Mid Campanian‐Lower Maastrichtian magnetostratigraphy of the James Ross Basin,Antarctica: Chronostratigraphical implications

The James Ross Basin, in the northern Antarctic Peninsula, exposes which is probably the world thickest and most complete Late Cretaceous sedimentary succession of southern high latitudes. Despite its very good exposures and varied and abundant fossil fauna, precise chronological determination of its infill is still lacking. We report results from a magnetostratigraphic study on shelfal sedimentary rocks of the Marambio Group, southeastern James Ross Basin, Antarctica. The succession studied covers a ~1,200 m‐thick stratigraphic interval within the Hamilton Point, Sanctuary Cliffs and Karlsen Cliffs Members of the Snow Hill Island Formation, the Haslum Crag Formation, and the lower López de Bertodano Formation. The basic chronological reference framework is given by ammonite assemblages, which indicate a Late Campanian – Early Maastrichtian age for the studied units. Magnetostratigraphic samples were obtained from five partial sections located on James Ross and Snow Hill islands, the results from which agree partially with this previous biostratigraphical framework. Seven geomagnetic polarity reversals are identified in this work, allowing to identify the Chron C32/C33 boundary in Ammonite Assemblage 8‐1, confirming the Late Campanian age of the Hamilton Point Member. However, the identification of the Chron C32/C31 boundary in Ammonite Assemblage 8‐2 assigns the base of the Sanctuary Cliffs Member to the early Maastrichtian, which differs from the Late Campanian age previously assigned by ammonite biostratigraphy. This magnetostratigraphy spans ~14 Ma of sedimentary succession and together with previous partial magnetostratigraphies on Early‐Mid Campanian and Middle Maastrichtian to Danian columns permits a complete and continuous record of the Late Cretaceous distal deposits of the James Ross Basin. This provides the required chronological resolution to solve the intra‐basin and global correlation problems of the Late Cretaceous in the Southern Hemisphere in general and in the Weddellian province in particular, given by endemism and diachronic extinctions on invertebrate fossils, including ammonites. The new chronostratigraphic scheme allowed us to calculate sediment accumulation rates for almost the entire Late Cretaceous infill of the distal James Ross Basin (the Marambio Group), showing a monotonous accumulation for more than 8 Myr during the upper Campanian and a dramatic increase during the early Maastrichtian, controlled by tectonic and/or eustatic causes.     

Inter‐population differences in feeding ecology under nitrogen‐limited diets: Field growth and the role of cannibalism in limiting/improving reserve accumulation

Growth is determined by an organism's physiology, physical environment, and biological conditions, including food availability and any intra‐ and inter‐specific interactions that can affect feeding activity. To analyse how all these factors interact to produce final growth in the herbivorous/detritivorous crab Neohelice granulata, we performed field and laboratory experiments with juveniles and adults from three populations which differed genetically as well as in their physical environment and the organic matter (OM) content in the soil that serves as food. We evaluated (a) growth in the field: Juveniles of the three populations were cross‐transplanted in exclusion cages; (b) effect of the presence of adults on juvenile feeding: We measured the feeding activity of small juveniles in presence/absence of an adult male as potential predator in the field; and (c) effect of diet on cannibalism: We analysed the cannibalistic behavior of adult males from two of the populations in the laboratory after they had received protein‐rich (24%) and protein‐poor (3%) diets. In experiment (a), final size was similar for the crabs from all three origins but growth differed between sites. Experiment (b) showed that the presence of adults interfered with feeding activity at the two sites with lower weight indicators. In experiment (c), we observed that low protein diet increased the cannibalistic behavior of adult males, and this effect was more intense in crabs from the poorest food site. Our results contribute to understanding the set of factors and interactions involved in the response of individuals to the prevailing conditions in natural environments in order to maintain a growth rate, perhaps at the expense of different reserve accumulation. They also enable discussion of the limitations of approaches used in laboratory experiments.     

Population Density, Distribution and Consumption Rates of Three Corallivores at Cabo Pulmo Reef, Gulf of California, Mexico

Abstract. The influence of corallivores on coral community structure of eastern Pacific reefs has been considered less important then that of abiotic oceanographic factors. The data that support this assumption, however, are only available for Central American reefs. To assess the role of predation on hermatypic corals in a different regional reef environment, the abundance, spatial distribution and consumption rate of three corallivores: the echinoid Eucidaris thouarsii (Valenciennes), the asteroid Acanthaster planci (Linnaeus) and the teleostean fish Arothron meleagris (Bloch & Schneider), were estimated at Cabo Pulmo reef, Gulf of California, México (23°25' N, 109°25' W). Statistically, the abundances of the species did not change in any sections of the reef (mean values: E. thouarsii , 0.17 indiv. · m⁻²; A. planci , 1.9 indiv. · m⁻²; A. meleagris , 39 indiv. · ha⁻¹). The average daily individual consumption rates of coral were calculated at 1.83 g CaCO₃· m⁻² for E. thouarsii , 118.4 cm² for A. planci , and 16.38 g CaCO₃· m⁻² for A. meleagris , and were lower than those reported for Central American reefs. Considering the mean estimated carbonate production (7.9 kg CaCO₃· m⁻²· a⁻¹), corallivores eliminate less than 4% of the coral standing stock of Cabo Pulmo reef. The low corallivore population density and consumption rates, together with high local coral cover, indicate that corallivores are not key factors determining scleractinian abundance in this marginal reef.     

The influence of geological, geochemical, and biogenic habitat heterogeneity on seep biodiversity

Cold seeps are among the most heterogeneous of all continental margin habitats. Abiotic sources of heterogeneity in these systems include local variability in fluid flow, geochemistry, and substrate type, which give rise to different sets of microbial communities, microbial symbiont-bearing foundation species, and associated heterotrophic species. Biogenic habitats created by microbial mats and the symbiotic species including vesicomyid clams, bathymodiolin mussels, and siboglinid tubeworms add an additional layer of complexity to seep habitats. These forms of habitat heterogeneity result in a variety of macrofaunal and meiofaunal communities that respond to changes in structural complexity, habitat geochemistry, nutrient sources, and interspecific interactions in different ways and at different scales. These responses are predicted by a set of theoretical metacommunity models, the most appropriate of which for seep systems appears to be the 'species sorting' concept, an extension of niche theory. This concept is demonstrated through predictable patterns of community assembly, succession, and beta-level diversity. These processes are described using a newly developed analytical technique examining the change in the slope of the species accumulation curve with the number of habitats examined. The diversity response to heterogeneity has a consistent form, but quantitatively changes at different seep sites around the world as the types of habitats present and the size-classes of fauna analyzed change. The increase in beta diversity across seep habitat types demonstrates that cold seeps and associated biogenic habitats are significant sources of heterogeneity on continental margins globally.     

Predicting forest fire in the Brazilian Amazon using MODIS imagery and artificial neural networks

The presented work describes a methodology that employs artificial neural networks (ANN) and multi-temporal imagery from the MODIS/Terra-Aqua sensors to detect areas of high risk of forest fire in the Brazilian Amazon. The hypothesis of this work is that due to characteristic land use and land cover change dynamics in the Amazon forest, forest areas likely to be burned can be separated from other land targets. A study case was carried out in three municipalities located in northern Mato Grosso State, Brazilian Amazon. Feedforward ANNs, with different architectures, were trained with a backpropagation algorithm, taking as inputs the NDVI values calculated from MODIS imagery acquired during five different periods preceding the 2005 fire season. Selected samples were extracted from areas where forest fires were detected in 2005 and from other non-burned forest and agricultural areas. These samples were used to train, validate and test the ANN. The results achieved a mean squared error of 0.07. In addition, the model was simulated for an entire municipality and its results were compared with hotspots detected by the MODIS sensor during the year. A histogram analysis showed that the spatial distribution of the areas with fire risk were consistent with the fire events observed from June to December 2005. The ANN model allowed a fast and relatively precise method to predict forest fire events in the studied area. Hence, it offers an excellent alternative for supporting forest fire prevention policies, and in assisting the assessment of burned areas, reducing the uncertainty involved in currently used methods.     

Landslide inventory using image fusion techniques in Brazil

The present work aims to assess the accuracy of six fusion techniques (Brovey, IHS, HSV, PCA, WTYO and WTVE) in order to compile landslide inventories using orbital images (ETM+ and PAN HRV). The study area is characterized by steep terrain and dense forest in Caraguatatuba, São Paulo State, Brazil. In terms of spatial quality, the Wavelet Transform technique provided the best results, presenting correlations above 90%. As for spectral quality, the best results were obtained with the IHS fusion. Based on the results, it may be concluded that the IHS is the best technique for preserving spatial and spectral information from the original images, so as to more clearly identify landslide scars. However, it was still not possible to typify the landslides from remote sensing data. Nonetheless, it is believed that image fusion techniques adequately met expectations in terms of their capacity to identify landslide for the creation of an inventory for the studied area.     

The barnacle Balanus amphitrite as a biomonitor for Cd: Radiolabelled experiments

Radiolabelled experiments were carried out to measure necessary parameters in the development of a biodynamic ecotoxicological simulation model of Cd accumulation in the barnacle biomonitor Balanus amphitrite. The Cd uptake rate constant from the dissolved phase, the Cd assimilation efficiency (AE) from suspended particulate matter (SPM) and the efflux rate constant were obtained using ¹⁰⁹Cd. A Cd uptake rate constant from the dissolved phase (k_u) of 0.0072 L g⁻¹ h⁻¹ was determined for the barnacle under environmentally realistic dissolved Cd concentrations (maximum of 400 ng L⁻¹). Cd AE from SPM was determined from the barnacle feeding on SPM with low and high chl a concentrations, resulting in AEs of 39.0% and 48.7%, respectively, and an efflux rate of 0.0072 d⁻¹. The difference between the AEs resulted from differences in chl a:SPM ratios suggesting a general tendency of higher AE when SPM is enriched with chl a. These results reinforce that the accuracy of ecotoxicological models for metal accumulation in organisms depends on how representative the selected food items are of the organism’s natural diet.     

A snapshot of suspended sediment and fluid mud occurrence in a mixed-energy embayment, Tijucas Bay, Brazil

Along the southern Brazilian coast, Tijucas Bay is known for its unique muddy tidal flats associated with chenier plains. Previous field observations pointed to very high suspended sediment concentrations (SSCs) in the inner parts of the bay, and in the estuary of the Tijucas River, suggesting the presence of fluid mud. In this study, the occurrences of suspended sediments and fluid mud were examined during a larger-scale, high-resolution 2-day field campaign on 1–2 May 2007, encompassing survey lines spanning nearly 80 km, 75 water sampling stations for near-bottom density estimates, and ten sediment sampling stations. Wave refraction modeling provided qualitative wave energy estimates as a function of different incidence directions. The results show that SSC increases toward the inner bay near the water surface, but seaward near the bottom. This suggests that suspended sediment is supplied by the local rivers, in particular the Tijucas. Near-surface SSCs were of the order of 50 mg l⁻¹ close to the shore, but exceeded 100 mg l⁻¹ near the bottom in the deeper parts of the bay. Fluid mud thickness and location given by densimetry and echo-sounding agreed in some places, although being mostly discordant. The best agreement was observed where wave energy was high during the campaign. The discrepancy between the two methods may be an indication for the existence of fluid mud, which is recorded by one method but not the other. Agreement is considered to be an indication of fluidization, whereas disagreement indicates more consolidation. Wave modeling suggests that waves from the ENE and SE are the most effective in supplying energy to the inner bay, which may induce the liquefaction of mud deposits to form fluid mud. Nearshore mud resuspension and weak horizontal currents result in sediment-laden offshore flow, which explains the higher SSCs measured in the deeper parts of the bay, besides providing a mechanism for fine-sediment export to the inner shelf.     

Relationships between bioturbation by Tylos spinulosus (Crustacea, Isopoda) and its distribution on sandy beaches of north-central Chile

The semi-terrestrial isopod, Tylos spinulosus Dana, is a common inhabitant of the upper shore levels of sandy beaches of north-central Chile (ca. 26–30°S). During daylight hours, this isopod remains buried in the sand, while during the night emerges for feeding on stranded organic detritus, leaving exit holes on the beach surface. After feeding, isopods return to dig in their burrowing zones leaving surface irregularities such as cone-shaped mounds of sand. The burrowing preference of T. spinulosus was studied in the field, by: (i) releasing 30 isopods on artificially prepared sand circles (2 m diameter) having exit holes and mounds similar to those left by the isopods and on circles without holes and mounds, and (ii) counting active and buried isopods 15 min after their release in the experimental arenas. The circles had two densities of holes and mounds: treatments 1 and 2 had 100 and 200 holes, respectively, while treatments 3 and 4 had 100 and 200 mounds, respectively. Other 30 isopods were released on sand circles without these holes and mounds (treatment 5). A significantly higher number of isopods buried in circles with holes and mounds (either inside or outside them), compared with experimental arenas without such structures. These results show that the beach surface heterogeneity resulting from holes and mounds would be one of the processes explaining the patchiness of T. spinulosus and thus, its zonation on the intertidal zones of sandy beaches of north-central Chile.     

Knowledge gaps and climate adaptation policy: a comparative analysis of six Latin American countries

ABSTRACT

This article identifies and analyzes some of the main knowledge gaps that affect the development of climate adaptation policies in the Latin American context. It is based on a comparative analysis of online survey results conducted among government officials working on climate adaptation in six countries of the region: Argentina, Brazil, Chile, Costa Rica, Paraguay and Uruguay. The article addresses four key issues. First, it identifies some of the critical knowledge deficits (missing or incomplete information) that affect climate adaptation policy making and implementation. Second, it addresses the obstacles and difficulties facing collaborative processes of knowledge production (co-production) between scientists and public policy actors. Third, it analyzes factors affecting knowledge uptake and use by policymakers. Finally, it identifies some of the main knowledge deficits specifically affecting the monitoring and assessment of climate adaptation policies and measures. Overall, the article provides a diagnosis of the main knowledge gaps facing climate adaptation policy in the Latin American countries studied. The results of this diagnosis can serve as input for a research and action agenda aiming to strength the interaction between science and policy on climate adaptation in Latin American countries.

Key policy insights

• The countries covered by the study suffer strong knowledge deficits related to the design, implementation and evaluation of adaptation policy.

• Collaborative modes of knowledge production in the field of climate adaptation do not tend to sustain over time. Climate change co-production processes tend to be project based, linked to specific initiatives rather than to institutionalized long-term policymaking or planning processes.

• The fragmentation and lack of integration of the knowledge available on the different aspects of climate adaptation issues deeply affect their usability in policy processes.

• Weak state capabilities to co-produce, manage and use knowledge in the policy process constitute a main barrier affecting the science-policy interface on climate adaptation issues.