营养盐水平对四种海洋浮游硅藻胞外多糖产量的影响

4种海洋浮游硅藻(牟勒氏角毛藻、海链藻、三角褐指藻和新月菱形藻)培养在改进的f／2培养基中，研究了不同氮、磷和硅营养水平对它们胞外多糖产量的影响．结果表明，硅藻胞外多糖的生产和释放具有种间特异性，角毛藻和海链藻胞外多糖的生产和释放主要在静止期，而三角褐指藻和新月菱形藻在指数生长期前期和静止期都能生产和分泌较高的胞外多糖；培养液中低浓度磷减少了4种硅藻在静止期胞外多糖的产量，但增加了角毛藻在生长期前期胞外多糖的产量；氮浓度的降低增加了三角褐指藻在指数生长前期胞外多糖的产量，但减少了其他3种藻类胞外多糖的产量；硅浓度的降低对4种硅藻胞外多糖的产量影响不大，在一定程度上还促进了静止期胞外多糖的生产．本研究表明，营养盐水平对硅藻胞外多糖生产的影响因种类和细胞所处生长期不同而存在着很大的差异．

Influences of nutrient status on extracellular carbohydrate production of marine planktonic diatoms

Four planktonic diatom species, Chaetoceros muelleri, Thalassiosira sp. , Phaeodac-tylum tricornutum and Nitzschia closterium , were cultured in modified f/2 medium, and the in-flue'nces of different levels of three nutrients, nitrate, phosphate and silicate on the production of extracellular carbohydrates were investigated. The results showed that production and release of extracellular carbohydrates were species specific, extracellular carbohydrates were produced mainly in the stationary phase of C. muelleri and Thalassiosira sp. , however, both in the early exponential phase and stationary phase in P. tricornutum and N. closterium. The decrease of phosphate concentration in the medium inhibited extracellular carbohydrate production in the stationary phase, however, lower phosphate concentration increased extracellular carbohydrate production in the early exponential phase of C. muelleri. Low concentration of nitrate increased extracellular carbohydrate production in early exponential phase of P. tricornutum and inhibited the production of other three species. The decrease of silicate concentration almost did not influence extracellular carbohydrate production in the four species and increased the production in the stationary phase to some degree. The results indicated that the influences of nutrient status on the extracellular carbohydrate production differed among the algal species and the growth phase.