August/September 2004
Brought to you by your friends at Alligator Bayou

Living Inside The Basin:

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A Rich, Diverse Ecosystem

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The Spanish Lake Basin teems with wildlife. Egrets and herons lunge for splashing fish and slithering snakes, alligators sunbathe on fallen logs, and red-shouldered hawks soar over the tops of moss-draped cypress trees. It is a habitat with a rich diversity of species. Once regarded as dark and dreary places, wetlands like Spanish Lake Basin are now understood to be precious ecological resources, which nurture wildlife, purify polluted waters, check the destructive powers of floods and storms, and provide many recreational opportunities. For these reasons, many people are taking steps to preserve and protect wetland areas like Alligator Bayou and the Spanish Lake Basin.

The Survival of Species: What Sustains Them?

In the Spanish Lake Basin ecosystem everything is linked. The survival of living organisms depends on the health of the four ecosystems found in the Spanish Lake Basin: 1) the open water of bayous and lakes, 2) swamps, 3) bottomland-hardwood forests, and 4) distributary ridges. Over thousands of years, deposits of rich river sediments produced a unique community of wetland trees and plants. The vegetation feeds and shelters countless numbers of invertebrates, insects, fish, reptiles, birds, amphibians, and mammals, which interact with each other. These plants and animals eventually die and are decomposed by scavengers and detritovores (organisms that consume dead/decaying material, like bacteria), becoming nutrients for the system and thus completing the cycle.

Each habitat, ascending in elevation from open water distributary ridge, is home to interacting vegetation and animals. For example, crawfish hide under rotting vegetation on the bottom of bayous and lakes. Alligators and bulrushes live in the muddy substrate of the swamp. Squirrels, raccoons and opossums nest in the cavities of trees in the bottomland-hardwood forest. They eat the acorns, hickory nuts, pecans, persimmons, paw-paws, and mulberries produced by these trees. Barred owls, hawks and vultures live in trees growing on the distributary ridges. They feed on squirrels, opossums, and other animals living on the forest floor. It is easy to see that the organisms share a tight connection with their environment. Preserving their habitat preserves the Basin’s biodiversity.

The Cycle of Plenty

Hydrologic processes are some of the most important components of the Spanish Lake Basin’s ecology. They constantly enrich the Basin’s cycle of plenty. Soil, nutrients, and animals are carried by water through the Basin’s four habitats, sowing new vegetation, feeding animals and delivering enriched sediments. Small animals carried in the water – like invertebrates, snails and crawfish – are food for frogs, fish, ducks and wading birds like the Snowy Egret and Great Blue Heron. In turn, they are food for alligators and other water and land animals. Because of this abundant food supply, bottomland-hardwood forests, for example, attract two to five times as many game animals and in the wintertime, ten times as many compared to adjacent pine forests.

A Cathedral of Trees

Ranging from the ancient, old growth bald cypress trees on Cypress Flats to sprawling live oaks on the distributary ridge, the bottomland-hardwood forest is another important component of the Spanish Lake Basin ecology. In spring and early summer, hardwoods produce flowers that support insects and the majority of wildlife. During the rest of the year, the same hardwoods produce fruit, berries, nuts and acorns that support the seed-based food chain. Known as “mast,” this is a reliable, year-round food supply of waterfowl and wildlife. In the uplands, mast feeds mammals. Washed by rain into lakes and bayous, it feeds ducks. Dependable food sources such as mast form a base of the complex and highly productive swamp food web, detrital material being the other important base.

Of the many species of trees growing at Alligator Bayou and Bluff Swamp, the area is perhaps best known for the giant bald cypress trees, which are believed to be between 800 and 1,200 years old. Some are astonishing to behold. They are immense in size – 36 feet in circumference, with 12-foot-tall cypress knees! The heat and typically abundant rainfall lengthen the growing season, and along with the flooding-dewatering process, create these towering, primeval giants.

A Paradise of Birds

Serving as a bird refuge is one of the most important ecological functions of Bluff Swamp and the Spanish Lake Basin. The Basin is the refuge and nesting site of 250 to 285 species of birds, which either inhabit the area year round, during winter, or only during migration. More than 150 species of birds permanently reside in the forests of Bluff Swamp, and, on any given day, a birdwatcher may spot as many as 50 species in the woods alone. In addition to the resident birds, the Spanish Lake Basin plays host to thousands of birds migrating between Canada and Central/South America. They follow the Mississippi River’s air currents and vegetation. Before crossing the Gulf of Mexico, many species of migratory birds land in Bluff Swamp and Cypress Flats to spend days or weeks replenishing their reserves. The Bluff Swamp-Spanish Lake area is one of the dwindling number of undeveloped refuges left for these migrating species. Without the ability to store reserves, many birds would not be able to traverse the Gulf of Mexico. This would certainly impact the species.

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