benthic microbes – organisms and ecology … · plankton ecology group icbm lecture aims at the...

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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


Amoeba Amoeba Flagellates

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Cili t Ciliates


Meiofauna Meiofauna Rotifers Nematodes Copepods Ostracods

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Players: mixotrophs

Game board

Sediment Hard substrateSediment Hard substrate

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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


Hüttel et Hüttel et al. 1996: Sediment-Topography alters fluid and particle i t iintrusion into the water column

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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


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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Architecture and biofilms Architecture and biofilms


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


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


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

18


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


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



400

600

800

1000

C:P

mol

ar r

atio

start con bit the


• Low light increases periphyton P (and N) - relative release from nutrient limitation

start HL4 HL15 LL4 LL15

Sampling

200


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400

600

800

1000

C:P

mol

ar r

atio

start con bit the


• 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


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

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Summary

Benthic eukryotic Benthic eukryotic miroorganisms interact by important direct (feeding, competition) and indirect (nutrient regeneration) interactions.

benthic microbes – organisms and ecology … · plankton ecology group icbm lecture aims at the...

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