Download - Polar oceans 2014.ppt - natur.cuni.cz
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Ecology of polar oceansLinda Nedbalová
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Arctic Ocean and Southern Ocean
Sea ice extent in the Arctic and Antarctic regions
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Solar radiation is absorbed by surface layers of oceans, causingthermal stratification.
Thermocline – transition to colder denser bottom water, abruptchange of temperature.
Temperature: vertical profile
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Temperature: vertical profile
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Temperature and salinity are related. Highest salinity in subtropical regions, the lowest in polar regions.
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Chemismus mořské vody je velice stabilní, 97.7 % z celkových rozpuštěných minerálních látek připadá na látky, které charakterizují salinitu. Zbývající podíl připadá na dusík a fosfor.pH 7.8 až 8.4.
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• can persist throughout the whole winter• may occur in the same region over a number of years• recurring polynyas • vary greatly in size from a few square kilometres to huge areas
POLYNYAS – persisting areas of open water
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• upwelling of warmer water (sensible-heat or open ocean),• mechanical divergence of the pack ice (latent-heat or coastal)
POLYNYAS – origin and importance
• pathways for heat losses to the atmosphere• provide open water to birds and sea mammals in winter• ice edge with enhanced productivity• important for seasonal hunting of indigenous people
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North Water (NOW) polynya80 000 km2 in northern Baffin Bay, largest Arctic polynya
COMBINED ORIGIN
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Weddell Sea polynya200 000 km2, 1974-1976
OPEN OCEAN
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Ocean ecosystem can be divided into two main systems:1) Open ocean – up to 90% of the world ocean surface, epipelagic,
mesopelagic, bathypelagic, abyssopelagic zones2) Littoral zone – warmer, enriched in nutrients, three main types –
estuaries, steep littoral zone, sandy and stony beaches.
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• productivity changes with depth as result of decreasing light intensity
Vertical profile of light and productivity
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Primary producers of polar oceansPhytoplankton composed mainly by diatoms, haptophytes (coccolithophores), dinoflagellates and cyanobacteria.
Polar oceans belong to the most productive marine ecosystems.
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Productivity of polar oceans• Southern Ocean – productivity higher than in the Arctic
• upwellings of nutrient-rich deep water
• isothermic temperature profile does not prevent mixing
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Polar ocean
food chain and nutrient cycling
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Plankton: size classification
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Polar seas - plankton
phytoplankton maximum in May, zooplanktonin June, high biomass tillthe onset of polar night
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Seasonal development of phytoplankton production
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Phytoplankton of the Arctic Ocean
• dominance of diatoms (Bacillariophyceae), coccolithophores (Coccolithophyceae)
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Emiliania huxleyi
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Southern Ocean• 20 % of the global ocean surface – role in climate regulation
• relatively higher nutrient concentrations, but HNLC regions
• dominance of diatoms
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Iron as limiting nutrient:mesoscale enrichment experiments
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• mesoscale enrichment experiments
•A: IronEx I •B: IronEx II •D: SOIREE •E: EisenEx •G: SEEDS •H: SOFeX •J: Planktos •K: SERIES
• up to 40x increase in phytoplankton biomass
Iron as limiting nutrient
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Iron as limiting nutrient
Gao et al. 2001
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Phaeocystis antarctica
Corethron
Phytoplankton of the Southern Ocean
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Dictyochophyceae
silicoflagellates -Dictyochacold seas,
involved in global cycle of silicon
bioindication of cold periods in the past
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Ice algae
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Fragilariopsis cylindrus
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Zooplankton of the Arctic Ocean
Calanus glacialis• the most important species
• stores a large amount of fat (lipids), which can amount to as much as 70 % of its body mass
• primary food source for Arctic cod, marine birds and bowhead whales
• mature females feed on ice algae
• offsprings feed on phytoplankton
• developmental stages are perfectly synchronised with the two distinct algal bloomsc
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Zooplankton of the Southern OceanAntarctic krill Euphausia superba• key species in the Antarctic ecosystem
• probably the most abundant animal species on the planet in terms of biomass
• filter-feeding on phytoplankton
• swarms reaching densities of 10000–30000 individuals per m3
• length up to 6 cm
• can live for up to 6 years
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Marine benthos in polar regions
• In contrast to terrestrial habitats stable conditions with steady temperatures
• in deeper waters benthos is frequently the most successful form of life
• majority of polar invertebrates are stenothermal
• in littoral and sublittoral zone, mechanical damage by drifting ice can be severe
• not easy to study, observations in situ most valuable – scuba diving, remotely operated vehicles
• diversity underestimated
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Littoral and sublittoral zones• disturbance by scouring ice• sublittoral benthos can only develop fully in polar regions out of reach
of scouring sea ice, around 10 m below low tide level• below these depths an extreme example of severe habitat
transformation is caused by icebergs• without significant mechanical distubŕbance – a productive ecosystem
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Vertical zonation of fauna in the shallow-water benthic community of McMurdo Sound.
A few mobile animals, but no sessile forms, are found in Zone I; the sessile animals inZone II are mostly coelenterates and those in Zone III are predominantly sponges
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D.G. Lillie with siliceous sponges (the one he is holding was probably Rosella villosa) from the Ross Sea; Terra Nova expedition 1911-13. From Huxley (1913) Scott's Last Expedition, Smith, Elder & Co., London. Supplied by Scott Polar Research Institute.
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Benthic macroalgae: maximal depth ?• below 40 m growth is sparse
• there are records of macroalgae from depths > 100 m
• photosynthetic growth was considered as possible at irradiances around 1 umol/m2/s
• deep water red algae seem to survive at 0.05 umol/m2/s
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The most southern occurrence of benthic macroalgal assemblages was described from Ross Sea (77°30´ S.), where sea ice is 2 meters thick and persist 10 months per year.
Characteristic vertical zonation – 3 dominant species of red algae prefer different depths>Iridaea cordata around 3,5 m, Phyllophora antarctica 12 m Leptophytum coulmanicum 18 m
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The largest seaweeds can be found around
Subantarctic islands –thalli of Macrocystis pyrifera can measure up to 40 m and have a
significant impact on the whole littoral zone,
because they act as a natural breakwater
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Benthos of deep waters• viewed as a region of low biodiversity.• however, three coordinated expeditions in the deep Weddell Sea (748-6348m) have shown this not to be true • among the 13000 specimens were: 200 polychaete species (81 new), 160 species of gastropods and bivalves, 76 species of sponge (17 new), 674 isopods (585 new), 57 nematode species, and 158 species of foraminifera
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• slow, seasonal growth and delayed maturation• low water temperatures certainly slow metabolic rates to the extent that growth rates are slow enough to enable organisms to live longer
Gigantism
Glyptonotus antarcticus
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Ecology of polar oceansLinda Nedbalová