Assessing the short-term response of stream diatoms to acidity using inter-basin transplantations and chemical diffusing substrates
Assessing the short-term response of stream diatoms to acidity using inter-basin transplantations and chemical diffusing substrates
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DOI：
10.1111/j.1365-2427.2004.01242.x
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发表时间：
2004-08-01
影响因子：
2.7
通讯作者：
Ormerod, SJ
中科院分区：
文献类型：
--
作者：
Hirst, H;Chaud, F;Ormerod, SJ
1.酸碱状态对硅藻的影响很大，但有关硅藻对酸度变化的短期响应的信息很少。尽管在溪流中使用硅藻作为生物指示剂，但在暴雨(几小时到几天)或积雪融化(几天到几周)期间酸性时段是重要的。在Llyn Brianne实验流域(英国威尔士)，我们试图通过(I)在两条酸度反差的溪流之间相互移植硅藻和(Ii)使用酸扩散底物来模拟短期酸化的影响。硅藻多样性在中性区移栽到酸性溪流时迅速下降，在双向移栽中增加。在酸性溪流中，由于甜菜的快速生长，优势类群的变化在3天内发生；在近中性溪流中，优势类群的变化是由于细小鞭毛虫的繁殖而发生的。到了第12.3天，移植物与周围环境的组合几乎无法区分。围隔对群落组成没有影响，但在粗网目(26 X 50 Mm)的围隔中，硅藻对化学变化的反应比细网目(320微米)更快。化学扩散基质包括附着在配料储存层上的陶瓷砖，这些储存层在26天的时间里在近中性河流中产生了局部酸(使用H2SO4)或富金属条件(使用MnSO4)。硅藻的反应与用去离子或周围中性溪水添加的参考底物进行了比较，我们还评估了大型无脊椎动物的影响是否缓和。加酸基质的表面pH比参照砖或周围河水低1-2个pH单位。在酸处理的底物上放牧的群落与未放牧的参考群落显著不同，获得了显著更大的Euntia spp的相对丰度。然而，响应的幅度小于流间移植，这是因为(I)金属暴露和碱阳离子浓度在移栽和投药基质之间不同，或(Ii)硅藻对扩散基质上pH降低的反应受到环中性溪流中酸性硅藻稀少的限制。类似的过滤器效应、创始人效应或显性效应也可能影响硅藻对真实酸性事件的反应。这些数据表明，硅藻组合可以对酸碱状态的变化做出快速和直接的反应，但短期酸化对硅藻的影响可能比随后的恢复更快。由于所使用的实验方法不能很好地描述事件效应，硅藻对真实酸性事件的响应需要进一步的现场评估。
1. Acid-base status has major effects on diatoms, but there is little information on their short-term response to changing acidity. This is despite the use of diatoms as bioindicators in streams where acid episodes are important during rainstorms (hours to days) or snowmelt (days to weeks). In the Llyn Brianne experimental catchments (Wales, UK), we attempted to mimic the effects of short-term acidification by (i) reciprocally transplanting diatoms between two streams of contrasting acidity and (ii) using acid-diffusing substrates.2. Diatom diversity decreased rapidly on substrata transplanted from the circumneutral into the acidic stream, and increased in the reciprocal transplantation. Changes in dominant taxa occurred within three days in the acidic stream because of the rapid growth of Eunotia exigua, and by nine days in the circumneutral stream because of the proliferation of Achnanthidium minutissimum. Transplants were near indistinguishable from ambient assemblages by day 12.3. There were no effects of enclosures on assemblage composition, but diatoms responded more rapidly to altered chemistry in enclosures with coarse mesh (26 x 50 mm) than finer mesh (320 mum).4. Chemical diffusing substrates comprised terracotta tiles attached to dosing reservoirs that created locally acid (using H2SO4) or metal-rich conditions (using MnSO4) in the circumneutral stream over 26 days. Diatom responses were compared with reference substrates dosed with deionised or circumneutral stream water, and we also assessed whether effects were moderated by macroinvertebrate grazers.5. Surface pH was lower by 1-2 pH units on acid-dosed substrates than on reference tiles or in surrounding streamwater. Grazed assemblages on acid-dosed substrates differed significantly from ungrazed reference assemblages, acquiring significantly greater relative abundance of Eunotia spp. However, the magnitude of response was less than in the between-stream transplantations either because (i) metal exposure and base cation concentrations differed between the transplants and dosing substrates or (ii) diatom response to reduced pH on the diffusing substrates was restricted by the scarcity of acidobiontic diatoms in the circumneutral stream. Similar filter, founder or dominance effects might also affect diatom responses to real acid episodes.6. These data show that diatom assemblages can respond rapidly and directly to changes in acid-base status, but short-term acidification might affect diatoms more rapidly than subsequent recovery. Because the experimental methods used were imperfect representations of episodic effects, diatom response to real acid events requires further field evaluation.