Ontogenic shifts in predatory roles involving two invasive species

The red swamp crayfish, Procambarus clarkii, and the eastern mosquitofish, Gambusia holbrooki have been introduced worldwide, but the interactions between these invasive species are not well known. The effects of crayfish presence, crayfish size and water depth on the consumption of G. holbrooki by P. clarkii were analyzed, as were the effects of mosquitofish presence and water depth on the consumption of recently hatched crayfish (RHC) by mosquitofish. To better understand this subject we conducted aquaria and open air mesocosm experiments simulating a rice field section. Aquarium experiments showed that P. clarkii consumes G. holbrooki and that G. holbrooki consumes RHC. Adult crayfish size did not significantly affect the consumption of mosquitofish and water depth had no effect on the consumption of G. holbrooki by P. clarkii and vice versa. In the outdoor mesocosm experiments P. clarkii caused no statistically significant effect on G. holbrooki numbers or biomass when compared with controls without crayfish. In spite of this, the analysis of crayfish stomach contents clearly demonstrated that several G. holbrooki individuals were consumed, indicating that crayfish can profit from the presence of G. holbrooki. Results from our study suggest that in shallow pools there are strong interactions between the two invasive species since adult crayfish predate mosquitofish and mosquitofish predate recently hatched crayfish. Therefore, there are bidirectional trophic interactions between these invasive species which change depending on their relative size. We believe that these interactions should become more relevant in confined areas such as small shallow pools formed during the late summer and autumn.     

Palynological and geochemical response to environmental changes in the Lower Cretaceous in the Outer Western Carpathians; a record from the Silesian unit, Czech Republic

Rich dinoflagellate cyst assemblages recorded from the Vendryne Formation, Tesin Limestone, and Hradiste Formation of the Silesian unit, Czech Republic are presented. The results of a qualitative and quantitative study of dinoflagellate cysts are presented and discussed. Age-assessment of the sediments based on 86 species suggests a Late Tithonian to Early Berriasian age for the Vendryne Formation and a Late Berriasian (Otopeta Ammonite Zone) to the basal part of the Late Valanginian (Verrucosum Ammonite Zone) age for the Tesin Limestone. Pelitic flyschoid sediments of the Hradiste Formation belong to the Late Valanginian - Early Hauterivian age. Quantitative palynological study and carbon isotope analysis were applied to understand the change from the grey clays to dark grey clays sedimentation. The dinoflagellate cyst assemblages show deposition in a shallow-sea environment. An increasing amount of sporomorphs towards the overlying layers (they are the most abundant in the Hradiste Formation) shows a growing supply of terrestrial material at the same time. The values of δ¹³C increased significantly from a level of 0.43 or 0.75-1.81‰ in the Late Valanginian. This change probably indicates an increase in organic matter storage and perturbation of the carbon cycle connected with the dark grey clays sedimentation.     

Assessing Decomposition Rates of Rhizophora mangle and Laguncularia racemosa Leaves in a Tropical Mangrove

Studies exploring leaf decomposition in mangroves in the Brazilian northeast are scarce. Therefore, in a mangrove of the Cachoeira River estuary at Ilhéus, Bahia, the decomposition of senescent leaves of Rhizophora mangle L. and Laguncularia racemosa Gaertn was studied. The litter-bag method and the Olson exponential model were applied to estimate the decomposition rates. The decay pattern of leaf material of both species was similar to those reported in the literature, with rapid initial weight loss, followed by a deceleration and period of slow weight loss. L. racemosa had the highest decay constants at all the study sites which suggest that their leaves are more easily degraded than those of R. mangle. The constantly submerged site presented the highest decay constants of 0.022 g g^?1 day^?1 for R. mangle and 0.031 g g^?1 day^?1 for L. racemosa. Most (95 %) of the leaf material of the two species was lost in 135 and 98 days, respectively. Benthic macrofauna organisms were recorded in the litter bags from the fifth day after the start of the experiment. Such organisms play a key role in the first phase of decomposition in this mangrove system. The decay constants of the leaf litter were generally higher than those reported in other tropical and subtropical regions. This suggests that differences in the process of decomposition are in response to environmental conditions at each location.     

Salt kinematics and regional tectonics across a Permian gas field: a case study from East Frisia, NW Germany

This study presents a reconstruction of the tectonic history of an Upper Rotliegend tight gas field in Northern Germany. Tectonism of the greater study area was influenced by multiple phases of salt movement, which produced a variety of salt-related structural features such as salt walls, salt diapirs as well as salt glaciers (namakiers). A sequential 2D retro-deformation and stratal backstripping methodology was used to differentiate mechanisms inducing salt movement and to discuss their relation to regional tectonics. The quantitative geometric restoration included sedimentary balancing, decompaction, fault-related deformation, salt movement, thermal subsidence, and isostasy to unravel the post-depositional tectonic overprint of the Rotliegend reservoir rock. The results of this study indicate that reactive salt diapirism started during an Early Triassic interval of thin-skinned extensional tectonics, followed by an active diapirism stage with an overburden salt piercement in the Late Triassic, and finally a period of intensive salt surface extrusion and the formation of salt glaciers (namakiers) in Late Triassic and Jurassic times. Since the Early Cretaceous, salt in the study area has been rising by passive diapirism.     

Water quality and risk assessment of dug wells: a case study for a poor community in the city of São Paulo, Brazil

Sparsely populated areas, or peripheral communities commonly lack access to a public water supply and sewerage systems. The inhabitants of these areas must make use of excavated wells to provide their water needs, and cesspits for domestic wastewater disposal. These on-site sanitation systems can release pathogens and nutrients into shallow groundwater. These poor communities urgently require cheap and efficient techniques for the detection of sanitary conditions, in order to prevent contamination of the water resources supplied by dug wells. The sanitary risk assessment methodology, applied in an irregular settlement south of the city of São Paulo, was based on a questionnaire with yes/no questions (risk factors), which allowed the identification of problems related to the well construction and operation, and the presence of potential contamination sources in its vicinity. These risk factors were compared against nitrate and bacterial analysis using the clustering statistical method, to verify the relationship between contamination and certain aspects surveyed in the questionnaire. Questions that were more related to contaminated wells were those concerning the presence of cover and its integrity; gaps between mouth and cover; the surrounding pavement and presence of ground irregularities; infiltration in the well casing; water-suspended materials; and proximity to contamination sources. Contamination models based on variograms allowed to observe that bacterial contamination presented a strong localized component, which was associated frequently with the way residents handled the wells, whereas nitrate contamination was related more to a regional (spatial) component; that is, the distance between wells and cesspits.     

Non-glacial paleoenvironments and the extent of Weichselian ice sheets on Severnaya Zemlya, Russian High Arctic

The extent of the Barents-Kara Sea ice sheet (northern Europe and Russia) during the Last Glacial Maximum (LGM), in Marine Isotope Stage (MIS) 2 is controversial, especially along the southern and northeastern (Russian High Arctic) margins. We conducted a multi-disciplinary study of various organic and mineral fractions, obtaining chronologies with ¹⁴C and luminescence dating methods on a 10.5 m long core from Changeable Lake (4 km from the Vavilov Ice Cap) on Severnaya Zemlya. The numeric ages indicate that the last glaciation at this site occurred during or prior to MIS 5d-4 (Early Middle Weichselian). Deglaciation was followed by a marine transgression which affected the Changeable Lake basin. After the regression the basin dried up. In late Middle Weichselian time (ca 25–40 ka), reworked marine sediments were deposited in a saline water body. During the Late Weichselian (MIS 2), the basin was not affected by glaciation, and lacustrine sediments were formed which reflect cold and arid climate conditions. During the termination of the Pleistocene and into the Holocene, warmer and wetter climate conditions than before led to a higher sediment input. Thus, our chronology demonstrates that the northeastern margin of the LGM Barents-Kara Sea ice sheet did not reach the Changeable Lake basin. This result supports a modest model of the LGM ice sheet in northern Europe determined from numeric ice sheet modelling and geological investigations.     

Dynamical features of near-inertial motions in global ocean based on the GDP dataset from 2000 to 2019

Based on the latest oceanic surface drifter dataset from the global drifter program during 2000–2019, this study investigated the global variation of relative frequency shift(RFS), near-inertial energy(NIE) and inverse excess bandwidth(IEB) of near-inertial motions, and analyzed their relations with oceanic mesoscale dynamics, relative vorticity and strain. Compared with previous works, we have some new findings in this study:(1) the RFS was high with negative values in some regions in which we found a significant blue shift of the RFS in the equatorward of 30°N(S) and from 50°N to 60°N in the Pacific, and a red shift in the western boundary currents and their extension regions, the North Atlantic and the Antarctic Circumpolar Current regions;(2) more peak values of the NIE were found in global regions like the South Indian Ocean, the Luzon Strait and some areas of the South Ocean;(3) the global distribution of the IEB were characterized by clear zonal bands and affected by vorticity and wind field;(4)the RFS was elevated as the absolute value of the gradient of vorticity increased, the IEB did not depend on the gradient of vorticity, and the eddy kinetic energy(EKE) weakened with the decrease of the absolute value of RFS;(5) the NIE decreased with increasing absolute value of the relative vorticity and the gradient of vorticity, but it increased with increasing strain and EKE when EKE was larger than 0.003 2 m~2/s~2.     

Jarosite stability on Mars

Jarosite, a potassium (sodium) iron sulphate hydrated mineral, has recently been identified on the martian surface by the Opportunity rover. Using recent thermochemical data [Drouet and Navrotsky, 2003, Geochim. Cosmochim. Acta 67, 2063-2076; Forray et al., 2005, Geochim. Cosmochim. Acta, in press], we calculate the equilibrium decomposition curve of jarosite and show that it is thermodynamically stable under most present martian pressures and temperatures. Its stability makes jarosite potentially useful to retain textural, chemical, and isotopic evidence of past history, including possible biological activity, on Mars.