Lecture 9 - Stream Enrichment Flashcards
What are the primary limiting macronutrients in freshwater and which is more common to control? (3)
Nitrogen and phosphorus
Phosphorus is the most common to control because N2 is available in the gaseous cycle
What are the 4 techniques to assess nutrient limitation in streams?
- Bioassay analysis
- Synoptic surveys
- Low-level water chemistry analysis
- Qualitative assessment
What is bioassay analysis? (5)
Analysis of concentrations of nutrients
Involved conducting in-situ testing
Various concentrations of N and P are added to determine seasonal limitation of nutrients
The “gold standard” of testing
Expensive and time consuming = rarely done
What are synoptic surveys? (3)
When you compare biomass and macroinvertebrate composition across several streams and develop reference biomass and density
Field collection of benthic invertebrates either by the scientific method or a standardized form (CABIN)
Expensive and time consuming, especially the analysis
What is low-level water chemistry analysis? (4)
In streams, P is limiting when:
SRP (soluble reactive phosphorus) < 1ug/L or
TDP (total dissolved phosphorus)
< 2-3ug/L or
N is limiting when:
DIN (dissolved inorganic nitrogen)
< 20 ug/L
Relatively cheap, takes 1-2 weeks for results
What is a qualitative assessment of nutrients? (2)
Can determine a rough level of nutrients by how slippery the stream substrates are
Must do one of the other assessment techniques before actually proceeding with nutrient enrichment
What are the fractions of natural phosphorus in water? (6)
- Soluble Reactive Phosphorus (SRP)
- Soluble Unreactive Phosphorus (SUP)
- Particulate Phosphorus (PP)
- Total Phosphorus (TP)
TDP = SRP + SUP TP = PP + SRP + SUP
Soluble Reactive Phosphorus (4)
Can be filtered through 0.45 micron mesh
Consists largely of the inorganic orthophosphate (PO4-3) form of phosphorus
Taken up directly by algae = highly bioavailable
Concentration of fraction constitutes a good index of the amount of phosphorus immediately available for algal growth
Soluble Unreactive Phosphorus (SUP) (4)
Contains filterable phosphorus forms that do not readily react with the reagents in the SRP test
It is measured as the difference between TDP and SRP
Compounds in the SUP fraction are organic forms of phosphorus and chains of inorganic phosphorus molecules
Slowly becomes bioavailable (second best)
Particulate Phosphorus (PP) (3)
All material, inorganic and organic, particulate and colloidal, that was captured on the 0.45 micron mesh filter
May contain everything from bacteria to algae to clay, zooplankton, plant material etc.
Not bioavailable
Total Phosphorus (TP) (3)
Total of all filterable (<0.45 micron mesh) and particulate (>0.45 micron mesh) phosphorus forms
Most often analyzed fraction of phosphorus (not necessarily the best)
Not bioavailable
What is periphyton? (2)
A complex mixture of algae, Cyanobacteria, heterotrophic microbes, and detritus that is attached to submerged surfaces in aquatic ecosystems
Does not include aquatic plants
How does periphyton respond to low level additions of P and N? (2)
Periphyton are very sensitive to very low concentrations of bioavailable P and N
It has a highly efficient nutrient uptake mechanism for limiting nutrients (P and N)
How do aquatic invertebrate grazers respond to nutrients?
Algae spikes near the enrichment site (and decreases downstream) in the second year and decreases with each additional nutrient addition due to insect grazers catching up by year 3
What is the Stream Continuum Concept? (3)
Relates changes in stream communities and processes to the downstream gradient of abiotic factors like stream width, shading by trees, stream gradient, and water velocity
Streams don’t just transport materials, they also process materials as the biota take up, use, convert, and release nutrients and carbon
Describes the relative importance of autochthonous and allochthonous energy sources
Autochthonous materials
Biological communities are supported by and based on the photosynthetic production of organic matter produced within a community
Allochthonous materials
Biological communities are supported by and based on the photosynthetic production of organic matter derived from an external source
What are the 2 main changes that occur in the ratio of autotrophic production within the stream to heterotrophic respiration? (3)
- P/R is <1 in headwaters where production in the stream (autochthonous) is less than the total needed for respiration (this lack of production is subsidized by the input of allochthonous materials
P/R is > 1 in wider rivers where in-stream production is greater than the total needed for respiration (excess carbon is moved downstream)
P/R < 1 again in very large rivers
- There is also a change in the relative importance of various functional feeding groups of macroinvertebrates (shredders -> scrapers -> collectors)
What is nutrient spiraling? (3)
The unidirectional flow of water displaces nutrients considerable distances downstream
Spiraling distance increases with stream size (eg. 5km in Keogh River, 35km in Nechako. River)
It is difficult to measure precisely, but can use radioisotopes (not likely going to happen)
What are the 3 components of nutrient spiraling, and which is dominant?
Transport *dominant
Uptake
Release
Nitrogen limitation (4)
Varies seasonally and spatially
Can be masked by point and non-point source pollution
It is possible to shift from a P limited to N limited situation
N is limiting when DIN < 20 ug/L
What are the ecological responses to an N limitation? (2)
System could:
Show a reduction in rates of algae, periphyton, and bacteria
Show an appearance of blue-green algae (Cyanobacteria)c which can obtain nitrogen from the air via nitrogen fixation (nutritionally deficient, toxic, undesirable)
Nitrogen fixation in Cyanobacteria (2)
Reaction is performed by prokaryotic bacteria using an enzyme called nitrogenase
Occurs is specialized cells called heterocysts in Cyanobacteria
Cyanobacteria toxins (5)
Fall into 3 categories:
Hepatotoxins (attack the liver)
Neurotoxins (attack the nervous system)
Irritation (skin problems)
Usually released into water when cells rupture and die
Microcystin (type of Cyanobacteria) is now classified as a carcinogen by Health Canada
