空间层次及人工基质对着生藻类建群特性的影响

为全面了解着生藻类在建群中群落变化的生态学特性,揭示着生藻类的建群规律,在以丝状藻类为优势藻的生态塘中,采用花岗岩和瓷砖为附着材料,设置水体底部和中部为附着位点,进行频次为10d的采样分析。结果表明,生态塘中共检出8门73属117种着生藻类,其中以硅藻、蓝藻、绿藻为优势类群。同时不同人工基质和不同空间层次条件下着生藻类的建群特征较一致,早期以单细胞硅藻如舟形藻(Navicula sp.)、脆杆藻(Fragilaria sp.)、曲壳藻(Achnanthes sp.)等为优势,后期以丝状藻类如鞘丝藻(Lyngbya sp.)、颤藻(Oscillatoria sp.)、伪鱼腥藻(Pseudanabaena sp.)等为优势;研究结果发现不同人工基质(花岗岩和瓷砖)对着生藻类的种类组成、细胞密度、生物量和藻类多样性无显著影响,花岗岩和瓷砖上附着的着生藻类具有较高的相似性;但不同的空间层次对着生藻类建群特征影响明显,水体底部具有更多的硅藻种类数,中部具有更多的绿藻,随着建群时间的发展,蓝藻比例不断增加;就生物量而言,底部的着生藻类叶绿素a显著高于水体中部,但两者的细胞密度无显著性差异;随着建群过程的发展,水体底部的着生藻类生物量达峰值所需的时间比中部更长。通过相关性分析,生态塘中着生藻类的生长主要受总磷的影响。

Effects of vertical location and artificial substrate on colonization of algal periphyton

The colonization of algal periphyton is a complex process in which algae colonize a new habitat and gradually develop into a mature community. Adhering substrates serve as new habitats and may play an important role in colonization of the periphyton community, but there is no consensus about the colonization process and succession patterns of algal periphyton communities on different substrates. Previous studies have mainly focused on diatoms, which tend to be the first colonizers; little is known about other types of periphytic algae. In addition, most field investigations have placed substrates at the bottom of the water column, and no attention has been paid to the colonization of algae on substrates located at different depths. This study aimed to investigate the process and ecological characteristics of algal periphyton colonization throughout the water column. Two artificial adhering substrates, granite and tile, were placed at the bottom and at mid-depth in a filamentous algae-dominated ecological pond. Algal periphyton on the artificial substrates was sampled every 10 days for analysis of species composition, cell density, and biomass, and the Shannon-Weaver index, Jaccard index, and time to peak biomass of periphytic algae were calculated. Water samples were collected from each site and water quality parameters, including total phosphorous, total nitrogen, nitrate, nitrite, ammonia, and chemical oxygen demand, were determined. The algal periphyton was dominated by diatoms, cyanobacteria, and green algae; 117 species belonging to 73 genera and 8 phyla were identified in the pond. The colonization of algal periphyton on granite and tile showed a similar pattern at both depths. At the early stage of colonization, unicellular diatoms such as Navicula, Fragilaria, and Achnanthes sp. were dominant; the dominant species changed to filamentous algae including Lyngbya, Oscillatoria, and Pseudanabaena sp. at later stage. The type of adhering substrate had no significant effect on species composition, cell density, chlorophyll a, or diversity of algal periphyton. The Jaccard index of the algal communities was similar for granite and tile. On the other hand, the effects of water depth on species composition were significant. There were more periphytic diatom species at the bottom of the water column, while more green algae were present on both substrates placed at mid-depth. The proportion of cyanobacteria gradually increased during colonization. The biomass (chlorophyll a content) of periphytic algae was higher on substrates at the bottom than at mid-depth, but the cell density did not differ significantly. Furthermore, more time was required to reach peak biomass at the bottom. Correlation analyses between cell density and water quality parameters showed that the growth of periphytic algae was mainly dependent on the total phosphorus concentration in the ecological pond.