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Remineralisation rates of sinking particles – K2
MP Gall, PW Boyd (NIWA)&
J Valdes (WHOI)
On VERTIGO we adopted 3 approaches to examining particleRemineralisation / Respiration
i) Shipboard MicrowinklerIncubations and ETS
ii) In situ respirationchambers
ii) In situ remineralisationof settling particles
Successful
A failureData on ETS and bacterial ecto-enzymes before endof 2006 (HOT data indicate bact assim. effic. of 10% or less
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 trapcylinders
A rotating ball design was employed to prevent swimmers enteringthe inner sanctum
Fill trap withwater from 200 mNO PRESERVATIVES
T=0
10 min
STOP
T=36 h T=72 h
DISSOLVED OXYGEN AND TEMPERATUREWAS MEASURED EVERY 10 MINUTES
Particles collected on upper surface of the ball once it stopped turning
The experiments
Three 72 h deployments 3 additional experimentsi) After deployment 3 the trap was placed in a tempControlled 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 (whichWas coated with settled particles). Their behaviour was Filmed – both with the ball in a stationary and in rotatingState.
iii) A serial addition experiment was conducted with Neocalanus spp. – using microwinkler flasks to estimateTheir respiration rates
Turley (1993) DSR I “linear decrease in rates ofLeucine and thymidine incorporation with increasingPressure” at 200 atm rates were 1/3 to ½ of those at 1 atm
K2 234 Th flux
In deployment 1the 234 Th flux for the36 h collection period was around 600 dpmm-2 d-1
Data courtesy of KEN BUESSELER
Deploy 1
Year day 2005
212.0 212.5 213.0 213.5 214.0
O2
(um
ol L
-1)
0
2
4
6
8
Export flux (as O2) = 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
HOWEVER……
We recovered 9 copepodsNeocalanus 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
Deploy 2
Year day 2005
223.2 223.6 224.0 224.4 224.8
O2
(um
ol L
-1)
0
2
4
6
8
A FURTHER TRAP DEPLOYMENTS YIELDED COMPARABLEOXYGEN CONSUMPTION RATES – despite a marked decrease inSurface PP, EP, but not in b
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 slowsinkers (<10 m to 400 m d-1)
150 m
Mixed layer 40 m
Fast sinkersCould be 600 m deeperIf it was not intercepted and remineralized in ourtrap
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