For Work Package 1, we sampled the natural population of microplankton in Cala Santanyí from June 2021 to October 2022 to study dinoflagellate and parasitoid abundances during bloom and non-bloom conditions. From June 2021 to October 2021 and from May 2022 to mid-September 2022, we collected water and sediment samples every 5-10 days. During the three algal blooms which occurred during our sampling period, two in summer of 2021 and one in summer of 2022, we sampled every 2-3 days to better understand the dynamics between dinoflagellates and parasitoids during the bloom. From November 2021 to April 2022, we sampled every 10-30 days. We sampled twice more from mid-September 2022 until the end of October 2022. Overall, 70 days were sampled during this 16-month long period. When we sampled, we measured water temperature and salinity, and collected 6 L of water from the surface layer, 6 L of water from the bottom of the water column (< 1.5 m), and > 500 g of sediment. For both the surface and depth sampling, we used a Flow CAM VS series (Fluid Imaging Technologies, Inc.) to identify and measure the abundance of plankton and parasitoids, a Walz Phyto-PAM to measure photosynthetic activity, preserved samples for manual counts and flow cytometry, and filtered water for nutrient and chlorophyll measurements. We incubated water from the sampling to better detect parasitoid abundances. During most of the sampling period, we kept a fluorometer in the inlet to measure chlorophyll and turbidity. We placed a current meter at the end of the inlet to measure water movement during the summer months of 2021 and 2022. We are still working on processing this data, and several additional projects have come out of the work of this part of the project. We detected parasitoids in incubation samples in March, April, and May 2022, indicating that parasitoids are present before the algal blooms in summer and that parasitoid infections may persist in winter when dinoflagellate abundances are low.
In Work Package 2, we proposed studying individual parasitoid zoospores and their interactions with potential host dinoflagellates. This project is part of the thesis of a PhD student at the University of the Balearic Islands. We perfected culturing techniques of the model dinoflagellate Alexandrium minutum and the Perkinsozoa parasitoid Parvilucifera sinerae. We are in the preliminary stages of conducting and analyzing high-speed video microscopy and microfluidic experiments to analyze parasitoid zoospore movements.
In Work Package 3, we proposed to: (1) work with FACSA, an integrated water resources management company in Spain which controls water pumps currently used to dilute plankton concentrations along beaches in the Balearic Islands; (2) develop a numerical model to simulate parasitoid infections in dinoflagellates; and, (3) validate the model using mesocosm experiments. We worked with FACSA on 14 July 2021 to evaluate the flow of the pumps in Cala Santanyí and found the flow generated was not sufficient to dilute plankton. However, we were unable to complete the numerical model or evaluate it due to our continued work on Work Package 2. While other studies have quantified swimming behaviors in dinoflagellates, no study as quantified the movement behaviors of parasitoid zoospores, which is integral to our model.
Information about our research has been disseminated through several different avenues. Preliminary results were presented to the larger scientific community by the researcher at the Microscale Ocean Biophysics 6.0 in May 2022, at the 12th International Conference on Modern and Fossil Dinoflagellates in July 2022, and by the PhD student at the PHYMOT Second Annual Meeting in March 2023. As part of the EU Ocean Night in Palma on 30 September 2022, we demonstrated some of our techniques and the importance of our research to the general public. We promoted our research through a poster displayed at the Estacio Intermodal in Palma, Mallorca, in September 2021.
