Researchers study effects of rare climate extremes on fish communities

FIU researchers examined the severity of two climate extremes to determine its effects on coastal fish communities in the Everglades.

In South Florida, two independent but sequential climate extremes took place in 2010 and 2011 — a cold front and a drought, respectively. Climatic extremes are rare events that result in conditions that exceed the capacity of organisms to acclimate.

“It’s the first time in 60 years we’ve had two climate extremes coincide,” said Ross Boucek, researcher in the Department of Biological Sciences. “It was also, by far, the worst cold front we’ve have in 80 years. It lasted a total of 13 days – five days longer than any other cold front – which is outstanding. It’s a blessing for us to get to study these events, but it’s a curse for the species.”

Jennifer Rehage (left) and Ross Boucek (center) count, weigh and measure fishes in the Everglades.

Boucek and Jennifer Rehage, professor in the Department of Earth and Environment, developed a trait-based approach that examines functional traits, instead of relying on species-based metrics or metrics that depend on the identity of the species, to make their assessment. According to the researchers, a trait-based approach allows predictions on the severity of climate extremes to be made that are independent of the identity and location of a species.

“This type of approach can be applied to areas outside of the Everglades, allowing us to make comparisons across ecosystems throughout the world. That’s very powerful,” Rehage said. “It’s a much more powerful approach, given that we expect the frequency of climate extremes to increase because of climate change.”

By looking at traits including temperature and salinity lethal limits, the researchers found the cold front had the strongest impact on tropical species with low temperature limits, including manatees, alligators, snook, striped mullet and mangroves. The drought severely impacted freshwater fishes, including largemouth bass, Florida gar, sunfish and different wading birds.

“These findings are significant, particularly since snook and largemouth bass fisheries are so economically important to South Florida, and since small fishes are important sources of food for wading birds,” Rehage said. “It’s critical to not only track the effects of the climate extremes, but to also track the ecosystem’s recovery. This approach will allow research to better document the crash and recovery of these ecosystems and species.”

The paper, titled “Climate extremes drive changes in functional community structure,” was published in the journal Global Change Biology in April.