Tuesday, March 30, 2010

Lake Okeechobee Performance Measure - Diatom / Cyanobacteria Ratio


Lake Okeechobee Performance Measure

Diatom/Cyanobacteria Ratio

Last Date Revised: March 7, 2007

Acceptance Status: Accepted

1.0 Desired Restoration Condition

The target is to substantially reduce the dominance of cyanobacteria relative to diatoms. This can be expressed as a numeric target of having a long-term pelagic ratio of biovolume (diatoms: cyanobacteria) greater than 1.5:1.

2.0 Justification

Studies of phytoplankton taxonomic structure of Lake Okeechobee in the 1970s indicated that the community was dominated by diatoms; today the community is dominated by pollution-tolerant bloom-forming cyanobacteria (Havens et al. 1996). The five-year mean diatom to cyanobacteria ratio for 2000-2005 was 0.63 (SFER, 2006). If phosphorus loads are substantially reduced the percentage of the community comprised of cyanobacteria should decline (LATHROP et al., 1998).

The target of this approach is to reduce phosphorus to reduce the cyanobacteria population. The alternative of increasing Silica to increase Diatoms population is not being discussed. This is an easier solution.

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