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REMOTE SENSING OF THE CHLOROPHYLL CONCENTRATION IN THE 
SAINT-LAWRENCE ESTUARY OF CANADA: PRE-ALGORITHMIC INVESTIGATIONS 
INTO THE OPTICAL COHERENCY OF SURFACE AND IN-SITU MEASUREMENTS 
Mehmet Yayla, Norman O'Neill and Servet Cizmeli 
CARTEL - Université de Sherbrooke, Sherbrooke — Qc., J1K 2R1 Canada 
mehmet@courrier.usherb.ca 
KEY WORDS: Oceanography, Marine Optics, Marine Chlorophyll, Ocean Colour, Chlorophyll Remote Sensing, Saint Lawrence 
Estuary, Case-II water, SeaWiFS 
ABSTRACT: 
Bio-optical measurements at SO stations in the Gulf and Estuary of Saint Lawrence were carried out over three major field 
campaigns in 1999, 2000, and 2001. These campaigns were performed over different periods of the year in order to obtain separate 
samplings of the system's seasonal cycles. The goal of these field campaigns is to arrive at a consistent remote sensing algorithm for 
the estimation of the chlorophyll concentration in the Case-Il waters (where optical properties are influenced not just by 
phytoplankton and covarying constituents, but also by non-covarying constituents such as gelbstoff and suspended sediments), of the 
Lower Saint Lawrence estuary. The optical component of these missions included measurements of inherent and apparent in-situ 
optical parameters, surface reflectance spectrometry, multi-altitude reflectance spectrometry and satellite remote sensing using 
SeaWiFS imagery. Preliminary results show systematic differences between different regions and suggest that it is possible to 
classify the St. Lawrence system into sub regions characterized by different inherent and apparent optical properties. In this 
presentation focus will be given on the observation and analysis of variations in the surface reflectance spectrometry. 
RESUME: 
Lors des missions en mer effectuées en 1999, 2000 et 2001, un ensemble de paramétres bio-optiques a été mesuré à partir de 50 
stations fixes situées dans l'estuaire et dans le golfe du Saint-Laurent. L'échantillonnage a été réparti sur différentes périodes de 
l'année, afin d'obtenir des données sur les cycles saisonniers du systéme. Le but de ces campagnes consiste à développer un 
algorithme pour l’estimation de la concentration de la chlorophylle pour les eaux de type Case-II (ou les propriétés optiques de l’eau 
sont influencées par trois quantités: la chlorophylle, le gelbstoff et les sédiments suspendus, dont les concentrations varient 
indépendamment les uns des autres). L'ensemble des données bio-optiques comprend les paramètres optiques inhérents et apparents 
in-situ, la reflectance de la surface, la reflectance à multi altitude (mesures spectrométriques aéroportées), et des données de 
télédétection spatiale basées sur les images SeaWiFS. Les résultats préliminaires montrent des différences spectrales systématiques 
selon les zones. Ceci pourrait permettre de distinguer des sous régions dans l’estuaire et dans le golfe du St. Laurent par une 
classification basée sur les propriétés optique inhérentes et apparentes des eaux de surface. Cette recherche se concentre 
principalement sur l’observation et l’analyse des variations spectrométriques de la reflectance de surface. 
1. INTRODUCTION Vessel Martha L. Black. During the period the vessel was 
inside the estuary, and when the weather permitted, daily 
1.1 Project transects with the Compact Airborne Spectrographic Imager 
: : ; (CASI) have been performed. 
Remote sensing observations of bio-oceanographic processes in 
the Saint-Lawrence system project started in 1998 and concerns The ultimate goal of the project is to develop the simplest 
à number of Canadian institutions as CARTEL - Université de operational RS algorithm which permits the estimation of 
Sherbrooke, CRESTECH - York University, Maurice- chlorophyll concentration in Case I and Case II waters of the 
Lamontagne Institute - Fisheries and Oceans Canada and LSLE. The RS algorithm development will be focused on 
ISMER-Université de Québec à Rimouski. The principal SeaWiFS data while validation will be performed using multi- 
Scientific goal of the project is to validate remotely sensed altitude spectro-radiometry as well as ship-based bio-physical 
Chlorophyll productivity algorithms for images acquired by the and spectro-optical measurements. 
SeaWiFS sensor onboard the Orbview2 satellite, over the 
Estuary and Gulf of St. Lawrence system. The project is funded 1.2 Saint Lawrence System 
by NSERC (Natural Sciences and Engineering Research 
Council, Canada) Located in the eastern Canada, the St. Lawrence system is a 
complex environment with its both estuarine and oceanic 
À set of research cruises were carried out starting from 1997, at characteristics, and with the large temporal and spatial 
different periods of the year in order to cover the system's variability of its physical and biological parameters. The overall 
seasonal cycles. These campaigns consisted of extensive system is a transitional one between continental and oceanic 
monitoring along transects made by the Canadian Coast Guard (North Atlantic) environments, influenced by large-scale 
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