WP8 Impact on trophic interactions

Two main foci:

1) The: C:N:P stoichiometry - food quality - TEP production – bacterial DOC consumption – algal/bacterial nutrient competition –– set of interactions.

2) Grazing vs viral lysis. Particularly for Ehux.

Idealized food web model

Thingstad et al. , J.Mar.Syst. 2007Higher pCO2 increases the C:N (and C:P? ratio)

What are the food web consequences of this?

Does it matter whether bacteria are C or N(P,Fe) limited?

Is the phyoplankton community structure important for the competitive balance between phytoplankton and bacteria (flagellates, Phaeocystis, small vs large diatoms…)?

Biodiversity aspect:Coexistence on one resource maintained by size-

selective predation

Thingstad et al. , J.Mar.Syst. 2007

Same principle at higher level of resolution: Coexistence maintained by species-specific viral lysis

Flag-ellate

#1

Flag-ellate

#2

Ehux

Ciliates

Virus #1

Virus #2

EhV

Size-class (small flagellates) abundance controlled by size-selective predation.

Species abundance controlled by lytic viruses.

Fate of coccoliths different depending on whether predation or lysis is dominating?

”Up” the food chain

”Down” to DOM

WP 8 partner involved 1.1 L

OV

2 UiB

3 IFM

13 NIO

Z

24 SO

TO

NImpact on trophic interactionsTask

number

Quantify the effects of acidification on predator-mediated mortality of autotrophic and heterotrophic microorganisms in the pelagic mesocosms studies Focus 1 & Focus 2

T8.1X X X X  

Quantify the consequences of changes in prey quality (e.g. C:nutrient ratios as expected in task 8.1) for herbivorous predators in microcosms Focus 1

T8.2X X X    

Quantify the consequences of changes in the bioavailability of algal exudates (as expected in task 8.1), also including indirect effects due to TEP enhanced cell aggregation, for predatory control by grazing and viral lysis in microcosms Focus 1 & Focus 2

T8.3

X X      

Determine the quantitative importance of coccoliths in reducing mortality due to predation and viral infection Focus 2 T8.4

X X   X X

Task 8.1 Quantify the effects of acidification on predator-mediated mortality of autotrophic and heterotrophic microorganisms in the pelagic mesocosms studies

8.1 2008 2009 2010 2011 2012

Month: 0-3 4-6 7-9 10-12

11-15

16-18

19-21

22-24

25-27

28-30

31-33

33-36

37-39

40-42

43-45

43-48

LOV Impact on grazing & viral lysis

UiB

IFM Impact of mesozoopl on phyto & micro

NIOZ Estimate viral lysis & microzoopalnkton grazing

SOTON

Microcosms and mesocosms, time not specified

D8.4 Datasets on predatory effects from pelagic mesocosm experiments (month 42; O, PP)

Participate in mesocosms

Task 8.2 Quantify the consequences of changes in prey quality (e.g. C:nutrient ratios as expected in task 8.1) for herbivorous predators in microcosms

2008 2009 2010 2011 2012

0-3 4-6 7-9 10-12

11-15

16-18

19-21

22-24

25-27

28-30

31-33

33-36

37-39

40-42

43-45

43-48

LOV

UiB

IFM Food quality effects on development/ egg production

NIOZ

SOTON

Mesocosms; 5 CO2-levels gradient design

D8.3 Dataset on food quality effects on predators in pelagic microcosms (month 36; O, PP)

Task 8.3 Quantify the consequences of changes in the bioavailability of algal exudates (as expected in task 8.1), also including indirect effects due to TEP enhanced cell aggregation, for predatory control by grazing and viral lysis in microcosms

2008 2009 2010 2011 2012

0-3 4-6

7-9

10-12 11-15 16-

18

19-

21

22-

24

25-

27

28-

30

31-

33

33-

36

37-

39

40-

42

43-

45

43-

48

LOV Effects on TEP formation & aggregation

UiB Food web consequences of increased C:nutrient stoichiometry

IPY meso-cosm Ny Ålesund

EPOCA mesocosm NÅ

MERCLIM cruise Svalbard

IFM

NIOZ

SOTON

Microcosms

D8.2 Dataset on ocean acidification effects on algal exudation and its consequences (month 36; O, PP)

Task 8.4 Determine the quantitative importance of coccoliths in reducing mortality due to predation and viral infection

8.4 2008 2009 2010 2011 2012

0-3 4-6 7-9 10-12

11-15

16-18

19-21

22-24

25-27

28-30

31-33

33-36

37-39

40-42

43-45

43-48

LOV

UiB

IFM

NIOZ Lytic virus growth cycle studies

SOTON

effect on omega calcite and on the proteomics signatures of coccolithophores . Also: molecular PhD student

Lab experiments

D8.1 Tipping point/risk assessment of ocean acidification effects on viral infection and predation on calcifying algae. Linking observations of calcification and performance (WP4 and WP6) to trophic interactions (WP8) (month 36; R, PU)

Microcosms; pCO2, light and trace metal controlled, time not specified

Deliverable (without associated task)

D 8.5 Improved model description(s) relating direct OA effects on organisms to properties of the lower pelagic food web linking WP8 to WP9 (month 36; O, PP)

UiB will, in project MERCLIM (R.Bellerby), have a PhD student looking at how to incorporate microbiology into the Barents Sea model of D. Slagstad

Associated projects:

SOTON: PhD student: in silico assessment of putative coccolithophore calcification genes, monitor the expression of selected candidate genes under low and high CO2 conditions representative of the modern ocean and future climate scenarios, and use confocal microscopy to assess sub-cellular localization of gene products.

UiB: Acidification and viruses. PhD student Cátia Carreira (Vigo). 6 months

exchange stipend from Norwegian Research Council.

UIB: MERCLIM (R.Bellerby); Norwegian Research Council. Arctic ecosystem studies.

UiB: PAME-Nor. Microbial consumption of DOC in Arctic waters.

DELIVERABLES

WP 8 partnerinvolved 1

.1 L

OV

2 U

iB

3 IF

M

13

NIO

Z

24

SO

TO

N

 Impact on trophic interactions

Deliverablenumber

Tipping point/risk assessment of ocean acidification effects on viral infection and predation on calcifying algae. Linking observations of calcification and performance (WP4 and WP6) to trophic interactions (WP8) (month 36; R, PU)

D8.1

X X   X X

Dataset on ocean acidification effects on algal exudation and its consequences (month 36; O, PP)

D8.2X X      

Dataset on food quality effects on predators in pelagic microcosms (month 36; O, PP)

D8.3X X X    

Datasets on predatory effects from pelagic mesocosm experiments (month 42; O, PP)

D8.4X X X X  

Improved model description(s) relating direct OA effects on organisms to properties of the lower pelagic food web linking WP8 to WP9 (month 36; O, PP)

D8.5X X X X X