Particle distribution and composition in the NE Aegean Sea based on transmissometry, optical backscattering and size measurements

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1 Particle distribution and composition in the NE Aegean Sea based on transmissometry, optical backscattering and size measurements Karageorgis A.P., Androni A., Assimakopoulou G., Banks A.C., Drakopoulos P., Kabouri G., Kanellopoulos Th., Krasakopoulou E., Lagaria A., Morfis Ι., Pagou K., Papadopoulos V., Parinos K., Psarra S., Renieris P., Spyridakis N.

2 Perseus and AegeanMarTech PERSEUS: Policy-oriented marine Environmental Research for the Southern European Seas. Funded by the EU under FP7 Theme Oceans of Tomorrow Coordinator: Dr E. Papathanassiou-HCMR AegeanMarTech: Technological and oceanographic cooperation Network for the Study of mechanisms fertilizing the North-East Aegean Sea. Funded by the Ministry of Education-Thales Coordinator: Dr S. Psarra-HCMR

3 AEGEX Bio-optics experiment Towards a better assessment of the planktonic productivity estimate (measurements of bio-optical properties of open-sea waters and association to remote sensing products) Eastern Mediterranean => Levantine Basin, Aegean Inherent optical properties In situ reflectance Remote sensed reflectance Ground truthing Chl-a concentration Primary productivity Eutrophication/Oligotrophication

4 Comparison of remote sensing mean monthly data (MODIS) with in situ Chl-α values Interannual ( ), area 1: BSW influence This session 10:30-10:45 Assessing phytoplankton dynamics in the Aegean Sea: combining remote sensing and field data of Chlorophyll a Psarra S. et al. Projects ( ) ANREC July 2003 Sept July 2004 EUROCEANS Sept April 2006 POSEIDON May 2007 SESAME April 2008 Sept Significant deviation in the area under the influence of BSW Minimum deviation when maximum values are attained in the field (spring bloom, April 2006) Chl-α sat / Chl-α in situ = 4,1±1,9!

5 Inverse radiative transfer The inversion problem is to determine the biogeochemical parameters from the upwelling radiance spectrum, i.e. the normalized water-leaving radiance. The inversion is a two-step process: the derivation of IOPs from the radiance, and then biogeochemical parameters from the IOPs. Historically, starting with the CZCS, remote sensing inversions have been focused on the direct derivation of the chlorophyll concentration from water leaving radiance. This was based on the early recognition that chlorophyll-laden waters are greener than chlorophyll poor waters.

6 IOPs RADIATION TRANSFER AOPs ACS a, b ECO-BB b b b R k b RS b a b + FORWARD LISST PARTICLE SIZE DISTRI- BUTION Chl a CONCENTRATION GROUND TRUTHING REVERSE 1.6 POSTER No. 32 R rs An Underwater Optical Instrument Platform for the measurement of the 0.8 RS optical REFLECTANCE properties of sea water R rs (sr -1 ) x 10-3 RS REFLECTANCE wavelength (nm) DOWNWELLING IRRADIANCE UPWELLING RADIANCE -PAR Spyridakis N.,Psarra S., Karageorgis A., Banks A.C.

7 PERSEUS-Thales Cruises Olson et al, JPO cruises in the N. Aegean sea 1 cruise in the Cretan Sea 50 profiles

8 PERSEUS-Thales Cruise Oct. 2013

9 PERSEUS-Thales Cruise Oct C (m -1 )

10 PERSEUS-Thales Cruise Oct C (m -1 ) C (m -1 )

11 PERSEUS-Thales Cruise Oct %PPPPPP = PPPPPP PPPPPP xxxxx %POC mean = 35.6 ± 19.1 n = 70 %PPPPPP = PPPPPP PPPPPP xxxxx

12 PERSEUS-Thales Cruise Oct C (m -1 )

13 Thales Cruise March 2014

14 Thales Cruise July 2014

15 Combining IOPs and bulk biogeochemical properties

16 Conclusions We examined the IOPs of the NE Aegean Sea waters for the first time BSW is a major hydrological feature defined by a m layer exhibiting low salinity Beam c p appeared to be enhanced at the surface and near bottom Total Chl-α showed subsurface maxima CDOM originates both in the BSW and the decomposition of autotrophic organisms at mid waters High POC:Chl-α ratio in the BSW points to predominance of detritus and heterotrophic bacteria over autotrophs The backscattering ratio provides insights into particle composition via the particle index of refraction The presence of microaggragates is confirmed throughout the cruises

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