Putting Temperature and Oxygen Thresholds of Marine Animals in Context of Environmental Change: A Regional Perspective for the Scotian Shelf and Gulf of St. Lawrence
Abstract:We conducted a literature review of reported temperature, salinity, pH, depth and oxygen preferences and thresholds of important marine species found in the Gulf of St. Lawrence and Scotian Shelf region. We classified 54 identified fishes and macroinvertebrates as important either because they support a commercial fishery, have threatened or at risk status, or meet one of the following criteria: bycatch, baitfish, invasive, vagrant, important for ecosystem energy transfer, or predators or prey of the above spe… Show more
“…DO has been described as a good predictor of SSLs vertical distribution (Bianchi et al, 2013). Indeed in case of low DO levels the metabolism of marine organism is often directly affected (Brennan et al, 2016;Claireaux and Lagardère, 1999;Pörtner, 2010). In our study, DO appeared to have a limited influence on SSLs vertical position, no doubt due to high DO value in both area (lowest value at 151 m bottom depth above the general recognition of hypoxia, i.e., DO < 1.43 ml l −1 (Diaz and Rosenberg, 2008;Keller et al, 2015).…”
Section: Ssls Related To Physicochemical Parameters In the Vertical Dsupporting
Abstract. Sound scattering layers SSLs distribution and their relationship to pelagic habitat characteristics is a first step to understand their role in ecosystem dynamics and their interactions with other pelagic components such as small pelagic fish. In this study two areas of the Senegalese shelf have been characterized during upwelling season corresponding to a cold inshore area and a deeper and warmer stratified offshore area that was sharply separated by a strong thermal boundary. Marine pelagic organisms usually aggregates and occurs as SSLs on echosounder. Mean SSL thickness and SSL vertical depth increase with continental shelf depth; thickest and deepest SSLs were observed in the offshore part of the continental shelf. SSLs preferendum was reported for stratified water conditions rather than fresh upwelled water. The SSLs spatiotemporal variability was mostly explained by bottom depth which influence depth, thickness, and biomass of the SSLs. Diel period and water physico-chemical characteristics had also an effect on SSL depth and SSL thickness but not on SSL biomass. Despite chlorophyll-a has statistically no effect on SSLs structure, we report that the chlorophyll-a peak was always located above or in the middle of the SSLs, often matching with the peak of SSLs biomass. Such observations indicate trophic relationships, highlighting SSLs being mainly composed of phytoplanktivorous organisms. Acoustic mapping technique of mixed layer depth is not always efficient in east border upwelling system. Lastly, over the Senegalese continental shelf the level of dissolved oxygen was not found limitative (no hypoxia) for SSLs marine pelagic organisms during upwelling event.
“…DO has been described as a good predictor of SSLs vertical distribution (Bianchi et al, 2013). Indeed in case of low DO levels the metabolism of marine organism is often directly affected (Brennan et al, 2016;Claireaux and Lagardère, 1999;Pörtner, 2010). In our study, DO appeared to have a limited influence on SSLs vertical position, no doubt due to high DO value in both area (lowest value at 151 m bottom depth above the general recognition of hypoxia, i.e., DO < 1.43 ml l −1 (Diaz and Rosenberg, 2008;Keller et al, 2015).…”
Section: Ssls Related To Physicochemical Parameters In the Vertical Dsupporting
Abstract. Sound scattering layers SSLs distribution and their relationship to pelagic habitat characteristics is a first step to understand their role in ecosystem dynamics and their interactions with other pelagic components such as small pelagic fish. In this study two areas of the Senegalese shelf have been characterized during upwelling season corresponding to a cold inshore area and a deeper and warmer stratified offshore area that was sharply separated by a strong thermal boundary. Marine pelagic organisms usually aggregates and occurs as SSLs on echosounder. Mean SSL thickness and SSL vertical depth increase with continental shelf depth; thickest and deepest SSLs were observed in the offshore part of the continental shelf. SSLs preferendum was reported for stratified water conditions rather than fresh upwelled water. The SSLs spatiotemporal variability was mostly explained by bottom depth which influence depth, thickness, and biomass of the SSLs. Diel period and water physico-chemical characteristics had also an effect on SSL depth and SSL thickness but not on SSL biomass. Despite chlorophyll-a has statistically no effect on SSLs structure, we report that the chlorophyll-a peak was always located above or in the middle of the SSLs, often matching with the peak of SSLs biomass. Such observations indicate trophic relationships, highlighting SSLs being mainly composed of phytoplanktivorous organisms. Acoustic mapping technique of mixed layer depth is not always efficient in east border upwelling system. Lastly, over the Senegalese continental shelf the level of dissolved oxygen was not found limitative (no hypoxia) for SSLs marine pelagic organisms during upwelling event.
“…It seems clear that the Mesoproterozoic ocean experienced greatly expanded anoxia compared to today 60 – 62 , requiring that atmospheric oxygen concentrations were much less than current levels. Furthermore, most modern animals, including both vertebrates and invertebrates, could not survive at oxygen levels as low as 1–4% PAL 63 . Therefore, it seems likely that increases in atmospheric oxygen beyond Mesoproterozoic levels were required to support many animals with the physiological requirements of those living today.…”
The history of atmospheric oxygen through the Mesoproterozoic Era is uncertain, but may have played a role in the timing of major evolutionary developments among eukaryotes. Previous work using chromium isotopes in sedimentary rocks has suggested that Mesoproterozoic Era atmospheric oxygen levels were too low in concentration (<0.1% of present-day levels (PAL)) for the expansion of eukaryotic algae and for the evolution of crown-group animals that occurred later in the Neoproterozoic Era. In contrast, our new results on chromium isotopes from Mesoproterozoic-aged sedimentary rocks from the Shennongjia Group from South China is consistent with atmospheric oxygen concentrations of >1% PAL and thus the possibility that a permissive environment existed long before the expansion of various eukaryotic clades.
“…Ocean warming, acidification, deoxygenation and eutrophication are manifesting on global (Bopp et al, 2013;Jickells et al, 2017;Schmidtko et al, 2017) and regional scales (Breitburg et al, 2018;Claret et al, 2018;Irby et al, 2018;Laurent et al, 2018;Fennel and Testa, 2019). These profound changes in ocean physics and biogeochemistry in combination with the ever more efficient harvesting of living marine resources are driving major shifts in marine ecosystems (Cheung et al, 2010;Bianucci et al, 2016;Brennan et al, 2016;Galbraith et al, 2017) with significant societal impacts. Changes in ocean biogeochemistry and ecosystems will also complicate conservation efforts for endangered species but are rarely considered in species recovery planning (e.g., Hartman et al, 2014).…”
Ocean ecosystems are subject to a multitude of stressors, including changes in ocean physics and biogeochemistry, and direct anthropogenic influences. Implementation of protective and adaptive measures for ocean ecosystems requires a combination of ocean observations with analysis and prediction tools. These can guide assessments of the current state of ocean ecosystems, elucidate ongoing trends and shifts, and anticipate impacts of climate change and management policies. Analysis and prediction tools are defined here as ocean circulation models that are coupled to biogeochemical or ecological models. The range of potential applications for these systems is broad, ranging from reanalyses for the assessment of past and current states, and short-term and seasonal forecasts, to scenario simulations including climate change projections. The objectives of this article are to illustrate current capabilities with regard to the three types of applications, and to discuss the challenges and opportunities. Representative examples of global and regional systems are described with particular emphasis on those in operational or pre-operational use. With regard to the benefits and challenges, similar considerations apply to biogeochemical and ecological prediction systems as do to physical systems. However, at present there are at least two major differences: (1) biogeochemical observation streams are much sparser than physical streams presenting a significant hinderance, and (2) biogeochemical and ecological models are largely unconstrained because of insufficient observations. Expansion of biogeochemical and ecological observation systems will allow for significant advances in the development and application of analysis and prediction tools for ocean biogeochemistry and ecosystems, with multiple societal benefits.
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