Diversification dynamics, species sorting, and changes in the functional diversity of marine benthic gastropods during the Pliocene-Quaternary at temperate western South America
Rivadeneira, M. M., & Nielsen, S. N.
Functional diversity based on species traits is a powerful tool to investigate how changes in species richness and composition affect ecosystem functioning. However, studies aimed at understanding changes in functional diversity over large temporal and spatial scales are still scant. Here we evaluate the combined effect of diversification and species sorting on functional diversity of fossil marine gastropods during the Pliocene-Quaternary transition in the Pacific coast of South America. We analyzed a total of 172 species in 29 Pliocene and 97 Quaternary sites. Each species was characterized according to six functional traits: body size, feeding type, mobility, attachment, life-habit, and larval mode. Functional diversity was estimated according to four indexes (functional richness, evenness, divergence and dispersion) based on functional traits measured. Extrapolated species richness showed a slight yet not significant decrease from the Pliocene to the Quaternary despite the fact that a large faunal turnover took place; furthermore, a large extinction of Pliocene species (61–76%) was followed by a high pulse of appearances (49–56%) during the Quaternary. Three out of four indices of functional diversity (evenness, divergence and dispersion) increased significantly towards the Quaternary which is more than expected under a random turnover of species. The increase in functional diversity is associated with a loss of large-sized carnivore forms, which tended to be replaced by small-sized grazers. Hence, this trait-selective species turnover, even in the absence of significant changes in species richness, likely had a large effect and has shaped the functional diversity of present-day assemblages.
Palabras claves: Species diversity, Species extinction, Pliocene epoch, Physiological parameters, Gastropods, Biodiversity, Malacology, Marine fossils
Holocene tephrochronology of the lower Río Cisnes valley, southern Chile
Weller, D. J., de Porras, M. E., Maldonado, A., Méndez, C., & Stern, C. R.
Sediment cores from lakes and bogs in the Río Cisnes valley contain tephra from explosive eruptions of volcanoes in the southern part of the Andean Southern Volcanic Zone (SSVZ). These tephra, which thicken and coarsen to the west, are attributed to eruptions from Melimoyu, Mentolat, Hudson, and potentially either Macá, Cay or one of the many minor eruptive centers (MEC) located both along the Liquiñe-Ofqui Fault Zone (LOFZ) and surrounding the major volcanoes. Correlation of the tephra between two new cores in the lower Río Cisnes valley, and amongst other cores previously described from the region, and source volcano identification for the tephra, has been done using lithostratigraphic data (tephra layer thickness and grain size), petrography (tephra glass color, vesicle morphology, and type and abundance of phenocryst phases), and by comparison of bulk tephra trace-element characteristics with previously published whole-rock and bulk tephra chemical analysis. Four tephras in these cores are attributed to eruptions of Mentolat, four to eruptions from Melimoyu, one possibly to Hudson, and six cannot be assigned to a specific source volcano. Some of these tephra correspond to pyroclastic tephra fall deposits previously observed in outcrop, including the MEL2 eruption of Melimoyu and the MEN1 eruption of Mentolat. However, others have not been previously observed and represent the products of newly identified small to medium sized eruptions from volcanoes of the SSVZ. These results provide new information concerning the frequency and magnitude of explosive eruption of SSVZ volcanoes and contribute to the evaluation of volcanic hazards in the region.
Palabras claves: Andean volcanism; Tephra; Tephrochronology; Chile
The combined effects of ocean warming and acidification on shallow-water meiofaunal assemblages
Lee, M. R., Torres, R., & Manríquez, P. H.
Climate change due to increased anthropogenic CO2 in the atmosphere is causing an increase in seawater temperatures referred to as ocean warming and a decrease in seawater pH, referred to as ocean acidification. The meiofauna play an important role in the ecology of marine ecosystems and the functions they provide. Using microcosms, meiofaunal assemblages were exposed to two temperatures (15 and 19 °C) and two pHs (pCO2 of 400 and 1000 ppm), both individually and in combination, for a period of 90 days. The hypothesis that increased temperature will increase meiofaunal abundance was not supported. The hypothesis that a reduced pH will reduce meiofaunal abundance and species richness was supported. The combination of future conditions of temperature and pH (19 °C and pCO2 of 1000 ppm) did not affect overall abundance but the structure of the nematode assemblage changed becoming dominated by a few opportunistic species.
Palabras claves: Meiofauna, Nematodes, Ocean warming, Ocean acidification, Microcosms, Chile
Microplastic sampling with the AVANI trawl compared to two neuston trawls in the Bay of Bengal and South Pacific
Eriksen, M., Liboiron, M., Kiessling, T., Charron, L., Alling, A., Lebreton, L., Richards, H., Roth, B., Ory, N.C., Hidalgo-Ruz, V., Meerhoff, E., Box, C., Cummins, A., & Thiel, M.
Many typical neuston trawls can only be used during relatively calm sea states and slow tow speeds. During two expeditions to the Bay of Bengal and the eastern South Pacific we investigated whether the new, high-speed AVANI trawl (All-purpose Velocity Accelerated Net Instrument) collects similar amounts and types of microplastics as two established scientific trawl designs, the manta trawl and the DiSalvo neuston net. Using a 335 μm net, the AVANI trawl can collect microplastics from the sea surface at speeds up to 8 knots as it “skis” across the surface, whereas the manta and DiSalvo neuston trawls must be towed slowly in a less turbulent sea state and often represent shorter tow lengths. Generally, the AVANI trawl collected a greater numerical abundance and weight of plastic particles in most size classes and debris types than the manta trawl and DiSalvo neuston net, likely because these trawls only skim the surface layer while the AVANI trawl, moving vertically in a random fashion, collects a “deeper” sample, capturing the few plastics that float slightly lower in the water column. However, the samples did not differ enough that results were significantly affected, suggesting that studies done with these different trawls are comparable. The advantage of the AVANI trawl over traditional research trawls is that it allows for collection on vessels underway at high speeds and during long transits, allowing for a nearly continuous sampling effort over long distances. As local surface currents make sea surface abundance widely heterogeneous, widely spaced short-tow trawls, such as the manta and DiSalvo trawls, can catch or miss hotspots or meso-scale variability of microplastic accumulations, whereas the AVANI trawl, if utilized for back-to-back tows of intermediate distances (5–10 km), can bridge variable wind conditions and debris concentrations potentially reducing variance and provide a greater resolution of spatial distribution.
Palabras claves: Plastic pollution, Marine debris, Microplastics, Bay of Bengal, South Pacific Gyre, Trawl comparison, Validation, Neuston trawls, AVANI trawl
Interactions between kelp spores and encrusting and articulated corallines: recruitment challenges for Lessonia spicata
Parada, G. M., Martínez, E. A., Aguilera, M. A., Oróstica, M. H., & Broitman, B. R.
Intertidal kelps like Lessonia spicata (Laminariales) dominate low intertidal habitats, where they coexist with morphologically diverse coralline seaweeds. We show that crustose and articulated coralline algae have contrasting effects on the settlement and recruitment of this kelp species. Crustose coralline algae significantly inhibited the settlement of kelp spores, while they readily settled on the genicula of articulated coralline algae. This pattern was observed both in laboratory experiments and in field experiments conducted in the low intertidal zone at three locations. Field surveys confirmed that L. spicata juveniles were significantly more likely to be found on articulated corallines than on crustose corallines. This pattern held in field surveys at 10 sites, where primary space occupancy of L. spicata showed a significant negative correlation with the cover of crustose coralline algae in 3 out of 4 years, across all sites. Our results provide an important ecological clue to the processes determining recruitment limitation for ecologically and economically important seaweeds, and support conservation and management actions.
Palabras claves: Facilitation; Intertidal kelps; Seaweed interactions; Spore settlement
Benthic communities under anthropogenic pressure show resilience across the Quaternary
Martinelli, J. C., Soto, L. P., González, J., & Rivadeneira, M. M.
The Southeast Pacific is characterized by rich upwelling systems that have sustained and been impacted by human groups for at least 12 ka. Recent fishing and aquaculture practices have put a strain on productive coastal ecosystems from Tongoy Bay, in north-central Chile. We use a temporal baseline to determine whether potential changes to community structure and composition over time are due to anthropogenic factors, natural climatic variations or both. We compiled a database (n = 33 194) with mollusc species abundances from the Mid-Pleistocene, Late Pleistocene, Holocene, dead shell assemblages and live-sampled communities. Species richness was not significantly different, neither were diversity and evenness indices nor rank abundance distributions. There is, however, an increase in relative abundance for the cultured scallop Argopecten, while the previously dominant clam Mulinia is locally very rare. Results suggest that impacts from both natural and anthropogenic stressors need to be better understood if benthic resources are to be preserved. These findings provide the first Pleistocene temporal baseline for the south Pacific that shows that this highly productive system has had the ability to recover from past alterations, suggesting that if monitoring and management practices continue to be implemented, moderately exploited communities from today have hopes for recovery.
Palabras claves: Conservation palaeobiology, Molluscs, Aquaculture, Overfishing, Temporal baseline, South Pacific
Development and characterization of the first 16 microsatellites loci for Panulirus pascuensis (Decapoda: Palinuridae) from Easter Island using Next Generation Sequencing
Díaz-Cabrera, E., Meerhoff, E., Rojas-Hernandez, N., Vega-Retter, C., & Veliz, D.
The spiny lobster Panulirus pascuensis stands out among the endemic species of Easter Island, due to its cultural and economic importance. A total of 16 microsatellite loci were characterized in 18 individuals, 9 of which were polymorphic. The mean number of alleles per locus was 3.44 (2-6) and the observed heterozygosity ranged from 0.11 to 0.93. None of the loci exhibited significant linkage disequilibrium or departures from HWE. These new microsatellites will be used to obtain information about migration, population structure and genetic diversity of P. pascuensis in order to improve the future sustainable management and conservation plans.
Palabras claves: Panulirus pascuensis, Easter Island, Microsatellite, Genetic marker
Characterizing stream‐aquifer exchanges with self‐potential measurements
Valois, R., Cousquer, Y., Schmutz, M., Pryet, A., Delbart, C., & Dupuy, A.
Characterizing the interactions between streams and aquifers is a major challenge in hydrology. Electrical self‐potential (SP) is sensitive to groundwater flow through the electrokinetic effect, which is proportional to Darcy velocity. SP surveys have been extensively used for the characterization of seepage flow in a variety of contexts. But to our knowledge, a model coupling SP and groundwater flow has never been implemented for the study of stream‐aquifer interactions. To address the issue, we first implemented a two‐dimensional model to a synthetic stream‐aquifer cross section. Results underline the very distinct nature of SP profiles in gaining or losing stream conditions. Second, we presented a field application in a transect crossing a stream in losing conditions. The coupled model successfully reproduced the observed SP profile. This inverse modeling of the SP signal provides quantitative data on hydrodynamic parameters (hydraulic conductivity, hydraulic heads) and geophysical parameters (coupling coefficient). Nevertheless, all relevant parameters cannot be uniquely estimated without precise prior information on at least some of these parameters. Our results confirm the potential of SP surveys on the characterization of stream‐aquifer exchanges. Recommendations on the collection of high‐quality data are also provided, along with a description of the contexts in which the methodology is likely to perform well.
First insight into the heritable variation of the resistance to infection with the bacteria causing the withering syndrome disease in Haliotis rufescens abalone
Brokordt, K., González, R., Farías, W., Winkler, F. E., & Lohrmann, K. B.
Withering syndrome disease has experienced worldwide spread in the last decade. This fatal disease for abalone is produced by a rickettsia-like organism (WS-RLO), the bacterium “Candidatus Xenohaliotis californiensis”. To evaluate the potential of the red abalone (Haliotis rufescens) to improve its resistance to infection by WS-RLO, the additive genetic component in the variation of this trait was estimated. For this, the variation in infection intensity with WS-RLOs and WS-RLOv (phage-infected RLOs) was analyzed in 56 families of full-sibs maintained for three years in a host-parasite cohabitation aquaculture system. A WS-RLO prevalence of 65% was observed in the analysed population; and from the total WS-RLO inclusions 60% were hyperparasited with the phage (WS-RLOv). The decrease in the food ingestion rate was the sole negative effect associated with increasing WS-RLO intensity of infection, suggesting that the high level of WS-RLOv load may have diminished the symptoms of WS disease in the analyzed abalones. The estimated heritabilities were moderate to mid, but significant, varying from 0.21 to 0.23 and 0.36 for WS-RLO and WS-RLOv infections, respectively. This suggests that variation in resistance to infection with WS-RLO may respond to selection in the evaluated red abalone population. Estimated response to selection (G) for the level of infection by WS-RLO indicated that if the 10% of red abalone with the lowest infection level is selected as broodstock, a 90% reduction in the intensity of infection in the progeny can be expected, even with the lowest estimation of heritability (h2 = 0.21). This strong response would be also due to the large phenotypic variance of this trait. Strong positive correlations, both phenotypic and genotypic, were observed between infection intensities with WS-RLO and WS-RLOv, indicating that selection to increase resistance to one of the types of RLOs will affect resistance in the other in the same direction. This is the first study that demonstrates the existence of additive genetic variation for resistance to WS-RLO in abalone. Consequently, it is possible to increase the resistance to WS-RLO in H. rufescens by selective breeding, which can be an economically attractive and environmentally friendly manner to reduce mortalities and growth effects caused by WS in abalone farms.
Palabras claves: Withering syndrome, Heritability, WS-RLO infection, Phage-infected WS-RLOs, Disease resistance, Abalone
An unusual kind of diurnal streamflow variation
Cuevas, J. G., Arumí, J. L., Zúñiga-Feest, A., & Little, C.
During hydrological research in a Chilean swamp forest, we noted a pattern of higher streamflows close to midday and lower ones close to midnight, the opposite of an evapotranspiration (Et)-driven cycle. We analyzed this diurnal streamflow signal (DSS), which appeared mid-spring (in the growing season). The end of this DSS coincided with a sustained rain event in autumn, which deeply affected stream and meteorological variables. A survey along the stream revealed that the DSS maximum and minimum values appeared 6 and 4 hours earlier, respectively, at headwaters located in the mountain forests/ plantations than at the control point in the swamp forest. Et in the swamp forest was higher in the morning and in the late afternoon, but this process could not influence the groundwater stage. Trees in the mountain headwaters reached their maximum Ets in the early morning and/or close to midday. Our results suggest that the DSS is a wave that moves from forests high in the mountains towards lowland areas, where Et is decoupled from the DSS. This signal delay seems to convert the link between streamflow and Et in an apparent, but spurious positive relationship. It also highlights the role of landscape heterogeneity in shaping hydrological processes.
Palabras claves: Evapotranspiration; Groundwater; Riparian zones; Streamflow; Swamp forests