Chapter 1.3 Stream Biology

There are 3 dominant groups of organisms in most stream communities. Algae and Animal like protists Invertebrates Vertebrates

Are plantlike protists that make their own food (autotrophs) 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 Ex. Ameoba, Euglena

Amoeba Raptors Saprotrophs 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