By: Zack Jud, Ph.D.
“Algae.” It’s everywhere lately. In the St. Lucie River and the Indian River Lagoon (IRL). On our beaches. All over the national news. But what do algae blooms mean for those of us who find our happiness out on the water? As anglers, we have some major concerns regarding algae blooms in our home waters. What are the short-term and long-term human health issues associated with algae contact? What will happen to the fish we love, and the aquatic ecosystems they rely on? How will our fishing-based economy be affected? Sadly, the answers to these questions aren’t immediately clear, even to experts in the field.
First off, not all algae are harmful. In fact, some species are an important part of healthy IRL ecosystems. However, when microscopic planktonic algae begin to grow out of control – growth that is usually triggered by excessive nitrogen and phosphorous in the water – we can end up with harmful algae blooms. The nutrients that trigger algae blooms can come from a variety of sources, including agricultural fertilizer, herbicides, livestock waste, residential fertilizer use, septic tanks, and the nutrient-rich muck covering the bottom of the IRL.
Harmful algae blooms have been occurring in the IRL for decades, but the issue really came to light with the 2011 “Superbloom.” As a result of the Superbloom, and other subsequent green and brown algae blooms, the IRL has lost more than 47,000 acres of critical seagrass habitat. Sunlight can’t penetrate the green and brown pea-soup water, causing seagrass to slowly “starve” to death. The seagrass meadows that once blanketed the bottom of the IRL not only provided habitat for countless species of gamefish, forage fish, crustaceans, and mollusks – they also anchored the lagoon’s sediment in place, reducing the effects of wind and wave action on water clarity. The health of our fishery depends on the health of our seagrass – which in turn is intrinsically linked to water quality, nutrient pollution, and algae blooms.
Although the green and brown algae blooms that are wreaking ecological havoc on the IRL are not considered toxic, they can have lethal effects on fishes and invertebrates. When an algae bloom dies off, bacterial decay of the dead algae can cause dissolved oxygen levels in the water to plummet, oftentimes resulting in fish kills. The catastrophic fish kill that wiped out of millions of fish in the northern IRL this spring was attributed to a brown algae bloom that suddenly collapsed. Within two days, oxygen levels dropped to the point that fish began to suffocate. Widespread fish kills can have long-lasting effects on our fishery, particularly when large breeder fish are involved.
The green and brown algae blooms that occur in the IRL contrast sharply with the toxic blue-green algae bloom that has been devastating the St. Lucie River in recent months. The blue-green algae (also known as cyanobacteria) that is causing this bloom naturally occurs in freshwater – not brackish estuaries. This spring, an enormous slick of floating blue-green algae began to grow on Lake Okeechobee. As of early July, the bloom covered an estimated 200 square miles of lake’s surface. Sadly, the mismanagement of Florida’s surface water flow by the US Army Corps of Engineers is allowing this floating mat of toxic green slime to be carried out of Lake Okeechobee, through the C-44 canal, and into the St. Lucie Estuary. At times this spring, the Army Corps released as much as 4 billion gallons of Lake Okeechobee water – along with its film of floating algae – into the St. Lucie River each day. In addition to turning most of the St. Lucie Estuary bright green, wind and tide have occasionally pushed the floating green particles into the IRL and onto local beaches. Even without the accompanying toxic algae, massive discharges of freshwater out of Lake O represent a huge threat to the health of our estuaries. Add blue-green algae to the mix, and we’re looking at an ecological and economic disaster for our region. The toxic chemicals that are produced by this type of blue-green algae – known to harm the brain and liver – may stick around in our environment for years to come. Only time will tell.
So how do we slow the flow of freshwater and toxic blue-green algae that’s pouring into our estuaries? Although the problem is complex and multifaceted, the only true option for eliminating coastal discharge of water from Lake Okeechobee is the creation of massive engineered filtration marshes in the Everglades Agricultural Area south of Lake Okeechobee. Converting sugarcane fields into filtration marshes will allow water to flow out of the big lake and towards the Everglades and Florida Bay, where it is desperately needed. Along the way, aquatic vegetation in the man-made marshes will use up phosphorous and nitrogen, creating water that is clean enough to sustain the health of the Everglades. Although Lake Okeechobee is clearly the smoking gun here in the Treasure Coast, we can all help to improve water quality locally by limiting fertilizer use, especially during the wet season, ensuring that septic tanks are functioning properly, and keeping grass clippings and pet waste out of canals and waterways.
As anglers, all hope is not lost. Algae blooms are not affecting every square inch of our local waterways. There’s clean water and fish to be found – just get out and explore! Areas of the Indian River Lagoon to our north and south have been fishing well, and summertime sight fishing for beach snook is in full swing. While the discharge plume from the St. Lucie Inlet has been spotted as far as six miles offshore, with a little bit of running, clean water is easy to find. The decision to fish in areas where visible blue-green algae is present is up to you, but keep in mind that the health effects associated with blue-green algae toxins might not be apparent for many years to come.
Zack Jud, Ph.D., is the Director of Education at Florida Oceanographic Society. He is a coastal ecologist (researching tarpon, snook, bonefish, permit, and lionfish), a marine science educator, and a fly casting and fly tying instructor. Zack can be reached at zjud@floridaocean.org.
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