Northern-central Chile Research Articles

Sexual dimorphism and reproductive strategy of the kelp-dwelling isopod Amphoroidea typa (Isopoda, Sphaeromatidae)

Abstract Sexual dimorphism and the reproductive strategy of the isopod Amphoroidea typa were examined and compared with other species from the isopod family Sphaeromatidae. We analyzed populations of A. typa occurring on the kelps Lessonia spp. and Macrocystis pyrifera at six locations on the coast of northern-central Chile. Males could be clearly distinguished from females starting at total body lengths (TL) ⩾ 14 mm, taking as criteria the presence of reproductive appendages and the development of gonopods in males. Females reached substantially larger sizes (up to 22.20 mm) than males (up to 18.25 mm), confirming the existence of sexual size dimorphism in A. typa. Although females had developed oostegites at lengths ⩾ 14 mm TL, only the largest females (⩾17 mm TL) were ovigerous. This suggests that female A. typa reproduce once before dying. At most study sites there were more adult females than males occurring on Lessonia spp., while males dominated on M. pyrifera. Some A. typa individuals had white stripes present on the dorsal part of the pereon, a colour polymorphism apparently independent of the sex of the isopods but becoming more frequent in large individuals, suggesting high predation pressure and that individuals with these stripes have higher survival rates. The results of this study confirm sexual size dimorphism in A. typa, which appears to be a semelparous species. A comparison with other sphaeromatid species indicates that the evolution of semelparity is unrelated to body size, but might be more common in species from habitats with high predation pressure.

Consequences of Land Use Changes on Native Forest and Agricultural Areas in Central-Southern Chile during the Last Fifty Years

Chile’s central-south region has experienced significant land use changes in the past fifty years, affecting native forests, agriculture, and urbanization. This article examines these changes and assesses their impact on native forest cover and agricultural land. Agricultural data for Chile (1980–2020) were obtained from public Chilean institutions (INE and ODEPA). Data on land use changes in central and south Chile (1975–2018), analysed from satellite images, were obtained from indexed papers. Urban area expansion in Chile between 1993 and 2020 was examined using publicly available data from MINVIU, Chile. Additionally, photovoltaic park data was sourced from SEA, Chile. Field crop coverage, primarily in central and southern Chile, decreased from 1,080,000 ha in 1980 to 667,000 ha in 2020, with notable decreases observed in cereal and legume crops. Conversely, the coverage of export-oriented orchards and vineyards increased from 194,947 ha to 492,587 ha. Forest plantations expanded significantly, ranging from 18% per decade in northern central Chile to 246% in the Maule and Biobío regions. This was accompanied by a 12.7–27.0% reduction per 10 years in native forest. Urban areas have experienced significant growth of 91% in the last 27 years, concentrated in the Mediterranean climate region. Solar photovoltaic parks have begun to increasingly replace thorn scrub (Espinal) and agricultural land, mirroring transformations seen in other Mediterranean nations like Spain and Portugal.

Effects of brine discharges on newly hatched larvae of the rocky-shore keystone gastropod Concholepas concholepas

In response to drought challenges in Chile, desalination plants are becoming crucial. Consequently, the implementation of more osmosis reverse desalination plants in central-northern Chile has been promoted, but the consequences of brine discharges on local organisms are largely unknown. The Chilean abalone (Concholepas concholepas) represent the most economically important marine resource exploited along the Chilean coast. In this study, newly hatched larvae of C. concholepas were used to investigate the effects of brine discharges of a reverse osmosis desalination plant on coastal organisms. Under laboratory conditions, larvae were exposed to various dilutions of a brine to assess the consequences on lethal (survival) and sublethal (swimming performance and metabolism) traits. The results indicated that brine discharges had no effects on larval survival. However, undiluted brines (ca. 56 PSU) and salinities above 38 PSU led to increased metabolic rates and a reduction in the swimming performance of the larvae. We suggest mitigating the negative effects of brines on newly hatched C. concholepas larvae by situating discharge points in highly hydrodynamic zones or as far as possible from mating and larval hatching areas. Additionally, we recommended using diffusers to enhance mixing and dilute brine to sub-lethal levels (below 48 PSU).

Insects associated to ephemeral pools in Huentelauquén (29ºS Coquimbo Region, Chile).

In northern central Chile, ephemeral pools constitute shallow isolated water bodies with a favourable habitat for fauna adapted to seasonal changes. Based on the limited knowledge about the fauna-particularly insects-associated to these ecosystems, the objective of this study was to characterize the richness, composition, structure and similarity of the insect communities associated with ephemeral pools in Huentelauquén (29º S, Coquimbo Region, Chile). By using pitfall traps, 10,762 individuals were captured, represented by 7 orders, 27 families, and 51 species. Coleoptera and Hymenoptera were the best represented orders, with Neuroptera, Orthoptera and Plecoptera being poorly represented groups. The non-parametric estimators evaluated showed wealth values above those observed for all the studied pools, and their accumulation curves suggest the existence of an incomplete species inventory in the studied community. Additionally, the hierarchical and ordering analysis showed groupings of pools located in the northwest and southeast of Huentelauquén. Preliminarily we found a negative correlation between the area of the pools and the richness (species) and abundance of insects. Additional studies (on other arthropod groups and other seasons of the year) could provide a better understanding of the local processes of extinction and colonization of the species inhabiting these fragile coastal environments.

CMIP6 precipitation and temperature projections for Chile

AbstractPrecipitation and near-surface temperature from an ensemble of 36 new state‐of‐the‐art climate models under the Coupled Model Inter‐comparison Project phase 6 (CMIP6) are evaluated over Chile’s climate. The analysis is focused on four distinct climatic subregions: Northern Chile, Central Chile, Northern Patagonia, and Southern Patagonia. Over each of the subregions, first, we evaluate the performance of individual global climate models (GCMs) against a suit of precipitation and temperature observation-based gridded datasets over the historical period (1986–2014) and then we analyze the models’ projections for the end of the century (2080–2099) for four different shared socioeconomic pathways scenarios (SSP). Although the models are characterized by general wet and warm mean bias, they reproduce realistically the main spatiotemporal climatic variability over different subregions. However, none of the models is best across all subregions for both precipitation and temperature. Moreover, among the best performing models defined based on the Taylor skill score, one finds the so-called “hot models” likely exhibiting an overestimated climate sensitivity, which suggests caution in using these models for accessing future climate change in Chile. We found robust (90% of models agree in the direction of change) projected end-of-the-century reductions in mean annual precipitation for Central Chile (~ − 20 to ~ − 40%) and Northern Patagonia (~ − 10 to ~ − 30%) under scenario SSP585, but changes are strong from scenario SSP245 onwards, where precipitation is reduced by 10–20%. Northern Chile and Southern Patagonia show non-robust changes in precipitation across the models. Yet, future near-surface temperature warming presented high inter-model agreement across subregions, where the greatest increments occurred along the Andes Mountains. Northern Chile displays the strongest increment of up to ~ 6 °C in SSP585, followed by Central Chile (up to ~ 5 °C). Both Northern and Southern Patagonia show a corresponding increment by up to ~ 4 °C. We also briefly discuss about the environmental and socio-economic implications of these future changes for Chile.

Spatial distribution of microplastics in a coastal upwelling region: Offshore dispersal from urban sources in the Humboldt Current System

In coastal waters, higher concentrations of microplastics (MPs) are generally related to densely populated and industrialized areas, but intense upwelling and offshore transport in the Eastern Boundary Upwelling Systems (EBUS) may influence this pattern. The Humboldt Current System (HCS) along the coast of northern-central Chile represents a perfect model to test whether the abundance of MP at the sea surface decreases with distance from land-based sources, e.g., river mouths, harbors, and submarine wastewater outfalls. The sea surface was sampled with a manta trawl to examine the abundance, composition, and distribution of floating MPs, and Generalized Additive Mixed Models (GAMMs) were performed to examine the relationship between MP abundance (particles km−2) and the distance to putative sources. MPs were found in all 57 net tows, with an average of ⁓120,000 MP km−2 and maximum values of ⁓1,500,000 MP km−2. The composition of MPs was dominated by fragments (>50% of the total count) and over 80% of all MPs were ≥1 mm. The combined effect of the various sources, spatially concentrated in urban areas, makes it difficult to distinguish their relative contributions, but the MP composition suggested that rivers are more important sources, followed by submarine wastewater outfalls and then harbors. A significant and steep negative relationship with the “distance to source” explained 15.2% of the variance of “MP abundance”, suggesting rapid offshore displacement within the HCS. This is the first study to report this pattern along the edges of the South Pacific Subtropical Gyre (SPSG), revealing that continuous offshore transport of microplastic from land-based sources is occurring over large scales and contributing to the accumulation of microplastics in the center of the SPSG. However, the findings additionally suggested that processes at meso- and submeso-spatial scales (driven by geographic and seasonal variables) are disrupting the general pattern.

Species delimitation in a recently diverged species complex of Eryngium (Apiaceae: Saniculoideae) from the Chilean Mediterranean and the Atacama Desert: morphological, environmental and molecular coalescent-based analyses

Abstract The Eryngium anomalum species complex comprises a group of annual herbs that are found in coastal areas of central-northern Chile which diverged during the Quaternary. According to current taxonomy, this complex comprises two distinct species. However, variation in their fruits suggests the presence of a hitherto undetected species. To improve our understanding of speciation processes in the complex, we follow an integrative approach using morphological, geographical, climatic and molecular data. Quantitative morphological, bioclimatic and topographic variables were analysed using uni- and multivariate statistics, and DNA sequence data from plastid and nuclear genomes using phylogenetic and coalescent-based methods. Geographical data were mapped with QGIS. The recognition of three different species in the complex is supported, one of which is new: Eryngium atacamense. These species diverged during the Quaternary in the Chilean Mediterranean and the Atacama Desert and differ in morphology, geographical distribution and climatic niche. They also show strong genetic structure as three independent lineages. Geographically and ecologically divergent habitats, mainly with different degrees of aridity, probably acted as drivers for speciation of three lineages of the E. anomalum complex during the Quaternary in the Chilean Mediterranean bioclimate.

The ENSO-induced South Pacific Meridional Mode

Previous studies have investigated the role of the Pacific meridional mode (PMM), a climate mode of the mid-latitudes in the Northern and Southern Hemisphere, in favoring the development of the El Niño Southern Oscillation (ENSO). However little is known on how ENSO can influence the development of the PMM. Here we investigate the relationship between ENSO and the South Pacific Meridional Mode (SPMM) focusing on strong SPMM events that follows strong El Niño events. This type of events represents more than 60% of such events in the observational record and the historical simulations of the CESM Large ensemble (CESM-LE). It is first shown that such a relationship is rather stationary in both observations and the CESM-LE. Our analyses further reveal that strong SPMM events are associated with a coastal warming off northern central Chile peaking in Austral winter resulting from the propagation of waves forced at the equator during the development of El Niño events. The time delay between the ENSO peak (Boreal winter) and this coastal warming (Austral winter) can be understood in terms of the differential contribution of the equatorially-forced propagating baroclinic waves to the warming along the coast. In particular, the difference in phase speeds of the waves (the high-order mode the wave the slower) implies that they do not overlap along their propagation south of 20°S. This contributes to the persistence of warm coastal SST anomalies off Central Chile until the Austral summer following the concurrent El Niño event. This coastal warming is favorable to the development of strong SPMM events as the South Pacific Oscillation become active during that season. The analysis of the simulations of the Coupled Intercomparison Project phases 5 and 6 (CMIP5/6) indicates that very few models realistically simulate this ENSO/SPMM relationship and associated oceanic teleconnection.

Independent Effects of Species Removal and Asynchrony on Invariability of an Intertidal Rocky Shore Community

Ecological stability depends on interactions between different levels of biological organization. The insurance effects occur when increasing species diversity leads to more temporally invariable (i.e., more stable) community-level properties, due in part to asynchronous population-level fluctuations. While the study of insurance effects has received considerable attention, the role of dominant species that contribute with particular functional traits across different level of organizations is less understood. Using a field-based manipulative experiment, we investigated how species richness and different types of parameters at the population level, such as the invariability of dominants, population invariability, and population asynchrony, influence the community invariability. The experiment involved the repetitive removal of the canopy forming algaMazzaella laminarioides(hereafter “Mazzaella”) during 32 months in two rocky intertidal sites of northern-central Chile. We predicted that the invariability of dominants enhances community invariability, that the effect of multispecies population-level parameters on community invariability are dependent on species richness, and that subdominant algae are unable to fully compensate the loss of canopies of the dominant species. Biomass of algae and mobile invertebrates was quantified over time. We observed independent effects ofMazzaellaremoval and community-wide asynchrony on community invariability. While canopy removal reduced community invariability, population asynchrony boosted community invariability regardless of the presence of canopies. In addition, filamentous and foliose algae were unable to compensate the loss of biomass triggered by the experimental removal ofMazzaella. Canopy removal led to a severe decrement in the biomass of macrograzers, while, at the same time, increased the biomass of mesograzers. Asynchrony stemmed from compensatory trophic responses of mesograzers to increased abundances of opportunistic algae. Thus, further work on consumer-resource interactions will improve our understanding of the links between population- and community-level aspects of stability.

Sociodemographic and clinical characteristics of people with multiple sclerosis and neuro-myelitis optica spectrum disorder in a central northern region of Chile: A prevalence study

BackgroundThere is a scarcity of information on the prevalence of demyelinating diseases in Chile and other Latin American countries. The aim of this study was to determine the prevalence of multiple sclerosis (MS) and neuromyelitis optica spectrum disorder (NMOSD) in a region of central-northern Chile. MethodsA cross-sectional study was performed. All patients in the region with a confirmed diagnosis of MS or NMOSD under control of the program by the end of 2020 and were included in the study, totalling sixty patients with a diagnosis of MS and eight patients with NMOSD. Sociodemographic and clinical variables for these patients were recorded by the neurologists in charge of the MS programs at each public and private facility in the Coquimbo region between January and March of 2021. ResultsThe prevalence of MS was 7.18 per 100,000 inhabitants (95% CI: 5.36‒8.99) and NMOSD, 0.95 per 100,000 population (95% CI: 0.9‒1.62). Both diseases were several times more prevalent in women than in men (female/male ratio: MS, 5:1 and NMOSD, 7:1). The mean age at diagnosis was 32.2 for MS and 32.2 years for NMOSD. No relevant risk factors were identified. In terms of the type of MS, 86.6% patients had a diagnosis of relapsing-remitting MS, 6.7% had primary progressive MS, and 6.7% had secondary progressive MS. Overall, 20% of patients with MS and 12.5% with NMOSD presented score over 5 in the Expanded Disability Status Scale, and 87.5% of the NMOSD patients were receiving rituximab. ConclusionThe prevalence of demyelinating diseases in a central-northern region of Chile corresponds to the reported rates for other Latin American countries. This is an important contribution, given the scarcity of evidence on the prevalence of demyelinating diseases in Chile. These illnesses mainly affect young adult women and are a cause of disability among productive adults.

Climatic suitability and compatibility of the invasive Iris pseudacorus L. (Iridaceae) in the Southern Hemisphere: Considerations for biocontrol

Iris pseudacorus L. (Iridaceae) is an emergent macrophyte native to Europe, North Africa and western Asia. Considered invasive in wetland habitats around the world, this species is now the target of a biocontrol programme in the Southern Hemisphere. Native range surveys of the weed led to the selection of the flea beetle, Aphthona nonstriata Goeze (Coleoptera: Chrysomelidae), as a candidate biocontrol agent. An important aspect to consider in weed biocontrol is the ability of an agent to establish and thrive in the environment where it is released. Climatic incompatibility between source and intended release sites can in fact limit the success of a biocontrol programme. In the current study, the potential climatic niche of I. pseudacorus and A. nonstriata in the Southern Hemisphere was analysed. The ecological niche modelling software MaxEnt was used to map the climatic suitability of both organisms across invaded regions in South America, southern Africa and Australasia. Furthermore, occurrence records from each invaded range were used independently to model the climatic compatibility of I. pseudacorus in Europe, in order to prioritize areas of the native range to explore during future surveys for potential biocontrol agents. The models identified areas at high risk of invasion by I. pseudacorus in northern Argentina, Uruguay, southern Brazil and central Chile, as well as numerous provinces of eastern South Africa, Lesotho, southern Australia and New Zealand. Accordingly, the highest climatic suitability for A. nonstriata was predicted across the humid temperate climates of north-east Argentina, Uruguay, southern Brazil, southern South Africa, south-east Australia and New Zealand. These results can eventually be used in future release plans to prioritize areas where establishment and survival of the agent is expected to be highest. At the same time, it may be useful to search the native range of the weed for biological control agents showing high climatic adaptation towards the intended release sites of each invaded range. In this regards, our climatic compatibility models identified high-priority areas across the Mediterranean regions of Italy and southern France, as well as the temperate regions of central and western Europe. Altogether, the current study provides useful new information to tackle the invasion and advance the biocontrol programme of I. pseudacorus in the Southern Hemisphere.

Complex Rupture of the 2015 Mw 8.3 Illapel Earthquake and Prehistoric Events in the Central Chile Tsunami Gap

Abstract On 16 September 2015, the Mw 8.3 Illapel megathrust earthquake broke the subduction contact of the Nazca plate beneath the South American plate, causing unexpectedly high tsunami waves that strongly impacted the coast along the Coquimbo region in central–northern Chile. Here, we report results from a postearthquake and tsunami survey, evidencing a complex coastal geological response driven by the near coast and near trench seismic patches that ruptured during this event. Systematically, high tsunami run-ups, up to 10–11 m a.s.l., were measured on the western coast of the Punta Lengua de Vaca Peninsula in front of the near trench rupture patch, whereas tsunami run-ups up to 5–6 m were measured close to the near coast rupture patch. Detailed measurements conducted in the Coquimbo area revealed tsunami run-ups systematically higher than 6–6.5 m and up to 7.8 m. Field observations of bleached coralline algae supported by ulterior laboratory experiences were compared with geodetic measurements that evidenced complex and variable alongshore uplift-subsidence responses of the coast, suggesting a relative consistency with respect to its modern geomorphological configuration. From the analysis of pit dug in the Tongoy area, which was strongly impacted by this last tsunami, we evaluated distinctive sandy layers with benthic foraminifera tests interbedded between alluvial fine sediments, which we interpreted as paleotsunami events dated before 1108 ± 77 C.E., shortly before 1346 ± 50 C.E., and approximately 1473 ± 37 C.E. In addition to the historical massive tsunamis that occurred in 1730, 1877, and 1922 C.E. in central and northern Chile, we interpreted prehistoric tsunamis revealed here as events triggered by large megathrust earthquake ruptures, evidencing the high exposition of these coasts to near fields as well as to distant tsunamis produced along the Chilean subduction margin but also in the pan-Pacific region.

COVID lessons from the global south – Face masks invading tourist beaches and recommendations for the outdoor seasons

In response to the COVID-19 pandemic in 2020, Personal Protective Equipment (PPE) has been extensively used, and discarded PPE has been observed in many different environments, including on tourist beaches. Here we examined the distribution and densities of face masks on some of the main tourist beaches in Chile, and we monitored their daily accumulation rates on one beach in northern-central Chile. Face masks were found on beaches across the country with average densities of 0.006 ± 0.002 (mean ± se) face masks m−2, which are higher than densities reported on Peruvian beaches, but lower than those on some Kenyan beaches. Face masks were also found on more remote beaches and rocky shores in northern-central Chile. Daily accumulation rates on one tourist beach were low during austral fall/winter (0.2 face masks km−1 d−1), but were over ten times higher during austral summer (3.0 face masks km−1 d−1). These values are substantially higher than daily accumulation rates reported from urban streets, which is most likely due to the high densities of beach visitors during the summer tourist season. COVID-19 related infrastructure (signposts and PPE waste bins) was present on most beaches, but while signposts about personal protection were abundant, there were few signposts about littering, and only one of the 12 beaches sampled for COVID infrastructure had a signpost that offered recommendations about the proper disposal of used face masks. Specific waste bins for PPE waste were only available at three beaches. Based on these findings it is recommended to provide sufficient PPE-related signs and waste bins, establish general and strict waste disposal regulations, and to improve enforcement. Educational campaigns should aim at recommending proper use and disposal of face masks, litter prevention, reduction of single-use waste and enhanced pro-environmental behaviors.

Preliminary observations on terrestrial isopods (Peracarida, Isopoda) in the transitional coastal desert of Chile (24-29°S)

Abstract The terrestrial isopods of Chile make a group on which until now only a few studies have been done, most of which based mainly on species records in isolated zones. The aim of the present study was to make an attempt at characterization of the isopods present in three coastal protected areas in the Atacama Desert and northern-central Chile, and compare the results with literature records for northern and central Chile. The collected specimens belong to the genus Benthanoides (Oniscoidea, Philosciidae), probably to the species Benthanoides pauper that was originally described for central Chile. The obtained results would not agree with literature records that described the presence of two species of the genus Tylos (Oniscoidea, Tylidae) between 26-29°S, and it would be the first isopod genus recorded north of 26°S (Paposo priority site, Antofagasta Region). More systematic and ecological studies would be necessary for understanding the geographical distribution of Chilean terrestrial isopods.

Environmental Genotoxicity Assessment Using Micronucleus (and Nuclear Abnormalities) Test on Intertidal Mussel Perumytilus purpuratus: A Tool for Biomonitoring the Chilean Coast.

The release of pollutants is increasing along the coast of Chile, and the use of biomarkers in biomonitoring programs is essential to assess the early biological effects of marine contamination. The Micronucleus (MN) test was carried out using hemocytes of the mussel Perumytilus purpuratus from two sites in northern-central Chile (La Pampilla and Totoralillo). Nuclear abnormalities were assessed, and high frequencies of micronucleus (10.7-14.4‰) and other abnormalities were found (51.9-76.6‰). These values tended to be higher in La Pampilla, possibly due to the large presence of pollution sources in that site. However, considerably high values were observed in both sites. P. purpuratus is a suitable bioindicator and further monitoring along the Chilean coast using this species should be developed using the MN test and/or other biomarkers to comprehend the effects of human activities on the coastal environment of Chile.

Discrete Spawning Aggregations of the Loliginid Squid Doryteuthis gahi Reveal Life-History Interactions of a Dwarf Morphotype at the Center of Its Distribution Range

Heterogeneous environmental conditions along the Humboldt Current System (HCS) influence the life-history strategy of a variety of species in different ways. There is limited information on latitudinal traits of coastal cephalopods as part of the interacting species in pelagic and benthic environments. The present study used the loliginid squidDoryteuthis gahias a model organism to: (1) evaluate latitudinal traits on egg laying patterns, (2) characterize a particular spawning ground, (3) quantify the isotopic variation from different tissues, (4) evaluate potential trophic ontogenetic changes, (5) determinate trophic position, and (6) isotopically estimate the relative importance of putative preys in the squid’s assimilated diet. Results evidenced that egg-masses collected between 2014 and 2020 presented similar patterns along northern-central Chile (27–36°S), with females attaching small egg-capsules (10–50 mm length) through the year and over a variety of anthropogenic and natural substrates. At a small scale (Coquimbo; 29°S), early life history traits showed distinct patterns depending on SST, with warmer collection periods (∼18°C) evidencing larger capsules and smaller embryos, although small paralarvae were obtained over the 4-year sampling period. In this site, sampling of older ontogenetic stages supported the constant presence of small-sized squids (19–77 mm ML). Males had larger mean sizes compared to females and undetermined specimens, with a high proportion of mature stages. Observations in captivity were extended for up to 110 d, validating that small females (45–64 mm ML) spawn the small egg-capsules typically observed in the field. Differences in stable isotope composition between beaks and soft tissues of adult squids were lower for δ13C values (1.1 vs. 1.4‰, respectively) and higher for δ15N values (5.3 vs. 4.7‰, respectively). Isotopic composition through ontogeny found similar δ13C and δ15N values, suggesting that carbon sources (pelagic origin) and trophic position did not change significantly, with copepods, euphausiids and nereid polychaetes being the most important preys. This study unveils the permanent occurrence of a small reproductive morphotype ofD. gahiin shallow coastal habitats of northern-central Chile (i.e., center of the distribution range), providing the first insights for understanding the species’ potential adaptations to heterogeneous conditions in the HCS and the unexplored distribution gap between the two centers of abundance (Peru and the Falkland/Malvinas islands).

The rediscovery of the only introduced barnacle in Chile: Amphibalanus amphitrite (Darwin, 1854) (Crustacea: Cirripedia) in Estero Tongoy, Northern-Central Chile

The rediscovery of the only introduced barnacle in Chile: Amphibalanus amphitrite (Darwin, 1854) (Crustacea: Cirripedia) in Estero Tongoy, Northern-Central Chile

A photogrammetry-based approach for soil bulk density measurements with an emphasis on applications to cosmogenic nuclide analysis

Abstract. The quantification of soil bulk density (ρB) is a cumbersome and time-consuming task when traditional soil density sampling techniques are applied. However, it can be important for terrestrial cosmogenic nuclide (TCN) production rate scaling when deriving ages or surface process rates from buried samples, in particular when short-lived TCNs such as in situ 14C are applied. Here, we show that soil density determinations can be made using structure-from-motion multi-view stereo (SfM-MVS) photogrammetry-based volume reconstructions of sampling pits. Accuracy and precision tests as found in the literature and as conducted in this study clearly indicate that photographs taken from both a consumer-grade digital single-lens mirrorless (DSLM) and a smartphone camera are of sufficient quality to produce accurate and precise modelling results, i.e. to regularly reproduce the “true” volume and/or density by >95 %. This finding holds also if a freeware-based computing workflow is applied. The technique has been used to measure ρB along three small-scale (<1 km) N–S transects located in the semi-arid to arid Altos de Talinay, northern central Chile (∼30.5∘ S, ∼71.7∘ W), during a TCN sampling campaign. Here, long-term differences in microclimatic conditions between south-facing and north-facing slopes (SFSs and NFSs, respectively) explain a sharp contrast in vegetation cover, slope gradient and general soil condition patterns. These contrasts are also reflected by the soil density data, generally coinciding with lower densities on SFSs. The largest differences between NFSs and SFSs are evident in the lower portion of the respective slopes, close to the thalwegs. In general, field-state soil bulk densities were found to vary by about 0.6 g cm−3 over a few tens of metres along the same slope. As such, the dataset that was mainly generated to derive more accurate TCN-based process rates and ages can be used to characterise the present-day condition of soils in the study area, which in turn can give insight into the long-term soil formation and prevailing environmental conditions. This implies that the method tested in this study may also being applied in other fields of research and work, such as soil science, agriculture or the construction sector.

Knowledge status of predators of the freshwater prawn Cryphiops caementarius (Decapoda: Palaemonidae) in river systems along the North Western Andean region from Perú and Chile

Introduction: Cryphiops caementarius, is an endemic prawn from river ecosystems in Southern Perú and Northern Chile. In these watersheds, natural populations are threatened by multiple anthropic interventions such as mining activities and fishing pressure, but also, by increasing impacts of invasive exotic predators. Information related with predation on C. caementarius is scarce representing a major knowledge gap to ensure suitable management and conservation practices. Accordingly, the further deepening in relevant aspects such as the estimation of populations losses due to predators has been indicated as critical by relevant agencies as FAO. Objective: To conduct a complete registry and classification of C. caementarius predators, updating the knowledge for the Andean region. Methods: A thorough bibliographic review on existing information on C. caementarius' predators from Perú and Chile was carried out calculating percentage of occurrence, relative frequency of species, zoogeographic origin, trophic structure, phenotypic attributes, river zone that inhabits and life stage of incidence. The registry was complemented using semi-structured interviews from prawn´s fishers in central-Northern Chile. Results: C. caementarius is predated along the entire fluvial network (estuary, potamon and rhithron) by 21 species of opportunists, carnivores, omnivores and herbivores, mostly aquatic vertebrates. In turn, these belong to 15 families and six guilds of native, exotic and cosmopolitan species. Approximately 86 % predate on adult prawns, whilst, 71 % on juveniles and 24 % on larvae. More than 40 % of the predation pressure seems to be exerted by native waterfowls and 24 % by exotic fish. Conclusions: The results emphasize the relevance for conservation of native species of predators in the Andean region and the need of control measures on exotic species in a latitudinal basis. Accordingly, this review may serve as an initial decision-making tool for future conservation efforts both on prawns and native biota, but also supporting restocking actions, fisheries management plans and risk assessment for C. caementariuspopulations across the Andean region.

Small burrowing amphipods cause major damage in a large kelp.

Large herbivores such as sea urchins and fish consume a high proportion of benthic primary production and frequently control the biomass of marine macrophytes. By contrast, small mesograzers, including gastropods and peracarid crustaceans, are abundant on seaweeds but have low per capita feeding rates and their impacts on marine macrophytes are difficult to predict. To quantify how mesograzers can affect macrophytes, we examined feeding damage by the herbivorous amphipods Sunamphitoe lessoniophila and Bircenna sp., which construct burrows in the stipes of subtidal individuals of the kelp Lessonia berteroana in northern-central Chile, southeast Pacific. Infested stipes showed a characteristic sequence of progressive tissue degeneration. The composition of the amphipod assemblages inside the burrows varied between the different stages of infestation of the burrows. Aggregations of grazers within burrows and microhabitat preference of the amphipods result in localized feeding, leading to stipe breakage and loss of substantial algal biomass. The estimated loss of biomass of single stipes varied between 1 and 77%. For the local kelp population, the amphipods caused an estimated loss of biomass of 24–44%. Consequently, small herbivores can cause considerable damage to large kelp species if their feeding activity is concentrated on structurally valuable algal tissue.