The hyporheic assemblage of a recently formed stream following deglaciation in Glacier Bay, Alaska, USA

Many studies focus on the recovery of stream communities following disturbances such as high flows (secondary succession); relatively few examine community composition in streams undergoing primary succession and even fewer detail the hyporheic community in such streams. We examined the composition and temporal distribution of invertebrates in the shallow hyporheic sediments of Stonefly Creek, a recently deglaciated stream in Glacier Bay, Alaska, USA, whose lower reaches became ice free in the late 1970s. We used modified polyvinyl chloride wells at four contrasting sites over two years in this stream and collected data on stream temperature, discharge, and suspended solids. A diverse assemblage of 19 taxa was found, including cyclopoid and harpacticoid Copepoda, Ostracoda, Cladocera, tardigrades, and macroin vertebrates, but the nature and extent of the goods and services provided by the hyporheos of this young stream to the whole river ecosystem are unclear. The hyporheic assemblage differed strongly between sites and years and was significantly more abundant and diverse where there was minimal disturbance by redd-digging salmon. This study gives an insight into the development of the hyporheos in a primary successional context and our findings are also relevant to new streams created during river engineering.