Health and Dynamics of Marine Environments

There is a broad consensus within the scientific community recognizing that greenhouse gas emissions (carbon dioxide [CO2] and methane) have substantially contributed to modifying our planet’s climate since the beginning of the industrial era. This consensus is founded not only on numerical modeling but also on the analysis of long time-series studies.

The coordinated study of climate changes at a global scale has highlighted the existence of close and complex links between different spheres of the climate system (hydrosphere, lithosphere, atmosphere, biosphere, cryosphere). Climate change can severely impact coastal environments, involving a whole range of new physical stressors that add to the threats already weighing on these environments due to intense human activities, from maritime transport to toxic wastewater discharges.

Coastal ecosystems seem better able to withstand the effects of intense physical and chemical fluctuations compared to the open-ocean environment. These environments require more in-depth and detailed studies to determine the tolerance thresholds of different marine species in relation to climate change predictions. New threats are emerging, such as the recent but widespread use of nanoparticles in many industrial processes; these materials end up in estuarine and marine sediments, and their effects are still poorly understood. All the phenomena discussed above can impact biodiversity.

According to the International Union for Conservation of Nature (UICN) and the Census of Marine Life (a research network in which ISMER-UQAR actively participated), the current rate of species disappearance is worrisome. Over the past decade, these disappearances have intensified to the point where species are now going extinct faster than new species are being discovered. Consequently, biodiversity changes as well as the protection, conservation, and valorization of species have become key concepts guiding research activities in the domains of marine ecotoxicology, cumulative impacts, and environmental risk assessment.

In this context, researchers at ISMER-UQAR seek to better understand changes in marine environments and to predict future changes in their functioning. Their actions are implemented at different organizational levels.

Key processes underlying ecosystem functioning

ISMER-UQAR researchers promote a holistic approach to ecosystem studies that integrates biological, geological, and chemical components into regional and climatic models, in accordance with research issues defined in major national and international programs such as ARTICNET, CHONe II, ASP-ICE, BeBest, and Past4Future. This approach includes the global effect of human activities on ecosystems.

Knowledge on variations in the physical and dynamic conditions of the environment (temperature, stratification, currents, ice, illumination, reflected light intensity), dissolved organic carbon (DOC) concentration, CO2 flux, penetration of ultraviolet radiation, permafrost melting, and resuspension of methane hydrates among other factors will enable us to characterize the close coupling between physical and biological processes. The production of marine pelagic and benthic ecosystems (biomass structure and abundance) as well as the carbon fluxes associated with the cold waters off eastern Canada (Gulf of St. Lawrence, Hudson Bay, Baffin Bay) are studied in the context of climate change using modeling tools, in situ measurements, experimentation with simulated ecosystems (mesocosms), and the expertise available at ISMER-UQAR.

The ocean is a turbulent fluid in motion at variable interrelated spatial and temporal scales, from basin-scale circulation to the smallest centimetre-sized eddies. However, the numerical models of global ocean circulation used to predict climate change cannot resolve horizontal scales of less than a few tens of kilometres. Even regional numerical models are limited to scales larger than a few hundred metres. The collective effects of unresolved scales on larger scales are represented by rather crude parameterizations that often fail to account for the dynamics of unresolved movements. ISMER-UQAR researchers are therefore seeking to understand the fundamental dynamics of physical processes such as waves and their interactions with sea ice, meso- and sub-mesoscale quasi-geostrophic turbulence, small-scale turbulence, internal waves, and convection in coastal and oceanic environments. Data are collected from measurements at sea, remote sensing, laboratory experiments, and numerical modelling, all of which may lead to the formation of new theories.

The photochemistry of dissolved and particulate chromophoric organic carbon (“coloured organic matter”; CDOM and CPOM) is an essential component of the complex dynamics of marine organic carbon and nutrients. Northern marine systems, including the Arctic Ocean and the St. Lawrence Estuary system, are ideal environments for studying the photochemistry of organic matter in relation to climate change. Among other things, climate change is causing an increase in freshwater and organic matter inputs to the surface of the northern seas, thereby increasing water column stratification and the concentrations of organic substrates. The combined increase in ultraviolet (UV) radiation, organic matter input, and water column stratification synergistically amplifies the potential for oxidation of chromophoric organic matter. The aim of ISMER-UQAR’s research in this field is to assess how the photochemistry of organic matter may affect the functioning of northern marine ecosystems in a context of climate change. Among other things, we will seek to understand the influence of CDOM and CPOM photochemistry on trace gas cycling (such as carbon monoxide [CO] and dimethyl sulfide [DMS]) and on the nitrogen cycle. The effects of photochemical activity in sea ice on the ocean carbon cycle will be examined. The distribution of methane concentrations in both water and air in Canada’s arctic and subarctic regions will be monitored to identify “hot spots” associated with permafrost melting, methane hydrate destabilization, and submarine hydrocarbon infiltration.

Scientific evidence of hypoxia, eutrophication, and acidification in coastal waters around the world, including the Lower Estuary and Gulf of St. Lawrence, has increased in recent decades. Around 40% of the world’s population lives near the coast, causing various sources of anthropogenic stress in coastal ecosystems that provide goods and services to local industries and communities. Excessive nutrient loading (e.g., nitrogen and phosphorus) to watersheds accelerates algal production and decomposition of organic matter, causing higher oxygen consumption and CO2 production, thus leading to hypoxia and acidification in coastal waters. Various other environmental changes, such as rising temperatures and changes in water-mass circulation, also contribute to these effects. In addition, the higher solubility of CO2 at low temperatures means that high latitude regions are naturally more sensitive to acidification, with negative consequences for both calcifying and non-calcifying organisms.

Sediments are an important site for the remineralization of organic matter and nutrients in coastal ecosystems. Element cycles in these sediments are dominated by chemical reactions that are often induced by bacteria and are strongly influenced by macrofaunal activities and bottom water composition. At the same time, water composition is directly affected by the production or consumption of compounds dissolved in the seabed by these chemical reactions. ISMER-UQAR researchers aim to study the feedback mechanisms in the coupling between the benthic and pelagic domains that can produce environmental changes in coastal ecosystems. Among other things, particular attention is being paid to benthic respiration and nitrogen remineralization in order to better understand the role of sediments in net metabolism, nutrient balance, and oxygen depletion in the Estuary and Gulf of St. Lawrence. Studying the sensitivity of benthic processes to eutrophication will help predict how the role of sediments in an ecosystem may be altered by environmental changes. Researchers are also interested in the production of CO2 and alkalinity in coastal sediments, which affect CO2 exchanges at the water–atmosphere interface. It is therefore important to quantify these flows and to understand their sources and spatio-temporal variability.

A comprehensive study of fundamental oceanographic processes involves the observation of different types of ecosystems, from coastal systems (Estuary and Gulf of St. Lawrence, Saguenay Fjord, Hudson Bay¸ Baffin Bay, Gulf of San Jorge [Argentina]) to polar environments, with a particular focus on critical environments (e.g., coastal marshes, lagoons, and marine protected areas). Particular attention is paid to the evolution of the coastal zone, in particular coastal erosion, to be able to predict its impact on ecosystems and coastal infrastructures. An assessment of the frequency of natural hazards such as floods, storms, landslides, and earthquakes over the past millennia is crucial to the accurate modeling of their impacts.

ISMER-UQAR researchers are also interested in the effects of nutrient inputs and eutrophication in the Estuary and Gulf of St. Lawrence as well as the diversity of marine bacterial communities and their dynamics in the nitrogen cycle in coastal marshes. These marshes, home to a rich benthic community, are critical zones because water exchange remains limited and they are subject to significant anthropogenic nitrogen inputs from intensive agricultural practices as well as urban and industrial waste. Understanding the exchange of nitrogen species between the St. Lawrence Estuary and the coastal marshes that border it is required to predict the future of these marshes in the wake of current climatic upheavals and to determine the impact on the entire nitrogen bio-cycle in the St. Lawrence system.

Dissolved organic matter, such as humic substances, partly controls light penetration in the photic zone, affecting the intensity and spectral composition of photosynthetically active radiation (PAR) as well as UV radiation. These substances, produced by a wide variety of biogeochemical reactions, lead to a “chemical mutation” of natural biopolymers (lipids, proteins, sugars) synthesized by organisms. The transformed molecules form humic substances, creating new chemical configurations and reactivities that alter the fate of organic matter in the environment. Because the abundance of these substances is linked to good ecosystem functioning, ISMER researchers will strive to understand the effects of global change on the ecosystem services associated with these substances. For example, if global warming produces warmer, drier climates, this will lead to less drainage of humic substances into aquatic ecosystems, affecting the physico-chemical characteristics of the water. The solar filtering effect associated with the presence of humic substances will be altered. Humic substances can also have undesirable effects, such as promoting the development of harmful or toxic algal blooms.

Recent discoveries concerning the carbon cycle are also of interest to ISMER-UQAR researchers. In particular, the production and importance of exopolymeric particles produced by phytoplankton and bacteria appear to play a central role in carbon flows within the water column. In the future, these particles could lead to a significant increase in the intensity of biological pumping of carbon dioxide into the ocean. The St. Lawrence system, one of the largest on the planet, could make a significant contribution to global carbon fluxes, but little is known about this contribution.