Abstract
Ocean Acidification (OA) can have pervasive effects in calcifying marine organisms, and a better understanding of how different populations respond at the physiological and evolutionary level could help to model the impacts of global change in marine ecosystems. Due to its natural geography and oceanographic processes, the Chilean coast provides a natural laboratory where benthic organisms are frequently exposed to diverse projected OA scenarios. The goal of this study was to assess whether a population of mollusks thriving in a more variable environment (Talcaruca) would present higher phenotypic plasticity in physiological and morphological traits in response to different pCO2 when compared to a population of the same species from a more stable environment (Los Molles). To achieve this, two benthic limpets (Scurria zebrina and Scurria viridula) inhabiting these two contrasting localities were exposed to ocean acidification experimental conditions representing the current pCO2 in the Chilean coast (500 μatm) and the levels predicted for the year 2100 in upwelling zones (1500 (μatm). Our results show that the responses to OA are species-specific, even in this related species. Interestingly, S. viridula showed better performance under OA than S. zebrina (i.e., similar sizes and carbonate content in individuals from both populations; lower effects of acidification on the growth rate combined with a reduction of metabolism at higher pCO2). Remarkably, these characteristics could explain this species’ success in overstepping the biogeographical break in the area of Talcaruca, which S. zebrina cannot achieve. Besides, the results show that the habitat factor has a strong influence on some traits. For instance, individuals from Talcaruca presented a higher growth rate plasticity index and lower shell dissolution rates in acidified conditions than those from Los Molles. These results show that limpets from the variable environment tend to display higher plasticity, buffering the physiological effects of OA compared with limpets from the more stable environment. Taken together, these findings highlight the key role of geographic variation in phenotypic plasticity to determine the vulnerability of calcifying organisms to future scenarios of OA.
Highlights
Ocean acidification (OA) is a process where increasing amounts of anthropogenic CO2 from the atmosphere are being diluted into the ocean, affecting its geochemical balance and decreasing its pH and carbonate saturation state ( ) (Gattuso et al, 2015; IPCC, 2019)
Individuals of Scurria zebrina and Scurria viridula were collected from different populations in the upwelling center and in a near zone without the influence of semi-permanent upwelling in the northern-central Chilean coast (Figure 1): Talcaruca (30◦ 29 S, 71◦41 W) and Los Molles (32◦ 24 S, 71◦ 50 W), respectively
The highest and more variable levels of pressure of CO2 (pCO2) were observed in Talcaruca (870 ± 312.9 μmol/Kg), while a pCO2 of 458 ± 141.4 was observed in Los Molles
Summary
Ocean acidification (OA) is a process where increasing amounts of anthropogenic CO2 from the atmosphere are being diluted into the ocean, affecting its geochemical balance and decreasing its pH and carbonate saturation state ( ) (Gattuso et al, 2015; IPCC, 2019). As calcification has a core role controlling other processes such as growth, metabolism, and internal pH regulation, OA could have ubiquitous effects in these organisms (Pörtner and Farrell, 2008; Somero et al, 2016) In this context, to have a better understanding of how calcifying species are responding at the physiological and evolutionary level, it is crucial to model the impacts of this aspect of global change in marine ecosystems (Reusch, 2014; Sunday et al, 2014; Fox et al, 2019). Just a few investigations have considered the influence of geographical (e.g., Lardies et al, 2014; Gaitán-Espitia et al, 2017b; Broitman et al, 2018) and temporal environmental variation (Frieder et al, 2014; Eriander et al, 2015; Jarrold et al, 2017; Cornwall et al, 2018; Johnson et al, 2019) as drivers of differences in phenotypic plasticity or physiological responses among populations of marine organisms under OA
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