ch 14 ocean life

sea water composition:

• sewater is 3.5% dissolved minerals

• salinity: amount of solid material dissolved in water

  • expressed in parts-per-thousand %00

  • average is 3.5% in weight

  • major constituent - sodium chloride

  • salt often comes from rocks

processes affecting seawater salinity:

• decreasing salinity - adding water

  • precipitation

  • runoff from land

  • icebergs melting

  • sea lice melting

• increasing salinity - removing water

  • evaporation

  • formation of sea ice

ocean acidity:

• 1/3 of human generated co2 ends up dissolved in oceans

• ocean pH goes down bc of humans

• if humans continue, by 2100 pH with drop .3 unit - not seen in millions of years and makes it more difficult for marine creatures to build hard parts

• acidity goes up bc carbon dioxide dissolved in ocean water, and acidification is caused by carbonic acid

ocean temperature:

• surface water temp varies /w amount of solar radiation recived

  • lower surface temp - in high-latitude regions

  • higher temp - in low-latitude regions

ocean density: mass per volume unit

• determines water’s vertical position in ocean

• factors affecting seawater density

  • salinity

  • temperature (greatest influence)

density - ocean layering:

• 3 layered structure

  1. surface mixed zone

     • sun-warmed zone

     • zone of mixing

     • shallow (300 meters)

  2. transition zone

     • between surface and deep zone

     • termocline and pycnocline

  3. deep zone

     • no sunlight

     • temp just a few degrees above freezing

     • high-density water

ocean life:

• most organisms live within sunlight zone (photic/photosynthesis)

• classified by where they life and how they move

• success of marine life depends on avoiding predators

  • plankton

  • nekton

  • benthos

plankton (floaters): microscopic organisms that float in ocean and are major food source

• phytoplankton - produces food vis photosynthesis

• zooplankton - must eat food

nekton (swimmers):

• all animals capable of moving independently of ocean currents

• able to move throughout breadth of ocean

benthos (bottom dwellers):

• live on surface of seafloor

• great # of species exist on shallow coastal floor w/ some sunlight

• most live in darkness in deep water

marine life zones: based on…

1. availability of light

   • photic (ligh) zone

     • upper part of ocean

     • sunlit

     • euphotic zone near surface where light is strong

   • aphotic (w/o light) zone

     • deep ocean

     • no sunlight

2. distance from shore

   • intertidal zone - where land and ocean meet and overlap

   • neritic zone - seaward from the low tide line, the continental shelf out to the shelf break

   • oceanic zone - beyond continental shelf

3. water depth

   • pelagic - open ocean w/ any depth

   • benthic - includes any sea-bottom surface

   • abyssal zone - subdivision of benthic zone

     • deep, high water pressure, low temp, no sun, sparse life

     • food sources: decaying particles from above, large falling fragments, hydrothermal vents

ocean productivity:

• primary productivity (food sources)

  • rate which organisms store energy through formation of organic mater

  • energy is derived from photosynthesis (solar radiation) and chemosynthesis (chemical reactions)

  • influenced by availability of nutriends and amount of solar radiation

productiviy in polar oceans:

• bc nutrients rising from deeper water, high lat surface waters have high nutrient concentrations

• low solar energy limits photosynthetic productivity

productivity in temperate oceans

• winter: low productivity, days are short and sun angle is low

• spring: spring blood of phytoplankton is quickly depleted and producivity is limited

• summer: strong thermocline develops, surface nutriends are no replaced from below. phytoplankon population remains low

• fall: thermocline breaks down, nutrients return to surface. short lived fall bloom of phytoplankton

• highest productivity occurs in temperate regions

• productivity in temperace oceans show marked seasonal variation

productivity in tropical oceans

• low in the open ocean

• thermocline eliminates supply of nutriends from deeper waters below

main oceanic producers - only small % of energy taken in at any level is passed onto the next

• marine algae

• plants

• bacteria

• bacteria-like archaea

trophic levels

• feeding stage where chem energy is transferred though animal community

• ex: algae - zooplankton - fish - shark

• energy between trophic levels is inefficient (2%)

food chain: sequence of organisms through which energy is transferred

food web: involved feeding on a number of different animals

• animals that feed through food web rather than chain are more likely to survive

other facts:

• prevailing winds are main energy source for driving surface ocean currents