Subscribe
Sea NettlesSea nettles (Chrysaora quinquecirrha) are stinging jellyfish that normally proliferate in the saltier regions of Chesapeake Bay from late spring to fall. Their abundance seasonally is largely controlled by water temperature and salinity.
Indicator Details
Sea Nettles
Sea nettles unusually sparse in the Choptank River in 2011
Sea nettles (Chrysaora quinquecirrha) are stinging jellyfish that normally proliferate in the saltier regions of the Chesapeake Bay from late spring to fall. In the Choptank River in 2011, sea nettles were virtually nonexistent—appearing for a shorter period of time and in much lower abundance than in previous years. 2011 was the first time on record that counts never reached 100 (see graph below). Their extremely late appearance and very low numbers are most likely due to the unusually low water salinities experienced in the late spring and early summer. The low salinities likely inhibited strobliation (i.e., reproduction), but since sea nettle polyps overwinter for several years, the low numbers this year are not necessarily indicative of what to expect in 2012.
Method for counting sea nettles
Common visual counting methods require an observer to make sea nettle counts in person. These extremely simple and cost-effective methods allow for a large amount of data to be collected, as compared to more traditional counting methods (e.g., towing plankton nets from a boat). However, more observations are needed in order to better understand what causes high abundances of sea nettles in patches. Digital video surveillance cameras may provide an answer by enabling the automation of the visual counting process. As a result, scientists could make simultaneous observations at multiple locations or continuous observations for longer periods of time. Beginning in 2010, a video camera was deployed at the Horn Point Laboratory dock on the Choptank River in order to determine the effectiveness of cameras for this purpose. Unfortunately, sea nettles were rarely within the view of the camera due to 2010's low abundance. Yet, scientists were still able to make some conclusions by using plastics disks suspended from a float at the surface to simulate sea nettles. In 2011, this digital surveillance method was again difficult to utilize due to the low numbers of jellyfish present in the water. However, this method will continue to be used, and will be further refined in the future.
Acknowledgements:
Webpage courtesy of Maggie Sexton (UMCES-HPL)
For more information, see Mapping sea nettles in the Chesapeake Bay.