Impact of oceanic forcing on coastal groundwater dynamics and chemical discharge to the sea Dr. Clare Robinson Civil and Environmental Engineering, Western University, Ontario, Canada Sustainable management of coastal surface water and groundwater resources is a majorenvironmental challenge due to increasing anthropogenic and climate stressors on coastal areas. Understanding groundwater-ocean interactions is critical for effective management of coastal water resources. From a marine perspective, chemical inputs to coastal seas via groundwater discharge can considerably impact coastal chemical budgets and impair water quality. From a terrestrial perspective, these interactions impact the quality of fresh groundwater resources by influencing salinization and associated mobilization of chemicals in coastal aquifers. Oceanic forcing (e.g., tides and waves) complicate groundwater-coastal water interactions as these forcing drive large quantities of coastal water to recirculate across the groundwater-ocean interface, and alter groundwater flows, salinization and geochemical conditions in coastal aquifers. Further, these forcings intensify mixing and reactions in the subterranean estuary and this in turn controls chemical loading to the ocean.  This presentation will provide an overview of recent advances from my research team in understanding dynamic groundwater-ocean interactions including their impact on contaminants including arsenic and fecal bacteria.  Finally, the presentation will also discuss the need to develop typologies for subterranean estuaries to enable interpolation and extrapolation of information between site-specific field studies, and to identify strategic data gaps.

The study of prokaryotes using environmental genomics offers unique opportunities to overcome statistical and technical limitations on the study of communities and populations in situ. In this lecture, I will showcase recently introduced bioinformatic tools, statistical techniques, and applications of genomics and metagenomics to the study of environmental adaptations to different environments. I will primarily focus on the problem of sampling coverage both within and between species. Sampling coverage affects the recovery of genomes from metagenomes, limits of detection, estimates of relative abundance, occupancy, and diversity, and comparisons of microdiversity. I will showcase techniques for the diagnosis of such issues, estimation of coverage in metagenomes, and methods to ameliorate the confounding effect of coverage. I will also show an application of these controls to the evaluation of global distributions of freshwater prokaryotes and its relationship with genome size.

Microbialite ecosystems offer glimpses into life’s adaptions and responses to past speciation or extinction events. Formed by microbial organisms and microalgae, they accrete layered geobiological calcified deposits (stromatolites) that are analogous to those in the fossil record as far back as 3.45 billion years ago, which is the longest and most uninterrupted record of ecosystem resilience on Earth. Supratidal spring-fed living microbialite ecosystems (SSLiME) occurring in South Africa are rare in that they are actively growing, extant examples of microbialites at the interface of fresh carbonate-rich groundwater discharging above the highwater mark. Exactly what the relevance of these living ecosystems are and how they can be used to interpret past climate change, coastal processes and species adaptations is being uncovered. Many animals that are bioturbators and supposedly should disrupt microbial biofilm lamination are active in these ecosystems. Instead, SSLiME are a biodiversity refuge, hosting previously unknown and unusual taxa such as the stromatolite tanaidid Sinelobus stromatoliticus, which seems to be endemic to these habitats. Functionally, they provide services such as connecting species associated with other environments such as estuaries, thereby providing a stepping-stone habitat link along the coastline. This is being revealed using next-generation sequencing techniques. The biodiversity of SSLiME and the insights it provides in terms of understanding past evolutionary dynamics and modern ecological processes is explored in this presentation.

Self-organization processes can play a key role in defining the adaptive response of ecosystems to climate change. Ecosystems can adjust spatial patterning, drainage networks, or other spatial structures due to the interaction between sessile organisms such as plants of bivalves and physical processes such as water flow or infiltration rate, locally stimulating growth, but at the same time optimizing growth conditions at the landscape scale. Modelling studies highlight that this process could play a crucial role in allowing ecosystems such as arid bushland, salt marshes and dunes to adjust to climate change. Despite this adaptive potential, human activities severely constrain self-organisation processes. Agricultural practices have globally homogenised landscapes. Dykes and human buildings and infrastructure now constrain many coastal ecosystems, limiting the potential for ecosystems to adapt to the rising sea. Here, I discuss a number of studies in which we highlight that self-organisation is a crucial process defining the adaptive capacity of salt marsh ecosystems. Creek formation, shaped by a scale-dependent feedback between plant growth and sedimentation, is an important process defining how salt marshes can follow sea level rise. Model analysis highlights that when these creeks closely mimic natural creek systems, these creeks create significant flow rates, allowing for quick sediment transport into the marsh. To end, I will discuss how these processes are included in ecosystem digital twins to predict how to restoration practices, and whether this is a feasible thing to do.

The ocean has been shielding the earth from the worst effects of rapid climate change by absorbing excess carbon dioxide from the atmosphere. This absorption of CO2 is driving the ocean along the pH gradient towards more acidic conditions. At the same time ocean warming is having pronounced impacts on the composition, structure and functions of marine ecosystems. Warming, freshening and associated stratification are driving a trend in ocean deoxygenation. The combined impact of warming, acidification and deoxygenation are already having a dramatic effect on the flora and fauna of the oceans and mirror similar events in the Earth’s past, which were often coupled with extinctions of major species’ groups. At the same time, climate induced changes on the continents are increasing around the globe: Extreme weather events, floodings, draughts and wild fires. Here I review the observed impacts, set out what the future may hold if carbon emissions and climate change are not significantly reduced with more or less immediate effect and discuss how nature-based solutions, like enhanced rock weathering, are needed to counteract the climate problem.