Phosphorus Problem in Lake Istokpoga?

By Bill Dwinell

While it may be to early to raise the alarm flag, it isnít to early to raise the caution flag. At the September meeting of the Lake Istokpoga Management Committee (LIMC) Dr. Jennifer Brunty, Natural Resource Specialist, Highlands County Soil and Water Conservation District, reported that recent tests of the water in Lake Istokpoga indicated that high levels of phosphorus (300 parts per billion (ppb)) were entering the lake from Arbuckle Creek. Further tests at S-68 indicated that 40 ppb of phosphorus (P) was measured leaving the lake. It doesnít take a scientist to figure out that this means 260 ppb of P is staying in the lake. Please refer to Istokpoga Newswire article "Can Lake Istokpoga end up like Lake Okeechobee" in the March 2001 edition (also available on our web site) for more information on what this could mean.

Now is not the time to get upset, but it is time to start looking for the reasons for the high amount of phosphorus entering our lake. According to Dr. Paul Parks, Florida Wildlife Federation, "In my view, 300 ppb phosphorus coming into Lake Istokpoga is very serious. If inflows continue at this level, it is only a matter of time until there is a much more serious eutrophication problem in this lake."

What is already being done?

According to Clell Ford, Highlands County Lakes Manager, the county is looking into the problem on several fronts:

Clell Ford also stated "We must, are and will continue to address the serious issues surrounding water quality in Lake Istokpoga. Yes, more phosphorus is entering Istokpoga than is leaving it, the balance evidently being sequestered in growing plants, plant islands and decaying muck. Evidently, investigations into nutrient sources in the past have not resulted in a positive impact to Istokpoga. Such a result in the future will be unacceptable. Long term, sustainable solutions that provide incentives for cooperation, as opposed to quick solutions that assess blame, are the only realistic hope for reducing nutrient loading in order to improve, protect and preserve Florida's 5th largest lake.

We can also thank the lake restoration for helping us with our phosphorus problem. According to Beacham Furse, FWC and Project Manager for the restoration work, there is an estimated 187 tons per tussock-acre, of which 0.1687 % is P, or approximately 0.3154 tons P per tussock-acre. With an estimated 1308 acres of shoreline that amounts to 412.6 tons of P removed from the lake. While some small amount of this may leach back into the lake from the in-lake islands that were created, Dr. Jennifer Brunty stated "We can't really know a leaching rate without doing a whole study next to some islands, but I think that since the interior of the island will be under anaerobic conditions only the top 6 inches or so will be leaching nutrients to the water. Organic matter decomposes poorly under anaerobic conditions - which is why they find these 500 year old canoes under muck and semi-decomposed organic matter."

Where do we go from here?

The amount of phosphorus entering the lake is high enough to be a serious problem. While 300 ppb is high, it is not so high that we canít fix it, and it will not destroy the lake in the immediate future. If we were to take no action, in the years to come our beautiful lake would gradually die.

It will take time to pinpoint the source of the phosphorus. Likely candidates are dairy farms or other agriculture interests along Arbuckle Creek. Water treatment sites are also places to check. This will likely take several months of data.

According to John Morgan "the District has funds budgeted for FY02 [full year 2002] to conduct an assessment of Lake Istokpoga sources and sinks for phosphorus. The details of this project have not been fully defined as yet, so we have an opportunity to develop the scope to meet multiple needs."

We will continue to work closely with the county and SFWMD to isolate the source of this problem and then take action to eliminate the phosphorus pollution..