Primary Production by Michael L. Murphy Presented by: Katy O’Donnell

Introduction Aquatic Primary Producers Benthic Algae Macrophytes Phytoplankton Light nutrients temperature streamflow herbivores Algae Aquatic Plants Allochthonous OM Provide trophic support for invertebrates, fish and other animals in aquatic environments Primary production is the basic source of energy for a system and acts as the only significant energy gateway into earth ecosystems

Benthic Algae Microscopic, unicellular algae Diatoms Form thin layers on stream substrates Macroscopic Green, Blue-Green, Red algaes Grow as filaments, sheets, or mats

Benthic Algae Filamentous Green Algae like Ulothrix Spring & Early Summer Green & Blue-Green Algae like Oedogonium, Pectonema, Phormidium Early Autumn Diatoms Winter

online/library/webb/BOT311/Cyanobacteria/Cyanobacteria.htm

Macrophytes Angiosperms Differentiated roots, leaves, and vascular tissue Bryophytes Mosses and liverworts Four main growth habits: Emergent plants rooted below water level with aerial leaves Floating attached plants with submerged roots Floating unattached plants Rooted submerged plants More common in low-gradient streams with open canopies Growth forms, long, clumped, free flowing filaments Short filaments Mosses are perennial and take several years to accumulate Prefer more stable conditions and tend to be more abundant in fast moving streams

Phytoplankton Restricted to slow moving streams and sloughs aka Potamoplankton Centric diatomsSmall green algae

Primary Production Photon energy from the sun drives primary production The energy is captured as chemical bond energy in plant’s pigments and is used for maintenance, growth, or stored. Production is limited by: Sunlight Nutrients Grazers

Limitations Light ! Compensation point food consumption > food production Light saturation photooxidation Nutrients Diffusion, not supply N:P ratios are indicative of the limiting nutrient CO 2, Silica, Nitrogen, Phosphorous Low N:P = N limits High N:P = P limits Grazers Lethal factors: Temperature Turbidity Streambed scour Dominate during low flow Alter algal structure Enhance nutrient supply

Energy Flow how energy generated by primary producers is output to consumers Primary production is a source for autochthonous & allochthonous OM Excretion of DOM Grazing of living tissue Collection of autochthonous detritus Avenues of energy flow from producers Algae and plants will vary seasonally, which affects energy flow pathways

The Grazing Pathway Stream size and flow control abundance of grazers Relative abundance indicates their importance in a stream Spatial variation of current, light, and stream substrate can mask effects of grazing Aquatic plants and algae somewhat control the distribution, abundance, and growth of scrapers

The Detrital Pathway Dominantly allochthonous and primary pathway Autochthonous matter is still important Sloughing Dislodgement Scour Primary methods of export Export and retention time important Related to spiral length

Distribution of Primary Production Primary production changes predictably downstream

Watershed Use Timber harvest Livestock grazing Agriculture Urban development Affect primary production by altering: Riparian vegetation Stream flow Sediment Channel structure, etc

Question The author discusses limiting factors for primary production. Based on the, text, how do you suppose these factors change throughout the day? How do they change seasonally? How do changes in these factors affect organisms?