温度和营养盐限制对网状原角藻生长与产毒的影响

Effects of temperature and nutrient limitation on growth and yessotoxin production of Protoceratium reticulatum

网状原角藻(Protoceratium reticulatum)是能够形成有毒赤潮的海洋甲藻之一,所产毒素为虾夷扇贝毒素(yessotoxins,YTXs),该藻在全球很多海域中普遍存在,其生长与产毒特征表现出较强的海域差异性。以分离自我国北黄海海域的网状原角藻为实验对象,研究了温度和营养盐(N、P)限制对该藻生长与产毒的影响。研究发现:温度和营养盐限制对藻细胞的生长和产毒均有影响,但营养盐限制影响更为显著。较低的温度更适宜P.reticulatum的生长,15℃时无营养盐限制的L1-Si培养基中藻细胞生长最好。营养盐限制尤其是P限制能够显著降低藻细胞的比生长速率和细胞密度(P<0.01),缩短藻细胞指数生长期和稳定期的持续时间。所有温度下N、P限制均有利于藻细胞内毒素累积,15℃P限制培养基中单个藻细胞中YTX毒素最高,达到92.6 pg/细胞,分别是相同培养温度下N限制和L1-Si中藻细胞毒素含量的3.8倍和7.1倍。温度变化对N和P限制下藻细胞毒素含量影响不同:在5—15℃范围内,随温度升高,N限制培养基中藻细胞YTX含量增幅逐渐下降,而P限制条件下反之。在所有培养条件下,滤液中毒素含量在稳定期后开始增多,与L1-Si相比,N、P限制不利于毒素的释放。高温能促进L1-Si培养基和N限制培养基中毒素的释放,但对P限制影响不显著。

Protoceratium reticulatum, a marine dinoflagellate that produces yessotoxins （YTXs）, is common in coastal waters worldwide and can form toxic algal blooms. There are marked differences in its growth and toxin-producing characteristics in different areas. This study investigated the effects of temperature and nutrient （N, P） limitation on the growth and toxin production of P. reticulatum recently isolated from the North Yellow Sea. The results showed that temperature and nutrient limitation affected growth and toxin production of the alga to different degrees, but nutrient limitation had a more significant influence. Lower temperatures were more suitable for the growth of P. reticulatum. Growth of algal cells in L1-Si medium without nutrient limitation was best at 15℃. P limitation greatly reduced the specific growth rate and cell density （P 〈 0.01 ）, and shortened the duration of the exponential and stationary phases. N-limited cultures, in contrast, resulted in a growth rate and maximum cell density similar to those in LL-Si medium, but with a shorter stationary phase. At all temperatures, both N and P limitation were favorable for the accumulation of YTX in algal cells, which was particularly marked in the latter. The maximum YTX content of 92.6pg/cell was observed in 1/10P medium at 15℃ at the end of the stationary phase. This was approximately 3.8 times and 7.1 times that of the YTX in the N limited and L1-Si medium at the same culture temperature, respectively. Changes in temperature had different influences on the content of intracellular YTX in N- and P-limitation cultures. In the range of 5-15℃, temperature change had a negative effect on YTX increase under N limitation, whereas in P-limited medium, the effect was positive. In all culture conditions, the YTX concentration in the filtrate began to increase during the stationary phase. Compared with L1-Si, both N- and P-limited media were not conducive to the release of toxins. Higher temperature helpful to YTX release in the L1-Si and N-limited media, but it did not significantly affect that in the P-limited medium.