Sex Ratios and Field Fertilization of Acartia tonsa in Tampa Bay

Marine primary consumers, including zooplankton, are crucial to the biological transfer of energy and nutrients within an ecosystem. Zooplankton species are abundant in waters around the world. The most common zooplankton species found in Tampa Bay is a calanoid copepod, Acartia tonsa. Sex ratios and fertilization frequencies of A. tonsa serve as a metric for the population’s health, which in turn, impacts ecosystem health. Sampling cruises were conducted in Tampa Bay monthly, which consisted of plankton tows across the surface of the water column to acquire live A. tonsa. Several hundred adult A. tonsa were identified as male or female. Females were examined for the presence of an attached spermatophore sac, indicative of successful fertilization. Sex ratios and fertilization frequencies were then calculated. Given the temporal scale of the sampling, the comparative monthly fertilization and sex ratios provide insight into the annual reproductive cycle of A. tonsa. We anticipate observing more females than males in the population and finding fertilization frequencies between 40 and 70%. The findings of this study will provide a baseline for further monitoring of population health and provide the background necessary to conduct further research on the changes in A. tonsa reproductive success.

For more information email: krhenwoo@eckerd.edu