Antonio Toscano

Freshwater ostracods as environmental tracers

This paper revises the response of freshwater ostracods to different environmental conditions and anthropogenic impacts, with a worldwide overview of the potential use of these microcrustaceans as bioindicators and several examples of applications in different scenarios. The development of either a single species or an ostracod assemblage is influenced by physical–chemical properties of waters (salinity, temperature, pH, dissolved oxygen), hydraulic conditions, bottom grain sizes or sedimentation rates. In addition to population and community changes, morphological and geochemical changes can also be detected in the ostracod carapace, which serves as a tracer of the water quality. All these features permit to delimit the spatial effects of urban sewages, mining effluents, agricultural wastes, watershed deforestation or road building. These data are the basis for the palaeoenvironmental reconstruction of cores, with an interesting application to archaeology. In addition, favourable results of recently developed bioassays, coupled with an important variability of local assemblages under changing conditions in both waters and sediments, suggest that these microcrustaceans may included between the most promising sentinels groups in freshwater areas. These microcrustaceans show high sensitivity to pesticides, herbicides, heavy metal pollution and oil inputs.

Distribution of heavy metals and pollution pathways in a shallow marine shelf: assessment for a future management

The spatial distribution and geoaccumulation indices of four heavy metals were investigated in very shallow marine sediments of southwestern Spain. Surface sediments were collected from 43 sites with water depth ranging from 3 to 20xa0m. High to very high pollution levels (Igeoxa0>xa04 for zinc, lead and copper) were detected near the end of the Huelva bank, whereas chromium shows a more hazardous distribution in the southwestern Spanish littoral. Low to moderate heavy metal contents (mainly zinc and lead) were also observed in other two areas at different water depths (Isla Cristina-Piedras River: 10–18xa0m water depth; Mazagón–Matalascañas: <10xa0m water depth), whereas unpolluted to moderately polluted sediments were detected in the very shallow zones (<8xa0m water depth) located between the mouths of the Guadiana and the Piedras Rivers. A regional scenario indicates a strong pollution of the adjacent marine areas by polluted inputs derived from the Tinto–Odiel rivers, with a partial transport of heavy metals by W–E littoral currents even 40xa0km eastward. The Guadiana River is an additional source of zinc–lead contamination near the Spanish–Portuguese border, mainly at water depths up to 10xa0m. All these rivers are affected by acid mine drainage processes, derived from millennial mining activities. This pollution affects the sediment quality even 40xa0km eastward.

Holocene palaeoenvironmental evolution of Saltés Island (Tinto and Odiel estuary, SW Spain) during the Roman period (1st century BC–5th century AD)

A multidisciplinary analysis of Holocene sediments from Saltés Island (Tinto-Odiel estuary, SW Spain) has allowed to differentiate eigth sedimentary facies, according to their textural characteristics, internal structure, paleontology and archaeological content. Its interpretation and the chronological datings carried out reconstruct a transition from a sandy tidal plain to a final occupation by a Roman salting (cetaria) between the 1st century BC to 5th century A. This evolution includes the deposit of washover fans derived from high-energy events between the 1st century BC to 3th century AD. The integration of these new data with others from previous research has allowed partially complete the palaeoenviromental reconstruction of the marine domain of the Tinto-Odiel estuary.ResumenEl análisis multidisciplinar de sedimentos holocenos procedentes de la isla Saltés, situada en el estuario de los ríos Tinto y Odiel (SO de España), ha permitido diferenciar ocho facies sedimentarias, de acuerdo a sus características texturales, estructura interna, contenido paleontológico y restos arqueológicos presentes. Su interpretación y las dataciones cronológicas efectuadas han permitido reconstruir una transición desde una llanura mareal arenosa a la ocupación final de la zona por una factoría romana de salazones (cetaria) entre los siglos I BC y V AD. Esta evolución incluye el depósito de washover fans derivados de la acción de eventos de alta energía entre los siglos I BC y III AD. La integración de estos nuevos datos con otros procedentes de investigaciones previas ha permitido completar parcialmente la reconstrucción paleoambiental del dominio marino del estuario de los ríos Tinto y Odiel.

First European record of Homiphoca (Phocidae: Monachinae: Lobodontini) and its bearing on the paleobiogeography of the genus

ABSTRACT Marine mammal fossils (except pinnipeds) have commonly been found in Pliocene marine siliciclastic layers of the Neogene Guadalquivir Basin in Southwest Spain. A few Neogene phocid innominate bones are known from the Western Paratethys and Western Atlantic. Here we describe a new innominate bone from the early Pliocene (5.3–3.6 Ma) of the Western Paratethys (Spain), which is typical of the subfamily Monachinae, and has a flattened ilium similar to representatives of the tribe Lobodontini, particularly Leptonychotes weddellii. Comparison with other fossil monachine innominates from North America, South America and South Africa reveals that this specimen represents the genus Homiphoca, but species classification remains premature. This is the first European record of the genus Homiphoca and has paleobiogeographic implications, questioning the geological age of the Varswater Formation ‘E’ Quarry, Langebaanweg, Cape Province of South Africa. This discovery from the eastern North Atlantic further implies a more regular transatlantic gene flow in Miocene and Pliocene times than today. We argue that during the Messinian-Zanclean crisis, monachines became isolated and retreated southward to lower latitudes, possibly due to climatic deterioration (during glacial stages) and competition from the cold-adapted phocines from the north. Abbreviations: NMNH: National Museum of Natural History, Smithsonian Institution, Washington, DC., USA; CMM: Calvert Marine Museum, Solomons, Maryland (USA); UTM: Universal Transverse Mercator Coordinate system

Predation on Ostracod Populations of Two North African Lagoons

Evidence of predation on the recent ostracod populations of Nador lagoon (Morocco) and El Melah lagoon (Tunisia), two semi-arid coastal areas of North Africa, is scarce. However, rare, bored valves have been extracted from the inner, very restricted areas of both lagoons. All these valves present cylindrical boreholes, an ichnofossil known as Oichnus simplex Bromley, 1981, near the central muscular field. Borehole diameters are not correlated with the dimensions the (length, height) of the bored valves. Predation had apparently focused on the adults and the last juvenile stages of either smooth, or punctuated species of ostracods.