Florida Marsh Exploration. Part I

This is a recounting of the first three exploratory walks into the perimeter of a Florida Marsh located in the Bonita Bay Slough.

Cover photo is a Saltmarsh Morning Glory (Ipomoea sagittat)

This is part of a series of Floridian environments and ecosystems including Wetlands.

Introduction:

The central wetland feature of the Bonita Bay Community property is a slough. It connects the Spring creek at the north end to the Imperial River to the south. I examined maps of this area that predate the roads, rail beds and towns since records were kept. The entire property including the marsh may have been tidal before the current community was built and made an east-west road across the center at the watershed divide. What remains is now a tidal marsh that appears to be otherwise unaltered for at least several hundreds of years and a wooded wetland in the developed community. The city of Bonita Springs and the highway now called Old 41 as well as the railroad bed were placed to avoid these marshes and swamps. In 1952, highway 41 was built and the marsh and lowland to the east of the highway were filled. The natural watershed to the BB community area was compromised. It is now fed primarily by the estuary of Spring Creek, the Imperial River and rainfall. The creek and river continue to accumulate water from the areas east of 41 but there is no obvious westward surface flow between these two streams. Included are some photographs of some of my observations. Irrigation water is pumped from wells east of highway 41 for community and golf course irrigation.

Marsh exploration:

Visit 1.

Level 1 preparation for a walking trip: Action plan with driver drop-off and pick-up points and gear for a walk in the marsh included: bush pants, shirt, calf high waterproof swamp boots, hat, drinking water, cell phone, SLR camera, bug repellent, and sun block.

I began my walk at the south end at the center of the marsh. This was at the beginning of the artificially created east/west roadbed at the watershed divide.(See map) The vegetation was thick and dense, dominated by grasses, low shrubs and herbaceous plants. After two steps the depth of the water rapidly increased. While I was standing in eight inches of water, I probed the spot for my next step with my walking stick. It easily slipped to full 1 ½ meter length through an increasingly viscus mix of water, vegetation, and decayed plant material. I could not find any real hard bottom. I assume that the bottom is peat.

Carefully using my walking stick to test for footing I treaded into the marsh. There were a few areas where the floating vegetation did support my weight. There were some spots where there was soil sufficiently high for secure standing. Avoiding the possibility of sinking into the water and muck to my chest, I cautiously advanced further in a very irregular line about 70 meters into the marsh. It all appeared to be a heterogeneous tangle of a great variety of grasses, ferns, bushes, and vines.

Visit 1.

I expected this area to be filled with wildlife and a variety of plants different from other environments in Florida. I have looked at the slough many times from a raised viewing platform and was always surprised by the sparsity of birds. I expected to see more diverse animals, however, when wading in the marsh I was again disappointed. For ninety minutes of observation, I saw only a pair of red winged blackbirds. There may be extenuating circumstances for this condition. Salt marshes are not known for bird nesting. Birds are concentrated at the Rookery Islands on the southern end of the slough, there may be predators in this northern end which the birds recognize and this results in their avoidance. The density of the dead vegetation or the deadly effects of hurricane Ian storm surge may have caused a die-off of the predated food supply. 

The height of the vegetation was above my field of vision and there was no sign of an animal path or previous human activity. At one spot where the vegetation thinned, I could see the tree line which was approximately a quarter mile to my east. No other landmarks were visible. The abundant plant variety was very diverse; the animal live was not. I was surprised to find very few flying or crawling insects, no vertebrates except for a few birds. At 9:00 AM it was very quiet, no wind, no odor and very hot (38 C, 100 F) with 100% humidity. After 1 ½ hours, aided by my cell phone and dead reconning, I retreated approximately 70 meters back to my start point. I reviewed my findings overnight. The plants which I observed were more typical of a salt marsh. This deserved further investigation.

Previous views during the past years from the observation deck suggested a rich variety of the marsh vegetation. Again, I was disappointed. The slough is filled with dead plant remains secondary to the saltwater infusion of hurricane Ian’s storm surge. Brush and tall grasses are grey-brown and toppled over horizontally to the water line. Some are continuing to sprout and flower but the overall color of the area is greyish brown. 

Visit 2. 

The following day I returned for a second look with the same prep, and made additional photos and notes. The weather was unchanged. The second trip provided additional findings. I saw more feeding birds but none nesting and very few insects. It was especially interesting to watch a great white heron hunting in the depth of the marsh. Previously I saw them only on the shores of more open spaces. In the deep marsh I could see it using all its skills of crouching, deep water wading and stealth. It did indeed catch something, however, the identity was obscured by some green vegetation surrounding the small prey. After I returned home, I ordered a handheld refractometer to check the marsh salinity.

Visit 3.

Same prep was used plus 6 specimen bottles for water sampling The weather was unchanged. The sample times were between 8:45 and 9:30 AM. Water samples were taken at three surface points at five locations using a dip cup. See map in Fig 20. The samples were brought home and their temperatures were stabilized at 72F (23C). Using the handheld refractometer I gauged the salinity of my samples. The findings are reported in table 1.

I also sampled other wetland areas in the community properties to test the salinity at various  locations. See the five locations on the map (Fig. 2). 

Findings:

Also found were numerous plants that were thriving despite the damage caused by the hurricane of 2023. These can be seen in the next posting. Florida Marsh Exploration. Part II

Discussion:

This is a saltmarsh without a north/south flow. The north and south arms of the slough have been blocked by the Bonita Bay boulevard. The two arms were continuous prior to the property development. The obstruction of the continuity has resulted in the formation of two very different environments. The north end of the slough is wide open to the Spring creek which is estuarial. The south end is connected to water retention ponds in the community with an exit to the Imperial River. The retention ponds collect the water which has filtered through the community swamps and wooded wetland. There is a narrow one-way gate that allows a very limited inflow from the river at the south end of the slough. This does not prevent an inflow from a salt water storm surge two feet above the high tide water line. From table 1 you can see a progression of salinity changes. I also learned that trial explorations are important in determining the level of preparation for venturing deep into unknown areas.

Level 2 preparation. for exploration of the marsh

Similar to level 1 preparation but use a kayak as a vehicle and/or working platform.

Level 3 preparation. for exploration of the marsh using a Full Immersion Preparation.

Have a companion. Make an action plan with driver drop-off and pick-up points. Gear should include: Two lengths of 50^ft, ½ⁱⁿ, 4 ply, hemp rope, carabiners, gloves, drinking water, folding knife, 3-meter foldable measuring stick, containers for wet samples, waterproof cell phone or a camera with over and underwater capability. Enter wearing a full 1^mm diving wetsuit, with hood, boots, and sneakers. Prepare to change to dry clothing for an after-extraction at pick-up point.

The rope and carabiners are for emergency extraction. The wet suit is for buoyancy and skin protection. Hemp rope rather than climbing rope because it is less expensive. It is impossible to remove the salt and dirt and it may be discarded after a few uses.

I learned from this experience. The next trip preparation will be different.

Conclusions:

These observations are made during a very small timeline in the marsh and may not be representative of the yearlong parade of conditions. To better understand the marsh, multiple return visits are certainly forth coming. Test other entry points with level one preparation. Test other seasons with drier or wetter conditions. If a Kayak cannot penetrate the vegetation, plan for a level 3,  immersive exploration.

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#marsh #salt water #heron #saw grass #Bonita Bay #slough #Morning glory #salt marsh #salinity #wetlands #Florida

Reference:

Freshwater Systems of Florida, Main M., University of Florida, Gainsville, FL, 2015, http://www.masternaturalist.org