Chapter 3 Life in water

1
Chapter 3 Life in water

• Over 71 of the earths surface is covered by
  water,which includes lakes, rivers, and oceans.
  The oceans contain over 97 of the water in the
  biosphere, and the polar ice caps and glaciers
  contain 2, and rivers, lakes, and actively
  exchanged groundwater.

2

• Hydrologic cycle The distribution of water
  across the biosphere is not static, but moving
  from time to time. This dynamic exchanges of
  water in the biosphere is called the hydrologic
  cycle (Fig.3.2).
• Turnover time is the time required for the
  entire volume of a particular reservoir to be
  renewed. The turnover time of atmospheric water
  is c. 9 days of ocean water, 3100 years.

3
The deep blue sea (Fig. 3.3)

• Geography The world ocean covers gt 360 million
  km2 of earths surface, and consists of one
  continuous, interconnected mass of water. It
  includes 3 major ocean basins The Pacific,
  Atlantic and Indian (Fig 3.5).
• The Pacific Ocean c. 180 million km2, average
  depth over 4000m.
• The Atlantic Ocean c. 106million km2, average
  depth 3900m.
• The Indian Ocean c. 75million km2, average
  depth 3900m.

4

• Structure
• Horizontal structure.
• --Littoral(??)/Intertidal zone shallow
  shoreline area affected by the rise and fall of
  the tides.
• --Neritic zone(???) area from the coast to
  the margin of the continental shelf, with a depth
  of c. 200m.
• --Ocean zone area beyond the continental
  shelf.

5

• Vertical structure
• --The epipelagic zone(?????) the surface
  layer of the ocean, from the surface extending to
  a depth of 200m.
• --The mesopelagic zone from 200m to 1000m.
• --The bathypelagic zone(???) from 1000m to
  4000m.
• --The abyssal zone(????) from 4000m to 6000m.
• --The hadal zone(????) gt6000m (deepest parts
  of the ocean (Fig. 3.6).

6

• Physical conditions
• Light c. 80 of the solar energy striking the
  ocean is absorbed in the first 10m. Most
  ultraviolet and infrared light is absorbed in the
  first few meters. Red, orange, yellow, and green
  lights are absorbed more rapidly than blue light.

7

• Temperature Oceanic temperatures are much more
  stable than terrestrial temperatures, with the
  lowest average oceanic temperature c. 1.5 oC
  (around the Antarctic), and the highest average
  temperature a bit more than 27 oC (near the
  equator). Maximum annual variation c. 7-- 9 oC
  (occurring in the temperate zone above 40o N.

8

• Water movement
• Gyres(??) Moving from equatorial area toward
  the poles, transporting warm water and moderating
  climates at middle and high latitudes. Gyres
  generally move to the right in the Northern
  Hemisphere and to the left in the Southern
  Hemisphere (Fig. 3.5).

9

• Upwelling(???) Occurring along the west coasts
  of continents and around Antartica, cold water
  rises to the surface and bring the surface water
  offshore. Upwelling results cold and dry climate
  in the coast regions (Fig. 3.5).

10

• Chemical conditions
• Salinity varying with latitudes and among the
  seas.
• The lowest salinity occurs near the equator
  and above 40 oN and 40 oS, where precipitation
  exceeds evaporation.
• The highest salinity is in the subtropics and
  above 20 to 30 oN an oS, where precipitation is
  low and evaporation is high.

11

• The relative proportion of the major ions, Na,
  Mg, Cl-, remain approximately constant from one
  part of the sea to another.

12

• Oxygen far lower concentration and much more
  variation in sea water than in aerial
  environments. Maximum 9 ml O2 per litter water
  comparing 200 ml O2 per litter air.
• Typically, oxygen concentration is highest
  near the ocean surface and decreases
  progressively with depth to about 1000m, and then
  increases progressively to the bottom.

13

• Biology
• --Phytoplankton community of microscopic
  photosynthetic organisms, which is in the
  euphotic zone.
• --Zooplankton community of microscopic
  animals, which is also in the euphotic zone.
• --Deep-sea organisms Canivorous animals, such
  as sharks, whales, and many other fishes, which
  are distributing in entire water column.
  Chemosynthetic organisms in the sea floor, which
  are nourished not by photosyntesis, but by
  chemosynthesis with undersea hot springs (Fig.
  3.8).

14

• --Higher diversity in the ocean species
  diversity in the ocean would rival that of the
  tropical rain forest. More endemic taxa (Fig
  3.9).
• Human Influences
• Overharvest ex. Whales.
• Pollution.

15
Life in shallow waters Kelp forests and coral
gardens

• The shallow waters along continents and islands
  support marine communities of very high diversity
  and biomass. Main marine communities are Kelp and
  coral reef.
• --Kelp grove of seaweed in temperate sea.
  Some kelps grow to a length over 40m, and in such
  densities that they resemble submarine forests
  (Fig.3.10, Fig.3.14).

16

• --Coral reef community in tropical sea.
  Corals are animals that secrete a stony skeleton,
  and depend on photosynthesis by photosynthetic
  protists called zooxanthellae that live in their
  tissues (Fig.3.11).
• --Geographical distribution of kelps and coral
  reefs as in Fig.3.12.

17
Estuaries, salt marshes, and mangrove forests

• Estuaries area where rivers meet the sea.
• Salt marshes places covered by herbaceous
  vegetation along sandy shores from temperate to
  high latitudes (Fig.3.20, Fig.3.23).
• Mangroves forests distributing along tropical
  muddy sea shores (Fig.3.21, Fig.3.25).
• Geographical distribution of salt marshes and
  mangroves as in Fig.3.22.

18
Rivers and streams Life blood and pulse of the
continents

• Geography major rivers in the world (Fig.3.29)
• Structure rivers and streams can be divided
  along their lengths into pools, runs, riffles
  and rapids, and can be divided into wetted
  channels and active channels across their widths.

19

• Vertical structure of a river water surface
  water column bottom/benthic zone
• Hyporheic zone a zone of transition between
  areas of surface water flow and groundwater
• Phreatic zone area containing groundwater
  below the hyporheic zone.
• Vertical structure is shown in Fig.3.30

20
Physical Conditions

• Light reduced light because of suspending
  inorganic and organic matters. Shaded by riparian
  vegetation at headwaters.
• Temperature smaller variation comparing air
  temperature.
• Water movement
• River discharge water amount carried by a
  river. River discharge varied from seasons, from
  year to year, and from different climate zones
  (Fig.3.32).

21
Chemical conditions

• Salinity related rainfall of a zone. Wet
  tropic has low salinity(Fig.3.33).
• Oxygen oxygen content is inversely correlated
  with temperature. Organic waste pollution can
  reduce oxygen content.

22
Biology

• Species number varies between rivers of different
  climate zone, tropical rivers have higher species
  diversity than temperate high latitude rivers.
• Species are different at different parts of a
  river (Fig.3.34).

23
Lake small seas

• Lakes are basins collecting water which are
  worked over by geological forces including
  shifting of the earths crust, volcanism, and
  glacial activity. (Fig.3.35)

24
1. Geography

• Distribution of some major lakes (Fig.3.36).

25
2. Structure

• Horizontally two zones
• Littoral zone shallowest waters along the
  lake shore, where rooted aquatic plants may grow.
  
• Limnetic zone area beyond the littoral zone.
• Vertically three main depth zones
• the epilimnion the warm surface layer.
• the thermocline/metalimnion below the
  epilimnion
• the hypolimnion the deepest layer of lakes.
  (Fig.3.37))

26
3. Physical Conditions

• Temperature vertical variation of temperature
  in a temperate lake
• In summer, temps decrease with depth
• In winter, temps increase with depth
• In spring and fall, water temp is uniform.
  (Fig.3.38).

27

• Water movements Like tropical sea, tropical
  lakes at low elevations are permanently
  stratified. Tropical lakes at high elevations
  heat and stratify every day and cool to mix every
  night.
• Water movement of temperate lakes as showed in
  Fig.3.38.
• Patterns of mixing have profound consequences
  to the chemistry and biology of lakes.

28

• Oxygen
• Oligotrophic nearly always well oxygenated.
• Eutropic may be depleted of oxygen.
• Biology ( Fig.3.39)
• Oligotrophic lakes low biological production,
  species requiring high oxygen.
• Eutropic lakes high biological production,
  species tolerant low oxygen.

29

• Human Influences
• 1. Dumping nutrients of toxic waste into lakes,
• 2. Introducing exotic species into lakes
  (Fig.3.40).
• 3. Occupying areas of lakes.