VERSITET Mustafa Mantikci, Stiig Markager, Jørgen Hansen AARHUS UNIVERSITET DEPARTMENT OF BIOSCIENCE Liege, Belgium UNI The ratio of dark respiration to maximum photosynthesis and seasonal variability in two marine coastal waters

VERSITET Mustafa Mantikci, Stiig Markager, Jørgen Hansen AARHUS UNIVERSITET DEPARTMENT OF BIOSCIENCE Liege, Belgium UNI Seasonal variations in respiration and relationships to production and temperature

You can’t know production without Respiration… John Marra, 2013

Who respires? Robinson & Williams,2005 >95% Community Respiration

Unknown Respiration BacteriaPhytoplankton Light Size fractionation-antibiotics

‘Global’ database of Respiration Robinson & Williams, %6% 14 C PP45 th Liege Colloquium Presentations

Great Belt North sea Baltic sea Roskilde fjord monthly sampling (12 total ) (1 m & 200µM) 24 CTD profiles in 2012 Study site

14 C samples (12 light + 2 dark) Dark Incubator 2 hours Linear Light Incubator 12h Respiration samples r 2 =0.997 Experimental setup

Results / CTD Profiles GBRF

Chlorophyll a GBRF

Community Respiration (CR) GBRF

P max - P max B GB RF

Q 10 Index r 2 = 0.38 r 2 = 0.32 r 2 = 0.72 r 2 = 0.88 GBRF Lomas et al., 2002

R / P max % indicator of the trophic balance of the plankton community (Irriarte et al., 1991) GB RF

% BR as a function of Chl-a GFF filtered (Sachia et al.,unpublished)

Photosynthetic parameters r 2 = 0.19 r 2 = 0.46 r 2 = 0.53 p< Webb et al, Markager et al., 1999

Bacterial abundance and POC r 2 = 0.45r 2 = 0.42

Respiration model r 2 = 0.83 p< 0.001

Take home messages Phytoplankton biomass and temperature are the main factors governing community respiration Bacteria become relatively more important in open coastal waters with lower phytoplankton biomass If you measure PP don’t forget to measure R Mustafa

NCP GB-mixed layer RF (gC m -2 y -1 )GBRF  PP  CR  NCP  NCP NCP 1 = GPP(PP) – CR (R a +R h ) NCP 2 = PP-R a light - R a dark -R h

Depth integration of PP and CR

Photosynthetic rates (mg C m 3 h -1 ) P est alpha P EKEK c P max =P est + c E Webb, Markager et al., 1999

Respiration rates (µmol O 2 L -1 h -1 ) oxy(y) t