底栖微藻垂直迁移特性对群落光合效率的影响

Microphytobenthos (MPB) are important primary producers, may contribute up 50% of total primary pruction of estuarine ecosystem, and produce about 500 million ton carbon per year in neritic ecosystem. The vertical migration is a striking feature of intertidal MPB, frequently exhibiting a periodic rhythm coupled to diurnal emersion whereby cells migrate onto the sediment surface during low tide and migrate int io the sediment precding the incoming tide and at night. In intertidal flats, the large amounts of MPB biomass that accumulates in the photic layers of the sediment and the capacity for high photosynthetic activity under a wide range of environmental conditions enable MPB reach a high community-level primary productivity rate. Untill now, researches carried on MPB primary production are all on community-level rather on species-level, therefore, there still remained many details in variation mechanism of MPB photosynthesis. In this study, we aim to: 1. monitor the migration of dominated species in intertidal flats, the variation of individual and community photosynthetic efficiency along with the light and tidal cycle; 2. monoculture the isolated MPB dominated species, figure out their vertical migratory rhythm and charateristics of photosynthetic activity; 3. Using mimic-miniaturized sediment system with artificial biofilm, investigate the response of different species combination to light intensity, the effects of species variation on the community photosynthetic efficiency. Based on the charateristics of individual speices in migration and photo-physiology, we will elucidate MPB how to respond the change of environmental factors, adjust by themselves through migration, acquire the premium light conditions, and finaly attain high photosynthetic effciency for whole community. These results will help explain the adaptation of MPB to environments from on behaivor and photophysiology, also could supply new methods and species resources for high density microalgal culture.

底栖微藻是近海生态系统重要的初级生产者，垂直迁移是其适应底质环境的显著特性，其光合作用也因此具有强环境适应性和高光合能力。迄今为止，对底栖微藻光合效率的研究仅停留于群落整体水平，未能深入到种，因而尚不能明晰其内在变动机制。本研究拟通过：1.监测野外自然群落，随光和潮周期，主要组成种在微米空间尺度上的垂直迁移和光合效率变动、群落光合效率变动；2.分离纯培养主要组成种，确定其垂直迁移和光合生理特性；3.构建人工生物膜，应用室内模拟底质系统，验证不同微藻组合对光强变化的垂直迁移响应，种变动对群落光合效率变动的影响。综合分析底栖微藻如何响应环境变化，自我调节，获得最适宜光合条件，达到群落高光效的变动机制。本研究将完善一套实时微观监测底栖微藻的技术，从种的水平，明确垂直迁移对群落光合效率的影响，阐明群落适应环境、实现高效光合的内在机制，并可为微藻高密度、高光效的培养，提供新的研究思路和种质资源。

本课题通过野外调查和室内试验相结合,掌握了潮间带底栖微藻微观上的垂直分布,及其随光和自然潮周期的变动的规律；代表种的垂直迁移特性和光合生理特性；群落光合效率随光强的变动；底栖微藻垂直迁移及光合特性对不同光强的响应机制，特别清晰了底栖微藻行为及光合生理特性的光保护机制；构建并完善了室内简便模拟实验及监测系统，极大便利了实验研究底栖微藻的垂直迁移和光合生理特性。通过综合分析，清晰了底栖微藻响应主要环境因素，主动调节，达到群落高效光合的机制。除此并开展了分子鉴定工作，应用分子DNA条形码以及宏基因技术，加强并简便藻类的鉴定和群落结构分析研究，使后续研究可以摆脱繁重的传统镜检计数工作。并为微藻高密度、高光效培养提供了有力的数据依据和新的种质资源。