Ecosystem interactions

Ecosystem interaction (Introduction)

admin@barentsportal.com (Administrator) — Wed, 03 Feb 2010 09:14:00 +0000

To understand the overall dynamics of an ecosystem and the way it is affected by human activities, it is important to consider both the impact of natural environmental variations and multispecies interactions. This chapter therefore starts (Abiotic impact) with a description of effects from environmental variation on the biological groups described earlier in chapter Biotic components. It then goes on to describe multipsecies interactions within and between these groups (Biotic interactions).

Abiotic impact

Thu, 03 Dec 2009 10:09:34 +0000

This subchapter describes effects of variation in the physical part of the ecosystem on biological groups. Such links are strong and important for the overall dynamics of the Barents Sea ecosystem. For example, variation in temperature has significant effects on reproduction and recruitment of several of the large fish stocks, and variation in ice cover may have considerable effects on primary productivity.

Abiotic impact - Phytoplankton and zooplankton

Thu, 03 Dec 2009 10:10:35 +0000

Distinctions in quantitative distribution, structure and rates of development of phyto- and zooplankton are connected with the temperature influence, related to ocean currents and the distribution of the ice and the ice edge. Many species of phytoplankton have a rather wide tolerance range for parameters such as temperature and salinity, and also adapt to different levels of light down to its very minimum. However, some of the species in the Barents Sea are connected to colder water or ice edges, with more specific demand in these parameters. For species with a more narrow tolerance in these parameters changes will have a strong effect on their distribution and abundance.

Abiotic impact - Benthos shellfish and squid

Thu, 03 Dec 2009 10:11:57 +0000

Boreal-arctic species dominate the biomass of benthos in the Barents Sea (as well as throughout the arctic shelf), and have an optimum temperature range lying within the long-term temperature mean of the region. According to this latter theory, any deviation from the long-term mean has a negative impact on boreal-arctic species reproduction, abundance, and biomass. Some studies suggest that the decline in total biomass of benthos from 1924-1935 to 1968-1979 (Antipova 1975b) is due to a change in faunal distribution during the cold period between the 1960s and 1980s (Figure 2.6.1; 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).

Abiotic impact - Climate and fish

Thu, 03 Dec 2009 10:13:11 +0000

Climate variability affects fish in a variety of ways and throughout its life cycle. Sea temperature is the variable that has received the most attention from researchers in terms of its effects on both pelagic and demersal fish. Successful individual growth often occurs within a limited thermal range that differs among species and even between developmental stages within the same species. Generally, fish in colder waters tend to exhibit slower individual growth than those in warmer waters (Godø, 2003).

Abiotic impact - Marine mammals

Thu, 03 Dec 2009 10:14:39 +0000

Because marine mammals are large, homeothermic animals, they can cope with significant ranges of water and air temperatures. So, marine mammals residing in, and those that currently migrate seasonally into, the Barents Region are not likely to be directly physiologically challenged by the predicted increases in air and water temperatures. Physical changes in the marine environment are likely to have impacts first and foremost on the animals that depend on sea-ice (e.g. Kovacs and Lydersen, 2008; Kovacs et al., 2009).

Abiotic impact - Seabirds

Thu, 03 Dec 2009 10:16:02 +0000

Physical variation in the Barents Sea is likely to affect seabirds both directly and indirectly. Direct influence works primarily through the effects of temperature, wind and precipitation during the breeding season, and through extreme weather outside the breeding season. Temperature and wind affect the birds’ energy budget, and changes in these factors can impose great energy costs on the birds. Air temperature is partly responsible for determining the onset of breeding for several species.

Biotic interactions

Thu, 03 Dec 2009 10:17:09 +0000

The organisms in the ecosystem are linked through ecological interactions to form a food web, which has several trophic levels: producers (plants) at the lowest trophic level, primary consumers feeding on the producers, secondary producers feeding on the primary consumers and so on up to the apex predators that do not have any predators feeding on them, except for young stages in some species and some species where adults may be killed by humans. Because energy transfer from each trophic level to the next (e.g. the producers to the primary consumers) is not 100% efficient (as a general rule of thumb, the efficiency is only 10%) the biomass and production is highest in the lowest trophic levels and lowest at the highest trophic level.

Biotic interactions - Phytoplankton (and ice algae) - competition and main predators

Thu, 03 Dec 2009 10:18:59 +0000

In the Barents Sea, phytoplankton is the main primary producer sustaining the rest of the food web. Within the phytoplankton community there is a competition for light and dissolved nutrients. The phytoplankton species in the Barents Sea are either pelagic, or linked to the ice edge in a way similar to the ice algae. Phytoplankton blooms in spring and summer and attracts concentrations of intensively feeding secondary producers and their predators. The phytoplankton is both consumed by pelagic zooplankton and sink to the seafloor and sustain benthic feeders there.

Biotic interactions - Benthos, including shrimp and shellfish- competition, main prey and predators

Thu, 03 Dec 2009 10:20:05 +0000

Benthic invertebrates are diverse organisms both in terms of species richness, and feeding and way of life. They are often very habitat specific. Sessile benthic organisms are known to compete for space. Some benthic organisms are filter feeders, some feed on detritus and sediments and some are predators. Decapods are known predators of benthic bivalves, including scallops (Elner and Jamieson, 1979; Arsenault and Himmelman, 1996; Anisimova et al., 2005).