Warming impacts on early life stages increase the vulnerability and delay the population recovery of a long‐lived habitat‐forming macroalga

Abstract

1. Understanding the combined effects of global and local stressors is crucial for conservation and management, yet challenging due to the different scales at which these stressors operate. Here, we examine the effects of one of the most pervasive threats to marine biodiversity, ocean warming, on the early life stages of the habitat-forming macroalga Cystoseira zosteroides, its long-term consequences for population resilience, and its combined effect with physical stressors.2. First, we performed a controlled laboratory experiment exploring the impacts of warming on early life stages. Settlement and survival of germlings were measured at 16°C (control), 20°C, and 24°C, and both processes were affected by increased temperatures. Then, we integrated this information into stochastic, density-dependent integral projection models.3. Recovery time after a major disturbance significantly increased in warmer scenarios. The stochastic population growth rate (λ s ) was not strongly affected by warming alone, as high adult survival compensated for thermal-induced recruitment failure. Nevertheless, warming coupled with recurrent physical disturbances had a strong impact on λ s and population viability. 4.Synthesis. The impact of warming effects on early stages may significantly decrease the natural ability of habitat-forming algae to rebound after major disturbances. These findings highlight that, in a global warming context, populations of deep-water macroalgae will become more vulnerable to further disturbances, and stress the need to incorporate abiotic interactions into demographic models. K E Y W O R D Sclimate change, demography, human impacts, population ecology, quasi-extinction, recovery, seaweeds, stress interactions 1130 | Journal of Ecology CAPDEVILA Et AL.

Are we ready for scaling up restoration actions? An insight from Mediterranean macroalgal canopies

“…Germlings mortality can be density-dependent [40, 41], and intraspecific competition might be exacerbated by limited nutrient availability and elevated temperatures [65]. High temperature itself may reduce survival of juvenile macroalgae [66–68], although undesirable effects have not been detected for the growth of Cystoseira barbata juveniles [42]. Yet, the temperature range experimentally investigated by Irving et al [42] simulates naturally occurring spring values (16°), which might result less stressing compared to the extreme temperature values tested by other authors [65–68], better resembling the stressful summer conditions occurring in our restoration experiment.…”

Differential effects of pollution on adult and recruits of a canopy-forming alga: implications for population viability under low pollutant levels

“…Macroalgal forests formed by species of the orders Fucales and Laminariales are structurally and functionally complex ecosystems 6 – 11 . These highly productive and iconic ecosystems are declining in some areas due to the accumulation of anthropogenic impacts, such as those related to intensive land use, pollution, warming or invasive species 12 – 22 . The loss of macroalgal forests also implies a loss or impoverishment of ecosystem services such as nutrient cycling, food production, nursery habitat provision, erosion reduction, and control of water quality 13 .…”

Response of foundation macrophytes to near‐natural simulated marine heatwaves

“…We tested whether single and sequential heatwaves lead to an increase or decrease in sensitivity to thermal stress (when treatments were compared to the control and among each other) on F. vesiculosus and Z. marina populations of the Baltic Sea. F. vesiculosus germlings were included in the experiment, in order to determine whether early life‐history stages (which are critical to maintain seaweed or seagrass beds; Coelho, Rijstenbil, & Brown, ) are more sensitive to environmental changes, as often proposed (Andrews, Bennett, & Wernberg, ; Capdevila et al, ; Coelho et al, ; Wernberg et al, ). We investigated the impacts of single and repeated heatwaves on crucial responses of F. vesiculosus and Z. marina , which included (a) photosynthesis and respiration of Z. marina , (b) growth rates of F. vesiculosus and Z. marina , (c) abundance of the Z. marina pathogen ( L. zosterae ) and Z. marina 's ability for defence against this pathogen (anti‐ L. zosterae defence), (d) abundance of epibacteria on F. vesiculosus and the macroalga's ability to deter epibacterial colonization (antibacterial defence), (e) defence against grazers in F. vesiculosus (antigrazing defence) and (f) survival and growth of F. vesiculosus germlings.…”

“…We tested whether single and sequential heatwaves lead to an increase or decrease in sensitivity to thermal stress (when treatments were compared to the control and among each other) on F. vesiculosus and Z. marina populations of the Baltic Sea. F. vesiculosus germlings were included in the experiment, in order to determine whether early life-history stages (which are critical to maintain seaweed or seagrass beds; Coelho, Rijstenbil, & Brown, 2000) are more sensitive to environmental changes, as often proposed (Andrews, Bennett, & Wernberg, 2014;Capdevila et al, 2019;Coelho et al, 2000;Wernberg et al, 2010). We investigated the impacts of single and repeated heatwaves on crucial responses…”