Download Peruvian anchovy landings and El Niño events

Oceanic ecosystems
1. Tectonics and ocean basin evolution
2. Late Cenozoic climates
(and biogeographic consequences)
3. Ecosystem structure and function
4. Short-term spatio-temporal variations
5. Reef, forest, and smoker communities
Oceanic environments
area:
ecosystem:
basin
trench
ridge
shelf
slope
continental
plate
open ocean
60%
coastal
10%
pelagic
neritic
terrestrial
30%
Tectonics and ocean basin
formation since 200 Ma BP
3
4
1
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2
4
Major Cenozoic changes
Tectonic (see previous slide)
1.
2.
3.
4.
Opening of Atlantic Ocean
Closing of Tethys Sea
Closing of Panama gap
Opening of Antarctic circulation
Climatic
a. Climatic cooling in polar latitudes
b. Glacio-eustatic changes in relative
sea level
Divisions of the ocean ecosystem
Nybakken, J.W. (2001) “Marine Biology”. Addison-Wesley-Longman
Definitions of terms
littoral:
neritic:
pelagic:
benthic:
abyssal:
hadal:
Spatio-temporal variations in
sea-surface temperature
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Phytoplankton: marine
diatoms and dinoflagellates
Light: required for photosynthesis. Phytoplankton are sensitive
to light amount and quality. By modifying their buoyancy (and
hence their depth in the water column), they can change their
ambient light environment.
CO2: required for photosynthesis.
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Nutrients: silicate (required to build diatom cell walls), and
nitrate, phosphate and iron (required for cell metabolism) may be
limiting resources for phytoplankton growth in many parts of the
ocean.
Temperature and
phytoplankton growth
Species
Thermal
environment (°C)
Skeletonema tropicum 18 to 25
Skeletonema costatum 12 to15
Thalassiosira antarctica -2 to 4
Phaeocystis antarctica -2 to 4
Optimal
temperature (°C)
10 to 20
10 to 20
10 to 20
10 to 20
year-round growth in tropics; seasonal
production in temperate and polar waters
Spatio-temporal variations in
primary production
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Temperature-depth profiles
0
-5
0
5
0
5
10
15
20
25
0
5
10
15
20
seasonal
thermocline
500
permanent
thermocline
1000
permanent
thermocline
1500
2000
2500
3000
Arctic
Temperate
Tropical
25°C
Plankton
production
in polar,
temperate
and tropical
oceans
phytoplankton
zooplankton
Nybakken, J.W. (2001) “Marine Biology”. Addison-Wesley-Longman
Seasonal variations in thermal
structure and nutrient concentration in
temperate oceans
Temperature
Temperature
thermocline
Winter
Summer
Terrestrial vs. oceanic food chains
Nybakken, J.W. (2001) “Marine Biology”. Addison-Wesley-Longman
A simple marine food web:
sub-Antarctic waters
diatoms,
dinoflagellates
A marine carbon budget:
Herbivore pathway
an example from the English Channel
Phytoplankton
100
61
Bacteria
22
17
Zooplankton
19
Protozoa
6
5
Microbial loop
Flagellates
6
World ocean currents
Currents and biotic migrations
Image: FAO
Seasonal variations in circulation
L
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H
Maps: Thompson et al., 1989. “Vancouver Island coastal current…
Wind directions and water
advection in coastal waters
Images: http://www.crd.bc.ca/
Upwelling zones
Fraser
River
plume
Primary
productivity
in zones of
coastal
upwelling
image: terra.nasa.gov
Upwelling (in green)
Tidal stream flowing over
continental shelf margin
(e.g. Bering Sea)
Coriolis-induced divergence
of surface equatorial
currents
Coriolis-induced offshore
flow of coastal current
(e.g. California Current)
Ocean Fronts and Eddies
FRONT: the interface between two water masses with
differing physical characteristics (temperature and salinity)
with resulting variations in density. Some fronts which have
weak boundaries at the surface have strong “walls” below the
surface. The boundary zones are sites of increased biological
production.
EDDY: a rotating mass of water with a ± uniform physical
characteristics. They can be thought of as circular fronts.
Their boundaries are associated with increased productivity.
Fronts and eddies: Gulf Stream Labrador Current boundary zone
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seis.natsci.csulb.edu/rbehl/gulfstream.htm
Oceanic front productivity
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Iron fertilization experiment:
polar Southern Ocean (I)
days
Iron fertilization experiment:
polar Southern Ocean (II)
days
Sahara dust storm over
adjacent Atlantic Ocean
image: terra.nasa.gov
El Niño - Southern Oscillation (ENSO)
events
El Niño (1982-83)
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High SSTs and reduced upwelling of nutrients in
eastern tropical Pacific Ocean
Sea level and thermocline depth
variations in the central Pacific
during the El Niño event of 1997-8
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Variations in primary production in
the vicinity of the Galapagos Islands
during an El Niño - La Niña cycle
El Niño
La Niña
Consequences of reduced
upwelling ( e.g. 1982-83)
N depletion in surface waters led to a drastic
reduction in phytoplankton abundance
Pelagic fish populations were heavily impacted
e.g. Peruvian anchoveta (Engraulis ringrens) live for only three years
and feed on diatoms and are therefore highly susceptible to shortterm environmental oscillations.
South American sardine (Sardinops sagax) feed on copepods and
diatoms and can live for up to 25 years. They are less sensitive to El
Niño events than anchoveta.
Peruvian anchovy landings
and El Niño events
14000
12000
Landings (tons)
10000
8000
6000
4000
major
minor
2000
0
1970
1975
1980
1985
1990
1995
2000
Ecological consequences of
El Niño events
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Decadal-scale fluctuations:
the Pacific Decadal Oscillation
SST anomalies
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“warm phase”
“cool phase”
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14000
Russian sockeye catch
10000
tonnes
PDO regime
shifts and
ecological
consequences
12000
8000
6000
4000
2000
0
1940
1950
1960
1970
1980
1990
Deep-sea communities
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Feed on organic particles in ooze that accumulates on
ocean floor at rates of <0.01 mm yr-1.
Sediment includes aeolian deposits and biogenic detritus.
Deep-sea communities
• Largely (~80%) sediment deposit feeders;
• Predators include crustaceans and primitive
fish;
• Spatially and temporally variable, despite
apparent locally uniform water masses;
• Diverse (= numerous sediment microhabitats
and heavy predation?) but poorly known;
?10 M species yet to be described from
deep-sea sediments.
Major hydrothermal vents
Nybakken, J.W. (2001) “Marine Biology”. Addison-Wesley-Longman
Hydrothermal vent
communities
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“black smoker”
releasing sooty, mineralrich, hot ( 350°C) water,
H2S and CO2
Food web (generalized)
Nybakken, J.W. (2001) “Marine Biology”.
Addison-Wesley-Longman
Kelp “forests”
A subtidal forest in the
Aleutian Islands, Alaska.
Cymathera triplicata
(foreground); Alaria fistulosa
(rear). Kelp forests in the
northeastern Pacific commonly
have complex threedimensional structure, with
many coexisting species. As in
terrestrial forests, shading is
a major mechanism of
competition.
Image and text:
life.bio.sunysb.edu/marinebio/kelpforest.html
Distribution of kelp species
with depth (California)
Layers
1.
2.
3.
4.
red algae and coralline algae
prostate-canopy kelp
erect understorey kelp
floating canopy
Nybakken, J.W. (2001) “Marine Biology”.
Addison-Wesley-Longman
Kelp biogeography
Miocene?
26 genera
5 genera
~83 spp.
11-18 spp.
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Pleistocene?
4 genera
10-12 spp.
Originated in north Pacific in early Cenozoic; rapid radiation
of new forms; dispersed in mid to late Cenozoic? to N.
Atlantic, and in Pleistocene? to southern oceans.
Kelp forest food webs
Orcas
(1990s)
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research.amnh.org/biodiversity/crisis/foodweb.html
Effects of sea otters on species
diversity of kelps in southern Alaska
no otters
present
otters
<2 yr
otters
>15 yr
Torch Bay
Deer Harbor
Surge Bay
Diversity Index (H')
0.5
Sea otter harvesting
sea urchin
0.4
0.3
0.2
0.1
0
Succession in an
Alaskan kelp
forest
Note high diversity
in the early intermediate
successional
phases; “climax”
consists of a selfreplacing Laminaria
bed
(shade tolerant)
Image: David Duggins