Nigeria Institute for Oceanography and Marine Research
Nigeria Institute for Oceanography and Marine Research
de Prunele A.,French Research Institute for Exploitation of the Sea |
Ruffine L.,French Research Institute for Exploitation of the Sea |
Riboulot V.,French Research Institute for Exploitation of the Sea |
Peters C.A.,Center for Marine Environmental science |
And 15 more authors.
Geochemistry, Geophysics, Geosystems | Year: 2017
The Niger Delta is one of the largest hydrocarbon basin offshore Africa and it is well known for the presence of active pockmarks on the seabed. During the Guineco-MeBo cruise in 2011, long cores were taken from a pockmark cluster in order to investigate the state of its current activity. Gas hydrates, oil, and pore-water were sampled for geochemical studies. The resulting dataset combined with seismic data reveal that shallow hydrocarbon migration in the upper sedimentary section was focused exclusively within the pockmarks. There is a clear tendency for gas migration within the hydrate-bearing pockmarks, and oil migration within the carbonate-rich one. This trend is interpreted as a consequence of hydrate dissolution followed by carbonate precipitation in the course of the evolution of these pockmarks. We also demonstrate that Anaerobic Oxidation of Methane (AOM) is the main process responsible for the depletion of pore-water sulfate, with depths of the Sulfate-Methane Transition Zone (SMTZ) ranging between 1.8 and 33.4 m. In addition, a numerical transport-reaction model was used to estimate the age of hydrate-layer formation from the present-day sulfate profiles. The results show that the sampled hydrate-layers were formed between 21 and 3750 years before present. Overall, this work shows the importance of fluid flow on the dynamics of pockmarks, and the investigated cluster offers new opportunities for future cross-site comparison studies. Our results imply that sudden discharges of gas can create hydrate layers within the upper sedimentary column which can affect the seafloor morphology over few decades. © 2016. American Geophysical Union. All Rights Reserved.
Wei J.,University of Bremen |
Pape T.,University of Bremen |
Sultan N.,French Research Institute for Exploitation of the Sea |
Colliat J.-L.,Total S.A. |
And 11 more authors.
Marine and Petroleum Geology | Year: 2015
A joint research expedition between the French IFREMER and the German MARUM was conducted in 2011 using the R/V 'Pourquoi pas?' to study gas hydrate distributions in a pockmark field (1141-1199m below sea surface) at the continental margin of Nigeria. The seafloor drill rig MeBo of MARUM was used to recover sediments as deep as 56.74m below seafloor. The presence of gas hydrates in specific core sections was deduced from temperature anomalies recorded during continuous records of infrared thermal scanning and anomalies in pore water chloride concentrations. In situ sediment temperature measurements showed elevated geothermal gradients of up to 258°C/km in the center of the so-called pockmark A which is up to 4.6 times higher than that in the background sediment (72°C/km). The gas hydrate distribution and thermal regime in the pockmark are largely controlled by the intensity, periodicity and direction of fluid flow. The joint interaction between fluid flow, gas hydrate formation and dissolution, and the thermal regime governs pockmark formation and evolution on the Nigerian continental margin. © 2014 Elsevier Ltd.
Akinrotimi O.A.,Nigeria Institute for Oceanography and Marine Research |
Edun O.M.,Nigeria Institute for Oceanography and Marine Research |
Uka A.,Nigeria Institute for Oceanography and Marine Research |
Owhonda K.N.,Nigeria Institute for Oceanography and Marine Research
Journal of Fisheries and Aquatic Science | Year: 2012
This study is an attempt to evaluate public perception of mudskipper consumption, a delicacy in some fishing communities of Rivers State in Niger Delta area of Nigeria. One hundred and twenty structured questionnaires were randomly hstributedin ten communities spread across three local governments. The results of the survey showed that consumption of mudskipper was more popular among the old people than the younger ones. A greater number of people 82.50% considered mudskipper as fish, 10% as nuisance, 4.17% as snake and 3.32% as pest. Also, 83.33% of the respondents were favorably hsposed towards mudskipper 15.0% were negative and 1.67% were indifferent. The study revealed that there is no taboo in the consumption of mudskipper in these areas, any perceptions were observed personal to individual and not a communal affair. © 2013 Academic Journals Inc.
Ayo-Olalusi C.I.,Nigeria Institute for Oceanography and Marine Research
Journal of Fisheries and Aquatic Science | Year: 2014
This study presents the findings of the study on the length-weight relationship, condition factor and sex ratio of African mud catfish (Clarias gariepinus) reared in flow-through system tanks. During the study 154 fish samples including 76 females and 78 males ranging from 12.0-35.3 cm total body length and weighing between 12.2-450 g were studied. The parameters “a” and “b” of the length-weight relationship were estimated using the equation W = aLb while the condition factor was also calculated from the equation, K = 100 W/Lb. The regression coefficient “b” values for the length-weight relationship were 3.358, 3.391 and 3.372 for males, females and combined sexes, respectively. The result showed positive allometric growth exhibited by the species. The mean “K” value for the males was 0.8087±0.23, females 0.7884±0.09 while the combined sex was 0.7987±0.18 and there was no significant difference among the sexes. The sex ratio of males to females was 1: 1.02 and a chi-square test indicated no significant different (p>0.05) from 1:1 sex ratio. © 2014 Academic Journals Inc.