Effects of Hurricanes on Aquatic Vegetation and Fisheries in Florida Lakes
Hurricanes are a large-scale disturbance that can cause catastrophic damage to infrastructure and the environment. The impacts of hurricanes on aquatic vegetation can be severe and may result in long-lasting impacts, often leading to many years of recovery to return to pre-hurricane conditions. If you drove through the panhandle of Florida after Hurricane Michael, you likely noticed the widespread damage and significant loss of trees and other vegetation. Imagine this amount of wind energy across a shallow lake: wind-driven wave action coupled with high water levels physically uproots plants and resuspends sediments from the bottom into the water column. This greatly increases turbidity, decreasing the clarity of the water, which reduces sunlight penetration and suppresses plant growth. The recovery to aquatic vegetation communities can take many years, and sometimes may never recover to pre-hurricane levels. This devastating sequence has played out many times in Florida’s lakes and has been documented in numerous peer-reviewed scientific publications. While hurricanes are not the only stressor on freshwater systems, in this article, we summarize some of the impacts of hurricanes to Florida lakes.
Florida Hurricane Seasons of 2004 – 05
The hurricane seasons of 2004 – 05 were particularly devastating for Florida. Hurricanes Charley, Frances, and Jeanne all made landfall in Florida as major hurricanes in 2004, and Hurricane Wilma swept across Lake Okeechobee as a major hurricane in 2005.
Lake Weohyakapka (Walk-In-Water) and Farm 13-Stick Marsh were ravaged by the 2004 storms as wind-driven wave action uprooted much of the submersed aquatic vegetation primarily consisting of Hydrilla. Both waterbodies maintained high-quality Largemouth Bass fisheries prior to the hurricanes. However, the loss of habitat and degraded water quality resulted in reductions in the number of juvenile Largemouth Bass for many years following these hurricanes. This led to drastic reductions in angler effort to catch largemouth bass, catches of trophy-sized fish, and expenditures at the tackle shops supporting these fisheries. The picture below shows uprooted hydrilla and other aquatic vegetation along the shoreline of Lake Walk-In-Water post-hurricanes. In both instances and many others, the lakes no longer have hydrilla even though no hydrilla treatments were conducted by the Invasive Plant Management program.
The most notable hurricane impacts to aquatic vegetation communities have been documented in Lake Okeechobee. As Hurricanes Frances and Jeanne crossed the lake, winds pushed water from the north of the lake to the south of the lake. It was like tipping a bowl of water to one side. When the winds receded, the water rushed back to the north. Water levels at the north end of the lake during Hurricane Jeanne changed 16 feet in elevation in less than a day (10 feet for Hurricane Frances). These events, along with the other hurricanes Lake Okeechobee experienced in 2004 and 2005, resulted in a drastic loss of aquatic vegetation (>75% lake-wide) and a significant reduction in the abundance of sport fish as well as declines in overall species diversity. When the lake was sampled following the storms, juvenile largemouth bass were completely absent. Anglers will also remember the lake’s water looking like chocolate milk for the next couple of years due to the suspended sediments.
Hurricane Irma in 2017
Long-term vegetation and water quality monitoring programs also documented impacts at Lake Okeechobee and Lake George following Hurricane Irma in September 2017. Physical uprooting of aquatic vegetation during the hurricane left the shoreline of Okeechobee littered with uprooted plants and destroyed about 11,000 acres of submersed aquatic vegetation. Post-hurricane drainage from the Kissimmee River caused the lake to rise rapidly, drowning the nearshore vegetation with high water. Increased turbidity combined with high water levels continued to cause severe impacts to the submersed aquatic vegetation community at Lake Okeechobee, leading to the lowest aquatic vegetation coverage since the last hurricane impacts in 2004 and 2005.
Hurricane Irma and the 2004 and 2005 hurricanes caused record high turbidity levels, diminished submersed aquatic vegetation coverage, and in turn reduced fish spawning and foraging habitat that led to declines in sport fish populations. These hurricanes also caused an increase in sediment depth that could be resuspended, leading to higher turbidity during moderate storm events post-hurricanes. In 2010 there was a peak of more than 50,000 acres of submersed aquatic vegetation but successive years of high-water levels and increased turbidity on Lake Okeechobee due to hurricanes have resulted in the loss of nearly 45,000 acres of submerged aquatic vegetation.
A similar story played out at Lake George, with uprooting during Hurricane Irma and increased turbidity which caused large reductions in the coverage of important eelgrass beds. In the years following, eelgrass has struggled to recover to pre-hurricane Irma conditions as other large rain events increased turbidity and slowed the recovery of these plants. Summertime vegetation mapping conducted by the FWC has documented this change, with the 2017 mapping occurring in August just before Hurricane Irma.
All these published and reported findings demonstrate an important link between hurricanes and changes to whole lake ecosystems including drastic changes in aquatic vegetation coverage, increases in water levels and turbidity, and declining fisheries. FWC fish and habitat monitoring programs are being used to evaluate changes from these hurricanes and inform resource managers on the best strategies for habitat restoration and enhancement.