Dissolved organic carbon (DOC) released by macroalgae is an intrinsic component of the coastal ocean carbon cycle, yet knowledge of how future ocean warming may influence this is limited. Temperature is one of the primary abiotic regulators of macroalgal physiology, but there is minimal understanding of how it influences the magnitude and mechanisms of DOC release. To investigate this, we examined the effect of a range of temperatures on DOC release rates and physiological traits of Ecklonia radiata, the most abundant and widespread kelp in Australia that represents a potentially significant contribution to coastal ocean carbon cycling.
View Article and Find Full Text PDFKelps are in global decline due to climate change, which includes ocean warming. To identify vulnerable species, we need to identify their tolerances to increasing temperatures and determine whether tolerances are altered by co-occurring drivers such as inorganic nutrient levels. This is particularly important for those species with restricted distributions, which may already be experiencing thermal stress.
View Article and Find Full Text PDFKelp forests are threatened by ocean warming, yet effects of co-occurring drivers such as CO are rarely considered when predicting their performance in the future. In Australia, the kelp forms extensive forests across seawater temperatures of approximately 7-26°C. Cool-edge populations are typically considered more thermally tolerant than their warm-edge counterparts but this ignores the possibility of local adaptation.
View Article and Find Full Text PDFAlgal carbon-to-nitrogen (C:N) and carbon-to-phosphorus (C:P) ratios are fundamental for understanding many oceanic biogeochemical processes, such as nutrient flux and climate regulation. We synthesized literature data (444 species, >400 locations) and collected original samples from Tasmania, Australia (51 species, 10 locations) to update the global ratios of seaweed carbon-to-nitrogen (C:N) and carbon-to-phosphorus (C:P). The updated global mean molar ratio for seaweed C:N is 20 (ranging from 6 to 123) and for C:P is 801 (ranging from 76 to 4102).
View Article and Find Full Text PDFCarbon sequestration is defined as the secure storage of carbon-containing molecules for >100 years, and in the context of carbon dioxide removal for climate mitigation, the origin of this CO is from the atmosphere. On land, trees globally sequester substantial amounts of carbon in woody biomass, and an analogous role for seaweeds in ocean carbon sequestration has been suggested. The purposeful expansion of natural seaweed beds and aquaculture systems, including into the open ocean (ocean afforestation), has been proposed as a method of increasing carbon sequestration and use in carbon trading and offset schemes.
View Article and Find Full Text PDFMarine heatwaves are extreme events that can have profound and lasting impacts on marine species. Field observations have shown seaweeds to be highly susceptible to marine heatwaves, but the physiological drivers of this susceptibility are poorly understood. Furthermore, the effects of marine heatwaves in conjunction with ocean warming and acidification are yet to be investigated.
View Article and Find Full Text PDFIncreased plant biomass is observed in terrestrial systems due to rising levels of atmospheric CO, but responses of marine macroalgae to CO enrichment are unclear. The 200% increase in CO by 2100 is predicted to enhance the productivity of fleshy macroalgae that acquire inorganic carbon solely as CO (non-carbon dioxide-concentrating mechanism [CCM] species-i.e.
View Article and Find Full Text PDFOcean acidification (OA) is the reduction in seawater pH due to the absorption of human-released CO2 by the world's oceans. The average surface oceanic pH is predicted to decline by 0.4 units by 2100.
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