Ecologists are reporting that rising temperatures in the Atlantic Ocean may be allowing certain tropical fish to spread to shallow waters that are becoming warmer, an expansion that could pose a significant threat to coral reefs.

A study of 40 species along the reefs off the North Carolina coast shows northward movement by the invasive and poisonous lionfish, according to researchers from the National Oceanic and Atmospheric Administration (NOAA) and the University of North Carolina-Wilmington, who published their findings in the September issue of Marine Ecology Progress Series.

“Globally, fish communities are becoming more tropical as a result of warming temperatures, as fish move to follow their optimal temperature range,” study author Paula Whitfield, a research ecologist at NOAA’s National Centers for Coastal Ocean Science, said in a news release. “Along the North Carolina coast, warming water temperatures may allow the expansion of tropical fish species, such as lionfish, into areas that were previously uninhabitable due to cold winter temperatures.”

The Indo-Pacific lionfish was first sighted off the east Florida coast in the late 1980s. They have since spread throughout the western North Atlantic, including the Gulf of Mexico and Caribbean, according to the news release.

In 2000, the lionfish was also reported off the coast of North Carolina. Historically, both temperate and tropical species live in the North Carolina reefs, confined to their range limits by water temperatures. But, the researchers noted, temperatures in this zone are becoming more tropical.

Lionfish are viewed as a major threat to Atlantic reefs by reducing reef fish recruitment and biomass, the researchers said, and they may be involved with cascading impacts such as decreased coral cover on coral reefs.

For their findings, the researchers combined year-round bottom water temperature data with fish community surveys in water depths from 15 to 150 feet off the coast of North Carolina from 2006 to 2010.

“The temperature thresholds collected in this study will allow us to detect and to estimate fish community changes related to water temperature,” explained Whitfield.

“This kind of monitoring data set is quite rare because it combines multiyear quantitative fish density data with continuous bottom water temperature data from the same location,” added the study’s co-author, Jonathan A. Hare, NOAA Fisheries research oceanographer, in the release.

The researchers found the fish community in deeper water, from 122 feet to 150 feet with a winter mean temperature of 69.8 degrees Fahrenheit, was primarily tropical. They concluded that water temperature was a key factor in controlling their expansion.

And they noted lionfish have become the most abundant species in those areas. Although the lionfish were restricted to depths below 87 feet where the average water temperature was higher than 59.5 degrees, the fish could spread to shallow waters that are becoming warmer.

“The results will allow us to better understand how the fish communities might shift under different climate change scenarios and provide the type of environmental data to inform future decisions relating to the management and siting of protected areas,” said Whitfield.

Source: consumer.healthday.com