Background on Life in the Oceans

Living things all    

        contain matter in an organized state,

        can capture, store, and transmit energy

        can reproduce and change through time, and

        can adapt to their environment.

Their common needs involve the need to capture and store energy,

        maintain their metabolisms, and

        transmit information between generations.

The millions of species on earth have developed different strategies for meeting these needs.

Organisms in the sea range from microscopic single celled organisms to large multicellular organisms.

Three types,        Plankton - free floating

                           Nekton - swimming

                           Seston - attached

1.  Plankton-the free floating micro-organisms of the ocean’s surface waters
 Plankton are very small, yet have something in common with very large objects-planets.  Plankton and Planet both come from the same greek root word meaning WANDERER.  In the case of plankton, they are wanderers because they do not actively swim, but instead float in the water, and so must go where the water takes them.

2.  The marine plankton fall into three main groups:  the phytoplankton (plants), the zooplankton (animals), and  a group consisting of bacteria & viruses, often called the nanoplankton and picoplankton.  Today we will look primarily at the phytoplankton and the zooplankton.
 

3.  Phytoplankton  are often referred to as the “grasses of the sea” because they are the plant community that form the base of the food chain.  They are autotrophic, meaning they make their own food through photosynthesis.
 a.  Phytoplankton live only where sunlight can reach them, the surface of the ocean
 b.  Phytoplankton (along with the atmosphere) supply oxygen to the surface water, and thus provide oxygen to the deep water that is moving by thermohaline circulation.
 c.  Phytoplankton form the base of the food chain for most of the ocean communities
 d.  Phytoplankton provide at least 40% of the food made by photosynthesis on Earth each year
 

Two of the many types of Phytoplankton are

Diatoms - dominant in areas of high productivity with shells of silica.  They store energy as oils in their bodies, are free floating, and often form long chains.

Dinoflagellates - don't form shells, but have whip-like appendages (flagellae) that allow them to move about.  They have a solitary lifestyle, but may occur in immense numbers and often cause harmful "blooms".

4.  Phytoplankton are autotrophic:  that is, they make their own food by photosynthesis
a. Photosynthesis is a process that occurs during the day in sunlight
b. carbon dioxide and water are used, with sunlight, to make a glucose molecule with a waste product of oxygen.

5.  Primary productivity = synthesis of organic matter from inorganic substances
••Expressed in grams of carbon per unit area per unit time
• (grams/meter²/day)
• (grams/meter²/year)

Where is the highest productivity?

Oceans                            grams/meter²/day

    Coral reef                    880-2200

    Kelp Bed                    400-1900

    Shelf Plankton                90-270

    Open Ocean                    1-180

Land

    Rain forest                    460-1600

    Temperate forest           270-1140

    Freshwater swamp        360-1820

    Cropland                        45-1820

6•Where does photosynthesis take place in the ocean?:
•- maximum activity just below surface
•-   decreases with depth

7.  Where does respiration take place in the ocean?:
•-  does not depend on depth
•What is the compensation depth?  Where   Photosynthesis  = Respiration.
Some communities in the ocean are more productive than others:
 Coral Reefs and coastal communities are more productive than the open ocean

8.  Algal Blooms:  Algae often go through “blooms” or population explosions that are seasonal in nature (spring and late summer).  Although microscopic as individuals, once they undergo a “bloom” they can be seen from space!  Example is the microscopic Coccolithophore, named Ehux (Emiliani huxleyi).•

9. Some phytoplankton generate toxic chemicals or decay so fast they use up all the oxygen in the water column.
•This is can be harmful to other marine and coastal life
•Examples:
•- ”Red or Brown tides"
•- Ciguatera
Most are generated by dinoflagellate algal blooms.  These algae produce poisons that can cause paralysis, diarhea, memory loss, coma and death in humans.  The toxins are easily taken up by filter feeding shellfish, and also some toxins are taken up by crabs and lobsters.

Blooms are triggered by excess nutrients in surface waters, particularly by heavy
Runoff of fertilizer or sewage laden water from rivers following big storms.

10.What are zooplankton?  Most are
Primary consumers-called primary heterotrophs meaning, they feed on the phytoplankton
     can be Juveniles of large invertebrates, spending  their early phases floating in the surface waters.
     or can be Fully adult, just very small, animals.

11.  An overwhelming number of zooplankton are crustaceans-some are tiny adults
And some are juvenile crustaceans that will eventually settle down and grow to be large adults that live on the sea floor, like crabs and lobsters

Crustaceans are the most successful class of marine animals. 

12.  Many are consumed by secondary consumers (small fish) but some are fed on by the
balleen whales.  Krill are a good example of this.  Krill are tiny crustaceans that swim in
the surface waters, particularly in the Antarctic circumpolar current.  They are a major food source for these whales.

13.  Plankton form the lower portion of the food web, with phytoplankton serving as the base of the food web.  If big changes happen to this population,
those changes will be felt up the line to other organisms.  The plankton are sensitive indicators of the health of the ocean.

Next Lecture:  Ecology & Open Ocean Communities