Primary Productionby Michael L. Murphy

Presented by: Katy O’Donnell

Introduction

Aquatic Primary ProducersBenthic AlgaeMacrophytesPhytoplankton

Lightnutrients

temperature streamflowherbivores

AlgaeAquatic PlantsAllochthonous 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 AlgaeFilamentous Green Algae

like UlothrixSpring & Early Summer

Green & Blue-Green Algaelike Oedogonium, Pectonema, Phormidium

Early Autumn

DiatomsWinter

http://www.photomacrography.net/forum/userpix/1609_Oscillatoria_1_1.jpg

http://www.biologie.uni-hamburg.de/b-online/library/webb/BOT311/Cyanobacteria/Cyanobacteria.htm

Macrophytes

AngiospermsDifferentiated roots, leaves,and vascular tissue

BryophytesMosses and liverworts

Four main growth habits:Emergent plants rooted below water level with aerial leavesFloating attached plants with submerged rootsFloating unattached plantsRooted submerged plants

More common in low-gradient streams with open canopies

Growth forms,long, clumped, free flowing filamentsShort 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 diatoms Small green algae

http://www.doctortee.com/dsu/tiftickjian/cse-img/botany/algae/diatom/centric-diatomhttp://www.pondsolutions.com/product_images/uploaded_images/pond-algae4.jpg

Primary Production

Photon energy from the sun drives primary productionThe energy is captured as chemical bond energy in plant’s pigments and is used for maintenance, growth, or stored.

Production is limited by:SunlightNutrientsGrazers

LimitationsLight! Compensation pointfood consumption > food production

Light saturationphotooxidation

Nutrients Diffusion, not supply

N:P ratios are indicative of the limiting nutrient

CO2, Silica, Nitrogen, Phosphorous

Low N:P = N limitsHigh N:P = P limits

Grazers

Lethal factors: TemperatureTurbidityStreambed scour

Dominate during low flowAlter algal structureEnhance nutrient supply

Energy Flowhow energy generated by primary producers is output to consumers

Primary production is a source for autochthonous & allochthonous OM

Excretion of DOMGrazing 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 PathwayStream 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 PathwayDominantly allochthonous and primary pathwayAutochthonous matter is still important

SloughingDislodgementScour

Primary methods of export

Export and retention time important Related to spiral length

Distribution of Primary ProductionPrimary production changes predictably downstream

Watershed UseTimber harvestLivestock grazingAgricultureUrban development

Affect primary production by altering: Riparian vegetation

Stream flowSediment

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?