PHOTOSYNTHESIS AND GROWTH OF NITZSCHIA-PUNGENS F MULTISERIES HASLE, A NEUROTOXIN PRODUCING DIATOM

The pennate diatom Nitzschia pungens f. multiseries Hasle implicated in the amnesic shellfish poisoning in bays of eastern Prince Edward Island, produces a neurotoxin, domoic acid. Batch cultures of this diatom were grown at photosynthetic photon flux densities (PPFD) of 1100 (high light, HL) and 105 (low light, LL) mu-mol m-2 s-1 at 10-degrees-C. The relationships between photosynthesis and PPFD were established on Days 1,4,8,15,25 and 34 and were quantitatively described. Maximum specific growth rates (mu-max) for the HL and LL cultures were 0.74 and 0.56 day-1 respectively. Cells grown at HL had higher assimilation number (P(m)B: 2.2-mu-g C [mu-g Chl a]-1 h-1) but lower initial slopes (alpha-B: 6.06 ng C [mu-g Chl a]-1 h-1 [mu-mol m-2 s-1]-1) than those grown at LL (P(m)B: 1.7-mu-g C [mu-g Chl a]-1 h-1; alpha-B: 8.69 ng C [mu-g Chl a]-1 h-1 [mu-mol m-2 s-1]-1). Both P(m)B and alpha-B increased from Day 1 to Day 4, and then decreased as the cells aged. Temporal variations in the rate of growth, cellular Chl a, cell concentration, carbon and nitrogen showed differences in their magnitude and lag phase.