Nitrogen sufficiency enhances thermal tolerance in habitat-forming kelp: implications for acclimation under thermal stress

Abstract

Local and global changes associated with anthropogenic activities are impacting marine and terrestrial ecosystems. Macroalgae, especially habitat-forming species like kelp, play critical roles in temperate coastal ecosystems. However, their abundance and distribution patterns have been negatively affected by warming in many regions around the globe. Along with global change, coastal ecosystems are also impacted by local drivers such as eutrophication. The interaction between global and local drivers might modulate kelp responses to environmental change. This study examines the regulatory effect of no 3 − on the thermal plasticity of the giant kelp Macrocystis pyrifera. To do this, thermal performance curves (TPCs) of key temperature-dependant traits-growth, photosynthesis, NO 3 − assimilation and chlorophyll a fluorescence-were examined under nitrate replete and deplete conditions in a short-term incubation. We found that thermal plasticity was modulated by NO 3 − but different thermal responses were observed among traits. Our study reveals that nitrogen, a local driver, modulates kelp responses to high seawater temperatures, ameliorating the negative impacts on physiological performance (i.e. growth and photosynthesis). However, this effect might be species-specific and vary among biogeographic regions -thus, further work is needed to determine the generality of our findings to other key temperate macroalgae that are experiencing temperatures close to their thermal tolerance due to climate change.Rising levels of atmospheric CO 2 are causing increases in air and sea surface temperatures (SSTs), with the mean SST predicted to rise by 1.4 °C to 4.8 °C by 2100 1 . With global warming, extreme high temperature events such as marine heat waves (MHWs) have also increased in frequency, intensity and duration along the World's coastline, including the Mediterranean, Australia and Brazilian Atlantic sea 2-6 . These anomalous elevated temperatures have negatively impacted marine and terrestrial ecosystems by altering species' composition and distribution patterns 7-9 . Such ecological changes are also severely impacting ecosystem goods and services such as fisheries, and carbon sequestration and storage 10 . The impacts of warming are considerably larger in marine systems because of their greater sensitivity to these global stressors compared to terrestrial systems 11,12 . Because of this, there is rising concern about the capacity of marine species to acclimate quickly enough to short-term variability in temperature, which will be critical for organisms to adapt and survive in a changing ocean 13,14 .In ectothermic organisms such as plants, algae, invertebrates and lower vertebrates, temperature is the major factor regulating their physiology, growth, performance and fitness [15][16][17][18][19][20] . Therefore, changes in environmental temperatures (T a ) due to climate change will trigger modifications at physiological and biochemical levels, influencing whole-organism thermal plasticity (i.e. thermal sensitivities and...

Influence of the Macronutrients N, P and K on the Agarophyte <i>Alsidium triquetrum</i> (S. G. Gmelin) Trevisan, during Experimental Culture

“…The lack of phosphorus is accentuated in the stage of rapid multiplication. The mean element concentration value was significantly higher than the magnitude reported by [31]. The tropical macroalgae typical of environments with high concentrations of carbonate in sediments (0.07% vs 0.16% d. w).…”

“…Temperature or lighting limitations are capable of uncoupling the tissue concentration of some nutrients from the growth rate [35] [36]. This phenomenon is capable of restricting net algal productivity [31].…”

Aquaculture Production of the Brown Seaweeds Laminaria digitata and Macrocystis pyrifera: Applications in Food and Pharmaceuticals

“…The seaweed industry requires large quantities and high-quality seaweed raw material that exerts pressure on the existing natural seaweed resources. Aquaculture cultivation of seaweed has grown considerably since 2009 to meet product demand and to protect wild kelp beds that are still under threat from over-exploitation and climate change, which has caused increases in ocean water temperatures [ 251 ]. To produce high value products (HVP) from seaweed requires considerable cultivation control to retain quality biomass, not possible in offshore systems; therefore, onshore aquacultures have been proposed to fulfil this need [ 252 ].…”

Effect of environmental history on the habitat-forming kelp Macrocystis pyrifera responses to ocean acidification and warming: a physiological and molecular approach

“…It is generally thought that Macrocystis tends to be a more cold-adapted species, and cannot survive at temperatures above 20 °C 53 , 63 . A recent study has shown that the optimum temperature (T opt ) for growth in adult’s individuals of Macrocystis is close to 16 °C, and temperature above T opt (i.e., at 24 °C) can negatively affect its physiological performance 104 . However, NO 3 − enrichment can modulate these responses, enhancing for example, their physiological thermal tolerance, ameliorating the negative impacts of sub-optimal temperatures 104 .…”

“…A recent study has shown that the optimum temperature (T opt ) for growth in adult’s individuals of Macrocystis is close to 16 °C, and temperature above T opt (i.e., at 24 °C) can negatively affect its physiological performance 104 . However, NO 3 − enrichment can modulate these responses, enhancing for example, their physiological thermal tolerance, ameliorating the negative impacts of sub-optimal temperatures 104 . Although we found that both populations were equally negatively affected by elevated temperatures, relative growth rates remained above 9% day −1 , which might be attributed to the non-limiting level of NO 3 − supplied during the experiments (> 5 µM).…”