Phytoplankton in polar regions
BIO 4400 2009 Bente Edvardsen
Arctic and Antarctic - similarities
• Cold • Low light during long polar winter, continuous
light during summer• Seasonal dynamics dominated by annual
formation and melting of ice• Cold high-density bottom water formation
during freezing of sea water, brine expultionand reduction of ice salinity.
differencesArctic• Latitude: 70-80°N• Enclosed by land• Ocean size: 15 mill km2
• Ice cover: 14 mill km2 winter• 7 mill km2 summer• Pack ice last longer and is
thicker (av. 3.5 m)• Influenced by many large river
systems• Av. depth 1800 m and large
part over shallow shelf• Nutrient controlled
phytoplankton productionduring the summer
Southern Ocean• Latitude: 50 - 60 or 70°S• Circumpolar open system• Ocean size: 36 mill km2
• Ice cover: 20 mill km2 winter• 4 mill km2 summer• Most pack ice is one year
and thinner (av. 1.5 m)• Little terrestrial influence• Narrow shelf, pack ice over
deep water (4000-6500 m)• High nutrient, low chlorophyll
areas that may be limited by iron
ArcticOcean
SouthernOcean
The maximum and minimum extent ofsea ice cover.
Irradiance per 24 h
theoretical values for irradiance at different latitudes
from Sakshaug et al. 1992
latitude
NorwegianNorwegian, , GreenlandGreenland and and BarentsBarents SeasSeas
Barents Sea
Water circulation in the Barents Sea
Polar front
Barent Sea: Distribution of temperature at 100 m depth during August-September
Variation in ice cover distribution
Barents sea: Median values for end of April in twoperiods
(extreme)
from Blindheim 2004
Pack ice= ice formed at sea
Melosira arctica in the Arcticocean
Ice assemblages
from Sakshaug et al. 1992 modified from Horner
Ice microalgalassemblages
Microalgal communities in the ice
from Syvertsen 1991
(skrugard-sammfunnet)
Ice algae
fra Syvertsen 1991
the comb effectfor trapping and colonisation of icealgae
Algae in the icewill avoid verticalmixing and somegrazing
Algal communities near and on the ice in the Arctic
from Syvertsen 1991
= Fragilariopsis oceanica =Attheya septentrionalis
Plankton- and icealgae in the Arctic
from Syvertsen 1991
plankton sub-ice Nitzschia frigida
Melosira arctica
Ice algaecommunities in the Barents Sea
from Syvertsen 1991
the ice edge effect –productive zone 20-50 km along the ice edge
Microalgal developmentin the Barents Sea
from Sakshaug et al. 1992
SPRINGsnow
multi year ice one year ice
Microalgal development in the Barents Sea
from Sakshaug et al. 1992
SUMMERsnow
Algal succession in the BarentsSea
from Sakshaug et al. 1992
the ice-edge effect
prebloom
Zooplankton spawning
overwintering zooplankton migrating up
ice edgebloom
nutrientdepleated new generation of
zooplankton developing
Capelin feedingalgae sinking
TIME
marginal ice zone / ice edgeAntarctic: 100-200 km
Arctic: 20-50 km
Timing of vernal blooming- Arctic
Ice-edge bloom• Stratification depends on salinity (as in
fjords)• may start in April, 6-8 weeks before the
vernal bloom in the Norwegian Sea
Stability and production in theBarents Sea
North of polar front• strong stratification (freshwater stabilization; 20-30 m)
throughout summer• regenerated production after the spring maximumSouth of polar front• weaker stratification (temperature stabilisation)
• wind driven vertical mixing throughout summer keep up nutrient supplies
South of the polar front; turbulence and ”blooming”(model), Barents Sea
phytoplankton Ncalm
with wind
Algal groups in the Barents Sea
Diatoms -> 100 000 cells L-1
Prymnesiophyceans; • Phaeocystis pouchetii
-> million cells litre-1
other flagellates
BiogeographySpecies with preference for cold water have
competing advantages in the Arctic, but are also present in temperate waters
1. Nitzschia frigida (also in Oslofjorden)2. Melosira arctica (also in the Baltic Sea)3. Thalassiosira gravida og Thalassiosira
hyalina (also in Skagerrak)
Subsurface algae and bacteria
Summary – Barents Sea
• Hydrography; atlantic water meets polar water (polar front)
• Melting cause a brackish upper water layer that stabilise the water mass
• Spring bloom associated to the ice edge• Ice algae in and under the ice• South of the polar front: recurrent periods
with wind cause vertical mixing also in thesummer and bring up nutrients.
Southern Ocean
Hydrography
Antarctic bottom water
Deep ocean circulation
F/F G.O. Sars on cruise to the Southern Ocean2008
Leg 2: 25 scientists from 8 countries + 12 crew
18 February- 24 March 2008
Stations for CTD, nutrients, chl a and phytoplankton, leg 2.
Aims - phytoplankton
Phytoplankton in the food web• Abundance and distribution• Species and size composition • Co variation with nutrients temp. salinity stability • Food preferences in krill
Biodiversity• Biodiversity of protists, with emphasis on nano and pico-plankton• Distribution, abundance and ecology of certain taxa
Sampling for phytoplankton
• Nutrients (N, P, Si)• Chlorophyll a• Chlorophyll a size
fractions• Phytoplankton
quantitative sample• Phytoplankton net haul• Pico-nanoplankton• DNA• Cultures
-36 stations, up to 8 depths
Phytoplankton net haul, vertically 0-100m
algal culturessampling
DNA-isolation
Methods- biodiversity
electron microscopy
PCR
DNA sequencingphylogenetic
analyses
cloning454-sequencing
Fluo
rese
nce
/ µug
/l
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
51
53
55
56
58
59
61
62
63
65
66
68
69
71
72
73
74
Latitude °S
Pre
ssur
e / d
bar
AKES 2008
Contours at [0:0.05:.8] µug/l46 48 50 52 54 56 58 60 62 64 66
300
250
200
150
100
50
0
Fluorescence along 15oE
0
50
100
150
200
250
0 0,1 0,2 0,3 0,4 0,5
Chl a (mg/m3)
Depth
Fluo
resc
ens
Dyp
(m)
0
50
100
150
200
250
0 0,1 0,2 0,3 0,4
Chl a (mg/m3)
Depth
st. 62 st. 73
Results:
Thet
a / °
C, p
ref =
0 d
bar
-2
0
2
4
6
8
10
12
51
53
55
56
58
59
61
62
63
65
66
68
69
71
72
73
74
Latitude °S
Pre
ssur
e / d
bar
AKES 2008
Contours at [-2:0.5:6 7:1:12 ] °C46 48 50 52 54 56 58 60 62 64 66
1500
1000
500
0
Sal
inity
/
33.6
33.8
34
34.2
34.4
34.6
34.8
35
35.2
51
53
55
56
58
59
61
62
63
65
66
68
69
71
72
73
74
Pre
ssur
e / d
bar
AKES 2008
Contours at [33.5:0.1:34.8 35 35.2 ] 46 48 50 52 54 56 58 60 62 64 66
1500
1000
500
0
Dep
th(m
)D
epth
(m)
temperature
salinity
Hydrography
15oEHigh levels of N, P and Si south of51oS (>15,1,30 mg L-1)
Quantitative phytoplankton counts
0
200
400
600
800
1000
1200
1400
67- 30m 69 - 5m 72 - 50m 73 - 30m 78 - 30m 78 - 5m 78 - 75m 83 30m
Station and depth
Cel
ls/m
L
Diatoms
Cryptophytes
Ciliates
Dinoflagellates
nanoflagellates andmonads >3 my
Small pico- and nanoflagellates and monads. and small diatoms dominatedin the open ocean during this summer cruise.
Pico-nanoflagellates(SEM)
haptophytes, cryptophytes, prasinophytes, choanoflagellates
etc.
Rhizosolenia antennata f. antennata Asteromphalus parvulus
Fragilariopsis kerguelensis
Corethron pennatum
Microalgae in net hauldiatoms
Chaetoceros dichaeta
Chaetoceroscriophilus
Chaetocerosflexuosus
Microalgae in net haul - diatoms
Nanoplankton
Phaeocystis antarctica
(haptophyte)
Dactyliosolen cf. tenuijunctus
(diatom)
LM SEM
Pico-nanoplankton (LM og SEM)
Fragilariopsis nana
Fragilariopsis pseudonana
Fragilariopsis spp. (st. 63, TEM)
F. nana
F. kerguelensis
F. separanda
F. rhomboides F. ritscheri
Some conclusions on from theG.O. Sars cruise in 2008
• Chlorophyll levels were low (<1 mgL-1) with a maximum at 20-100 m depth
• High levels of N, P, Si in open ocean during summer
• Higher algal abundance in the polar front region and near the continent, despite lower stabilityhere, probably due to higher Fe-levels
• Nano- and picoflagellates and small diatomsdominated in numbers
• Diatoms dominated in the net hauls