By Roxi Aslan
Originally published at ScientificAmerican.com
On our science diving trip to Palau we visited Jellyfish Lake, a tropical marine lake home to millions of golden and moon jellyfish. Due to the stratification of the lake into two layers, the bottom anoxic layer containing concentrations of hydrogen sulfide, phosphate, and ammonia, the lake is an unsafe environment for divers. Therefore, only snorkeling is permitted in Jellyfish Lake to ensure the protection of visitors. Because the sting of the jellyfish present in the lake is very mild to the point of being unnoticeable, divers are able to safely enjoy an almost dreamlike environment.
Aside from the lake’s aesthetic appeal, which has contributed to a five-fold increase in Palau’s tourism since 1986, it is an attractive site for evolutionary and ecological study (Dawson 2001). Over the span of about 20,000 years in their confined ecosystem, the dense jellyfish in the lake have developed remarkable adaptations including daily 1-km long horizontal migrations that are believed to play a part in carbon sequestration (Dybas 2009).
During the day the golden jellyfish, which have a symbiotic relationship with microscopic algae, avoid their white-sea anemone predator by swimming east until hitting a shadow that precedes the predator rich edge of the lake (Coral). As these creatures avoid shadows, they then reverse in the afternoon and head west, completing the same cycle the next day.
In the fall of 1998, the previously stable population of golden jellyfish collapsed and then finally vanished. After field measurements and observations along with laboratory-based experiments, scientists determined that the high sea surface temperature brought on by the 1997-98 El Nino had caused the disappearance. Studies of this particular marine lake ecosystem therefore have been especially important in demonstrating the relationship between climate change and the dynamics of such an ecosystem.
The temperature of the lake has cooled since, and the jellyfish polyps that were able to endure such high temperatures made it possible for the medusae population to recover. Though the population has recovered, the jellyfish and the ecosystem as a whole remain under constant threat. The government of Palau has therefore been taking initiatives to protect this fragile ecosystem. Upon exiting our boats prior to our hike up to the lake, we were instructed not to apply sunscreen as well as to wash our shoes in a bucket of water and make sure our snorkel gear was clean. These instructions are an important step in protecting the lake as non-native species have already been introduced into the lake most likely by being carried in by a visitor.
To further protect the lake, the government of Palau has also introduced a controversial fee increase on the permits required to visit Jellyfish Lake. When our group visited with the Department of Conservation and Law and Enforcement for a lecture on conservation and enforcement activities in the State of Koror, we were told that the Jellyfish Lake permit fee would be increased from $35 to $100 and this increase would become effective on June 1st — luckily, we had bought our permits already. Soon enough, the story could be found in local newspapers and on the web where debates ensued. The fee increase has just gone into effect, and time will tell whether this increase will be effective in meeting Koror State’s objectives of controlling the number of visitors and generating enough revenue to preserve its marine resources.
About the author:
Roxi Aslan is a junior biology major with a minor in environmental studies in the USC Dana and David Dornsife College of Letters, Arts, and Sciences. Roxi plans on pursuing a career in biomedical research and hopes to hone her science diving skills in Guam and Palau.
Colin, Patrick L. Marine Environments of Palau. San Diego: Indo-Pacific, 2009. Print.
Coral Reef Research Foundation. Jellyfish Lake Information Sheet. Coral Reef Research Foundation. Print.
Dawson, Mike N., Laura E. Martin, and Lolita K. Penland. Jellyfish Swarms, Tourists, and the Christ-child. Hydrobiologia 451 (2001): 131-44.
Dybas, Cheryl. “Jellyfish: Far From Passive Drifters-in-the-currents.” National Science Foundation, 8 May 2009. Web. 16 May 2012.
Editor’s note: Scientific Research Diving at USC Dornsife is offered as part of an experiential summer program offered to undergraduate students of the USC Dana and David Dornsife College of Letters, Arts and Sciences. This course takes place on location at the USC Wrigley Marine Science Center on Catalina Island and throughout Micronesia. Students investigate important environmental issues such as ecologically sustainable development, fisheries management, protected-area planning and assessment, and human health issues. During the course of the program, the student team will dive and collect data to support conservation and management strategies to protect the fragile coral reefs of Guam and Palau in Micronesia.
Instructors for the course include Jim Haw, Director of the Environmental Studies Program in USC Dornsife, Assistant Professor of Environmental Studies David Ginsburg,, SCUBA instructor and volunteer in the USC Scientific Diving Program Tom Carr and USC Dive Safety Officer Gerry Smith of the USC Wrigley Institute for Environmental Studies.