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Food webs

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Food webs show the complexity of trophic relationships in communities.

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Bear Island Arctic Food Web

Bear Island (Bjørnøya) is a small, remote island in the Arctic Ocean, located between mainland Norway and the Svalbard archipelago. In 1921, the ecologist Charles Elton conducted one of the first systematic studies of food web relationships here, helping to establish the foundations of modern ecology. The island lies at 74°N latitude and experiences extreme seasonal variation in daylight, with continuous daylight in summer and polar night in winter. The harsh climate supports a relatively interconnected but straightforward community of organisms spanning terrestrial, freshwater and marine habitats.

https://maps.app.goo.gl/wMV23VqvgrfkskAL9

Species Scientific Name Category Diet / Food Sources
Mosses Bryophyta (various species) Producer Photosynthesis
Lichens Cladonia spp., Cetraria spp. Producer Photosynthesis
Arctic willow Salix arctica Producer Photosynthesis
Phytoplankton Various species Producer Photosynthesis
Springtails Collembola (class) Detritivore Decaying plant matter, fungi, algae
Crane flies Tipula spp. Detritivore / Herbivore Decaying plant matter, moss, plant roots
Mites Acari (subclass) Detritivore / Predator Decaying matter, fungi, springtails
Spiders Araneae (order) Predator Springtails, crane flies, mites
Svalbard rock ptarmigan Lagopus muta hyperborea Herbivore Arctic willow (buds and leaves), lichens, mosses
Snow bunting Plectrophenax nivalis Omnivore Seeds (from Arctic willow), crane flies, spiders
Purple sandpiper Calidris maritima Carnivore Springtails, crane flies, mites, marine invertebrates
Barnacle goose Branta leucopsis Herbivore Mosses, Arctic willow (leaves)
Glaucous gull Larus hyperboreus Omnivore Bird eggs and chicks (ptarmigan, snow bunting, barnacle goose), Arctic cod, marine invertebrates, carrion
Arctic skua Stercorarius parasiticus Carnivore Bird eggs and chicks (ptarmigan, snow bunting, barnacle goose), Arctic cod
Zooplankton Calanus spp. Herbivore Phytoplankton
Arctic cod Boreogadus saida Carnivore Zooplankton
Ringed seal Pusa hispida Carnivore Arctic cod
Arctic fox Vulpes lagopus Omnivore Bird eggs and chicks (all bird species), ptarmigan, snow bunting, barnacle goose, berries (occasionally), seal carcasses
Polar bear Ursus maritimus Carnivore Ringed seal, bird eggs, carrion
  1. Use the information below to construct a food web showing the trophic relationships in the Bear Island ecosystem.
    1. Producers should be placed at the bottom of your food web.
    2. Arrows point from the food source to the consumer (showing direction of energy flow).
    3. Some species feed at multiple trophic levels.
    4. The food web connects terrestrial, freshwater and marine subsystems.

  2. The arctic fox has been described as a "generalist" predator. Suggest one advantage of being a generalist feeder in the Arctic environment.

  3. Compare your food web to a simple food chain (e.g., phytoplankton → zooplankton → Arctic cod → ringed seal → polar bear). What additional information does the food web show that the food chain does not?

  4. If a disease killed all the crane flies on Bear Island, identify three species that would be directly affected. Would all three species be affected equally? Explain your reasoning.

Biomass

Stick insect experiment [Worked example]