Shallow lakes in the Netherlands Pristine state: Clear water Abundant - - PowerPoint PPT Presentation

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Shallow lakes in the Netherlands Pristine state: Clear water Abundant - - PowerPoint PPT Presentation

Mar 14, 2024 19 likes •116 views

Shallow lakes in the Netherlands Pristine state: Clear water Abundant submerged vegetation G Gradual increase in nutrient d l i i i loading from agricultural run off Sudden transition to turbid state characterized by S dd t iti t t bid

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SLIDE 1

Shallow lakes in the Netherlands Pristine state: Clear water Abundant submerged vegetation G d l i i i Gradual increase in nutrient loading from agricultural run‐off S dd t iti t t bid t t h t i d b Sudden transition to turbid state characterized by phytoplankton blooms, suspended sediment, little submerged vegetation submerged vegetation Decreases in nutrient loading unable to reverse

http://www.sparcs‐center.org/applications/ecology/lakes.html

g transition

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SLIDE 2

A possible explanation: Alternative stable states Alternative stable states Submerged vegetation promoted water clarity by: water clarity by:

  • reducing nutrients in water

column

  • providing habitat refuges for

grazing zooplankton

  • preventing sediment

resuspension

http://www.sparcs‐center.org/applications/ecology/lakes.html

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SLIDE 3

A possible explanation: Alternative stable states Alternative stable states Turbid state:

  • Lack of penetrating sunlight

Lack of penetrating sunlight prevents re‐establishment of submerged vegetation g g

  • Eutrophication, reduction in

zooplankton densities lead to h l k bl phytoplankton blooms

  • Benthic feeders (fish) stir up

sediment sediment

http://www.sparcs‐center.org/applications/ecology/lakes.html

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SLIDE 4

from Scheffer & Carpenter, TREE 2003

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SLIDE 5

from Scheffer et al, Nature 2001

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SLIDE 6

Alternative stable states

  • Slow, gradual changes in

environment cause sudden, unexpected changes in ecosystems (“tipping points”)

  • Changes are not easily reversed

(hysteresis) (hysteresis)

http://www.sparcs‐center.org/applications/ecology/lakes.html

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SLIDE 7

Alternative stable states

  • Lakes in the Netherlands: Water

clarity restored by reducing nutrient inputs and removing fish that were feeding in the benthos and on zooplankton and on zooplankton.

  • Other purported examples:

Other purported examples:

  • Woodlands vs grasslands in

terrestrial ecosystems

  • Desertification
  • Coral vs algal dominanted

t t i l f

http://www.sparcs‐center.org/applications/ecology/lakes.html

states in coral reefs

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SLIDE 8

Coral (C) Macroalgae (M) Turf (T) Photo credits P. Edmunds

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SLIDE 9

sea urchins, Diadema antillarum (massive die‐off in 1983) parrotfishes p grazing grazing Photo credits M. Chiappone, Wikipedia Macroalgae (M) Turf (T)