Effects of small-scale environmental variation on metaphyton condition and community composition
Effects of small-scale environmental variation on metaphyton condition and community composition
复制标题
小尺度环境变化对后生藻状况和群落组成的影响
DOI：
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发表时间：
2012
期刊：
影响因子：
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通讯作者：
R. Verb
中科院分区：
文献类型：
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作者：
L. L. Saunders;S. Kilham;G. Fairchild;R. Verb
摘要
1. 变形藻垫子通常起源于底栖藻类生物膜，一旦到达水面，它们会经历更高的太阳辐射和温度，并减少获得营养物质的机会，但这些物理化学变化对海生生物条件和群落组成的影响几乎没有引起注意。
2. 使用位于0、2、4和6厘米深的微探针，我们在8周的时间里记录了限制在浮动网中的干湿垫内水化学的小范围差异。每周同时采集垫层顶部、中部和底部的丝状藻类及其硅藻附生植物的样品，分析其无灰干质量(AFDM)和叶绿素a、营养元素(N、P、C、Si)含量和分类组成的变化。
3. 光强、温度和溶解氧均随垫层深度的增加和整个研究期间的增加而降低。自养指数(=AFDM值/叶绿素a)在垫层顶部最大，并随着时间的推移而增加；样本的C/P和C/N比也高于垫层深处的样本。
4.在整个研究过程中， Pithophora始终是主要的藻丝(占所有藻丝随时间和深度平均的85%)；Pithophora上的附生硅藻盖度(以附生植物面积指数计算)随着时间的推移而下降，尤其是在垫子的顶部。
5.硅藻附生植物Gomhonema、Cocconeis和Fragilaria的 密度随着垫层深度的增加而增加，而Cymbella/Encyonema在表层样品中更常见。
6. 我们的结果表明，干湿垫是高度动态的群落，在空间上部分由小规模的环境变化组成，并在到达水面后受到分类组成的变化。
Summary
1. Metaphyton mats typically originate as benthic algal biofilms that experience higher solar radiation and temperatures, and reduced access to nutrients, once they reach the water surface, but the impacts of these physicochemical changes on metaphyton condition and community composition have received little attention.
2. Using microprobes positioned at 0, 2, 4 and 6 cm depth, we recorded small-scale differences in water chemistry within metaphyton mats constrained in floating nets during an 8-week period. Concurrent weekly samples of filamentous algae and their diatom epiphytes were collected from the top, middle and bottom of the mats and were analysed for changes in ash-free dry mass (AFDM) and chlorophyll-a, nutrient (N, P, C, Si) content and taxonomic composition.
3. Light intensity, temperature and dissolved oxygen declined both with increasing depth in the mat and over the study period. The autotrophic index (=AFDM/chlorophyll-a) was greatest at the top of the mats and increased over time; samples also had higher C/P and C/N ratios than samples deeper within the mat.
4. Pithophora was consistently the dominant algal filament throughout the study (representing 85% of all filaments averaged over time and depth); epiphytic diatom cover on Pithophora (calculated as epiphyte area index) declined over time, particularly at the top of the mat.
5. Densities of the diatom epiphytes Gomphonema, Cocconeis and Fragilaria increased with increasing depth within the mat, whereas Cymbella/Encyonema was more common in surface samples.
6. Our results indicate that metaphyton mats are highly dynamic communities, spatially organised in part by small-scale environmental variation and subject to changes in taxonomic composition following their arrival at the water surface.