Transcript Stream Biotic and Abiotic

Chapter 1.3
Stream Biology
 There are 3 dominant groups of organisms in most
stream communities.
 Algae and Animal like protists
 Invertebrates
 Vertebrates
• Algae
•Are plantlike protists that make their own food autotrophs)
•Since they are autotrophs it forms the base of most aquatic food chains.
•Freshwater Alage use sunlight and dissolved nutrients in a stream to
make their food.
(
•Animal-like protists
•Has many characteristics as animals
•Are aquatic organisms that eat:
•Bacteria
•Sediments that contain bacteria
•Algae
•Ex. Ameoba, Euglena
 Amoeba
 Are protists that engulf food by flowing around and over it
 Raptors
 Protists that eat other protist
 Saprotrophs
 Protists that feed on decayed organic material
 Invertebrates
 Do not have an internal skeleton made of bone
 Examples of freshwater invertebrates
 Insects, worms, mollusks
 Shredders & striders
Mollusk
strider
Mollusk
 Vertebrates
 Has an internal skeleton made of bone
 Examples of freshwater Vertebrates
 amphibians (frogs, salamanders)
 fish
Factors that affect Freshwater ecosystems
 Stream order
 Smaller streams ( 1st order) flow into larger streams (2nd
order) and continue on. Two streams of the same
order must come together for a stream to move up
in order.
 The size or order of the stream relates directly on the
organisms that are in the ecosystem.
 1st order streams are home to large insect populations, few if
any fish.
 Plants and game fish dominate 3rd & 4th order.
 Larger the stream the more diverse populations of algae, fish,
and other aquatic organisms.
Factors that affect Freshwater ecosystems
 Temperature
 Change in temp affects the kinds and #’s of species in a
stream.
 Some species can live in a wide range of temps (catfish and
carp), while others species can survive only in certain temps
(algae, protists and trout).
 Examples of factors that causes difference in stream temp
 Velocity
 Depth
 Seasonal change
 Riparian coverage
Factors that affect Freshwater ecosystems
 Current
 Unidirectional
 Causes different forces on organisms in the stream
 Velocity
 Change in distance over time.
 Fish are unaffected by velocity, while insects are generally
limited to calmer water.
 Waters moves the fastest in the middle of the stream
below the surface.
 Substrate
 Is the material that organisms live in, on, or around.
 EX. of Organic substrate – algae, plants, mosses
 EX. of Inorganic substrate – rocks, sand, silt and mud
Factors that affect Freshwater ecosystems
 Sunlight (plants rely on it to make food thru photosynthesis)
 Less sunlight = less organisms
 Turbidity (clarity)
 Reflects the amount of suspended matter in water
 Facts that affect turbidity
 Increase in stream erosion
 Increase in water volume
 Heavy rain/melting snow
Factors that affect Freshwater ecosystems
 Dissolved Gases
 Oxygen and Carbon dioxide
 Oxygen
 Enters the water from the air
 Concentration depends mainly on temp
 As temp increases, D.O. decreases
 Photosynthesis also adds oxygen to the water
 Current
 As current decreases, so does D.O.
Factors that affect Freshwater ecosystems
 Organic Matter




Mostly used for food
Algae and detritus (particulate organic matter)
Too few nutrients = loss of organisms
Too many can cause mass algal blooms and then loss of
other organisms
 pH
 Scale ranges 0-14, 7 neutral, below 7 acidic, above 7 basic
 Rainwater tends to be slightly acidic
 Mine drainage is a major contributor to stream
acidification