A COMPARISON OF PHOTORESPONSE AMONG TEN DIFFERENT KARENIA BREVIS (DINOPHYCEAE) ISOLATES¹

Abstract

Many laboratories have solely used the Wilson isolate to physiologically characterize the harmful algal bloom (HAB) dinoflagellate Karenia brevis (C. C. Davis) G. Hansen et Moestrup. However, analysis of one isolate may lead to misinterpretations when extrapolating measurements to field populations. In this study, pulse-amplitude-modulated chlorophyll fluorometer (PAM-FL) relative electron transport rate (ETR), F v ⁄ F m , and chl were compared with traditional techniques, such as 14 C photosynthesis versus irradiance (P-E) curves, DCMU [3-(3¢,4¢-dichlorophenyl)-1,1-dimethyl urea] F v ⁄ F m , and extracted chl. The DCMU and PAM-FL values of F v ⁄ F m (r 2 = 0.51) and chl (r 2 = 0.58) were in good agreement. There was no correlation between 14 C and PAM-FL a, P max , and b parameters because PAM-FL ETR was only a relative measurement. The PAM-FL techniques were then used to investigate P-E curves, quantum yield of PSII (F v ⁄ F m ), and chl from 10 K. brevis isolates to determine whether one or all isolates would better represent the species. Comparisons were made with a radial photosynthetron, which allowed for controlled conditions of light and temperature. Isolate a, P max , and b varied between 0.097 and 0.204 lmol e ) AE m )2 AE s )1 AE (lmolquanta AE m )2 AE s )1 ) )1 , 80.41 and 241 lmol e ) AE m )2 AE s )1 , and 0.005 and 0.160 lmol e ) AE m )2 AE s )1 AE (lmol quanta AE m )2 AE s )1 ) )1 , respectively. Either carbon limitation and ⁄ or bacterial negative feedback were implicated as the cause of the P-E parameter variability. Furthermore, these results directly contradicted some literature suggestions that K. brevis is a low-lightadapted dinoflagellate. Results showed that K. brevis was more than capable of utilizing and surviving in light conditions that may be present on cloudless days off Florida.

A brief summary of the physiology and ecology of Karenia brevis Davis (G. Hansen and Moestrup comb. nov.) red tides on the West Florida Shelf and of hypotheses posed for their initiation, growth, maintenance, and termination

“…More recently, however, Schaeffer et al (2007) found variability in the photosynthesis-irradiance response between clones with a wide range of values for the initial slope of the photosynthesis vs. irradiance (P vs. E) curve and the maximum rate of photosynthesis per unit irradiance. They suggest that some clones of K. brevis are not strictly low light adapted and can easily grow at typical surface irradiances.…”

Temporal variation of caspase 3-like protein activity in cultures of the harmful dinoflagellates Karenia brevis and Karenia mikimotoi

“…While these data are insufficient to claim the occurrence of a specific type of cell death they certainly provide evidence of the cells' deteriorating condition . 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 (Schaeffer et al, 2007;. However, the maintenance of high F v /F m values even during the decline phase of the cultures is unexpected and surprising since F v /F m is commonly used as an indicator of the physiological state of cells, which responds mostly to nutrient limitation and high irradiance (Kolber and Falkowski, 1993).…”

Diel vertical migration thresholds of Karenia brevis (Dinophyceae)

“…Results presented here lead to the conclusion that cells follow an optimization scheme based on threshold limits to control vertical migration in the water column. Competition for space and time at the surface may have induced cells to expose themselves to photo-inhibiting light (Schaeffer et al, 2007). However, the average time spent at a photo-inhibiting light location may be insignificant when compared to the reward of obtaining an optimal position for carbon fixation later.…”