Effects of salinity on diel vertical migration behavior in two red-tide algae, Chattonella antiqua and Karenia mikimotoi

Abstract

Abstract:We examined the effects of salinity on diel vertical migration (DVM) of two coastal flagellates, Chattonella antiqua and Karenia mikimotoi, in 90-cm-high columnar aquariums. Experiments were performed with surface salinities from 5 to 32 and bottom salinity constant at 32. Cells of each flagellate were injected into the bottom of the aquarium at night and the vertical distribution of cells was monitored every 4 h for 36 h in one series of experiments, or twice daily (day and night) for 5 days in another. Ascent and descent started at approximately the same time in all water columns, indicating that difference in surface salinity does not substantially affect DVM rhythm in the two flagellates. During daytime, C. antiqua and K. mikimotoi transited haloclines with surface salinities ≥ 15 and accumulated at the surface, although K. mikimotoi required 2 days to transit the halocline with surface salinity of 20 and 4 days for surface salinity of 15. However, neither flagellate could transit haloclines with surface salinities of 5 or 10; instead they accumulated in the halocline during daytime. At night, most cells of both species accumulated at the bottom in all water columns, although the distribution of K. mikimotoi gradually expanded to the upper layers on successive days when surface salinity was 5 or 10. We demonstrated that low salinity in the surface layer blocks upward migration in two flagellate species and delays surface accumulation and weakens population synchrony of DVM at night in K. mikimotoi.

Diurnal vertical migration rhythms and their photoresponse in four phytoflagellates causing harmful algal blooms

“…The present study demonstrated that four noxious flagellates have distinct DVM cycles under constant environmental conditions by a small scale observation (water depth: three centimeters) with CCD camera. Although the observation scale is very small in comparison with natural environment, the obtained DVM parameters such as start times of upward and downward migrations were almost the same with one in 85‐cm cylinder aquarium in the case of C. antiqua and K. mikimotoi (Shikata et al ; the same culture strains were used), and were roughly similar to ones derived from field investigations (Table ). However, the phases of the DVM cycle of K. mikimotoi observed in some previous field studies (Honjo et al ; Koizumi et al ) occur much earlier in the L : D cycle compared with the corresponding phases in the laboratory.…”

“…It has been suggested that various environmental conditions such as temperature (Heaney and Eppley 1980), salinity (Bearon et al 2006;Jephson and Carlsson 2009;Shikata et al 2014), light (Kingston 1999;Richter et al 2002) and nutrient concentrations (Heaney and Eppley 1980) affect DVM behavior in each phytoflagellate species. However, the external environment may be of secondary importance in regulating the DVM cycle; it has been suggested that the DVM cycle is controlled primarily by an endogenous clock (e.g., Roenneberg et al 1989;Eggersdorfer and H€ ader 1991;Kamykowski et al 1999).…”

A New Fluorometer to Detect Harmful Algal Bloom Species and its Application as a Long–Term HABs Monitoring Tool

“…HAI sensors were moored at the middle and near-bottom of the water column considering the K. mikimotoi diel vertical migration, which is described in the literature (Koizumi et al, 1996, Shikata et al, 2014. Although there were no large K. mikimotoi red tide events during the observed period, the FSI measured from the HAI sensor moored at mid-water exceed 2 on August 9 th 2019.…”

Identification and expression analysis of blue light receptor aureochrome in the harmful alga Heterosigma akashiwo (raphidophyceae)

“…DVM behavior in most flagellate algae, moving nearer to the surface during the day and sinking to lower depths at night, is presumably controlled by an endogenous clock (Roenneberg et al, 1989), and affected by light, salinity, temperature, nutrient concentration (Heaney and Eppley, 1981;Kamykowski et al, 1999;Schaeffer et al, 2009;Shikata et al, 2014). This DVM behavior enables the flagellates to access nutrients enriched in deeper layers and to acquire light in the surface, and to avoid grazing by zooplankton that typically have an opposite DVM behavior (Lampert, 1989;Watanabe et al, 1988).…”