Search

In order to contribute with more integrative strategies for better identify areas of high conservation priority we study the coupling of physical and biological processes that sustain a deep subpopulation of the most caught sea urchin (Loxechinus albus) worldwide and its associated epibenthic community over a bathymetric depression in southern Chile, which is surrounded by intensive anthropic activities. We used a remotely operated vehicle (ROV) to characterize the epibenthic community (organisms > 15 mm long) and substrate, up to a depth of 112 m in a submarine hole. Additionally, a combination of a towed and a moored Acoustic Doppler current Profiler (ADCP) was used to characterize current patterns. We found evidence that physical mechanisms transport and retain macro and micro material in the bottom of the hollow, and they contribute to homogenizing the habitat along the entire bathymetric gradient. These coupled processes allow i) that several species expand their bathymetric distribution range, ii) the existence of nursery areas for fishes, iii) that characteristic grazers in shallow habitats colonize greater depths, where filter feeders or DOM consumers generally represent the typical epifauna. We hypothesize that coupling of physical and biological processes on this bathymetric depression are key for bring on Loxechinus albus along the entire bathymetric gradient, who in turn is key to the community structure of the hollow. Given that this particular habitat is surrounded by intensive anthropic activities (eg. salmon aquaculture, mussel aquaculture, fishing, port) and a city, we suggest: Firstly, that monitoring should be undertaken in order to observe biodiversity changes in the bathymetric gradient, since it could be an indicator of conservation status. Secondly, that a proposal should be formulated to consider this zone as a Marine Protected Area.

The patterns of abundance, composition, biomass and vertical migration of zooplankton in short-time scales ( 10 of total dry weight (mg m −3 ) of zooplankton biomass was moderate but significant in both locations. Biomass estimated from biological samples was higher in the mixed station and determined by euphausiids. Copepods were the most abundant group in both stations. Acoustic methods were a useful technique to understand the detailed patterns of migratory strategies of zooplankton and to help estimate zooplankton biomass and abundance in the inner waters of southern Chile.

Time series of acoustic backscatter and vertical velocity profiles were obtained at three sites along a Chilean fjord with the purpose of determining dominant structures of vertical migrations of the sound scattering layer. Ancillary data obtained with stratified net samples indicated that the sound scattering layer may have been dominated by euphausiids and decapods. Therefore, distributions of acoustic backscatter anomalies and vertical velocities were attributed to vertical migrations of predominantly these organisms. Migration patterns were dominated by twilight excursions in which organisms swam toward the water surface at sunset, spent 100 m). This migration strategy can also be termed ‘semidiel migration’ as two double excursions were linked to light levels. The reasons for this twilight migration remain uncertain. But it is possible that the up and down motion around sunset was related to predation avoidance, hunger–satiation state, ontogeny, seaward transport evasion, or reaction to the environmental shock from the pycnocline, or a combination of all or some of them. In contrast, the sunrise double excursion was probably linked to feeding requirements by organisms that need to spend the day at great depth with no food available. This study demonstrated the existence of semidiel patterns throughout the fjord and through prolonged periods. In addition, identification of this pattern by acoustic backscatter was complemented by direct vertical velocity measurements. It is proposed that twilight vertical migration is a common strategy in Chilean fjords.

The prevalence of asthma and obesity is increasing worldwide, and obesity is a well-documented risk factor for asthma. The mechanisms underlying this association and parallel time trends remain largely unknown but genetic factors may be involved. Here, we report on a common ~0.45 Mb genomic inversion at 16p11.2 that can be accurately genotyped via SNP array data. We show that the inversion allele protects against the joint occurrence of asthma and obesity in five large independent studies (combined sample size of 317 cases and 543 controls drawn from a total of 5,809 samples; combined OR = 0.48, p = 5.5 × 10(-6)). Allele frequencies show remarkable worldwide population stratification, ranging from 10% in East Africa to 49% in Northern Europe, consistent with discordant and extreme genetic drifts or adaptive selections after human migration out of Africa. Inversion alleles strongly correlate with expression levels of neighboring genes, especially TUFM (p = 3.0 × 10(-40)) that encodes a mitochondrial protein regulator of energy balance and inhibitor of type 1 interferon, and other candidates for asthma (IL27) and obesity (APOB48R and SH2B1). Therefore, by affecting gene expression, the ~0.45 Mb 16p11.2 inversion provides a genetic basis for the joint susceptibility to asthma and obesity, with a population attributable risk of 39.7%. Differential mitochondrial function and basal energy balance of inversion alleles might also underlie the potential selection signature that led to their uneven distribution in world populations.

The relationships between the distribution of different zooplankton and ichthyoplankton stages and physical and chemical variables were studied using samples and data (CTD profiles, ADCP and current meter measurements, nutrients, mesozooplankton, ichthyoplankton) obtained from different strata during two 24-h cycles at two oceanographic stations in a Chilean Patagonian gulf during the CIMAR 10-Fiordos cruise (November, 2004). A station located at the Chacao Channel was dominated by tidal mixing and small increments in surface stratification during high tides, leading to decreased nutrient availability. This agreed with short periods of increased phytoplankton abundance during slack waters at the end of flood currents. Increases in larval density for all zooplankton and ichthyoplankton taxa corresponded to the flooding phases of the tidal cycle. When the larval density data were fit to a sinusoidal model, the regression coefficients were high, suggesting that tides are important features that modulate short-term variations in plankton abundance. All larvae did not vary synchronously with the tidal phase; rather, time lags were observed among species. The abundances of older individuals of the copepodite Rhincalanus nasutus and all zoea stages of the squat lobster Munida gregaria increased during night flood tides, whereas younger stages increased during daytime flood tides. At a station located at the Queullin Pass, which was dominated by vertical stratification patterns, the variations in peak larval density were better fitted to the semi-diurnal sea level fluctuations. Other evidence indicated internal tides below the pycnocline, which could promote larval transport in deeper layers. In the overall picture that emerges from this study, planktonic organisms from different habitats and phylogenetic origins seem to respond to the local tidal regimes. In some cases, this response might be beneficial, transporting these individuals inshore to areas that are rich in food during the peak biological production season.

The spatial and temporal distribution of Dinophysis spp. in a fjord in southern Chile (43°47′S–72°56′W) was studied through experiments performed in a seasonal and intratidal timescales. Seasonal variability was studied through monthly experiments performed between January 2005 and February 2006. Intratidal variability was explored through two 24-h ADCP (acoustic Doppler current profiler) current measurement experiments combined with biological sampling, in order to assess the effect of flow patterns on Dinophysis spp. distribution. We found four species of Dinophysis , which included D. acuminata and D. acuta . The former was the most abundant species in the two samplings, whereas D. acuta was only found in low concentrations near the head of fjord. The persistent saline stratification and the increased temperature during spring–summer were well associated with the increase of D. acuminata cellular concentrations inner Pitipalena Fjord. There, higher concentrations of D. acuminata were observed around the pycnocline in narrow temperature (11.19–12.52 °C) and salinity (19.75–22.59 psu) ranges. During intratidal experiments, decreases in shear instabilities in the up-fjord direction were accompanied by increases in D. acuminata concentrations (maximum 332 cells L −1 in the pycnocline). Our results suggest that the diel variability observed for D. acuminata at the Pitipalena Fjord is mainly influenced by the tidal effect and vertical density gradients (maximum 4.77 sigma-t m −1 ), which was evidenced by the vertical movement of the pycnocline (between 5 and 10 m depth) during the tidal semidiurnal cycle.

Water velocity and density profiles were obtained over a semidiurnal tidal cycle to describe the transverse variability of flow in either side of Galvarino Pass, a sill/contraction combination in a fjord-like inlet in southern Chile (44.4°S). Velocity profiles were obtained with a 614.4 kHz Acoustic Doppler Current Profiler (ADCP) during eight repetitions of a circuit that consisted of along-fjord transects along the pass and cross-fjord transects at either side of the pass. The geomorphology in Galvarino Pass represents a coastline contraction of about 90%, decreasing from 2000 m to 200 m in just 1500 m in the along-channel direction. Depth varies from 40 m on the landward side of the pass to 10 m at the shallowest portion of the sill to 80 m south of the pass. The mean flow in the northern side of the pass showed a tendency of the flow to rotate anticlockwise throughout the water column. This feature should result in a sluggish flushing of the northern side. South of the pass, mean surface outflow and mean bottom inflow (at 20 m) developed near the western side of the fjord. Within the pass, the shallowest and narrowest section represented a boundary between inflows and outflows. The strongest net inflows (∼15 cm/s) were observed in the sill region and the strongest outflows (∼10 cm/s) were seen to the south of the pass. The magnitude of the tidal flows increased inside the pass, reaching a maximum over the sill, and then decreased northward owing to conservation of mass. In the across-channel momentum balance the advective terms seemed to be greater than the rest of the terms in the northern end of the pass and over the sill. Magnitudes of the terms in the along-channel momentum balance were comparable to those in the across-channel direction, highlighting the importance of the transverse dimension under strong geometric constraints.

Measurements of velocity and density profiles were made to describe the transverse structure of the flow in Aysen Fjord, Southern Chile (45.2°S and 73.3°W). Current profiles were made with a 307.2 kHz acoustic doppler current profiler (ADCP) during 20 repetitions of a cross-fjord transect during one semidiurnal tidal cycle. The transect had a ∼320° orientation, 3 km length, and its bathymetry consisted of two channels, one on the southern side (230 m depth) and the other on the northern side (180 m depth), separated by a bank ca. 65 m depth, which was located ∼1 km from the northern coast. Density measurements to a maximum depth of 50 m were made at the extremes of each transect repetition and over the bank. Also, a total of nine CTD stations that covered the surroundings of the bank was sampled 2 days prior to the ADCP sampling. During the sampling period the mean flow showed a three layer structure that was consistent with up-fjord wind-induced exchange: a thin (