TRA TRANSPARENT EXOPOLYMERIC SUBSTANCES (TEP) IN HUDSON BAY NSPARENT EXOPOLYMERIC SUBSTANCES (TEP) IN HUDSON BAY DURING FALL: SIGNIFICANCE AND POTENTIAL ROLES DURING FALL: SIGNIFICANCE AND POTENTIAL ROLES Christine Michel 1 , Amandine Lapoussière 2 , Bernard LeBlanc 1 , and Michel Starr 3 1 Fisheries and Oceans Canada, Freshwater Institute, 501 University Crescent, Winnipeg (Manitoba), Canada, R3T 2N6 2 Institut des sciences de la mer (ISMER), Université du Québec à Rimouski, Rimouski (Québec), Canada, G5L 3A1 3 Fisheries and Oceans Canada, Institut Maurice Lamontagne, Mont-Joli (Québec), Canada, G5H 3Z4 ACKNOWLEDGEMENTS ACKNOWLEDGEMENTS This research was supported by Fisheries and Oceans Canada research grants to C.M. and M.S. We acknowledge NCE ArcticNet (Network Center of Excellence), Natural Sciences and Engineering Research Council (NSERC) of Canada. We express our sincere thanks to the officers and crew of the Canadian icebreaker Pierre Radisson, to M. Harvey and other colleagues for their help during the experdition and in the laboratory. REFERENCES REFERENCES SUMMARY AND CONCLUSIONS SUMMARY AND CONCLUSIONS Figure 1: Location of the sampling stations in Hudson Bay, during MERICA 2006. Note that sampling station locations were similar in 2005. ｾ These results show that TEP are widespread in pelagic waters of Hudson Bay after the summer bloom. ｾDOC and TEP concentrations were variable at stations visited in Hudson Bay during the fall. ｾ DOC and TEP concentrations were correlated with algal biomass (chl a concentrations) in surface waters. However, additional factors such as riverine input appeared to influence the vertical and spatial distribution of DOC and TEP. MATERIAL AND METHODS MATERIAL AND METHODS Sampling was conducted at stations distributed along an East-West transect in northern Hudson Bay, and in Hudson Strait and Foxe Basin during MERICA expeditions in August 2005 and 2006 (Figure 1). At each station, CTD profiles and vertical characterization of biochemical variables were performed with a CTD-Rosette sampler, equipped with a fluorescence probe. At each station, 7 euphotic depths (100%, 50%, 30%, 15%, 5%, 1%, and 0.2% of surface irradiance) and 3 aphotic depths were sampled. The water was immediately transferred into Nalgene containers and analyzed for the following: ｾChlorophyll a and phaopigments: Total chl a was determined fluorometrically after filtration of duplicate samples on Whatman GF/F 25 mm glass-fiber filters and extraction in 90% acetone in the dark at 4 o C during 24 h (Parsons et al., 1984). ｾTEP were measured spectrophotometrically after filtration of triplicate samples on 0.4 µm polycarbonate filters, staining with Alcian Blue and extraction in 80% H 2 SO 4 (Passow and Alldredge 1995). ｾDissolved organic carbon (DOC) was measured on samples filtered through combusted Whatman GF/F filters, using high-temperature catalytic combustion, on a Teckmar Dorhman TOC/TON analyzer. ｾ Due to limitations in the availability of data at the time of preparation of this paper, preliminary results on DOC are from the 2005 expedition while results on TEP are from the 2006 expedition. KEY POINTS: ｾ DOC concentrations ranged between 46 and 145 µM, and generally increased with proximity to the chl a max at stations located in the center of Hudson Bay (HB04). At stations located closer to shore (HB02), DOC concentrations were highest at surface (Fig. 2). ｾ Typical vertical profiles in TEP concentrations mirrored those in chl a, with maximum TEP concentrations observed at the depth of the chl a max. However, at stations closer to shore (HB02), an increase in TEP concentrations was also observed at surface (Fig. 3). ｾ In surface waters (top 100m), TEP concentrations were positively significantly correlated with chl a concentrations (Fig. 4). INTRODUCTION INTRODUCTION Transparent exopolymeric substances (TEP) are part of a diverse group of high molecular weight polymers that play a significant role in marine environments. These polymers, gel-like substances with sticky characteristics, are abundantly produced by algae at the end of blooms, and to a lesser extent by bacteria (e.g. Deccho, 2000; Passow, 2002). TEP are involved in various ecological processes in the pelagic environment, e.g. in cell locomotion (Wetherbee et al., 1998), adhesion to surfaces (Cooksey and Wigglesworth-Cooksey, 1995), and protection against harsh conditions (Raymond and Janech, 2003). In addition, TEP contributes to biogeochemical cycling in various ways, e.g. by enhancing (Passow, 2002) or retarding (Azetsu-Scott and Passow, 2004) the sinking flux of particles, and by shifting the carbon to nitrogen (C/N) ratio of particulate organic matter towards high values compared to the Redfield ratio (e.g. Engel, 2004). Through various bio-ecological interactions, TEP play an important role in the cycling or organic material in marine systems, yet their role in Arctic and sub-Arctic pelagic environments remain poorly studied. This paper presents preliminary results on TEP and dissolved organic carbon (DOC) concentrations in Hudson Bay waters during the fall, at a time that typically follows the phytoplankton bloom. These preliminary results were obtained during the MERICA expeditions in 2005 and 2006. Figure 4: Regression between TEP and chl a concentrations in the top 100m, at stations located along the East-West transect (data from 2006 expedition). 0 50 100 150 0.0 0.5 1.0 1.5 Chl a (mg m -3 ) TEP (µg Xantham equiv. L -1 ) P <0.001 Figure 3: Vertical profiles of chl a and TEP at station HB04 (A) and HB02 (B), during fall 2006. Depth (m) 0 50 100 150 0.0 0.5 1.0 1.5 0 100 200 0.0 0.3 0.5 Chl a (mg m -3 ) TEP (µg Xantham equiv. L -1 ) 0 50 100 150 200 Chl a TEP A) B) PRELIMINARY RESULTS PRELIMINARY RESULTS 40 80 120 160 0 40 80 120 DOC (µM) Depth (m) 0 50 100 150 200 A) Chl a max Figure 2: Vertical profiles of DOC at stations HB04 (A) and HB02 (B), during fall 2005. B) Azetsu-Scott and Passow 2004 Limonl. Oceanogr. 49:741-748; Cooksey and Wigglesworth-Cooksey 1995 Aquat. Microb. Ecol. 9: 87-96; Deccho 2000 Ocean. Mar. biol. Ann. Rev. 28: 73-153; Engel 2004 Deep-Sea Res. I 51: 83-92; Passow, 2002 Prog. Oceanogr. 55:287-333; Parsons et al. 1984 A manual for chemical and biological methods for seawater analysis, Pergamon Press, Toronto; Raymond and Janech 2003 Crybiol. 46: 203-204; Wetherbee et al. 1998 J. Phycol. 34: 9-15