New research into the proportion of time semi-enclosed water bodies are connected to the ocean has found that the greater the connectivity, the greater the presence of the non-native crab species carcinus maenas.
This finding lends itself to the management of approximately 90 coastal lakes and lagoons found along the New South Wales coast, and the ongoing debate on whether to artificially open them or not.
These waterways naturally spend days to years separated from the ocean by sand bars. Artificially opening sand bars, either by dredging or by building a training wall, can alleviate flooding and improve water quality by re-establishing tidal conditions. However, a new study published in Limnology and Oceanography suggests that artificially opening lakes and lagoons may render these waterways more susceptible to biological invaders.
“Our surveys of 14 southern New South Wales coastal lakes and lagoons revealed that the invasive European shore crab was absent from waterways that were disconnected from the ocean by a sand bar for more than 60% of the time,” said lead author Clifford Garside from Macquarie University. “By contrast, the crab was recorded in all of the surveyed lakes and lagoons that had entrances either permanently trained open or naturally open for more than 40% of the time“.
Press Release, June 16, 2014