Periphyton structure and function in constructed headwater streams of the Appalachian coalfield

摘要

Streams are often constructed on reclaimed coal mines to offset stream losses caused by mining disturbance in the Appalachian coalfield of the Eastern USA. Periphyton is an important component of the organic matter resources in these lotic ecosystems. We compared both short-term (similar to 2 mo) and long-term (9-11 mo) dynamics of periphyton in 8 recently (most 10 y old) constructed, low-order streams in mined areas with that in 4 forested reference streams. We used artificial substrates to quantify periphyton biomass as ash-free dry mass (AFDM), viable algal standing crop as chlorophyll a (Chl a) concentration, organic matter from senescent autotrophic cells as phaeopigment (phaeo) concentration, and periphyton structure as the autotrophic index (AI) and Chl a:phaeo ratio. We compared short-term periphyton accrual rates of AFDM (r(AFDM)) and Chl a (rada) between the stream types. In constructed streams, we also evaluated relationships between environmental factors and both r(chla), and peak algal standing crop. Over the long term, mean AFDM and Chl a in constructed streams were similar to 4 and 2x higher, respectively, than in reference streams. The constructed streams also had greater mean AI values relative to reference streams, indicating lower relative abundances of viable algae in the periphyton. Short-term periphyton structural differences were similar to long-term differences, with AFDM and mean Chl a in constructed streams exceeding those of reference streams. Accrual rates were higher in constructed streams during summer and fall seasons, suggesting that higher relative light availability during leaf-on seasons in constructed streams is a primary cause of differences in periphyton production. During fall, warmer temperatures in the constructed streams also appear to have increased algal accrual. The shading of benthic habitats by planting native trees in riparian areas of constructed streams may promote autochthonous organic matter dynamics similar to that of reference streams.