I.
Miller Chapter 8 Review
Chapter 8: Aquatic Biodiversity
a. 8-1: What is the General Nature of Aquatic Systems?
i. Saltwater covers about 71% of the earth’s surface and freshwater occupies roughly
another 2.2%
ii. Oceans: Atlantic, Pacific (the largest), Arctic, and Indian
iii. Aquatic equivalents of biomes are called AQUATIC LIFEZONES
1. Distribution of many aquatic organisms is determined largely by the water’s
salinity
2. Saltwater (Marine Life Zones) – oceans and their bays, estuaries, coastal
wetlands, shorelines, coral reefs, and mangrove forests
3. Freshwater Life Zones – lakes, rivers, streams, and inland wetlands
iv. Aquatic Species:
1. Plankton – can be divided into three groups
a. Phytoplankton – drifting organisms, includes many types of algae
b. Ultraplankton – smaller than phytoplankton, through photosynthesis
they produce about half of the earth’s oxygen, on which we depend for
survival
c. Zooplankton – feed on phytoplankton and on other zooplankton
2. Nekton – strongly swimming consumers
a. Fish, turtles, whales
3. Benthos – consist of bottom dwellers
a. Oysters, sea stars, clams, lobsters
4. Decomposers – mostly bacteria
v. Key factors determine the types and numbers of organism found in different areas
of the ocean are temperature, dissolved oxygen content, availability of food, and
availability of light and nutrients required for photosynthesis
1. Photosynthesis is largely confined to the upper layer – the euphotic or photic
zone
2. Algal Blooms – results from nutrient overloads
3. Turbidity – cloudiness
b. 8-2: Why Are Marine Aquatic Systems Important?
i. Oceans provide enormously valuable ecosystem and economic services
ii. Enormous reservoirs of biodiversity
iii. Marine life is found in three major zones:
1. The Coastal Zone – the warm, nutrient-rich shallow water that extends from
the high-tide mark on land to the gently sloping, shallow edge of the
continental shelf
a. Makes up less than 10% of the world’s ocean area, but it contains 90%
of all marine species
b. Includes estuaries, coastal marshes, mangrove forests, and coral reefs
i. Estuary – where a river meets the sea
1. Estuaries are associated with coastal wetlands – coastal
land areas covered with water all or part of the year
2. Include:
a. Coastal Marshes and mangrove forest – the
earth’s most productive ecosystem
b. Sea-grass beds – have a high NPP due to ample
supplies of sunlight and plant nutrients that flow
from land and are distributed by wind and ocean
currents
ii. Economic Services – they help to maintain water quality in
tropical coastal zones by filtering toxic pollutants, provide
food, habitats, and nursery sites for a variety of aquatic and
terrestrial species --- they also reduce storm damage and
coastal erosion
c. Tides – caused by the gravitational pull of the moon and sun, rise and
fall about every 6 hours in most coastal areas
i. Intertidal Zone – the area of shoreline between low and high
tides
ii. Tidal Pool – steep rocky shores
iii. Barrier beaches or sandy shores (NC has these)
iv. Barrier Islands – low narrow, sandy islands that form offshore,
parallel to nearby coastlines (NC has these)
2. The Open Sea – the sharp increase in water depth at the edge of the
continental shelf separates the coastal zone from the vast volume of ocean
a. Different zones based of the penetration of sunlight
i. Euphotic Zone – the brightly light upper zone, where drifting
phytoplankton carry out about 40% of the world’s
photosynthetic activity.
1. Nutrient levels are low and levels of dissolved oxygen
levels are high
ii. Upwelling Zone – where ocean currents driven by coastal
winds or by differences in temperature at different depths
being water up from the deepest waters
1. Carry nutrients from the ocean bottom to the surface
for use by producers and thus these zones contain high
levels of nutrients
iii. Bathyal Zone – the dimly lit middle zone, which receives little
sunlight and therefore does not contain photosynthesizing
producers
b. NPP is quite low in the open sea, except in upwelling areas, however it
makes the largest contribution to the earth’s overall NPP
3. The Ocean Bottom
a. Abyssal Zone – the lowest zone, there is no sunlight to support
photosynthesis and this zone has little dissolved oxygen
b. Marine Snow – showers of dead and decaying organisms
i. Drift down from upper, lighted levels of the ocean
c. Deposit Feeders – which take in mud into the guts and extract
nutrients
d. Filter Feeders – pass water through or over their bodies and extract
nutrients
4. Coral Reefs – among the world’s oldest and most diverse and productive
ecosystems
a. Worldwide coral reefs are being damaged and destroyed at an
alarming rate by a variety of human activities
i. Ocean Acidification – an increasing levels of acid in the world’s
oceans, occurs because the oceans absorb about a third of the
CO2 emitted into the atmosphere by human activities
c. 8-3: How Have Human Activities Affect Marine Ecosystems?
i. Major Threats Include:
1. Coastal Development
2. Runoff of nonpoint sources of pollutants
3. Point-Source Pollution
4. Pollution and degradation of coastal wetlands and estuaries
5. Overfishing
6. Use of fishing trawlers – degrading and destroying habitats
7. Invasive Species
8. Ocean Warming
9. Ocean Acidification – known as the “other CO2 problem”
a. Tends to threaten coral reefs, phytoplankton, and many shellfish that
form their shells from calcium carbonate
ii. Sea-grass beds are being lost to pollution and other disturbances
iii. Slowly melting land-based glaciers in Greenland and other parts of the world could
cause a rise in sea levels (during this century) which would destroy shallow coral
reefs and flood coastal marshes and many coastal cities
iv. Case Study – The Chesapeake Bay – An Estuary in Trouble
1. Receives wastes from point and nonpoint sources scattered throughout its
huge drainage basin
a. Become a huge pollution sink – phosphate and nitrate levels
2. Integrated Coastal Management – a citizen’s group, communities, state
legislatures, and the federal government worked together to reduce pollution
inputs into the bay
a. After 25 years of effort costing almost $6 billion, the Chesapeake Bay
Program had failed to meet its goals.
i. Due to increased population and development, a drop in state
and federal funding, and a lack of cooperation and enforcement
among local, state, and federal officials
d. 8-4: Why Are Freshwater Ecosystems Important?
i. Surface Water – precipitation that does not sink into ground or evaporate
ii. Freshwater life zones include:
1. Standing (Lentic) bodies
a. Lakes, Ponds, Inland Wetlands
2. Flowing (Lotic) systems
a. Streams and Rivers
iii. Surface water that flows into such bodies of water is called runoff
iv. Watershed (Drainage Basin) – is the land area that delivers runoff, sediment, and
dissolved substance to a stream, lake, or wetland
v. Lakes – large natural bodies of standing water formed when precipitation, runoff,
streams, rivers, and groundwater seepage fill depressions in the earth’s surface
1. Freshwater lakes vary tremendously in size, depth, and nutrient content
a. Deep lakes has four distance zones that are defined by their depth and
distance from shore
i. Littoral (top layer) – near the shore and consists of the shallow
sunlit waters to the depth at which rooted plants stop growing,
high levels of biodiversity
ii. Limnetic (middle layer closest to the top) – open, sunlit surface
layer away from the shore that extends to the depth penetrated
by sunlight, the main photosynthetic zone, layer that produces
the food and oxygen that support most of the lake’s consumers
iii. Profundal Zone (middle layer closest to the bottom) – deep,
open water where it is too dark for photosynthesis, oxygen
levels are often low here
iv. Benthic Zone (bottom layer) – inhabited mostly by
decomposers detritus feeders, and some species of fish
(benthos), nourished mainly by dead matter that falls from the
littoral and limnetic zones and be sediment washing into the
lake
b. Classify lakes according to their nutrient content and primary
productivity
i. Oligotrophic Lakes – have a small supply of plant nutrients
1. Often deep and has steep banks
2. Usually have crystal-clear water and small populations
of phytoplankton and fish species
3. Have a low NPP
ii. Eutrophic Lake – a large supply of nutrients
1. Typically shallow and have murky brown or green
water with high turbidity
2. High NPP
iii. Mesotrophic Lakes – fall somewhere between the two
extremes of nutrient enrichment
c. Cultural Eutrophication – often puts excessive nutrients into lakes,
and can accelerate the eutrophication of the lake
vi. Streams and Rivers – the downward flow of surface water and groundwater from
mountain highlands to the sea typically takes place in three aquatic life zones
(characterized by different environmental conditions)
1. Source Zone – headwater streams are usually shallow, cold, clear, and swiftly
flowing
a. Dissolves large amounts of oxygen from the air, most of these streams
are not very productive because of a lack of nutrients and primary
producers
2. Transition Zone – headwater streams merge to form wider, deeper, and
warmer streams that flow down gentler slopes with fewer obstacles
a. Can be turbid (containing suspended sediment) and slower flowing
than headwater streams, and they tend to have less dissolved oxygen
b. Warmer water
3. Floodplain Zone – streams join into wider and deeper rivers that flow across
broad, flat valleys
a. Usually has higher temperatures and less dissolved oxygen
b. Water in the floodplain zone often is muddy and contains high
concentrations of suspended particulate matter (silt)
vii. Deltas – an area at the mouth of a river that was built up by deposited sediment and
contains coastal wetlands and estuaries
viii. Coastal deltas, mangrove forests, and coastal wetlands provide considerable natural
protection against flood and wave damage from coastal storms, hurricanes,
typhoons, and tsunamis
1. Multiple dams, levees, and canals built in this river system funnel much of
this sediment load through the wetlands and out into the Gulf of Mexico
a. Instead of building up delta lands, this causes them to subside or to
sink
ix. Inland Wetland – lands located away from coastal areas that are covered with
freshwater all or part of the time – excluding lakes, reservoirs, and streams
1. Include marshes, swamps, and prairie potholes, floodplains – which receive
excess water during heavy rains and floods
a. Some wetlands are covered with water year-round, others called
seasonal wetlands remain under water or are soggy for only a short
time each year
2. Provide a number of free ecosystem and economic services:
a. Filtering and degrading toxic wastes and pollutants
b. Reducing flooding and erosion
c. Helping to sustain stream flows
d. Recharge groundwater aquifers
e. Maintain biodiversity
f. Supplying valuable products
g. Providing recreation
e. 8-5: How Have Human Activities Affected Freshwater Ecosystems?
i. Disrupting and degrading many of the ecosystem and economic services provided
by freshwater rivers, lakes, and wetlands in four major ways:
1. Dams and canals restrict the flows of about 40% of the world’s 237 largest
rivers
a. This alters or destroys terrestrial and aquatic wildlife habitats along
these rivers, also lead to degraded coastal wetlands and greater
damage from coastal storms
2. Flood-control levees and dikes built along rivers disconnect the rivers from
their floodplains, destroy aquatic habitats, and alter or degrade the functions
of adjoining wetlands
3. Comes from cities and farms which add pollutants and excess plant nutrients
to streams, rivers, and lakes (cultural eutrophication)
4. Many inland wetlands have been drained or filled to grow crops or have been
covered with concrete, asphalt, and buildings