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Arctic Ecosystem

With a unique, complex food web, the Arctic Ecosystem is driven by the physical environment cycles of solar radiation and temperature. This results in short production periods that are essential for global chemical cycles (carbon cycle) (Laidre et al., 2007). Primary producers bloom in spring due to high solar radiation input.  Ice Algae and Phytoplankton are the main primary producer (photosynthesizing organism that uses carbon dioxide and water to produce organic matter). Ice Algae is the only algal species that lives in sea ice. Ice Algae and Diatoms (phytoplankton) dominate the underside of the ice sheets and in pockets of water between ice crystals in pack ice(Berta et al., 2005). They are both primary producers and keystone species of the Arctic marine ecosystem and are therefore at the base of all polar food chains including the Bowhead food chain (Figure 5). Thus Ice Algae and phytoplankton (Diatoms) are essential for all polar inhabitants and Arctic life (Laidre et al., 2007).

The next step in the Bowhead food chain is a primary consumer, Zooplankton. Zooplankton consumes small particles such as Ice Algae, phytoplankton or bits of dead material (detritus). Zooplankton size usually ranges from near-microscopic to several centimeters. It is found throughout the water column down to the seabed.  Zooplankton includes copepods (calanus sp.), euphausiids (thysanoessa sp.), mysids (mysis sp.) and krill (Blix 2005).  The most abundant Arctic zooplankton are krill and copepods.

The largest zooplankton predator in the arctic ecosystem is the Bowhead whale (apex predator) (Laidre et al., 2007). The Bowheads ability to survive near and under the ice sheet means that they are not in direct competition with other Baleen Whales. Bowheads filter feed in Arctic waters all year round to obtain their food; krill, copepods, euphausiids, mysids, invertebrates, and small fish (Moore and Laidre, 2006). They are specially adapted to efficiently filter feed (Blix, 2005). They use the zooplankton for nutritional gain and building their insulation layer (fat deposit) (Laidre et al., 2007). Bowhead whales are the apex predator that feeds on the grazers (mainly krill and copepods) preventing them from over-grazing the primary producers (Berta et al., 2005). Once Bowhead whales die they provide longer-term sustenance for Arctic land predators, maintaining arctic ecosystem balance.

Figure 5: Arctic Environment and the key organisms in the Arctic Food Wed. The red line indicate the food chain of the Bowhead Whale. The orange line leads to the phytoplankton that also live in the ice., they are also primary producer. Image by Polar Discovery, Woods Hole Oceanographic Institution.

Figure 5: Arctic Environment and the key organisms in the arctic food web. The red line indicates the food chain of the Bowhead Whale. The orange line leads to the phytoplankton that can also live in the ice (diatoms). (Source: Polar Discovery, Woods Hole Oceanographic Institution).

 

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