Influence of glacier runoff on ecosystem structure in Gulf of Alaska fjords

Marine ecosystems respond to a range of habitat variability in coastal zones modified by glacial freshwater outflows, biophysical data were collected in three study regions that included four major glacial fjord systems around the Gulf of Alaska. A suite of geographic, oceanographic, nutrient and biological attributes were sampled at these three study regions during peak ice-melt season in summer.

Abstract

To better understand the influence of glacier runoff on fjord ecosystems we sampled oceanographic conditions, nutrients, zooplankton, forage fish, and seabirds within four fjords in coastal areas of the Gulf Alaska. We used generalized additive models and geostatistics to identify the range of glacier runoff influence into coastal waters within fjords of varying estuarine influence and topographic complexity. We also modeled the response of depth-integrated chlorophyll a concentration, copepod biomass, fish and seabird abundance to physical, nutrient and biotic predictor variables. The effects of glacial runoff were traced at least 10 km into coastal fjords by cold, turbid, stratified and generally nutrient-rich near-surface conditions. Glacially modified physical gradients, nutrient availability, and among-fjord differences explained 67 % of the variation in phytoplankton abundance, which is a driver of ecosystem structure at higher trophic levels. Copepod, euphausiid, fish and seabird distribution and abundance were related to environmental gradients that could be traced to glacial freshwater input, particularly turbidity and temperature. Seabird density was predicted by prey availability and silicate concentrations, which may be a proxy for upwelling areas where this nutrient is in excess. Similarities in ecosystem structure among fjords were due to influx of cold, fresh, and sediment-laden water, whereas differences were likely related to fjord topography and local differences in estuarine versus &ocean influence. We anticipate continued changes in the timing and volume of glacial runoff will ultimately alter coastal ecosystems in the future.

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Products

Title	Type
Zooplankton Displacement Volume in Glacier Bay, Alaska, 2004	Data
Zooplankton Biomass Data from Prince William Sound, Icy Bay and Yakutat Bay, Alaska 2010-2011	Data
Modified Herring Trawl Fish Catch Data, Gulf of Alaska Fjords, 2004-2011	Data
Glacier Runoff Biophysical Data in Gulf of Alaska Fjords, 2004-2011	Data
Near-surface Nutrients Data from Gulf of Alaska Fjords, 2004-2011	Data
Marine Bird and Mammal Surveys in Glacier Fjords of Alaska, 2004-2011	Data
Oceanographic Profile Data from Glacier Fjords of Alaska, 2004-2011	Data
Glacier Runoff Biophysical Data in Gulf of Alaska Fjords, 2004-2011	Data
Influence of glacier runoff on ecosystem structure in Gulf of Alaska fjords	Metadata Record
Influence of glacier runoff on ecosystem structure in Gulf of Alaska fjords	Data
Seabird and Forage Fish Ecology Program	Project Website

Contacts

Arimitsu, Mayumi L., 907-364-1593
Piatt, John F., 360.774.0516

Status: completed
Start Year: 2004
End Year: 2011

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Project Sites

Collaborators

FWS - Alaska Region
NPS - Glacier Bay National Park and Preserve

USGS Mission Area and Program

Major Initiatives

USGS - Marine and Freshwater Ecology

Keywords

Biological Classification > Animals/Vertebrates > Fish
Biosphere > Aquatic Ecosystems > Marine Habitat
Biosphere > Aquatic Ecosystems > Plankton > Zooplankton
Oceans > Coastal Processes > Fjords
Oceans > Ocean Temperature > Water Temperature
Oceans > Salinity/Density
Oceans > Salinity/Density > Conductivity