Oceanic ecosystems

1. Tectonics and ocean basin evolution2. 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

ridge

tren

ch

slope

area: open ocean coastal terrestrial 60% 10% 30%

ecosystem: pelagic neritic

shelf

continentalplateoceanic plate

basin

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Tectonics and ocean basin formation since 200 Ma BP

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44

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

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

dinoflagellatesLight: 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 20year-round growth in tropics;

seasonal production in temperate and polar waters

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 25°C 0

500

1000

1500

2000

2500

3000Arctic Temperate Tropical

permanentthermoclinepermanent

thermocline

seasonal thermocline

De

pth

(m

)

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

De

pth

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: an example from the English

Channel

Phytoplankton100

Zooplankton

22

6

Herb

ivore

path

way

Decomposer pathway

Bacteria

61

Protozoa

17

Flagellates

19

65

Microbial loop

World ocean currents

Currents and biotic migrations

Image: FAO

Seasonal variations in circulation

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Maps: Thompson et al., 1989. “Vancouver Island coastal current…”

L

H

Wind directions and water advection in coastal waters

Images: http://www.crd.bc.ca/

Upwelling zones

Primary productivity in zones of

coastal upwelling

image: terra.nasa.gov

Fraser

River plum

ediatom bloom

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

from

: B

oyd e

t al., (2

00

0),

N

atu

re 4

07

, 6

95

-70

2.

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

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.

Peruvian anchovy landings and El Niño events

0

2000

4000

6000

8000

10000

12000

14000

1970 1975 1980 1985 1990 1995 2000

Landings (tons)

majorminor

Ecological consequences of El Niño events

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Sea lio

ns

an

d f

ur

seals

Mar i

ne igu

an

as

Decadal-scale fluctuations: the Pacific Decadal

Oscillation

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“warm phase” “cool phase”

SST anomalies

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PDO regime

shifts and ecological consequen

ces0

2000

4000

6000

8000

10000

12000

14000

1940 1950 1960 1970 1980 1990

tonnes

Russian sockeye catch

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

Nybakken, J.W. (2001) “Marine Biology”.Addison-Wesley-Longman

Food web (generalized)

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“black smoker”releasing sooty, mineral-rich, hot ( 350°C) water,

H2S and CO2

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 text:life.bio.sunysb.edu/marinebio/kelpforest.html

Distribution of kelp species with depth

(California)

Ploc

aPe

lago

phy

Layers1. red algae and coralline algae2. prostate-canopy kelp3. erect understorey kelp4. floating canopy

Nybakken, J.W. (2001) “Marine Biology”.Addison-Wesley-Longman

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26 genera~83 spp.

4 genera10-12 spp.

5 genera11-18 spp.

Kelp biogeographyMiocene?

Pliocene?

Pleistocene?

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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research.amnh.org/biodiversity/crisis/foodweb.html

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Kelp forest food websOrcas

(1990s)

Effects of sea otters on species diversity of kelps in southern

Alaska

0

0.1

0.2

0.3

0.4

0.5

Torch Bay Deer Harbor Surge Bay

Diversity Index (H')

no otters otters otters present <2 yr >15 yr

Sea otter harvestingsea urchin

Image: David Duggins

Tim

e

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

Succession in an Alaskan kelp forest