The World's Oceans drive the biology of Planet Earth... How? (climate, O₂ availability, nutrient cycling, etc.)

An understanding of geological processes is fundamental to marine biology because....

Geology ultimately determines most physical and chemical characteristics in marine environments

Three topics of particular interest when defining the physical and chemical environment: Topography, Chemistry, History

Why is topography important?

Water, as a fluid, fills the shape of its container

Local topography (shape of ocean floor and coastlines) influences:

Flow (currents, tides, waves)

Temperature (shallow vs. deep)

Chemistry (salinity and other important chemical elements

Why is chemistry important?

Consider the main elements used by organisms

Calcium, Hydrogen, Nitrogen, Oxygen, Phosphorus, Sulfur, and Iron

Availability determined by geology, physics, chemistry, and biology

These chemicals circulate between organic and inorganic reservoirs

Biological markers

Elements and isotopes are an important source of information

Present day studies (otoliths)

Historical studies (isotope ratios vs. temperature)

Why is history important?

Paleo-biology and paleo-ecology (traces the origins and evolution of life)

Historical events profoundly influence life on the planet (and in the sea)

Ice ages

Catastrophes (seismic events, asteroids)

Also... past events determine availability of fossil fuels...

This often determines what and where studies take place

Understanding geologic processes begins with plate tectonics and continental drift

Imagine a simmering cauldron of soup: Silica croutons, ferrous crust, and magma broth

Sea floor spreading, subduction, volcanism, and other seismic events (side-side vs. up-down faults)

Historically, the oceans and continents looked quite different... and that influenced both marine and terrestrial lifeforms.

Some definitions:

Continental margins

shelf (sediments from land erosion, turbidity currents send land sediments to the depths)

slope

trenches

island arcs, archipelagos

shelf-slope-rise vs. shelf-slope-islands/trench  

Ocean basin floors

soft sediments of:

Plankton skeletons

Clay and other minerals

Volcanic products

Precipitates (manganese, iron)

Oceanic ridge systems

Centers of divergence: sea-floor spreading

Evidence:

magnetic anomalies

increasing age of volcanic rock with distance from ridge

few old sedimentary deposits (all subducted)

"jigsaw" fit of the continents.

Watching it happen!

Divergence in some areas leads to subduction in others.

Defining oceans and marginal seas

two views: equatorial vs polar

The Oceans

Pacific

Wide and old

"ring of fire"

Little river drainage, few seas, determines climate

Atlantic

Narrow and young

Many seas (Gulf of Mexico, Baltic, Mediterranean, North)

Influenced by rivers (Mississippi, Nile, Amazon, Congo)

Indian

Smaller

Seasonally moderate upwelling/productivity

Arctic

Small, seasonally high productivity

Antarctic

No land boundaries, high year-round productivity

"Marginal" seas

Restricted flow creates unique local oceanographic features

high salinity

local currents

unique flora and fauna, etc.

 

Classifying marine habitats

What you find depends upon where you look

Patterns of temperature, light, nutrition, disturbance, desiccation, etc vary spatially

(figure 1-45 from text)

Some habitats:

Neritic zone (over the continental shelf)

Intertidal

between high and low tide

Subtidal

Pelagic zone (Oceanic)

Epipelagic (upper 150 - 200 m or so... linked to the photic zone)

Mesopelagic (150/200 - 1000 m)

Bathypelagic (1,000 - 4,000 m)

Abyssopelagic (4,000 - 6,000 m)

Hadal or "Hadopelagic" (in the trenches)

"Benthic" zones are on the bottom