Dr. León-Muñoz, Jorge

Climate-driven changes in freshwater inputs have been shown to afect the structure and function of coastal ecosystems. We evaluated changes in the infuence of river runof on coastal systems of Northwestern Patagonia (NWP) over recent decades (1993–2021) by combined analysis of long-term streamfow time series, hydrological simulation, satellite-derived and reanalysis data on sea surface conditions (temperature, turbidity, and salinity). Signifcant decreases in minimum streamfow across a zone spanning six major river basins were evident at weekly, monthly, and seasonal scales. These changes have been most pronounced in mixed-regime northern basins (e.g., Puelo River) but appear to be progressing southward to rivers characterised by a nival regime. In the adjacent two-layer inner sea, reduced freshwater input corresponds with a shallower halocline and increased surface temperatures across northern Patagonia. Our results underscore the rapidly evolving infuence of rivers on adjacent estuarine and coastal waters in NWP. We highlight the need for cross-ecosystem observation, forecasting, mitigation and adaptation strategies in a changing climate, together with corresponding adaptive basin management of systems that supply runof to the coastal marine waters.

Here, we describe an assessment of climate‐change vulnerability for the salmon farming sector in southern Chile using a model that combines semi‐quantitative measures of Exposure (risks), Sensitivity (economic and social dependence) and Adaptation Capacity (measures that prevent and mitigate impacts). The evaluation was carried out in eight pilot communes representative of salmon production (marine grow‐out). Exposure was estimated with a semi‐quantitative risk assessment tool based on oceanographic, meteorological and hydrological information, mortality‐by‐cause databases, and through extended consultation with experts and relevant stakeholders. Threats included relevant changes in water temperature and salinity, declines in dissolved oxygen, occurrence of HAB s, and diseases that could be associated with climate change. Based on our analysis of the data, we divided the farming regions into four sub‐regions with distinctive oceanographic properties and superimposed the sea surface warming trend and a spatial pattern of mortality by respective cause. Reduction of precipitation and the increase of air and sea surface temperature are the most relevant foreseen climate change drivers, especially for regions X and XI . The resulting vulnerability matrix indicated that communes with higher production concentrations were more exposed, which in some cases coincided with higher sensitivity and lower adaptation capacity. Our models of four management scenarios allowed us to explore the changes in vulnerability associated with a southward movement of salmon production towards the Magallanes region. By identifying new protocols to increase adaptation and reduce vulnerability in a spatially explicit fashion, we provide policy recommendations aimed at increasing climate change adaptation and the long‐term sustainability of the sector.

The increasing occurrence of harmful algal blooms (HABs) affecting mariculture has been related to climatic factors but also to increasing eutrophication of coastal zones, to which aquaculture may also contribute. The role of climate change on HABs may be increasingly relevant but scientific efforts to separate this from other causal factors are to date inconclusive. HABs have been a permanent threat to the aquaculture industry in southern Chile, yet government and farmers may have not paid enough attention to scientific information and advice, even when risk-based predictions and warnings have been provided. Here we describe eutrophication risk assessments for water bodies hosting salmon farms and climate change risk maps for the salmon industry in Chilean Patagonia, including the increase of HABs as a main threat. Assessments and maps were delivered in 2020 both to producers and to government. We show that such risk information and mapping could have lessened recent salmon mortality due to HABs (March-April 2021) if government and farmers had followed explicit recommendations to reduce salmon farming production in water bodies with higher risk. This measure would reduce Exposure and Sensitivity under the climate change risk framework used. We provide policy recommendations, including reviewing maximum salmon production in relevant water bodies such as fjords according to eutrophication risks, while paying attention to additional stress from climate change variability and trends.

The success of Chilean salmon farming’s early cultivation stages is largely facilitated by access to high-quality water, which is provisioned by watersheds dominated by native forests and defined by high precipitation levels. In recent decades, human activities have increasingly affected both attributes. This study analyzed the risk of climate change in 123 watersheds that supply water to land-based salmon farms in south-central Chile (36.5 43◦S). The risk was calculated based on exposure (fingerling and smolt production), sensitivity (land cover maps for three time periods), and hazard indicators (four climate change indicators). The results show a disturbing reality: under a high emissions scenario (RCP 8.5), more than 50% of the current fingerling and smolts production would be located in high or very high-risk areas. These projections are the result of both a drier and warmer climate as well as the continued processes of deforestation and fragmentation of native forests, a spatio-temporal combination which could limit the availability and quality of the water needed for optimal aquaculture production. The risk analysis suggests that landscape configuration may be a potential alternative to mitigate the consequences of climate change on Chilean salmon farming. This is particularly important in areas such as south-central Chile, where the current watershed management and/or conservation strategies do not ensure landscapes resilient to projected hydroclimatic changes.

The growth of Chilean salmon production has not been free of important sanitary and environmental shortcomings. To ensure sustainability, it is necessary to understand the environmental impacts of salmon production on the Patagonian ecosystems. Currently, there is limited regulation or monitoring of impacts in the freshwater phase compared to the marine fattening stage, and there is some evidence of local eutrophication impact and diversity changes downstream the farms. Eutrophication of Patagonian channels and fjords from marine farms has been recognized as crucial environmental risk, although most scientific evidence comes from local effects below and around farms. So far, there are no regulations based on carrying capacity estimates to limit maximum fish biomass per area or water body. There is controversy regarding the potential role of nutrients derived from farming in triggering harmful algal blooms, yet current environmental monitoring and available information does not allow establishing or rejecting a cause–effect relationship. Pesticides used to control sea lice infestation have been shown to be deleterious to some non‐target species. There is evidence that the use of high quantities of antibiotics has allowed the development of antibiotic‐resistant bacteria in sediments and there is concern that salmon aquaculture has the potential to increase the proportion of antimicrobial‐resistant bacteria to antibiotics that are used in human medicine. There is an urgent need for more comprehensive ecosystem (beyond farm) studies on the impacts of antibiotics. Escapes of salmon (exotic species) from farms are a relevant environmental risk, although the most farmed species, Salmo salar , has shown little success in establishing wild populations. The review identifies critical knowledge gaps whose fulfilment is essential to advance towards an ecosystem approach to aquaculture and to protect Patagonian ecosystems.

This study addresses the risk and vulnerability of Chilean salmon production to hazards resulting from the COVID-19 pandemic threat, including limited access to farms, limited processing capacity and reduced market demand. The role of different management approaches in reducing risk and vulnerability is also explored. Results suggest that concession areas having the largest accumulated and current biomass have the highest risk, which is also transferred to the municipal level. The scenarios modelled with better management practices that reduce diseases were able to reduce risks by 30–40%. The largest risk reduction is achieved when production biomass is divided in a more equitable manner among concession areas, suggesting the need for strategic improvements in spatial planning of the activity in the marine environment according to ecosystem carrying capacity and better practices. Improving adaptation capacity can reduce vulnerability between 20% and 30% for municipalities; for example, providing local employment can be a win-win management measure under the COVID-19 threat because it reduces movement of people and facilitates handling and responses to emergencies. A larger footprint in local economies and employment can also improve social perception and acceptance of the sector, thus contributing to improve adaptation changes and governance to face the threats. The framework used here to perform a risk and vulnerability assessment of salmon farming to the pandemic-associated threats can also be useful for other aquaculture systems elsewhere, provided that relevant information is available.

Freshwater inputs strongly influence oceanographic conditions in coastal systems of northwestern Patagonia (41–45°S). Nevertheless, the influence of freshwater on these systems has weakened in recent decades due to a marked decrease in precipitation. Here we evaluate potential influences of climate and land cover trends on the Puelo River (640 m3s–1), the main source of freshwater input of the Reloncaví Fjord (41.5°S). Water quality was analyzed along the Puelo River basin (six sampling points) and at the discharge site in the Reloncaví Fjord (1, 8, and 25 m depth), through six field campaigns carried out under contrasting streamflow scenarios. We also used several indicators of hydrological alteration, and cross-wavelet transform and coherence analyses to evaluate the association between the Puelo River streamflow and precipitation (1950–2019). Lastly, using the WEAP hydrological model, land cover maps (2001–2016) and burned area reconstructions (1985–2019), we simulated future land cover impacts (2030) on the hydrological processes of the Puelo River. Total Nitrogen and total phosphorus, dissolved carbon, and dissolved iron concentrations measured in the river were 3–15 times lower than those in the fjord. Multivariate analyses showed that streamflow drives the carbon composition in the river. High streamflow conditions contribute with humic and colored materials, while low streamflow conditions corresponded to higher arrival of protein-like materials from the basin. The Puelo River streamflow showed significant trends in magnitude (lower streamflow in summer and autumn), duration (minimum annual streamflow), timing (more floods in spring), and frequency (fewer prolonged floods). The land cover change (LCC) analysis indicated that more than 90% of the basin area maintained its land cover, and that the main changes were attributed to recent large wildfires. Considering these land cover trends, the hydrological simulations project a slight increase in the Puelo River streamflow mainly due to a decrease in evapotranspiration. According to previous simulations, these projections present a direction opposite to the trends forced by climate change. The combined effect of reduction in freshwater input to fiords and potential decline in water quality highlights the need for more robust data and robust analysis of the influence of climate and LCC on this river-fjord complex of northwestern Patagonia.

Oceanographic conditions in coastal Chilean northern Patagonia (41–46°S) are strongly influenced by freshwater inputs. Precipitation and streamflow records have shown a marked decrease in this area during the last decades. Given this hydro-climatic scenario, we evaluated the hydrological sensitivity driven by climate change in the Puelo River (average annual streamflow = 640 m3 s−1), one of the most important sources of freshwater in the fjords and inland seas of Chile’s Northern Patagonia. A lumped hydrological model was developed to evaluate the potential impacts of climate change under the Representative Concentration Pathways (RCP) 2.6, 4.5, and 8.5 scenarios in the near future (2030–2060) using the delta change method based on 25 General Circulation Models. The model was fed by local hydro-meteorological data and remote sensors, simulating well the magnitude and seasonality of Puelo River streamflow. Considering the Refined Index of Agreement (RIA), the model achieved a high performance in the calibration (RIA = 0.79) and validation stages (RIA = 0.78). Under the RCP 8.5 scenario (multi-model mean), the projections suggest that the annual input of freshwater from the Puelo River to the Reloncaví Fjord would decrease by − 10% (1.6 km3 less freshwater); these decreases would mainly take place in summer (~ − 20%) and autumn (~ − 15%). The recurrence of extreme hydroclimatic events is also projected to increase in the future, with the probability of occurrence of droughts, such as the recent 2016 event with the lowest freshwater input in the last 70 years, doubling with respect to the historical records.