1. Remineralisation rates of sinking particles – K2 MP Gall, PW Boyd (NIWA) & J Valdes (WHOI)

2. On VERTIGO we adopted 3 approaches to examining particle Remineralisation / Respiration i)Shipboard Microwinkler Incubations and ETS ii) In situ respiration chambers ii) In situ remineralisation of settling particles Successful A failure Data on ETS and bacterial ecto-enzymes before end of 2006 (HOT data indicate bact assim. effic. of 10% or less

3. Methodology (i) A DO sensor was deployed within the ‘inner sanctum’ of the sediment trap Our cylinder was deployed at 150 m depth along with other CLAP and ball trap cylinders A rotating ball design was employed to prevent swimmers entering the inner sanctum

4. Fill trap with water from 200 m NO PRESERVATIVES T=0 10 min STOP T=36 hT=72 h DISSOLVED OXYGEN AND TEMPERATURE WAS MEASURED EVERY 10 MINUTES

5. Particles collected on upper surface of the ball once it stopped turning

6. The experiments Three 72 h deployments 3 additional experiments i)After deployment 3 the trap was placed in a temp Controlled lab at atmospheric pressure and the Remineralisation signature was followed for a further 36 h ii) The video nasty – acclimated Neocalanus spp. Were added to the water overlying the ball valve (which Was coated with settled particles). Their behaviour was Filmed – both with the ball in a stationary and in rotating State. iii) A serial addition experiment was conducted with Neocalanus spp. – using microwinkler flasks to estimate Their respiration rates

7. Turley (1993) DSR I “linear decrease in rates of Leucine and thymidine incorporation with increasing Pressure” at 200 atm rates were 1/3 to ½ of those at 1 atm

8. K2 234 Th flux In deployment 1 the 234 Th flux for the 36 h collection period was around 600 dpm m -2 d -1 Data courtesy of KEN BUESSELER

9. Export flux (as O 2 ) = 74.29 umol L -1 This equals 6.2/74.3 is 8% over 36 h 6.1 umol L -1 over 36 h OXYGEN CONSUMPTION DUE TO PARTICLE REMINERALISATION

10. HOWEVER…… We recovered 9 copepods Neocalanus cristatus from the inner sanctum at the end of the deployment We set up a video of these animals at ambient temperature on the upper side of a ‘particle laden’ ball. It was clearly evident that they could ride the ball and access the innner sanctum

11. A FURTHER TRAP DEPLOYMENTS YIELDED COMPARABLE OXYGEN CONSUMPTION RATES – despite a marked decrease in Surface PP, EP, but not in b

12. WHAT DO THE DATA TELL US? Export flux (expressed as O2) = 74.29 umol L -1 over 36 h At 150 m So remineralisation equals 6.2/74.3 i.e. 8% over 36 h However, the particles that remineralised are a complex mixture of fast and slow sinkers (<10 m to 400 m d-1) 150 m Mixed layer 40 m Fast sinkers Could be 600 m deeper If it was not intercepted and remineralized in our trap