B. Butow et al., SEASONAL AND ENVIRONMENTAL-INFLUENCES ON ANTIOXIDATIVE PROTECTION IN PERIDINIUM GATUNENSE IN LAKE KINNERET, Journal of applied phycology, 8(4-5), 1996, pp. 403-407
As the only freshwater lake in Israel, Lake Kinneret serves a number o
f important functions which directly rely upon the viability of the wa
ter. The annual outbreak of a dinoflagellate bloom strictly governs th
e nature of the macro and micro food web and ultimately determines wat
er quality. The freshwater dinoflagellate Peridinium gatunense is subj
ect to a wide range of environmental stresses through-out the spring b
loom period. It was confirmed that SOD played an important antioxidati
ve maintainance role throughout the bloom, especially during periods o
f relatively high photosynthetic activity (820 mg C m(-2) day(-1)), wh
en activity reached similar to 500 Units SOD mg protein(-1). In additi
on, high light stress (>300 mu mol photons m(-2) s(-1)) induced SOD ac
tivity, despite the low dissolved inorganic carbon (DIC) concentration
s at the end of the bloom (1.3 mM). Catalase activity was only signifi
cant at the end of the bloom, peaking at 120 mu mol O-2 mg protein(-1)
min(-1) when induced by photorespiratory activity. A series of experi
ments with Peridinium cultures showed that 2 x 10(-4) M ascorbate inhi
bited catalase activity >50% within 15 min incubation, both in vivo an
d in vitro. It is suggested that the high concentrations of ascorbate,
found previously in Peridinium during early and mid-bloom (0.2-1.6 mM
), not only eliminate H2O2 build-up, but also prevent (directly or ind
irectly) the induction of catalase.