Search results for "oceanography"
showing 10 items of 1567 documents
Spatial distribution of phytoplankton and picocyanobacteria in Lake Tanganyika in March and April 1998
2003
The spatial distribution of phytoplankton and picocyanobacteria was studied in Lake Tanganyika in relation to environmental factors. Sampling was conducted within three weeks during the wet season of 1998 when the water column stratification was most stable. The secchi depth varied between 11 and 16 m, except off the river Malagarasi (3 m). The depth of the euphotic zone was 33 to 56 m. Altogether, 218 phytoplankton taxa were identified. Their total biomass varied between 13 and 88 mg m−3 fresh weight. Picocyanobacteria were present at very high densities (104 to 6 × 10 5 cells ml−1). The influence of the river Malagarasi appeared to spread along the water surface because of the lower densi…
Water Temperature Increasing Caused Mastigias Papua Disappeared in Marine Lake Lenmakana Misool Raja Ampat Regency, West Papua
2020
Mastigias papua is a jellyfish that is trademark of marine lakes. Ongeim’l Tketau Lake in Palau, Hang Du I Lake in Vietnam, Kakaban Lake in Kalimantan, and Lenmakana Lake in Raja Ampat Papua are exotic tourist destinations because of presence of these biota in the lake. Water temperature is very influential on the life of a jellyfish because of its mutual symbiosis with brown algae zooxanthellae. Mastigias has totally disappeared in several places due to water temperature increasing, including Lenmakana Lake in the West Monsoon 2017/2018 and 2018/2019. The absence of Mastigias in this lake will be explained by recorded logger data installed in the lake and at sea. Secondary data from NOAA a…
Palaeontological Virtual Congress: A new way to make science
2019
On the first month of 2018, one of the authors (VDC) of this preface had an interesting idea: to hold a virtual congress. At first, he did not know of the existence of this kind of congress, but a quick internet search showed him that there were some examples in the fields of medicine and veterinary medicine; however, it had never been done in palaeontology. For that reason, with the help of other co-workers from the Universitat de València, Museo Paleontológico de Alpuente and Museu Valencià d’Historia Natural, we decided to undertake this adventure. Fil: Crespo Roures, Vicente Daniel. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. División Paleontología Vertebra…
Molecular evidence for cosmopolitan distribution of platyhelminth parasites of tunas (Thunnus spp.)
2007
Global distribution of platyhelminth parasites and their host specificities are not well known. Our hypothesis was that platyhelminth parasites of large pelagic fishes are common around the world. We analysed molecular variation in three different taxa of platyhelminth parasites infecting four species of tunas: yellowfin tuna (Thunnus albacares, Scombridae) from Western Australia, southern bluefin tuna (Thunnus maccoyii, Scombridae) from South Australia, Pacific bluefin tuna (Thunnus orientalis, Scombridae) from Pacific Mexico and northern bluefin tuna (T. thynnus, Scombridae) from two localities in the Mediterranean (Spain and Croatia). Comparisons of ITS2 and partial 28S rDNA demonstrated…
Element variability in the coralline alga Lithophyllum yemenense as archive of past climate in the Gulf of Aden (NW Indian Ocean)
2017
This study presents the first algal thallus (skeleton) archive of Asian monsoon strength and Red Sea influence in the Gulf of Aden. Mg/Ca, Li/Ca, and Ba/Ca were measured in Lithophyllum yemenense from Balhaf (Gulf of Aden) using laser ablation inductively coupled plasma mass spectrometry, and Mg/Ca ratio oscillation was used to reconstruct the chronology (34 y). Oscillations of element rates corresponding to the algal growth between 1974 and 2008 were compared with recorded climate and oceanographic variability. During this period, sea surface temperatures (SST) in Balhaf recorded a warming trend of 0.55 degrees C, corresponding to an increase in Mg and Li content in the algal thallus of 2.…
Modelling biogeochemical processes in sediments from the north-western Adriatic Sea: response to enhanced particulate organic carbon fluxes
2018
This work presents the result of a study carried out in the north-western Adriatic Sea, by combining two different types of biogeochemical models with field sampling efforts. A longline mussel farm was taken as a local source of perturbation to the natural particulate organic carbon (POC) downward flux. This flux was first quantified by means of a pelagic model of POC deposition coupled to sediment trap data, and its effects on sediment bioirrigation capacity and organic matter (OM) degradation pathways were investigated constraining an early diagenesis model by using original data collected in sediment porewater. The measurements were performed at stations located inside and outside the ar…
Distribution and ecology of the Globigerinoides ruber — Globigerinoides elongatus morphotypes in the Azores region during the late Pleistocene-Holoce…
2018
Abstract Globigerinoides ruber is the dominant taxon in the North Atlantic Subtropical Gyre, nowadays limited to the north by the Azores Current. It is highly sensitive to recent and late Pleistocene Azores Front Current System variability. In this study, we analyse the distribution of five individual morphotypes of the G. ruber – G. elongatus plexus (G. ruber s.s., G. ruber cyclostoma type, G. elongatus, G. elongatus cf.1, G. elongatus pyramidical type) and G. ruber kummerform gr. in a core (ATA13-OF-KT1) collected southwest of the Azores islands and located in a strategical position near the present-day boundary of the Subtropical Gyre/Azores Front Current System (STG/AFCS). Micropaleonto…
Changement climatique et surcotes marines, quel avenir pour les plages camarguaises ?
2012
2 pages; National audience
BIOGEOGRAPHY AND MACROECOLOGY OF ANTARCTIC AND SUB-ANTARCTIC ECHINOIDS USING A GEOGRAPHIC INFORMATION SYSTEM.
2010
participant; Many features already show how Polar seas are impacted by present-day global warming. To cope with new climate-induced changes and survive, Antarctic and Subantarctic marine organisms can either migrate or adapt to new prevailing conditions. New biotic interactions between Southernmost species and Subantarctic invaders can be expected, as new biogeographical distributions have already been documented. Because they are biologically and ecologically well diversified, echinoids play an important part in Antarctic benthic communities. Moreover, symbioses associated to cidarid echinoids make them even more crucial for benthic diversity. The biogeographical mapping of Antarctic echin…
Late Cretaceous changes in continental configuration: toward a better-ventilated ocean?
2017
International audience; Oceanic anoxic events (OAEs) are large-scale events of oxygen depletion in the deep ocean that happened dur-ing pre-Cenozoic periods of extreme warmth. Last global OAE occurred at the Cenomanian-Turonian boundary(OAE2) prior to the Late Cretaceous long term cooling. Ever since, and despite the occurrence of warming events,Earth no more experienced such large-scale anoxic conditions. Here we explore the role of major continentalconfiguration changes occurring during the Late Cretaceous on oceanic circulation modes through numerical sim-ulations using a General Circulation Model (GCM), that we confront to existing neodymium isotope data ("Nd).Except from a continuous d…