Biotic components

Bacteria and viruses

Thu, 03 Dec 2009 08:50:27 +0000

In the biogeochefmical cycles of the ocean, a multitude of processes are catalyzed by Bacteria and Archaea, and the fufnctioning of these cycles in the Barents sea do not differ qualitatively from those at lower latitudes. The carbon cycle may well serve as an example of the biogeochemical cycles (Figure 2.4.1). The heterotrophic procaryotes, denoted bacteria for simplicity, are the major degraders of dissolved organic carbon (DOC), which is their principle source of energy and carbon. At high latitudes, DOC accumulates in the photic zone during the productive season, and the concentration decreases in September/October due to the combination of bacterial degradation and physical mixing processes (Børsheim and Myklestad 1997; Børsheim 2000).

Phytoplankton

Thu, 03 Dec 2009 08:52:13 +0000

As the main primary producer, phytoplankton is an important link between the physical and chemical elements and higher tropic levels in the marine food web. Changes in the environment could affect the annual succession and species composition of the phytoplankton, as well as the overall primary production in the area. Phytoplankton monitoring will give important information regarding biological changes on the lowest level in the food web with environmental impact and climatic changes.

Phytoplankton - Species composition and diversity

Thu, 03 Dec 2009 08:54:18 +0000

At the moment, there are 307 distinguishable species of pelagic micro algae registered in the Barents Sea, not including multiple subspecies and varieties (Makarevich, Larionov, 1992; Matishov et al., 2000). Taxonomically, 7 of them belong to the golden algae, Cryophyte, 148 – diatoms, 123 – dynophytes, 5 – green algae, 4 – to Haptophyta division, 8 – to Prasinophyta division and 6 species – to Euglenophyta and Cryptophyta algae. 49 species (16%) are oceanic, 178 (58%) – neritic, 39 (12.7%) – panthalassal species, 17 (5.5%) can be clearly defined as a fresh water species, however, they are typical representatives of the Barents Sea pelagic algae flora, abundant in estuaries and even in the open sea. 14 species (4.6 %) do not represent typical planktonic species, but belong to the microphytobenthos; however, they are regularly registered in the pelagic coastal zone and thus can be included in the list. Other species can’t be given an ecological characteristic.

Phytoplankton - Seasonal succession

Thu, 03 Dec 2009 08:55:36 +0000

According to several studies, general structure of the succession cycle of phytoplankton in the Barents Sea could be split up into different phases covering a time period of the year. These phases will be the winter phase (low activity), spring phase (covering the onset of and spring bloom maximum), summer phase, and the autumn phase. These periods shows characteristic species composition, abundance, and production.

Phytoplankton - Open water and ice edge zone

Thu, 03 Dec 2009 08:56:57 +0000

During the winter phase from November to February, there is low diversity and low production, with chlorophyll concentrations close to zero. The lowest levels are found in the ice free areas in the northern parts. During this period there are sufficient nutrients for growth, but the absent of clear stratification and light prevent large production. The species that are present are cosmopolitan representatives of dinoflagellates (Dinophyceae), large armed forms as Protoperidinium, Ceratium, Dinophysis (Protoperidinium depressum, Ceratium longipes, Ceratium tripos, Dinophysis norvegica) and athecate forms from the genus Gymnodinium and Gyrodinium and occasionally diatoms (Bacillariophyceae).

Phytoplankton - Coastal water

Thu, 03 Dec 2009 08:58:59 +0000

Phytoplankton production in the coastal water is to a large degree influenced by local hydrologic and meteorological factors, including fresh water runoff, wind mixing, tidal regime, as well as ice melting in the coastal areas. As for the open ocean the annual phytoplankton cycle could be divided into phases (winter, spring, summer, and autumn) as for the open areas. Along the Barents Sea coastal line there is large variation in the onset of the different phases along the Russian and Norwegian coast.

Zooplankton

Thu, 03 Dec 2009 09:00:11 +0000

In the Barents Sea ecosystem, zooplankton form a link between phytoplankton (primary producers) and fish, mammals and other organisms at higher trophic levels. The most abundant zooplankton species — calanoid copepods, krill, and hyperiid amphipods — form the major diet of herring, capelin, polar cod, and juveniles of other fish species. The Arctic front in the Barents Sea marks the boundary between the mainly Arctic zooplankton species (Calanus glacialis and Themisto libellula) and the Atlantic/subarctic species (C. finmarchicus, Meganyctiphanes norvegica, Thysanoessa spp and Themisto spp).

Benthos

Thu, 03 Dec 2009 09:01:38 +0000

More than 3,050 species of invertebrates inhabit the benthos of the Barents Sea (Sirenko, 2001). Total fauna biomass, including benthic species, generally increases near the Polar Front, in shallow regions, and near the edges of banks. The richest species diversity is found on sandy silts, and silty-sand floors. Lower biomass occurs in areas with limited upwelling, low primary production, reduced vertical flux, and areas with less suitable substrata caused by heavy sedimentation (e.g. inner parts of glacial fjords).

Benthos - Distribution and fluctuations in benthic communities

Thu, 03 Dec 2009 09:02:41 +0000

There has been a decline in the total biomass of benthos from 1924-1935 to 1968-1970 (Antipova, 1975b). This happened almost throughout the Barents Sea, and has been attributed to climate change by many investigators. The mechanism behind this biomass reduction is not clear, however. Some studies suggest that it is due to a change in faunal distribution during the cold period between the 1960s and 1980s (Figure 2.4.7; Bryazgin, 1973, Antipova, 1975b, Bochkov and Kudlo, 1973), while others invoke declining biomass of resident boreal-arctic species during the 1930s-1960 warm period (Galkin, 1987; Kiyko and Pogrebov, 1997a; Kiyko and Pogrebov, 1998).

Benthos - Distribution of benthic abundance and biomass

Thu, 03 Dec 2009 09:03:52 +0000

The distributional pattern of benthos from different periods shows considerable variability, but demonstrates a number of more consistent features (Figure 2.4.8).

The areas with low abundance (less than 1000 individuals/ m2) and biomass (less than 10-25 g/m2) are usually restricted to bottom depressions such as the western deep-water areas in the Bear Island Channel and Hopen Deep, deep-water areas between Franz Josef Land and the shallow waters of the Novaya Zemlya bank and the deep-water areas in Eastern Basin. The high biomass areas (biomass hotspots) are usually located in connection with considerable rises in sea-floor topography and generally typical for the areas with hard soil and strong currents (Kiyko and Pogrebov, 1997a).