Troubled Waters – Mysterious Wildlife Deaths in Indian River Lagoon

from Wildlife Promise

Areal view of Indian River Lagoon. eutrophication&hypoxia/Flickr

Areal view of Indian River Lagoon. eutrophication&hypoxia/Flickr

It sounds like a scene straight out of a Carl Hiaasen novel – mysterious marine mammal and bird deaths haunting a once pristine South Florida lagoon. A historically vibrant estuary now lined with the carcasses of outwardly healthy manatees and emaciated dolphins and pelicans…and no one seems to know why.

At Indian River Lagoon, this nightmarish scene is real.

An Engineered Landscape

Indian River Lagoon stretches along 40 percent of Florida’s east coast, 156 miles long and encompassing Mosquito Lagoon, Banana River, and Indian River. Its estuarine waters are brackish, a mix of fresh and salt water and support roughly 685 fish species, 370 bird species, and 2,200 animal species.

Like most of Florida’s water ecosystems, Indian River Lagoon has felt the impacts of Florida’s zealous history of development, diversions, and engineering manipulation. As part of the nation’s crusade to control water in South Florida, Congress authorized the Army Corps of Engineers to construct a dike around Lake Okeechobee in 1948. Now, the Corps is required to carefully monitor the lake’s levels and periodically release discharges of nutrient-rich freshwater from Okeechobee to the west (Caloosahatchee River) and east (St. Lucie River), where it eventually enters Indian River Lagoon.

Emaciated pelicans began dying in the lagoon starting in February. Andrea Westmoreland/Flickr.

Emaciated pelicans began dying in the lagoon starting in February. Andrea Westmoreland/Flickr.

These frequent pulses of freshwater – laden with nitrogen and phosphorus – have altered the lagoon’s nutrient and salinity balances, degrading wildlife habitat and fostering algal growth. In 2011, a large algal bloom occurred, destroying 60% of the lagoon’s vital seagrass. Last year, the lagoon was inundated with a brown algal bloom, choking off much of the remaining seagrass.

A Death Trap

To complicate the issues plaguing the lagoon, an enigmatic slew of dolphin, manatee, and pelican deaths have erupted in the last year. Fifty-one dolphins, 111 manatees, and over 300 pelicans have died in the lagoon since last July.

What is even more perplexing is that the pelican and dolphin carcasses found are emaciated, while the manatee carcasses appear outwardly healthy, with traces of the typically non-toxic macroalgae Gracilaria lining their digestive system. A federal researcher with National Ocean Service has recently found three varieties of toxins from microscopic algae that cling to the Gracilaria seaweed, which may be the cause. However, it’s still unclear what algae or group of algae is producing the toxins and how to counteract it.

One thing , however, is certain: manatees and fish have been consuming more of this red drift seaweed — and presumably the toxins that stick to it — since their main source of food, seagrass, has been killed by previous algal blooms in the lagoon.

The St. Johns River Water Management District has committed up to $3.7 million to research the previous algal blooms and help protect the estuary in future.

It is the largest dolphin die-off the lagoon has ever experienced, with this year’s mortality rate already approaching 10% of the 700 dolphins living in the lagoon. NWF Photo by Glenn Watkins.

It is the largest dolphin die-off the lagoon has ever experienced, with this year’s mortality rate already approaching 10% of the 700 dolphins living in the lagoon. NWF Photo by Glenn Watkins.

Wildlife deaths from toxic algal blooms in South Florida are not limited to the east coast. Manatees have had a particularly tough year, with Florida Fish and Wildlife Conservation Commission recording at least 272 manatee deaths relating to red tide off the west coast since January alone. This is the highest number ever recorded.

There are only about 5,000 manatees in Florida.

Let’s Protect Paradise

Since Governor Rick Scott was elected in 2009, Florida’s regulation, conservation, and water programs have suffered severe cutbacks, essentially reversing much of the progress Florida has made towards improving land and water conservation since the 1960s.

If the Indian River Lagoon death trap is any indication, these cuts and poor water management practices have done nothing but dilute the protections meant to guard Florida’s water resources for Floridians and for our wildlife.

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