Search results for "Oceano"
showing 10 items of 1626 documents
Population response during an Oceanic Anoxic Event: The case of Posidonotis (Bivalvia) from the Lower Jurassic of the Neuquén Basin, Argentina
2019
Benthonic marine species show a wide range of biological reactions to seawater chemical changes through time, from subtle adjustments to extinction. The Early Toarcian Oceanic Anoxic Event (T-OAE) was recently recognized in the Neuquén Basin, Argentina, confirming its global scope. The event was identified chemostratigraphically on the basis of a relative increase in marine organic carbon and a characteristic negative carbon-isotope excursion (δ13Corg) in bulk rock and fossil wood in the upper Pliensbachian–lower Toarcian interval in the Arroyo Lapa section (Neuquén). Simultaneously with collection of lithological samples, a high-resolution biostratigraphical survey was carried out, and the…
Molecular data attest to the occurrence of autochthonous Daphnia pulex (Crustacea, Branchiopoda) populations in Sicily, Italy
2021
Biological invasions are known to be among the most important threats to the long-term conservation of native biota, and their effects might be even more difficult to contrast when they are cryptic, i.e., when the non-native invaders cannot be easily recognised based on morphology, and can thus be confused with native taxa. Such cryptic invasions are known to widely occur in the cladoceran genus Daphnia O.F. Müller, 1785, so that the actual distribution and status of most species and lineages need to be checked with a genetic approach. In the frame of this work, we investigated if the Sicilian populations of D. (Daphnia) pulex Leydig, 1860 belonged to the allochthonous North American lineag…
Warmer climates boost cyanobacterial dominance in shallow lakes
2011
Dominance by cyanobacteria hampers human use of lakes and reservoirs worldwide. Previous studies indicate that excessive nutrient loading and warmer conditions promote dominance by cyanobacteria, but evidence from global scale field data has so far been scarce. Our analysis, based on a study of 143 lakes along a latitudinal transect ranging from subarctic Europe to southern South America, shows that although warmer climates do not result in higher overall phytoplankton biomass, the percentage of the total phytoplankton biovolume attributable to cyanobacteria increases steeply with temperature. Our results also reveal that the percent cyanobacteria is greater in lakes with high rates of ligh…
Carbon photoassimilation by sharply stratified phototrophic communities at the chemocline of Lake Arcas (Spain)
1998
Three populations of phototrophic microorganisms were found closely stratified in the chemocline of the holomictic Lake Arcas. Cryptomonas spp. reached a maximum population density in microaerobic waters above dense plates of Oscillatoria cf. ornata and Chromatium weissei, whose maxima were found in the deeper sulfide-rich waters. High photoassimilation rates were found during the stratification period at the chemocline (up to 197.63 mg C m−3 h−1), especially at depths at which maximal densities of prokaryotic phototrophs were located, whereas much lower values were observed in the mixed zone of the lake. Despite these high rates, the contribution of carbon photoassimilation at the chemocli…
Insular stock identification of <EM>Serranus atricauda</EM> (Pisces: Serranidae) through the presence of <EM>Ceratothoa steindachne…
2004
Ceratothoa steindachneri (Isopoda: Cymothoidae) and Pentacapsula cutanea (Myxozoa: Pentacapsulidae) parasites infecting the blacktail-comber ( Serranus atricauda ) were considered suitable as biological tags for stock identification around the islands of La Palma and Gran Canaria, in the Western and Eastern areas of the Canarian archipelago, respectively. The ecological parameters of both species differed significantly between the islands. While individuals caught off La Palma showed a high degree of infection by the isopod, a single infected fish was found off Gran Canaria. Also, the myxozoans showed a high level of infection on fish from Gran Canaria but it was reported on only a single s…
Reventilation Episodes During the Sapropel S1 Deposition in the Eastern Mediterranean Based on Holococcolith Preservation
2019
Organic-rich layers (sapropels), preserved in eastern Mediterranean marine sediment records, represent pronounced perturbations to thermohaline circulation and environmental conditions in the basin, in response to enhanced African monsoon activity and subsequent massive freshwater discharge. During the most recent event, Sapropel S1 formed between 10.8 and 6.1 ka, when freshwater-driven stratification caused seafloor anoxia below ~1,800-m depth, as a result of both failure of deep water formation and enhanced productivity. Here we analyze coccolith assemblages from the open eastern Mediterranean that form a west-east transect across the basin and provide insights on past environmental chang…
Correlation between the level of the potential biomarker, heat-shock protein, and the occurrence of DNA damage in the dab, Limanda limanda: a field s…
2000
In the present study, heat-shock protein of M-r 70 kDa (HSP70), a marker of cellular stress response, was validated as a potential biomarker under field conditions. The dab, Limanda limanda (female, size greater than or equal to 25 cm, spawning maturity stage 2) was used as the indicator organism. The data on HSP level were correlated with the occurrence of DNA damage, measured in the same specimens of L. limanda, to prove the usefulness of the method. The area under investigation was the North Sea. Four locations were selected: station N01, close to Heligoland, in the North Sea; station N04 at the Dogger Bank; station N06 at the Firth of Forth; and station G08 in the English Channel. Ten a…
Hoeflea alexandrii sp. nov., isolated from the toxic dinoflagellate Alexandrium minutum AL1V
2006
A Gram-negative, aerobic, non-symbiotic bacterium (AM1V30(T)) was isolated from the toxic dinoflagellate Alexandrium minutum AL1V. On the basis of 16S rRNA gene sequence similarity, strain AM1V30(T) was most closely related (97.4 % similarity) to the type strain of Hoeflea marina, which belongs to the family Phyllobacteriaceae within the order Rhizobiales of the class Alphaproteobacteria. A polyphasic approach was used to clarify the taxonomic position of strain AM1V30(T). During the course of this study, a second species was described by others as belonging to the genus Hoeflea, namely Hoeflea phototrophica; it showed a somewhat higher level of 16S rRNA gene sequence similarity with respec…
Neptuniibacter caesariensis gen. nov., sp. nov., a novel marine genome-sequenced gammaproteobacterium.
2007
7 pages, 1 figure, 1 table
Vulnerability of the North Water ecosystem to climate change
2021
High Arctic ecosystems and Indigenous livelihoods are tightly linked and exposed to climate change, yet assessing their sensitivity requires a long-term perspective. Here, we assess the vulnerability of the North Water polynya, a unique seaice ecosystem that sustains the world’s northernmost Inuit communities and several keystone Arctic species. We reconstruct mid-to-late Holocene changes in sea ice, marine primary production, and little auk colony dynamics through multi-proxy analysis of marine and lake sediment cores. Our results suggest a productive ecosystem by 4400–4200 cal yrs b2k coincident with the arrival of the first humans in Greenland. Climate forcing during the late Holocene, l…