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