Zooplankton density in the St.Lawrence River, Québec (2006)

Zooplankton and environmental data were surveyed at 52 sites distributed in 16 transects along three biogeographical zones: the fluvial section zone (FSZ), the fluvial estuary zone (FEZ), and the estuarine transition zone (ETZ) along the fluvial estuary section of the St. Lawrence River (Québec). Two surveys were conducted in May and August 2006 between Cornwall (Ontario) and île aux Coudres (Québec).

Personne(s) ayant accès aux données

Personne(s) ayant collecté les données

Autres institutions

GRIL (Groupe de Recherche Interuniversitaire en Limnologie et Environnement Aquatique) and UQTR (Université du Québec à Trois-Rivières).

Personne en chare des données

Audrey Lafrenaye

Source(s) de financement

This study was partially supported by grants from the Natural Science and Engineering Research Council (NSERC to BPA, PL and J-JF) and the Fonds Québécois de la Recherche sur la Nature et les Technologies (FQRNT to the GRIL). The sampling cruises were supported by a grant from the NSERC shiptime program to J.-JF (P/I). The construction and operation of the research vessel Lampsilis was funded by a CFI grant to the GRIL (Groupe de Recherche Interuniversitaire en Limnologie et Environnement Aquatique) at UQTR.

Format du jeu de données

Excel documents

Information additionnelle

We thank Simon de Sousa, Patrice Thibeault, Virginie Roy and Ginette Méthot for various assistances during field sampling and the Captain F. Harvey and the crew of the Lampsilis research vessel for their invaluable support during cruises. We are indebted to Ginette Méthot (Université de Montréal) and Michel Clément (Swedish Museum of Natural History) for helping in zooplankton taxonomic analysis and to Olivier Champoux (Environment Canada) for the mapping of water masses.

Nombre de sites

52 stations

Description du site

The zooplankton sampling units and the environmental data were collected during two cruises of the research vessel Lampsilis, conducted during the spring (23 to 30 May) and summer (8 to 15 August) of 2006. A total of 52 stations, distributed along 16 transversal transects, were visited in three biogeographical zones of the SLR from Cornwall to Île aux Coudres along a 375 km transect. Transects were positioned perpendicularly to the main east-to-west axis of the SLR. Locations of stations within each transect were determined in order to study the lateral heterogeneity of the SLR water masses. Unfortunately, some sites in the FC (sites 10, 15 and 16) and the LSP (sites 22, 28, 29, 35) were not sampled due to technical problems during the sampling cruise in August. The lacking sites in LSP, which were located in the northern and southern shallow littoral zones, were probably richer in zooplankton, as these highly vegetated zones had considerably greater macrozooplancton biomass than in the open water during mid-summer. Their loss may have significantly biased the results.

Habitat

The fluvial section zone (FSZ; sites 1-35) is 240 km long from Cornwall in Ontario to the Lake Saint-Pierre outlet in Québec, and ranges from < 2 km to 10 km wide (St. Lawrence Centre (SLC) 1996). This freshwater zone encompasses three fluvial lakes (Lake Saint-François (LSF), Lake Saint-Louis (LSL) and Lake Saint-Pierre (LSP)), and one fluvial corridor (FC). There is no or very little tidal effect to this point. Fluvial lakes are wide, slow flowing (< 0.3 m·s-1 with the exception of the central channel), and shallow, with depth averaging 6 m for LSF and 3 m in LSL and LSP, whereas the fast flowing (1 m·s-1) navigation channel is 11.3 to 15 m deep. The fluvial lakes are extensively colonized by submerged macrophyte beds. Those slow flowing littoral areas are isolated from the rapidly circulating central channel during years of relatively low macrophytes development, this transversal discontinuity limiting exchanges among the main northern, southern and central water masses. The main channel is fed by the clear waters of Lake Ontario, whereas the south and north shores receive waters from the tributaries. The fluvial estuary zone (FEZ; sites 36-45) stretches more than 160 km from the LSP outlet to the eastern tip of île d’Orléans. River width ranges from 870 m near Québec City to 15 km at the eastern end of Île d’Orléans. Average water depth in the main channel varies from 13 to 40 m. The FEZ is composed of fresh waters and shows significant semidiurnal tides (averaging 4.1 m) at Québec City. The upper estuary covers 150 km from the eastern tip of île d’Orléans to the mouth of the Saguenay River. Average width is 17 km and depth varies from 100 to 300 m. In this study, we included this section up to île aux Coudres only, this portion being called the estuarine transition zone (ETZ; sites 46-52). In this region, high-intensity currents encounter tides which cause fresh and salt water mixing, strong upwelling currents and important sediment resuspension. Highly turbid waters on the north shore, especially in the area between île d’Orléans and île aux Coudres, originate from this sediment resuspension. Meteorological conditions were uniform during each sampling cruises and water masses stability was validated by satellite images. The sampling periods reflected seasonal variations in discharge. Tributaries discharge was much more important in May than in August, and that was reflected on the cumulative discharge of the SLR, mostly at Trois-Rivières, downstream of LSP and the confluence of the major St. Lawrence tributaries.

Environnement

Aquatique

Taxa étudiés

Zooplankton

Information taxonomique

Crustacées, Animaux invertébrés autre qu'arthropodes.

Détails taxonomiques

Nom latin	Nom anglais	Nom français

Approche expérimentale

ZOOPLANKTON SAMPLING AND ANALYSIS : Zooplankton was collected at each site using a conical net (1 m mouth opening, 153 µm mesh size) hauled horizontally at the same depth as for water collection. Zooplankton are generally longer than 153 µm. Net filtered volume was measured with a flowmeter (General Oceanic). Upon collection, zooplankton organisms were split into fractions with a Folsom splitter. One/eight of each sampling unit was reserved for taxonomy and transferred to 250 ml plastic bottles. Zooplankton was narcotized with carbonated water and preserved in a buffered 4% sugar-formaldehyde solution and stored for later analysis. In the laboratory, a subsample was taken with a large opening pipette, transferred to a Ward rotative cell and analysed under a stereomicroscope. Adult copepods were identified to species. The copepodid stages (C1–C5) were categorised to appropriate suborder (Calanoida, Cyclopoida, Harpacticoida), while nauplii were not enumerated. For cladocerans, amphipods and mysids, identification was carried up to species level when it was possible and adults were at least identified to genus level. Identification of cladocerans was made based on Edmonston (1959), Amoros (1984) and Hebert (1995). Identification of copepods was made following Hudson et al. (2003), Lesko et al. (2003a, 2003b), Lacroix (1981), Huys et al. (1996), Edmondson (1959), and Smith and Fernando (1978). We identified amphipods using Bousfield (1958) and Holsinger (1972), and mysids using Brunel (1960) and Brunel et al. (1998). Laboratory procedures are described in details in Pinel-Alloul et al. (1990). Counts of crustacean species were expressed as numbers of individuals per cubic metre accounting for subsampling fractionation during field collection and microscopic analysis. ENVIRONMENTAL VARIABLES : At each site, water temperature (Tem, °C), conductivity (Cond, µS·cm-1), turbidity (Turb, NTU), pH and dissolved oxygen (DO, mg·L-1) were measured in situ using a Conductivity Temperature Depth profiler (YSI 6600 EDS-M sensor array, Yellow Spring Instruments). A spectroradiometer-fluorometer (HFT: Satlantic hyperpro-Wetlab C Star) was used to determine underwater profiles of light irradiance and calculate by Simpson integration the light available for photosynthesis (PAR: 400-700 nm). Water samples were collected using an 8 liters GO-Flow water sampler (Model 1080; General Oceanics) 1 m below the surface at each site. To measure chlorophyll a (Chl-a), dissolved organic carbon (DOC, mg·L-1), total nitrogen (TN, mg·L-1), total phosphorus (TP, µg·L-1), total dissolved solids (TDS, mg·L-1), and chromophoric dissolved organic matter (aCDOM, m-1), subsamples were drawn from the GO-Flow bottles into acid-washed polyethylene bottles. Chl-a concentrations were measured with a Turner Designs 10–005R fluorometer, after sonication and 24 h extraction in 90% acetone at 4°C in the dark. For phosphorus analyses, samples for soluble reactive phosphorus (SRP) were filtrated on 45 mm diameter, 0.7-µm pore size GFF filters (Millipore) and kept frozen until analysis. SRP was analyzed using the acid molybdate technique (APHA, AWWA, and WPCF 1998). DOC measurements were undertaken as follows: at each sampling site, 200 mL of water was filtered through a 45 mm diameter, 0.2-µm nominal poresize polycarbonate membrane (Isopore; Millipore). Membranes were pre-rinsed with 100 mL of MilliQ water to remove potential impurities. The filtrate was stored in acid-washed borosilicate bottles and kept in the dark at 4°C until analysis. DOC concentrations were determined with a total organic carbon analyzer (TOC-1010; OI Analytical, College Station, Texas, USA) by sodium persulfate digestion. CDOM absorbance (aCDOM) was measured with a Shimadzu UV-2401PC UV–Vis spectrophotometer (Shimadzu, Columbia, Maryland, USA) using a 1-cm quartz cell between 190 and 900 nm. See Frenette et al. (2006) and Massicotte and Frenette (2011) for calculations of the absorption coefficients.

Statut de l'étude

Complété

Stratégie d'echantillonnage

Échantillonnage passif (e.g. trappe à insecte ou à animal)

Objectifs de l'étude

Niveau de la communauté (e.g. richesse, distribution, composition)

Types de données

Liste d'espèces, Abondance/abondance relative/fréquence

Fréquence d'échantillonnage

The zooplankton sampling units and the environmental data were collected during two cruises of the research vessel Lampsilis, conducted during the spring (23 to 30 May) and summer (8 to 15 August) of 2006.

Première année de collecte de données

2006

Dernière année de collecte de données

2006

Pinel-Alloul B, Cusson E, Aldamman L. 2011. Diversity and spatial distribution of copepods in the St. Lawrence River
(Québec, Canada). Crustaceana monographs, vol 16, pp 425–429

Massicotte P, Frenette J-J, Proulx R, Pinel-Alloul B, Bertolo A. 2014. Riverscape heterogeneity explains spatial variation in zooplankton functional evenness and biomass in a large river ecosystem. Landscape Ecology, vol 29, Issue 1, pp 67-79

Données