Stefano Accoroni, Cecilia Totti
Advances in Oceanography and Limnology, 2016; 7(1): 1-15
- Correct ID of Ostreopsis species in the field (distinguishing between them) is “highly problematic” requiring a comparison of precise anatomical measurements and experience comparing strains from different regions. Even genetic ID has been complicated. They are now referring to some Ostreopsis as species-complexes and clades.
- Either P- or N-depletion has been shown to lower Ostreopsis ovata toxicity. (Strain, growth phase and salinity all figure it too.)
- Turbulence affects growth rate/cell-size.
- Cell counts were consistently lower in exposed sites vs sheltered ones.
- Dino’s are easy to dislodge, which is why they show a preference for calm areas
- Turbulence is most effective against them at the peak population levels when they are mat-forming.
- While it appears there is a general preference for higher temperatures during the peak bloom (77ºF+) they tend to range widely and some strains appear to have multiple optimal ranges.
- N:P around the Redfield ratio and temperatures of at least 77ºF seems necessary to allow cell proliferation.
- Temperatures to stop a bloom were much lower, however – around or under 60ºF.
- Blooms appear to be initiated under low-N/low-P conditions and then spike with a flush of nutrients.
- It’s also suggested that Ostreopsis toxins might be intended for survival under low-N/low-P conditions while waiting for conditions to become ideal. (Which seems to be an elevation in temperature along with a spike in nutrients.)
- At least one strain of Ostreopsis showed a very strong demand for P in depletion tests, which was remarkable among dinoflagellates.
- It’s suggested that Ostreopsis may share the habit known of other dinoflagellates for resorting bacterivory/mixotrophy under low-P/low-nutrient conditions.
- Most Ostreopsis species exhibited lowered growth rates at light intensities around 250 PAR and higher….sometimes only slightly lowered, sometimes significantly.
- Higher light levels may also be related to mucus formation (for photodamage protection) and settling from their planktonic stage.
- However, being motile, they are also capable of migrating from brighter to shadier areas.
- Although recorded in the wild on a variety of substrates, there are many reports that they prefer to be epiphytic on macroalgae, which as an environment is known to have low light availability.
- Interestingly, living substrates like macroalgae support the lowest cell densities of all sampled substrates.
- All investigated seaweed types exhibited a negative effect on Ostreopsis counts: brown, red and green algae. The brown algae Dictyota dichotoma had the strongest effect….a red algae the weakest.