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Primary Production by Michael L. Murphy Presented by: Katy O’Donnell Introduction Primary production is the basic source of energy for a system and acts as the only significant energy gateway into earth ecosystems Aquatic Primary Producers Benthic Algae Macrophytes Phytoplankton Algae Aquatic Plants Allochthonous OM Light nutrients temperature streamflow herbivores Provide trophic support for invertebrates, fish and other animals in aquatic environments Benthic Algae Microscopic, unicellular algae Macroscopic Diatoms Green, Blue-Green, Red algaes Form thin layers on stream substrates 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 http://www.photomacrography.net/forum/userpix/1609_Oscillatoria_1_1.jpg http://www.biologie.uni-hamburg.de/bonline/library/webb/BOT311/Cyanobacteria/Cyanobacteria.htm Macrophytes Angiosperms Bryophytes Differentiated roots, leaves, and vascular tissue 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 aka Potamoplankton Centric diatoms Small green algae Restricted to slow moving streams and sloughs http://www.doctortee.com/dsu/tiftickjian/cse-img/botany/algae/diatom/centric-diatom http://www.pondsolutions.com/product_images/uploaded_images/pond-algae4.jpg 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 Light saturation food consumption > food production photooxidation Nutrients Diffusion, not supply CO2, Silica, Nitrogen, Phosphorous N:P ratios are indicative of the limiting nutrient Low N:P = N limits High N:P = P limits Grazers Dominate during low flow Alter algal structure Enhance nutrient supply Lethal factors: Temperature Turbidity Streambed scour Energy Flow how energy generated by primary producers is output to consumers Excretion of DOM Grazing of living tissue Collection of autochthonous detritus Primary production is a source for autochthonous & allochthonous OM Algae and plants will vary seasonally, which affects energy flow pathways Avenues of energy flow from producers 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?
