Colonization and development of stream communities across a 200-year gradient in Glacier Bay National Park, Alaska, U.S.A.

Abstract

In May 1997, physical and biological variables were studied in 16 streams of different ages and contrasting stages of development following glacial recession in Glacier Bay National Park, southeast Alaska. The number of microcrustacean and macroinvertebrate taxa and juvenile fish abundance and diversity were significantly greater in older streams. Microcrustacean diversity was related to the amount of instream wood and percent pool habitat, while the number of macroinvertebrate taxa was related to bed stability, amount of instream wood, and percent pool habitat. The percent contribution of Ephemeroptera to stream benthic communities increased significantly with stream age and the amount of coarse benthic organic matter. Juvenile Dolly Varden (Salvelinus malma) were dominant in the younger streams, but juvenile coho salmon (Oncorhynchus kisutch) abundance was greater in older streams associated with increased pool habitat. Upstream lakes significantly influenced channel stability, percent Chironomidae, total macroinvertebrate and meiofaunal abundance, and percent fish cover. Stable isotope analyses indicated nitrogen enrichment from marine sources in macroinvertebrates and juvenile fish in older streams with established salmon runs. The findings are encapsulated in a conceptual summary of stream development that proposes stream assemblages to be determined by direct interactions with the terrestrial, marine, and lake ecosystems.

Crenic habitats, hotspots for freshwater biodiversity conservation: toward an understanding of their ecology

“…Other studies have also shown successional gradients based on time since major disturbance, e.g. glaciation or river channel migration, owing to the variable dispersal abilities of invertebrates (Hoffsten & Malmqvist 2000;Milner et al 2000;Barquín 2004). However, local-scale factors, such presence/absence of aquatic plants, may also play an important role in structuring spring invertebrate communities in New Zealand.…”

Vegetation succession in deglaciated landscapes: implications for sediment and landscape stability

“…Detailed historical and geological data allow recession of the ice since the Neoglacial maximum to be accurately dated, and catchment age may be deduced from its distance from the retreating glacier termini. Modern day stream and catchment ages have been defined as the time since ice recession from the stream mouth (Milner et al, 2000).…”

Major flood disturbance alters river ecosystem evolution

“…Invertebrates were preserved in 70% ethanol and later separated in the laboratory from detritus and inorganic matter. Macroinvertebrates were identified using Merritt and Cummins 26 and Chironomidae larvae were identified using methods outlined in Milner et al 27 . Meiofauna were identified using Thorp and Covich 28 and Smith 29 .…”

“…Meiofauna were identified using Thorp and Covich 28 and Smith 29 . Adult pink salmon spawners were estimated using the average of counts by two observers walking the length of the stream, and juvenile coho salmon densities with minnow traps baited with salmon eggs and fished for 2h 27 .…”