Orange Lake Fish Kill

Lynn and I rendezvoused at Heagy Burry Park on the south side of Orange Lake for a late afternoon canoe paddle. We headed out straight into the wind for a couple of miles NNE along the open path through dense submerged macrophytes to the edge of the big lake’s open water. She had told me about gobs o' ‘gators on the south side of the lake up in the weed cuts and airboat trails, and I had never canoed around in that part of the lake.

As we pulled away from the boat ramp we noticed a few dozen dead, rotting fish floating in the weeds just off the boat path. Most were a foot or more in length and torpedo-shaped, so I expected them to be bowfin (Amia calva) and/or gar (Lepisosteus spp.) because local anglers often catch and then deliberately kill them, and throw them back in the water. Why do they kill them? When I was a boy, my older fishing fellows insisted that we kill rough fish because that would make room for more eatin’ fish in the lake for us to catch. Sheesh! Anyway, when we pulled over to examine them I was shocked to see they were chain pickerel (Esox niger) instead! We saw one that was easily 18 inches in length, but it sank out of sight when we tried to maneuver it for photography. This other one was only about 14 inches long:


A very few of the dead fish were sunfishes (Centrarchidae), I saw a largemouth bass (Micropterus salmoides) and an unidentified bream (Lepomis sp.), but there were no dead gar or bowfin. The great majority of the dead fish were chain pickerel, a delicious fish that anglers readily keep. Pickerel are among the most finicky of our Peninsular Florida fishes, needing cleaner water and more dissolved oxygen than sunfishes. Could the killer instead be nocturnal dissolved oxygen deficits? Orange Lake and the other large lakes in the Orange Creek Basin are hypereutrophic and have frequent blooms of blue-green algae (Cyanobacteria), dominated by Cylindrospermopsis raciborskii (http://tinyurl.com/ybby3x5). The new satellite images of Orange Lake on Google Earth clearly show a massive algae bloom in January 2008, possibly from “cylindro:”


How about that? A huge algae bloom in mid-winter! Do you think the bloom might extend all the way to Heagy Burry boat ramp by late September? (Or was its photosignature simply not picked up by the next image?) As I have noted before, the lake’s enormous submerged macrophyte biomass also depresses nocturnal oxygen levels. Between macrophytes in the shallows and cylindro in deep waters, there could be a huge deficit of dissolved oxygen just before dawn on a hot summer day like the one we had a few days ago. That could kill a sensitive taxon like Esox, which could be likened to a canary taken into a mine to warn miners of bad air.

Or was the kill caused by a toxin? Cylindro produces cylindrospermopsin, which in sufficient quantities results in closure of public lake beaches in Indiana (http://tinyurl.com/y99uof8). The Indiana group also pointed out that cylindro is positively related to elevated dissolved phosphorus levels, which Orange Lake certainly has. This toxin has been implicated in deaths of mice, cattle, shellfish, fish, horses, sheep, dogs, birds, bats and muskrats (http://tinyurl.com/y85hftl). In humans it has caused skin rash, fever, hay fever-like symptoms, hepatoenteritis and toxic hepatitis (http://tinyurl.com/y85hftl).

Or was the fish kill a result of too much toxin and too little oxygen working in synergy?

Moving right along…

We ran across a couple of patches of yellow water lily, Nymphaea mexicana. I had never seen it before, and I’ve been on a LOT of Florida’s freshwaters taking inventory of plants and such, and was therefore certain it was an exotic. But no, the Center for Aquatic and Invasive Weeds (http://aquat1.ifas.ufl.edu/node/289) lists it as a native of Florida. How could I have missed this plant after all these years of wandering around Florida’s aquatic ecosystems? Egad! Having fewer petals, it is not as showy as its sister species, white water lily (N. odorata), but it does also have a very pleasant fragrance:


At that we turned around and headed slowly for the ramp with the wind at our backs, reaching shore as the sun was setting and a three-quarter moon rising higher. A group of black vultures was coming back to the ramp too, for the snag roosts there. It was a good ending to a fine early fall day.

Orange Lake Island Hopping

Well, I did indeed go to Redbird Island today, and beyond. The canoe route took me along the edge of the marsh east to Redbird Island, then south to McCormick Island, then west to Bird Island, then north, passing by Hixson Island on the way home. I paddled a total of 5.7 miles on glass-flat water under an unremitting sun. Thank goodness for the shade of cumulus clouds, although I should be careful what I wish for. I photographed the headliner white water lily (Nymphaea odorata) today.

There is so much biomass in Orange Lake, primarily in the form of submerged aquatic plants. Yesterday I mentioned hydrilla, and it is indeed dominant, but there is also milfoil, elodea and bladderwort. The latter was blooming today, small yellow flowers, not many of them. This pic gives you an idea of the density of the submerged plants occupying most of the lake:


Such vegetation adds drag to the canoe, making paddling harder but admittedly only by a few percent. To that, however, add the friction from the water lilies and lotus that often must be plowed thru, and paddling gets a little strenuous at times. The yellow water lilies, or bonnet (Nuphar advena), are the worst. Bonnet’s above-water surfaces are turgid and rubbery, making its dense leaves “grab” the canoe’s smooth fiberglass hull.

Another important biomass component is the wide band of floating plants that grow out over the water from the marsh edge. Frog’s-bit and split leaf pennywort form a thin edge at the outer boundary of the mat:


This floral fringe can be up to 150 ft wide altho is usually more like 50 ft. As I paddle along its edge, I imagine submerged alligators lurking under the floating mat waiting to rush out and attack unsuspecting prey as it comes swimming or floating by. I watch the water.

Floating islands and floating chunks of peat are everywhere in the “shallows.” This lake is famous for its floating islands. My first stop at Redbird Island was at a floating peat island only about 20 ft by 30 ft in size. It supported a few coastal plain willows, shrubby, brittle little trees that contained the remains of about a dozen foot-wide stick nests:


Redbird Island is hardly a real island, being a floating marsh with several small to medium-sized floating peat islands embedded peripherally. I do not know how all this floating vegetation and peat is anchored, whether there is solid ground in there or it is just a hill of peat all the way down. Ditto Bird Island.

McCormick Island has a wide band of floating marsh ringing it on the north and west sides where I paddled. Fortunately, I found a place where the band narrowed and I was able to hop off onto a grounded peat island-cum-peninsula. I threaded my way thru thick stems of dogfennel and willow, and then a band of blackberry, to reach the island proper. Breaking thru the brush barrier and into the open shaded cypress forest was a relief.

I got a good first cursory look today at the three islands, and would like to return at least to McCormick Island for a more thorough exploration.

Anybody have any idea what kind of sampling device this is? I spotted two of them along the way. Of course, I did not mess with them:

This weekend's adventures, so far

Yesterday Sleazeweasel, Brack and I went on a mission of biodiversity in an outright act of guerrilla activism, but I can’t tell you about it because Sleaze swore us to secrecy. I can tell you, tho, that it was a highly moral and legal act. I can also say that we must have looked odd dressed in camo and wearing knapsacks as we rode our mountain bikes through a Friday afternoon throng of brightly colored joggers and spandex bicyclists. A few wild men grinned as we rode by, probably thinking we were marijuana growers.

Soon we reached the end of the trail, stashed our bicycles behind a clump of cabbage palms and headed off trail into the woods. Right away we ran into a thick undergrowth of yaupon holly (Ilex vomitoria). This shrub has a long Native American history as making a caffeinated drink and has bright red fruits that winter birds feed heavily on, but to the walker it is a thicket-maker. Twigs and berries and bugs down the back of the neck, spider webs… Oh, did I mention that I forgot to apply mosquito repellant? Anyway, we accomplished our mission and had an aerobic 13+ mile bike and hike trip.

This morning I set off solo in a 13ft canoe out into Orange Lake. I like to hug the shoreline when canoeing big water, so I paddled easterly along the edge of the marsh, only a little south of where I usually walk to the spoil islands. I have to push through the water lilies ahead and to the left:


Along other stretches of this route the water is more open, and I suspect alligators and/or boaters might have something to do with it:


Hydrilla verticillata nearly fills the water column almost everywhere I went in the lake today. Hydrilla is even underneath the extensive stands of American lotus and yellow water lily. You can be sure the hydrilla sucks a lot of oxygen out of the water at night. Floating mats of marsh vegetation center on every higher substrate and grow outward over the water, especially from the lake margin, shading and deoxygenating the waters beneath. I saw only small fish like mosquitofish and bluegill, and only one turtle. I hope their absence was just a hot summer afternoon thing.

As I was drift-paddling along the shoreline I spied a family of pied-billed grebes (Podilymbus podiceps) up ahead foraging around and on a floating clump of pickerelweed. They saw me coming but didn’t appear too awfully frightened, so I took out my new camera and put away the paddle and let the wind push me slowly toward them. They were in an alert attitude as I initially approached, but seemed to get used to me as my canoe slowly drifted past them. It was a family of two adults and three young:


The wind picked up and pushed the boat even more rapidly toward the birds, and I thought for sure they would flush, but no, they just moved nimbly out of the craft’s way, inches away. Here’s the last one hurrying to catch up as I finally passed them all:


Returning to port I opted to steer through relatively “open” water and paddle directly against the wind for another good aerobic workout. The exercise did wonders for the knots around my right clavicle.

Maybe I’ll paddle out to Redbird Island tomorrow.

Revegetating Orange Lake Spoil Islands

An early afternoon thunderstorm Thursday moved quickly over Orange Lake and cooled the air from the high 80s to the low 80s, and that was enough to set me free! I put on swimming trunks, calf-high rubber boots, a tee shirt and hat, and strode off through the lake margin hammock down to the wetland continuum of shrub swamp, dry marsh, wet marsh and thence back uphill in the dense shrubs dominating the first island.



The goal was to plant some early successional tree seedlings on the island. The four islands are created from dredge spoil and are vegetated by invasives, both native and exotic. I had been thinking to make a little project of occasionally walking over to the island carrying plant species that might increase the biodiversity of the island. A small collection of black cherry, sweetgum, cabbage palm and sugarberry seedlings were dug up from my plant nursery and bagged for the trip over.

On my previous trips out there the weather had been relatively dry. The island's “soil” had been dessicated and plants had made a only a modest cover on the ground. I figured the summer rains had softened the ground by thoroughly moistening it, but was not prepared for the rampant foliage I met. Elderberry was flourishing everywhere over the island, not just along the its margin, as were pokeweed, blackberry, fireweed and thistle. Passionflower and peppervine, an odd couple in name only, had spread atop much of the shrubbery.

It was a mess of leaves and green stems that looked like it would shade out my poor little tree seedlings. I would be throwing them to the wolves, I thought, so brought them back home for reconsideration. Methinks I need to carry some serious gardening implements out there the next time, and possibly larger transplants, or just forget it.

At any rate, I have been experimenting with my new Garmin GPS 60CSx, and how it can interface with Google Earth. Here is the track of my 3-hour wander:



I was following the edge of the water along the northeast part of the track when I stumbled upon an alligator nest. Judging by the looseness of the top of the pile of dead vegetation that comprised the nest, I'd say that the last sheaf had been placed there only a short time ago. Oh, it wasn't as if the top was still visibly settling in, it's just that the storm had just beat down pretty hard and yet there was this airy looseness about the nest. Creepy. I remained alert while taking the waypoint and photographs, I did.



Did I ever tell you about the time I was flagging wetlands in Ponte Vedra Beach, FL within The Guana? The Guana River comes out of real old residential development in the form of a manicured, eutrophic stormwater reservoir. It drains into the next, old-but-not-quite-as-old residential development that also uses it for stormwater disposal but has left significant portions of its shoreline wild. There I was along this moderately long wild stretch, making slow time through dense shrubs and intertwined vines and golden orb spider webs, when suddenly an Enormous Black Thing erupted from the ground and bolted straight at me!

In the first half-second I figured out it was either a bear or a feral pig or a mature alligator or the largest indigo snake that had ever slithered over the earth. “Well,” I thought, in the next half-second, “if I think this could be a snake, then it must have scales, and if it has scales it cannot be a pig or a bear, and since this is not the Miocene, it must be a 9-foot 'gator running straight at me! ... I'm gonna die.” But then it suddenly turned hard left and made a beeline for the water, and I realized it had simply taken an established path to the water and never intended to attack me.

Several biologists have observed and recorded instances of startled reptiles heading straight for a person only to continue on their trajectory after the person moves aside. Bruce Means wrote about his experiments on the subject using poisonous cottonmouths. He may have been the first to realize that the snakes were just trying to take the shortest path to the escape pod (lake) and that they were not trying to attack. I believe my 'gator was in that same mode.

Morning Snakes

After spending this morning reviewing the literature on the Southeastern American Kestrel (Falco sparverius paulus) in prep for upcoming field work designed to find nest cavities and foraging habitat, I walked outside to stretch my legs and eyelids:



Then ever so softly I crept over to a marina bulkhead to look down where a week or so ago I had spotted a juvenile cottonmouth (Ancistrodon piscivorus). At first I didn't see a serpent, but as my eyes moved slowly over the tangled marsh vegetation, lo and behold there was an adult moccasin! Unlike the distinctively marked juvenile, this adult was dullish dorsally, dirty yellow below and with a hint of opaqueness to the eyes, so it may be shedding its skin soon:



As I reached out my hand to steady against a utility pole, I looked over and spotted a yellow rat snake (Elaphe obsoleta quadrivittata) an arm's length away amongst my hanging bromeliads:



Aaaahhhhh, with all the rains we are having after so long doing without, the snakes are back in force at Orange Lake. No wonder the red-shouldered hawks (Buteo lineatus) are doing so well here at Sportsmans Cove.