Living in a Fluctuating Environment Increases Tolerance to Marine Heatwaves in the Free-Living Coralline Alga Phymatolithon lusitanicum

Recently, increased attention is being paid to the importance of environmental history in species’ responses to climate-change related stressors, as more variable and heterogeneous environments are expected to select for higher levels of plasticity in species tolerance traits, compared to stable conditions. For example, organisms inhabiting environments with highly fluctuating thermal regimes might be less susceptible to the increasing frequency and intensity of marine heatwaves (MHWs). In this study, we assessed the metabolic and calcification responses of the rhodolith-bed forming Phymatolithon lusitanicum, from a coastal region that is strongly influenced by frequent changes between upwelling and downwelling conditions, to a simulated MHW scenario, with and without prior exposure to a moderate thermal stress. This allowed determining not only the influence of the species’ long-term thermal history on its resilience against MHWs, but also the rhodoliths capacity for short-term thermal stress memory and its importance during posterior MHW-exposure. Our findings indicate that the rhodoliths experienced negative impacts on daily net primary production (DNP) and calcification (DNC) during the MHW. The effect on the former was only temporary at the beginning of the MHW, while DNC was highly impacted, but exhibited a quick recovery after the event, suggesting a high resilience of the species. Furthermore, prior exposure to a moderate temperature increase, such as those occurring frequently in the natural habitat of the species, mitigated the effects of a subsequent MHW on DNP, while promoting a faster recovery of DNC after the event. Thus, our findings (1) support the hypothesis that benthic organisms living in nearshore habitats may benefit from the natural short-term temperature fluctuations in these environments with an increased resistance to MHW impacts and (2) provide first-time evidence for thermally induced stress memory in coralline algae.

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Effects of light and temperature on Mg uptake, growth, and calcification in the proxy climate archive <i>Clathromorphum</i> <i>compactum</i>

Biogeosciences ◽

10.5194/bg-15-5745-2018 ◽

2018 ◽

Vol 15 (19) ◽

pp. 5745-5759 ◽

Cited By ~ 9

Author(s):

Siobhan Williams ◽

Walter Adey ◽

Jochen Halfar ◽

Andreas Kronz ◽

Patrick Gagnon ◽

...

Keyword(s):

Sea Ice ◽

Cell Walls ◽

Natural Habitat ◽

Algal Growth ◽

High Light ◽

Coralline Algae ◽

Growth Increments ◽

Environmental Controls ◽

Wall Calcification ◽

Ice Conditions

Abstract. The shallow-marine benthic coralline alga Clathromorphum compactum is an important annual- to sub-annual-resolution archive of Arctic and subarctic environmental conditions, allowing reconstructions going back > 600 years. Both Mg content, in the high-Mg calcitic cell walls, and annual algal growth increments have been used as a proxy for past temperatures and sea ice conditions. The process of calcification in coralline algae has been debated widely, with no definitive conclusion about the role of light and photosynthesis in growth and calcification. Light received by algal specimens can vary with latitude, water depth, sea ice conditions, water turbidity, and shading. Furthermore, field calibration studies of Clathromorphum sp. have yielded geographically disparate correlations between MgCO3 and sea surface temperature. The influence of other environmental controls, such as light, on Mg uptake and calcification has received little attention. We present results from an 11-month mesocosm experiment in which 123 wild-collected C. compactum specimens were grown in conditions simulating their natural habitat. Specimens grown for periods of 1 and 2 months in complete darkness show that the typical complex of anatomy and cell wall calcification develops in new tissue without the presence of light, demonstrating that calcification is metabolically driven and not a side effect of photosynthesis. Also, we show that both light and temperature significantly affect MgCO3 in C. compactum cell walls. For specimens grown at low temperature (2 ∘C), the effects of light are smaller, with a 1.4 mol % MgCO3 increase from low-light (mean = 17 lx) to high-light conditions (mean = 450 lx). At higher (10 ∘C) temperature there was a 1.8 mol % MgCO3 increase from low to high light. It is therefore concluded that site- and possibly specimen-specific temperature calibrations must be applied, to account for effects of light when generating Clathromorphum-derived temperature calibrations.

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Warm temperatures, cool sponges: the effect of increased temperatures on the Antarctic sponge Isodictya sp.

PeerJ ◽

10.7717/peerj.8088 ◽

2019 ◽

Vol 7 ◽

pp. e8088 ◽

Cited By ~ 2

Author(s):

Marcelo González-Aravena ◽

Nathan J. Kenny ◽

Magdalena Osorio ◽

Alejandro Font ◽

Ana Riesgo ◽

...

Keyword(s):

Thermal Stress ◽

De Novo ◽

Cold Water ◽

Heat Exposure ◽

Time Frame ◽

Molecular Response ◽

Short Term ◽

Sres Scenarios ◽

Ipcc Sres ◽

The Antarctic

Although the cellular and molecular responses to exposure to relatively high temperatures (acute thermal stress or heat shock) have been studied previously, only sparse empirical evidence of how it affects cold-water species is available. As climate change becomes more pronounced in areas such as the Western Antarctic Peninsula, both long-term and occasional acute temperature rises will impact species found there, and it has become crucial to understand the capacity of these species to respond to such thermal stress. Here, we use the Antarctic sponge Isodictya sp. to investigate how sessile organisms (particularly Porifera) can adjust to acute short-term heat stress, by exposing this species to 3 and 5 °C for 4 h, corresponding to predicted temperatures under high-end 2080 IPCC-SRES scenarios. Assembling a de novo reference transcriptome (90,188 contigs, >93.7% metazoan BUSCO genes) we have begun to discern the molecular response employed by Isodictya to adjust to heat exposure. Our initial analyses suggest that TGF-β, ubiquitin and hedgehog cascades are involved, alongside other genes. However, the degree and type of response changed little from 3 to 5 °C in the time frame examined, suggesting that even moderate rises in temperature could cause stress at the limits of this organism’s capacity. Given the importance of sponges to Antarctic ecosystems, our findings are vital for discerning the consequences of short-term increases in Antarctic ocean temperature on these and other species.

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Leaf photosynthetic characteristics and net primary production of the polar willow (Salix polaris) in a high arctic polar semi-desert, Ny-Ålesund, Svalbard

Canadian Journal of Botany ◽

10.1139/b02-108 ◽

2002 ◽

Vol 80 (11) ◽

pp. 1193-1202 ◽

Cited By ~ 26

Author(s):

Hiroyuki Muraoka ◽

Masaki Uchida ◽

Masako Mishio ◽

Takayuki Nakatsubo ◽

Hiroshi Kanda ◽

...

Keyword(s):

Primary Production ◽

Net Primary Production ◽

Natural Habitat ◽

Leaf Age ◽

High Arctic ◽

Photosynthetic Characteristics ◽

Photon Flux ◽

Photon Flux Density ◽

Salix Polaris ◽

Temperature Conditions

Photosynthetic characteristics and their leaf-age dependence were examined to estimate ecophysiological effects on net primary production (NPP) of a polar willow (Salix polaris), a dominant dwarf shrub species in a polar semi-desert area of Ny-Ålesund, Svalbard. Leaves of S. polaris emerged just after snowmelt in early July in 2000; flowers were initiated within 1 week, and fruits in late July. Light-saturated rate of photosynthesis and stomatal conductance to water vapor increased rapidly to their maximum values within 1 week after leaf emergence and then decreased gradually. Depending on the leaf age, photosynthetic rates saturated at photosynthetically active photon flux density (PPFD) of 200400 µmol·m2·s1, which is the light level usually available in the natural habitat. Optimum leaf temperature of photosynthesis ranged from 10 to 18°C, while air temperature in the habitat ranged from 8 to 20°C. These light and temperature responses of photosynthesis of S. polaris would be suitable for efficient carbon gain in the natural habitat characterized by highly variable light and temperature conditions. Using the photosynthetic and respiratory characteristics, biomass distribution, and meteorological data, NPP of S. polaris in the current year was estimated to be 26.1 g C·m2. A model simulation of rising temperature conditions predicted a reduction of NPP because of a large increase in respiration. It was suggested that temperature condition and leaf phenological aspects strongly influence the carbon fixation by plants in the high arctic area studied.Key words: arctic semi-desert, climate change, net ecosystem production (NEP), net primary production (NPP), Salix polaris, photosynthesis.

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