Piepenburg 2005

Piepenburg D. 2005. Recent research on Arctic benthos: common notions need to be revised. Polar Biology 28: 733-755.

This author reviews the broad scale ecology of Arctic marine benthic environments, with emphasis on energy and matter flows and biodiversity patterns. There is an early summary of what was known or supposed about Arctic benthic biodiversity in the late 1980s and early 1990s, before major shifts in research took place. With the breakup of the Soviet Union and concommitent opening to Western researchers of the Siberian Arctic, and an increased public awareness of polar issues, the mid-to-late 1990s saw a large increase in scientific attention on the Arctic benthos.

No single clear definition of “Arctic” for the marine realm is recognized, but this author follows the work of Zenkevitch (1963; original in Russian 1955), which broadly defines the Arctic marine as the Arctic Ocean proper, plus its adjacent seas including the northern shorelines of Eurasia and North America, as well as the continental shelves of Greenland, Baffin Bay, and everything north of the “Polar Front” of the Barents and Bering seas. A map of these areas is provided in figure 1.

While the Arctic Ocean proper is almost entirely covered by permanent sea-ice, the adjacent Arctic seas are primarily characterized by very low but relatively constant water temperatures, long-lasting seasonal ice cover, and very pronounced seasonal fluctuations in insolation and, hence, primary production. There are broad continental shelves underlying several Arctic seas such as the Laptev Sea of central Siberia, and these shelves receive a large amount of input from rivers, approximately 10% of the total global river outflow. The broad width of several of these shelves prevents movement of this terrestrial input into the deeper basins of the central Arctic ocean.

The Arctic as a low-temperature ecosystem is much younger than that of Antarctica. While a cold circumpolar current formed around Antarctica perhaps 23mya, the Arctic ocean was temperate until a drastic fall in sea temperatures in the Pliocene about 4mya. During that recent 4my, many areas of Arctic shelf have been either dry due to sea level falls, or covered by glaciers, effectively removing the benthic faunas. Many Antarctic shelf areas also probably experienced glaciation, sometimes to surprisingly deep depths of hundreds of meters. This pattern of repeated extermination and recolonization may imply that Arctic organisms are particularly resilient in the face of environmental change.

Work since the increase in Arctic research has generally supported but modified pre-existing views of Arctic ecology. Both the Arctic and Antarctic benthos can be considered to harbor intermediate biodiversity, though the Antarctic still appears to be slightly more diverse. Disturbances once thought to be unique to the Arctic (such as iceberg bottom-scouring) have been found at significant frequencies in the Antarctic. Most Arctic organisms appear to be wide-spread boreal-Arctic species rather than endemic, while much more of the Antarctic biota is endemic to areas south of the Antarctic convergence.

The major faunal groups of the Arctic benthos are:
On fine sand and mud, bivalves and polychaetes.
On coarse grained sediments, gammaridean amphipods.
On many shelf and slope habitats, brittle stars, which can reach carpet-like population densities.
In the Barents Sea, sea urchins
In the Laptev Sea, sea cucumbers and bivalves
In the Bearing and Chukchi Seas, sea stars and crustaceans, including dense populations of ampeliscid amphipods in some areas
In the deep ocean basins of the Arctic Ocean proper, deposit feeding polychaetes, crustaceans, and bivalves.

“Pelago-benthic coupling” is a blanket term coined by Hargrave (1973) to refer to the downward flux of matter and energy from the water column to the seabed, and related processes of upwelling and other mixing effects. This coupling seems especially strong and important in the Arctic ocean, with meso-scale variations (10-100km) driven by local bottom topology, currents, ice cover dynamics (including polynyas), et cetera. The stronger coupling in the Arctic appears to be driven by a slower response of zooplankton to seasonal changes in phytoplankton, allowing more “fresh” captured carbon to reach the sea floor.

The deep Arctic Ocean basins are apparently relatively uncoupled from adjacent shelf areas, with most productivity in the basins driven by very strong pelago-benthic coupling. Nonetheless, the Arctic Ocean supports productivity about an order of magnitude higher than previously suspected, in part due to the role of ice-bound algae and stochastic large inputs of food.

This is a useful review paper that introduces many of the issues of Arctic marine biology at an ecosystem scale. There are useful links here to other community ecology considerations and to deep ocean research programs.