South American Continental Shelf Research Articles

Humid and cold forest connections in South America between the eastern Andes and the southern Atlantic coast during the LGM

The presence of Andean plant genera in moist forests of the Brazilian Atlantic Coast has been historically hypothesized as the result of cross-continental migrations starting at the eastern Andean flanks. Here we test hypotheses of former connections between the Atlantic and Andean forests by examining distribution patterns of selected cool and moist-adapted plant arboreal taxa present in 54 South American pollen records of the Last Glacial Maximum (LGM), ca. 19–23 cal ka, known to occur in both plant domains. Pollen taxa studied include Araucaria, Drimys, Hedyosmum, Ilex, Myrsine, Podocarpus, Symplocos, Weinmannia, Myrtaceae, Ericaceae and Arecaceae. Past connectivity patterns between these two neotropical regions as well as individual ecological niches during the LGM were explored by cluster analysis of fossil assemblages and modern plant distributions. Additionally, we examined the ecological niche of 137 plant species with shared distributions between the Andes and coastal Brazil. Our results revealed five complex connectivity patterns for South American vegetation linking Andean, Amazonian and Atlantic Forests and one disjunction distribution in southern Chile. This study also provides a better understanding of vegetation cover on the large and shallow South American continental shelf that was exposed due to a global sea level drop.

The first biological survey of the Royal Charlotte Bank (SW Atlantic) reveals a large and diverse ecosystem complex

The Southwestern Atlantic harbors unique reef environments with high proportions of endemic species. The most prominent reefs are located in the Abrolhos Bank, a 46,000 km2 extension of the South American continental shelf. However, just 100 km north of Abrolhos is the Royal Charlotte Bank (RCB), an area still poorly investigated. From a biological perspective, the only scientific information available is the historical record of lobster fisheries in the region. Hence, we performed an expedition to investigate what macrohabitats are found in the RCB and perform a preliminary biodiversity assessment. A dropcam was deployed in 67 sites and recorded images of macrohabitats and associated biodiversity. Four different macrohabitats were detected: rhodolith beds, macroalgal forests associated with rhodolith beds, calcareous sand deposits and coral reefs. The former two were the most frequent, and both rhodolith and macroalgae densities were higher on the outer shelf. A total of 83 species of fish, invertebrates and algae were identified, which comprises a comparatively high diversity for visual reef biodiversity assessments in the Southwestern Atlantic. Our findings show that the RCB is a large and diverse ecosystem complex mostly composed of rhodoliths, and also that it may be already undergoing anthropogenic impacts associated with climate change and fisheries. Therefore, further investigations are necessary to understand the extent of biodiversity and its main threats and evaluate the possible need of conservation and management measures.

Planktonic foraminifera as indicators of oceanographic complexity on the southern Caribbean Sea continental shelf

The southern Caribbean Sea over the northern South American continental shelf is oceanographically complex. It is subject to (1) widespread coastal upwelling, (2) wakes and eddies in the NW-flowing Guiana and Caribbean Currents to the lee of islands, and (3) the hypopycnal Orinoco River plume. Upwelled water is dispersed NW along high-productivity filaments. Offshore northern Trinidad, an intra-plume front separates higher-productivity Orinoco-derived water to the west from lower-productivity Amazon-derived water. This paper examines planktonic foraminiferal assemblages in surface sediment samples (a) below upwelling foci in the Gulf of Venezuela (GoV). North of Lake Maracaibo, and (b) at an upwelling focus in the North Coast Marine Area (NCMA) offshore northern Trinidad, near but west of the intra-plume front. The samples were collected for previous studies and only certain size fractions, which differed between the study areas, were available for current study.Samples from the GoV (>250 μm fraction; taken using an Alpine corer or a Petersen dredge) were assigned a priori to groups underlying upwelled and non-upwelled water. Discriminant analysis after cluster analysis confirmed these assignments. Total recovery was dominated by Neogloboquadrina dutertrei with lesser Globigerinoides ruberpink and the upwelling indicator Globigerina bulloides. All four non-upwelled samples, co-dominated by N. dutertrei and Gs. ruberpink, reflect seasonal freshwater outflow from Lake Maracaibo. Five upwelled-area samples were dominated by G. bulloides with subdominant N. dutertrei or Globigerinoides ruber Morphotype B. The remaining two upwelled samples (dominant N. dutertrei, subdominant Gs. ruber Morphotype A) apparently reflect the transition between upwelling and non-upwelling areas. The mean proportions of assemblages as Trilobatus sacculifer Morphotype A did not differ markedly between the upwelled and non-upwelled GoV clusters. This morphotype was absent from the Gulf proper but present to the north.NCMA total recovery (>150 μm fraction; samples taken using a van Veen grab) was dominated by Gs. ruber Morphotype B. Cluster analysis here indicated three clusters: Cluster 1, proximal to the intra-plume front; Cluster 2, distal to the intra-plume front; and Cluster 3, scattered throughout the NCMA. Upwelling was pervasive, canonical variate analysis (CVA) verifying that G. bulloides did not differentiate the clusters. Instead, these clusters were differentiated by Gs. ruber Morphotype B only, the proportional abundance of which was highest in Cluster I and lowest in Cluster 2. This pattern indicates that the influence of the Orinoco plume on assemblage composition is stronger than that of upwelling, Cluster 1 reflecting higher productivity near the front.

Population genetic structure of Patagonian toothfish (Dissostichus eleginoides) in the Southeast Pacific and Southwest Atlantic Ocean.

Previous studies of population genetic structure in Dissostichus eleginoides have shown that oceanographic and geographic discontinuities drive in this species population differentiation. Studies have focused on the genetics of D. eleginoides in the Southern Ocean; however, there is little knowledge of their genetic variation along the South American continental shelf. In this study, we used a panel of six microsatellites to test whether D. eleginoides shows population genetic structuring in this region. We hypothesized that this species would show zero or very limited genetic structuring due to the habitat continuity along the South American shelf from Peru in the Pacific Ocean to the Falkland Islands in the Atlantic Ocean. We used Bayesian and traditional analyses to evaluate population genetic structure, and we estimated the number of putative migrants and effective population size. Consistent with our predictions, our results showed no significant genetic structuring among populations of the South American continental shelf but supported two significant and well-defined genetic clusters of D. eleginoides between regions (South American continental shelf and South Georgia clusters). Genetic connectivity between these two clusters was 11.3% of putative migrants from the South American cluster to the South Georgia Island and 0.7% in the opposite direction. Effective population size was higher in locations from the South American continental shelf as compared with the South Georgia Island. Overall, our results support that the continuity of the deep-sea habitat along the continental shelf and the biological features of the study species are plausible drivers of intraspecific population genetic structuring across the distribution of D. eleginoides on the South American continental shelf.

Marine fishes (Elasmobranchii and Teleostei) from the Santana Archipelago, a Marine Protected Area in the southwestern Atlantic

ABSTRACTThe Santana Archipelago (22°23′S, 41°42′W) is located at the northern limit of the South Brazil Bight in Southeastern Brazil, a major topographic feature of the South American continental shelf relevant in terms of fisheries, biogeography and conservation. Herein, the first inventory of the ichthyofauna of the Santana Archipelago is presented, with information on the distribution and conservation status of 147 species of the Teleostei and Elasmobranchii. Sampling was performed during 15 field expeditions between March 2013 and November 2015. A total of 6931 specimens were collected using bottom trawl, beach seine, hand net and scuba diving. Records of 28 species were based on photographs, and five species were recorded through underwater sighting. The Elasmobranchii was represented by nine species in eight families and six orders, and the Teleostei by 138 species in 54 families and 26 orders. Previous records of fishes from the Archipelago consist of 18 species deposited in fish collections; therefore, 129 species are reported herein for the first time. Most (114, 77.5%) species have large geographic distributions (western Atlantic: 81 species, 55.1%; eastern and western Atlantic: 33 species, 22.4%), but seven recorded species (4.8%) are endemic to the Brazilian Province. At the Global (IUCN) level, 12 species (8.1%) are threatened with extinction. Thirteen (8.8%) species are also considered as threatened at the Regional (Brazilian) level. These results highlight the relevance of the Santana Archipelago in the Brazilian conservationist context. Possible threats to the ichtyofauna of the Archipelago are discussed, and effective measures of conservation are presented.

Carbonate sediment production in the equatorial continental shelf of South America: Quantifying Halimeda incrassata (Chlorophyta) contributions

The middle and outer continental shelves of eastern equatorial South America (ESA) are characterized by intense production of carbonate sediments. Qualitative analyses of sediment deposits suggest that the calcareous green alga Halimeda incrassata is among the top CaCO3 producers. Nevertheless, no study so far has quantified its real contributions. To better understand the sediment dynamic in this area, we measured biomass, growth rates and calcium carbonate production by this alga. The species exhibited high growth rates (3.38 segments.individual−1.day−1), coverage (174 individuals.m−2) and biomass (214.02 g.m−2). Substitution of segments may allow a sedimentation rate of 1.53 mm.yr−1 and a complete turnover of the population every 60.2 days. The rapid growth indicates that this alga can produce as much CaCO3 (1.19 kg CaCO3.m−2.year−1) as other tropical organisms, such as corals and rhodoliths. In a conservative estimate, 773.500 tonnes of CaCO3 are produced per year in a 5000 km2 area off the northern coast of Brazil. Sedimentation rate seems to be higher than that promoted by continental inputs in middle and outer continental shelf. On the other hand, population turnover is twice as slow as in other H. incrassata assemblages, suggesting that South American populations are sensible to physical disturbances. New studies are necessary to accurately estimate H. incrassata coverage along the Brazilian coast and to integrate data on other CaCO3 producers, such as foraminifera and coralline algae. This would allow a better understanding of the role of South American continental shelf on the global carbon budget. Furthermore, analysis on the health of these organisms is urgent, since a decline in their populations could negatively affect ecosystems functioning and services.

Sea-air carbon dioxide fluxes along 35°S in the South Atlantic Ocean

The oceans play an important role in absorbing a significant fraction of the atmospheric CO2 surplus, but there are still uncertainties concerning several open ocean regions, such as the under-sampled South Atlantic Ocean. This study assessed the net sea-air CO2 fluxes and distribution of sea-surface CO2 fugacity (fCO2sw) along the 35°S latitude in the South Atlantic, during 2011 spring and early summer periods. Underway CO2 molar fraction, temperature, salinity and dissolved oxygen measurements were taken continuously from South American to South African continental shelves. Values of both satellite and discrete in situ chlorophyll-a concentration along the ship's track were used as ancillary data. Both fCO2sw and difference in sea-air fugacity (ΔfCO2) showed high variability along the cruise track, with higher values found on the continental shelf and slope regions. All ΔfCO2 values were negative, implying that a sinking process was occurring during the cruise period, with an average net CO2 flux of −3.1±2.2mmol CO2 m−2 day−1 (using Wanninkhof, 1992). Physical variables were the main drivers of fCO2sw variability in South American continental shelf and open ocean regions, while the biological factor dominated the South African continental shelf. Algorithms for estimating fCO2 and temperature-normalized fCO2 were developed and applied separately to the three defined sub-regions: the South American shelf, the open ocean and the South African continental shelf, with the regional temperature-normalized fCO2 models showing better results.

REVISIÓN TAXONÓMICA DEL CORAL PORITES COLONENSIS (SCLERACTINIA: PORITIDAE) EN EL CARIBE COLOMBIANO

Porites colonensis is a coral from the Caribbean Sea; colonies are foliaceous, undulated, and plate-like. Polyps are dark brown or red with small bright white or green centers; pali are present in corallites and the septal plan is bisymmetrical, conformed by three fused ventral septa, a dorsal solitary septum, and two pairs of lateral septa at each side of the dorso-ventral axis. P. colonensis is similar and can be confused with the smooth varieties of Porites astreoides and Porites branneri. There are three specimens collected from Colombia and previously identified as P. colonensis: one from Golfo de Urabá (Darién ecoregion), other from Islas del Rosario (Coralline Archipelagos ecoregion), and another from an unspecified locality, in addition to one published observation from the Golfo de Urabá without collected specimens. A recent finding of other specimens in the Tayrona National Natural Park (TNNP, Tayrona ecoregion) and the absence of a rigorous taxonomic revision for all specimens collected from Colombia showed that it was necessary to review the presence and distribution of P. colonensis in the Colombian Caribbean. A taxonomic review was done for all specimens collected from Colombia and previously identified as P. colonensis. Then, the morphologic variability of specimens that were confirmed as P. colonensis was described. Only the specimens from TNNP agreed with the holotype description of P. colonensis, while others agreed with flat varieties of P. astreoides. Thus, the presence of P. colonensis is confirmed for the first time for Colombia, but its presence in other Colombian localities outside Tayrona ecoregion could not be demonstrated. This is the only confirmed record of this species for the South American continental shelf. Furthermore, the skeletal characteristics of Colombian P. colonensis corallites showed large variability, exceeding the ranges previously described for the species.

Sea surface height trend and variability at seasonal and interannual time scales in the Southeastern South American continental shelf between 27°S and 40°S

Recent improvements in satellite altimetry data correction terms are encouraging studies of the remote sensed sea level anomalies (SLA) progressively closer to the coast and over shallow continental shelves. In this paper we describe and discuss the SLA trend and variability at seasonal and interannual time scales in the southeastern South American continental shelf influenced by the Río de la Plata estuary and the Patos Lagoon fresh waters. The spatio-temporal coverage of the gridded altimetry SLA data allows identify several variability patterns and the associated physical processes. On seasonal time scales, the combination of the solar radiation and wind forcing cycles accounts for up to 98% of the variability. Seasonal variability of the wind is responsible for a difference of up to 16cm between the southern (Argentinean) Río de la Plata estuary coast and the Uruguayan and southern Brazilian coasts. On interannual time scales, positive/negative SLA anomalies are coherent with El Niño/La Niña events. Finally, a significant positive trend of up to 5mmyr−1 is found in all the study area except in the region around the Patos Lagoon (Brazil) and part of the Río de la Plata. Besides the local relevance of the results, this study indicates that satellite altimetry data are accurate enough to unveil SLA spatio-temporal patterns close to the coast and over continental shelves in the mentioned time scales.

Hydrodynamic controls on the distribution of surface sediments from the southeast South American continental shelf between 23°S and 38°S

This study aims to explore the hydrodynamic factors that influence the depositional processes on the upper continental margin of southeastern South America. Mineralogy and the activities of natural (40K) and artificial (137Cs) radionuclides from surface sediment samples were used to evaluate the provenance and oceanographic controls on depositional processes. High values of the smectite/illite (S/I) ratio indicate that the Rio de la Plata (RdlP) is a major source of terrigenous sediments to the continental shelf between 38°S and 27°S and that its importance decreases towards lower latitudes. This is also corroborated by the high radionuclide 40-K activity found in muddy sediments. The kaolinite/illite (K/I) ratio highlights the interplay between two hydrodynamic controls in the sediment distribution of the study area: (i) the Brazil Current, which supplies the shelf mostly in the northern portion of the study area with kaolinite-enriched clay minerals from tropical regions, and (ii) the Brazil Coastal Current, which transports the clay minerals, mainly illite and smectite, from the RdlP to the southern portion of the study area (up to 27°S). This is also corroborated by high 137-Cs activities. In the deeper parts (>300m) of the study area, high calcite content indicates the progressive decrease in terrigenous input towards the outer shelf and upper slope.

The effects of continental margins and water mass circulation on the distribution of dissolved aluminum and manganese in Drake Passage

A total of 232 samples were analyzed for concentrations of dissolved aluminum ([Al]) and manganese ([Mn]) in Drake Passage. Both [Al] and [Mn] were extremely low (∼0.3 and 0.1 nM, respectively) in the surface layer of the middle Drake Passage, most likely due to limited input and biological uptake/scavenging. Elevated [Al] (>14 nM) and [Mn] (>2 nM) over the South American continental shelf are related to land run‐off, whereas elevated concentrations (>1 nM and >2 nM, respectively) near the Antarctic Peninsula are most likely related to sediment re‐suspension. Re‐suspension of sedimentary particles and pore waters influences the distribution of [Al] and [Mn] over the continental slopes on both sides of Drake Passage. The influence of the continental margins and accumulated dust input potentially explains the higher [Al] observed eastward in the Atlantic section of the Southern Ocean. In the northern Drake Passage, elevated [Al] (∼0.8 nM) and [Mn] (∼0.3 nM) near the seafloor are most likely the result of bottom sediment re‐suspension by the relatively strong currents. In the deep southern Drake Passage sediment re‐suspension associated with the inflow of Weddell Sea Deep Water appears to cause elevated [Al] (>1 nM) and [Mn] (∼0.4 nM). In the deep northern Drake Passage, North Atlantic Deep Water brings in elevated [Al] and Southeast Pacific Deep Slope Water brings in the signature of Pacific hydrothermal vents. Elevated [Mn] andδ3He were correlated in this water layer and are most likely originating from the volcanically active ridges in the Pacific Ocean.

Abundance and dominance become less predictable as species richness decreases

Aim: To test the hypothesis that communities with higher diversity have more predictable properties by examining patterns of community structure along a species richness gradient. Location: Trinidad and Tobago (11°00 N, 61°00 W), on the South American continental shelf, opposite the Orinoco River delta, north-east Venezuela. Methods: We used quantile regressions to investigate how three total abundance, absolute and relative dominance measures – numerical abundance, biomass and energy use, respectively – change across a species richness gradient. We investigated which allocation rule best mimics community assembly in this species richness gradient by examining the abundance of the dominant species and comparing it with predictions of niche apportionment models. Results: All measures of total abundance increase on average across the gradient, but the upper limit remains constant. On average, absolute dominance is constant, but the distance between the upper and lower limits decreases along the gradient. Relative dominance decreases with species richness. Observed dominance patterns are best described by Tokeshi's random fraction model. Main conclusions: Our results show that both total abundance and absolute dominance become increasingly variable as biodiversity decreases. Consequently, our study suggests that ecosystem properties are less predictable when biodiversity is lower.

Are wind wave heights increasing in south-eastern south American continental shelf between 32°S and 40°S?

In this paper, a possible increase in wind wave heights in the south-eastern south American continental shelf between 32°S and 40°S is investigated. Both time series of in situ (1996–2006) and topex (1993–2001) annual mean significant wave heights gathered at the continental shelf and adjacent ocean present apparent positive trends. Even though these trends are not statistically different from zero, it must be taken into account that the available in situ and satellite data have a short span and, moreover, in situ data present several gaps. Several papers presented evidence about a possible change on the low atmospheric circulation in this region of the southern hemisphere. Consequently, a weak increase in wave height might be occurring, which would be hard to quantify due to the shortness and the insufficiency of the available observations. In order to study a possible trend in mean annual wind wave heights simulating waves nearshore (swan) model forced with ncep/ncar surface wind was implemented in a regional domain for the period 1971–2005. The annual root-mean-square heights of the simulated wave show significant trends at several locations of the inner continental shelf and the adjacent ocean. The most significant increase is observed between 1991–2000 and 1981–1990 decades. The largest difference (0.20 m, 9%) occurs around 34°S–48°W. The wave height increase is somewhat lower, 7%, in the continental shelf and in the río de la plata estuary. The annual mean energy density (spatially averaged) also presents a significant positive trend (0.036 m 2/yr) and relatively high inter-annual variability. The possible link between this inter-annual variability and el niño–southern oscillation (enso) was investigated but no apparent relationship was found. A possible increase in the annual mean energy density of waves would be able to produce changes in the littoral processes and, consequently, in the erosion of the coast.

Cryptic mitochondrial lineages in the widespread pycnogonid Colossendeis megalonyx Hoek, 1881 from Antarctic and Subantarctic waters

Colossendeis megalonyx Hoek, 1881 is a widespread and abundant pycnogonid in the Southern Ocean which has also been reported from the South Atlantic and South Pacific Oceans. Its strictly benthic lifestyle is expected to promote genetic differentiation among populations and ultimately facilitate speciation. On the other hand, the reported eurybathy and unknown larval stages of this species may allow Colossendeis megalonyx to maintain genetic continuity between isolated shallow-water habitats by active dispersal through the deep sea or by passive rafting on floating substrates. Thus, it remains unknown whether and to which extent geographically separated populations of Colossendeis megalonyx maintain gene flow in the Southern Ocean. We sampled 96 specimens of Colossendeis megalonyx from three stations in the Atlantic Sector of the Southern Ocean and one station from the South American continental shelf (Burdwood Bank). The genetic structure of nominal Colossendeis megalonyx as well as its phylogenetic position within the genus Colossendeis were assessed using a fragment of the cytochrome c oxidase subunit 1 gene. Our data strongly support that nominal Colossendeis megalonyx consists of at least five cryptic and one pseudocryptic mitochondrial lineages, four of which appear to be geographically restricted. Two lineages occurred at locations separated by more than 1,000 km in the Antarctic, thus indicating high levels of gene flow or recent colonization. No haplotype sharing across the Polar Frontal Zone was observed. Our results strongly suggest that cryptic speciation occurred within the genus Colossendeis. The wide biogeographic distribution range of Colossendeis megalonyx and perhaps that of other Antarctic pycnogonids should therefore be regarded with caution.

Distributional patterns of shallow-water polychaetes in the Magellan region: a zoogeographical and ecological synopsis

The zoogeography of polychaete annelids was described for the Magellan region. This work considered information available from 19 expeditions carried out in the last 124 years of polychaete taxonomic research around the southernmost tip of the South American continental shelf. The polychaete fauna of the Magellan region comprised a total of 431 species belonging to 108 genera and 41 families. MDS and ANOSIM analyses showed the Magellan region to be divided into two subregions, one on the Pacific side of the tip of South America and one on the Atlantic side. These subregions showed a low percentage of “endemic species” ( 70% of the species recorded for the whole Magellan region showed a wide distribution range, and there were especially high affinities with Antarctic and Subantarctic areas. We suggest that the opening of the Straits of Magellan created a new pathway for enhanced exchange of faunal elements between the Pacific and the Atlantic. Transport of larvae via easterly directed currents of the West Wind Drift plays an important role in current distribution patterns of polychaete fauna around the tip of South America.

A numerical study of the Plata River plume along the southeastern South American continental shelf

The Rio de la Plata, one of the largest rivers on Earth, discharges into the ocean waters from basin that covers a large area of South America. Its plume extends along northern Argentina, Uruguay, and southern Brazil shelves strongly influencing the ecosystems. In spite of this, little is known about the mechanisms that control it. Here we report results of simulations with POM carried out to investigate the roles of wind and river discharge in Plata plume dynamics. Different outflows were explored, including an average climatological value and magnitudes representative of La Niña and El Niño. Forcing the model with river discharge the average plume speed was directly related to the outflow intensity. The Plata northward extension varied from 850 to 1550 km and for average discharge a band of low salinity waters formed from the estuary up to 30ºN of South Brazilian Shelf. Upwelling and downwelling winds were applied after 130 days. The distribution of low salinity waters over the shelf was more sensitive to the wind direction than to the river outflow variability. Downwelling winds were very capable of advecting the low salinity signal downshelf. Upwelling winds were efficient in eroding the plume, which was basically detached from the coast by Ekman drift. Abnormal plume intrusions toward low latitudes may be a result of the original plume position coupled with events of persistent strong downwelling favorable winds.

Sea surface salinity interannual variability in the western tropical Atlantic: An ocean general circulation model study

Interannual variability of sea surface salinity in the northwest tropical Atlantic is investigated in several ocean general circulation model eddy‐permitting simulations using different air‐sea freshwater forcing. The only simulation able to reproduce some features of the observed variability from 1989 to 1993, in particular in the northwest South American region up to 20°N, east of the Lesser Antilles, is one with no relaxation to a salinity climatology. The model variability results from advection of freshwater originating from the large South American continental shelf river runoff and has a seasonal cycle associated with the displacement of the intertropical convergence zone: Anomalies develop from March to May and then propagate to a larger area within the next months with the horizontal currents (where both geostrophic and Ekman currents contribute). Later on, from July to October, the anomalies are damped through entrainment across the mixed layer base. The vertical diffusion through the mixed layer base does not weaken when anomalously fresh surface water is present (i.e., no barrier layer effect). According to the European Centre for Medium‐Range Weather Forecasts ERA15 reanalysis, air‐sea freshwater fluxes have little impact on the large (over 0.5 practical salinity scale) sea surface salinity (SSS) variability in this region. In the model, eddy variability plays little role in the interannual SSS variability, maybe because of inadequate resolution resulting in too weak and too few North Brazil Current eddies.

The diet of black-browed albatrosses at the Diego Ramirez Islands, Chile

The diet of black-browed albatrosses was studied at Gonzalo Island, Diego Ramirez, Chile, during the early chick-rearing periods of 2000, 2001, and 2002. Diet composition was determined by sampling chick-stomach contents during January and February of each year. Reconstituted meal mass was similar throughout the study, with diet being dominated by fish in all 3 years. Overall, the main items taken were the fishes Macruronus magellanicus (66–89% by mass) and Micromesistius australis (2.6–3.7% by mass), which are both fisheries-related species, and the squid Martialia hyadesi (8–20% by mass). The distribution of the prey species indicates that black-browed albatrosses obtained the bulk of their food over the South American continental shelf, but also foraged at the Antarctic Polar Front. The prevalence in the diet of fish species discarded from fishing operations, and the presence of fish hooks and fish bait species, indicate a strong association with fisheries in southern Chile.

The annual cycle of satellite derived sea surface temperature on the western South Atlantic shelf

In this article, thirteen years of weekly sea surface temperature (SST) fields derived from NOAA Advanced Very High Resolution Radiometer global area coverage infrared satellite data, from January 1982 to December 1994, are used to investigate spatial and temporal variabilities of SST seasonal cycle in the Southwest Atlantic Oceano This work addresses large scale variations over the eastem South American continental shelf and slope regions limited offshore by the 1000-m isobath, between 42° and 22°S. SST time series are fit with annual and semi-annual harmonics to describe the annual variation of sea surface temperatures. The annual harmonic explains a large proportion of the SST variability. The coefficient of determination is highest (> 90%) on the continental shelf, decreasing offshore. The estimated amplitude of the seasonal cycle ranges between 4° and 13°e throughout the study area, with minima in August­September and maxima in February-March. After the identification and removal of the dominant annual components ofSST variability, models such as the one presented here are an attractive tool to study interannual SST variability.

The annual cycle of satellite derived sea surface temperature on the western South Atlantic shelf

In this article, thirteen years of weekly sea surface temperature (SST) fields derived from NOAA Advanced Very High Resolution Radiometer global area coverage infrared satellite data, from January 1982 to December 1994, are used to investigate spatial and temporal variabilities of SST seasonal cycle in the Southwest Atlantic Oceano This work addresses large scale variations over the eastem South American continental shelf and slope regions limited offshore by the 1000-m isobath, between 42° and 22°S. SST time series are fit with annual and semi-annual harmonics to describe the annual variation of sea surface temperatures. The annual harmonic explains a large proportion of the SST variability. The coefficient of determination is highest (> 90%) on the continental shelf, decreasing offshore. The estimated amplitude of the seasonal cycle ranges between 4° and 13°e throughout the study area, with minima in AugustSeptember and maxima in February-March. After the identification and removal of the dominant annual components ofSST variability, models such as the one presented here are an attractive tool to study interannual SST variability.