Download Chapter 8: Aquatic Biodiversity

Jason Zheng
 The
Earth is made mainly of Water.
 Saltwater covers around 71% of the earth’s
surface.
 Freshwater occupies only about 2.2%
 Global Ocean: is a single and continuous
body of water, geographers divide it into
four large areas- Atlantic, Pacific, Arctic, and
Indian.
 The Largest ocean is the Pacific, which
contains more than half of the earth’s water.
 Aquatic
life Zones- saltwater and freshwater
portions of the biosphere that can support
life.
 Distribution of many aquatic organisms is
determined largely by the water’s salinity.
 Saltwater or marine life zones: Oceans,
bays, estuaries, coastal wetlands, shorelines,
coral reefs, and mangrove forests.
 Freshwater life zones: Lakes, rivers, streams,
and inland wetlands.
 Saltwater
and freshwater contains
organisms called planktons.
 There are three groups of planktons:
Phytoplankton which includes many types
of Algae. Zooplankton which consists of
primary consumers, they feed off of each
other. Ultraplankton which are small
photosynthetic bacteria which are in 70% of
ocean surface.
 Decomposers: breaks down organic
compounds in dead bodies and wastes.
 The
marine coastal ecosystems make over
$12 Trillion per year.
 Coastal Zone- The warm, nutrient-rich,
shallow water that extends from the hightide mark on land to the gently sloping,
edge of continental shelf.
 Most coastal zone aquatic systems such as
estuaries, coastal marshes, mangrove
forests, and coral reefs have a high net
primary productivity.
 Estuaries- are where rivers meet the sea.
 Coastal Wetlands-
coastal land areas
covered with water all or part of the year.
 Sea grass beds are another component of
coastal marine biodiversity.
 Mangrove forests are found along some
70% of gently sloping sandy coastlines in
tropical and subtropical regions,
especially Australia and Southeast Asia.
Intertidal zone- The area of shoreline between
low and high tides.
 Organisms living in this zone must not be swept
away or crushed by waves.
 Some coasts have steep rocky shores that are
pounded by waves.
 Other shores have sloping sandy shores that has
different types of organisms.
 Coral reefs are the worlds oldest, most diverse,
and productive ecosystem.
 Open sea- sharp increase in water depth at the
edge of the continental shelf separates the
coastal zone from the vast volume of the ocean.
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 In
2008, scientists have tried 17 different
human activities in oceans and it affect the
worlds ocean by 41%.
 In 2010, 45% of the worlds population and
more than half of the US population lived
along the coast has experienced rapid
changes.
 Major Threats include: Coastal
development, Runoff of nonpoint source
pollutants, Point-source pollutants, Pollution
and degradation, overfishing, and fishing
trawlers.
 Between
1940 and 2007, the number of
people living in the Chesapeake Bay
area grew from 3.7 million to 16.8 million,
and could reach 18 million by 2020.
 The estuary receives wastes from point
and non- point sources scattered
throughout a huge drainage basin in
parts of six states and the District of
Columbia.
 However, by
2008, despite 25 years of
effort costing almost $6 billion, the
program had failed to meet its goals.
 This was because of increased
population and development, a drop in
state and federal funding, and lack of
cooperation and enforcement among
local, state, and federal officials.
Freshwater life zones include standing bodies of
freshwater such as lakes, ponds, and inland
wetlands, and flowing systems such as streams
and rivers.
 Although these freshwater systems cover less
than 2.2% of the earth’s surface, they provide a
number of important ecological and economic
services.
 Lakes are large natural bodies of standing freshwater formed when precipitation, runoff, streams,
rivers, and groundwater seepage fill depressions
in the earth’s surface.
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Freshwater lakes vary tremendously in size, depth, and nutrient
content. Deep lakes normally consist of four distinct zones that are
defined by their depth and distance from shore.
The top layer, called the littoral zone, is near the shore and
consists of the shallow sunlit waters to the depth at which rooted
plants stop growing.
The next layer is the limnetic zone, the open, sunlit surface layer
away from the shore that extends to the depth penetrated by
sunlight. The main photosynthetic zone of the lake, this layer
produces the food and oxygen that support most of the lake’s
consumers.
Next comes the profundal zone, a layer of deep, open water where
it is too dark for photosynthesis.
The bottom layer of the lake is called the benthic zone, inhabited
mostly by decomposers, detritus feeders, and some species of
fish.
Ecologists classify lakes according to their
nutrient content and primary productivity. Lakes
that have a small supply of plant nutrients are
called oligotrophic lakes.
 Glaciers and mountain streams supply water to
many such lakes, bringing little in the way of
sediment or microscopic life to cloud the water.
 Over time, sediment, organic material, and
inorganic nutrients wash into most oligotrophic
lakes, and plants grow and decompose to form
bottom sediments. A lake with a large supply of
nutrients needed by producers is called a
eutrophic lake.

 First, dams
and canals fragment about 40%
of the world’s 237 largest rivers.
 Second, flood control levees and dikes built
along rivers disconnect the rivers from their
floodplains.
 A third major human impact on freshwater
systems comes from cities and farms.
 Fourth, many inland wetlands have been
drained or filled to grow crops or have been
covered with concrete, asphalt, and
buildings.
The rest were lost to mining, logging, oil and gas
extraction, highway construction, and urban
development. The heavily farmed U.S. state of
Iowa has lost about 99% of its original inland
wetlands.
 This loss of natural capital has been an important
factor in increased flood damage in the United
States, which are examples of unnatural disasters.
Many other countries have suffered similar
losses.
 For example, 80% of all inland wetlands in
Germany and France have been destroyed.
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 Three
Big Ideas:
 Saltwater and freshwater aquatic life zones
cover almost three-fourths of the earth’s
surface, and oceans dominate the planet.
 The earth’s aquatic systems provide
important ecological and economic
services.
 Human activities threaten biodiversity and
disrupt ecological and economic services
provided by aquatic systems.