Primary Studies On Anti-algal Effect Of Cornstalk On HABs Algae And Its Mechanism

Objective: In recent years, HABs have occurred frequently in China and all over the world, which has a great impact on marine ecosystem, aquaculture, economics development and human health. HABs have caused widespread attention, especially, its management and control. It is deemed to be a promising method applying alllelopathy to control HABs, since it is economical, effective and friendly to environment. In this paper, effects of com stem and leaves on the growth of A.tamarense were assessed, the selectivity in inhibition on five HABs algae, Alexandrium tamarense, Chattonella marine, Heterosigma akashiwo Hada ex Y. Hara et Chihara,P. donghaiense Lu, Phaeocystis globosa, was discussed, anti-algal chemicals in com leaves were analyzed by GC-MS. The main objective of this study was to provide more information on new algaecide with efficiency, ecological safety and selectivityMethods: The inhibitory effects of cornstalk on A.tamarense were assessed by counting microalgal cells under a CKX 41 inverted microscope. The effect of the com stalk on the morphology of microalgae were observed under microscope. Fractions of secondary metabolites which inhibited the growth of A.tamarense were isolated by several separation techniques from the ethanol extract of the com leaves. The anti-algal chemicals were analyzed by GC-MS.Results: Cornstalk was shown to have inhibitory effect on A.tamarense, and the inhibition of com leaves was stronger than that of the com stem. 0.5g/L of the com leaves inhibited A.tamarense remarkably in cell density of 1.69×10~6cells/L, whereas 1.0g/L com leaves removed the algae efficiently. There are a large amount of linoleic acid, linolenic acid, and palmitic acid in anti-algal extracts from com leaves. Besides fatty acids, esters such as ethyl cetylate and dibutyl phthalate existed in relatively high content in the allelochemicals too. The results suggested that fatty acids play an important role in the anti-algae and that cornstalk have selective inhibitory effect on different HABs algae.