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Oceanography 101

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Chapter 13 - The Marine Environment


What is a "Marine Community?"

-- An area where a group of marine organisms live and interact with each other.

See Chapter 13 Handout (one-page .pdf file with vocabulary summary from class presentation)

Marine communities include:

Tropic Levels Organisms
Tertiary consumers carnivores (larger animals, i.e. tuna, sharks, birds, sea mammals, etc)
Secondary consumers carnivores and detritus feeders (ie, small fish, crustaceans)
Primary consumers herbivores (zooplankton)
Primary producers photosynthetic bacterial - plankton - plants (focus of chapter 12)

Definitions

* Planktonic: "Floaters/drifters" (zooplankton are animals, phytoplankton are plants)

* Nektonic: "Swimmers"

* Pelagic: means “relating to the open sea, chiefly shallow layers” Planktonic and nectonic organisms live in "open water" (more in chapter 14)

* Benthic: means “relating to, or occurring at the bottom of a body of water (oceans, lakes), relates to "bottom dwellers" (more in chapter 15)

"Benthic" applies to:
-- shoreline and nearshore environments (littoral and estuarine)
-- limnetic (pertaining to lakes)
-- estuarine (pertaining to transition from river to ocean settings
-- seabed in shallow ocean (neritic) and deep water settings

* Terrestrial refers to “land” environments (desert, mountain, rivers, etc) - some marine predators live in terrestrial environments.

* Autotrophic: Produce their own food (primary producers)

* Heterotrophic: Eat other things (living or dead) (consumers - primary, secondary, and tertiary).

Feeding strategies of heterotrophic marine organisms:

* Filter feeding: ex: shellfish

* Deposit feeding: Eat deposits of dead or decaying matter

* Carnivorous feeding: Capture and eat it!

1. Natural factors influencing marine life:


Physical factors
:
a) Temperature/Salinity (very significant)
b) Tides, Waves, Currents (“energy" in the environment)
c) Water Transparency
d) Nutrients
e) pH
f) Pressure
g) Dissolved Gases
h) Environmental Stability

Biological factors
:
i) Competition for mates, food, and space
j) Predators

a) Temperature: governs the rate chemical and metabolic rates especially in cold-blooded organisms.
Many organisms are sensitive to changes in temperature and this results in species zonation.
Example: Different species of sharks.

For poikilothermic
(cold blooded) organisms: every 10o C rise in temperature doubles their metabolism.
For homeothermic (warm blooded) organisms: metabolism increases with decreasing temperature to stay warm.

b) Salinity of surrounding water
*Variable near landmasses ie: tidepools, river outlets and with depth.
*Salinity of the ocean is close to the salinity of most marine creatures.
*Different organisms have different tolerances to changes ie: Bull Sharks,
*example: oysters can't tolerate normal seawater because of predation and food supply

c) Water transparency: Water has a high transparency. So many organisms use different strategies to survive.

* Countershading or camouflaging help organisms hide from predators.
* Migration into darker areas during the day and lighter areas at dawn and dusk is another.

Another consideration is clarity for photosynthesesis.
* Photic zone: The upper part of the ocean where sunlight penetrates (down to ~3,300 feet in very clear water!).
* Euphotic Zone: upper ½ of photic zone where most primary production occurs.

d) Nutrients: are not "food," more like vitamins and minerals essential to life functions

* Aids in the production of food (primary production).
* Photosynthesis formula shows only basic steps -- There are many more intermediate processes requiring nutrients to produce other complex organic compounds (proteins, carbohydrates, fats, etc).

Sources: Upwelling and continents
Primary = nitrates and phosphates
Secondary = minerals: calcium, iron, zinc, sodium, and many others.

e) pH
Seawater averages about 8 on a scale from 1 – 14 (1 is acidic, 14 is basic and 7 is neutral).
Seawater is a buffered system meaning it is controlled in a range.
If it gets too acidic it dissolves CaCO3, if its too basic it precipitates CaCO3.
Becomes slightly more acidic near the CCD (carbonate compensation depth).

f) Pressure
pressure is the same inside an organism as outside
organisms at great depths must be able to withstand great internal pressures

g) Dissolved gases: (discussed in previous sections)
There must be sufficient CO2 for plants and O2 for animals or they must: move, adapt or die.
Most ocean pollutants remove the waters ability to hold CO2 or O2.

h) Environmental stability

The open ocean is generally a very stable environment compared to shallow and nearshore environments where the factors listed above may vary wildly with weather changes and other natural and artificial causes, both physical or biological in nature.

Biological factors:

i) Competition for mates, food, and space
-- competition may be between members of a species or between species

j) Predators
-- too many predators can wipe out a community; not enough predators cause population explosions, resource exhaustion, and collapse.

2) Divisions in the Marine Environment


a) The Pelagic (open sea) environment is divided into the Neritic (neritos-of the coast) and Oceanic Provinces.

Neritic (nearshore): Extends from shore with water less than 200 meters
* Littoral (intertidal) zone: Interval between high and low tides
* Sub-littoral: Below the littoral zone to a depth of 200 meters.

Oceanic Provinces
* Epipelagic: Water less than 200 meters
* Mesopelagic: Water between 200 and 1000meters
* Bathypelagic: Water between 1000 and 4000meters
* Abyssopelagic: Water deeper than 4000meters

b) Sunlight penetration has its own divisions:
* Photic zone: The upper part of the ocean where sunlight penetrates
* Euphotic Zone: upper ½ of photic zone (usually to about 100 meters)
* Disphotic Zone: lower ½ of photic zone
* Aphotic Zone: No light penetrates

Evolution - Adaptation or Extinction ("Adapt, move or die!")


Evolution
is the process by which different kinds of living organisms have developed and diversified from earlier forms during the history of the earth.

Darwinism - the theory of the evolution of species by natural selection advanced by Charles Darwin.

Natural selection: "organisms better adapted to their environment tend to survive and produce more offspring."

All living things
(plants, animals, etc.) use a variety of adaptations to help them survive.

Extinction - the state or process of a species, family, or larger group being or becoming extinct.

Changes in in physical and biological factors create opportunity and misfortune/bad luck, operating
under natural selection (Adapt, move, or die!)

Local die-offs happen frequently; when all viable reproducing members of a "species" or "biological organization" die off it is extinction.

Global environmental change and irresponsible exploitation are current driving forces of extinction.

A mass extinction is a event when many different life forms (including plant and animal species) become extinct (over a "relatively short" period of geologic time).

The last mass extinction occurred approximately 65.5 million years ago (the Cretaceous/Tertiary Boundary). What happened?

In the last 500 million years, there have been at least five major mass extinctions when more than 50 percent of animal species disappeared.

1) Zoning and Extinction in Marine Communities
Both physical and biological factors result in zoning and extinction of organisms in a specific environment.

Each group of organisms are affected by physical and biological factors (listed above). These conditions exist within geographically definable areas ranging from large (entire oceans) to microenvironments (such as a rock outcrop on a beach).

2) Carrying Capacity in Marine Communities – stable number of individuals in a community

Example:
Raise the temp 10 degrees C for a group of poikilothermic organisms with a
limiting factor of food and hold other factors constant-what is the most likely result.

Same problem but with homeothermic organisms?

Changes in in physical and biological factors create opportunity and misfortune/bad luck, operating under natural selection (Adapt, move, or die!)

Local die-offs happen frequently; when all viable reproducing members of a "species" or "biological organization" die off it is extinction.

Global environmental change and irresponsible exploitation are current driving forces of extinction.

A mass extinction is a event when many different life forms (including plant and animal species) become extinct (over a "relatively short" period of geologic time).

The last mass extinction occurred approximately 65.5 million years ago (the Cretaceous/Tertiary Boundary). What happened?

In the last 500 million years, there have been at least five major mass extinctions when more than 50 percent of animal species disappeared.

3) Distribution of Organisms - how are they distributed throughout an environmental setting?

i. Random: rare in marine environment
ii. Uniform: more common than random – eels in holes or penguins on nests
iii. Clustered: most common schooling fish, clusters of barnacles and mussels on rocks.
iv. Zoned: species or community of species living together in a limited geographic range defined by physical and biological factors.
Most organisms in marine environment are ZONED or CLUSTERED.

4) Symbiotic Relationships

* Mutualism: benefits both host and symbiant.
Example: Anemone and the anemone fish; fish cleans and feeds anemone,
stays with anemone for protection – fish can’t be stung (clown fish)

* Parasitism: Harms host, benefits symbiant.
Example: Parasites in tuna.

* Commensalisms: no effect on host, benefits symbiant.
Example: Shark and pilot fish (pilot fish eats leftovers).

http://geologycafe.com/oceans/course_notes13.html
9/3/2014