Combined effect of pCO2 and temperature levels on the thermal niche in the early benthic ontogeny of a keystone species

Autores:

Manríquez, P., Jara, M., González, C., Díaz, M., Brokordt, K., & Lattuca, M., Peck, M.A., Alter, K., Marras, S., Domenici, P.

Resumen:

We evaluated the effects of projected, near future ocean acidification (OA) and extreme events of temperature (warming or cooling) on the thermal tolerance of Concholepas concholepas, a coastal benthic keystone species. Three separate trials of an experiment were conducted by exposing juvenile C. concholepas for 1 month to one of two contrasting pCO2 levels (~500 and ~1200 μatm). In addition, each pCO2 level was combined with one of four temperature treatments. The control was 15 °C, whilst the other temperatures were 10 °C (Trial 1), 20 °C (Trial 2) and 25 °C (Trial 3). At the end of each trial, we assessed Critical Thermal maximum (CTmax) and min- imum (CTmin) via self-righting success, calculated partial thermal tolerance polygons, measured somatic growth, determined transcription of Heat Shock Proteins 70 (HSP70) and measured oxygen consumption rates. Regardless of pCO2 level, HSP70 transcript levels were significantly higher in juveniles after exposure to extreme temperatures (10 °C and 25 °C) indicating physiological stress. Oxygen consumption rates increased with in- creasing temperature from 10 °C to 20 °C though showed a decrease at 25 °C. This rate was not affected by pCO2 or the interaction between temperature and pCO2. Juveniles exposed to present-day and near future pCO2 levels at 20 °C showed similar thermal tolerance polygonal areas; whilst changes in both CTmin and CTmax at 25 °C and 10 °C caused narrower and broader areas, respectively. Temperature affected growth, oxygen consumption and HSP70 transcription in small juvenile C. concholepas. Exposure to elevated pCO2 did not affect thermal tolerance, growth or oxygen consumption at temperatures within the thermal range normally experi- enced by this species in northern Chile (15-20 °C). At elevated pCO2 conditions, however, exposure to warmer (25 °C) or colder (10 °C) temperatures reduced or increased the thermal area, respectively. This study demon- strates the importance of examining the thermal-tolerance edges to better understand how OA and temperature will combine to physiologically challenge inter-tidal organisms.

Año: 2020

Palabras claves:

pH and other upwelling hydrographic drivers in regulating copepod reproduction during the 2015 El Niño event: A follow-up study

Autores:

Aguilera, V.

Resumen:

The combined upwelling-El Niño (EN) event regulation of the numerically dominant Acartia tonsa (Crustacea, Copepoda) reproduction was examined in a year-round upwelling system (23°S) of the Humboldt Eastern Boundary Upwelling System (EBUS) during the EN 2015. A previous analysis of the environmental regulation of this system is extended here by considering complementary oceanographic information (sea level, stratification indexes) and additional reproductive traits, such as maximum (MaxEPR), median (MedianEPR) and prevalence of egg producing females over a period of six months. Furthermore, field minimum-maximum pH levels were reproduced in three 96-h incubation experiments conducted under variable salinity conditions to evaluate copepod mean EPR, egg size and hatching success. Supporting previous assertions, the warm-high salinity EN 2015 was observed in the study site separately from hydrographic conditions associated with upwelling to non-upwelling regimes. Analysis of similarity-distance (Distance based Linear Model (DistLM)) and normalized data (separate-slope comparison under a General Linear Model (GLM)) showed that reproductive traits were regulated by specific combinations of ambient conditions, and that this regulation was also sensitive to the prevailing hydrographic regime. Thus, upwelling to non-upwelling transitions changing the pH, and EN-associated salinity and stratification shifts, were significantly and strongly linked to almost all reproductive traits (DistLM). Slope comparison (GLM) indicated MaxEPR and MedianEPR variations also underlie the phenology, highlighting the relationship between pH and salinity with biological variations. In conjunction with experimental observations, the current study consistently suggests that pH-variations in the upwelling realm, and EN hydrographic perturbations might underpin responses of plankton populations to climate change in productive EBUS.

Año: 2020

Palabras claves: Eastern boundary upwelling systems, Intra-seasonal variationsInter-annual variations, Ocean acidification, Zooplankton physiology

Antagonistic interplay between pH and food resources affects copepod traits and performance in a year-round upwelling system

Autores:

Aguilera, V., Vargas, C., & Dam, H.

Resumen:

Linking pH/pCO2 natural variation to phenotypic traits and performance of foundational species provides essential information for assessing and predicting the impact of ocean acidification (OA) on marine ecosystems. Yet, evidence of such linkage for copepods, the most abundant metazoans in the oceans, remains scarce, particularly for naturally corrosive Eastern Boundary Upwelling systems (EBUs). This study assessed the relationship between pH levels and traits (body and egg size) and performance (ingestion rate (IR) and egg reproduction rate (EPR)) of the numerically dominant neritic copepod Acartia tonsa, in a year-round upwelling system of the northern (23° S) Humboldt EBUs. The study revealed decreases in chlorophyll (Chl) ingestion rate, egg production rate and egg size with decreasing pH as well as egg production efficiency, but the opposite for copepod body size. Further, ingestion rate increased hyperbolically with Chl, and saturated at ~1 µg Chl. L−1. Food resources categorized as high (H, >1 µg L−1) and low (L, <1 µg L−1) levels, and pH-values categorized as equivalent to present day (≤400 µatm pCO2, pH > 7.89) and future (>400 µatm pCO2, pH < 7.89) were used to compare our observations to values globally employed to experimentally test copepod sensitivity to OA. A comparison (PERMANOVA) test with Chl/pH (2*2) design showed that partially overlapping OA levels expected for the year 2100 in other ocean regions, low-pH conditions in this system negatively impacted traits and performance associated with copepod fitness. However, interacting antagonistically with pH, food resource (Chl) maintained copepod production in spite of low pH levels. Thus, the deleterious effects of ocean acidification are modulated by resource availability in this system.

Año: 2020

Palabras claves: Scientific Reports

Season-dependent effects of ocean warming on the physiological performance of a native and a non-native sea anemone

Autores:

Suárez, J., Hansen, M., Urtubia, U., Lenz, M., Valdivia, N., & Thiel, M.

Resumen:

The effects of ocean warming on the physiological performance of marine organisms have been widely studied. However, few studies have considered the relevance of seasonal acclimation to elevated temperatures and whether native and non-native species have similar tolerances to warming. We tested the hypotheses that the susceptibility to warming in two species of sea anemones from temperate latitudes is (i) higher in winter than in summer, and (ii) higher in the native than in the non-native species. Seasonal variability in the upper thermal tolerance limit of Anthothoe chilensis (native) and Anemonia alicemartinae (non-native) individuals from the northern-central coast of Chile was assessed in laboratory experiments during the austral winter 2015 and summer 2016. In line with our predictions, seawater warming (up to 16 °C above natural levels) significantly suppressed individual performance proxies such as survival and asexual reproduction (longitudinal fission) in the native species, but not in the non-native species. However, asexual reproduction in the non-native sea anemone was rare across warming treatments, and the native species showed a stronger capacity to detach from the substratum under adverse thermal conditions. Negative effects of warming on survival and fission were evident only in winter, when asexual reproduction is more intense in these taxa. Finally, water temperatures of 30 °C or more were lethal for both native and non-native sea anemones. These results show that the non-native species may have a broader thermal tolerance (in terms of survival) than the native taxonomically related species, but the latter displays behavioral adaptations to avoid adverse conditions of high temperatures. We suggest that knowledge about life history traits related to seasonal variations in water temperature and the invasion status of a species can help to predict its performance in a warming ocean.

Año: 2020

Palabras claves: Ocean warming, Thermal tolerance, Seasonality, Anthothoe chilensis, Anemonia alicemartinae

Assessment of Gene Expression Biomarkers in the Chilean Pencil Catfish, Trichomycterus areolatus, from the Choapa River Basin, Coquimbo Chile

Autores:

Ali, J.M., Montecinos, A., Schulze, T.T., Allmon, L.G., Kallenbach, A.T., Watson, G.F., Davis, P.H., Snow, D.D., Bertin, A., Gouin, N., Kolok, A.S.

Resumen:

The objective of this study was to describe changes in the gene expression in the Chilean catfish, Trichomycterus areolatus, based on their geographic location within the Choapa River. Genes of choice included those that are biomarkers of exposure to metals, oxidative stress, and endocrine disruption. Male and female T. areolatus were sampled from four sites in Janu-ary 2015 differently impacted by human activities. In males, but not females, hepatic gene expression of heat shock protein (HSP70) and cytochrome P450 1A (CYP1A) were significantly elevated at the site adjacent to the small city of Salamanca, relative to the other sites. In females, hepatic HSP70, the aryl hydrocarbon receptor (AHR), and the estrogen responsive genes, vitellogenin (VTG) and estrogen receptor alpha (ERα), were significantly lower at the site located furthest downstream. A similar downstream pattern of lower expression levels also was found in ovarian tissue for the genes, HSP70 and ERα. Gill gene expression showed a unique pattern in females as levels of metallothionein were elevated at the site furthest downstream. While analytical chemistry of water samples provided limited evidence of agrichemical contamination, the gene expression data are consistent with an exposure to agrichemicals and metals. T. areolatus may be a valuable sentinel organism and its use as a bioindicator species in some rivers within Chile can provide considerable insight, particularly in situations analytical chemistry is limited by environmental constraints.

Año: 2019

Palabras claves:

Using remote sensing to detect whale strandings in remote areas: The case of sei whales mass mortality in Chilean Patagonia

Autores:

Fretwell, P., Jackson, J., Ulloa Encina, M., Häussermann, V., Perez Alvarez, M., Olavarría, C., & Gutstein, C.

Resumen:

We test the ability of Very High Resolution satellite (VHR) imagery to detect stranded whales using both manual and automated methods. We use the 2015 mass mortality event in the Gulf of Penas locality, central Patagonia, Chile, as an initial case study. This event was the largest known mass mortality of baleen whales, with at least 343 whales, mainly sei whales (Balaenoptera borealis), documented as stranding. However, even with such a large number of whales, due to the remote location of the gulf the strandings went unrecorded for several weeks. Aerial and boat surveys of the area were conducted two to four months after the mortality event. In this study we use 50cm resolution WorldView2 imagery to identify and count strandings from two archival images acquired just after the stranding event and two months before the aerial and ground surveys, and to test manual and automated methods of detecting stranded whales. Our findings show that whales are easily detected manually in the images but due to the heterogeneous colouration of decomposing whales, spectral indices are unsuitable for automatic detection. Our satellite counts suggest that, at the time the satellite images were taken, more whales were stranded than recorded in the aerial survey, possibly due to the non-comprehensive coverage of the aerial survey or movement of the carcases between survey acquisition. With even higher resolution imagery now available, satellite imagery may be a cost effective alternative to aerial surveys for future assessment of the extent of mass whale stranding events, especially in remote and inaccessible areas.

Año: 2019

Palabras claves: Whales, Islands, Image analysis, Boats, Beaches, Remote areas, Geological surveys, Marine mammals

Seasonal variability of the southern tip of the Oxygen Minimum Zone in the eastern South Pacific (30°-38°S): A modeling study.

Autores:

Pizarro‐Koch, M., Pizarro, O., Dewitte, B., Montes, I., Ramos, M., Paulmier, A., & Garçon, V.

Resumen:

We investigate the seasonal variability of the southern tip (30°–38°S) of the eastern South Pacific oxygen minimum zone (OMZ) based on a high horizontal resolution (1/12°) regional coupled physical‐biogeochemical model simulation. The simulation is validated by available in situ observations and the OMZ seasonal variability is documented. The model OMZ, bounded by the contour of 45 μM, occupies a large volume (4.5x104 km3) during the beginning of austral winter and a minimum (3.5x104 km3) at the end of spring, just 1 and 2 months after the southward transport of the Peru‐Chile Undercurrent (PCUC) is maximum and minimum, respectively. We showed that the PCUC significantly impacts the alongshore advection of dissolved oxygen (DO) modulating the OMZ seasonal variability. However, zonal transport of DO by meridionally alternating zonal jets and mesoscale eddy fluxes play also a major role in the seasonal and spatial variability of the OMZ. Consistently, a DO budget analysis reveals a significant contribution of advection terms to the rate of change of DO and the prominence of mesoscale variability within the seasonal cycle of these terms. Biogeochemical processes and horizontal and vertical mixing, associated with subgrid scale processes, play only a secondary role in the OMZ seasonal cycle. Overall, our study illustrates the interplay of mean and (mesoscale) eddy‐induced transports of DO in shaping the OMZ and its seasonal cycle off Central Chile.

Año: 2019

Palabras claves: Oxygen minimum zone, Eddy fluxes, Peru‐Chile Undercurrent, Oxygen budget, Eastern South Pacific

The rise and demise of plastic shopping bags in Chile – Broad and informal coalition supporting ban as a first step to reduce single-use plastics

Autores:

Amenábar Cristi, M., Holzapfel, C., Nehls, M., De Veer, D., Gonzalez, C., & Holtmann, G., Honorato-Zimmer, D., Kiessling, T., Leyton Munoz, A., Narvaez Reyes, S., Nunez, P., Sepulveda, J.M., Vásquez, N., Thiel, M.

Resumen:

Single-use plastic bags (SUPBs) were introduced to society as a way to facilitate our daily lives, but due to their low post-use value they are found as litter in many different environments, from urban to rural and remote, natural environments. Given the increasing awareness about environmental litter, many communities have banned SUPBs in the recent past. Here we explore an emerging economy to document the rise and demise of SUPBs in society. Through a review of scientific and grey literature (including governmental documents and media coverage) we reconstruct the timeline of SUPBs in Chile, including the development of the plastic industry and retail business within Chile, the introduction, spread and finally the demise of SUPBs. Focused on the demise phase, we document the creation and succession of municipal ordinances to reduce SUPBs in local commerce, and the development of a national law to regulate the use of SUPBs. In order to document the involvement of the general public during the demise phase, we also examined current behavior and behavioral intentions of people in (i) a local project introducing reusable cloth bags to reduce the use of SUPBs, and (ii) a consumer survey about public perception of SUPBs and their use. Plastic bags were introduced in Chile in the 1970s, then spread with the emergence of supermarkets and retail stores in the 1980s and 1990s, and were widely used in commerce by the turn of the century. During the first decade of the 21st century the first scientific studies reported large amounts of plastic litter and high proportions of single-use plastics in coastal environments, public awareness grew, and numerous initiatives aiming to reduce consumption and littering of plastics developed. The first municipal ban of SUPBs in 2013 was emulated during the following five years by 62 other Chilean municipalities and in 2018 translated into a national law, which was highly approved and supported by the population. We conclude that the ban of SUBPs in Chile was facilitated by a broad concern among the general public, which led to a bottom-up movement culminating in the national government taking stakes in the issue. Finally, we argue that this can only be a first step that must be followed by further actions to abolish single-use products in order to effectively protect the environment and in particular the world's oceans.

Año: 2019

Palabras claves: Marine litter, Willingness to engage, Socio-economic factors, Pro-environmental behavior, Waste management.

Seasonal Variability of the Southern Tip of the Oxygen Minimum Zone in the Eastern South Pacific (30°‐38°S): A Modeling Study

Autores:

Pizarro‐Koch, M., Pizarro, O., Dewitte, B., Montes, I., Ramos, M., Paulmier, A., & Garçon, V.

Resumen:

We investigate the seasonal variability of the southern tip (30°–38°S) of the eastern South Pacific oxygen minimum zone (OMZ) based on a high horizontal resolution (1/12°) regional coupled physical‐biogeochemical model simulation. The simulation is validated by available in situ observations and the OMZ seasonal variability is documented. The model OMZ, bounded by the contour of 45 μM, occupies a large volume (4.5x104 km3) during the beginning of austral winter and a minimum (3.5x104 km3) at the end of spring, just 1 and 2 months after the southward transport of the Peru‐Chile Undercurrent (PCUC) is maximum and minimum, respectively. We showed that the PCUC significantly impacts the alongshore advection of dissolved oxygen (DO) modulating the OMZ seasonal variability. However, zonal transport of DO by meridionally alternating zonal jets and mesoscale eddy fluxes play also a major role in the seasonal and spatial variability of the OMZ. Consistently, a DO budget analysis reveals a significant contribution of advection terms to the rate of change of DO and the prominence of mesoscale variability within the seasonal cycle of these terms. Biogeochemical processes and horizontal and vertical mixing, associated with subgrid scale processes, play only a secondary role in the OMZ seasonal cycle. Overall, our study illustrates the interplay of mean and (mesoscale) eddy‐induced transports of DO in shaping the OMZ and its seasonal cycle off Central Chile.

Año: 2019

Palabras claves: Oxygen minimum zone, Eddy fluxes, Peru‐Chile Undercurrent, Oxygen budget, Eastern South Pacific

Multiple reproductive modes of Myrcianthes coquimbensis (Myrtaceae), an endangered shrub endemic to the Atacama Desert

Autores:

García-Guzmán, P., Loayza, A., & Squeo, F.

Resumen:

Many plants can produce seeds via multiple reproductive modes, such as selfing and outcrossing. Having multiple reproductive modes can be advantageous if it assures seed production when outcrossing fails, which is important for species inhabiting environments where pollinators are scarce or variable. However, it can also be disadvantageous due to the fitness costs associated to selfing. Consequently, plants have mechanisms to reduce the incidence of selfing. Here we examined the breeding system of Myrcianthes coquimbensis; this threatened Atacama Desert shrub is the last species to bloom in the community and exhibits low visitation rates per flower because pollinators are less abundant. Our aim was to determine whether this plant can produce fruits by modes other than outcrossing, and whether it possesses floral traits to prevent sexual interference. We conducted experimental flower treatments in two localities to determine whether fruits were produced by outcrossing, selfing, autonomous selfing and agamospermy. We also evaluated stigma receptivity and pollen viability during a flower’s lifespan. M. coquimbensis developed fruits and seeds by all the reproductive modes assessed, including selfing and agamospermy. Flowers presented partial segregation of sexual functions, with the peak of pollen viability occurring before the peak of stigma receptivity. Selfing is unavoidable in M. coquimbensis and likely interferes with outcrossing. Coupled with possible early inbreeding depression, it probably results in a cost for seed production. Our results suggest that this species may be vulnerable in scenarios where pollinators are scarce; however, agamospermy may provide an alternative route of seed production in these scenarios.

Año: 2020

Palabras claves: Breeding system, Agamospermy, Selfing, Mix-Mating, Protandry, Reproductive assurance, Sexual interference.