Phytoplankton composition and biomass in tropical sodaLake Shala: seasonal changes in response toenvironmental drivers

Tadesse Ogato; Demeke Kifle

摘要

Although soda lakes are valuable, sensitive aquatic resources where phytoplankton play a decisive role for the entire ecologicalfunctions, they are among the least-studied ecosystems. Seasonal variations in phytoplankton composition, abundanceand biomass in relation to some environmental parameters of the little known, deep, large, volcanic and saline–alkaline Lake Shala were investigated over an annual cycle. The lake phytoplankton community consisted of relativelydiverse taxa (23) belonging to Bacillariophyceae, Cryptophyta, Cyanoprokaryota and Dinophyta. Bacillariophyceae andCryptophyta were the dominant groups throughout the annual cycle, accounting for about 57 and 22 of the total numberof species, and 28 and 69 of the total abundance of the phytoplankton community, respectively. Cryptomonas spp.were most abundant throughout nearly all months, contributing about 59–95 of total phytoplankton abundance, followedby Thalassiosira sp. (1–35). The chlorophyll-a concentration, as a proxy for algal biomass, was generally low(mean 17 lg L~(-1)), exhibiting only small seasonal variation. The strong, inverse relation of chlorophyll-α with water transparency(r = 0.69; n = 11) and the persistent dominance of species adapted to low-light conditions and mixing suggestthe overriding importance of these factors in controlling the lake’s phytoplankton. The results of the present study generallysuggest the phytoplankton composition and biomass in Lake Shala exhibited muted seasonal changes, despite theenvironmental perturbations, probably because of the lake’s high buffering capacity against allochthonous impactsbecause of its voluminous nature.

机译：尽管苏打湖是宝贵、敏感的水生资源，浮游植物对整个生态功能起着决定性作用，但它们是研究最少的生态系统之一。研究了浮游植物组成、丰度和生物量的季节性变化与鲜为人知的深海、大型火山和盐碱性沙拉湖的一些环境参数的关系。湖泊浮游植物群落由相对多样化的类群组成（23），属于芽孢杆菌科、隐藻门、蓝原核门和恐龙门。芽孢杆菌科（Bacillariophyceae）和隐藻门（Cryptophyta）是整个年周期的优势类群，分别占浮游植物群落总数的57%和22%，占浮游植物群落总丰度的28%和69%。隐单胞菌属在几乎所有月份都最丰富，约占浮游植物总丰度的59%-95%，其次是海藻属（1%-35%）。叶绿素-a浓度作为藻类生物量的代表，总体上较低（平均17 lg L~（-1）），仅表现出较小的季节变化。叶绿素-α与水透明度（r = 0.69;n = 11）的强反比关系以及适应弱光条件和混合的物种的持续优势表明，这些因素在控制湖泊浮游植物方面具有压倒一切的重要性。本研究的结果总体上表明，尽管存在环境扰动，但沙拉湖的浮游植物组成和生物量表现出温和的季节变化，这可能是因为该湖因其体积庞大而对异种生物的影响具有很高的缓冲能力。

Phytoplankton composition and biomass in tropical sodaLake Shala: seasonal changes in response toenvironmental drivers

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