Oceanic ecosystems

1
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

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Oceanic environments
shelf
slope
trench
ridge
continental plate
basin
oceanic plate
open ocean coastal
terrestrial 60 10
30
area
ecosystem pelagic neritic

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Tectonics and ocean basin formation since 200 Ma
BP
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3
2
4
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Major Cenozoic changes

• Tectonic (see previous slide)1. Opening of
  Atlantic Ocean2. Closing of Tethys Sea3.
  Closing of Panama gap4. Opening of Antarctic
  circulation

• Climatica. Climatic cooling in polar
  latitudesb. Glacio-eustatic changes in relative
  sea level

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Divisions of the ocean ecosystem
Nybakken, J.W. (2001) Marine Biology.
Addison-Wesley-Longman
6
Definitions of terms
littoral neritic pelagic benthic abyssal
hadal
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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. 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.
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Temperature and phytoplankton growth
Species Thermal
Optimal
environment (C) temperature (C)Skeletonema
tropicum 18 to 25 10 to
20Skeletonema costatum 12 to15
10 to 20 Thalassiosira antarctica -2 to 4
10 to 20 Phaeocystis antarctica
-2 to 4 10 to 20
year-round growth in tropics seasonal production
in temperate and polar waters
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Spatio-temporal variations in primary production
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Temperature-depth profiles
-5 0 5 0 5 10 15 20
25 0 5 10 15 20 25C
0 500 1000 1500 2000 2500 3000
seasonal thermocline
permanentthermocline
permanentthermocline
Depth (m)
Arctic Temperate Tropical
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Plankton production in polar, temperate and
tropical oceans
phytoplankton zooplankton
Nybakken, J.W. (2001) Marine Biology.
Addison-Wesley-Longman
13
Seasonal variations in thermal structure and
nutrient concentration in temperate oceans
Temperature
Temperature
Depth
thermocline
Winter Summer
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Terrestrial vs. oceanic food chains
Nybakken, J.W. (2001) Marine Biology.
Addison-Wesley-Longman
15
A simple marine food web sub-Antarctic waters
diatoms,dinoflagellates
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A marine carbon budget an example from the
English Channel
Phytoplankton 100
61
Bacteria
Decomposer pathway
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Herbivore pathway
Zooplankton
Protozoa
Flagellates
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6
5
Microbial loop
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World ocean currents
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Currents and biotic migrations
Image FAO
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Seasonal variations in circulation
Maps Thompson et al., 1989. Vancouver Island
coastal current
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Wind directions and water advection in coastal
waters
Images http//www.crd.bc.ca/
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Upwelling zones
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Primary productivity in zones of coastal upwelling
Fraser River plume
diatom bloom
image terra.nasa.gov
23
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)
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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.
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Fronts and eddies Gulf Stream - Labrador Current
boundary zone
seis.natsci.csulb.edu/rbehl/gulfstream.htm
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Oceanic front productivity
frontal zone
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Iron fertilization experimentpolar Southern
Ocean (I)
days
from Boyd et al., (2000), Nature 407, 695-702.
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Iron fertilization experimentpolar Southern
Ocean (II)
days
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Sahara dust storm over adjacent Atlantic Ocean
image terra.nasa.gov
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El Niño - Southern Oscillation (ENSO) events
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El Niño (1982-83)
High SSTs and reduced upwelling of nutrients in
eastern tropical Pacific Ocean
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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
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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 short-term
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.
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Peruvian anchovy landings and El Niño events
major minor
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Ecological consequences of El Niño events
Marine iguanas
Sea lions and fur seals
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Decadal-scale fluctuations the Pacific Decadal
Oscillation
SST anomalies
warm phase cool
phase
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Russian sockeye catch
PDO regime shifts and ecological consequences
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Deep-sea communities
Feed on organic particles in ooze that
accumulates on ocean floor at rates of lt0.01 mm
yr-1. Sediment includes aeolian deposits and
biogenic detritus.
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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.

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Major hydrothermal vents
Nybakken, J.W. (2001) Marine Biology.
Addison-Wesley-Longman
42
Hydrothermal vent communities
black smoker releasing sooty, mineral-rich,
hot ( 350C) water,H2S and CO2
Food web (generalized)
Nybakken, J.W. (2001) Marine Biology. Addison-W
esley-Longman
43
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 three-
  dimensional structure, with many coexisting
  species. As in terrestrial forests, shading is a
  major mechanism of competition.

Image and textlife.bio.sunysb.edu/marinebio/kelp
forest.html
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Distribution of kelp species with depth
(California)

• Layers
• red algae and coralline algae
• prostate-canopy kelp
• erect understorey kelp
• floating canopy

Ploca
Pelagophy
Nybakken, J.W. (2001) Marine Biology. Addison-W
esley-Longman
45
Kelp biogeography
Miocene?
26 genera83 spp.
5 genera11-18 spp.
Pliocene?
Pleistocene?
4 genera10-12 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.
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Kelp forest food webs
Orcas(1990s)
research.amnh.org/biodiversity/crisis/foodweb.html
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Effects of sea otters on species diversity of
kelps in southern Alaska
Sea otter harvesting sea urchin
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Succession in an Alaskan kelp forest

• Note high diversity in the early -
  intermediate successional phases climax
  consists of a self-replacing Laminaria bed(shade
  tolerant)

Time
Image David Duggins