Chapter 8 Review
What is the general nature of aquatic
systems?
• Most of the Earth (71%) is covered in water an
divided by the four main oceans, the Atlantic,
Pacific, Arctic and Indian oceans.
• The distribution of species is determined by the
salinity (saltiness) of water which splits the
aquatic life zones into two major categories
• The first is saltwater (marine) life zones which
consists of oceans, coastal wetlands, estuaries,
coral reefs, shorelines, and mangrove forests
• The next is freshwater life zones which contains
lakes, rivers, streams, and inland wetlands
• Most aquatic species live in the top, middles, or bottom
layers of water. There are many types of organisms.
• Plankton species can be divided into three groups.
Phytoplankton (drifting plants) includes algae and plants along
the shorelines that are the primary producers that supports
most aquatic food webs. Zooplankton (drifting animals) is
made up of primary and secondary consumers ranging from
single celled protozoa to larger species such as jelly fish. Ultra
plankton (bacteria) are responsible for 70% of the primary
productivity near the ocean surface.
• Another main type of organism is nekton which consists of
strong swimming species like turtles and fish.
• The third main group of organism is benthos
includes bottom dwellers such as sea stars,
oysters, worms, lobsters and crabs.
• The fourth is the decomposers of the ocean
which breaks down dead fish and wastes and
converts them into nutrients that the
producers of the seas can use.
• The temperature, dissolved oxygen content,
availability of food and light, and nutrients
determines what organisms can live where.
Why are marine aquatic systems
important?
• Oceans provide vital economic and ecological services.
The estimated value of the goods and services we get from
the ocean is $12 trillion a year.
• We don’t know a lot about the ocean but we know that the
ocean helps support the Earths biodiversity. Ocean
organisms are mainly found in the coastal zones, open
ocean, or the ocean bottom.
• The coastal zone is the warm, nutrient rich, shallow water
that extends from the high tide mark on land to the gently
sloping edge of the continental shelf. Coastal zones include
mangrove forests, estuaries, and coral reefs. These zones
tend to have a high net primary productivity rate.
• Estuaries and coastal wetlands are highly productive.
• Estuaries are areas where rivers meet the sea. In these areas,
seawater and freshwater mixes as well as nutrients and
pollutants.
• Coastal wetlands are areas on land that are covered in water
year around such as river inlets, bays, coastal marshes, sounds
and mangrove forests. These areas have ample sunlight and
nutrients. Sea grass beds contains at least 60 species of
plants.
• Coastal ecosystems are harsh to live in because they must
adapt quickly to daily and seasonal tidal changes, pollutants,
and weather. As a result, some coastal ecosystems have low
plant diversity.
• Coastal ecosystems help maintain water quality in tropical
zones by filtering pollutants, extra nutrients, and sediments.
• Rocky and sandy shores hot different types of organisms
• The area of shoreline between low and high tide is called the
intertidal zone. Organisms who live here must deal with changes in
salinity, heavy crashing waves during high tide, and loss of water
and increase in heat during low tide.
• On some coasts, rocky shores are pounded by waves
• Other coasts have gently sloping barrier beaches (sandy shores)
• Organisms that live on both coasts must adapt to their
surroundings. For example, organisms on sandy beaches are able to
dig or burrow into the sand.
• Coral reefs are amazing centers of biodiversity and provides homes
for ¼ of all marine species
• Open sea and the ocean floor hosts a variety of species
• Open sea is the increase in depth at the edge of the continental
shelf. There are three main layers of water, classified by organisms
that live there, depth, and amount of sunlight.
• The topmost zone is called the euphotic zone. It is brightly lit and
phytoplankton carries out 40% of the worlds photosynthetic activity
here. Nutrient levels are low unless there are upwellings where
ocean current carry nutrients from the bottom up to the surface
here and levels of dissolved oxygen is high. Strong swimming
organisms can be found in this zone.
• The dimly lit middle zone is called the bathyal zone. There is little
sunlight and no photosynthesizing producers. Zooplankton and
small fish populates this zone.
• The abyssal zone is the lowest and darkest zone. It receives no
sunlight so it is very cold. This zone has low levels of dissolved
oxygen. Organisms who live here get their food from marine snow,
dead and decaying organisms drifting from the upper layers. Some
abyssal zone organisms like worms are deposit feeders which
means they take mud into their systems and extract nutrients from
it. Filter feeders like oysters and clams extract nutrients from the
water they pass through themselves.
• Production in the open sea is very low, except in the upwelling
areas but since it covers so much space, it contributes to most of
the worlds net production.
How have human activities affected
marine ecosystems?
• Human activities are disrupting and degrading marine ecosystems
and the services they provide for us especially in coastal marshes,
mangrove forests, coral reefs and shorelines. A four year study
conducted by the NCEAS found that human activity has heavily
affected 41% of the world oceans and no parts of the oceans have
been left untouched. People who live near the coast are destroying
and degrading the aquatic biodiversity. Forty-five percent of the US
lives near the coast and that number is rapidly increasing.
• Major threats to marine systems from human activities includes
coastal development, runoff from pollutants, pollution from cruise
ships and oil tankers, pollution and degradation from coastal
wetlands, overfishing, weighted fishing nets that drag across the
bottom of the ocean, invasive species, and climate change that is
caused by humans.
• Major impacts on marine ecosystems include
the loss of half of our coastal wetlands due to
agriculture and urban development, loss of
one-fifth of mangrove forests due to
agriculture and urban development and
shrimp farms, erosion of beaches because of
coastal development and rise in sea level,
ocean bottom habitats degraded because of
weighted nets, and at least 20% of coral reefs
degraded and 25-33% more threatened.
• Major impacts on coral reefs include ocean
warming, rising ocean acidity, soil erosion,
algae growth from fertilizer runoff, bleaching,
rising sea levels, increased UV exposure,
damage from anchors, and damage from
fishing and diving.
Why are freshwater ecosystems
important?
• Water stands in some freshwater systems and flows
in others
• When water stands (lakes), it is called a lentic body
of water and when the water flows (rivers) it is called
a lotic body of water. These freshwater systems cover
less than 2.2% of the earths surface but they still
provide many goods and services.
• Lakes are formed by precipitation or runoff filling
depressions caused by volcanic activity and
glaciation.
• Lakes vary in size, depth, and nutrient content. Deeper lakes
have four distinct zones classified by their distance form the
shore and their depth. The top layer nearest the shore is
called the littoral zone and consists of the shallow sunlit
waters where rooted plants stop growing. Organisms such as
turtles, frogs and crayfish reside here.
• The next layer is the sunlit limnetic zone away from the shore.
This layer produces food and oxygen that supports the lakes
consumers. Phytoplankton and zooplankton live here along
with some larger species of fish.
• The third layer is called the profundal zone, a layer of deep,
open water that is too dark for photosynthesis. Oxygen levels
here are low and fish have adapted to the cold and the
darkness.
• The last layer is called the benthic zone located at the very
bottom of the lake and mostly inhabited by decomposers,
detritus feeders, and some fish (benthos).
• Some lakes have more nutrients than others
• Lakes with small amounts of nutrients are called oligotrophic
lakes. These types of lakes are usually deep with steep banks.
• Most lakes get their water from mountain streams and have
low populations of phytoplankton and fish. This is why they
have a low net productivity.
• In time, dead plants go to the bottom and lakes become more
nourished. These lakes are called eutrophic lakes. These lakes
have a high net productivity.
• Some lakes can go through a process called cultural
eutrophication where fertilizer causes excessive nutrients.
These lakes are called mesotrophic lakes.
• Fresh water streams and rivers carry water form the
mountains to the oceans.
• Precipitation that does not sink into the ground is called
surface water. When it flows into streams it becomes runoff.
The land area that delivers the runoff to a stream is called a
watershed, or a drainage basin.
• Freshwater inland wetlands are vital sponges.
• Inland wetlands is a piece of land away form the coast that’s
always covered in water, excluding lakes, rivers, and streams,
and including marshes, swamps, and prairie potholes.
• They include many free ecological services that include
filtering and degrading toxic wastes and pollutants, reducing
flooding and erosion, helping to replenish streams, helping to
recharge groundwater aquifers, helping to maintain
biodiversity, supplying valuable supplies, and providing
recreation.
How have human activities affected
freshwater ecosystems?
• Human activities are disrupting and degrading freshwater systems
• Man made dams and canals fragment about 40% of the worlds 237
rivers.
• Flood control levees and dikes disconnect rivers from their
floodplains, destroy aquatic habitats, and alter or reduce the
functions of nearby wetlands.
• Cities and farms add pollutants and excess plant nutrients to nearby
bodies of water
• Many inland wetlands have been drained or filled to grow crops.
Eighty percent of wetlands were destroyed to grow crops.
• The loss of natural capital has been an important factor in increased
flood damage in the US.
The chapters 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
eco- logical and economic services.
• Human activities threaten biodiversity and
disrupt ecological and economic services
provided by aquatic systems.