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Aquatic Ecology


Two Major Types of Aquatic Life Zones Saltwater or marine Estuaries, coastlines, coral reefs, coastal marshes, mangrove swamps, and oceans Freshwater Lakes and ponds ... – PowerPoint PPT presentation

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Title: Aquatic Ecology

Aquatic Ecology
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
  • 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
  • Secondary consumers that feed on other
  • 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
  • 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

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

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
  • 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 earths 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
  • 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

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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

Narrow littoral zone
Little shore vegetation
Low concentration of nutrients and plankton
Sparse fish population
Limnetic zone
Sleepily sloping shorelines
Profundal zone
Sand, gravel, rock bottom
Oligotrophic lake
Wide littoral zone
Much shore vegetation
High concentration of nutrients and plankton
Dense fish population
Limnetic zone
Gently sloping shorelines
Figure 7-21Page 158
Profundal zone
Silt, sand, clay bottom
Eutrophic lake
  • 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

  • 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

  • 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

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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
  • Bogs and fens waterlogged peaty areas

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