The box jellyfish, Alatina moseri, is known for showing up in big numbers on Waikīkī Beach 8 to 12 days after each full moon. Researchers at the University of Hawai'i at Mānoa have published an analysis of 14 years of monthly jellyfish collection data. They have seen 173 full moons and 66,000 jellyfish since they began, "Although there have been long-term studies of jellyfish abundance and climate in recent years, none have looked at box jellyfish species," said Luciano Chiaverano a Research Scholar and head author of the paper. "This is quite surprising, as box jellyfish are among the most venomous animals in the world. Often their habitat overlaps with human recreation, resulting in painful, sometimes even lethal, stings and causing beach closures at various locations around the world."
The researchers' analysis confirm that box jellyfish arrive in Waikīkī with predictable timing based on the moon cycle more than likely to reproduce. In a 400-meter section of the beach, on average about 396 jellyfish arrived, with actual numbers ranging from 5 to 2,365. The total number of box jellyfish arriving to Waikiki shows no overall increase or decrease in the past 14 years, but follows an oscillating pattern with periods of increase and decrease, each one lasting approximately four years. The UH scientists propose, that these are probably caused by climate changes, which regulates food availability, and ultimately affecting the numbers of local jellyfish.
Chiaverano, PBRC Associate Research Professor Brenden Holland, and Waikīkī Aquarium Marine Biologist Jerry Crow analyzed three climatic indexes, 13 oceanographic variables, and seven local weather parameters. Although no significant relationship between beach counts and the weather parameters were found, jellyfish counts showed a strong, positive relationship with the primary production, abundance of small zooplankton.
It was concluded that the number of box jellyfish at Waikīkī is probably caused by an index of water mass movement, where the higher the mass, the higher the transportation of nutrient-rich waters from the northern Pacific into the oceanic waters around the Hawaiian Islands. This boost may drive regional primary production, and in turn increase zooplankton which are food for box jellyfish. "Jellyfish are known to have increased growth rates and reach larger adult sizes in response to increased food availability, and because body size positively correlates with fecundity in jellyfish, more eggs and more larvae are produced when food is readily available" said Chiaverano.
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