Seasonal shifts in microzooplankton grazing in the UK Shelf Sea

Transcription

1 Seasonal shifts in microzooplankton grazing in the UK Shelf Sea Sari Giering, Seona Wells, Kyle Mayers Glen Tarran, Louise Cornwell, Elaine Fileman Angus Atkinson, Dan Mayor

2 Shelf Seas - ~5% of the global ocean area - support 15-35% of global primary productivity - provide ~90% of the global fish catches

3 SSB Model (ERSEM) PO4 / NH4/ DOM Phyto Zoo Bact Coccollith. Diatoms Flagellates Pico-fl. CO2 < 20 µm µm > 200 µm POM

4 Focus of this talk What? (1) Growth of pico & nanoplankton ( and 2-20 µm) (2) Grazing by microplankton (20-63 µm) When and where? In the Celtic Sea (a) during Spring and Summer (b) in two depth strata

5 CCS Apr 2015: 5x Jul 2015: 3x Central Celtic Sea (CCS) site

6 Growth and grazing by µ-zoo: Dilution technique Series of seawater diluted with filtered (0.2 µm) sea water. 4-Point dilution Data analysis very time-intensive (Chlorophyll a, cell counts) 100% 70% 40% 20% (% unfiltered sea water)

7 Apparent growth rate (d -1 ) Dilution technique Synechococcus 15 Apr 2015 y = -0.67x R² = Fraction unfiltered seawater intercept (k) is the phytoplankton growth rate (d -1 ) slope (g) is mortality rate of phytoplankton due to grazing (d -1 ) Landry & Hassett (1982), Landry et al. (1995)

8 Cell counts Nano- & picoplankton ( µm) Flowcytometry on board 1. Synechococcus 2. Picoeukaryote phytoplankton 3. Nanoeukaryote phytoplankton 4. Coccolithophores 5. Cryptophytes Microplankton (10 63 µm) FlowCam at PML (Plymouth, UK) 1. Ciliates 2. Flagellates 3. Diatoms 4. Dinoflagellates Pennate Diatoms Flagellates 92% of diatoms (cell counts)

9 Cell counts Nano- & picoplankton ( µm) Flowcytometry on board 1. Synechococcus 2. Picoeukaryote phytoplankton 3. Nanoeukaryote phytoplankton 4. Coccolithophores 5. Cryptophytes Microplankton (10 63 µm) FlowCam at PML (Plymouth, UK) 1. Ciliates 2. Flagellates 3. Diatoms 4. Dinoflagellates Pennate Diatoms Growth & grazing Flagellates 92% of diatoms (cell counts)

10 Cell counts Nano- & picoplankton ( µm) Microplankton (10 63 µm) Flowcytometry on board Kyle Mayers Does microzooplankton grazing 1. Synechococcus FlowCam at PML (Plymouth, UK) 1. Ciliates 2. Picoeukaryote phytoplankton 2. Flagellates influence the Kyle fate Mayers of 3. Nanoeukaryote phytoplankton 3. Diatoms 4. Coccolithophores coccolithophores? Does microzooplankton grazing 4. Dinoflagellates influence the fate of coccolithophores? 5. Cryptophytes Session 5, Poster 303 Session 5, Poster 303 Pennate Diatoms Growth & grazing Flagellates 92% of diatoms (cell counts)

11 Depth (m) Depth (m) Chlorophyll profiles April 0 Nitrate + Nitrite (µm) Apr 11-Apr 15-Apr

12 Depth (m) Depth (m) Chlorophyll profiles April July CTD Fluorescence µm Nitrate

13 Depth (m) Depth (m) Chlorophyll profiles April July CTD Fluorescence shallow 25 shallow 50 DCM 75 deep µm Nitrate

14 Depth (m) Depth (m) Expectations April July CTD Fluorescence High biomass Large phyto High growth Increasing grazing NO 3 shallow shallow DCM Low biomass No growth Low grazing deep

15 Depth (m) Depth (m) Expectations April July High biomass Large phyto High growth Increasing grazing NO 3 shallow CTD Fluorescence Low biomass Small cells Low growth NO 3 Low grazing High biomass High growth Moderate grazing shallow DCM Low biomass No growth Low grazing deep

16 What was there? Biomass based on initial samples

17 Shallow Pico/nano biomass mg C m

18 mg C m -3 Rel. biomass Shallow Pico/nano biomass

19 Shallow Pico/nano biomass Deep mg C m -3 Rel. biomass mg C m -3 mg C m m DCM

20 Shallow Pico/nano biomass Deep mg C m -3 Rel. biomass Rel. biomass mg C m -3 mg C m m DCM

21 Rel. abundance mg C m Shallow Micro biomass

22 Rel. abundance Rel. abundance Micro biomass Shallow Deep mg C m -3 mg C m m DCM

23 Growth and grazing rates of pico/nano plankton Based on dilution series

24 Deep growth & graz. Shallow growth & graz. Growth/grazing (d -1 ) growth grazing Synecho. Picoeuk. Nanoeuk. 100 m

25 Deep growth & graz. Shallow growth & graz. 0 1 Growth/grazing (d -1 ) growth grazing Synecho. Picoeuk. Nanoeuk. 100 m

26 Deep growth & graz. 0 1 Shallow growth & graz. 0 1 Growth/grazing (d -1 ) growth grazing Synecho. Picoeuk. Nanoeuk. 100 m

27 Deep growth & graz. 0 1 Shallow growth & graz. 0 1 Growth/grazing (d -1 ) growth grazing Synecho. Picoeuk. Nanoeuk. DCM

28 Depth (m) Depth (m) Expectations April July High biomass Small Large phyto High growth Increasing grazing NO 3 shallow CTD Fluorescence Low biomass Small cells High Low growth NO 3 High Low grazing High biomass High growth Moderate grazing shallow DCM Low biomass No growth Low grazing deep

29 Primary production at CCS April July

30 Primary production at CCS April July

31 Primary production at CCS April July Recycled production NO 3 New production

32 Biomass in July Shallow DCM mg C m -3 mg C m mg C m -3 mg C m pico/ nano micro mg C m m

33 Mesozooplankton? Mesozoo Microzoo Phyto

34 A big thank you to the amazing teams during cruises DY029 & DY033! NERC for funding

35 Mesozooplankton Day and night time nets Three size-fractions: µm µm 3. >500 µm Depth horizons: 1. above thermocline 2. deep chlorophyll maximum (DCM; in July only) below thermocline

36 Food removal experiments T µm µm >500 µm Controls