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Shade effects on stream periphyton and invertebrates: An experiment in streamside channels

 

作者: JohnM. Quinn,   A. Bryce Cooper,   MoragJ. Stroud,   GregoryP. Burrell,  

 

期刊: New Zealand Journal of Marine and Freshwater Research  (Taylor Available online 1997)
卷期: Volume 31, issue 5  

页码: 665-683

 

ISSN:0028-8330

 

年代: 1997

 

DOI:10.1080/00288330.1997.9516797

 

出版商: Taylor & Francis Group

 

关键词: riparian;photosynthesis;carbon;photopigments, nitrogen;phosphorus

 

数据来源: Taylor

 

摘要:

The effects of shade on periphyton and invertebrates were investigated by comparisons in 12 replicate channels beside a pasture stream where shade cloth reduced the photosynthetically available radiation (PAR) by 0, 60, 90, and 98%. Periphytic productivity decreased with increasing shade. Periphyton chlorophyllawas consistently low (< 30 mg m−2) under 98 and 90% shade and usually low at 60% shade, whereas blooms were common during summer in the unshaded channels. More periphytic taxa occurred in the open than shaded channels and the relative concentration of the photo‐protective pigment beta‐carotene decreased with increasing shade. Nitrate uptake rates by periphyton, measured in separate chamber studies, decreased progressively as shade increased from 60% through 90% to 98%, and were more strongly correlated with gross primary productivity than periphyton chlorophyllaand particulate carbon levels. Total invertebrate and chironomid densities declined significantly as shade increased from 60 to 90% and invertebrate taxa richness declined markedly between 90 and 98% shade. Most collector‐browsing invertebrates (other than chironomids) had similar densities under 0–90% shade and only declined at 98%. This suggests a weak coupling of these invertebrates with local periphyton production and also suggests that energy derived from up‐stream sources may be their most important food in these pastoral streams.

 

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