Algae give freshwater clues in the face of sea level rise
The Florida Everglades is vulnerable to the effects of rising sea level. While attempts are being made to restore freshwater in areas where salt water is encroaching on the Everglades, habitats are changing and there is a need for early indicators of sea level rise-induced change to help focus and expedite these restoration efforts. Florida International University biology student Viviana Mazzei is studying the characteristic algal mats (i.e., periphyton) of the Florida Everglades in order to develop periphyton-based predictors of saltwater intrusion. Because the effects of saltwater intrusion are expected to be most pronounced at the ecotone, the area where fresh and coastal waters meet, Mazzei is particularly interested in using the periphyton communities to track the migration of the ecotone further inland as salt water continues to encroach on the southern Everglades.
Periphyton mats are communities of organisms including algae, fungi, bacteria, decaying plant matter and invertebrates, which act as a microecosystem and are very sensitive to the environmental conditions of their surroundings. This makes them great indicators of environmental changes, such as the elevated salinities and phosphorus concentrations caused by saltwater intrusion into naturally freshwater marshes. Mazzei is studying the periphyton along several transects that run from freshwater marshes through the ecotone, and into the coastal mangroves in order to characterize the different types of periphyton, and their algal communities, that occur in each area.
“There are ways to map that now, with aerial photography, for example, but it takes a while to see the effects of saltwater that way,” said Mazzei. “The turnover rate for micro-organisms is so fast that we will be able to see the changes happening in the environment more quickly.”
Mazzei’s work is focused on the algal community of the periphyton, particularly the diatoms. These are single-celled algae with silica (i.e., glass) cell walls that have intricate ornamentations allowing the trained eye to identify them to the species level with relative ease. These organisms are particularly suitable to indicating environmental change because they are sensitive to the slightest of changes in their surroundings and have short life cycles, which allow those changes to be quickly reflected in their populations.
“I’m hoping to identify distinct diatom communities along the freshwater to coastal gradient of the Everglades,” said Mazzei. “Then we can map where those communities are and how they change. We want to identify diatom species that are indicative of the environment in the ecotone. Monitoring these ecotone-indicator species will help us track changes in the location of the ecotone.”
Mazzei is conducing her research as part of FIU’s Florida Coastal Everglades Long Term Ecological Research (FCE LTER) program, which is dedicated to understanding how water, climate and people impact the Everglades. Her research project is funded by The Everglades Foundation’s FIU ForEverglades Scholarship.
Saltwater intrusion delivers coastal water with its unique chemical composition inward to the freshwater Everglades. “We want to see if we can use the diatoms to track that saltwater intrusion,” said Mazzei. “There are ways to map that now, with aerial photography, for example, but it takes a while to see the effects of saltwater that way. The turnover rate for micro-organisms is so fast that we will be able to see the changes happening in the environment more quickly.”
The Florida Everglades is a wetland made up of different ecosystems, including swamps, hardwood hammocks, mangrove forests, pine rocklands and sawgrass marshes. Their interconnectivity makes them especially vulnerable to changes in the environment.
In 2000, the U.S. Congress authorized the Comprehensive Everglades Restoration Plan to restore, preserve and protect the water resources of the Florida Everglades.
Working in the Gaiser Lab for Aquatic Ecology, under Evelyn Gaiser, Mazzei is assisted by a Miami-Dade Country Public Schools (MDCPS) student who won the Research Experience for High School Students Internship, which is supported by the Florida Coastal Everglades Long Term Ecological Research Program. His work on the project will be presented at the MDCPS science fair, exposing the next generation of students to the work.
Alligators dig change
Alligators are one of the Florida Everglades’ most famous predators. They sit at the top of the food chain and influence the world around them by how they hunt and what they eat. But FIU biologist Bradley Strickland believes they also impact the ecosystem from the bottom of the food chain up.
The Ph.D. student is studying how alligators move nutrients in the environment by digging out holes in the wetlands with their snout, feet and tail. Known as alligator holes, they help the reptiles keep cool during hot weather and successfully mate. The holes also store water during the dry season, providing refuge for wildlife that might end up as alligator prey, including birds, fish, insects, snakes and turtles. By examining water and soil chemistry, Strickland is investigating whether burrowing alligators stir up phosphorous and nitrogen found in the soil and distribute these nutrients to other parts of the Everglades through the water, helping to feed organisms at the bottom of the food chain such as algae.
“You are what you eat, so we can sample small fish and aquatic invertebrates and see what the food web structure is like,” Strickland said. “If that structure is different in the alligator ponds than in the surrounding marsh, we can begin to measure what ecosystem-level changes are being made by the alligators.”
Strickland is conducing his research as part of FIU’s Florida Coastal Everglades Long Term Ecological Research (FCE LTER) program, which is dedicated to understanding how water, climate and people impact the Everglades. His research project is funded by The Everglades Foundation’s FIU ForEverglades Scholarship.
Found only in the southeastern United States, American alligators are sensitive to and indicative of changes in the environment. Strickland hopes his research will allow resource managers to better predict the effects of ongoing restoration efforts in the Everglades.