L4 - River Macroinvertebrates Flashcards
What are the defining features of lotic bodies?
Flow and turbulence
What is flow measured as?
Velocity in meters per second
Discharge in cubic meters per second
What is turbulence?
when water flows in irregular paths
* this happens more in lotic systems than lentic systems
Why do most streams and rivers have few planktonic organisms? And what is the exception to this?
Planktonic organisms get flushed away in lotic bodies.
Exception: very big, slow river have a few
What is the pelagic zone ‘limited’ to?
Strong swimmers - mainly vertebrates such as fish because anything else gets washed away.
‘Most stream organisms are attached or benthic’ - what does attached and benthic mean?
Attached = cling to hard surfaces or plants
Benthic = buried in soft sediments
Where do boundary layers form?
In flowing water
- Boundary layers also form when water flows across a fixed surface
→ Water flows more slowly close the surfaces of a stream bed
What creates a boundary layer around small organisms?
Viscosity of water
Explain how attached organisms take advantage of boundary layers
It’s easier to stop getting washing downstream if:
- you’re very flat
- you stay pressed against the stream bed surfaces
What is periphyton? (base of benthic/attached food web)
A complex mixture of algae, microbes, and detritus that grows on aquatic surfaces and sediments
*attached microbial communities
What are macrophytes? (base of benthic/attached food web)
aquatic plants + macroalgae
Explain the role of macroinvertebrates (second layer in a benthic/attached food web)
- grazers (the same role as zooplankton in pelagic food webs)
*but lots of intraguild predation ( also eat each other)
Which layer of the benthic/attached food web are vertebrate predators found?
Third layer e.g. fish
Where is the attached/benthic food web found in comparison to the pelagic food web?
attached/benthic food web - streams and rivers
pelagic food web - lakes and oceans
What are 2 adaptions of periphyton?
- a jelly-like matrix prevents dehydration and stores nutrients
- the community can function in and out of water - this is important for changing water levels
State the 4 functional groups of macroinvertebrates
Shredders
Collectors (filter-feeding & gatherers)
Grazers/scrapers
Predators
What are the 2 groups of collectors within lotic food webs?
Gathering/Gatherers
Filtering/Filterers
What are the characteristics of filtering collectors within lotic food webs?
- Capture and eat FPOM (Fine Particulate Organic Matter) from suspension
- Sloughed periphyton, faeces
- Diverse mechanisms for feeding
→ Black fly larvae sticky fans
What are the characteristics of gathering collectors within lotic food webs?
- Capture and eat FPOM (Fine Particulate Organic Matter) from substratum
- Sometimes called deposit feeders
- Sloughed periphyton, faeces
- Often in association with shredders (commensalism)
What are the characteristics of grazers/scrapers in the lotic food web?
- Graze on, and eat periphyton
- Scrape the surface with mouthparts
→ Snails: rasping radula
→ Insects: mandibles
What are the characteristics of Shedders in the lotic food web?
- Eat CPOM (coarse particulate organic matter) made of decaying leaves and macrophytes
- Many groups of insect larvae
- Conditioning increases palatability
- Microbes on the surface (periphyton)
→ help with decomposition
→ are like ”peanut butter on a cracker”
Where does CPOM (coarse particulate organic matter) come from?
CPOM is detritus that comes from terrestrial plants surrounding the stream. It is also covered in periphyton, which provides important additional nutrition to shedders
What are the characteristics of (macroinvertebrate) predators within the lotic food web?
- eat other macroinvertebrates
- Ambush versus hunting
→ Suspended prey
→ Damselfly larvae = ambush predators
What are the characteristics of vertebrate predators in lotic food webs?
- eat macroinvertebrates
How are streams classified?
Streams are classified by their order or Strahler number (bigger = bigger)
→ The Amazon is 12th order
→ 80% of streams and rivers are 1st or 2nd order
What is the river continuum concept (RCC)?
Describes the way the community composition and ecological function change along the length of a river as it increases in size/order
