Geographical ecology of the symbiotic crabs Libinia ferreirae and Libinia spinosa: Distributional patterns in south and south-eastern coast of Brazil

The Brazilian coast is home to two species of Majoid crabs: Libinia ferreirae and Libinia spinosa, with similar habits, as they live in symbiosis with the jellyfish Lychnorhiza lucerna during their juvenile stage and dwell on the bottom of the ocean near the coast when adults. This study investigated the spatial and temporal distribution of L. ferreirae and L. spinosa during different ontogenic phases on the south and south-eastern coast of Brazil, between latitudes 22º and 27ºS. Our results showed that both species have different distributions during their development in the three studied regions. Libinia ferreirae were more abundant associated with jellyfish, and L. spinosa were more abundant in the free-living phase. Environmental factors, especially temperature and salinity, for associated and free-living crabs, respectively, are the main factors that need to be supported for the establishment of these specimens. We were able to identify that the presence or absence of hosts (given the ecological interactions between the species) is determinant in finding the associated crabs. Geographical variations (morphology of the regions, marine currents and the strength of the tide) are linked directly to the movement of the jellyfish hosts to the coast, influencing the abundance of L. fereirae and L. spinosa populations and affecting their distribution patterns. We can infer that both species are connected with other populations because of the association with the jellyfish, crabs could be passively transported along the south and south-eastern coast of Brazil, maintaining the connection between metapopulations.     

Cold seep communities in the deep eastern Mediterranean Sea: composition, symbiosis and spatial distribution on mud volcanoes

Two mud volcano fields were explored during the French–Dutch MEDINAUT cruise (1998) with the submersible NAUTILE, one south of Crete along the Mediteranean Ridge at about 2000 m depth (Olimpi mud field) and the other south of Turkey between 1700 and 2000 m depth (Anaximander mud field) where high methane concentrations were measured. Chemosynthetic communities were observed and sampled on six mud volcanoes and along a fault scarp. The communities were dominated by bivalves of particularly small size, belonging to families commonly found at seeps (Mytilidae, Vesicomyidae, Thyasiridae) and to Lucinidae mostly encountered in littoral sulfide-rich sediments and at the shallowest seeps. Siboglinid polychaetes including a large vestimentiferan Lamellibrachia sp. were also associated. At least four bivalve species and one siboglinid are associated with symbiotic chemoautotrophic bacteria, as evidenced by Transmission Electronic Microscopy and isotopic ratio measurements. Among the bivalves, a mytilid harbors both methanotrophic and sulfide-oxidizing bacteria. Video spatial analysis of the community distribution on three volcanoes shows that dense bivalve shell accumulations (mainly lucinids) spread over large areas, from 10% to 38% of the explored areas (2500–15000 m²) on the different volcanoes. Lamellibrachia sp. had different spatial distribution and variable density in the two mud volcano fields, apparently related with higher methane fluxes in the Anaximander volcanoes and maybe with the instability due to brines in the Olimpi area. The abundance and richness of the observed chemosynthetic fauna and the size of some of the species contrast with the poverty of the deep eastern Mediterranean. The presence of a specialized fauna, with some mollusk genera and species shared with other reduced environments of the Mediterranean, but not dominated by the large bivalves usually found at seeps, is discussed.     

Report on the 4th International Meeting of the IUGS Lower Cretaceous Ammonite Working Group, the “Kilian Group” (Dijon, France, 30th August 2010)

The 4th Kilian Group meeting (Dijon, France, 30th August 2010) focused on the Aptian and Albian Stages. For the Aptian, a two-fold division of the stage was adopted for the Mediterranean area with a boundary between the Dufrenoyia furcata and Epicheloniceras martini Zones. The main changes to the zonal scheme concern the Lower Aptian with: the introduction of a Deshayesites luppovi Subzone in the upper part of the Deshayesites oglanlensis Zone; the replacement of Deshayesites weissi by Deshayesites forbesi as new index-species of the second interval zone; the introduction of a Roloboceras hambrovi Subzone in the upper part of the D. forbesi Zone; and the subdivision of the D. furcata Zone into the D. furcata and Dufrenoyia dufrenoyi Subzones. For the Albian, the upper part of the Douvilleiceras mammillatum Zone (Lower Albian) is now characterized by a Lyelliceras pseudolyelli Subzone. The main amendments concern the Upper Albian. The base of this substage is defined by the base of the Dipoloceras cristatum Zone. Above it, the Upper Albian zonal scheme comprises in stratigraphic order the Mortoniceras pricei, Mortoniceras inflatum, Mortoniceras fallax, Mortoniceras rostratum, Mortoniceras perinflatum and Arrhaphoceras briacensis Zones.     

Freshwater seepages and ephemeral macroalgae proliferation in an intertidal bay: II. Effect on benthic biomass and metabolism

Intertidal soft-sediments biomass and metabolism are naturally heterogeneous in time and space at different scales. Particular perturbations such as freshwater seepages and seasonal proliferation of ephemeral macroalgae can intermittently and/or locally create additional variability in these systems. Since the impacts of such environmental stresses on natural processes are not well understood, the hypothesis that they would affect the functioning of the benthic system was tested. An intertidal bay whose structure and functioning has been previously described and where a carbon budget has been calculated, was chosen. The results showed that the metabolism of the intertidal sediments was greatly impacted by the above perturbations. Freshwater seepage increased meiofauna and microalgae biomasses and enhanced the total benthic metabolism (increasing community respiration and gross primary production until 4 and 2 fold respectively) without altering its seasonal trend. Ephemeral macroalgae proliferation had a more important effect on the total benthic metabolism, increasing community respiration and gross primary production 8 and 12 fold respectively and leading to a change in the seasonal trend.     

Empirical assessment of flood wave celerity–discharge relationships at local and reach scales

ABSTRACT

An accurate comprehension of celerity (flood wave speed) dynamics is a key step for understanding flood wave propagation in rivers. We present the results of empirically estimated celerity values in 12 Brazilian rivers, and analyse the behaviour of celerity–discharge relationships (CxQ). Celerity was estimated with a reach-scale (RS) method, based on the peak travel time between stations; and with a local-scale (LS) method, based on the derivative of discharge–cross-section area relationships surveyed at gauging stations. The results indicate that the magnitudes of celerity values obtained by the methods are reasonably comparable, and can rarely be considered constant, varying with river discharge. Three reaches presented differing CxQ relationships at local and reach scales, which suggests that in situ cross-sections at gauging stations should not be extrapolated as representative of the whole reach for flood routing studies, and that CxQ relationship assessments might provide relevant insights for hydrological modelling.     

Discrimination between different water bodies from a multilayered aquifer (Kaluvelly watershed,India): Trace element signature

In the multilayered aquifer of Kaluvelly (India), comprising various sedimentary layers overlying a charnockitic basement, concentrations of trace elements were measured in aquifer formations and in groundwaters to identify geochemical tracers for water bodies. The two main sandstones (Cuddalore and Vanur) originate from the charnockites and the Cuddalore sandstone has experienced lateritization. In the studied area, two charnockite end-members were identified: a dioritic and a granitic one. Mineralogical composition and whole-rock Ti concentrations confirmed the charnockite which displayed the granitic composition as the parent rock of the two sandstones. Titanium distribution indicates that the Cuddalore sandstone originates from a more intense weathering of the parent material than the Vanur sandstone. Despite extensive differences in trace element contents recorded in aquifer formations, only a few trace elements were suitable to distinguish the water bodies. Among soluble elements, Li (in the Vanur aquifer) and Ba (in the charnockite and carbonaceous aquifers) can be used as tracers. As the input of these elements in solution is mainly regulated by the available stock, for a given mineralogical origin there is a direct link between the aquifer formation composition and water signature. With the exception of As, concentrations of redox-sensitive elements were not preserved during pumping because of oxidation, preventing their use as tracers. Low-mobility elements such as La, Ce, Th, Zr, Nb, Hf, or Ta were too insoluble to be detected in waters and/or to record the aquifer formation signature. Their input in solution was not regulated by the available stock but by the dissolution rate of rock-forming minerals. Only Ti can be used to distinguish between two out of the three aquifers (charnockite and Vanur). The specific behavior of Ti recorded in these waters may be linked to rutile inclusions within plagioclases and to the influence of climate on Ti solubility.     

Treatment of Acid Mine Drainage (AMD) in South Brazil: Comparative active processes and water reuse

This work describes AMD techniques of neutralization, with lime, flocculation of the precipitates and comparative flocs/liquid separation by flotation with microbubbles or by lamellar settling (LS). The AMD treated water was characterized by its quality for recycling in terms of inorganic or organic elements, suspended or dissolved solids, among others. Two types of flocs were formed, “aerated” or not, in a special flocculation reactor, patented by this research group (RGF^®). Aerated flocs formed (within seconds) entered into contact with microbubbles under high shearing and raised-up at rates > 120 mh^− 1 allowing a rapid solid–liquid separation by flotation (HR-high rate), at about 13–15 m³m^− 2 h^− 1 loading capacity. Conversely, the non-aerated flocs settled at about 5–6 m h^− 1 in a lamella settler. Both AMD treatment techniques showed similar efficiencies (removal of ions > 90%) but the separation by lamella settling presented advantages, namely less reagents (no flotation collector required), lower power requirements and easier to operate. The operating costs (approximate values) of the AMD treatment by LS at pH 9 reaches about 0.3 US$ m^− 3 against 0.6 US$ m^− 3 for the HR-flotation process. Results found were proved to be similar to those found in recent ADM treatment installations in South Brazil. The quality of the treated water is fairly good, nearly free of heavy metals ion, low BOD (biological oxygen demand) and TOC (total organic content), low solids content and may be readily reused for irrigation, industrial processes and as wash water (among others, streets, vehicles, dust control). However, there is a need to extend the use of this treated water resource, but this, at least in Brazil, has not been legislated properly. It is concluded that this research will contribute in the discussion of this old and complex problem in acid mining effluents worldwide.