Letteratura scientifica selezionata sul tema "Fjords de Patagonie"

Abstract. Coccolithophores are potentially affected by ongoing ocean acidification, where rising CO2 lowers seawater pH and calcite saturation state (Ωcal). Southern Patagonian fjords and channels provide natural laboratories for studying these issues due to high variability in physical and chemical conditions. We surveyed coccolithophore assemblages in Patagonian fjords during late spring 2015 and early spring 2017. Surface Ωcal exhibited large variations driven mostly by freshwater inputs. High-Ωcal conditions (max. 3.6) occurred in the Archipelago Madre de Dios. Ωcal ranged from 2.0–2.6 in the western Strait of Magellan and 1.5–2.2 in the inner channel and was subsaturating (0.5) in Skyring Sound. Emiliania huxleyi was the only coccolithophore widely distributed in Patagonian fjords (> 96 % of total coccolithophores), only disappearing in the Skyring Sound, a semi-closed mesohaline system. Correspondence analysis associated higher E. huxleyi biomasses with lower diatom biomasses. The highest E. huxleyi abundances in Patagonia were in the lower range of those reported in Norwegian fjords. Predominant morphotypes were distinct from those previously documented in nearby oceans but similar to those of Norwegian fjords. Moderately calcified forms of E. huxleyi A morphotype were uniformly distributed throughout Patagonia fjords. The exceptional R/hyper-calcified coccoliths, associated with low Ωcal values in Chilean and Peruvian coastal upwellings, were a minor component associated with high Ωcal levels in Patagonia. Outlying mean index (OMI) niche analysis suggested that pH and Ωcal conditions explained most variation in the realized niches of E. huxleyi morphotypes. The moderately calcified A morphotype exhibited the widest niche breadth (generalist), while the R/hyper-calcified morphotype exhibited a more restricted realized niche (specialist). Nevertheless, when considering an expanded sampling domain, including nearby southeast Pacific coastal and offshore waters, even the R/hyper-calcified morphotype exhibited a higher niche breadth than other closely phylogenetically related coccolithophore species. The occurrence of E. huxleyi in naturally low pH–Ωcal environments indicates that its ecological response is plastic and capable of adaptation.

As a result of climate change, the frequency of glacial lake outburst floods (GLOF) is increasing in Chilean Patagonia. Yet, the impacts of the flood events on the physics and biology of fjords is still unknown. Current velocities, density, in-situ zooplankton samples, and volume backscatter (Sv) derived from an acoustic profiler were used to explore the response of circulation and zooplankton abundance in a Patagonian fjord to GLOF events in 2010 and 2014. Maximum Sv was found both during the GLOFs and in late winter to early spring of 2010 and the fall and summer of 2014. The increase in Sv in late winter and spring of 2010 corresponded to multiple zooplankton species found from in-situ net sampling. In addition, diel vertical migrations were found during this seasonal increase both qualitatively and in a spectral analysis. Concurrently with zooplankton increases, wind forcing produced a deepening of the pycnocline. Zooplankton abundance peaked in the fjord when the pycnocline depth deepened due to wind forcing and throughout the entire spring season, indicating that mixing conditions could favor secondary production. These results were corroborated by the 2014 data, which indicate that weather events in the region impact both fjord physics and ecology.

Abstract. The aggregation of plankton species along fjords can be linked to physical properties and processes such as stratification, turbulence and oxygen concentration. The goal of this study is to determine how water column properties and turbulent mixing affect the horizontal and vertical distributions of macrozooplankton along the only northern Patagonian fjord known to date, where hypoxic conditions occur in the water column. Acoustic Doppler current profiler moorings, scientific echo-sounder transects and in situ plankton abundance measurements were used to study macrozooplankton assemblages and migration patterns along Puyuhuapi Fjord and Jacaf Channel in Chilean Patagonia. The dissipation of turbulent kinetic energy was quantified through vertical microstructure profiles collected throughout time in areas with high macrozooplankton concentrations. The acoustic records and in situ macrozooplankton data revealed diel vertical migrations (DVM) of siphonophores, chaetognaths and euphausiids. In particular, a dense biological backscattering layer was observed along Puyuhuapi Fjord between the surface and the top of the hypoxic boundary layer (∼100 m), which limited the vertical distribution of most macrozooplankton and their DVM, generating a significant reduction of habitat. Aggregations of macrozooplankton and fishes were most abundant around a submarine sill in Jacaf Channel. In this location macrozooplankton were distributed throughout the water column (0 to ∼200 m), with no evidence of a hypoxic boundary due to the intense mixing near the sill. In particular, turbulence measurements taken near the sill indicated high dissipation rates of turbulent kinetic energy (ε∼10-5 W kg−1) and vertical diapycnal eddy diffusivity (Kρ∼10-3 m2 s−1). The elevated vertical mixing ensures that the water column is well oxygenated (3–6 mL L−1, 60 %–80 % saturation), creating a suitable environment for macrozooplankton and fish aggregations. Turbulence induced by tidal flow over the sill apparently enhances the interchange of nutrients and oxygen concentrations with the surface layer, creating a productive environment for many marine species, where the prey–predator relationship might be favored.

Abstract. The dissolved oxygen (DO) levels of coastal ocean waters have decreased over the last few decades in part because of the increase in surface and subsurface water temperature caused by climate change, the reduction in ocean ventilation, and the increase in stratification and eutrophication. In addition, biological and human activity in coastal zones, bays, and estuaries has contributed to the acceleration of current oxygen loss. The Patagonian fjord and channel system is one world region where low-DO water (LDOW, 30 %–60 % oxygen saturation) and hypoxia conditions (<30 % oxygen saturation, 2 mL L−1 or 89.2 µmol L−1) are observed. An in situ dataset of hydrographic and biogeochemical variables (1507 stations), collected from sporadic oceanographic cruises between 1970 and 2021, was used to evaluate the mechanisms involved in the presence of LDOW and hypoxic conditions in northern Patagonian fjords. Results denoted areas with LDOW and hypoxia coinciding with the accumulation of inorganic nutrients and the presence of salty and oxygen-poor Equatorial Subsurface Water mass. The role of biological activity in oxygen reduction was evident in the dominance of community respiration over gross primary production. This study elucidates the physical and biogeochemical processes contributing to hypoxia and LDOW in the northern Patagonian fjords, highlighting the significance of performing multidisciplinary research and combining observational and modeling work. This approach underscores the importance of a holistic understanding of the subject, encompassing both real-world observations and insights provided by modeling techniques.

Abstract. The increased melting and rapid retreat of marine-terminating glaciers is a key contributor to sea-level rise. In glacial fjords with shallow sills common in Patagonia, Alaska, and other systems, these bathymetric features can act as a first-order control on the dynamics. However, our understanding of how this shallow bathymetry interacts with the subglacial discharge from the glacier and impacts the fjord circulation, water properties, and rates of submarine melting is limited. To address this gap, we conduct idealized numerical simulations using a coupled plume–ocean fjord model spanning a wide range of initial ocean conditions, sill depths, and subglacial discharge. A previously documented circulation regime leads to strong mixing and vertical transport over the sill, where up to ∼ 70 % of the colder water from the upper-layer outflow is refluxed into the deeper layer, cooling the incoming warm oceanic water by as much as 1 ∘C and reducing the stratification near the glacier front. When the initial stratification is relatively strong or the subglacial discharge is relatively weak, an additional unsteady circulation regime arises where the freshwater flow can become trapped below the sill depth for weeks to months, creating an effective cooling mechanism for the deep water. We also find that submarine melting often increases when a shallow sill is added to a glacial fjord due to the reduction of stratification – which increases submarine melting – dominating over the cooling effect as the oceanic inflow is modified by the presence of the sill. These results underscore that shallow-silled fjords can have distinct dynamics that strongly modulate oceanic properties and the melting rates of marine-terminating glaciers.

Abstract de la Torriente, A., Quiñones, R. A., Miranda-Urbina, D. A., and Echevarría, F. 2010. South American sea lion and spiny dogfish predation on artisanal catches of southern hake in fjords of Chilean Patagonia. – ICES Journal of Marine Science, 67: 294–303. The South American sea lion (Otaria flavescens) is a pinniped known to interact with fisheries, potentially damaging gear and lowering catches. Predation by O. flavescens and spiny dogfish (Squalus acanthias) on artisanal southern hake (Merluccius australis) catches in fjords of Chilean Patagonia is estimated and compared. Observations were made in the Gulf of Ancud and Comau Fjord in southern Chile from October 2005 to September 2006. Losses of southern hake catches to O. flavescens predation were 1.6% of the total catch of the species, and to spiny dogfish predation were slightly higher, at 3.3%. The predation of both species on southern hake catches varied throughout the year, but was lower in summer. Both predators showed a preference for adult southern hake over juveniles. There was no significant relationship between predation on southern hake catches by the sea lion and the availability of adult and juvenile southern hake on longlines (AHCL). However, there was a significant relationship (p < 0.05) between AHCL and spiny dogfish predation. Most O. flavescens interaction events (81.4%) were during longline retrieval. Our results showed minimal interactions between O. flavescens and the artisanal southern hake fishery in the area, so with the present abundance of O. flavescens, there is no justification for reducing the sea lion population by hunting.

The spatial distribution of heavy metals content (Ba, Cd, Cu, Pb, Sr and Zn) in sediments of the Baker Fjord and surrounding channels in the central region of the Chilean fjords (47°45'S, 48°15'S) is analyzed. The aim of the study was characterized the patterns of abundance and distribution of these metals in surface sediments. The area corresponds to a poorly studied zone with low human activity. Distribution patterns would be influenced by rainfall conditions (local erosion), fluvial (continental sediments carried by rivers), glacier (glacier flour) and estuarine circulation. Cluster analysis allows differentiation among the sampled sites and group with similar characteristics. Finally, the concentrations found were contrasted with average values of metamorphic rocks and show with some certainty that the values found for calendar for this area and the greatest concentrations are the result of natural enrichment.

The Syllidae subfamilies Eusyllinae, Anoplosyllinae and Autolytinae, as well as the incertae sedis genera (Aguado et al., 2012), were studied from samples collected in shallow water from fjords and channels in Chilean Patagonia. One new species Paraehlersia kawesqar sp. nov. is described. The genus Nudisyllis Knox & Cameron, 1970 is recorded for the first time for Chile, while the species Brachysyllis infuscata (Ehlers, 1901a) and Syllides japonica Imajima, 1966 are recorded for the first time for continental Chile. Finally, Syllides articulosa Ehlers, 1897 and Epigamia sp. are also reported. The majority of the species were found inside tubes of the polychaete worm Chaetopterus cf. variopedatus (Renier, 1804) – a new habitat for syllid polychaetes. This work is an important contribution to the knowledge of syllids in Chile and to the polychaete fauna of the Patagonian region generally.

We present reconstructions of late Holocene changes in the source of organic matter and siliceous export production in the Relocanví Fjord (41°S, 72°W), Northern Chilean Patagonia, based on organic carbon content, δ13Corg, N/C ratio, diatom assemblages and biogenic silica contents from three sediment cores. The age models are based on a combination of 210Pb profiles, AMS 14C dating, and on the first occurrence of the diatom Rhizosolenia setigera f. pungens, as a stratigraphic marker in the fjords. The cores span the last 300 to 700 yr. Diatoms dominate the siliceous assemblages in the three cores (98% on average). Our results suggest that precipitation seasonality in the region of Reloncaví was high in CE 1300–1400 and CE 1700–1850, with a clear decreasing trend since CE 1850. The latter trend is in agreement with instrumental records and tree-ring reconstructions. These fluctuations seem to be associated with the Southern Annular Mode (SAM).

The kelp forests of southern Patagonia have a large diversity of habitats, with remote islands, archipelagos, peninsulas, gulfs, channels, and fjords, which are comprised of a mixture of species with temperate and sub-Antarctic distributions, creating a unique ecosystem that is among the least impacted on Earth. We investigated the distribution, diversity, and abundance of marine macroinvertebrate assemblages from the kelp forests of southern Patagonia over a large spatial scale and examined the environmental drivers contributing to the observed patterns in assemblage composition. We analyzed data from 120 quantitative underwater transects (25 x 2 m) conducted within kelp forests in the southern Patagonian fjords in the Kawésqar National Reserve (KNR), the remote Cape Horn (CH) and Diego Ramírez (DR) archipelagos of southern Chile, and the Mitre Peninsula (MP) and Isla de los Estados (IE) in the southern tip of Argentina. We observed rich assemblages of macroinvertebrates among these kelp forests, with a total of 185 unique taxa from 10 phyla and 23 classes/infraorders across the five regions. The number of taxa per transect was highest at IE, followed by MP, CH, and KNR, with the lowest number recorded at DR. The trophic structure of the macroinvertebrate assemblages was explained mostly by wave exposure (28% of the variation), followed by salinity (12%) and the KNR region (11%). KNR was most distinct from the other regions with a greater abundance of deposit feeders, likely driven by low salinity along with high turbidity and nutrients from terrigenous sources and glacial melt. Our study provides the first broad-scale description of the benthic assemblages associated with kelp forests in this vast and little-studied region and helps to establish baselines for an area that is currently lightly influenced by local anthropogenic factors and less impacted by climate change compared with other kelp forests globally.

Le Chili, deuxième pays d'élevage de saumons au monde, est celui qui utilise le plus d'antibiotiques et de pesticides, qui peuvent être nocifs pour l'environnement et l'homme. Ces composés ont tendance à être séquestrés par les particules en suspension, transportés par les courants et finalement déposés dans les sédiments, où ils sont finalement consommés par la communauté benthique. Des changements dans les communautés bactériennes, l'émergence de gènes de résistance et les impacts écologiques ont été décrits pour les antibiotiques et les pesticides, bien que la plupart se concentrent sur l'impact local de la salmoniculture. Le present travail vise à comprendre la dynamique et le devenir des antibiotiques dans le fjord de Puyuhaupi, à caractériser la partition des antibiotiques florfénicol et fluméquine par une approche expérimentale simulant les températures moyennes du fjord en hver et été. En outre, la présence des pesticides deltaméthrine et cyperméthrine dans les particules en suspension et les organismes benthiques filtrants (bivalves et éponges) dans le fjord de Puyuhuapi a été évaluée. Enfin, une expérience d’exposition des organismes vivants dans la colonne d'eau et dans les sédiments marins d'une zone sans activité aquacole (baie de Banyuls, France) a été réalisée pour évaluer si la présence d'antibiotiques et de pesticides affecte le processus de minéralisation de la matière organique, à travers des changements dans la respiration de la communauté et les composants reminéralisés. Nos résultats montrent de faibles concentrations de florfénicol (de trace à 23,1 ng L-1) et de fluméquine (niveau de trace) détectées après 180 et 360 jours (respectivement) depuis leur dernière médication à une distance comprise entre 2 et 23 km des sites d’aquaculture. Le modèle de fugacité utilisé dans notre zone d'étude, associé au modèle de décomposition, prévoit que la fluméquine peut rester dans les sédiments pendant plus de deux mois à des concentrations d'inhibition subminimales (sub-MIC). Cette situation peut favoriser la sélection bactérienne pour la résistance aux antibiotiques et, à terme, constituer un risque pour la santé humaine lié à la consommation de fruits de mer. Les valeurs des constantes de partage Kd et KOC, obtenues par des expériences en lots dans notre étude, suggèrent que la capacité d'adsorption de la fluméquine est deux fois supérieure à celle du florfénicol (Tableau 2, section 3.2), ce qui implique que la fluméquine a une plus grande tendance à être adsorbée et absorbée par les sédiments. D'un point de vue environnemental, le devenir de la fluméquine sera plus associé aux processus affectant les particules, comme leur transport et leur déposition sur le fond marin, alors que la concentration de florfénicol sera contrôlé par des processus hydrodynaques, comme la dilution et le transport par les courants. En conséquence, une fraction plus élevée de fluméquine pourrait être stockée dans les sédiments des zones côtières d'élevage de saumons. Les pesticides deltaméthrine et cyperméthrine ont été utilisés dans des bains de saumon pour contrôler les foyers d'infection de Caligus (Caligus rogercresseyi). De très faibles concentrations de deltaméthrine ont été détectées dans les particules en suspension (0,01 à 0,05 ng L-1), ce qui n'aurait aucun effet sur les organismes (NOEC, LC50 et EC50) ou au niveau écologique (NOEAEC). Cette occurrence peut traduire la remise en suspension des sédiments ou un apport externe provenant de zones adjacentes, dans lesquelles des sites d’aquaculture sont actifs. Bien que la cyperméthrine n'ait pas été utilisée dans le fjord de Puyuhuapi, de faibles concentrations ont été détectées dans les bivalves et les éponges (0,04 et 0,05 ng g-1, respectivement) avec des valeurs comparables à celles mesurées dans des saumons sauvage capturé pour la consommation humaine (0,04 ng g-1). [...]
Chile, as the second largest salmon farming country in the world, reports the highest use of antibiotics and pesticides, which can be harmful to both the environment and humans. These compounds tend to be sequestered by suspended particles, transported by currents and finally deposited in sediments, where they are later consumed by the benthic community. Changes in the bacterial community, emergence of resistance genes and impacts at the ecological level have been described for antibiotics and pesticides, although most focus on the local impact of salmon farming. This study sought to understand the dynamics and fate of antibiotics throughout the Puyuhaupi Fjord and to understand the partitioning behavior of the antibiotics florfenicol and flumequine through adsorption experiments that simulate the average temperature of the fjord. In addition, the occurrence of deltamethrin and cypermethrin in total suspended solids and filtering benthic organisms (bivalves and sponges) in the Puyuhuapi Fjord was evaluated. Finally, an experiment of respiration in the water column and marine sediments obtained in an area without aquaculture activity (Banyuls Bay, France) was developed to evaluate if the presence of antibiotics and pesticides can affect the degradation process of organic material, through changes in community respiration and remineralized components.Our results show low concentrations of florfenicol (from trace to 23.1 ng L-1) and flumequine (trace level) detected after 180 and 360 days (respectively) since their last medication at a distance between 2 and 23 km from the culture sites. The fugacity model used in our study area, together with the decay model, predicts that flumequine can remain in sediments for more than two months at sub-minimum inhibition concentrations (sub-MIC). This condition may promote bacterial selection for antibiotic resistance and eventually pose a risk to human health from the consumption of seafood products. The values of the partition constants Kd and KOC, obtained by bacth experiments, suggest that the adsorption capacity of flumequine is twice that of florfenicol (Table 2, section 3.2), implying that flumequine has a greater tendency to be adsorbed and absorbed by sediments. From an environmental point of view, our results may imply that the fate of flumequine will be related to processes affecting particles, suspension transport and seafloor deposition, whereas florfenicol concentration be controlled by hydrodynamic processes such as dilution and transport by currents. In turn, a higher fraction of flumequine may be stored in the sediments in coastal areas housing salmon farming centers.The pesticides deltamethrin and cypermethrin were incorporated through dips to control outbreaks of caligus (Caligus rogercresseyi) infection. Very low concentrations of deltamethrin were detected in total suspended solids (0.01 to 0.05 ng L-1), which value would not have an effect on organisms (NOEC, LC50 and EC50) or at the ecological level (NOEAEC), which may come from sediment resuspension or external input from adjacent areas with active salmon culture centers. Although cypermethrin was not used in Puyuhuapi Fjord, low concentrations were detected in bivalves and sponges (0.04 and 0.05 ng g-1, respectively), values comparable to wild salmon caught for human consumption (0.04 ng g-1). These results suggest an indirect exposure of the compound may be associated with external input from adjacent fjords or unreported treatments because cypermethrin can remain for more than two years in sediments with high organic material and low oxygen content. [...]
Chile, como segundo país con mayor producción en el cultivo de salmones a nivel mundial, reporta el mayor uso de antibióticos y pesticidas, lo que puede ser perjudicial tanto para el medioambiente como para el hombre. Estos compuestos tienden a ser secuestrados por las partículas suspendidas, transportados por las corrientes y, finalmente son depositadas en los sedimentos, donde eventualmente son consumidos por la comunidad bentónica. Cambios en la comunidad bacteriana, aparición de genes de resistencia e impactos a nivel ecológico han sido descritos para antibióticos y pesticidas, aunque la mayoría se enfocan en el impacto local de la actividad salmonera. Este estudio buscó entender la dinámica y el destino de los antibióticos en todo el fiordo Puyuhaupi y conocer el comportamiento particional de los antibióticos florfenicol y flumequina a través de experimentos de adsorción que simular la temperatura promedio de fiordo. Junto con esto se buscó evaluar la ocurrencia de deltametrina y cipermetrina en los sólidos totales suspendidos y los organismos bentónicos filtradores (bivalvos y esponjas) en el fiordo Puyuhuapi. Finalmente se desarrolló un experimento de respiración en columna de agua y sedimentos marinos obtenidos, una zona sin actividad acuícola (bahía Banyuls, Francia), para evaluar si la presencia de antibióticos y pesticidas pueden afectar el proceso de degradación del material orgánico, a través de cambios en respiración comunitaria y en las componentes remineralizadas.Nuestros resultados muestran bajas concentraciones florfenicol (desde traza a 23.1 ng L-1) y flumequina (nivel traza) detectados después de 180 y 360 días (respectivamente) desde su la última medicación a una distancia de entre 2 y 23 km de los centros de cultivo. El modelo de fugacidad utilizado en nuestra área de estudio, junto con el modelo de decaimiento, predicen que flumequina puede permanecer en los sedimentos más de dos meses a concentraciones de inhibición sub-Mínima (sub-MIC). Esta condición puedo promover la selección bacteriana por resistencia a los antibióticos y, eventualmente representar un riesgo para la salud humana por el consumo de productos marinos. Los valores de constantes de partición Kd y KOC, obtenidos experimentalmente en nuestro estudio, sugieren que la capacidad de adsorción de flumequina es dos veces mayor que la de florfenicol (Tabla 2, sección 3.2), lo que implica que flumequina tiene una mayor tendencia a ser adsorbido por los sedimentos. Desde el punto de vista ambiental, nuestros resultados pueden implicar que el destino de la flumequina estará más asociado a procesos como el transporte de partículas y la deposición en el fondo marino, mientras que el florfenicol debería estar másxxiiirelacionado con procesos acuáticos como la dispersión y el transporte por las corrientes, lo que sugiere que, eventualmente, una mayor fracción de flumequina puede quedar almacenada en los sedimentos en la zona con centros de cultivo de salmones.Los pesticidas deltametrina y cipermetrina se incorporaron a través de baños para controlar brotes de infección por caligus (Caligus rogercresseyi). Concentraciones muy bajas de deltametrina se detectaron en los sólidos totales suspendidos (0.01 a 0.05 ng L-1), cuyo valor no tendría un efecto sobre los organismos (NOEC, LC50 y EC50) o a nivel ecológico (NOEAEC), los que pueden provenir de la resuspensión de sedimentos o por aporte externo de áreas adyacentes con centros de cultivo activos. A pesar de no ser utilizada cipermetrina en fiordo Puyuhuapi, bajas concentraciones se detectaron en bivalvos y esponjas (0.04 y 0.05 ng g-1, respectivamente) valores comparables a salmones silvestres capturados para consumo humano (0.04 ng g-1)

Les écosystèmes marins des hautes latitudes méridionales (HLME) sont très sensibles au changement climatique, ayant un impact sur les processus physiques, chimiques et biologiques. Cependant, leur rôle important dans la modulation du climat et la circulation des masses d'eau contraste avec le nombre relativement faible d'études sur leur fonctionnement. Relativement peu d'études sur la structure de la communauté bactérioplanctonique ont été rapportées pour le sud de la Patagonie chilienne et pour l'océan Austral (SO) à grande échelle, et aucune n'a ciblé la fraction active de la communauté bactérioplanctonique. Nous avons utilisé le séquençage de l'ARNr 16S pour analyser et décrire la structure communautaire des communautés bactérioplanctoniques actives dans le sud de l'HLME. L'objectif principal de cette thèse était de caractériser la diversité et l'abondance des communautés de bactérioplancton le long de gradients environnementaux et géographiques dans le sud de HLME. Tout d'abord, nous avons cherché à savoir si les fjords voisins du sud de la Patagonie chilienne, avec un climat et une localisation similaires mais des apports d'eau douce différents, présentaient des communautés différentes. Deuxièmement, nous avons étudié les changements interannuels subis par la communauté bactérioplanctonique du fjord de Yendegaia. Troisièmement, nous avons examiné la structure spatiale à grande échelle de la communauté bactérioplanctonique le long d'un transect traversant le secteur Pacifique du SO. Nos résultats montrent que les communautés bactérioplanctoniques du pôle sud sont structurées en fonction de paramètres physiques, chimiques et biologiques caractéristiques de la zone. De plus, nous avons également démontré que les changements des paramètres environnementaux, spatiaux et temporels affectent la structure des communautés bactérioplanctoniques. Ainsi, nous soulignons l'importance des études d'écologie microbienne dans les zones sensibles au changement climatique global comme le sud de l'HLME
Southern high latitudes marine ecosystems (HLME) are highly sensitive to climate change, impacting physical, chemical, and biological processes, however, their prominent role in climate modulation and water masses circulation, contrast with the relatively low number of studies on their functioning. Relatively few studies on bacterioplankton community structure have been reported for southern Chilean Patagonia and for the Southern Ocean (SO) on a large scale, and none have targeted the active fraction of the bacterioplankton community. We used 16S rRNA sequencing to analyze and describe the community structure of the active bacterioplankton communities in southern HLME. The main objective of this thesis was to characterize de diversity and abundance of bacterioplankton communities along environmental and geographical gradients in southern HLME. First, we investigated whether nearby fjords of the southern Chilean Patagonia, with similar climate and location but different freshwater inflows, had different communities. Second, we investigated interannual changes experienced by the bacterioplankton community of the Yendegaia fjord. Third, we examined the large-scale spatial structure of the bacterioplankton community along a transect across the Pacific sector of the SO. Ours results show that southern polar bacterioplanktonic communities are structured according to physical, chemical, and biological parameters characteristic of the area. In addition, we also demonstrated that changes in environmental, spatial, and temporal parameters affect the structure of bacterioplanktonic communities. Thus, highlighting the importance of microbial ecology studies in areas sensitive to global climate change such as southern HLME

Benthic marine food webs, which recycle organic matter and sustain unique biodiversity, are an important component of estuarine Patagonian fjords. These benthic communities in the Chilean Patagonia are highly diverse as the spatial variation of its habitats and food sources. Environmental stress from glacier melt and river discharge are known drivers of benthic community dynamics; However, other pressures such as salmon farming may be strongly influencing over benthic community structure. Under the above conditions, this study focus in described the trophic structure of the subtidal benthic communities in the Puyuhuapi fjord (45°S), evaluate primary food sources that support these communities using stable isotope Bayesian analyses, and identify key benthic species based on carbon and nitrogen stable isotopes as potential tracer associated to fish farm wastes. The results showed that in the Puyuhuapi fjord different environmental and anthropogenic forces act as drivers of changes in the structure and composition of the benthic communities, such as allochthonous sources of organic matter (OM) coming mainly from glaciofluvial discharges with high contributions of terrestrial OM and salmon farming waste. Briefly, carbon and nitrogen stable isotopes analyses revealed that the highly variable isotopic niche widths respond to food supplies from marine and terrestrial OM. In addition, particulate and dissolved waste from salmon farming activities were found to modify isotopic composition ratios in many suspension feeders. Particularly, our results indicate high δ15N values in the sponge Cliona chilensis and the encrusting coral Incrustatus comauensis, which appear to be potential ecological indicators for evaluating stoichiometry imbalances and trace organic pollution sources in fjord environments.

1. Main oceanographic characteristics of Patagonian fjords The Chilean Patagonia (41°-56°S) encompasses one of the most extensive fjord regions in the world (240000 km2) with oceanographic conditions that can sustain unique ecosystems. The region is made up mainly of fjords and channels, characterized by intertangled geomorphologies where water inputs from terrestrial and marine ecosystems overlap and mix (González et al., 2013). Patagonian fjords are characterized by highly complex geomorphology and hydrographic conditions, besides strong seasonal and latitudinal patterns in precipitation, freshwater discharge, glacier coverage, and light regime (Aracena et al., 2011). These systems receive Sub-Antarctic Water (SAAW) with high loads of nitrate and phosphate from the ocean, and freshwater with high loads of silicic acid from land (Silva, 2008). The surface freshwater layer that is formed by river discharges, high precipitation and glacier melting, gradually mixes with the deeper and salty SAAW layer through estuarine circulation (Chaigneau and Pizarro, 2005; Silva et al., 2009; Schneider et al., 2014). The interplay between oceanic waters and freshwater produces a vertical and horizontal gradient in salinity, nutrients and structure of microplanktonic community, making these fjords highly heterogeneous ecosystems. In addition, this interaction allows the transport and exchange of large amounts of organic matter between terrestrial and open-ocean environments (Sievers and Silva, 2009; González et al., 2011). Patagonian fjords play an important role in biological productivity and in coastal carbon cycling (González et al., 2013; Iriarte et al., 2014). These highly productive ecosystems have a great potential in terms of transfer of food to higher trophic levels, and vertical carbon export (González et al., 2010, 2011; Montero et al., 2011, 2017a,b). Previous studies within this region have highlighted the role of light (Jacob et al., 2014), winds, low-pressure systems, and freshwater discharge in driving cycles of biological productivity and composition of the phytoplankton community at seasonal and shorter time scales (Montero et al., 2011, 2017a,b). 2. Factors that modulate primary production in Chilean Patagonia The hydrodynamic mechanism that usually controls total phytoplankton production is the alternation, in time and/or space, between the destabilization and re-stratification of the water column (Legendre and Razzoulzadegan, 1996). In fjords, fresh water inputs tends to stabilise stratification while wind stress can oppose the stabilising effects of freshwater and is likely to be an important mechanism for mixing the upper water column (Goebel et al., 2005). In general, it is accepted that the interplay between wind-forced vertical mixing, solar radiation, and nutrient availability determines the occurrence of phytoplankton blooms (Sverdrup, 1953). Iriarte and González (2008) have suggested that an improvement in the light regime towards the end of winter is the main factor triggering phytoplankton production in the southern Pacific coastal area. However, this seasonal improvement in light alone may not be enough to cause phytoplankton blooms. Montero et al. (2011) suggests that the annual solar radiation cycle interact with mesoscale patterns of wind variability to modulate primary productivity in fjords. These authors reported that the onset of the productive season in Reloncaví Fjord (41°S; 72°W) coincided with seasonal changes in the direction and intensity of meridional winds. Low-pressure synoptic (LPS) events have also been shown to be important drivers of phytoplankton productivity during winter in Puyuhuapi fjord (44°S; 72°W) (Montero et al., 2017b). In that study, the area was under low surface irradiance levels and was subjected to the passage of several LPS separated by intervals of 2 to 4 days. During these events, strong northern winds (10-20 m s-1) contributed to the mixing of the water column, resulting (subsequent to water column re- stratification) in enhanced phytoplankton productivity at very low irradiance (1-10 μE m-2 s-1) (Montero et al., 2017b). These results are novel and challenge the so far established paradigm of low levels of irradiance as a key factor limiting phytoplankton blooms in fjords ecosystems. This research has also highlighted the importance of LPS events to ecosystem productivity. During these events, periods of intensive freshwater inputs also appear to modulate pulses of primary production (including the onset of productive season) in the Puyuhuapi fjord (44°S; 72°W) (Montero et al., 2017a). Freshwater input stabilizes the water column and increase the concentration of silicic acid in the upper layers, favouring the occurrence of diatom dominated phytoplankton blooms (Montero et al., 2017a). 3. Primary production cycle in Chilean Patagonia The productivity cycle within a number of Patagonian fjords (41-51oS) has been typically described as a two-phase system consisting of a short non-productive winter phase (May to July) and a productive phase extending from late winter (August) to autumn (April) (Iriarte et al., 2007; Montero et al., 2011, 2017a). Nevertheless, more recently, the occurrence of highly productive winter blooms of phytoplankton challenges our earlier perception of winter as a low production season in these fjords (Montero et al., 2017b). The productive season has been characterized by the occurrence of diatom blooms associated with high primary production rates (1-3 g C m-2 d-1), while winter phytoplankton productivity, characterized by the dominance of small phytoplankton cells, has been reported to be a small fraction (<0.5 g C m-2 d-1) of the total annual productivity (Iriarte et al., 2007; Iriarte and González 2008; Czypionka et al. 2011; Montero et al., 2011; Paredes and Montecinos, 2011). Diatoms of the genera Pseudonitzchia, Skeletonema and Chaetoceros usually dominate the phytoplankton community during the productive season, when warmer waters have been associated with high concentrations of Pseudo-nitzschia spp., and silicate-rich waters with Skeletonema spp. and Chaetoceros spp. blooms (Montero et al., 2017a). Diatoms are known to represent a significant component of the overall phytoplankton biomass in Patagonian waters (Iriarte et al. 2001; Cassis et al., 2002; Alves- de-Souza et al., 2008; Iriarte and González, 2008). They are key species that transfer energy efficiently to higher trophic levels and also significantly contribute to the downward transfer of organic carbon (Iriarte et al., 2007; González et al., 2010; Montero et al., 2011; Iriarte et al. 2013). Low rates of primary production and low carbon sedimentation observed in the water column, mainly during winter months, suggests that most of the locally produced organic carbon is recycled within the microbial loop (Montero et al., 2011). Low temperature, and/or unfavourable light conditions, added to the dominance of small flagellates (size range: 2-20 μm) during the non-productive season, have been reported as the key factors depressing phytoplankton activity during the winter in the Patagonian fjord region (Pizarro et al., 2005; Iriarte et al., 2007; Montero et al., 2011; Montero et al., 2017a). Despite these earlier described winter characteristics, a dense bloom of the dinoflagellate Heterocapsa triquetra (32-7900 cells mL-1) was recorded during winter 2015 in the Puyuhuapi Fjord (44°S; 72°W), and was responsible for unusually high levels of winter primary production (1.6 g C m-2 d-1) (Montero et al., 2017b). More recently, we have again recorded winter blooms in the Puyuhuapi Fjord during May/July 2018 and July 2019, this time with a high abundance of diatoms such as Pseudo-nitzschia spp. and Skeletonema spp., associated with high primary production rates (2.3-2.7 g C m-2 d-1) (data unpublished). Thus, our preliminary data appear to suggest that the marked seasonal pattern of the productivity cycle in the Puyuhuapi fjord is changing, and showing every time a less predictable phytoplankton succession model. These findings introduce a novel variability for biological productivity that requires more focused research attention. 4. Bacterial community and dissolved organic matter utilization Dissolved organic matter (DOM) is an important component of the total carbon pool in aquatic ecosystem (Kirchman, 2008) and heterotrophic bacterial community is the main group within the food web involved in the degradation and mineralization of this organic material. Heterotrophic bacterial communities are able to process an important fraction of dissolved organic matter (DOM), offering a permanent and fundamental path for the transfer of matter and energy within the carbon flux (Montero et al., 2011). In the Puyuhuapi Fjord (44°S; 72°W), Reloncaví Fjord (41°S; 72°W) and in some sampling stations next to the fjord area of Southern Ice Field (49°-51°S), we have found significant correlations between primary production and bacterial secondary production rates (Daneri et al., submitted; Montero et al., 2011), reflecting a significant degree of coupling between the primary formation of organic matter and its utilization by the microbial heterotrophic community (Montero et al., 2011). Weak coupling between phytoplankton and bacterial production rates in fjord areas has been reported mainly when bacterial community uses allochthonous organic substrates as a basis for secondary production (Bukaveckas et al., 2002). DOM consists of a heterogeneous mixture of different carbon compounds that vary in chemical quality (Benner, 2002) and include both autochthonous and allochthonous sources. The majority of autochthonous DOM in aquatic ecosystem is produced by phytoplankton (primary production) (Cole et al., 1988; Bianchi, 2007; Nagata, 2008), while allochthonous organic matter is primarily derived from terrestrial vegetation and soils (Bianchi, 2007) that enters the water column mainly through river discharges. In addition of these natural sources of organic matter, coastal environments receive the supply of allochthonous organic substrates derived from anthropogenic activities. In the case of Chilean fjords, the installation of an extensive salmon farming industry in the region can be a significant source of allochthonous inorganic and organic material (Quiñones et al., 2019). While some studies have shown the potential effect of nutrient enrichment associated with salmon industry in Chilean fjords (e.g. Soto and Norambuena 2004; Iriarte et al., 2013), the effect of organic matter releasing remains a main challenge to be unravelled (Quiñones et al., 2019). Different DOM sources provides a series of ecological niches that support the growth of highly diverse bacterial communities (Buchan et al., 2014; Blanchet et al., 2016; Hoikkala et al., 2016). Bacterial community composition and bacterial production rates may vary according to the DOM source (Lucas et al., 2016). Indeed, phytoplankton blooms drive the dynamic of bacterial taxa specialized in processing efficiently photolytically produced organic matter (Buchan et al., 2014). In the case of the DOM derived from salmon farming, it has been indicated that this pool could also be an important source of organic substrates for heterotrophic bacterial community (Yoshikawa et al., 2012; Yoshikawa and Eguchi, 2013; Nimptsch et al., 2015), mainly because their high level of degradability (Nimptsch et al., 2015) and rich content in proteins (Yoshikawa et al., 2017). The responses of bacterial groups to specific DOM compounds may also vary spatially and seasonally (Bunse and Pinhassi, 2017), due to the natural variability in the composition of microbial communities associated with environmental factors (Pinhassi and Hagström, 2000). In Patagonian fjords, temperature, salinity and oxygen (Gutiérrez et al., 2018) and hydrological changes associated with meltwater discharge (Gutiérrez et al., 2015) can modify the diversity of bacterial community in the water column. In the Puyuhuapi fjord (44°S; 72°W) Gutiérrez et al. (2018), reported that the composition of the bacterial community showed a pattern of vertical zonation, where different groups Operational Taxonomic Units (OTUs) were associated to predominant water masses. Bacterial communities represented mainly by Actinomycetales, Rhodobacteraceae, Cryomorphaceae, and Flavobacteriaceae were associated with Estuarine Fresh Waters, whereas Cenarchaeaceae and Oceanospirillales were representative of Modified Sub Antarctic Waters. Salinity and dissolved oxygen concentration were the main factors that explained bacterial segregation in these contrasting water masses (Gutiérrez et al., 2018). In addition, a dramatic reduction of richness and individual abundances within Flavobacteriaceae, Rhodobacteraceae and Cenarchaeaceae families was principally associated by seasonal increase of surface water temperature (Gutiérrez et al., 2018). The composition of phytoplankton can also influence the composition of bacteria in the fjord region of Patagonia (Gutiérrez et al., 2018). Positive correlations of members of Flavobacteriaceae, Alteromonadales, and Verrucomicrobiales with diatoms in subsurface waters and of Flavobacteriales (Cryomorphaceaeand and Flavobacteriaceae), Rhodobacteraceae, and Pelagibacteraceae with dinoflagellates in surface waters suggest that phytoplankton composition could define specific niches for microorganisms in Puyuhuapi fjord waters (Gutiérrez et al., 2018). These observations support previous findings in coastal environments where certain bacterial assemblages have been associated with spring diatom blooms and others with autumn blooms dominated by dinoflagellates (El-Swais et al., 2015). Since diatoms and dinoflagellates are the major primary producers in the Puyuhuapi Fjord (Montero et al., 2017a, b), the study of specific interactions between bacteria and phytoplankton and their role in carbon fluxes certainly merits further analysis. 5. Benthic suspension feeders In aquatic ecosystems, animals that feed on suspended particles in the water are collectively known as filter feeders (Jørgensen, 1990). Benthic communities are generally dominated by suspension feeders animals (Dame et al., 2001), including those actively pumping water, passively encountering particles, or some combination of the two (Petersen, 2004; Sebens et al., 2016). Active suspension feeders produce their own internal currents and pump water through a filtering structure that separates food particles from the water (Riisgård and Larsen, 2000). Contrarily, passive suspension feeders completely rely on the current for food supply (Best, 1988). By filtering water to satisfy their nutritional demands, these animals remove vast quantities of microscopic particles such as bacteria, phytoplankton, detritus, and suspended sediments, which collectively comprise the seston (Wright et al., 1982; Langdon & Newell 1996, Kreeger & Newell 2000, Cranford et al. 2011). Bivalve molluscs such as mussels are active suspension feeders and spatially dominant in benthic communities. Filter feeding behaviour in bivalves is known to be highly responsible to fluctuations in both the abundance and composition of suspended seston (Bayne, 1998; Prins et al., 1998), mainly due they can filter large volumes of water and retain a wide size range of particles (ca. 4-35 μm diameter) (Voudanta et al., 2016). The amount of food consumed by bivalves is determined by the filtration rate and efficiency of particle retention by the gill which has evolved to act as both a water- transporting and a particle-retaining organ (Riisgård, 1988). The filtration rate of a bivalve is a parameter of great ecological importance in aquatic ecosystems, which is critical to understanding the impact of these species on particles fluxes in coastal environments. Having determined the filtration rate and knowing the concentration of suspended particles in the water, it is possible to calculate the amount of food retained by the gills and ingested by the animal, as long as no pseudofaeces are produced (Winter, 1978). Several studies have reported differences in the bivalve filtration rates depending on the composition and quality of suspended particles in the water column (Rosa et al., 2018 and references therein). In addition, seasonal variation of the available food sources has also been demonstrated as a crucial factor in selection of prey and the filtration rate of bivalves (Cranford et al., 2011; Cresson et al., 2016). Bivalves exhibit little or no movement and are dependent upon food sources available in the water column. Vertical flux of organic matter (autochthonous) mainly from phytoplankton has been considered as a main food source for bivalves (Dame, 1996; Arapov et al., 2010; Greene et al., 2011). Several studies have indicated that phytoplankton abundance can be strongly controlled by bivalve grazing in shallow areas (Cloern, 1982; Prins et al., 1998; Lonsdale et al., 2009; Lucas et al., 2016), where even this “cleaning” potential could represent a mechanism to control eutrophication in coastal areas impacted by aquaculture (Officer et al., 1982; Rice, 1999; Rice et al., 2000). Bacteria and detritus have also been described as an important contribution to the diet of bivalve populations, especially in ribbed mussels, whose morphology of gill makes these species a very effective bacterial grazer in comparison to other bivalves (Wright et al., 1982; Stuart and Klumpp, 1984; Langdon and Newell, 1990; Kreeger and Newell, 1996; Gili and Coma, 1998). Blue mussels inhabiting in close vicinity to the fish farms have been described for their capacity to use as a potential food those waste organic material from salmon cages such as uneaten food pellets and fecal particles (Reid et al., 2010; MacDonald et al., 2012; Handa et al., 2012 a, b). Several studies have indicated that bivalves grown adjacent to salmon farming areas remove the organic matter from cages, increase their growth rates (Lander et al., 2004; Peharda et al., 2007; Sarà et al., 2009) and help reduce the ecological impacts of the salmon industry in the water column (Lefebvre et al., 2000; MacDonald et al., 2012). In Chilean Patagonia fjords, salmon farming is the main aquaculture activity that takes place (Buschman et al., 2006), mainly due to favourable physical/chemical water conditions for fish (Katz, 2006). This industry releases a large quantity of organic wastes that modify the load of particulate and dissolved material in the water column (Quiñones et al., 2019), and represent a permanent source of allochthonous organic matter input to the system (Iriarte et al., 2014). These allochthonous materials together with the high amount of autochthonous organic matter produced by phytoplankton in fjords (Montero et al., 2011; Montero et al., 2017a, b) provide a heterogeneous pool of food available to benthic consumers. In this region very little is known about feeding behaviour in bivalves and what are the main components of the diet of these animals, mainly of those dominant species such as ribbed mussel Aulacomya atra present along the protected and semi-protected rocky shores in the Chilean Patagonian fjord (Försterra, 2009). Considering the importance of filter feeding bivalves to the pelagic-benthic coupling is fundamental to know if these organisms are processing both autochthonous and allochthonous organic matter. Knowing the bivalve feeding dynamic will allow a better understanding of carbon fluxes in Chilean fjords. 6. Pelagic-benthic coupling The capture and ingestion of particulate organic matter by benthic suspension feeders is one pathway through which carbon and nutrients are transferred from the water column to the benthos, resulting in their retention, utilization and cycling (Monaghan et al., 2011). Bivalves filter considerable amounts of particles. The amount of material filtered is determined by their biomass, activity and the supply of organic matter to the benthos. In Chilean Patagonian fjords, high rates of primary production (Montero et al., 2017a, b) result in the efficient export of organic carbon to sediments (González et al., 2013). In addition, particulate organic matter from terrestrial origin (Quiroga et al., 2016) together with those derived from salmon cages augments the vertical flux of particles reaching the benthos. The influence of terrestrial and aquaculture derived carbon sources on hard-bottom benthic communities from Chilean fjords has, to date, been poorly studied. Some authors have indicated that allochthonous material from terrestrial origin plays a minor role as a food for suspension feeders (Mayr et al., 2011; Zapata-Hernández et al., 2014). In contrast, autochthonous organic matter from phytoplankton production has been highlighted as one of the main food sources in benthic suspension feeders (bivalves and ascidians) from sub- Antarctic Magellan Strait (Andrade et al., 2016). From our recent studies in Patagonian fjords, we are beginning to better understand carbon fluxes in fjords environments, where bacterioplankton communities are able to process an important fraction of the organic carbon produced by phytoplankton, and classic and microbial food web are coupled playing a significant role in carbon export from surface to the benthos (Montero et al., 2011). However, little is known about the cycling of allochthonous organic matter, mainly those coming from salmon aquaculture and, what is the importance of this allocthonous material in sustaining the bacterial communities (both composition and activity) and benthic suspension feeder. This research describes the main pathways of production and utilization of autochthonous and allochthonous carbon by bacterial communities and their relative importance in sustaining benthic filter feeder bivalves.

AbstractThis chapter explores Chilean tourists’ valuation of tourism experiences in and around the Chilean village of Puyuhuapi. In 2020, local stakeholders were concerned about the impacts that salmon aquaculture infrastructure within the fjords surrounding Puyuhuapi might have on tourism. Research was undertaken to examine how prospective national tourists might perceive visible salmon aquaculture infrastructure within Puyuhuapi’s landscapes. Two hypothetical experience scenarios were designed, with short texts describing possible experiences and visual cues portraying typical destination landscapes. The scenarios were differentiated by the presence of movable floating sea cages. The scenarios were presented to potential tourists through an online survey (n = 804 responses). Results supported current nature-based tourism experience positioning, suggesting it was well received with and without the presence of salmon aquaculture infrastructure. The visible presence of the movable floating sea cages did not provoke significant differences in the valuation of the landscape for prospective tourists; nevertheless, several significant interactions occurred between tourism experience attributes and socio-demographic characteristics, including population density, level of education, and sex. Discussion focuses on defining a series of hypotheses to inform future research and the importance of expanding understanding of Chilean perspectives and imaginaries of Patagonia and its abundant natural settings and values.