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Ecology

Plants, Animals and Geography

The St. Johns River is home to many hundreds of species of birds, mammals, reptiles, amphibians, fish, mollusks, and more. Some of the wildlife that calls the St. Johns River home includes:

Wading Birds

Great blue herons, great egrets, snowy egrets, wood storks (the only real American stork), white ibis, anhinga (aka snakebird and water turkey), double-crested cormorants, little blue herons, reddish egrets, black crowned night herons, yellow crowned night herons, limpkins, pied-billed grebes, least bitterns, American bitterns, rails, common yellowthroat warbler, red-winged blackbird, wrens, common moorhens (aka gallinules), American coots, wood ducks, water thrushes, barred owls, osprey, American Bald Eagle.

Plants

Cardinal flowers, pickerelweed, spatterdock, alligator lilies, duck potato, maidencane, giant bulrush, jointweed, eelgrass, coontail, alligator weed, aster, mosquito fern, button bush, muskgrass, wild taro, water hyacinth, spikerush, hydrilla, iris, duckweed, water primrose, baby tears, southern naiad, yellow water lily, pond lily, water lettuce, Illinois pondweed, sago pondweed, widgeon grass, marsh pink, dwarf arrowhead, water fern, lizard’s tail, cattail, horned pondweed.

Mammals

West Indian Manatee (aka sea cow), bottlenose dolphin, river otter, round tailed muskrat (aka Florida muskrat), mink, nutria (aka Coypu).

Fish

Pickerel, sun fish, warmouth, bass, bluegill, catfish, mudfish.

Other Animals in the St Johns River Watershed

Wild turkey, white tailed deer, opossum, marsh rabbit, gray squirrels, raccoons, bobcat, gray fox, alligators, turtles, mosquito hawks, dragonflies, frogs, lizards, snakes. The snail kite, a type of hawk, lives around the St. Johns River and has been on the endangered species list since 1967.

Native to South America, the nutria is a large aquatic rat, also known as the coypu. Nutrias were introduced to the St Johns watershed where it out competes native species such as the muskrat and eats much of the native vegetation. The upper St Johns used to be home to the Carolina parakeet, a species that is now extinct. The last known Carolina parakeet in the wild was found near Lake Okeechobee. To control hydrilla, several other species have been introduced, including 2 fly species, a weevil that eats the roots of the plant, and a hybrid Asian grass carp.

Unfortunately none of these strategies have been successful, and in fact, the Asian grass carp that is tiny in captivity was able to grow up to 30-40 pounds after gorging itself on hydrilla and began eating many of the native plants in the water. The possession of hydrilla is now a second-degree misdemeanor in Florida, with violation potentially leading to a $500 fine and/or 60 days in jail. The Nile perch aka blue tilapia is a freshwater African cichlid that was introduced as a sport fish. This invasive herbivore out competes native bass and bluegill. There are several species that are endemic to the St. Johns River or to Florida, that is, they are found nowhere else in the world outside the river or outside Florida. Fundulud bartrami, a minnow like fish (Clifton Springs) and Aohoastracon theiocrenetus, a snail (Sulfur Spring).

There are two mollusks that are endemic to the Wekiva River: the Wekiwa hydrobe and the Wekiwa siltsnail. Lake Jessup has the 6th densest population of alligators in Florida: 21 alligators per shoreline mile. The watershed is also home to the Florida black bear, a threatened subspecies of the black bear. Rhesus monkeys can be seen around some regions of the river. The monkeys were released around the river in the 1920s and 30s as part of the filming of Tarzan movies. Once harvested as a crop, indigo can now be found growing wild in the part of the river.

Geography

The St. Johns River is young, only approximately 5,000 years old. Because the river flows south to north, the southern part of the river is upstream, while the northern part of the river is downstream. Because it drops by only 27 feet over the course of 310 miles (approximately 1 inch per mile), the St. Johns River is very slow moving. The St. Johns River basin covers an area of 8840 square miles and is home to 3.5 million people. The southernmost end of the river is in a subtropical climate while the northern end is located in a warm temperate climate.

The St. Johns River has 3 major tributary rivers: Ockalawaha, Wekiva, and Econlockhatchee. The St. Johns River is divided into three basins: upper, middle, and lower. The river in the upper basin is characterized by indistinct banks, many swamps and shallow lakes. The river in the upper basin is fed by rainwater and some springs. The larger lakes in the upper basin include: Lake Hell ‘n’ Blazes, Sawgrass Lake, Lake Washington, Lake Winder, Lake Poinsett, Ruth Lake, Puzzle Lake, Lake Harney, Lake Jessup, and Lake Munroe. The Timucuan Indians named the St. Johns River Wekiva, or river of lakes, because there are so many lakes found on the river.

The middle basin begins in east-central Florida where the river begins to widen after it is joined by the Econlockhatchee River. The input of water from the Econlockhatchee River causes the current in the St. Johns River to become faster and an increase in flow. The middle basin runs through Ocala National Forest. Lake George, the largest lake found on the St. Johns River, is located in the middle basin. The lower basin is located between Putnam County and the mouth of the river in Duval County. The lower basin begins where the Ocklawaha River, the largest of the St. Johns’ tributaries, joins the river. After the river enters Clay County it averages 2 miles in width.

At Jacksonville the river turns east and meets the Intracoastal Waterway and forms an estuary. This is the only part of the river that flows east. 80-90% of Florida’s fish and shellfish species depend on estuaries for part of their lifecycle. Jetties have been built at the mouth of the river to maintain water depths that would support a major port at Jacksonville. These jetties and the subsequent changes in water flow and depth have lead to massive landscape changes such as the loss and creation of islands.

Much of the St. Johns River is infested with hydrilla, an underwater plant introduced from Sri Lanka. A single hydrilla plant can grow up to 35 feet, clogging waterways and out competing native plants.

Eel grass Eel grass
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