Transcript Primary Production by Michael L. Murphy

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?