This small body of water is in the Bonita Bay residential community in the city of Bonita Springs, Florida. It has been discussed in the first two parts of this presentation. It was artificially constructed as part of a larger hydraulic system intended to manage the surface water of the four-square mile community property. This submission focuses on the details that are the foundation of the recovery.
The feature image shows an alligator taking a closer look at the pond.
The soil:
The base soil type is Anclote and Immokalee Sand and is consistent with the slough which divides the east and west portions of the property. The pond area was a mesic depression prior to development of the property.
The water:
The pond is ground water sourced and linked to the surrounding ponds with underground conduits and to the slough by an above ground weir. This design maintains the water distribution level through a gravity driven cascading water flow. 5.5 million gallons of water is recirculated every day through a series of pumps and filters which supports the water level and provides grey water irrigation throughout the property. These pond hydrologic and geographic charts are from the Lee County Land and Water Survey.
The chemistry:
The ponds are regularly sampled for chemistry and the specimens are sent to the State of Florida for analysis. Here are the results for pond #47 from our BBA Water Committee. The last chemical analysis report on this area was 1/23/2021. Note that the total phosphates and ortho phosphates are elevated above the acceptable standards.
Statement of Pond chemical analysis supplied by Bonita Bay Community Association:
Hydrology, Geology and Biology graphic summary
The microbiology:
A sample of surface pond water in a small area of surface growth these microscopic specemines were found.
These microbiological organisms are normal. The most important finding was the absence of unwanted forms such as cane toad eggs, mosquito larvae, or invasive aquatic plants.
Statement of Pond Condition:
When surveyed on 04/10/2021, the water level was at 0.3 m (NAVD’88) for a water volume of 13,670 m3, a planar surface area of 7,130 m2 and a perimeter of 420 m. The mean depth of the pond was 1.9 m for a maximum depth of about 3.5 m in the central portion of this triangular pond. On 06/19/2021, the water was slightly brackish and hard with an adequate pH. The water column was thermally well mixed and the dissolved oxygen was about 6.9 ppm (adequate level) until about 1 m where a steady drop of dissolved oxygen occurred until it reached anoxia near the bottom (i.e., no dissolved oxygen). The sediment accumulation in this pond was moderately thick with 33% organic content. Based on the nutrients analyses, the pond was nutrients rich (eutrophic). The copper concentration was not determined in this pond. Although there are no standards for sucralose concentrations in the water, based on the range of sucralose concentration found at the BBCA ponds studied, pond 47 was found to have moderate levels of sucralose concentration which ties its nutrient loading to the use of reclaimed water. The pond was surrounded by lawns with some rooted vegetation near the edge of the water. Banks were also quite steep. There were some aquatic plants around the periphery of the pond with a higher density in the northeastern littoral zone which likely limited the nutrient loading into this pond.
Recommended Land management plan:
1. Sediment mapping: map the sediment including thickness and nutrient analysis by depth. 2. Dredging: Not currently necessary but depends on sediment map results. 3. Flocculation: Treat to mitigate nutrients in the water column and in the sediment. 4. Circulation: Not currently needed. 5. Aeration: Not currently needed. 6. Planting: Shoreline shows minor erosion. Verify plant recovery in 2025. 7. Shoreline restoration: Not currently needed 8. Restrict lawn fertilization of neighboring grass and ornamental trees. 9. Advocate reduction in lawn size and support native plant gardening.
The pond was significantly refurbished in 2020. The water level was reduced to 25% of filled. The soil was supplemented and recontoured to eliminate a steep drop at the water line that was the result of erosion. All house roof runoff was diverted by mandated gutters and downspouts. The downspouts were directed underground into the pond. The shores were remediated with contouring, installation of a soil retaining mesh and generous planting of aquatic vegetation at the new shoreline. The pond was allowed to refill naturally. Hurricane Ian, which occurred in September 2022, was a very destabilizing climatic event which significantly altered most of the ponds in Bonita Bay Community. Ten feet of sea water inundated lake #47. The height has returned to normal and the chemistry is slowly recovering. The selected soil stabilizing plant life surrounding the pond was thought to be lost but after two years is now slowly regrowing. The next State reported sampling will be done in 2025.
Summary:
The pond appears to be recovering well from the hurricane event two years ago. The foundation has been well preserved. I expect that the physiology of the ecosystem will stabilize at the levels near those reported in 2021. Sediment mapping is overdue considering the levels of nitrogen and phosphorus. There may be some improvement in the shoreline vegetative growth. It is remarkable that this totally artificial body of water provides so much to help to support all this diverse wildlife. The related sixty community ponds have responded equally well to similar care. This is an excellent example of cooperative natural growth and human intervention to produce a beautiful eutrophic environment.
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#eutrophic #ecosystem physiology #microbiotics #hydrology #geology #nutrients #nutrient rich #phosphates