SANIBEL-CAPTIVA CONSERVATION FOUNDATION The Sanibel Lighthouse Beach on May 20.

The Sanibel-Captiva Conservation Foundation reported that as the humidity builds and daily temperatures start to rise, it is clear that summer is quickly approaching in Southwest Florida. While these environmental changes are expected annually, a new seasonal trend may be on the rise — warming temperatures in the Caloosahatchee and the Gulf of Mexico.

SCCF’s River, Estuary, and Coastal Observing Network (RECON) monitoring stations have measured heightened surface water temperatures at several sites this year, with a maximum reading so far of 90.1 F at the Fort Myers site along the Caloosahatchee River.

“While water temperatures this high are not unprecedented in our region, peaks are usually seen later in the summer months. The concern is that these measurements represent part of the larger trend of unseasonably hot water temperatures in the Gulf and Atlantic, which has worsened in recent years,” Policy Associate Allie Pecenka said on May 28. “This trend peaked last summer with record-setting water temperatures felt across the state, reaching as high as 101.1 degrees F in the Florida Keys.”

The SCCF reported that water getting so warm too early in the season could have widespread impacts on the local ecosystems, contributing to harmful algal blooms, impacting the movement patterns and foraging behaviors of wildlife, and intensifying storms in the Gulf and Atlantic. Warmer waters are more conducive to the development of hurricanes and the process of rapid intensification — when a storms’ maximum wind speeds increase by more than 35 mph over a 24-hour period.

“While these local temperature trends are very concerning, we have yet to collect adequate data for the 2024 season to predict with certainty how this summer will compare to that of 2023,” she said.

SANIBEL-CAPTIVA CONSERVATION FOUNDATION Data from the Sanibel-Captiva Conservation Foundation’s River, Estuary, and Coastal Observing Network (RECON) site at Fort Myers Beach. The 2024 temperatures between May 10-28 are shown in yellow, with the most recent reading being 88.43 degrees F. Data from 2023 is missing due to losing the RECON station during Hurricane Ian.

Temperature can also change the solubility of gases and water soluble compounds. For example, warmer water has lower concentrations of dissolved oxygen. If atmospheric greenhouse gas concentrations continue to increase, temperature increases of 1 to 2°C combined with wider swings in temperature are expected to cause shifts in species distributions.

The SCCF reported that it will continue to collect data from its RECON system to determine how the water temperature spikes may correlate to larger-scale and global trends of warming.