The effects of two contrasting environmental conditions in nearshore waters off central Chile on the diet and morphospace of two cohorts of larval labrisomid blenny Calliclinus geniguttatus were studied using geometric morphometrics and gut content analysis. The two environmental conditions corresponded to (a) a cold period with upwelling-favourable southwesterly winds and a mixed water column of cooler water and (b) a warm period with calm winds and stratified warmer water. During the cold period, fish larvae had a more hydrodynamic head shape, longer jaws and a higher feeding incidence, suggesting a greater food supply due to upwelling events and a possible increase in encounter rates in the turbulent environment. In contrast, the larvae from the warm period had a more robust head shape with smaller jaws and a lower feeding incidence, which was related to higher water temperatures and lower wind intensities. The present study suggests that larvae have a rapid response to environmental changes on a short time scale (i.e., from weeks to months), showing a link between environmental conditions and changes in the phenotypic traits and diet of the larval stages of this cryptobenthic species.

Twelve egg capsules laid in captivity by three females of Dipturus chilensis were incubated in the laboratory. After 252 ± 9.4 days, 10 skates successfully hatched, with a mean total length, disc length, and disc width of 17.2, 7.4, and 11.4 cm, respectively. This is the first report of captive hatching of D. chilensis and its corresponding incubation period.

Larval growth, age, growth effect and instantaneous mortality were estimated in anchoveta, Engraulis ringens, collected biweekly during the austral winter of 2014 in nearshore waters off Bay of Antofagasta (23°41′W–70°30′S), northern Chile. Through measuring standard length (SL) and sagitta microstructure analysis, it was estimated that the growth rate of E. ringens larvae decreased from June (0.85 mm day−1) to August (0.50 mm day−1). However, the water temperature was homogeneous during the sampling dates (14.6, 15.2, 14.4, and 14.6°C), suggesting that the decelerating larval growth was not linked to changes in sea temperature. Additionally, larvae with slow growth have larger otoliths compared with conspecifics with fast growth (growth effect). Larval mortality rates tended to decrease until the middle of July (0.18 per day) but increased to 0.25 per day in early August, which coincided with lower food availability (i.e., chlorophyll-a, 2.7–5.6 mg m−3) and a high occurrence of smaller larvae (1.58–11.5 mm). Partial least squares analysis indicates low covariance between the biological and oceanographic variables (PLS: 11.71%), suggesting that other factors, such as parental effects, may explain the abrupt decrease in the larval growth rates.

In this work 10 years of data (1986-1996) from a fixed station located in the northern part of Valparaíso Bay (33º00’S; 71º35’W) were analysed to study the influence of coastal upwelling activity on the temporal variation of micro-phytoplankton (20-200 μm) and their relationship with oceanographic conditions. The upwelling activity at the bay was associated to semi-annual wind regime with an intensification of upwelling-favourable S-SW winds from September to March followed by a decrease and the occurrence of downwelling events from April to August. Oceanographic conditions showed the ascent of cold, nutrient-rich salty water in spring (September-November). However, during summertime under highest upwelling index, thermal stratification conditions were registered. This stratification might be associated to either the solar radiation or the presence of an upwelling shadow area in the bay. The upwelling period had the highest micro-phytoplankton abundance mainly dominated by diatoms. This period was associated with an increase in biomass and richness in the bay. Meanwhile during non-upwelling period —under homogenous conditions of temperature, salinity and nutrients— an increase in diversity (but low abundance and richness) associated to dinoflagellates and silicoflagellates was noted. Therefore, the results suggest the presence of a bi-modal regime of micro-phytoplankton in the bay in response to changes in oceanographic conditions related to local wind forcing and mixing/stratification.

Fjords are sensitive areas affected by climate change and can act as a natural laboratory to study microbial ecological processes. The Chilean Patagonian fjords (41–56°S), belonging to the Subantarctic ecosystem (46–60°S), make up one of the world’s largest fjord systems. In this region, Estuarine Water (EW) strongly influences oceanographic conditions, generating sharp gradients of oxygen, salinity and nutrients, the effects of which on the microbial community structure are poorly understood. During the spring of 2017 we studied the ecological patterns (dispersal and oceanographic factors) underlying the microbial community distribution in a linear span of 450 km along the estuarine-influenced Chilean Patagonian fjords. Our results show that widespread microbial dispersion existed along the fjords where bacterioplankton exhibited dependence on the eukaryotic phytoplankton community composition. This dependence was particularly observed under the low chlorophyll-a conditions of the Baker Channel area, in which a significant relationship was revealed between SAR11 Clade III and the eukaryotic families Pyrenomonadaceae (Cryptophyte) and Coccomyxaceae (Chlorophyta). Furthermore, dissolved oxygen and salinity were revealed as the main drivers influencing the surface marine microbial communities in these fjords. A strong salinity gradient resulted in the segregation of the Baker Channel prokaryotic communities from the rest of the Patagonian fjords. Likewise, Microbacteriaceae, Burkholderiaceae and SAR11 Clade III, commonly found in freshwater, were strongly associated with EW conditions in these fjords. The direct effect of EW on the microbial community structure and diversity of the fjords exemplifies the significance that climate change and, in particular, deglaciation have on this marine region and its productivity.

The inter-annual variability of oceanographic conditions and phytoplankton abundance and biomass was studied using 10 years (1986-1996) of in situ observations at a fixed station in Valparaíso Bay (~33ºS). The time series analysis revealed that strong S-SW winds drive a quasi-permanent upwelling activity that maintain the nutrients availability in the water column to fuel the phytoplankton in the bay. The most important changes in bio-oceanographic conditions were observed during 1987 El Niño event, which was characterized by higher temperatures but lower values for salinity, nitrate, and phosphate concentrations, together with a decrease of phytoplankton biomass compared to 1988 La Niña event when colder, saltier, and nutrient-rich upwelled water were observed. High Aconcagua River discharges were observed during the El Niño conditions (1987-1988 and 1993), which led to a decrease in surface salinity and a high abundance of dinoflagellates. Two periods with differences in bio-oceanographic conditions were observed; 1988-1992 showed lower temperatures but higher nutrients (nitrate), phytoplankton biomass and abundance of diatoms than 1993-1996 period. Throughout the study period, positive trends in upwelling activity was registered accompanied by a fall in phytoplankton biomass and dinoflagellate abundance. This paper provides new evidences concerning the influence of El Niño Southern Oscillation (ENSO) in phytoplankton and oceanographic conditions in the coastal upwelling off central Chile.

Little has been studied of the food metrics of most chondrichthyans, which provide baseline information for the assessment of fishing status to guide the development of ecosystem-based management plans. Therefore, the main goal of this study was to approach the isotopic niche of Dipturus chilensis and Callorhinchus callorynchus in Valparaíso (central Chile). The main findings showed that C. callorynchus presented a narrow ellipse (E= 0.79; RC= 4.14; θ= 1.39), meanwhile D. chilensis, presented an ellipse with greater extension (E= 0.95; RC= 8,23; θ= -0.11), therefore a wide isotopic niche.

Antarctic notothenioid fishes show wide adaptive morphological radiation, linked to habitat preferences and food composition. However, direct comparisons of phenotypic variability and feeding habits are still lacking, particularly in stages inhabiting nearshore areas. To assess these relationships, we collected juveniles and adults of the most common benthic species inhabiting shallow waters off the South Shetland Islands within a similar size range, the plunderfish Harpagifer antarcticus, the black rockcod Notothenia coriiceps, and the marbled rockcod Notothenia rossii. Individual size ranges varied from 44.0 to 98.9 mm standard length (LS) (H. antarcticus), from 95.8 to 109.3 mm LS (N. coriiceps), and from 63.0 to 113.0 mm LS (N. rossii). Notothenioid fish showed different morphospace variability, being larger for H. antarcticus than the other Notothenia species and associated with the position of the posterior end of the operculum, along with the location and relative size of the eye. The evolutionary allometry was low, but the static allometry was much higher, especially for H. antarcticus and N. rossii. The diet was mainly carnivorous, consisting of amphipods and euphausiids. Macroalgae were scarce or totally absent in the gut contents of all species. Only H. antarcticus showed an increase in the prey number and ingested prey volume with fish size. Finally, there was a significant covariation between shape changes and LS in all species (allometric effects), however, not with prey composition, probably due to the small size range or ontogenetic stage and the relative similarity (or lack of contrast) in the benthic environment that they utilized.

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.

After deposition, chondrichthyan egg capsules are frequently exposed to numerous threats that affect their survival. However, the ecological factors affecting the development and survival of embryos inside egg capsules remain unclear. The aims of this study was to quantify and describe two ecological factors that affect of the Shorttail fanskate Sympterygia brevicaudata egg capsules: predation and epibiosis. The egg capsules were collected (241) stranded from Coquimbo Bay's intertidal zone in northern Chile (29°57’S; 71°18’W and 71°19’W), and examined predation marks and epibiosis of these egg capsules at different stages of development. About 32.8% of the egg capsules presented evidence of predation marks, of which 48.1% had not yet hatched. Based on our findings, the shape and size of predation marks were different from those reported in the literature. Additionally, 78% of the egg capsules presented epibiosis, of which 21% had not yet hatched. Non-hatched egg capsules with more advanced stages of development (i.e., possessing open respiratory fissures) showed a higher probability to be predated and present epibiosis than those with earlier development (closed respiratory fissures). Ecological interactions, such as predation and the settlement of epibionts, may influence demographic aspects such as hatching success and survival rate, regulating the population sizes of S. brevicaudata during the embryonic phase.

Recent molecular evidence has called into question the identity of skates collected in the waters off the Falkland Islands previously identified as Zearaja chilensis. NADH2 sequence data indicate that these specimens are not conspecific with those currently referred to as Z. chilensis from Chile and, in fact, represent a novel cryptic species. This study aimed to investigate this hypothesis based on morphological comparisons of specimens from the coasts of both western and eastern South America. In total, 50 specimens from Chile and 41 specimens from the Falkland Islands were collected and examined; morphometric data were generated for a subset of specimens from both areas. NADH2 sequence data were generated for a total of 19 specimens from both areas, as well as specimens of Z. nasuta from New Zealand, D. pullopunctatus from South Africa, D. oxyrinchus from the Azores, Okamejei hollandi, and O. cairae from Borneo, and O. kenojei from Japan. Based on morphological and molecular analyses, Zearaja is synonymized with Dipturus and species assigned to the former genus are transferred to the latter genus. A neotype is designated for D. chilensis and this species is redescribed. Dipturus lamillai sp. nov. is described based on specimens from the Falkland Islands. Comparison of our NADH2 data with data for mitochondrial genomes generated from tissue samples taken from two specimens originally identified as Z. chilensis, indicate that, while the sample from Chile came from a specimen of D. chilensis, that from the skate steak obtained from a restaurant in Korea actually came from a specimen of D. lamillai sp. nov. This emphasizes the importance of confirming both the provenance and identity of specimens from which sequence data are generated and submitted to GenBank if misidentifications are to be avoided.

Angel sharks (Squatina spp. Duméril, 1805) are a group of coastal benthic sharks distributed worldwide, currently including threatened and understudied species. Two species are formally described along the East Pacific coast, the California angel shark S. californica Ayres, 1859 and the Chilean angel shark S. armata (Philippi, 1887). The latter species occurs in the southeastern Pacific and has historically been understudied. Additionally, the original description of S. armata lacks sufficient data to confidently identify individuals of this species compared to modern descriptions, and no type specimen is currently available to ensure specimen identification. Detailed morphological descriptions for identifying species are an essential resource for solving taxonomic issues in groups of morphologically similar species and to promote the conservation of critically endangered species. Therefore, a neotype from the type locality is here designated for S. armata, and a detailed and standardized morphological characterization based on modern taxonomic works is provided. This work contributes in improving the knowledge on the Chilean angel shark taxonomy and provides an improved frame of reference for identifying angel sharks in the East Pacific, especially in areas where species may occur in sympatry.

We describe a seiche process based on current, temperature, and sea-level data obtained from the Reloncaví fjord (41.6° S, 72.5° W) in southern Chile. We combined 4 months of acoustic Doppler current profiler (ADCP) data with sea-level, temperature, and wind time series to analyze the dynamics of low-frequency (periods > 1 day) internal oscillations in the fjord. Additionally, seasonal conductivity, temperature, and depth (CTD) data from 19 along-fjord stations were used to characterize the seasonality of the density field. The density profiles were used to estimate the internal long-wave phase speed (c) using two approximations: (1) a simple reduced gravity model (RGM) and (2) a continuously stratified model (CSM). No major seasonal changes in c were observed using either approximation (e.g., the CSM yielded 0.73 < c < 0.87 m s−1 for mode 1). The natural internal periods (TN) were estimated using Merian's formula for a simple fjord-like basin and the above phase speeds. Estimated values of TN varied between 2.9 and 3.5 days and were highly consistent with spectral peaks observed in the along-fjord currents and temperature time series. We conclude that these oscillations were forced by the wind stress, despite the moderate wind energy. Wind conditions at the end of winter gave us an excellent opportunity to explore the damping process. The observed damping time (Td) was relatively long (Td =  9.1 days).

Methane (CH4) is one of the most powerful greenhouse gases with the capacity to influence the Earth's radiative budget as well as contribute to atmospheric chemistry. Natural oceanic production makes up to ∼4% of the overall global CH4 emissions, however, there is uncertainty around the accuracy of this value due to a lack of accurate measurements. Such is the case in the Subtropical Eastern South Pacific Ocean (SESP), a region with pronounced chlorophyll-a and oxygen gradients, which in turn affect the microbial CH4 cycling. This study was conducted during spring-summer (2014–2016) in the SESP. The region (∼17°–37°S/71°–110°W) is separated into (i) eutrophic, (ii) mesotrophic, and (iii) oligotrophic areas, according to oceanographic and biogeochemical criteria. The SESP presents high CH4 zonal variability with levels ranging from 0.63 to 33.4 nmol L−1, corresponding to 29% and 1,423% saturation, respectively. High CH4 concentrations (>1,000% saturation) are observed in the narrow eutrophic area subjected to coastal upwelling. These conditions clearly differ to those observed in the extended oligotrophic subtropical gyre (∼100% saturation). Furthermore, CH4 also tends to accumulate in the mesotrophic area (with upto 1,423% saturation), where oceanographic conditions as stratification, mesoscale eddies and island mass effect could trigger the presence of a microbial biomass that may be able to induce CH4 regeneration. The CH4 efflux is estimated to be between 0.13 and 19.1 µmol m−2 d−1 (mean ± SD = 4.72 ± 4.67) and the SESP has an emission rate of ∼87.9 Gg CH4 yr−1.

Fjords play an important role in biological productivity worldwide but are vulnerable to climate/anthropogenic effects. Chilean Patagonia (41°S–55°S) is one of the largest fjord ecosystems in the world, characterized by a complex geography with highly heterogeneous hydrographic conditions and a permanent input from oceanic water mass, both of which influence the ichthyoplankton distributional patterns. In this study, we analysed the distributional patterns of ichthyoplankton and its diversity during austral spring from 1996, 2009 and 2019 in the southern Chilean fjords (47°S–54°S). The area shows important latitudinal gradients of sea surface temperature (from 15°C to 5°C), fjord-ocean variability in salinity (from 23 to 33) and water column temperature (3°C to 9°C). Spatial (but not temporal) variations in the composition and abundance of ichthyoplankton were recorded, caused mainly by differences in the abundance of larval Sprattus fuegensis, Maurolicus australis and Sebastes oculatus. Richness was higher on continental shelf and the lowest nearby fjord's head and ice fields. At the spatial scale, β-diversity showed an increased species replacement (turnover) across areas, suggesting an important role of environmental conditions (e.g., salinity and water stratification) on the larval fish structure in this region. Ordination analysis indicates that changes in salinity and temperature, caused by ice melting, is the main environmental factor influencing the abundance of larval Thysanopsetta naresi (1996), Cataetyx messieri (2009) and Bathylagichthys parini (2019). Finally, this study highlights the importance of the conservation and protection of the Chilean Patagonia and monitoring ichthyoplankton communities, which are vital biomarkers of ecosystem health.