Aquatic Ecology - Alabama School of Fine Arts
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Transcript Aquatic Ecology - Alabama School of Fine Arts
Two Major Types of Aquatic Life Zones
Saltwater or marine
Estuaries, coastlines, coral
reefs, coastal marshes,
mangrove swamps, and
oceans
Freshwater
Lakes and ponds, streams
and rivers, and inland
wetlands
Determining Factor:
Salinity
Major Types of Organisms
Phytoplankton – plant plankton
Free-floating microscopic
cyanobacteria and algae
The producers and the basis of the
food chain
Zooplankton – animal plankton
Nonphotosynthetic herbivores that
feed on phytoplankton
Secondary consumers that feed on
other zooplankton
Range from single-celled protozoa to
large invertebrates such as jellyfish.
Larger Organisms
Nekton
Fish, turtles, and whales
Benthos
Bottom-dwellers – barnacles
& oysters that anchor to one
spot
Worms – burrow into sand
or mud
Lobsters and crabs – walk on
the bottom
Some are filter-feeders
Decomposers
Bacteria that break down
organic compounds
Key Characteristics of Aquatic Organisms
Less pronounced and fixed physical boundaries;
therefore difficult to count and manage populations
More complex and longer food chains
More difficult to monitor and study because of their
size and they are hidden from view
Limiting Factors
Aquatic life zones are divided
into three layers – surface,
middle, and bottom
Factors are:
Temperature
Access to sunlight for
photosynthesis
Dissolved oxygen (DO) content
Availability of nutrients such as
carbon (CO2), nitrogen (NO3),
and phosphorus (PO4) for
producers
Dissolved Oxygen
Photosynthesis can take place only as deep as light
can penetrate (euphotic zone)
Oxygen gets in from photosynthesis and diffusion
for air and is removed by aerobic respiration
(includes decomposition)
O2 can vary greatly in aquatic ecosystems
Most aquatic organisms cannot survive below 5 ppm of
DO
DO and CO2 concentrations vary with depth
Saltwater Life Zones
Coastal Zone
Warm, nutrient-rich,
shallow water that extends
from the high tide mark to
the margin of the
continental shelf
Makes up less than 10% of
ocean but contains 90% of
all marine species and is
especially important to
commercial fisheries.
Gets:
Sunlight and nutrients
Other Coastal Ecosystems
Estuaries – a partially enclosed area where
seawater mixes with fresh water
An ecotone
Coastal Wetlands – covered by water all or part of
the year
river mouths, inlets, bays, sounds, mangrove swamps,
and salt marshes
Temperature and salinity vary widely
Tides, seasonal variation in water flow, unpredictable
flows after heavy rains and floods
VERY PRODUCTIVE AREAS!
Other Coastal Ecosystems
Intertidal zone – area of shoreline between high and low tides
Very stressful zone for organisms:
Wave stress
Immersed during high tides and dry during low tides
Changing levels of salinity
Organisms usually cling to something, dig or hide in shells.
What are Barrier Islands?
Barrier Islands
Long, thin, low offshore
islands of sedement that
generally run parallel to
shore
Help protect mainland
Constantly shift
Coral reefs
Form in clear, warm, coastal waters in tropics and
subtropics
Have many types of organisms
Attached – corals, algae, and sponges
Fishes
Small organisms that bore into or attach themselves to coral
Easily damaged, grow slowly, can survive only in clear,
shallow, warm water
Have been harmed by global warming
They face many threats from pollution and other human
activities.
Open Sea
Beyond the continental
shelf
Euphotic zone: lighted
upper area
Photosynthesis
Low nutrient levels
High DO
Bathyl zone: dimly lit
middle zone
No photosynthesis
Abyssal zone: dark lower
zone
Very cold
Little DO
Many nutrients
Some Open Sea Organisms
Deposit feeders
Take mud into their
bodies and extract
nutrients from it
Filter feeders
Pass water through or
over their bodies and
extract nutrients from it
Average primary
productivity & NPP are
low.
Freshwater Life Zones
Found where water with a dissolved salt
concentration of less than 1% by volume either
accumulates or flows through the surfaces of
terrestrial biomes.
Standing water – lakes, ponds, inland wetlands
Flowing water – streams and rivers
Covers less than 1% of the earth’s surface but
ecologically and economically important
Are very closely connected to terrestrial biomes
due to nutrient run-off
Life zones
Ponds – shallow – light often penetrates to the
bottom – usually have only one zone
Lakes – deeper – generally consist of four zones –
defined by depth and distance from shore
Littoral zone – shallow water near shore where rooted
plants grow
Limnetic zone – open sunlit water away from shore – as
deep as sunlight penetrates
Profundal zone – deep open water that receives no
sunlight – cool so although oxygen is low, some fish live
here.
Benthic zone – bottom of lake – cool temperatures and
low oxygen
Characteristics of Freshwater
Surface water forms when precipitation that does not
sink into the ground or evaporate becomes run-off
Watershed – the land area that delivers run-off,
sediment, and dissolved substances to a stream.
Streams join together to form rivers
Rivers flow downhill to the ocean
Freshwater Systems
Ecological Services
Economic Services
• Climate moderation
• Food
• Nutrient cycling
• Drinking water
• Waste treatment
and dilution
• Irrigation water
• Hydroelectricity
• Flood control
• Groundwater
recharge
• Transportation
corridors
• Recreation
• Habitats for aquatic
and terrestrial
species
• Genetic resources
and biodiversity
• Scientific
information
• Employment
Eutrophication – Natural Aging of a
Lake
Classify lakes according to
nutrient content and
primary productivity
OLIGOTROPHIC LAKE –
low nutrients
Geographically young
Deep
Blue in color
Colder
Low populations of
phytoplankton
More desirable fish – bass
and trout
Low NPP
Eutrophication – Natural Aging
of a Lake
EUTROPHIC LAKE –
many nutrients
Old lake
Shallow
Green or brown in color
(algae)
Warmer
Algal blooms are common
Less desirable types of fish
– catfish, carp
High NPP
Sunlight
Narrow
littoral
zone
Little
shore
vegetation
Low concentration of
nutrients and plankton
Sparse fish
population
Limnetic
zone
Profundal
zone
Sleepily
sloping
shorelines
Sand, gravel,
rock bottom
Oligotrophic lake
Sunlight
Wide
littoral
zone
Much
shore
vegetation
High concentration of
nutrients and plankton
Limnetic
zone
Profundal
zone
Eutrophic lake
Dense fish
population
Gently
sloping
shorelines
Silt, sand,
clay bottom
Figur
SEASONAL CHANGES IN LAKES
Occurs in temperate lake
Makes use of the property of water that it is less dense
as a solid (0oC) then it is at a liquid (4oC);therefore ice
floats on water.
This causes THERMAL STRATIFICATION of deep
lakes
Summer
Lakes have three distinct layers:
EPILIMNION – upper layer of warm water high levels of DO
THERMOCLINE – layer where the temperature changes with
depth – usually 1oC/meter increase in depth – moderate oxygen –
during summer acts as a barrier between epilimnion and
hypolimnion
HYPOLIMNION – bottom layer of cold, dense water – low DO
To keep cool fish would be at the bottom but low DO there
Fall Overturn
Water begins to cool, becomes more dense and sinks
to the bottom
The thermocline disappears
Water mixes – nutrients are carried to the top and
oxygen to the bottom. Fish can be found at all depths
Winter
Lake separates into layers again due to difference in
density.
Warmest (4oC)water is at the bottom
Thermocline is reversed
Coldest water is at the top and freezes forming ice
which insulates and protects the lake.
Spring Overturn
Water begins to warm up
Wind blows causing vertical currents
Lake overturns again bring nutrients to the top and
oxygen to the bottom
Other Freshwater Biomes
Inland wetlands – land covered with water all or part
of the year located away from the ocean
Marshes – have a few trees
Swamps –dominated by trees and shrubs
Prairie potholes – depressions formed by glaciers
Floodplains – receive water during heavy rains or floods
Bogs and fens – waterlogged peaty areas