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Benthic microbes – organismsBenthic microbes organisms and ecology
Helmut HillebrandPlankton Ecology Group
ICBM
Lecture aims
At the end of this lecture students are At the end of this lecture, students are supposed to Know basic features of benthic microbial
organisms Understand substratum – organism
interactions Understand the basic interactions between
bacteria, protists and microalgae
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Lecture structure
The players: microbial eukaryotes in the The players: microbial eukaryotes in the benthos
The game board: substratum as a determinant of microbial life
The game: interactions between The game: interactions between organisms in the benthos
Synthesis
Players: autotrophic eukaryotes
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Taxonomic overview
Cyanobacteria Cyanobacteria Prokaryotes Freshwater &
marine Unicells,
filaments, colonies
Partly N2-fixing: heterocysts
Taxonomic overview
Rhodophyta Rhodophyta Marine Filaments,
crusts and thalli
Crustose algae highly important in reef development
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Taxonomic overview
Heterokontophy Heterokontophyta: Chrysophyta Flagellated Unicells,
pelagic, few fcolony forming
benthic Marine and
Freshwater
Taxonomic overview
Bacillariophyta Bacillariophyta Freshwater &
marine Silicate frustule,
partly with raphe
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Taxonomic overview
Valve organization and colony formation Valve organization and colony formation in diatoms
Taxonomic overview
MOBILE
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Taxonomic overview Phaeophyta Phaeophyta
Marine, thalli Habitat forming species in many
coastal ecosystems (Fucus, kelp)
Taxonomic overview Chlorophyta Chlorophyta
Freshwater & marine Unicells, filaments, colonies,
thalli
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Players: heterotrophic eukaryotes
Players: heterotrophic eukaryotes
Amoeba Amoeba Flagellates
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Players: heterotrophic eukaryotes
Cili t Ciliates
Players: heterotrophic eukaryotes
Meiofauna Meiofauna Rotifers Nematodes Copepods Ostracods
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Game board: Sediment
Sediment picture Sediment picture
Some sediment constraints Sediments are Sediments are
inherently instable Underwood &
Paterson 1995: Diatoms enhance sediment stability by EPS production
C l ti b t Correlation between Chlorophyll and EPS in sediments
Photographs: Low diatom and high diatom sediment, with EPS coating
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Some sediment constraints
Kühl & Kühl & Jörgensen 1992: Vertical profile of light and phtosynthesis in a 3mm sediment core
Some sediment constraints
Hüttel et Hüttel et al. 1996: Sediment-Topography alters fluid and particle i t iintrusion into the water column
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Some sediment constraints
Bioturbation Bioturbation
Players in the sediment
Hatched meiofaunaHatched meiofaunaBlack bacteriaWhite algae
Upper 5mm sediment biota: Sundbäck et al.
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Players in the sediment
Microbial mats Microbial mats
Game board: Hard substrates
Periphyton Periphyton
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Some hard substrate constraints
Benthic boundary layer Benthic boundary layer
Some hard substrate constraints
Burkholder et al Burkholder et al. 1990: Uptake of P by adnate algae (AD) is only a fraction of loosely attached algae (LA) at control and P-enriched site
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Some hard substrate constraints
Architecture and biofilms Architecture and biofilms
Some hard substrate constraints
Succession Succession
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light
physical forcing
Players on hard substrates
periphyton
phytoplankton
macrophytesnutrients
competition
grazing
grazers
substratum
internal processes
nutrient regeneration
Players on hard substrates
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Games – case studies
Interactions: Interactions: Competition Grazing Nutrient recycling Mixotrophyp y
Game 1: competition between autotrophs on sediments
Competition between cyanobacteria and Competition between cyanobacteria and diatoms on sediments of different grain size and at different temperatures
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Game 1: competition between autotrophs on sediments
Game 2: Trophic interactions in sediments
Esptein et al. Esptein et al. 1997, Microbial Ecology. Trophic interactions in sedmient microbial food webs
S l tt Seasonal patterns of algae and bacteria as well as consumption on algae and bacteria
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Esptein et al.
Game 2: Trophic interactions in sediments
Esptein et al. 1997, Microbial Ecology. Trophic interactions in sedmient microbial food webs
S l tt
Ciliates
Seasonal patterns of algae and bacteria as well as consumption on algae and bacteria
Game 3: Multiple stressors in sediment communities
Addition ofAddition of nutrients and antifouling agent CPT had only small effects on microbenthic communities, systemssystems remained autotroph, recovery was rapid
Sundbäck et al. 2007, MEPS Low Nutrient High nutrient
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Game 4: Nutrient and grazing effects on epilithic algae
closed cages open cages uncaged control plots
4 replicates for each factor combination
NPKnutrient addition in two (ambient, enriched) or four (no, low, mid, high) categories
Game 4: Nutrient and grazing effects on epilithic algae
0.08
0.1
m3/
cm2)
High nutrient uptake - high grazing riskANOVA:
Graz***;
0
0.02
0.04
0.06
no low med high
nutrient treatment
Alg
al b
iovo
lum
e (m Nut***;
GxN+
Hillebrand et al. 2000, MEPS
Positive effects of nutrients, negative effects of grazing
Higher grazing effects with higher nutrient supply
“Trade-off” between algal growth types (nutrient uptake vs. grazing resistance)
Low grazing risk - low nutrient
availability
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Game 5: Microbial food webs on hard substrates
Game 5: Increased DOC supply
increased total periphytonincreased total periphyton biomass in almost all experiments, whereas increased P supply incresed total biomass only if algae were present.
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Game 5: The effects of DOC and P on the ratio of heterotrophic to autotrophic The effects of DOC and P on the ratio of heterotrophic to autotrophic
abundance strongly depended on trophic structure, where additional resources enhanced the autotroph component when the basal heterotrophs were limited by low organic C or by strong consumer pressure.
Game 5:
Purely heterotrophic biofilms had higher C:P ratios than autotrophic assemblages. Increased P-supply decreased periphyton C:P throughout except for the experiment with the highest trophic complexity, as including more elements of the
b l f d b l d h hmicrobial food web led to higher retention of P within the assemblage.
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Game 6: Periphyton biomass and stoichiometry
Exp 2: Factorial combination of 3Exp 1: 3 grazer treatments at low ambient nutrient concentrations (N-limited)
Sampling at day 0, 2, 4, 8, 15, 23
control
Theodoxus
Exp 2: Factorial combination of 3 grazer- and 2 light-manipulations (P-
limited)
Sampling at day
0, 4, 15
+ Lightcontrol
Theodoxus
Bythinia
Theodoxus
Bythinia
0, 4, 15
+++ Light
Game 6: Periphyton biomass and stoichiometry
Algae: strong reduction already after 2-4 days; Reduction in CONHeterotrophs (not shown):Bacteria: strong reduction after 8 d, no change in CONCiliates: strong reduction after 8dMeiofauna: reduction after 8-15 d, increase in Con0 1
0.2
0.3
0.4
biov
olum
e (m
m3 c
m-2
) Control Bithynia Theodoxus
increase in Con
Hillebrand, Burgmer, de Montpellier, Liess, Reiss, Wickham
Time (d)
0 4 8 12 16 20 240.0
0.1
Alg
al
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Algae: strong reduction already after 0.4
Game 6: Periphyton biomass and stoichiometry
2-4 days; Reduction in CONHeterotrophs (not shown):Bacteria: strong reduction after 8 d, no change in CONCiliates: strong reduction after 8dMeiofauna: reduction after 8-15 d, increase in Con
0.1
0.2
0.3
Alg
al b
iovo
lum
e (m
m3 c
m-2
) Control Bithynia Theodoxus
Hillebrand, Burgmer, de Montpellier, Liess, Reiss, Wickham
Time (d)
0 4 8 12 16 20 240.0
Temporal uncoupling of response to grazer presence Increasing heterotrophy in CON with time
N-Limitation indicatedC:N Theodoxus << Bithynia; C:P Theodoxus < Bithynia
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Game 6: Periphyton biomass and stoichiometry
8
10
12
14
16
18
C:N
mol
ar r
atio
• Grazer presence increased periphyton N
• Significant effects of BIT, not THE, on C:N
• Bithynia also increased DIN
Time (d)
0 4 8 12 16 20 244
6
8
Control Bithynia Theodoxus
ANOVA: graz + graz X time **
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P-Limitation indicatedC:N Theodoxus << Bithynia; C:P Theodoxus < Bithynia
Game 6: Periphyton biomass and stoichiometry
400
600
800
1000
C:P
mol
ar r
atio
start con bit the
• Both grazers increase periphyton P significantly
start HL4 HL15 LL4 LL15
Sampling
200
ANOVA: graz *** light ** graz X light ns
P-Limitation indicatedC:N Theodoxus << Bithynia; C:P Theodoxus < Bithynia
Game 6: Periphyton biomass and stoichiometry
400
600
800
1000
C:P
mol
ar r
atio
start con bit the
• Both grazers increase periphyton P significantly
• Low light increases periphyton P (and N) - relative release from nutrient limitation
start HL4 HL15 LL4 LL15
Sampling
200
ANOVA: graz *** light ** graz X light ns
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P-Limitation indicatedC:N Theodoxus << Bithynia; C:P Theodoxus < Bithynia
Game 6: Periphyton biomass and stoichiometry
400
600
800
1000
C:P
mol
ar r
atio
start con bit the
• Both grazers increase periphyton P significantly
• Low light increases periphyton P (and N) - relative release from nutrient limitation
• significant effects of Bithynia, not Theodoxus on C:Nstart HL4 HL15 LL4 LL15
Sampling
200
ANOVA: graz *** light ** graz X light ns
Game 7: Mixotrophy in the benthos
Mixotroph abundance in men
t darklight
2x105
Mixotroph abundance in sediments of Kiel Bight - increases in the dark - only <5% of total abundance
September October
abun
dan
ces
/ cm
³ se
dim
0
1x105
Station 3
gella
tes
80
100
sediment depth (mm)
0-3 3-6 6-9
% to
tal n
anof
lag
0
20
40
60
Moorthi, PhD thesis
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Game 7: Mixotrophy in the benthos
Proportion es 12
September, GemanyMarch, CaliforniaJuly, Greenland Sea
Proportion of mixotrophs increase with salinity
0 10 20 30 40 50
ates
7
8
0 10 20 30 40 50
% to
tal n
anof
lage
llate
(mea
n +
SE
)
0
2
4
6
8
10
12sediment (+brine) light sediment, dark
plankton light l kt d k
r=0.70, p<0.01, N=48 r=0.70, p<0.01, N=48
salinity (psu)
0 10 20 30 40 50
% to
tal n
anof
lage
lla(m
ean
+ S
E)
1
2
3
4
5
6
7
salinity (psu)
0 10 20 30 40 50
plankton, light plankton, dark
r=0.68, p<0.01, N=30 r=0.64, p<0.01, N=30
Moorthi, PhD thesis
Summary
Benthic Benthic eukryotic miroorganisms encompass a majority of phylogenetic groups