The annual routine of a predatory Arctic chaetognath in a highly seasonal environment

Presented by Jordan Grigor (Takuvik, Université Laval) At the Arctic Frontiers Conference on Friday 25th January 2013 Co-authors: Janne Søreide (UNIS), Øystein Varpe (Akvaplan-niva, UNIS)

Chaetognaths: most abundant invertebrate predators (King 1979) and comprise 5-15% of global biomass

Calanus Ctenophores C. hyperboreus: 7.2-8.0mm (adult ♀) Mertensia ovum: up to 100mm

Pteropods Chaetognaths Clione limacina: 10-25mm elegans: 20-60mm Parasagitta Eukrohnia elegans hamata

P. elegans

Pseudosagitta maxima

...the epipelagic P. elegans often dominates communitiesReproduced of chaetognaths from Dvoretsky in (2011) the high- Arctic (Dunbar 1962, Welch et al. 1996) Model of the planktonic food web in the Amundsen Gulf

Adapted from “Other zooplankton” Forest et al. (2011) - includes chaetognaths Arrow widths represent the importance of carbon flow between the connected food web components. “The tigers of the ” (Suthers et al. 2009) P. elegans prey: mostly copepods

Prey items in the gut of Parasagitta elegans in the Barents Sea in May/June 1983 (reproduced from Falkenhaug 1991)

(mm) P. elegans: vertical migration

 Changes in the vertical distribution of plankton can be due to passive processes or migration  Types of vertical migration: - diel (DVM), seasonal (SVM), ontogenetic (OVM)  Various advantages of migrating - may vary depending on needs Depth (m)

Diel verticalSeasonal migration vertical distributionof Parasagitta of Parasagitta elegans in the elegans western at Station North PacificP in the on subarctic July 22-23, Pacific 1971 . (March 1980-January 1981). Wider bars at a given depth, signify more individuals. Reproduced from Terazaki (2004) Annual routine

 The timing of Arctic zooplankton life-cycle events is closely linked to seasonality in food availability and predation risk  The term “annual routines” has been used to summarise the timetable of these events during the course of a year (McNamara & Houston 2008, Varpe 2012) A year-round study in Arctic Norway (July 2008-June 2009) Sampling...

Nets:WP3(1m2 opening, 1mm mesh size) WP2 (0.26m2 opening, 0.2mm mesh size) MPS (0.26m2 opening, 0.2mm mesh size) Environmental conditions in Billefjorden Size cohorts

In most months, e.g. in October... there were 3 clear cohorts:

• Cohort 0 (0 years+) lengths1.9mm-14.3mm

• Cohort 1 (1 year+) Density Probability lengths 13.0mm-29.7mm

• 0.00 0.02 0.04 0.06 0.08 Cohort 2 (2 years+) 0 1020304050 Length (mm) lengths 29.2mm-34.2mm Normal Mixture October: MPS & WP3 samples Total of 401 individuals measured Abundances throughout the year...

350

300

) 250 -2

200

150

100 Cohort 2 Abundance (ind m Abundance (ind Cohort 1 50 Cohort 0 0 MJ JASONDJ FMA Following cohorts throughout their lives...

45

40 Cohort 1 35

30 Cohort 0

25 Cohort 2 20

15

10 Mean body length (mm) Mean body length 5 LIFESPAN IS AT LEAST 3 YEARS 0 MJ JASONDJ FMAMJ JASONDJ FMAMJ JASONDJ FMA This growth is linked to the phyto bloom... Growth is linked to the phyto bloom...

Fluorescence (gl-1)

13th-17th June 2009

Reproduction too... Stained sperm in tail

Seminal receptacles Seminal vesicles

Long, swollen ovaries

A 30mm specimen in May InvestigatingInvestigating migration migration...SVD: Cohort 1

Seasonal vertical distribution (SVD): Cohort 0

SVD: Cohort 2 InvestigatingInvestigating migrationmigration – P. elegans hatchlings probably prey on small Calanus copepods

Seasonal vertical distribution (SVD): Cohort 0 Seasonal vertical distribution: Cohort 0 Stage 1 C. gl ac Stage 2 C. glac Depths (m)

Depth distribution of early

) 400 -2 C. glacialis life stages in the fjord ) -2 300 during summer 2008 (reproduced 200 from Bailey 2010) 100 Cohort 0 Abundance (ind m

Abundance (ind m 0 MJ J ASOND J FMA P. elegans gut contents... An almost intact Calanus inside the gut of P. elegans. A rare sight!!! A pteropod?

Another Calanus slightly further along in the digestion process... Conclusions from the study...

 Three size cohorts of P. elegans were present in the fjord year-round  Reproduction / Cohort 0 emergence took place in summer  Most length growth in all cohorts also took place in summer  Cohort 0 appear to be feeding in surface waters in July, but more data are needed...

TAKE HOME MESSAGE: TIMING OF REPRODUCTION, EMERGENCE, GROWTH AND MIGRATION ARE SPECIAL ADAPTATIONS TO USE THE Acknowledgements

The authors wish to thank the following individuals/groups for their help and support during the study:

Louis Fortier Takuvik Joint International Laboratory Québec-Océan and Laval intern students Stig-Falk Petersen Jago Wallenschus Other UNIS students and staff involved in the Ice Edge Programme Thanks for listening! Please feel free to ask me any questions!