The structure of the water column influences biological productivity in the Arctic, making it unique in its biological properties. It hosts animals such as walruses, whales (belugas, narwhals, and bowheads), and seals. Other marine animals include squid, flatfish, Greenland halibut, worms, snails, crabs, shellfish, and krill. Polychaetes, crustaceans, and bivalve mollusks dominate the benthic macrofauna.
Many microscopic animals such as zooplankton, diatoms, copepods, and foraminifera also live in the freezing waters of the Arctic water column (planktonic) and on the sea floor (benthic). The most important primary producers are phytoplankton. However, the growing season is restricted because of the short summer season, low light angles, and the snow and ice cover. The season is between April and September with a single peak, June to July. With the retreating ice on the shelves during these summer months, an algal bloom is possible near shore.
The Arctic deep sea has been widely ignored because of the thick sea ice. Initial studies show little diversity in this area, with a dominance of deposit feeders. Dominant animals include poly-chaetes, crustaceans, and bivalve mollusks. Occasional tunicates, sponges, cnidarians, ophiuroids, and several species of worms have also been found. Approximately 350-400 species have been found so far in the deep central Arctic Ocean. The long-believed hypothesis that species diversity decreases with higher latitudes is being reconsidered as more species are discovered in the central Arctic. As more research is conducted in this region, the known species diversity is increasing, discounting this outdated theory.
In the Arctic, as in all high latitudes, the food cascading to the bottom of the is the limiting factor for
the benthos, not temperature, as the benthos organisms in the Arctic are adapted to the freezing temperatures. However, they need food for survival and can only obtain it from organic matter produced in the surface waters. In the shallow shelf areas during the ice-free periods, particle transport is abundant. The benthos, therefore, play an important role in the system and production of the Arctic waters.
Although collection of the pelagic organisms has gone on for over a century, many of the taxa are understudied. Only the larger organisms, mostly near shore, are well understood because of their ease of collection. Smaller taxa, deep-water organisms, and the gelatinous forms have been missed by current sampling techniques, therefore, scientists know little about these organisms.
Macro- and megafauna have received the most attention in the Arctic waters, while the meiofauna and microbial communities have been persistently ignored. This is, more often than not, because of sampling techniques and the ease of capture in the ice-filled environment. However, in terms of the quantity of organisms, there are more microbial animals per square meter than there are megafauna. There are still many species of microscopic organisms that have not been identified and further study of the microbial world will enhance knowledge of the Arctic system.
Polar bears also venture into the frozen waters, using floating icebergs as islands on which to rest before venturing onward. With the warming of the Earth and Arctic climate change, these icebergs are not as prevalent as they once were, and the polar bears are having difficulty without these resting places. In addition to the deteriorating climate, there are still many mysteries about marine life, both macro- and microscopic, and how the interaction of these many species sustains an environment that allows life to flourish despite the harsh conditions.
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