Dr. Lara-Peña, Carlos

Coastal wetlands are highly threatened by human activities, leading to water quality degradation and biodiversity loss. This study assessed spatial variation in 27 water quality parameters, sediment organic matter, and macroinvertebrate assemblages across 12 sites in the estuarine Cruces River wetland (CRW Ramsar site, southern Chile) during summer 2019. Our analysis identified three areas of sampling stations in the wetland, categorized by trophic gradient and salinity: freshwater (n = 5), mixed (n = 3), and estuary (n = 4). Freshwater sites were characterized by low salinity, turbidity, and high nitrate concentrations. Estuarine sites were characterized by higher salinities and turbidity and low nitrates and total organic carbon (TOC) concentrations, and mixed sites had low salinities, high turbidities, high TOC, and low nitrates. Throughout the CRW, the richness and densities of different invertebrates were recorded. Freshwater stations had higher species richness, and estuary stations had higher abundance. Macroinvertebrates found in the lower reaches of the CRW included species characteristic of estuarine environments, whereas the upper stations were dominated by invertebrates inhabiting low-salinity environments. According to the ordination plot of distance-based redundancy analysis (dbRDA) and distance-based linear model (DistLM), our results indicate that macroinvertebrate assemblages differ significantly among areas of the CRW, primarily due to physicochemical variables (i.e., salinity, total carbon, and dissolved phosphorus). Total organic matter content in sediments was higher in freshwater sites and lower in estuarine sites. Our findings will be used to monitor the wetland and implement appropriate management measures for human activities, thereby protecting and conserving the estuarine Cruces River Ramsar wetland.

The coastal ocean off western Patagonia is one of the main coastal regions with high freshwater inputs from rivers, rain, and glaciers in the Southern Hemisphere. This study conducts an analysis of the seasonal and interannual variations in sea surface salinity and meridional geostrophic transports, specifically focusing on the Cape Horn Current, using improved satellite-derived data of sea surface salinity (SSS) and geostrophic velocities spanning an ∼11-year period (September 2011–August 2022). Our results reveal a clear salinity minimum in a coastal band between 42–54°S associated with the highest freshwater content. The average geostrophic currents are stronger south of 49°S, in line with the location of the Cape Horn Current. The average salinity minimum tends to disappear south of 54°S, with salinity values increasing slightly southward. The seasonal cycle of salinity shows the most pronounced minimum in summer (∼33.2–33.4). The greatest variability in salinity (standard deviation of salinity fields) occurs in the southern region of the Cape Horn Current. Hovmöller plots reveal two cores of minimum salinity observed in spring and summer (∼33.3–33.4). The freshwater off the Gulf of Penas contributes to the northern core. The meridional geostrophic transport differs between the northern and southern sections, with transports predominantly towards the Equator (Pole) north (south) of about 47–48°S during spring–summer. There is a marked seasonal variability in the magnitude and northern limit of the southward-flowing Cape Horn Current, being extended further north during winter and with a maximum average magnitude during summer–fall (about −2×104 m2 s−1). On the interannual scale, a major drop in surface salinity occurred off northern and central Patagonia during 2018–2019. Finally, a potential long-term freshening trend is observed in the coastal area off southern Patagonia (south of 52°S), although prolonged data records are essential to confirm this pattern.

Surface oceanic fronts are regions characterized by high biological activity. Here, Sea Surface Temperature (SST) fronts are analyzed for the period 2003–2019 using the Multi-scale Ultra-high Resolution (MUR) SST product in northern Patagonia, a coastal region with high environmental variability through river discharges and coastal upwelling events. SST gradient magnitudes were maximum off Chiloé Island in summer and fall, coherent with the highest frontal probability in the coastal oceanic area, which would correspond to the formation of a coastal upwelling front in the meridional direction. Increased gradient magnitudes in the Inner Sea of Chiloé (ISC) were found primarily in spring and summer. The frontal probability analysis revealed the highest occurrences were confined to the northern area (north of Desertores Islands) and around the southern border of Boca del Guafo. An Empirical Orthogonal Function analysis was performed to clarify the dominant modes of variability in SST gradient magnitudes. The meridional coastal fronts explained the dominant mode (78% of the variance) off Chiloé Island, which dominates in summer, whereas the SST fronts inside the ISC (second mode; 15.8%) were found to dominate in spring and early summer (October–January). Future efforts are suggested focusing on high frontal probability areas to study the vertical structure and variability of the coastal fronts in the ISC and its adjacent coastal ocean.