Preliminary experiments in establishing a standardized protocol for clearance rates of gelatinous zooplankton

COLLINI, R. C.; GRAHAM, W. M.; MIANZAN H. W.; ACHA, E. M.; SCHIARITI, A.; GENZANO, G.

Mar del Plata

Simposio; Third International Jellyfish Blooms Symposium; 2010

Gelatinous zooplankton represent a large grazing force on secondary production. However, a thorough understanding of their quantitative impact is lacking. To gain a first order approximation of their significance, interactions between various hydromedusae and their prey must be investigated worldwide. In order to do this effectively it would be beneficial to develop an easily replicated protocol. Preliminary experiments were conducted with the hydromedusae Liriope tetraphylla. Planktonic eggs of Pagrus pagrus (Pisces), red porgy, were preserved via freezing and formalin. Feeding rates of each preservation method were compared to feeding rates of live eggs. Analysis of variance (ANOVA) showed significant differences between the feeding rates of preserved eggs and live eggs, with frozen eggs being slightly more similar to live eggs than formalin. The fixing process reduces the buoyancy of the eggs, a potential source for the difference in feeding rates. Behavioral experiments to better understand the hydromedusae’s response to the presence of eggs, and in different light conditions were also conducted. Future work will focus on comparing lyophilized eggs to live eggs.