Alligator ponds have a greater diversity and abundance of plants and animals compared with the surrounding marsh, and offer aquatic refuge in dry months.
Alligators living in Florida marshes create nutrient-rich hotspots that help some algae, plants and other animals thrive.
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| Alligators in Florida help other life thrive Shutterstock/SunflowerMomma |
Animals like beavers are widely considered ecosystem engineers – by felling trees and building dams, they change their environment in ways that benefit other species. But American alligators (Alligator mississippiensis) have rarely been considered for their impact on wetland ecosystems, despite their penchant for making a mark on the landscape. From the mucky wetland slough, the large reptiles use their snouts and tails to dig holes in which they can lounge, mate, eat and stay cool. These alligator ponds dot the marsh, a landscape otherwise dominated by a grass-like plant called spikerush (Eleocharis cellulosa), with watery basins.
“We know alligators are important predators, but we really don’t have any idea if these ponds are important at the landscape level,” says Bradley Strickland at the Virginia Institute of Marine Science.
While a PhD student at Florida International University, he wanted to to see if and how alligator ponds influenced the surrounding marsh and its biodiversity. So, he and his colleagues took a close look at 10 of these basins in South Florida’s coastal Everglades. They assessed the types and number of plants, animals, algae and nutrients in three zones: inside the pond, near the pond’s edge and in the marsh.
Overall, alligator ponds had greater diversity and abundance of life-giving nutrients like phosphorus than other areas, and they hosted more creatures, from microscopic zooplankton to largemouth bass (Micropterus salmoides). Small crustaceans like ostracods and copepods were between 30 and 100 per cent more abundant in ponds than nearby. Zones around ponds also had more invertebrates like copepods and aquatic mites compared with the marsh.
Not everything was more abundant in alligator ponds. They hosted fewer plants than areas immediately next to the pond, probably because deep water and disturbance from alligators prevents their growth. The marsh was home to more grass shrimp (Palaemonetes) and creeping water bugs (Pelocoris femoratus), which were largely absent from ponds.
Because alligator ponds often hold water when the rest of the marsh desiccates in the dry season, they can also provide refuge for aquatic species like fish. The discovery provides further reason to value the presence of alligators, which are protected by the US Endangered Species Act, in Florida’s Everglades.
“We know now through this study that alligators are more than just fierce predators,” says Strickland. “They’re ecosystem engineers.”
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