Establishment of Gambierdiscus cultures
Epiphytic dinoflagellate communities are sampled monthly by collecting macroalgae genera known to host Gambierdiscus populations, such as Halimeda and Dictyota. Samples are shaken and sieved in order to obtain the dinoflagellate community from each sample and Gambierdiscus cells are isolated by single cell isolation and cultures are maintained for studies on genetic diversity, growth, and toxin production.
Gambierdiscus population dynamics
Both macroalgal and neutral substrates are used to investigate population dynamics. During monthly samplings, a large sample of multiple macroalgal species representing the dominant species at that time is collected. Samples are processed as mentioned above and used to quantify Gambierdiscus populations and analyze toxicity of wild Gambierdiscus populations. In addition, cages are deployed at each of the sites, containing artificial substrates. These substrates are sampled monthly, shaken and sieved in the same way as the macroalgal samples, and analyzed for dinoflagellate community composition.
At Tier 1 sites, temperature and light measurements are recorded every 15 minutes using HOBO data loggers. During monthly collections, light, temperature, salinity, and dissolved oxygen are recorded. Near-bottom water samples are collected and analyzed for nitrate + nitrite, phosphate, silicate, and ammonium.
Benthic community assessment
Benthic cover is assessed monthly by taking photos along transect lines; the photos are analyzed by Coral Point Count, which facilitates identification and categorization of benthic cover by placing random points on the photos. Community compositions as well as changes in coral cover and macroalgal cover are determined.
Collecting fish for toxin determination
Herbivorous and carnivorous fishes are captured by hook-and-line, spearing, and trapping at both Tier 1 and Tier 2 sites. Samples are extracted for ciguatoxins and shipped to the FDA Gulf Coast Seafood Lab for toxin analysis, including quantification and identification of CTX congeners.