Download ch 8 aquatic biodiversity

 Coral
reefs form in clear, warm coastal
waters of the tropics and subtropics.
• Among the oldest, most diverse, and most
productive ecosystems.
• Formed by massive colonies of tiny animals
called polyps.
 Secrete crust of limestone (CaCO3) around their soft
bodies.
 Elaborate network of crevices, ledges, and holes.
• Symbiosis with Zooxanthellae, which live in the
tissues of polyps.

Coral reefs occupy
only 0.2% of the ocean
floor, but provide
important ecological
and economic
services.
• Moderate atmospheric
•
•
•
•
•
temperatures
Act as natural barriers
protecting coasts from
erosion (protect 15% of
world’s coastline)
Provide habitats
Support fishing and
tourism businesses
Provide jobs and
building materials
Studied and enjoyed

Degradation and
decline
• 15% of coral reefs
destroyed
• Another 20% damaged
by coastal development,
pollution, overfishing,
warmer oceans
• Coral bleaching
• Increasing ocean acidity
• Decline of coral reefs
should serve as a
warning about threats to
the health of the oceans,
which provide crucial
ecological and
economic sevices.
 Concept
8-1A Saltwater and freshwater
aquatic life zones cover almost three-fourths
of the earth’s surface with oceans
dominating the planet.
 Concept
8-1B The key factors determining
biodiversity in aquatic systems are
temperature, dissolved oxygen content,
availability of food and availability of light
and nutrients necessary for photosynthesis.
 Global
ocean is single continuous body
of water divided into four large areas.
• Atlantic
• Pacific
• Arctic
• Indian
 Freshwater
makes up less than 2.2% of
earth’s surface.
 Aquatic
equivalents of biomes are called
aquatic life zones.
• Distribution of many aquatic organisms is
determined in large part by the water’s salinity.
  aquatic life zones are classified into two major types:
 Saltwater, or marine (oceans, estuaries, coastal wetlands,
shorelines, coral reefs, and mangrove forests)
 Freshwater (lakes, rivers, streams, and inland wetlands)
 Aquatic
systems play vital roles in the
earth’s biological productivity, climate,
biogeochemical cycles, and biodiversity,
and they provide us with fish, shellfish,
minerals, recreation, transportation routes,
and many other economically important
goods and services.
 Major types of aquatic
• Plankton – drifters
 Phytoplankton
 Zooplankton
 Ultraplankton
organisms
 Photosynthetic bacteria may be responsible 70% of PP near
ocean surface
• Nekton – swimmers
• Benthos – bottom dwellers
• Decomposers

Key factors that determine the distribution of
organisms in an aquatic life zone
•
•
•
•

Temperature
Dissolved oxygen content
Availability of food
Availability of light and nutrients needed for photosynthesis in
the euphotic, or photic, zone
Depth of euphotic zone in lakes and oceans can be
reduced by turbidity – cloudiness caused by algal
blooms or excessive silt.
• Excessive nutrient loading – cultural eutrophication
• Clearing land causes erosion and silt with runoff


In shallow systems: open streams, lake edges, and
ocean shorelines, nutrients are usually available
In most areas of open ocean, nitrates, phosphates,
iron, and other nutrients are in short supply  limits
NPP.
 Concept
8-2 Saltwater ecosystems are
irreplaceable reservoirs of biodiversity
and provide major ecological and
economic services.
 Enormously
valuable ecological and
economic services: estimated at $12 trillion
annually (Figure 8-4)
 Oceans still poorly understood.
 Huge reservoirs of biodiversity
• Many ecosystem types
 Variety of species, genes, and biological and chemical
processes
 Important for sustaining life.
 Marine
life is found in three major life zones:
coastal, open sea, and ocean bottom (Figure
8-5).
 Coastal
zone
• Warm, nutrient rich, shallow water that extends
from the high-tide mark on land to the gently
sloping, shallow edge of the continental shelf.
• < 10% of world’s ocean area but contains 90% of
marine species
• Most commercial fisheries
• Most ecosystems—estuaries, coastal wetlands,
mangrove forests, and coral reefs—have high
NPP.
  ample supplies of sunlight and plant nutrients, which
come from land.

Life in these coastal ecosystems is harsh
• Significant daily and seasonal changes in
 Tidal and river flows, temperature, salinity and runoff of
pollutants such as eroded sediments and chemicals form
land.
• May be composed of only a few plant species that
can withstand rapidly changing environmental
factors, athough such species are highly productive.

Estuaries
• Where rivers meet the sea
• Partially enclosed bodies of water where sea water
mixes with freshwater as well as nutrients and
pollutants from streams, rivers, and runoff from land
(Figure 8-6).

Coastal wetlands
• Coastal land areas covered with water all or part of
the year
 River mouths, inlets, bays, sounds, salt marshes (Figure 8-7) in
temperate zones, and mangrove forests in tropical zones.
• Some of the earth’s most productive ecosystems 
high nutrient inputs, rapid circulation from tidal
flows, and ample sunlight penetrates shallow water.

Seagrass beds
• Another component of coastal marine biodiversity.
• 60 species of plants that grow in shallow marine and
estuarine areas along most continental shorelines.
• Support a variety of species
• Stabilize shorelines and reduce wave impacts.

Mangrove forests
• Magroves—69 tree species that can grow in salt water
(Figure 8-8)
• Tropical equivalent of salt marshes.
• 70% of gently sloping, sandy and silty coastlines in
tropical and subtropical regions.
• Provide important ecological and economic services




Maintain water quality
Food, habitat, and nursery sites for aquatic and terrestrial species
Reduce storm damage and coastal erosion
Historically, sustainably supplied timber and fuelwood to coastal
communities
• Between 1980 and 2005, and estimated 20% of mangrove
forests were lost mostly due to coastal development.
  polluted drinking water, salt water intrusion
  reduced protection from storms
  reduced biodiversity
 Moon
and sun cause ocean tides that rise
and fall every 6 hours
 Intertidal zone – the area of shoreline
between low and high tides.
• Organisms here are adapted to extreme
conditions: waves, varying water levels, varying
salinity
 Organism hold on to something, dig in, and/or hide in
protective shells
• Rocky shores (Figure 8-9, top)
 Pounded by waves
 Organisms occupy different niches in response to daily
and seasonal changes in temperature, water flows, and
salinity.
• Sandy shores or barrier beaches (Figure 8-9,
bottom)
 Support other types of organisms; most survive by
burrowing, digging, and tunneling in sand
 Shorebirds have specialized feeding niches (Figure 413, p. 93)
 Barrier Islands (Figure 8-10) – low, narrow, sandy islands
that form offshore, parallel to some coastlines.
 South Padre Island
 Undisturbed barrier beaches generally have one or
more rows of natural sand dunes in which the sand is
held in place by plant roots.
 First line of defense against storm surges and heavy wave
action from storms.
 Such areas are valuable for real estate development.
 Marine
equivalent of
tropical rain forests
 Habitats
for onefourth of all marine
species
Figure 8.11
Natural capital: some components and
interactions in a coral reef ecosystem.
 Open
sea is marked by a sharp increase in
depth at the edge of the continental shelf.
 Divided into three vertical zones based on
light penetration and temperature (Figure 85).
• Euphotic zone
 Brightly lit upper zone where phytoplankton carry out
some 40% of the world’s photosynthesis.
 Nutrient levels are low, except at upwellings.
 DO levels are high
 Large fast-swimming predatory fish: swordfish, sharks,
and bluefin tuna.
• Bathyal zone
 Dimly lit middle zone does not contain
photosynthesizing producers.
 Zooplankton and smaller fishes which migrate to feed at
the surface at night.
• Abyssal zone
 Dark and very cold, with little DO
 Abundant with life even though there is no
photosynthesis to support it.
 Marine snow
 Deposit feeders such as worms
 Filter feeders such as clams and sponges
• Avg. NPP per unit area is low, but make larger
overall contribution to earth’s overall NPP.
 NPP, higher at upwellings
 Concept
8-3 Human activities threaten
aquatic biodiversity and disrupt
ecological and economic services
provided by saltwater systems.
A
four year study by U.S. National Center
for Ecological Analysis and Synthesis
• Examined 17 different human activities
• 41% of the world’s oceans, heavily affected
• No area left completely untouched
 In
2006, 45% of world’s population lives
near the coast.
•  destruction and degradation of natural
resources and services (Figure 8-4).
• Projected to be 80% in 2040
 Major
threats to
marine systems
• Coastal development
• Overfishing
• Runoff of non-point
• Invasive species
source pollution:
fertilizers, pesticides
and livestock waste
• Point source pollution
such as sewage from
cruise ships and oil
tanker spills
• Habitat destruction
from coastal
development and
trawler fishing
• Human enhanced
climate change causing
sea level rise: destroys
coastal habitats, coastal
cities and coral reefs
• Climate change:
warming oceans and
decreasing pH
• Pollution and
degradation of coastal
wetlands and estuaries
Figure 8.13
Chesapeake Bay, the largest estuary in the United States, is severely degraded
as a result of water pollution from point and nonpoint sources in six states and
from the atmospheric deposition of air pollutants.
 Largest estuary in the US
• Polluted since 1960
•  Population increased significantly to 16.6
million in 2007
 The
estuary receives wastes from point
and nonpoint sources
• Bay has become a huge pollution sink; only 1% of
waste is flushed to the Atlantic Ocean
 Phosphate and nitrate levels too high
•  Large algal blooms and oxygen depletion
• 60% of phosphates come from point sources
• 60% of nitrates come from non-point sources
 Overfishing
of oysters, crabs, and
important fishes
• Combined with pollution and disease, has
caused populations to fall since 1960.
 1983, U.S.
Implemented the Chesapeake
Bay Program
• Integrated coastal management, including
citizens’ groups, communities, state legislatures,
and federal government
 Land-use regulations in six states to reduce ag and
urban runoff
 Banned phosphate detergents
 Closely monitoring industrial discharges
 Restoration of wetlands and sea grasses
 Native
oyster
problem
 Chesapeake Bay
Program has
achieved some
success
• Between 1985 and
2000
 Phosphorus, -27%
 Nitrogen, -16%
 Sea grasses coming back
 There
has been a
drop in federal
funding
 Concept
8-4 Freshwater ecosystems
provide major ecological and economic
services and are irreplaceable reservoirs
of biodiversity.
 Standing (lentic)
• Lakes
• Ponds
• Inland wetlands
 Flowing (lotic)
• Streams
• Rivers

bodies of freshwater
systems of freshwater
Cover only 2.2% of earth’s surface but
provide important ecological and economic
 Formation of lakes
• Large natural bodies of standing freshwater formed
when precipitation, runoff, streams or groundwater
fills depressions in the earth’s surface.
 Four
zones based on depth and distance
from shore
•
•
•
•
Littoral zone
Limnetic zone
Profundal zone
Benthic zone
Figure 8.16
The effect of nutrient enrichment on a lake. Crater Lake in the U.S. state of Oregon (left)
is an example of an oligotrophic lake that is low in nutrients. Because of the low density
of plankton, its water is quite clear. The lake on the right, found in western New York
State, is a eutrophic lake. Because of an excess of plant nutrients, its surface is covered
with mats of algae and cyanobacteria.
 Oligotrophic lakes
• Low levels of nutrients and low NPP
 Eutrophic lakes
• High levels of nutrients and high NPP
 Mesotrophic
 Cultural
lakes
eutrophication leads to
hypereutrophic lakes
 Surface
water
 Runoff
 Watershed, or
drainage basin – the land
area that delivers runoff, sediment, and
dissolved substances to a stream,
 Three
aquatic life zones in the downhill flow
of water
• Source zone
• Transition zone
• Floodplain zone
 Source zone
• Shallow, cold, clear, and swiftly flowing
• Large amounts of DO
• Lack nutrients, not very productive
• Nutrients come from organic matter that falls into
the river.
• Fauna: cold-water fishes and other animals
adapted for fast moving water.
• Flora: algae and mosses attached to rocks
 Transition Zone
• Headwater streams merge to form wider,
deeper, and warmer streams
• Slower flowing, less DO, and can be turbid
• Cool- and warm-water fishes, and more
producers.
 Flood
Plain Zone
• Steams join into wider and deeper rivers that
•
•
•
•
•
flow across broad flat valleys.
Water higher in temp, less DO
Producers such as algae, cyanobacteria, and
rooted aquatic plants along the shores.
Water, muddy and high concentration of
suspended particulate matter (silt).
Main channels support distinct fishes (carp,
catfish), backwaters support fish similar to lakes
At mouth of river, may divide into many channels
as it flows through the delta, built up by deposits
of silt, and coastal wetlands and estuaries.
Figure 8.18
Much of the U.S. city of New Orleans, Louisiana, was flooded by the storm surge
that accompanied Hurricane Katrina, which made landfall just east of the city on
August 29, 2005. When the surging water rushed through the Mississippi River
Gulf Outlet, a dredged waterway on the edge of the city, it breached a floodwall,
and parts of New Orleans were flooded with 2 meters (6.5 feet) of water within
a few minutes. Within a day, floodwaters reached a depth of 6 meters (nearly 20
feet) in some places; 80% of the city was under water at one point. The
hurricane killed more than 1,800 people, and caused more than $100 billion in
damages, making it the costliest and deadliest hurricane in the U.S. history. In
addition, a variety of toxic chemicals from flooded industrial and hazardous
waste sites, as well as oil and gasoline from more than 350,000 ruined cars and
other vehicles, were released into the stagnant floodwaters. After the water
receded, parts of New Orleans were covered with a thick oily sludge.
 Coastal
deltas, mangrove forests, and
coastal wetlands: natural protection against
storms
 Dams
and levees reduce sediments in
deltas: significance?
 New
Orleans, Louisiana, and Hurricane
Katrina: August 29, 2005
 Global
warming, sea rise, and New Orleans
 Inland
wetlands are lands covered with
freshwater all or part of the time
(excluding lakes, reservoirs, and
streams).
• Marshes, dominated by grasses and reeds
• Swamps, dominated by trees and shrubs
• Prairie potholes, carved out by ancient glaciers
• Floodplains
• Actic tundra
 Some
wetlands are permanent, some are
seasonal
 Wetlands are highly productive
 Habitat for game fishes, muskrats, otters,
beavers, migratory waterfowl, and many
other birds species.
 Ecological and economic services
• Filter and degrade toxic wastes
• Reduce flooding and erosion
• Help to replenish streams and recharge
groundwater aquifers
• Biodiversity
• Food and timber
• Recreation areas
 Concept
8-5 Human activities threaten
biodiversity and disrupt ecological and
economic services provided by
freshwater lakes, rivers, and wetlands.
 Human
activities affect freshwater
ecosystems in four major ways:
• Dams and canals
 Alter and destroy terrestrial and aquatic habitats
 Reduce water flow and sedimentation in coastal deltas and
estuaries.
• Flood control levees and dikes
 Disconnect rivers from their floodplains
 Destroy aquatic habitats
 Alter or reduce the function of wetlands
• Cities and farms add pollutants and excess nutrients
to streams and lakes
 Cultural eutrophication
• Draining or filling in wetlands
 More
than half of inland wetlands in
continental U.S. lost since 1600s
• 80% destroyed to grow crops
• 20% lost to mining, forestry, oil and gas
extraction, highways and urban development.
• Has caused increased flood and drought damage
in the U.S.
 Other
countries too
• For example, 80% of all wetlands in Germany
and France have been destroyed.