(Editor’s note: Alison Green, senior marine biologist at The Nature Conservancy, is spending the next two weeks diving and exploring Palmyra Atoll as part of the first marine assessment of the atoll. Follow her posts from Palmyra on Cool Green Science…and learn more about the expedition.)
During World War II, Palmyra was one of many atolls that became a U.S. Naval air station, undergoing extensive modifications including (a) dredging a deep channel between the ocean and lagoon, and (b) dredging and filling to expand and link the islands via causeways.
This reduced circulation in the lagoon dramatically and seriously degraded coral reef communities within the lagoon.
In the seven decades since this construction, Mother Nature has started to reclaim the atoll by eroding away the causeways and establishing new circulation patterns in the lagoon.
Jim Maragos of the U.S. Fish & Wildlife Service, a member of our expedition, has been studying the reefs of Palmyra for 30 years. “When I first visited Palmyra, I found a heavily modified lagoon system with very little life,” he told me. “Since then, several breaches have occurred in the causeways that have increased water flow between the lagoons. Unfortunately, they are also sending hot turbid lagoon water over shallow reefs outside the lagoon.”
“When the breaches occurred, these shallow reefs were healthy with literally miles of lush coral growth east and west of the lagoon.” he added. By 1998, he realized these new, unnatural flow conditions were also killing corals outside the lagoon.
“Removing part of the north-south causeway to provide more natural circulation patterns is a high priority for protecting Palmyra’s coral communities, especially its famous Coral Gardens,” said Jim.
Should we give Mother Nature a hand and help her restore more natural patterns of circulation around the reef? Or should we let her continue to find her own way, which may cause more harm to coral communities?
Detailed scientific studies have been conducted since 2000 — and more are now required to ensure that restoration would improve and not exacerbate the problem further.
Despite these challenges, Palmyra is still a fabulous place. In this expedition we have seen spectacular coral communities and excellent coral recruitment, indicating great recovery potential if more natural current patterns can be restored in the lagoon.
(Caption: Satellite image of Palmyra (Space Imaging, Inc. 2000) showing coastal construction that reduced east to west current flow through the lagoon. The large, long island in the north (Cooper Island) and those in the south and east were built by expanding and connecting islands via causeways (including the north-south causeway). A deep channel was dredged from the ocean to the lagoon in the southwest side of the atoll. The Coral Gardens are located on the eastern end of the atoll. Credit: Jim Maragos/USFWS.)