Glacier Bay National Research Articles

Development and Decline of a Silurian Stromatolite Reef Complex, Glacier Bay National Park, Alaska

Development and Decline of a Silurian Stromatolite Reef Complex, Glacier Bay National Park, Alaska

Macroinvertebrate community succession in Wolf Point Creek, Glacier Bay National Park, Alaska

Summary 1 Macroinvertebrate community development in Wolf Point Creek in Glacier Bay National Park, Alaska formed by ice recession was investigated from 1991 to 1994 as part of a long-term study of colonization now exceeding 20 years. Chironomidae, the first taxon to colonize the stream, still dominated the community comprising 75–95% by number, but species succession was apparent. 2 Species richness in August increased from five species in 1978 to 11 in 1991 and 16 in 1994. 3 Diamesa species, abundant in 1978 at densities exceeding 2 750 m-2, were not collected in 1994, while Pagastia partica dominated the community with densities exceeding 10 000 m-2. 4 Sixteen taxa, never previously collected, colonized the stream between 1991 and 1994 including representatives of Coleoptera, Muscidae, Trichoptera, and the first noninsect taxon, Oligochaeta. Colonization by new taxa was associated with an increase in summer water temperature and the development of riparian vegetation. 5 Inter-specific competition is suggested as a possible factor in species succession and is incorporated into a taxa richness model of community development in postglacial streams incorporating stable and unstable channels.

Phylogeography of black bears (Ursus americanus) of the Pacific Northwest

Phylogeographic study across codistributed taxa provides temporal and spatial perspectives on the assemblage of communities. A repeated pattern of intraspecific diversification within several taxa of the Pacific Northwest has been documented, and we contribute additional information to this growing data set. We analyzed variation in two mitochondrial genes (cytochrome b and control region) for the black bear (Ursus americanus) and expand previous analyses of phylogeographic variation. Two lineages (coastal and continental) exist; the coastal lineage extends along the Pacific coast from the Takhin River north of Glacier Bay National Park, southeast Alaska, to northern California, whereas the continental lineage is more widespread, occurring from central Alaska to the east coast. Both lineages occur along the coast of southeast Alaska, where interlineage divergence ranged from 3.1 to 3.6% (uncorrected p distances). Multiple lineages of other species have also been identified from southeast Alaska, indicating a complex history for the assembly of biotic communities along the North Pacific coast. The overlapping of the distributions of the black bear lineages with those of other birds and mammals suggests comparable routes of colonization.

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

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.

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

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.

Influence of Riparian Vegetation on Invertebrate Assemblages in a Recently Formed Stream in Glacier Bay National Park, Alaska

Influence of the development of riparian vegetation on benthic invertebrate assemblages was analyzed in a recently formed stream in southeast Alaska. Several features of riparian interaction were documented: 1) invertebrate use of willow catkins entering streams in summer, 2) invertebrate use of submerged alder roots as a substrate for attachment and as a source of building material for caddisfly cases, and 3) retention of leaf litter by salmon carcasses. The development of riparian vegetation markedly influenced colonization of the stream by certain invertebrate taxa and thereby played an important role in the successional sequence of macroinvertebrates and overall assemblage development in this new stream.

The role of competition in invertebrate community development in a recently formed stream in Glacier Bay National Park, Alaska

New streams formed following ice recession in Glacier Bay National Park, southeastern Alaska allow insights into the role of abiotic and biotic interactions in the assemblage of benthic communities. Reductions in abundance of a pioneer chironomid colonizer, Diamesa alpina/lupus, in one new stream, Wolf Point Creek, is considered to be a result of competitive interactions with subsequent colonizers, as opposed to intolerance of warmer water temperature as previously suggested. Reduced densities of potential competitors (25–50 larvae per 500 cm2) in a cobble transplant experiment between streams, allowed persistence of D. alpina/lupus at low densities. In addition, significantly more D. alpina/lupus larvae emigrated from artificial stream channels containing other chironomid taxa than channels without potential competitors while there was no significant correlation of emigration with water temperature. A small number of D. alpina/lupus transplanted from a cold stream (4–6 °C) survived at water temperatures of 10–15 °C for 1 week. These results infer that interference competition is the causal mechanism in the decline of D. alpina/lupus. Complete exclusion of D. alpina/lupus from the stream has not occurred and water temperature may play a role in partitioning D. alpina/lupus from other taxa on a temporal or a spatial basis.

Meiobenthic arthropod communities in new streams in Glacier Bay National Park, Alaska

Meiobenthic arthropod community structure (comprising species of chydorid and macrothricid Cladocera, cyclopoid and harpacticoid Copepoda, Ostracoda and Hydrachnida) was examined along a chronosequence of five streams of different ages (20–150 years) in Glacier Bay National Park to determine whether meiobenthic arthropod colonisation had occured and successional patterns were evident. Meiobenthic arthropod communities were found in all five streams, indicating that initial colonisation was rapid, and there was clear evidence of successional patterns at both the species and the community level. Meiobenthic arthropod species richness and density rose along the chronosequence and was correlated with increasing stream age and CPOM and increasing channel stability as measured by Pfankuch's Index. These trends were largely driven by the Ostracoda and harpacticoid copepods. The latter group also exhibited a distinct shift in species composition with increasing stream age. Initial meiobenthic arthropod colonisation may be facilitated by the large breeding colonies of Canada geese that occur on the wetlands associated with newly deglaciated areas of Glacier Bay. Processes driving meiobenthic arthropod community succession in newly deglaciated streams are likely to be complex and may involve water temperature, channel stability, riparian zone development and CPOM / woody debris influx to the stream. Rapid meiobenthic arthropod colonisation and subsequent succession may have important implications for fish colonisation, and subsequent establishment in new streams as meiobenthic arthropods are important food items for juvenile fish.

Insights into nitrogen and carbon dynamics of ectomycorrhizal and saprotrophic fungi from isotopic evidence.

The successful use of natural abundances of carbon (C) and nitrogen (N) isotopes in the study of ecosystem dynamics suggests that isotopic measurements could yield new insights into the role of fungi in nitrogen and carbon cycling. Sporocarps of mycorrhizal and saprotrophic fungi, vegetation, and soils were collected in young, deciduous-dominated sites and older, coniferous-dominated sites along a successional sequence at Glacier Bay National Park, Alaska. Mycorrhizal fungi had consistently higher δ15N and lower δ13C values than saprotrophic fungi. Foliar δ13C values were always isotopically depleted relative to both fungal types. Foliar δ15N values were usually, but not always, more depleted than those in saprotrophic fungi, and were consistently more depleted than in mycorrhizal fungi. We hypothesize that an apparent isotopic fractionation by mycorrhizal fungi during the transfer of nitrogen to plants may be attributed to enzymatic reactions within the fungi producing isotopically depleted amino acids, which are subsequently passed on to plant symbionts. An increasing difference between soil mineral nitrogen δ15N and foliar δ15N in later succession might therefore be a consequence of greater reliance on mycorrhizal symbionts for nitrogen supply under nitrogen-limited conditions. Carbon signatures of mycorrhizal fungi may be more enriched than those of foliage because the fungi use isotopically enriched photosynthate such as simple sugars, in contrast to the mixture of compounds present in leaves. In addition, some 13C fractionation may occur during transport processes from leaves to roots, and during fungal chitin biosynthesis. Stable isotopes have the potential to help clarify the role of fungi in ecosystem processes.

Review: Land Reborn: A History of Administration and Visitor Use in Glacier Bay National Park and Preserve, by Theodore Catton

Review: <i>Land Reborn: A History of Administration and Visitor Use in Glacier Bay National Park and Preserve</i>, by Theodore Catton

The Border Ranges fault system in Glacier Bay National Park, Alaska: evidence for major early Cenozoic dextral strike-slip motion

The Border Ranges fault system of southern Alaska, the fundamental break between the arc basement and the forearc accretionary complex, is the boundary between the Peninsular–Alexander–Wrangellia terrane and the Chugach terrane. The fault system separates crystalline rocks of the Alexander terrane from metamorphic rocks of the Chugach terrane in Glacier Bay National Park. Mylonitic rocks in the zone record abundant evidence for dextral strike-slip motion along north-northwest-striking subvertical surfaces. Geochronologic data together with regional correlations of Chugach terrane rocks involved in the deformation constrain this movement between latest Cretaceous and Early Eocene (~50 Ma). These findings are in agreement with studies to the northwest and southeast along the Border Ranges fault system which show dextral strike-slip motion occurring between 58 and 50 Ma. Correlations between Glacier Bay plutons and rocks of similar ages elsewhere along the Border Ranges fault system suggest that as much as 700 km of dextral motion may have been accommodated by this structure. These observations are consistent with oblique convergence of the Kula plate during early Cenozoic and forearc slivering above an ancient subduction zone following late Mesozoic accretion of the Peninsular–Alexander–Wrangellia terrane to North America.

Norm congruence among tour boat passengers to Glacier Bay national park

Personal and social norms of visitors are receiving increased attention as a means of setting standards of quality in parks and recreation areas. However, if visitors’ evaluations and behavior are not congruent with norm‐based standards, then this approach may lack validity. This study tests norm congruence among tour boat passengers to Glacier Bay National Park. A sample of tour boat passengers was surveyed to determine (a) personal norms for the number of watercraft and aircraft seen, (b) number of watercraft and aircraft seen, and (c) the effect of watercraft and aircraft seen on enjoyment. Findings reveal the extent to which evaluations of seeing water‐craft and aircraft are congruent with data on personal norms. Several theoretical and methodological issues that help interpret study findings are discussed.

Causes and Ecosystem Consequences of Multiple Pathways of Primary Succession at Glacier Bay, Alaska

The classic account of primary succession inferred from a 220—yr glacial retreat chronosequence at Glacier Bay National Park, Alaska was compared to reconstructions of stand development based on tree—ring records from 850 trees at 10 sites of different age. The three oldest sites (deglaciated prior to 1840) differ from all younger sites in the early recruitment of Sitka spruce (Picea sitchensis), the presence of western hemlock (Tsuga heterophylla), and the inferred importance of early shrub thickets. The nitrogen—fixing shrub Sitka alder (Alnus sinuata) has been an important and long—lived species only at sites deglaciated since 1840. Black cottonwood (Populus trichocarpa) has been an overstory dominant only at sites deglaciated since 1900. These single—species additions or replacements distinguish three pathways of vegetation compositional change which are segregated spatially and temporally. The communities of different age at Glacier Bay do not constitute a single chronosequence and should not be used uncritically to infer long—term successional trends. Among—site differences in texture and lithology of soil parent material cannot account for the multiple pathways. However, distance from each study site to the closest seed source of Sitka spruce at the time of deglaciation explains up to 58% of the among—site variance in early spruce recruitment. Multiple pathways of compositional change at Glacier Bay appear to be a function of landscape context, which, in conjuction with species life history traits (dispersal capability and generation time), affects seed rain to newly deglaciated surfaces and thereby alters the arrival sequence of species. Differences among the pathways probably include long—term differences in ecosystem function resulting from substantial accumulation of nitrogen at sites where nitrogen—fixing shrubs are important.

Colonization and succession of invertebrate communities in a new stream in Glacier Bay National Park, Alaska

SUMMARY1. Invertebrate colonization of a new stream following glacial recession is documented for a 12 year period from 1978 to 1990.2. Invertebrates, particularly Chironomidae, displayed site‐specific temporal succession over the study period, at the end of which a number of the pioneer colonizers were no longer collected.3. Maximum species richness was found in 1988, whereas total invertebrate density was greatest in 1978, 10 years earlier.4. Water temperature appeared to be the most significant factor determining the year of colonization of invertebrate taxa. As a result, deterministic trends were apparent in patterns of invertebrate colonization and succession.5. Salmonids first colonized the stream in 1988. Dietary analyses of juvenile Dolly Varden (Salvelinus malma) showed preferential selection for blackfly and small chironomid larvae.

Changes in Productivity and Distribution of Nutrients in a Chronosequence at Glacier Bay National Park, Alaska

By assessing productivity and ecosystem nutrient distribution, this work extends the early classic studies of the influence of N 2 fixers and conifers on soil development and nitrogen accumulation in a primary succession chronosequence at Glacier Bay, Alaska, U.S.A. The nitrogen-fixing shrub Alnus sinuata (Sitka alder) dominates recently deglaciated sites along Glacier bay but is replaced by Picea sitchensis (Sitka spruce) after about 80 years. While Alnus dominated, soil organic matter and nitrogen (N) increased very rapidly (...)

Stream Development in Glacier Bay National Park, Alaska, U.S.A.

The effects of hydraulics, sediment supply, channel condition, and riparian vegetation on stream development were examined in a chronosequence of five streams in Glacier Bay National Park where rapid retreat of glacial ice has exposed landscapes of different ages within a confined region. The youngest stream, Wolf Point Creek (deglaciated around 1955), is fed by a remnant glacier and had the highest suspended sediment concentrations of all streams (103-111 mg L-1 at baseflows). The main channel of Wolf Point Creek was relatively wide and stable because of the peak flow buffering effects of the remnant glacier and associated lake. However, the floodplain was periodically inundated and only sparsely vegetated and highly braided. The study reach at Nunatak Creek (deglaciated around 1950) was actively downcutting through fine glacial outwash deposits creating a deeper thalweg and redepositing some material near channel margins. About 100 yr after deglaciation (Ice Valley stream), woody riparian vegetation begins to stabilize streambanks and becomes established on gravel bars where it provides potential sites for incipient woody debris dams. The Ice Valley channel shows only minimal degradation. The increased accumulation of woody material and the subsequent colonization of gravel bars by alder and willow have begun to increase channel and bank stability and pool formation in Berg Bay South (deglaciated around 1830). Berg Bay South appears to be near equilibrium with respect to sediment supply and transport. Berg Bay North, a stream of similar age to Berg Bay South, stabilized more rapidly because of the buffered peak flows and greater sediment trapping efficiency attributed to the lakes and bogs in the north stream system. Fish habitat improves as postglacial streams develop: pools begin to form, riparian cover increases, and sediment transport decreases.

Stream Development in Glacier Bay National Park, Alaska, U.S.A.

Stream Development in Glacier Bay National Park, Alaska, U.S.A.

Salmonid colonization of new streams in Glacier Bay National Park, Alaska

Abstract. Following the rapid recession of a neoglacial ice sheet within the last 250 years, colonization of recently deglaciated streams by salmonid fishes was investigated in Glacier Bay National Park, south-eastern Alaska. The primary factors governing the establishment, species diversity composition and abundance of salmonids in Glacier Bay streams were water temperature, sediment loading and stream discharge. No salmonids were found in the turbid meltwater streams emerging from retreating ice. Coho, Oncorhynchus kisutch (Walbaum), and sockeye, Oncorhynchus nerka (Walbaum). salmon and Dolly Vardcn, Salvelinus malma (Walbaum), charr were the first salmonids to colonize the youngest clearwater stream. Juvenile Dolly Varden were more abundant than juvenile coho salmon in the most recently formed clearwater stream because of the characteristic absence of pool habital. Densities of juvenile coho salmon were six times greater in a stream with a series of lakes compared with a stream of similar age without lakes. Future advancement of salmonid stocks will probably depend upon the rate and extent of the development of riparian vegetation and inputs of large woody debris from the developing forest to provide further instream cover, habitat variation and channel stabilization.

Nitrification, soil acidification and streamwater chemistry following deglaciation, glacier bay national park and preserve

A major tool used in the assessment of anthropic atmospheric effects on aquatic and terrestrial ecosystems is biogeochemical nutrient cycling and budgets. However, to be most effective such study should be done in an ecosystem context. Also some assessment of natural variation in factors affecting nutrient cycling must be in place before trends, often subtle and long-term, attributable to man can be statistically quantified. The input and output balance of chemical species in watershed ecosystems is considerably influenced by ecosystem succession. It is hypothesized that during primary ecosystem succession chemical element output is initially relatively high due to rapid acidification and lack of plant uptake. Outputs decline during the period of high ecosystem productivity and biomass accumulation, and they again rise during late successional stages to approximate inputs from precipitation weathering, and aerosol capture. Glacier Bay provides a unique opportunity to quantify many mechanisms responsible for variation in nutrient cycles without the need for site manipulation. This is especially true for quantifying the rate and magnitude of natural acidification in ecosystems. The park has a spectrum of watersheds differing in stage of primary and secondary succession following deglaciation. These sites are not now subjected to or altered by anthropic atmospheric inputs. The objectives of this research were (1) determine the rate of soil chemical change which occurs following deglaciation, (2) relate soil acidification to presence of organic matter, soil NO inf3 (sup-) , and total N, (3) estimate the downward movement of ionic species within the soil profiles with increasing acidification from advancing plant succession, and (4) determine if such processes and ionic movements might be reflected in watershed stream ionic outputs. We studied five watersheds ranging from 40-350 years since deglaciation. Soil samples were collected and lysimeters installed in seven vegetation successional stages following deglaciation. An anion of ecological importance and a common air contaminant is NO inf3 (sup-) , and its discharge in streamflow from early successional ecosystems was found to be high. The terrestrial biota in such systems was dominated by Alnus sinuata, a major nitrogen fixer. Stream discharge of NO inf3 (sup-) suggested that early successional ecosystem N fixation exceeded biotic uptake. This was confirmed by examining NO inf3 (sup-) in soil extractions and lysimeters. This process was particularly evident beneath >20-year old Alnus (forty years since deglaciation). concurrent with increased NO inf3 (sup-) concentrations below the rooting zone was increased H(+) which increased 100x during 25 years of primary succession. This natural acidification from a mobile NO inf3 (sup-) ion resulted in an pronounced increase in soil base cation leaching and mobilization of aluminium in the soil profile. The magnitude and short time required for such acidification greatly exceeded anything projected or modeled for systems impacted by anthropic inputs. Stream SO inf4 (sup2-) concentrations also were high relative to precipitation inputs suggesting mineralization of sulfur within the ecosystem and/or poor soil adsorption of SO inf4 (sup2-) . This is an important finding in such ecosystems where cation nutrient ion levels are often very low. Should atmospheric inputs of SO inf4 (sup2-) increase additional loss of cations appears imminent. These data suggest that most early successional ecosystems at Glacier Bay would be sensitive to anthropic inputs of both NO inf3 (sup-) and SO inf4 (sup2-) . This is unusual in other ecosystems where many conserve ionic NO inf3 (sup-) inputs, and older systems have considerable SO inf4 (sup2-) adsorption capacity. The effect of any increased atmospheric inputs of these ions would be accelerated cation leaching and ecosystem acidification.

Colonization and ecological development of new streams in Glacier Bay National Park, Alaska

SUMMARY 1. Colonization and ecological development of postglacial freshwater communities was investigated in Glacier Bay National Park, south‐eastern Alaska, following the rapid recession of a Neo‐glacial ice sheet within the last 250 years.2. Environmental variables shown to be most significant in stream development were temperature, flow regime and sedimentation.3. The Chironomidae (Diptera) were the pioneer invertebrate colonizers of newly emergent streams arising as meltwater from receding ice sheets and displayed a distinct pattern of succession with stream maturity.4. Ephemeroptera and Plecoptera colonized warmer clearwater streams, but Trichoptera had a minimal role in invertebrate community development.5. Establishment and production of salmonid fish populations in the new streams related principally to stream flow and sediment characteristics.6. Future pathways along which the streams may develop is probably dependent on the degree of large organic debris input.7. Stream development, structure and function are summarized including reference to theories of ecosystem development, ecological succession and community stability.