In 1960, CBL Research Associate David Cargo started a daily routine of strolling down the CBL research pier and recording the number of jellyfish he could see in the water. Today, CBL Assistant Professor Dr. Hongsheng Bi and his students are continuing the same method — and are working on a new jellyfish-counting method as well.
In July 2013 and 2014, the team tested a sonar imaging system off of the pier called ARIS. The system takes pictures of organisms in the water using sound signals. This makes it possible to accurately and consistently count jellyfish throughout the water’s depth, not just at the surface.
Dr. Bi and his team also deploy a system called ZOOVIS (ZOOplankton VISualization system) in the Chesapeake Bay. ZOOVIS uses specialized optics that produces a red beam of light with rays that run in parallel. Anything that disrupts the parallel light path creates a “shadow" that is photographed by the system. This approach means that everything in the field of view is in focus.
Traditional methods for sampling jellyfish, such as Dr. Cargo’s visual observations, may not sample young jellyfish effectively and the use of nets and pumps can damage these delicate, gelatinous zooplankton. Using advanced technologies such as ZOOVIS and ARIS allow CBL scientists to conduct more complete and efficient studies in a wider variety of environments.
Dr. Bi’s team combines their advanced jellyfish counts with environmental factors measured from the CBL pier daily, including temperature, salinity, and chlorophyll levels, to analyze how environmental conditions and the jellyfish population are related.
They are also trying to determine if the jellyfish counts taken from the CBL pier accurately represent the number of jellyfish in the entire Chesapeake Bay.
An estimate of the number of jellyfish in the water allows researchers to determine whether jellyfish will create a problem, not only for unlucky swimmers they sting and fishermen whose nets they clog, but for the food web. Jellyfish feed on the same small fish and zooplankton that larger predatory fish feed on, so too many jellyfish in an area means less food for those fish.
However, it appears that the Bay’s jellyfish population is actually decreasing, but whether it is due to climate change or a decreased oyster population remains unclear.
