Understanding oxygen dynamics in two Discovery Islands fjords with different oxygen characteristics (oxic vs. hypoxic subsurface waters)

In the northern end of the Salish Sea, the Discovery Islands region is a network of deep fjords and narrow channels between Vancouver Island and British Columbia’s mainland. The complex interaction of fresh water inputs, bathymetry, and marine and atmospheric forcing leads to rich marine ecosystems, which sustain wild salmon during their migration as well as orcas and other species. In 2019, summer observations in two nearby fjords, Bute Inlet and Toba Inlet, showed quite different oxygen characteristics. While Bute was fully oxygenated and had high oxygen concentrations in the upper waters, Toba experienced an oxygen minimum layer, with near-hypoxic waters. In this work, we aim to explore the mechanisms that led to these differences by the means of a coupled physical-biogeochemical ocean model. Our physical model is a high resolution (up to ~60 m) application of the Finite Volume Community Ocean Model (FVCOM) that extends from the northern tip of Texada Island to Johnstone Strait. The biogeochemical module, called FVCOM-ICM, allows for the representation of plankton, nutrient and oxygen dynamics in the region. In particular, we are interested in understanding what are the key processes dominating the distribution of dissolved oxygen concentrations, how they differ between the two neighbouring inlets, and whether these processes could change along with climate. In this presentation, we will discuss our latest results and future plans

Contribution of hurricane-induced sediment resuspension to coastal oxygen dynamics

© The Author(s), 2018. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Scientific Reports 8 (2018): 15740, doi:10.1038/s41598-018-33640-3.Hurricanes passing over the ocean can mix the water column down to great depths and resuspend massive volumes of sediments on the continental shelves. Consequently, organic carbon and reduced inorganic compounds associated with these sediments can be resuspended from anaerobic portions of the seabed and re-exposed to dissolved oxygen (DO) in the water column. This process can drive DO consumption as sediments become oxidized. Previous studies have investigated the effect of hurricanes on DO in different coastal regions of the world, highlighting the alleviation of hypoxic conditions by extreme winds, which drive vertical mixing and re-aeration of the water column. However, the effect of hurricane-induced resuspended sediments on DO has been neglected. Here, using a diverse suite of datasets for the northern Gulf of Mexico, we find that in the few days after a hurricane passage, decomposition of resuspended shelf sediments consumes up to a fifth of the DO added to the bottom of the water column during vertical mixing. Despite uncertainty in this value, we highlight the potential significance of this mechanism for DO dynamics. Overall, sediment resuspension likely occurs over all continental shelves affected by tropical cyclones, potentially impacting global cycles of marine DO and carbon.Support for J. Moriarty was provided by the USGS Mendenhall Program

Distribución de nutrientes inorgánicos y clorofila-a a través de los frentes de la Plataforma Continental Patagónica Argentina durante verano y otoño

Oceanographic data collected during 2001-2003 on the Patagonian Continental Shelf of Argentina were analyzed in order to study the main chemical features of this large shelf. The variation of inorganic nutrients and chlorophyll-a during summer and fall in an area within 40 to 60 km from the coast are presented. Nitrate is the limiting nutrient in the region and is negatively correlated to chlorophyll-a. All variables show localized variations in summer, which can be related to tidal fronts through the comparison of our data with the critical Simpson parameter of stability (50 J m-3). In fall, nutrient concentrations on the continental shelf were more uniform and generally higher than in summer due to the disruption of these fronts.Datos oceanógraficos recolectados durante 2001-2003 en la Plataforma Continental Patagónica Argentina fueron analizados para estudiar las principales características químicas en esta gran plataforma. Se presenta la variación de los nutrientes inorgánicos y de la clorofila-a a una distancia de 40 a 60 km de la costa. El nitrato es el nutriente limitante en la región y está negativamente correlacionado con la clorofila-a. Todas las variables presentan variaciones localizadas en verano, las cuales pueden ser relacionadas con los frentes de marea a través de la comparación de nuestros datos con el parámetro crítico de estabilidad de Simpson (50 J m-3). En otoño, la concentración de nutrientes en la plataforma continental fue más uniforme y generalmente mayor que en verano debido a la disrupción de dichos frentes.Facultad de Ciencias Naturales y Muse

Sensitivity of the regional ocean acidification and carbonate system in Puget Sound to ocean and freshwater inputs

While ocean acidification was first investigated as a global phenomenon, coastal acidification has received significant attention in recent years, as its impacts have been felt by different socio-economic sectors (e.g., high mortality of shellfish larvae in aquaculture farms). As a region that connects land and ocean, the Salish Sea (consisting of Puget Sound and the Straits of Juan de Fuca and Georgia) receives inputs from many different sources (rivers, wastewater treatment plants, industrial waste treatment facilities, etc.), making these coastal waters vulnerable to acidification. Moreover, the lowering of pH in the Northeast Pacific Ocean also affects the Salish Sea, as more acidic waters get transported into the bottom waters of the straits and estuaries. Here, we use a numerical ocean model of the Salish Sea to improve our understanding of the carbonate system in Puget Sound; in particular, we studied the sensitivity of carbonate variables (e.g., dissolved inorganic carbon, total alkalinity, pH, saturation state of aragonite) to ocean and freshwater inputs. The model is the updated version of our FVCOM-ICM framework (Finite Volume Community Ocean Model coupled to the water-quality model CE-QUAL-ICM), now with carbonate-system and sediment modules. Sensitivity experiments altering concentrations at the open boundaries and freshwater sources indicate that not only ocean conditions entering the Strait of Juan de Fuca, but also the dilution of carbonate variables by freshwater sources, are key drivers of the carbonate system in Puget Sound. This work is an update from our presentation in the Salish Sea Conference 2016, showing the final results from our model experiments

Salish Sea model: ocean acidification module and the response to regional anthropogenic nutrient sources

Several monitoring programs indicate the presence of lower pH and related changes in carbonate system variables in the Salish Sea. This project expands the existing Salish Sea Model to evaluate carbonate system variables. This project quantifies the influences of regional nutrient sources on acidification. The model accounts for Pacific Ocean upwelled water, regional human nutrient contributions, and air emissions around the Salish Sea. This effort also identifies geographical areas and seasons experiencing greater influence from regional sources of nutrients to Salish Sea waters. Results from this effort indicate that increased dissolved inorganic nitrogen, phytoplankton biomass, and non-algal organic carbon caused by regional anthropogenic nutrient sources can constitute significant contributors to acidification in the Salish Sea

Targeting redox metabolism of the maize-Azospirillum brasilense interaction exposed to arsenic-affected groundwater

Arsenic in groundwater constitutes an agronomic problem due to its potential accumulation in the food chain. Among the agro-sustainable tools to reduce metal(oid)s toxicity, the use of plant growth-promoting bacteria (PGPB) becomes important. For that, and based on previous results in which significant differences of As translocation were observed when inoculating maize plants with Az39 or CD Azospirillum strains, we decided to decipher the redox metabolism changes and the antioxidant system response of maize plants inoculated when exposed to a realistic arsenate (AsV) dose. Results showed that AsV caused morphological changes in the root exodermis. Photosynthetic pigments decreased only in CD inoculated plants, while oxidative stress evidence was detected throughout the plant, regardless of the assayed strain. The antioxidant response was strain-differential since only CD inoculated plants showed an increase in superoxide dismutase, glutathione S-transferase (GST), and glutathione reductase (GR) activities while other enzymes showed the same behavior irrespective of the inoculated strain. Gene expression assays reported that only GST23 transcript level was upregulated by arsenate, regardless of the inoculated strain. AsV diminished the glutathione (GSH) content of roots inoculated with the Az39 strain, and CD inoculated plants showed a decrease of oxidized GSH (GSSG) levels. We suggest a model in which the antioxidant response of the maize-diazotrophs system is modulated by the strain and that GSH plays a central role acting mainly as a substrate for GST. These findings generate knowledge for a suitable PGPB selection, and its scaling to an effective bioinoculant formulation for maize crops exposed to adverse environmental conditions.Fil: Peralta, Juan Manuel. Universidad Nacional de Rio Cuarto. Facultad de Cs.exactas Fisicoquimicas y Naturales. Instituto de Investigaciones Agrobiotecnologicas. - Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnologico Conicet - Cordoba. Instituto de Investigaciones Agrobiotecnologicas.; ArgentinaFil: Bianucci, Eliana Carolina. Universidad Nacional de Rio Cuarto. Facultad de Cs.exactas Fisicoquimicas y Naturales. Instituto de Investigaciones Agrobiotecnologicas. - Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnologico Conicet - Cordoba. Instituto de Investigaciones Agrobiotecnologicas.; ArgentinaFil: Romero Puertas, María C.. Consejo Superior de Investigaciones Científicas. Estación Experimental del Zaidín; EspañaFil: Furlan, Ana Laura. Universidad Nacional de Rio Cuarto. Facultad de Cs.exactas Fisicoquimicas y Naturales. Instituto de Investigaciones Agrobiotecnologicas. - Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnologico Conicet - Cordoba. Instituto de Investigaciones Agrobiotecnologicas.; ArgentinaFil: Castro, Stella Maris. Universidad Nacional de Rio Cuarto. Facultad de Cs.exactas Fisicoquimicas y Naturales. Instituto de Investigaciones Agrobiotecnologicas. - Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnologico Conicet - Cordoba. Instituto de Investigaciones Agrobiotecnologicas.; ArgentinaFil: Travaglia, Claudia Noemi. Universidad Nacional de Rio Cuarto. Facultad de Cs.exactas Fisicoquimicas y Naturales. Instituto de Investigaciones Agrobiotecnologicas. - Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnologico Conicet - Cordoba. Instituto de Investigaciones Agrobiotecnologicas.; Argentin

An overview of the Salish Sea model: existence of reflux mixing and recurring hypoxia

An improved version of a diagnostic hydrodynamic and biogeochemical model (nutrients, phytoplankton, carbon, dissolved oxygen, pH) of the Salish Sea has been developed with the ability to simulate characteristic circulation and water quality features. Notable improvements include expansion of the model domain beyond the Salish Sea, encompassing Vancouver Island and out to the continental shelf boundary. In this talk we present an overview of the model setup describing the model domain coverage, modeling framework, development of boundary conditions, and tidal, riverine, wastewater, and meteorological inputs. Ability of the model to reproduce known circulation features within the Salish Sea is highlighted. The existence of a strong circulation cell between Admiralty Inlet and Tacoma Narrows sills is discussed reflecting on the implications of reflux flow back into Central Puget Sound. Simulation of sediment diagenesis processes and coupling to the water column provides improved model performance that is responsive to land based and oceanic nutrient loads. This coupling is also credited with the improvements in simulation of hypoxia in selected sub-basins within the Salish Sea such as Hood Canal, Penn Cove, and East Sound. Using tidally averaged velocity profiles from the Salish Sea Model, we demonstrate that Hood Canal sub-basin, with a sill near the mouth, a deep channel configuration, and a freshwater source at its landward end, behaves like a classic-fjord. The dominant and notable feature is that circulation and exchange in the inner basin of Hood Canal occurs in the upper 40% of the water column while the lower 60% remains poorly mixed and relatively isolated from the exchange. This results in conditions well suited for the settling of organic matter and long residence times \u3e230 days, and causes recurring hypoxia in the inner regions of Hood Canal in late fall

Distribución de nutrientes inorgánicos y clorofila-a a través de los frentes de la Plataforma Continental Patagónica Argentina durante verano y otoño

Oceanographic data collected during 2001-2003 on the Patagonian Continental Shelf of Argentina were analyzed in order to study the main chemical features of this large shelf. The variation of inorganic nutrients and chlorophyll-a during summer and fall in an area within 40 to 60 km from the coast are presented. Nitrate is the limiting nutrient in the region and is negatively correlated to chlorophyll-a. All variables show localized variations in summer, which can be related to tidal fronts through the comparison of our data with the critical Simpson parameter of stability (50 J m-3). In fall, nutrient concentrations on the continental shelf were more uniform and generally higher than in summer due to the disruption of these fronts.Datos oceanógraficos recolectados durante 2001-2003 en la Plataforma Continental Patagónica Argentina fueron analizados para estudiar las principales características químicas en esta gran plataforma. Se presenta la variación de los nutrientes inorgánicos y de la clorofila-a a una distancia de 40 a 60 km de la costa. El nitrato es el nutriente limitante en la región y está negativamente correlacionado con la clorofila-a. Todas las variables presentan variaciones localizadas en verano, las cuales pueden ser relacionadas con los frentes de marea a través de la comparación de nuestros datos con el parámetro crítico de estabilidad de Simpson (50 J m-3). En otoño, la concentración de nutrientes en la plataforma continental fue más uniforme y generalmente mayor que en verano debido a la disrupción de dichos frentes.Facultad de Ciencias Naturales y Muse

Sensitivity of Flushing and Water Quality in Salish Sea Sub-basins to Exchange through Johnstone Strait Pathway – a modeling Study

The importance of tidally averaged inflow of upwelled Pacific Ocean water on flushing and water quality of the Salish Sea is well known. The general understanding is that this exchange flow enters Salish Sea along the bed, primarily through the Strait of Juan de Fuca, and is distributed north to the Strait of Georgia and south into Puget Sound. It has therefore been a common practice to neglect the connection of Salish Sea to the Pacific Ocean through the secondary pathway of Discovery Passage and the Johnstone Strait. The simplification of the Johnstone Strait boundary treatment in the leading predictive models of Salish Sea is a source of uncertainty and limitation that has not yet been characterized. A completely closed boundary approach assumes that there is zero exchange between the Pacific Ocean and the Salish Sea through Johnstone Strait and likely overestimates the strength of exchange flow. In this presentation we describe an improved Salish Sea Model developed using FVCOM-ICM where the limitation of the ocean boundary at Johnstone Strait has been eliminated. The model with expanded domain around Vancouver Island and covering the continental shelf extending from Coos Bay, Oregon in the south to Queen Charlotte Sound north of Vancouver Island was applied in a sensitivity analysis mode. A preliminary assessment previously provided an indication that significant fraction of tidally averaged flow exits the domain through the Johnstone Strait. The assessment has been refined with updated bathymetry provided by the Department of Fisheries and Oceans, Canada. Relative magnitudes of exchange of freshwater and nutrients between the Salish Sea and the Pacific Ocean through the Strait of Juan de Fuca and Johnstone Strait were re-characterized. The sensitivity of simplified/closed treatment of Johnstone Strait boundary on flushing times and water quality in Salish Sea sub-basins will be presented