image: A manatee swims between the spans of the Mobile Bay Bridge in lower Alabama.
A new publication from the Dauphin Island Sea Lab's Marine Mammal Research Program (DISL) examines how bridge-building and in-water construction activities may affect manatees and other large aquatic species. The article, which was recently published in The Journal of Wildlife Management, addresses the direct causes of injury and death and the longer-term, cumulative impacts on manatees and their habitats.
Some issues associated with construction activity include possible entanglement in barriers such as booms and siltation screens, loss of important habitats such as seagrass beds, and increased vessel activity near construction sites.
"Boat strikes are a major cause of manatee deaths, and increased presence of boats and barges in construction zones puts manatees at greater risk in these areas," stated lead author and manager of DISL's Manatee Sighting Network, Elizabeth Hieb. "Increased noise in construction areas can also mask the sound of approaching vessels, making it more difficult for manatees to avoid collisions," added Hieb.
DISL's new publication also reviews best practices to reduce the negative effects of construction on aquatic species. DISL researchers hope their work can be used to better understand and reduce the scope of risks associated with the construction of bridges, marinas, boat launches, and other infrastructure.
Manatees may be particularly vulnerable in areas along the northern Gulf of Mexico coast where less is known about their abundance and distribution. Data collected by DISL's Manatee Sighting Network since 2007 suggest that more manatees are seasonally migrating from Florida to Alabama and nearby waters in recent years. Construction projects planned in Mobile Bay, such as the expansion of the I-10 Bayway and deepening and widening of the Mobile Bay ship channel will benefit from the data and other information compiled in this timely review.
"This is not just an issue in Alabama or the U.S., but also globally," said Hieb. "More and more people are living in coastal areas where large species like manatees, dolphins, turtles, and fish also live, so manatees are a great model species for understanding how construction may affect many different species."