Lecture 5- macroinvertebrates and the river continuum concept

Question 1

How is macro invertebrate sensitivity scored?

Answer 1

-on a scale of 0-12.5

Question 2

how are macroinvertebrate fucntional groups scored?

Answer 2

on feeding habits

Question 3

what are the macro invertebrate functional groups? (four)

Answer 3

• shredders
• collectors
• scrapers
• predators

Question 4

what is periphyton, what does it contain and how does it form? how does it protect?

Answer 4

• periphyton is a microbial biofilm, containing the microbial loop. it is essentially a jelly like matrix that attaches to a surface. this jelly is produced by bacteria and algae
• periphyton is 99% water, which provides organisms in it protection from dehydration when changes in water level occur

Question 5

what are the three forms of macroinvertebrate food?

Answer 5

• fine particulate organic matter (microbes+zooplankton)
• coarse particulate organic matter
• periphyton

Question 6

Describe shredders(what they eat etc)

Answer 6

• shredders feed of CPOM, such as decayed leaves and aquatic plants
• snails and crustaceans are the main shredder groups

Question 7

why do shredders have to wait for leaf decay? what do they wait for?

Answer 7

• leaves are essentially “too hard” for macronivertebrates to consume
• so they must wait for a biofilm of microbes to cover them, and once this biofilm begins breaking the leaf down the macroinvertebrates can eat them

Question 8

what are the two groups of collectors?

Answer 8

-filterfeeders and gatherers

Question 9

what do filter feeders utilise?

Answer 9

• fine particulate organic matter

- acquire it from suspension via filter feeding

Question 10

how do gatherers acquire fpom?

Answer 10

• gather its from SUBSTRATUM (sediment associated larva)
• also called deposit feeders
• feed of sloughed periphyton and feces

Question 11

what do scrapers feed off? how do they acquire it?

Answer 11

• feed off periphyton via scraping food off the surface

- scrape surface with mouthpart. Eg. Rasping Radula of snails

Question 12

what do predators feed on? what are the two types of prey?

Answer 12

• feed on other macroinvertebrates via ambushing or overhunting
• feed on suspended (eg. caddisfly) or attached prey

Question 13

what do predators feed on when small vs large?

Answer 13

-commonly feed on perihpyton when small and macroinvertebrates when large

Question 14

what does the river continuum concept describe?

Answer 14

-describes the way macro invertebrate distribution changes along a river as it increases in size

Question 15

what do rivers start in?

Answer 15

-headwater streams

Question 16

what dominates 1-3 order streams?

Answer 16

• the initial inputs of energy are CPOM from vegetation that lines the catchment
• the dominant benthic invertebrates in headwater streams are COLLECTORS (collecting fpom) and SHREDDERS (breaking down cpom)
• most fish require cool,well oxygenated water

Question 17

what dominates 4-6 order streams?

Answer 17

• less cpom due to it being broken down by upstream shredders
• greater area for PERIPHYTON PRODUCTION which increase the quantity of scrapers
• collectors also present, filter feeding on broken down fpom coming from upstream
• larger river means warmer waters with less oxygen. Fish must tolerate this

Question 18

what dominates 6th order and onwards streams?

Answer 18

• large planktonic food web due to large river size
• collectors+filterfeeders dominate
• warmer conditions and even less oxygen for fish to cope with
• large zooplnakton population may also be sustained, feeding off upstream fpom

Question 19

how is the river continuum concept applied to the real world?

Answer 19

the RCC represents an ideal river with zero pollution. Organic polution in the real world will change macroinvertebrate distribution, so comparing the real to this ideal can allow for understanding of the extend of pollution effects.

Question 20

what is the difference between allochthonous and autochthonous inputs?

Answer 20

• autochontous inputs are those produced via primary production in the river
• allochontous are organic, external inputs (eg. leaves that fall in)

Question 21

what are the two variations in DOC in rivers?

Answer 21

• LABILE. meaning substances are easily decomposed and taken up by micro organisms
• REFRACTORY, meaning substances are left over and transported downstream

Question 22

what happens to doc and cpm as you move downstream?

Answer 22

-decrease in doc diversity, increase in cpom importance

Question 23

what is the functional group distribution as you progress up stream orders?

Answer 23

Low order streams: more shredders and collectors due to cpom dominance
Intermediate order streams: scraper and collector dominated
High order streams: collector and filter feeder dominated

Question 24

describe the water framework directive

Answer 24

-was created in 2000 by the EU, focusing on the integrated assessment and management of all
EU rivers
-applies to: rivers, lakes, estuaries, coastal water, groundwater

Question 25

what did the water framework directive aim to achieve? how did it go about this?

Answer 25

-maintain and restore ecosystem health, by reaching “good ecological and chemical status” of all water bodies by 2015
the directive had a “no deterioration policy for involved fining countries that polluted clear rivers”

Question 26

what were the advantages of using macroinvertebrate diversity to assess waterquality in the water framework directive?

Answer 26

• cheap and easy

- taxonomy well sorted and common species response known

Question 27

what were the disadvantages of the water framework directive?

Answer 27

• only measures macroinvertebrate response to organic pollution
• seasonal variability complicates comparability
• some groups (eg. segmented worms) are taxonomically difficult to identify

Question 28

what are the three filters on the ability of species to settle in a habitat?

Answer 28

• climate regime
• geochemistry of catchment (often a result of underlying bedrock)
• shoreline vegetation (impacts the amount of entering cpom)