Christian Nozais

Christian Nozais
Université du Québec à Rimouski UQAR | uqar · Département de Biologie, Chimie et Géographie

About

93
Publications
21,873
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2,407
Citations
Citations since 2017
5 Research Items
698 Citations
2017201820192020202120222023020406080100120
2017201820192020202120222023020406080100120
2017201820192020202120222023020406080100120
2017201820192020202120222023020406080100120
Additional affiliations
January 2012 - present
January 2003 - December 2008
Université du Québec à Rimouski UQAR
January 2001 - present

Publications

Publications (93)
Data
Description This study sought to estimate the effect of an anthropogenic and climate-driven change in prey availability on the degree of individual and population specialization of a large marine predator, the fin whale (Balaenoptera physalus) in the estuary and the gulf of St. Lawrence (eastern Canada). Specifically, we here examine the trophic ni...
Chapter
Full-text available
Living, harvestable resources in the upper Arctic Ocean ultimately depend on the production of marine microalgae. Microalgal production also mitigates global warming by fixing the greenhouse gas CO2 into biomass, of which a portion sinks to the seafloor. This process, called the ‘biological CO2 pump’, supplies food to the benthic organisms living a...
Article
Full-text available
Different krill species have a pivotal position in many marine food webs by both preying upon several tro-phic levels and being forage species for consumers. Within these food webs, different krill species coexist, though it remains unclear what mechanisms allow for the coexistence, for instance, of northern krill species in subarctic environments....
Presentation
Full-text available
In subarctic ecosystems, the krill communities are composed of many species, ranging from temperate to arctic, with diverse morphology and ecology. These krill species may express differential eco-physiological traits, which in turn may vary with strong seasonal changes in temperature and food supply in these environments. To enhance our capacity t...
Article
1. Ecological differences among species are usually associated with phenotypic differences that enable species to lessen interspecific competition. Many cryptic species co-occur in communities, thus raising the question of their ecological equivalency. In the case of freshwater amphipods from the Hyalella azteca cryptic species complex, both eco...
Article
Using stable isotope analyses, the present study looked at the fractionation of carbon and nitrogen isotopes between bulk sediment organic matter, particulates from the water column, and benthic consumers from the Northwestern Mediterranean continental shelf. Results showed that sedimentary organic matter in the area under study mainly consisted of...
Poster
Full-text available
In this poster we describe the benthic macrofauna community in the sediment cores that were used for enrichment experiments.
Article
Full-text available
Stable isotopes are a powerful tool used to study the diets of animals because they provide information on food assimilated over an extended period. However, trophic enrichment factors used to reconstruct diets sometimes vary substantially, even among animals from the same trophic level. The goal of this study was to verify if trophic enrichment fa...
Presentation
Full-text available
Krill as forage species play a key role in energy transfer to higher trophic levels in marine ecosystems. In the St. Lawrence estuary, three krill species (Meganyctiphanes norvegica, Thysanoessa raschii, Thysanoessa inermis) coexist and dominate the macrozooplankton biomass. Although, these species are ecologically important, the dynamics of their...
Poster
Full-text available
The lower St. Lawrence estuary (LSLE) is influenced by river discharge and saltwater inflow. Together with arctic water inflow and ice cover in winter, a strong stratification occurs resulting in a cold intermediate layer (CIL) from spring to autumn. This stratification provides thermal habitats. Here, we focus on two krill species Thysanoessa rasc...
Article
Full-text available
Forestry activities in the Canadian Boreal region have increased in the last decades, raising concerns about their potential impact on aquatic ecosystems. Water quality and fluorescence characteristics of dissolved organic matter (DOM) were measured over a 3-year period in eight eastern Boreal Shield lakes: four lakes were studied before, 1 and 2 y...
Chapter
Full-text available
Living, harvestable resources in the upper Arctic Ocean ultimately depend on the production of marine microalgae. Microalgal production also mitigates global warming by fixing the greenhouse gas CO2 into biomass, of which a portion sinks to the seafloor. This process, called the ‘biological CO2 pump’, supplies food to the benthic organisms living a...
Article
Full-text available
Forestry activities in the Canadian Boreal region have increased in the last decades, raising concerns about their potential impact on aquatic ecosystems. Water quality and fluorescence characteristics of dissolved organic matter (DOM) were measured over a three-year period in eight Eastern Boreal Shield lakes: four lakes were studied before, one a...
Article
Full-text available
This experimental microcosm study reports the influence of organic enrichments by mussel biodeposits on the metabolic activity and functional diversity of benthic prokaryotic communities. The different biodeposit enrichment regimes created, which mimicked the quantity of faeces and pseudo-faeces potentially deposited below mussel farms, show a clea...
Chapter
Full-text available
Living, harvestable resources in the upper Arctic Ocean ultimately depend on the production of marine microalgae. Microalgal production also mitigates global warming by fixing the greenhouse gas CO2 into biomass, of which a portion sinks to the seafloor. This process, called the “biological CO2 pump”, supplies food to the benthic or ganisms living...
Conference Paper
Full-text available
it is now well known that submarine groundwater discharge (SGD) transport nutrients, carbon and trace elements which may contribute to eutrophication in coastal waters. Nevertheless transports and transformations pathways from coastal aquifers to the ocean are still poorly constrained, particularly in permeable sandy beaches which are recognized as...
Conference Paper
Full-text available
In Canada, interest in a potential new krill source focusses on the evaluation of biochemical composition of northern and arctic krill for nutraceutical, cosmetic and pharmaceutical industries. Our prime objective is to examine the ecological resilience of the krill stocks in the St. Lawrence system prior to human exploitation. Krill stocks must co...
Conference Paper
Full-text available
Background/Question/Methods Disturbances play a significant role in shaping the community structure, influence the patterns of species richness and diversity, and affect ecosystem functioning. Their influence on biodiversity has captivated ecologists for several decades. Disturbances can be quantified in two ways: intensity and frequency. Because...
Conference Paper
Full-text available
Background/Question/Methods Many species are presumed to coexist stably by occupying different ecological niches. However, the existence of ecological differences among species of a community is not always clear. This is especially the case of species that are morphologically similar but genetically different, also called cryptic species. From a r...
Article
Full-text available
In boreal lakes, temperature and photoperiod are important environmental cues affecting reproduction, growth and feeding rates of benthic invertebrates; however, how invertebrates cope with seasonal changes in the availability of their food sources has rarely been addressed. In this study, where temperature and light conditions were controlled, we...
Article
Full-text available
Perturbations on ecosystems can have profound immediate effects and can, accordingly, greatly alter the natural community. Land-use such as forestry activities in the Canadian Boreal region have increased in the last decades, raising concerns about their potential impact on aquatic ecosystems. The objective of this study was to evaluate the impact...
Article
Full-text available
There is an urgent need to develop predictive indicators of the effect of species loss on ecosystem functioning. Body size is often considered as a good indicator because of its relationship to extinction risk and several functional traits. Here, we examined the predictive capacity of species body size in marine and freshwater multitrophic systems....
Chapter
Full-text available
Living, harvestable resources in the upper Arctic Ocean ultimately depend on the production of marine microalgae. Microalgal production also mitigates global warming by fixing the greenhouse gas CO2 into biomass, of which a portion sinks to the seafloor. This process, called the “biological CO2 pump”, supplies food to the benthic organisms living a...
Article
The biodiversity–ecosystem functioning (B–EF) relationship has become of main interest in the last few decades, mostly because of the worldwide increase in species extinctions. However, most of these studies only consider species within single size‐class or trophic level, thereby most likely underestimating ecosystem complexity. To reach more reali...
Article
Full-text available
Understanding the impacts of species extinctions on the functioning of food webs is a challenging task because of the complexity of ecological interactions. We report the impacts of experimental species extinctions on the functioning of two food webs of freshwater and marine systems. We used a linear model to partition the variance among the multip...
Article
Full-text available
Allochthonous inputs can be an important contribution of organic matter in lake eco- systems. Yet, our understanding of the patterns of energy dependence of littoral invertebrates and fish is poor. We measured carbon ( δ 13 C) and nitrogen ( δ 15 N) stable isotope values for primary pro- ducers, terrestrial detritus, benthic macroinvertebrates, zoo...
Article
Organisms inhabiting shallow coastal ecosystems are potentially exposed to damaging levels of solar UV radiation. UV-sunscreen compounds such as mycosporine like amino-acids (MAAs) are a widespread bio-chemical strategy among many marine organisms to counteract UV stress. These molecules are produced through a metabolic pathway restricted to cyanob...
Poster
Full-text available
Poster presentation ”Tracing organic matter sources of canadian Arctic benthic invertebrates with stable isotopes” for IPY 2012, Montreal, Canada
Article
Full-text available
The Hyalella azteca (Saussure) complex includes numerous amphipod cryptic species in freshwater habitats in America as revealed by DNA barcoding surveys. Two ecomorphs (small and large) have evolved numerous times in this complex. Few phenotypic criteria have been found to differentiate between the numerous species of this complex. The present stud...
Article
Full-text available
The Great Whale River region on the eastern shore of Hudson Bay, Canada, encompasses the villages of Whapmagoostui (Cree First Nation) and Kuujjuarapik (Inuit) and surrounding areas. The principal field station of Centre d'tudes nordiques (CEN: Centre for Northern Studies) has operated at Whapmagoostui-Kuujjuarapik (W-K; 55° 15′ N, 77° 45′ w) since...
Data
The co-occurrence of cryptic species of Hyalella amphipods is a challenge to our traditional views of how species assemble. Since these species have similar morphologies, it is not evident that they have developed phenotypic differences that would allow them to occupy different ecological niches. We examined the structure of a community of Hyalella...
Article
Full-text available
Corals live in close association with bacterial communities, but the nature of the relationship is still poorly understood. In this study, three scleractinian coral species, Galaxea fascicularis, Pavona cactus and Turbinaria reniformis were incubated under different laboratory conditions, and the composition of the bacterial community associated wi...
Article
Full-text available
Corals live in close association with bacterial communities, but the nature of the relationship is still poorly understood. In this study, three scleractinian coral species, Galaxea fascicularis, Pavona cactus and Turbinaria reniformis were incubated under different laboratory conditions, and the composition of the bacterial community associated wi...
Article
Full-text available
The co-occurrence of cryptic species of Hyalella amphipods is a challenge to our traditional views of how species assemble. Since these species have similar morphologies, it is not evident that they have developed phenotypic differences that would allow them to occupy different ecological niches. We examined the structure of a community of Hyalella...
Article
Full-text available
The microbial growth curve is widely studied within microbiology classes and bacteria are usually the microbial model used. Here, we describe a novel laboratory protocol involving flow cytometry to assess the growth dynamics of the unicellular microalgae Isochrysis galbana. The algal model represents an appropriate alternative to bacteria because i...
Data
This dataset consists of vertical profiles of discrete depth sampled over the Southeastern Beaufort Sea for chlorophyll a concentration of different size fractions: >0.7µm, >5µm and >20µm. Sampling took place from September to October 2002, from September to November 2003 and from June to August 2004. Chlorophyll a concentrations were determined by...
Article
Full-text available
The phytoplankton community of the Mackenzie shelf and the Amundsen Gulf (southeastern Beaufort Sea) was characterized (e.g. chlorophyll a biomass, primary production and taxonomy) during autumn 2002 (23 September to 14 October) and 2003 (30 September to 14 November). Spatial differences were evident, particularly in early autumn. Total phytoplankt...
Article
Full-text available
Logging activity was a regular practice in the boreal forest of Quebec during the 19th century and may have had an impact on the temporal dynamics of aquatic coarse woody debris (CWD) and associated organisms. The dynamics of white cedar (Thuja occidentalis) CWD inputs from the riparian environment in a boreal lake in Eastern Quebec, Canada, over t...
Article
The Mackenzie River is the largest river on the North American side of the Arctic and its huge freshwater and sediment load impacts the Canadian Beaufort Shelf. Huge quantities of sediment and associated organic carbon are transported in the Mackenzie plume into the interior of the Arctic Ocean mainly during the freshet (May to September). Changing...
Article
Full-text available
Depth profiles of heterotrophic bacteria abundance were measured weekly over a 6-month period from December to May in Franklin Bay, a 230 m-deep coastal Arctic Ocean site of the southeastern Beaufort Sea. Total bacteria, low nucleic acid (LNA) and high nucleic acid (HNA) bacteria abundances were measured using flow cytometry after SYBR Green I stai...
Article
Full-text available
Mouth breaching is a recurrent event in temporarily open/closed estuaries (TOCEs). Such disturbances result in flushing and sediment scouring, reducing the microalgal biomass stock. The depletion of these microalgae may have negative repercussions in the form of depleted stocks of commercial fish, game fish, crustaceans and mollusks. The aim of thi...
Article
Diel variations of cellular optical properties were examined for cultures of the haptophyte Imantonia rotunda N. Reynolds and the diatom Thalassiosira pseudonana (Hust.) Hasle et Heimdal grown under a 14:10 light:dark (L:D) cycle and transferred from 100 μmol photons · m−2 · s−1 to higher irradiances of 250 and 500 μmol photons · m−2 · s−1. Cell vo...
Article
Full-text available
The distribution of picophytoplankton (0.2–2 µm) and nanophytoplankton (2–20 µm) in the Beaufort Sea–Mackenzie Shelf and Amundsen Gulf regions during autumn, 2002 is examined relative to their ambient water mass properties (salinity, temperature and nutrients: nitrate + nitrite, phosphate, and silicate) and to the ratio of variable to maximum fluor...
Article
Pelagic–benthic coupling is relatively well studied in the marginal seas of the Arctic Ocean. Responses of meiofauna with regard to seasonal pulses of particulate organic matter are, however, rarely investigated. We examined the dynamics of metazoan meiofauna and assessed the strength of pelagic–benthic coupling in the Southeastern Beaufort Sea, du...
Article
Temporarily open/closed estuaries (TOCEs) account for almost 71% of the total number of South African estuarine systems. To date the dynamics of microalgal production and biomass in TOCEs is poorly understood. A survey was therefore conducted in two TOCEs along the KwaZulu-Natal coast: the river-dominated Mdloti and the marine-dominated Mpenjati. T...
Article
Full-text available
In studies of the biological effects of UV radiation, ozone depletion can be mimicked by performing the study under ambient conditions and adding radiation with UV-B lamps. We evaluated this methodology at three different locations along a latitudinal gradient: Rimouski (Canada), Ubatuba (Brazil) and Ushuaia (Argentina). Experiments of the effect o...
Article
UV irradiance has a broad range of effects on marine planktonic organisms. Direct and indirect effects on individual organisms have complex impacts on food-web structure and dynamics, with implications for carbon and nutrient cycling. Mesocosm experiments are well suited for the study of such complex interrelationships. Mesocosms offer the possibil...
Article
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http://www.atypon-link.com/WDG/doi/pdf/10.1515/BOT.2006.002?cookieSet=1 Variations in microphytobenthic biomass were investigated in relation to major environmental factors in the Mdloti and Mhlanga temporarily open/closed estuaries (TOCEs), South Africa, from March 2002 to March 2003. Both estuaries receive different volumes of treated sewage wate...
Article
Full-text available
One hundred and eighty-four of the 250 estuaries in South Africa are currently classified as temporarily open/closed and close off from the sea during the dry season, under low river inflow. The subtropical Mdloti Estuary, on the KwaZulu-Natal north coast, is one of these systems and hardly any information is available on its meiofauna. The abundan...
Article
It is crucial to study how food resources are allocated in order to understand how invertebrate species of soft-bottomed benthic communities can live in the same environment, especially when belonging to the same trophic level. On the southern shore of the Lower St. Lawrence Estuary, the polychaetes Nereis virens (Nereidae) and Nephtys caeca (Nepht...
Article
The effect of light–dark cycle on the timing of larval release from jelly masses of the Mediterranean polychaete Eupolymnia nebulosa (Terebellida) was investigated. The larval emergence from the jelly mass occurs mainly during daylight. Results suggest that the larvae of E. nebulosa do not track the light–dark cycle endogenously.
Article
Full-text available
Seventy-three percent of South African estuaries are temporarily-open and close off from the sea during the dry season, under low river inflow. Following periods of high rainfall, the water level rises gradually until breaching of the sandbar at the mouth occurs. These ecosystems often exhibit high zooplankton (0.008–2.6 g DW m –3) but low phytopla...
Article
Full-text available
Recently, the Arctic has experienced a recurrent springtime thinning of the stratospheric ozone layer resulting in increasing ultraviolet-B radiation (UVBR, 280 to 320 nm). However, little is known about the effect of such UVBR enhancement on the Arctic ecosystem. In spring-summer 1998 and fall 1999, 40 stations were investigated in the North Water...
Article
Full-text available
Gastrosaccus brevifissura is a key crustacean species in most South African estuaries. The biomass, distribution, grazing rates and feeding preferences of this species were investigated in the Mpenjati Estuary, on the east coast of South Africa. The species exhibits a very marked diurnal migration behaviour, with biomass varying within the range 0....
Article
Full-text available
A 12-month survey investigated seasonal variations in the vertical distribution of benthic microalgal biomass in relation to major factors potentially controlling their dynamics in the subtropical temporarily open Mdloti Estuary, KwaZulu Natal, South Africa. Benthic microalgal chla concentrations in the upper 5 cm of sediment ranged from 259 mg m (...
Article
Full-text available
The fate of first-year ice algae production was assessed from April to June 1998, in the North Water Polynya. A landfast ice station was regularly visited and sampled for biomass, composition, and production of bottom ice algae, composition and grazing of the bottom ice meiofauna, and under-ice sedimentation. The latter was assessed using particle...
Article
Full-text available
δ13C and δ15N analyses show that the three dominant zooplankton species of the Mpenjati Estuary (South Africa) derive their energetic requirements from specific and unique food sources within the same trophic level.
Article
Full-text available
[1] Short-term free-drifting particle interceptor traps were deployed at 28 stations from April to July 1998 in the North Water Polynya (northern Baffin Bay). The amount, composition, and vertical transformation of the organic material sinking out of the euphotic zone were assessed. Clear seasonal sedimentation patterns were apparent throughout the...
Article
Of South Africa's 250 estuaries, 182 (73% of the total) are classified as temporarily-open. There is, however, little information currently available on their physico-chemical-biological properties and processes. This study addresses some aspects of the primary biomass available in these systems, in order to provide basic information for their sust...