Examinando por Autor "Lagos, Nelson A."
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Ítem Acidification and high-temperature impacts on energetics and shell production of the edible clam Ameghinomya antiqua(Frontiers Media S.A., 2022-09) Martel, Sebastián I.; Fernández, Carolina; Lagos, Nelson A.; Labra, Fabio A.; Duarte, Cristián; Vivanco, Juan F.; García Herrera, Claudio; Lardies, Marco A.Warming and ocean acidification are currently critical global change drivers for marine ecosystems due to their complex and irreversible effects on the ecology and evolution of marine communities. Changes in the chemistry and the temperature of the ocean impact the biological performance of marine resources by affecting their energy budget and thus imposing energetic restrictions and trade-offs on their survival, growth, and reproduction. In this study, we evaluated the interplaying effects of increased pCO2 levels and temperature on the economically relevant clam Ameghinomya antiqua, an infaunal bivalve inhabiting a wide distributional range along the coast of Chile. Juvenile clams collected from southern Chile were exposed to a 90-day experimental set-up emulating the current and a future scenario projeced to the end of the current century for both high pCO2/low-pH and temperature (10 and 15°C) projected for the Chilean coast. Clams showed physiological plasticity to different projected environmental scenarios without mortality. In addition, our results showed that the specimens under low-pH conditions were not able to meet the energetic requirements when increased temperature imposed high maintenance costs, consequently showing metabolic depression. Indeed, although the calcification rate was negative in the high-pCO2 scenario, it was the temperature that determined the amount of shell loss. These results indicate that the studied clam can face environmental changes for short-term periods modifying energetic allocation on maintenance and growth processes, but with possible long-term population costs, endangering the sustainability of an important benthic artisanal fisheries resource. Copyright © 2022 Martel, Fernández, Lagos, Labra, Duarte, Vivanco, García-Herrera and Lardies.Ítem Effects of temperature and ocean acidification on shell characteristics of Argopecten purpuratus: implications for scallop aquaculture in an upwelling-influenced area(INTER-RESEARCH, 2016) Lagos, Nelson A.; Benítez, Samanta; Duarte, Cristian; Lardies, Marco A.; Broitman, Bernardo R.; Tapia, Christian; Tapia, Pamela; Widdicombe, Steve; Vargas, Cristian A.Coastal upwelling regions already constitute hot spots of ocean acidification as naturally acidified waters are brought to the surface. This effect could be exacerbated by ocean acidification and warming, both caused by rising concentrations of atmospheric CO2. Along the Chilean coast, upwelling supports highly productive fisheries and aquaculture activities. However, during recent years, there has been a documented decline in the national production of the native scallop Argopecten purpuratus. We assessed the combined effects of temperature and pCO(2)-driven ocean acidification on the growth rates and shell characteristics of this species farmed under the natural influence of upwelling waters occurring in northern Chile (30 degrees S, Tongoy Bay). The experimental scenario representing current conditions (14 degrees C, pH similar to 8.0) were typical of natural values recorded in Tongoy Bay, whilst conditions representing the low pH scenario were typical of an adjacent upwelling area (pH similar to 7.6). Shell thickness, weight, and biomass were reduced under low pH (pH similar to 7.7) and increased temperature (18 degrees C) conditions. At ambient temperature (14 degrees C) and low pH, scallops showed increased shell dissolution and low growth rates. However, elevated temperatures ameliorated the impacts of low pH, as evidenced by growth rates in both pH treatments at the higher temperature treatment that were not significantly different from the control treatment. The impact of low pH at current temperature on scallop growth suggests that the upwelling could increase the time required for scallops to reach marketable size. Mortality of farmed scallops is discussed in relation to our observations of multiple environmental stressors in this upwelling-influenced area.Ítem Plasticity in organic composition maintains biomechanical performance in shells of juvenile scallops exposed to altered temperature and pH conditions(Nature Research, 2021-12) Lagos, Nelson A.; Benítez, Samanta; Grenier, Cristian; Rodriguez-Navarro, Alejandro B.; García-Herrera, Claudio; Abarca-Ortega, Aldo; Vivanco, Juan F.; Benjumeda, Isabel; Vargas, Cristian A.; Duarte, Cristian; Lardies, Marco A.The exposure to environmental variations in pH and temperature has proven impacts on benthic ectotherms calcifiers, as evidenced by tradeoffs between physiological processes. However, how these stressors affect structure and functionality of mollusk shells has received less attention. Episodic events of upwelling of deep cold and low pH waters are well documented in eastern boundary systems and may be stressful to mollusks, impairing both physiological and biomechanical performance. These events are projected to become more intense, and extensive in time with ongoing global warming. In this study, we evaluate the independent and interactive effects of temperature and pH on the biomineral and biomechanical properties of Argopecten purpuratus scallop shells. Total organic matter in the shell mineral increased under reduced pH (~ 7.7) and control conditions (pH ~ 8.0). The periostracum layer coating the outer shell surface showed increased protein content under low pH conditions but decreasing sulfate and polysaccharides content. Reduced pH negatively impacts shell density and increases the disorder in the orientation of calcite crystals. At elevated temperatures (18 °C), shell microhardness increased. Other biomechanical properties were not affected by pH/temperature treatments. Thus, under a reduction of 0.3 pH units and low temperature, the response of A. purpuratus was a tradeoff among organic compounds (biopolymer plasticity), density, and crystal organization (mineral plasticity) to maintain shell biomechanical performance, while increased temperature ameliorated the impacts on shell hardness. Biopolymer plasticity was associated with ecophysiological performance, indicating that, under the influence of natural fluctuations in pH and temperature, energetic constraints might be critical in modulating the long-term sustainability of this compensatory mechanism.Ítem Resilience of an aquatic macrophyte to an anthropogenically induced environmental stressor in a Ramsar wetland of southern Chile(Ambio, 2019-03-15) Jaramillo, Eduardo; Duarte, Cristian; Labra, Fabio A.; Lagos, Nelson A.; Peruzzo, Bruno; Silva, Ricardo; Velasquez, Carlos; Manzano, Mario; Melnick, DanielIn mid-2004, anthropogenically induced changes in water quality of the Río Cruces wetland, a Ramsar site located in southern Chile (ca. 40°S), enhanced the resuspension of iron-enriched sediments, which were subsequently deposited over the most abundant aquatic macrophyte of the wetland (Egeria densa Planch. 1849). This event triggered the formation of brownish, necrotic patches and increased iron contents in the leaves and stems of E. densa, which contributed to a significant demise of the plant within the wetland. In this study, we estimate the recovery time as a proxy for resilience of this macrophyte at organismal and population levels. Macro- and micro-optical characteristics, as well as iron contents in tissues of E. densa, were documented in four time windows (2004, 2008, 2012, and 2014). In addition, the size of the macrophyte population and its spatial occurrence were monitored from 2008 to 2016 across 36 study sites within the wetland. Our results suggest necrotic patches and high iron contents in E. densa persisted at least until 2008. After 2013, a significant increase in the spatial occurrence of E. densa was observed within the wetland, reaching full recovery of the population during 2015. The health of plant tissues and iron contents in leaves and stems showed recovery period close to 4 years, while the recovery of the spatial occurrence of E. densa took approximately 9 years. While the monitoring of plant health was not performed on a strict annual basis, the recovery rates estimated here are slower than those described for other macrophytes. This finding might reflect the long-lasting effects of the disturbance from 2004 and the interaction with biotic processes, such as foraging by waterbirds recolonizing the Río Cruces wetland. These results show that full recovery of E. densa was achieved through a cascade of effects starting with abiotic factors (water quality) and passing through physiological and individual levels, to finally reach the population level. A key aspect of this response is the invasive nature of the macrophyte, which likely contributed to its recovery as a consequence of improved water quality. Less successful macrophyte species in other systems may not reach the specific population recovery, and become subdominant species instead, or even be eradicated from the wetland either as the result of herbivory or due to competition with other macrophytes.Ítem Species-specific responses to ocean acidification should account for local adaptation and adaptive plasticity(Nature Publishing Group, 2017-03) Vargas, Cristian A.; Lagos, Nelson A.; Lardies, Marco A.; Duarte, Cristian; Manríquez, Patricio H.; Aguilera, Victor M.; Broitman, Bernardo; Widdicombe, Steve; Dupont, SamGlobal stressors, such as ocean acidification, constitute a rapidly emerging and significant problem for marine organisms, ecosystem functioning and services. The coastal ecosystems of the Humboldt Current System (HCS) off Chile harbour a broad physical-chemical latitudinal and temporal gradient with considerable patchiness in local oceanographic conditions. This heterogeneity may, in turn, modulate the specific tolerances of organisms to climate stress in species with populations distributed along this environmental gradient. Negative response ratios are observed in species models (mussels, gastropods and planktonic copepods) exposed to changes in the partial pressure of CO 2 (pCO2) far from the average and extreme pCO2 levels experienced in their native habitats. This variability in response between populations reveals the potential role of local adaptation and/or adaptive phenotypic plasticity in increasing resilience of species to environmental change. The growing use of standard ocean acidification scenarios and treatment levels in experimental protocols brings with it a danger that inter-population differences are confounded by the varying environmental conditions naturally experienced by different populations. Here, we propose the use of a simple index taking into account the natural pCO2 variability, for a better interpretation of the potential consequences of ocean acidification on species inhabiting variable coastal ecosystems. Using scenarios that take into account the natural variability will allow understanding of the limits to plasticity across organismal traits, populations and species. © 2017 Macmillan Publishers Limited, part of Springer Nature. All rights reserved.