Spectral Absorption of Colored Dissolved Organic Matter (CDOM) and Suspended Particulate Matter (SPM) in Mar Chiquita Coastal Lagoon (Buenos Aires, Argentina): building a dark ecological scenario

DE MARCO SILVIA G.; BELTRAME M. ORNELA; FREIJE RUBÉN H.; MARCOVECCHIO JORGE E.

Bahia Blanca, Argentina

Congreso; ECSA 44; 2008

IADO- CONICET, ECSA

Time–space distribution of CDOM and SPM spectral absorption was monitored in waters from Mar Chiquita coastal lagoon (Buenos Aires, Argentina). Six (6) sampling stations were fixed  along a salinity gradient. Subsurface water samples were taken and processed for the determination of CDOM  spectral absorption (ACDOM) and of in vivo spectral absorption of SPM (AMPS) (350 -750 nm) detritus absorption (AD) and phytoplankton absorption (AP). High absorbance values, sharp absorption inflections between 260-280 nm spectral range and a similar UV absorption pattern indicated high concentrations of CDOM in all stations during the whole study period. SPM  concentrations between 5.7 mg/L - 347 mg/L were detected. High SPM values were registered within the inner region, and during spring,  related to great storms. Water transparency was very slow (Kd values between 2 y 11 m-1). Detritus showed to be the main component of SPM and represented the major contribution to spectral absorption of SPM. Phytoplankton component occassionally was the main contributor  to spectral light absorption. From a bio-optical viewpoint, waters from Mar Chiquita costal lagoon may be clasiffied as “case 2 waters”, where detritus is the main component of SPM. This information is of great usefulness for modelling and building algorythms within water remote sensing context. Results obtained show that CDOM concentrations are high, and, together with high concentrations of SPM -dominated by detritus- , contribute to create an shaded optical environment, where PAR and UV-B solar radiation received by phytoplankton may be strongly decreased.