and dry yourself with a towel. Launder your swimsuits often. Avoid feeding geese and ducks along docks and the water’s edge. There is no evidence that waterproof sunscreens are effective at preventing swimmer’s itch.

If you get swimmer’s itch, it’s important to avoid scratching, since this may cause infection. The itching can be relieved in several ways: applying corticosteroid or calamine lotions, bathing in Epsom salts or colloidal oatmeal, and applying cold compresses. If the itching is severe, your doctor may be apply to provide a prescription.

No. Swimmer’s itch is a natural occurrence in aquatic habitats.

West Lake Okoboji is 6.011 square miles in area, and the second largest lake in the state.

On average, the lake is about 39 feet deep. At its deepest, it is 136 feet deep, making it the deepest lake in Iowa.

There is no visible water source for the lake. It’s likely that it gets its water supply from subterranean springs, or underground flow from Center Lake and nearby sloughs.

Yes, though scientists prefer to call this “mixing”. The surface and bottom waters of all lakes mix, but West Okoboji – compared to other Iowa lakes - is unique because it only mixes twice a year, in the spring and fall, because it is so deep, while shallow lakes can mix on a daily basis. During the summer, the lake surface heats faster than the water underneath. Because cold water is denser than warm water, thermal layers develop with warm surface water overlying a layer of cold, deep water. When the wind blows, these layers mix, but not in deep lakes like Okoboji. The upper warm layer is about 30 feet deep and stays stable all summer long no matter how hard the wind blows until fall. Then, shorter days and dropping temperatures cause the surface water to cool and become denser. The denser water sinks, replacing and mixing the underlying water, which mixes its way up to the surface in what is popularly called ‘turnover’. From fall through winter water temperatures stay fairly uniform under the ice- just under freezing. When spring arrives, however, the melting ice cools the underlying water, making it denser, and once again causing it to sink and mix with the bottom water the mixes up to the surface. Each time this happens, the bottom waters bring organic material with them to the surface, in a sense fertilizing the lake and starting a new cycle of aquatic life over. In the

The DNR considers the water of West Okoboji Lake to be exceptionally high quality, and therefore, and asset to the state. In order to protect the quality of the water the DNR has designated the lake as an Outstanding Iowa Water. This protection extends to all of the Iowa Great Lakes and their watershed. To learn more about water quality in West Okoboji, click here.

A mile-thick glacier carved the lake 14,000 years ago. A waterfall on the glacier may have chiseled the lakebed to its depth of 136 feet, or the glacier may have shaped the basin by depositing sediments as it retreated, with glacial ice melting to fill the lake.

According to ecologist Mike Lannoo, there are 62 native species of fish in the lake and 5 introduced species. Twelve species of fish have been extirpated from the lake.