| 摘要: |
| 分离于香港海域的塔玛亚历山大藻单克隆藻株的昼夜垂直迁移特性的实验研究于1994年9月-1995年4月在暨南大学水生生物研究所的人工培养柱里进行。结果表明，该藻具有显著的趋光性和节律性昼夜垂直迁移行为。其昼夜垂直迁移的一般规律为光照开始后立即向上迁移，向下迁移则从光照结束前2h左右开始，直至光照结束后1h左右才在底部形成细胞的最大分布，但在连续光照或无光照的第2或第3天以后，这种规律性的昼夜垂直迁移即完全消失。因此，该藻垂直迁移的调控机制表现为显著的趋光性，但生物学节律可能也起着一定的作用。塔玛亚历山大藻垂直迁移速度与水柱温度密切相关，水柱温度越接近其最近生长温度或垂直温度梯度越小时，其垂直迁移速度越快，在12.5°C以下，则完全丧失垂直迁移的能力。塔玛亚历山大藻的上迁速度一般比下迁速度快，在最适温度范围甲，其向上迁移速度最高可达120 m/h;而下迁速度最高只有0.70 m/h。缺氮条件下塔玛亚历山大藻的迁移速度明显减慢，光照期避开表面而聚集于亚表层，并有明显的提前下移的倾向。 |
| 关键词: 赤潮 甲藻 塔玛亚历山大藻 昼夜垂直迁移 |
| DOI： |
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| 基金项目:国家自然科学基金资助项目，9389008号 |
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| LABORATORY STUDY ON THE DIURNAL VERTICAL IVIIGRATION OF A POISONOUS RED-TIDE DINOFLAGELLATE ALEXANDRIUM TAMARENSE |
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QiYuzao, Huang Changjiang, Zhong Yan, Zheng Lei
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Institute of Hydrobiology, Jinan University, Guangzhou 510632
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| Abstract: |
| The diurnal vertical migration (DVM) of a poisonous red tide dinoflagellate Alexandrium tamarense isolated from Hong Kong waters was studied from Sept, 1994 to April, 1995 in laboratory culture tubes (glass: 4 × 100 cm and 4 × 195 cm; plastic: 10.6 × 200 cm). In any experiment, A. tamarense was always kept at density of about 1000 cell/ml, and pre-cultured in the experimental culture tube for at least 48h. The present study involved four experiments. The first was a phototaxis experiment, wherein the vertical distributions of A. tamarense were investigated under different light conditions by varying the distance of the light source to the water surface. The second experiment addressed the A. tamarense vertical distribution during continuous 48h of darkness and of light. The third experiment was done in temperature of 12.2 - 14.9, 13.7 - 21.4, 18.0 - 25.6, 18.1 - 27.8 and 18.1 - 29.5°C. The last experiment was done under conditions of nitrate enrichment (148.8 μmol/L) or deficiency (5.6 μmol/L).
The results showed that A. tamarense exhibited strong phototaxis and clear diurnal vertical migration. The general pattern of DVM was that the cells started to migrate up just after light on and finished downward migration from ca. 2h before light off to ca. 1h after light off. The diurnal vertical migration, however, completely ceased from the second or third day under continuous dark or light conditions. There was significant relationship between water temperature and the DVM speed of A. tamarense. The diurnal vertical migration was remarkably accelerated when the water temperature was near its optimum growth temperature range (20.0 - 24.0°C) or when the temperature gradient throughout the water column was small, and ceased when the temperature was below 12.5°C. The upward DVM speed of A. tamarense was generally faster than the downward speed. In its optimum growth temperature range, the highest upward speed was 1.20 m/h, but the highest downward speed was only 0.70 m/h. With insufficient nitrogen supply (5.6 μmol/L), A. tamarense greatly decreased its DVM speed, swarmed in the subsurface during light-time and tended to migrate downwards earlier than usual.
These findings suggest that the DVM behavior of this alga is strongly controlled by phototaxis, but that the biological clock rhythm might have certain effects on it. When the water temperature drops within its optimum growth temperature range, the DVM speed of A. tamarense is the fastest. However, the physiological state of A. tamarenseA. tamarense may affect its behavior and DVM speed. |
| Key words: Red-tide, Dinoflagellate, Alexandrium tamarense, Diurnal vertical migration |
