Question

QUESTIONS OF THE DAY

• Diagram a typical stream food chain. Be sure to highlight the autochthonous and allochthonous pathways, as well as the importance of FPOM.
• Describe the processes that break down CPOM into DOM and FPOM. What role do microbes (bacteria and fungi) and macroinvertebrates play in the breakdown of CPOM?
• List the 5 macroinvertebrate functional feeding groups/guilds discussed in class. What does each primarily consume (e.g., periphyton/algae, CPOM, FPOM, other organisms).  Be able to list 1-2 dominant families in each group.
• Which functional feeding group(s) tend to be dominant within stream systems? (hint: what is the dominant carbon source in stream food systems?)
• What are 3 major characteristics of stream food webs?
• Describe the trophic cascade from Power et al. 1985.
• Describe the trophic cascade from Power 1990.
• What 2 things control the ability of a predator to induce trophic cascades?
• What 5 things make trophic cascades rare in streams?

Answer 1

Answer 1:-

DATE ae Particulate Dissolved Organic Matter ol aase Particulabe Crganic Mlater CoroN) Allschthonoun eaves Micnhe DOM Poducen EPOM Shredder Collectors, Predaton Pr e d ata Cinvertebrates) Autochthonau)

Answer 2:-

1) Coarse particulate organic matter is broken down into fine particulate organic matter by following Allochthonous mechanism which is subdivided into three steps.

• In step one, leaching occurs from the CPOM that is associated with release of soluble contents by means of leaching.
• In step two, there occurs colonization by microbes. Many benthic invertebrates if we consider example of an organic source being added to a stream, these microbes and invertebrates covers up the plant tissue. This results in increase in palatability ( accessibility ).
• In step three, there occurs detrivore breakdown by means of the decomposers. There occurs loss of around 25% and final output in Fine particulate Organic Matter (FPOM).
• Temperature and pH plays a vital role in the process.

2) Coarse Particulate organic matter is converted to DOM (Dissolved organic matter) more specifically by leaching process and the leached DOM along with CPOM may lead to formation of conditioned CPOM and DOM along with CO2 output. Finally Conditioned CPOM will be processed biological and abiotic fragmentation processes to form FPOM and DOM along with CO2. This follows a serial mechanism.

Microbes in this case can belong to either Shredder, Filterer-collector, Collector-gatheror, Grazer and Predator. They have specialized roles. For example, the shredders including the ones belonging to Trichoptera, are dependent upon non-woody CPOM and the method of fragmentation is chewing and mining.

Answer 3:-

1) Shredder

• Include the families of Trichoptera, Crustacea, Plecoptera, etc.
• Food resource include non-woddy CPOM like leaves.
• Feeding type is chewing and mining.

2) Gouger

• Include the families of Diptera and Coleoptera.
• Food resources include woody plants and microbiota usually the superficial layers.
• Feeding type is chewing and mining.

3) Filterer-collector

• Includes Trichoptera, Similar, some Dipterans and Ephemeropterans.
• Food resources include FPOM and microbiota along with small autotroph in the water column.
• Feeding mechanism include collecting particles via setae which acts as a filtering apparatus.

4) Collector-Gatherer

• Include Ephemeroptera, Chironomidae and other related families.
• Food resources include FPOM and microbiota along with biofilms.
• Feeding mechanism include collecting surface deposits, browsing on amorphous materials and burrowing in soft sediments.

5) Grazer

• Include Ephemeroptera, Coleoptera and Diptera.
• Food resources include Periphyton and mostly diatoms and biofilms.
• Feeding mechanism is scraping and rasping.