Fine-scale Dynamics of Marine Foodwebs in the Western Aleutian Islands

Authors: Douglas Causey, Veronica Padula, Rachel McKenna, University of Alaska Anchorage.

The Arctic regions are experiencing rapid change in marine and terrestrial environments from many sources, primarily caused by climate change and anthropogenic impacts of increased development and pollution. Even in the low Arctic – such as the southern Bering Sea and Aleutian Islands – multiple lines of evidence point to rapid environmental change on relatively fine-scales of space and time. A diverse avian community inhabits these region during summer, comprising terrestrial and marine species of several different upper trophic levels. Several endemic species, such as Red-faced Cormorants (Phalacrocorax urile) are currently undergoing dramatic population declines, likely related to climate-related change in food availability and trophic structure of the local marine environment.

This project is focused on the dynamics of climate change on marine bird communities. We use several data sources and analysis techniques, including diet data, stable isotopes, and Bayesian inference, and encompassing current, historical, and prehistoric time periods. We are working to develop an initial understanding of modern upper trophic-level food webs in the Aleutians. This will provide fundamental data for comparison with patterns of the past century and developing models predicting future change. In this study, we are analyzing constituent stable isotopes (e.g. H, C, N, O, S) of blood and feather samples from 16 avian species collected in the far Western Aleutian Islands (the Near, Rat, and Delarof Islands) since 2000, as well as from archival modern specimens collected as early as 1820, and prehistorical bony material dating 5000-6500 ybp.

The Red-faced Cormorant, Red-faced Shag or Violet Shag (Phalacrocorax urile, Cormoran à face rouge, RFCO) is a species of cormorant that is found in the far north of the Pacific Ocean and Bering Sea, from the eastern tip of Hokkaidō in Japan, via the Kuril Islands, the southern tip of the Kamchatka Peninsula and the Aleutian Islands to the Alaska Peninsula and Gulf of Alaska.  Deriving their name from the Latin term corvus marines ("sea raven"), cormorants are highly adapted for underwater hunting. Their bodies are streamlined and somewhat flattened beneath, the neck is long and supple, the wings broad, long, and blunt, and the legs powerful and set far back. Using their lean bodies, they thrust through the water and along the seabed to flush out prey. They range in size from the Pygmy to the goose-sized Great cormorant; the heaviest is the flightless Galapagos cormorant.

The Red-faced Cormorant, Red-faced Shag or Violet Shag (Phalacrocorax urile, Cormoran à face rouge, RFCO) is a species of cormorant that is found in the far north of the Pacific Ocean and Bering Sea, from the eastern tip of Hokkaidō in Japan, via the Kuril Islands, the southern tip of the Kamchatka Peninsula and the Aleutian Islands to the Alaska Peninsula and Gulf of Alaska. Deriving their name from the Latin term corvus marines (“sea raven”), cormorants are highly adapted for underwater hunting. Their bodies are streamlined and somewhat flattened beneath, the neck is long and supple, the wings broad, long, and blunt, and the legs powerful and set far back. Using their lean bodies, they thrust through the water and along the seabed to flush out prey. They range in size from the Pygmy to the goose-sized Great cormorant; the heaviest is the flightless Galapagos cormorant.

Our preliminary results indicate that the community-wide spatial and temporal dynamics of marine bird ecosystems are far greater in the last decade (2009-2012) than has been evident over recent decades. We also find that the magnitude of change is lesser here in the low Arctic (e.g. Westerns Aleutians Islands 53°N) compared to High Arctic coastal marine ecosystems (e.g. 78°N). In particular, we show that the ecological patterns observed within such widespread arctic species as puffins (Fratercula spp.), Northern Fulmars (Fulmaris glacialis), and Black-legged Kittiwake (Rissa tridactyla) indicate diets are strongly perturbed on small geographic and temporal scales of 101 km and decades. Moreover, we find that the variance in environmental and ecological parameters is increasing rapidly over time. We hypothesize that these fine-scale changes are related to mid-scale oceanographic and trophic-level changes, in addition to larger-scale perturbation possibly related to a cascade of climate-related factors.

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2 thoughts on “Fine-scale Dynamics of Marine Foodwebs in the Western Aleutian Islands

  1. Pingback: Upcoming ACZ Workshop (2016) | The Ossiferous Arctic

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