Microzooplankton matter: the importance of

smaller organisms in marine food webs

Xabier IrigoienDavid Montagnes*Dave Wilson

Tom AndersonRussell Davidson Dan Mayor

Claudia CastellaniRoger Harris

*primary author, School of Biological Sciences, University of Liverpool, BioSciencesBuilding, Crown Street, Liverpool, UK, L69 7ZB, dmontag@liv.ac.uk S

Note, the data in this presentation, by the authors listed on the title, slide have not been published. If you wish to use any of it, please contact David Montagnes, and he will direct you to the appropriate contributor(s) for permission. Images in this presentation are our originals, have been used with permission, or have been substantially modified.

PhytoplanktonPhytoplankton

Provided by the SeaWiFS Project, NASA/Goddard Space Flight Center and ORBIMAGE

Large> 5 µm

Small< 5 µm

Phytoplankton

Food web from a large perspectiveFood web from a large perspective

Mesozooplankton(copepods)

Mesozooplankton(copepods)

Food web from a small perspectiveFood web from a small perspective

MicrozooplanktonMicrozooplankton

FlagellatesFlagellates

CiliatesCiliates

microzooplankton

mesozooplankton

phytoplanktonmesozooplankton

planktivorous fish

piscivorous fish

fishers

Provided by the SeaWiFS Project, NASA/Goddard Space Flight Center and ORBIMAGE

SpringSummer

Four pronged approachQuantify microzooplankton

abundance, biodiversity, biomass, and production

Quantify phytoplankton as food for microzooplankton

Assess copepod grazingimpact on microzooplankton

Model the impact of microzooplankton

courtesy of

Are microzooplankton important?

Ciliate analysis by Dave Wilson and David Montagnes

First they were identified using this site: http://www.liv.ac.uk/ciliate/

~50 ciliate species

Relative total abundance

Strombidium sp

One dominant species

Myrionecta rubra

Another dominant species

Microzooplankton are important

Ciliate analysis by Dave Wilson and David Montagnes

The previous slides were just examples, but our data indicate this to be so

Are small phytoplankton important?

Phytoplankton by Dave Wilson

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4

Total < 10 µm< 5 µm

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4

Surface

Chl Max

Deep

Spring Summer

Chlorophyll a (µg L-1)

(n =26) (n =27)

and Russell Davidson

Small phytoplankton are important

The < 5 µm size fraction can be >50% of the biomass

Do copepods eat microzooplankton?

Ciliate biomass ( µg C L-1)

0 5 10 15 20 25

Inge

stio

n ( µ

g C

fem

ale-1

day

-1)

0.00

0.01

0.02

0.03

0.04

0.05

0.06

I = 0.055 x Cb10 + Cb

Grazing on ciliates by Oithona sp. in the Irminger basin by Claudia Castellani et al.

Ciliate biomass (µg C L-1)0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0In

gest

ion

(µg

C fe

mal

e-1 d

ay-1

)

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0 x CbI =3.8 + Cb

Grazing on ciliates by Calanus finmarchicusin the Reykjanes ridge by Dan Mayor et al.

Copepods do eat microzooplanktonNot only do copepods eat microzooplankton, we can quantify this response

Food web from a large & small perspectiveFood web from a large & small perspective

The food web is complex!

“traditional”foodchain

microbialloop

DOM

small phytoplanktonmicrozooplankton

bacteria

nutrients

large phytoplankton large zooplankton

exportexport

Modelling work by Tom Anderson