Esse Herrera, Carlos

The intertidal invertebrate community on rocky shores in northern Chile is characterised by a high species richness resulting from the high productivity of this ecosystem. The present study aims to do the first characterisation of invertebrate communities on rocky shores in Antofagasta town and surroundings (23°S), using species co-occurrence and niche-sharing null models, analysis of similarities (ANOSIM) and nonmetric multidimensional scaling (NMDS). The null model results revealed that species associations are not structured, that the existing species do not have the same ecology, which would result in many repeated species by site, and that specificity in their ecological niches exists. The ANOSIM and NMDS revealed the absence of significant differences between sites with human intervention and without human intervention. The obtained results agree with the literature for northern and central Chilean and southern Peruvian rocky shores, and other coastal marine ecosystems with high productivity.

The Andean lakes of northern Chile and southern Bolivia are characterized by their high salinity due to arid climate and high evaporation. These lakes are poorly studied due to access difficulties. The aim of this study is to characterize two shallow saline lakes in northern Chile (Salar de Atacama, 23°S, Chile) and South Lipez of Bolivia (Khalina lake, 22.61°S) using satellite images (Landsat 8). The data involved surface temperature, chlorophyll-a concentration, and meteorological parameters (wind speed, relative humidity, atmospheric pressure). The available data revealed marked monthly variations in limnological and meteorological parameters that would be associated. The exposed antecedents revealed that the use of remote sensing techniques can be an important tool for limnological studies in zones with geographical access difficulties.

The north Patagonian lakes in their original stage were characterized by their marked oligotrophy, with high abundance of mixotrophic ciliates in lakes with native forest in their surrounding basins. Nevertheless, in the last decades, it was a replace of native forest of different kind of human activities, such as towns and agricultural zones, that generate a transition from oligotrophy to mesotrophy, being replaced the mixotrophic ciliates by different kind of phytoplankton. The aim of the present study was to propose a descriptive model using remote sensing techniques for determining the best model for predict the mixotrophic ciliates abundance in two North Patagonian Chilean lakes. In studies sites, only Caburgua lake has mixotrophic ciliates, that belong to the species Ophyridium naumanni, Stentor amethystinus and S. araucanus, whereas Villarrica lake has not mixotrophic ciliates. The multiple regression analysis revealed that for O.naumanni and S. amethystinus have significant direct associations between temperature, B01, B07 reflectances, S. araucanus abundances, and inverse associations with B02, B04 and B07, and the abundance of both species was significantly inverse. Finally, for S. araucanus was positive associations with B04 and S. amethystinus. The exposed results would be similar to the first descriptions of mixotrophic ciliates abundances for Argentinean and Chilean Patagonian lakes. On this basis, we propose the use of remote sensing techniques would be an important key tool for study the presence of these organism.

Background: Forest ecosystems provide services that are important for human use; one of the most critical ecosystem services is the provision and regulation of water. Basins with high forest improves hydrological functionality by promoting reduction in surface runoff, increase infiltration and aquifer recharge, and ensures base flow regulation amongst others. On the other hand, the conversion towards highly anthropized productive systems is usually accompanied by precarious environmental management that alters the hydrological cycle and reduction in water quality in basins. Aim: The goal of this study was to analyze land use changes and their effect on water efficiency index (WEI) in three sub-basins. Methodology: The methodology included a multi-temporal analysis of satellite images to identify land uses, also the use of SWAT (Soil and Water Assessment Tool) model for hydrological analysis in each sub-basin, information needed for calculating the WEI. Results: The results revealed the existence of no significant difference in terms of WEI between the sub-basins with predominant tree cover of native or artificial, being higher (0.89) than the WEI values reported by the sub-basin with agricultural land use (0.65). It is concluded that hydrological functions are more efficient in basins with forest cover, made up of native or exotic species, than agricultural land use with annual crop rotations. The results contribute to decision making on public policies associated to the rural productive activities. Concluded: Finally, we conclude the necessity of the promotion of forest plantation management techniques that avoid clear-cutting and multiple rotations in basin headwaters and riparian areas.

Nothofagus dombeyi plantations have silvicultural and economic potential due to their ecological plasticity, rapid growth rate, and high wood quality. However, there is little research on timber yields, their quality, and the profitability of plantations with this species subjected to different silvicultural regimes. In this study, we evaluated one plantation without and three with intermediate cuttings (pruning and thinning). Growth and yield of timber products were estimated with volume and taper functions. The physical and mechanical properties of the wood from a plantation with intermediate cuttings were determined using national and international standards. The profitability of silvicultural regimes was evaluated using the internal rate of return, the net present value, and land expectation values. In plantations with intermediate cuttings, we estimated yields of 20 m3/ha/year, and the distribution of products was 19, 27, and 54% of veneer logs, timber, and firewood, while the log yield was over 60%. In the unmanaged plantation, these proportions were 3% timber and 97% firewood. Sawn and dried wood meet the requirements associated with moisture content, dimensions, strength, performance and durability, and structural grade, aspects that are considered in different technical standards and current Chilean legal regulations. In managed plantations, the scenario of marketing dry sawn timber presents the highest profitability indicators for discount rates of 6% and 8% (NPV of 7,380 and 2,447 US$/ha). To start an industry based on wood from N. dombeyi plantations, it is necessary to invest in intermediate cuttings, as well as to promote the drying of the wood.

The Patagonian blenny (Eleginops maclovinus) is species endemic to South America with physiological characteristics that would facilitate its incorporation into Chilean aquaculture. However, there is currently no specific artificial food that can be used to raise E. maclovinus. In light of this problem, this study describes the proximal composition and fatty acid profile of the crab Hemigrapsus crenulatus, one of the main foods of E. maclovinus. The purpose of the study is to serve as basic information for the development of a specific artificial diet for juveniles of this fish species. The proximal analysis of the complete body of H. crenulatus indicates that it is mainly composed of ash (35.9%), proteins (32.2%), glucides (19.8%) and minor lipids (3.6%). The fatty acid profile is 40.7% PUFAs, 29.7% MUFAs and 29.5% SAFAs, and the most abundant acids are Eicosapentaenoic (18.8%), Oleic (6.8%) and Palmitic (16.6%), respectively. H. crenulatus has highest level of proteins, lipids and PUFAs among the species of the Brachyura infraorder.

Microplastics (MPs) have been recognized as one of the most ubiquitous environmental pollutants globally. They have been found in all ecosystems studied to date, threatening biological diversity, ecosystem functioning and human health. The present study aimed to elucidate the environmental and anthropogenic drivers of MP dynamics in the whole catchment of the Biobío river, one of the largest rivers in South America. MP concentration and characteristics were analysed in 18 sites subjected to different sources of pollution and other human-related impacts. The sampling sites were classified in relation to altitudinal zones (highland, midland and lowland) and ecosystem types (fluvial and reservoir), and different water and territorial environmental variables were further collated and considered for analysis. Seven types of microplastic polymers were identified in the samples analysed, with a catchment mean (±SE) MP concentration of 22 ± 0.4 particles m−3, and MP presence being significantly higher in lowlands (26 ± 2 particle m−3) and in reservoirs (42 ± 14 particle m−3). The most abundant type of MP was fragments (84%), with a mean concentration of 37 ± 6 particles m−3. Overall, MP concentrations were low compared to those found in other studies, with a strong influence of human population size.

Aquatic insect communities in inland waters of Chile are characterised by the presence of certain species depending on water quality, but there is little information on statistical ecology in the structure of insect communities. The aim of the present study was to apply null models to explain the structure of aquatic insects in the middle zone of the Loa River, in the Atacama Desert (Antofagasta Region, Chile; 23° S). The results of the null models of species co-occurrence showed that species associations are random, while niche sharing showed that species share ecological niches and consequently there is interspecific competition. The reported taxa are similar to communities for other North Patagonian rivers in terms of community structure. © Publisher Publishing House "Akademperiodyka" of the NAS of Ukraine, 2023.

The decapod fauna of Chile’s intertidal shores in inner seas south of 40°S has relatively low diversity because of the presence of low-salinity waters due to river inputs and glacial smelts; nevertheless it is possible that the same decapods species are found as on the northern and central Chilean coast. The aim of the present study was to determine the spatial distribution patterns of lower intertidal decapods on Pelluhuín beach, a small beach south of Puerto Montt, northern Patagonia. Data were obtained by counting individuals from random quadrants in intertidal zones; to the obtained data the variance/mean ratio was applied to determine if the specimens have a random, aggregate or uniform distribution, which are associated with Poisson, negative binomial or positive binomial distributions respectively. Among four of the species observed, a uniform distribution (positive binomial) was reported, and one had an aggregated pattern (negative binomial). The sites correspond to rocky shores in semi-urban zones, and in a protected zone. Our results on the interpretative probabilistic models of aggregated distribution patterns agree with previously reported observations of decapods on the rocky shores of Northern and Central Chile, specifically in interpretative probabilistic models. © PATRICIO DE LOS RIOS-ESCALANTE ET AL., 2024.