Abstract Temporary depression wetlands are often overlooked from a conservation and research perspective, despite recent evidence suggesting that their cumulative contribution to biodiversity at the landscape level is substantial. Here, we present observations aimed at understanding the significance of macrophyte cover in relation to the lower trophic levels, more particularly microalgae, within these highly dynamic wetlands. Thirteen such wetlands were sampled during October 2015, December 2015 and March 2016 in the Eastern Cape Karoo region of South Africa, to test the hypotheses that densely vegetated wetlands will have lower microalgal biomass and smaller algal size classes than sparsely vegetated wetlands. PERMANOVA results indicated that neither planktonic nor benthic microalgal biomass differed significantly between macrophyte cover categories (sparse, moderate and extensive cover), although there was a strong difference between the planktonic and benthic biotopes themselves. Planktonic and benthic microalgal assemblages were dominated by cryptophytes and chrysophytes (flagellates) throughout the study, with smaller nanoplankton being more abundant in wetlands with moderate or extensive macrophyte cover and larger microplankton dominating sparsely vegetated sites. Median benthic diatom species richness and diversity were higher under sparse macrophyte cover, but these differences were not significant, and no convincing evidence was found for an effect of macrophyte cover on microalgal biomass and assemblage composition in these temporary wetlands. Using distance-based Redundancy Analysis, dissolved inorganic nitrogen appeared to be the only environmental predictor for which a significant relationship with microalgal assemblage composition was reported. This study adds to the evidence from other assemblages (e.g. invertebrates) suggesting that the generalist nature of species occupying these systems allows them to adapt to the ever-changing conditions typical of ephemeral environments.

中文翻译：

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水生植被覆盖（Schoenoplectus decipiens）对半干旱地区临时湿地微藻生物量和组合结构的影响（南非卡鲁角东部）

摘要 从保护和研究的角度来看，临时洼地湿地经常被忽视，尽管最近的证据表明它们在景观层面对生物多样性的累积贡献是巨大的。在这里，我们提出了观察结果，旨在了解大型植物覆盖与这些高度动态湿地中的低营养水平，尤其是微藻的重要性。2015 年 10 月、2015 年 12 月和 2016 年 3 月，在南非东开普卡鲁地区对 13 个这样的湿地进行了采样，以检验植被茂密的湿地与植被稀疏的湿地相比，微藻生物量和藻类大小级别较低的假设。PERMANOVA 结果表明，浮游生物和底栖微藻生物量在大型植物覆盖类别（稀疏、中等和广泛覆盖）之间没有显着差异，尽管浮游和底栖生物群落本身之间存在很大差异。在整个研究过程中，浮游和底栖微藻组合以隐生植物和金藻（鞭毛藻）为主，较小的纳米浮游生物在具有中等或广泛大型植物覆盖的湿地中更为丰富，而较大的浮游生物则占据植被稀疏的地点。在大型植物稀疏覆盖下，底栖硅藻物种丰富度和多样性的中位数较高，但这些差异不显着，并且没有发现大型植物覆盖对这些临时湿地中微藻生物量和组合组成的影响的令人信服的证据。使用基于距离的冗余分析，溶解的无机氮似乎是唯一报告与微藻组合组成有显着关系的环境预测因子。这项研究增加了来自其他组合（例如无脊椎动物）的证据，表明占据这些系统的物种的通才性质使它们能够适应瞬息万变的环境中典型的不断变化的条件。