Okoboji Protective Association

OKOBOJI SHORELINE EROSION

According to the Corps of Engineers and the Department of Natural Resources, Dickinson County Road 230th Avenue holds back water from flowing without restriction over the DNR weir. This leaves the entire Okoboji lake chain higher from ice-out to early summer. During the spring, heavy winds drive waves into Gull Point and other Okoboji chain of lakes shores to further erode our shorelines.

 

 

The photograph to the left, taken in late May, documents the extent of erosion that has eaten away the natural sand beach and tree roots on Gull Point. Each year this erosion leaves less sand beach and fewer trees on Iowa's prized state park and its natural sand point.

 

 

 

 

Residents of Omaha Beach have recently constructed a new rock pile along their once flat, smooth sand beach and point. It is their effort to arrest continued wind and wave erosion caused by high waters in the early spring and summer. Photographs from the 1950s, 1940s, and before show a much larger sand area to the west than presently exists.

 

 

THE ‘TURN-OVER’ OF LAKE OKOBOJI!

Did you know that like our Iowa climate, Lake Okoboji also has "seasons"? During its annual journey around the sun, our earth experiences differences in temperature and day length that cause the seasonal changes we recognize as winter, spring, summer and fall. These changes are also experienced by lakes, and influence the life cycles and ecology of plants and animals that live in them. However, the change in lake seasons of West Okoboji do not have names like ‘winter’, ‘spring’, ‘summer’ or ‘fall’. Instead, the term "turn-over" is used to describe these changes.

What is "turn-over"? Turn-over refers to the mixing of lake water. Most Iowa lakes are so shallow the wind easily mixes- or turns over- the water. Shallow lakes may turn over several times a season or even in a day. But not West Okoboji. Okoboji is so deep (Okoboji is the deepest natural lake in Iowa) it does not mix well, no matter how hard the wind blows! In fact, Okoboji only mixes completely in the spring and in the fall. Okoboji is called a "dimictic" or twice-mixing lake, while the shallow lakes that mix more frequently are called "polymictic", or many-mixing lakes.

How does turn-over happen? Lets begin with summer. During the summer the sun heats the surface water faster than it heats the bottom layer. Warm water is lighter, or less dense, than cold water. As a result, West Okoboji forms stable thermal layers, with the warmest water on the top - about 30 feet deep- and the coldest water at the bottom. In between is a narrow layer of water. No matter how hard the wind blows on a summer day, these layers of water do not mix until fall.

In the fall, the air temperature begins to drop. The surface water begins to cool, and become colder than the bottom layer. As the surface cools, heat escapes and on many a fall day you can see the heat rising as vapor from the lake surface. Fall turn-over is approaching! The water on the surface becomes cooler than the bottom layers. Because cold water is heavier than warm water, it sinks, and displaces the warmer, bottom layer of water which rises to the surface. Fall turn-over has happened!

As the warmer water rises to the surface it brings up nutrients up from the bottom sediments. These nutrients feed fall algae blooms. This is a normal, annual event. The fall algae are mostly the golden-brown kind called diatoms. If you pay close attention, you may a change in the water color to a golden-green-brown. Unlike the blue green algae blooms of the hot summer months, these diatom blooms do not form noxious scums and are in fact quite nutritious and an important source of food for the zooplankton which the little fish eat. Next, the bigger fish eat the smaller fish. Can you understand how the change in seasons is very important to the aquatic food chain of Okoboji?

Over the winter ice forms on the surface. Underneath the ice, the water is the same temperature from top to bottom: just under freezing. The shield of ice and snow does not allow the sun to differentially heat the top and bottom layers as it does in summer.

In the spring the lake mixes, or turns over, again when ice melt causes the surface water to become cooler and denser than the bottom layer of water. Once again, the heavier surface layer sinks and displaces the warmer, underlying layer that rises to the surface bringing nutrients with it. Again, the nutrients brought up from the bottom feed the algae blooms that feed the aquatic food chain.

When summer arrives, the longer days and rising air temperatures warm the surface water, and the cycle begins again. Summer tourists and residents return to enjoy the summer weather at Lake West Okoboji.

- Jane Shuttleworth, Environmental Education Coordinator, Iowa Lakeside Laboratory
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HOW ABOUT THEM "SEAWEED"?

"Seaweed" is the common term for what aquatic biologists call "macrophytes" or "submerged aquatic plants". In this article we will use the term "macrophyte". In Latin, "macro" means large and "phyte" means plant. Biologists invented this term to distinguish these large plants from the other dominant green organisms in aquatic systems, the "micro" algae. Macrophytes are different than algae in ways other than size, however. They have leaves, root-like structures, and stems whereas the algae lack these structures.

The distribution of macrophytes is limited to the shoreline zone of lakes where the water is shallow and clear enough for light to reach the bottom. That is why we see them growing next to our docks and not in the deep water in the middle of West Okoboji.

Nuisance or Benefit?

From a swimming and boating point of view, macrophytes may pose a nuisance. From a fisheries and water quality point of view, macrophytes are a benefit.

Because macrophytes attach to the bottom they help stabilize the sediments and help keep the water clear. Keeping the water clear allows plants to absorb sunlight and produce oxygen through photosynthesis. In addition, the long stems and leaves of macrophytes act like condominiums for literally 1000s of species of algae and tiny animals that live and hide on their surfaces. These organisms are fed upon by aquatic insects, micro-crustaceans, snails and other invertebrates which, in turn, are fed upon by minnows and baby fish, which in turn are fed upon by fish-eating-fish. Macrophyte beds also serve as import fish spawning, nursery and foraging areas. When macrophytes are removed, so is an important the basis of the lake food chain, and there is a decline in water quality and ecological health.

Nature Abhors a Vacuum

By the 1920s macrophytes began a drastic decline. In East Okoboji Lake, for example, 40 species were once described. By the 1970s, only two or three species were common.

Several interacting factors were responsible for this decline. Considered a nuisance, they were often removed by chemical and mechanical methods. Boating destroyed plants, especially in more shallow waters. We also believe nutrient enrichment from raw human sewage, livestock waste, soil erosion and agricultural runoff played a significant role, for at the same time macrophytes began to decline the noxious blue-green alea blooms began to make their annual appearance in our lakes. Blue greens grow rapidly in nutrient rich waters and can out compete macrophytes for nutrients. They also out compete macrophytes for light because they float near the water surface. Blue-greens further benefit from macrophyte removal because without the bottom stabilizing effect of macrophytes, sediments become suspended into the water column. Suspended sediments release nutrients and favor more algal growth at the expense of macrophytes and other aquatic life.
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Eurasian Watermilfoil

There is one macrophyte we are on the look-out for, a non-native species called Eurasian watermilfoil. It grows rapidly in nutrient rich waters and forms thick mats that are truly are a nuisance to boating and a danger to swimmers.

Eurasian watermilfoil can become established in a new lake simply by transport of fragments on a boat propeller. The OPA has been very supportive of state legislation passed to inspect Iowa lakes on an annual basis for this species. This legislation also included an outstanding public education campaign about this plant.

Eurasian watermilfoil looks similar to our native northern watermilfoil. The best way to learn to identify it is to become familiar with all of the aquatic plants growing in our lakes. The OPA encourages you to learn to recognize plants by their shapes and sizes. Eurasian watermilfoil has 12 to 21 leaflets, our native northern watermilfoil has only 5 to 10. If you think you have identified Eurasian watermilfoil, keep it in a bucket of water and call the DNR at the Spirit lake Fish Hatchery for identification verification.

Research indicates lakes with sedimentation problems and nutrient rich waters seem to be especially vulnerable to colonization by Eurasian watermilfoil, so this is another reason why it is so important to protect water quality through creation and enforcement of silt fence ordinances, establishment of vegetation buffers between lakes and lawns, and by supporting conservation agriculture practices. Being a member of the OPA also helps protect the health of our lake!

-Jane Shuttleworth, Environmental Education Coordinator, Iowa Lakeside Laboratory.
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Water Quality

To protect natural lakes and their watersheds in Dickinson County, the Okoboji Protective Association has supported the water quality monitoring programs of Iowa Lakeside Lab and the Friends of Lakeside Lab. Data is collected annually by volunteers through the Cooperative Lakes Area Monitoring Project (CLAMP). See the following links for more information.

Fact Sheets from 1999 - 2006 for West Okoboji and each of the other Dickinson County lakes monitored by CLAMP.

Raw Data for 2005 & 2006 from CLAMP.

Summaries of water quality data for the Iowa Great Lakes for 2003 and prior years, including data collected by CLAMP.

If you are interested in monitoring the health of our lakes, contact Jane Shuttleworth, CLAMP Volunteer Coordinator, at 337-3669 ext. 3 or by e-mail at lakesidejane@yahoo.com.

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How to Control Algae Blooms

Phil Petersen

Our greatest asset in the Iowa Great Lakes area is our lake water quality. It is the driver of our economic engine. An algae bloom reduces our enjoyment of the lakes and is one of those lake water quality distractions we would like to see disappear.

This past August and September we had heavy rains. Just after these heavy rains our lakes had very bad algae blooms. Although it is difficult to pin point the exact cause – and there could be multiple causes – many knowledgeable people feel the heavy rain washed a dry summer’s accumulation of lawn fertilizer into the lakes. It is well understood the major culprit for algae blooms is phosphorus.

Lawn fertilizer is sold with three numbers on the bag; example 15 - 0 - 15. These numbers represent the amount of Nitrogen – Phosphorus – Potassium. To limit the growth of algae it is important to keep the phosphorus – the middle number - at zero or a low level.

This concern over algae blooms is why this winter the Okoboji Protective Association worked with the lakes area lawn care companies and fertilizer retailers this winter to reach an agreement to limit the use of phosphorus on our lawns. The largest and most active lawn care companies have signed a pledge not to use phosphorus, except under special circumstances. They are:

• All American Turf Beauty
• Courtyard Gardens
• Ferguson Garden Center
• Handy Andy Yard Service
• Hassel Landscaping
• Halbur Lawn Service
• Lakes Property Management
• Lakeside Landscaping
• Lohman Landscaping
• Toft Landscaping
• TruGreen Chem Lawn
• Vugteveen Lawn Service
• Whittrock Lawn Service
• 4 Evergreen Landscaping

Under this pledge the limited situations where phosphorus could be used is where soil testing or extensive analysis has shown that phosphorus is required for a healthy lawn. New lawns might require some phosphorus to get started. Only a controlled amount of phosphorus would be used in these situations.

Six local companies do not use any chemicals in their lawn work. They are: Berg Landscaping, Bryan Landscape, DeMuth Landscaping, Great Lakes Lawnscape, Rinehart Landscape, and Cottage Gardens.

Three fertilizer retailers have also signed the limited phosphorus pledge: Ace Fick Hardware – Spirit Lake; Bomgaars – Spirit Lake; Del’s Garden Center – Spencer.

We can all help reduce the amount of phosphorus that finds its way into our lakes by patronizing lawn care companies and fertilizer retailers that will utilize lawn fertilizer with a minimum of phosphorus. By working together we can reduce the number and intensity of algae blooms impacting the Iowa Great Lakes.

To probe further: See website www.okobojiprotectiveassociation.org

Phil Petersen is a Past President of the Okoboji Protective Association.

A Threat Hard to Imagine

It is hard to imagine a biological threat to the Iowa Great Lakes that could severely damage the lakes that modern science couldn’t fix. But that is the situation we face with Aquatic Invasive Species (AIS). The reason they are termed “invasive” is that they have no native enemies and they grow very rapidly. The chemical remedies are so toxic they would probably kill most of the fish and vegetation in the lake and are virtually cost prohibitive - when applied to our size of lakes - that they are not a viable solution.

There are many Aquatic Invasive Species, but the two most threatening to the Iowa Great Lakes are the Eurasian milfoil and zebra mussels. Eurasian milfoil is a thick mat of weeds that can choke a lake to prevent boating, fishing, and swimming. The closest infestation of Eurasian milfoil is in the lakes surrounding the Twin Cities along with small ponds in Palo Alto and Kossuth counties. Zebra mussels have sharp edges that can cut swimmers feet. Zebras also grow so fast they could clog the lake water intake pipes that supply our drinking water. Three years ago, a few zebra mussels were found in Clear Lake. Now Clear Lake docks and hoists are covered with zebra mussels.

For the past three summers, three DNR Water Patrol Officers have been on Iowa Great Lakes boat ramps every day to educate boaters about the threat of AIS. While on the boat ramps these officers are also inspecting boats and trailers for any signs they are carrying AIS. However, with 12 major boat ramps and 3 officers, we are severely limited in our boat ramp coverage.

Volunteers to the Rescue

Last summer the Water Safety Council, along with the lake protective associations, organized boat ramp volunteers to help educate boaters. The major staffing concern for this effort is weekends and holidays when the number of boaters using our ramps increases significantly.

How to Volunteer

1. Contact your Lake Coordinator to provide your name and contact information. The use of email is preferred because it requires less real time contact.
   Alternative: Send email to watersafety@watersafetycouncil.org
2. Obtain your volunteer equipment from the Maritime Museum or DNR Fish Hatchery.
3. When you are ready - contact your Lake Coordinator to advise them the boat ramp and time you will be there.

Lake	2009 AIS Lake Coordinators
West Okoboji	Rhonda Thornton & Emily Schaefer 712-337-8038 emilyschaefer@hotmail
East Okoboji & Lower Lakes	Toby Jensen 712-249-9288 jensent96@iowalakes.edu
Spirit Lake	Dick Ramsey 712-336-5336 rramsay@mchsi.com

Boat ramp volunteers can obtain their volunteer equipment at the Maritime Museum in the Arnolds Park Amusement Park or the DNR Fish Hatchery at 122 252nd Avenue in Orleans.

Volunteers are asked to help educate boaters about the threat of Aquatic Invasive Species for two hours each summer month. Some volunteers may want to contribute more than two hours per month - that is encouraged. The volunteers would also inspect boats and trailers to prevent AIS from entering the Iowa Great Lakes.

Volunteers and interested persons should attend the DNR training session or obtain a copy of the new training DVD. The DNR Fisheries Bureau will provide live training at the date and time below.

Saturday – June 20th – 9 AM – Spirit Lake Expo Building

New for this year - we also have an Iowa Great Lakes boat ramp volunteer training DVD, so it is not necessary to attend one of the live training sessions. If you were a volunteer last summer, this new DVD might be a good way to brush up on your boat ramp skills.

Another new feature for this summer will be a Boater's Map for East Okoboji-Lower Lakes, West Okoboji, and Spirit Lake. The DNR has redrawn their lake contour maps in 3D to include marina locations, hazard buoy locations, and lake features. On the back of the map are Aquatic Invasive Species images and information and a map of car wash locations with high-pressure hoses for cleaning boats. The lake protective associations are paying to print 5,000 maps for each lake.

Some might think educating boaters along with inspecting boats and trailers is a waste of time, since some Wisconsin and Minnesota lakes already have Aquatic Invasive Species. Our experience is that 99% of the boats and trailers coming to the Iowa Great Lakes are free of Aquatic Invasive Species. However, we need to be vigilant for that one percent that could bring Eurasian milfoil or zebra mussels to our lakes. Boater education will pay dividends even when a DNR officer or volunteer is not at the boat ramp.

We have three protection advantages that infected lakes in Minnesota and Wisconsin did not have:

1. We are much further from the AIS sources of Lake Superior and Lake Michigan.
2. Iowa lakes are much further apart that Minnesota and Wisconsin lakes.
3. We have a high percentage of boaters who trailer to the Iowa Great Lakes and do not use other lakes.

Iowa Law on Aquatic Invasive Species

Iowa Code Section 456A.37 paragraph 5 states: A person shall not do any of the following:

1. Transport an aquatic invasive species on a public road.
2. Place a trailer or launch a watercraft that contains, or to which an aquatic invasive species is attached, in public waters.
3. Operate a watercraft in a marked aquatic invasive species infestation area.

The Iowa fine for transporting AIS is up to $500 plus costs.

To probe further check the Iowa Great Lakes Water Safety Council website www.watersafetycouncil.org – click on Aquatic Invasive Species.