The Indian River Lagoon System (IRLS) extends 156 miles along the east coast of Florida from Ponce DeLeon inlet in Volusia County south to Jupiter inlet in Palm Beach County. The lagoon ranges in width from one half mile to five miles and has an average depth of about three feet.
This estuary has the greatest species diversity of any estuary in North America with over 4000 plant and animal species; 35 which are listed as threatened or endangered. Among these threatened and endangered species are sea turtles and before our study began little was known about the sea turtles found in the southern region of the lagoon.
This project began in 1998 as an attempt to assess sea turtle aggregations in the southern Indian River Lagoon system and is what inspired the formation of Inwater Research Group. Today, we continue to collect data on the relative abundance, size frequencies, feeding ecology and general health of sea turtles utilizing the southern region of the lagoon system.
During this study sea turtles are net captured from an area of the lagoon known as Jenning’s Cove, just south of the Fort Pierce Inlet.
Once a turtle is entangled in the net it is brought on board and measurements and samples are collected.
Tags are applied to the trailing edge of both front flippers and a PIT (passive integrated transponder) tag is inserted under a scale on the right front flipper. Photographs are taken and the turtle is released back to the lagoon near the area of capture. Over 200 turtles have been captured at this study site since 1998 and some of our results have us concerned about the degraded condition of the IRLS and general health of the sea turtles found there.
AN ESTUARY IN CRISIS
What we have found during this study is disturbing; in that 50 to 70% of the green turtles found in the lagoon have a potentially deadly disease called fibropapillomatosis (FP) as seen in the photo below. This disease is similar to the human papilloma virus and is also associated with strains of the herpes virus. It is manifested by cauliflower like, benign tumors found on the soft tissue of sea turtles. In severe cases the tumors can occlude vision to the point that the turtle is unable to forage for food and eventually starves to death. In other cases the tumors are found internally, which can affect normal body function and ultimately cause death.
While some sea turtles are able survive this disease it is clearly symptomatic of an estuary in trouble. Hotspots for this disease are most often found among sea turtles that inhabit degraded bays and lagoons located near densely populated regions. The combination of poor tidal flushing, pollution and high nutrient runoff contributes to the detrimental conditions found at many of these sites. For example, the disease rate among green turtles found by our group in the relatively clean waters of the near-shore Atlantic is less than 3% compared to the high rate we find in the lagoon less than five miles away. A similar scenario is found in Hawaii where green turtles found near the most densely populated islands have a significantly higher rate of this disease than green turtles found near the sparsely populated outer islands.
Inwater Research Group is deeply concerned by how this disease affects sea turtles in the Indian River Lagoon, but this is not just a sea turtle issue. The compromised health of dolphins, manatees and fish inhabiting the lagoon has also recently been reported. This should be alarming to anyone that enjoys the Indian River Lagoon and a rallying cry to stop the further degradation of this enormously important estuary.
We have initiated and continued our project in the lagoon largely with our own funds. Despite the widespread health issues we have found among green turtles in the IRL, this project has been the most difficult to find funding for.
If you would like to support this project and help us learn more about this disease and the sea turtles of the Indian River Lagoon, please go to How You Can Help.