Biogenic silica and diatom thanatocoenosis in surface sediments below the Peru–Chile Current: controlling mechanisms and relationship with productivity of surface waters

2003 ◽  
Vol 48 (1-2) ◽  
pp. 71-90 ◽  
Author(s):  
O. Romero ◽  
D. Hebbeln
Keyword(s):  
Surface Waters ◽  
Biogenic Silica ◽  
Surface Sediments

Grain-size effect of biogenic silica in the surface sediments of the East China Sea

2014 ◽  
Vol 81 ◽  
pp. 29-37 ◽  
Author(s):  
Liang Wang ◽  
Dejiang Fan ◽  
Weiran Li ◽  
Yongjie Liao ◽  
Xilin Zhang ◽  
...  
Keyword(s):  
Grain Size ◽  
Size Effect ◽  
East China Sea ◽  
Biogenic Silica ◽  
Surface Sediments ◽  
East China ◽  
Grain Size Effect ◽  
The East China Sea ◽  
China Sea

Assessment of the Effect of Increasing Temperature On the Ecology and Assemblage Structure of Modern Planktic Foraminifers in the Caribbean and Surrounding Seas

2018 ◽  
Vol 48 (3) ◽  
pp. 251-272 ◽  
Author(s):  
Anna Jentzen ◽  
Joachim Schönfeld ◽  
Ralf Schiebel
Keyword(s):  
Surface Waters ◽  
Surface Sediments ◽  
Seawater Temperature ◽  
Chlorophyll Concentration ◽  
Caribbean Sea ◽  
Trophic Conditions ◽  
Near Surface ◽  
The Caribbean ◽  
Standing Stocks ◽  
The 1960S

Abstract Habitat patterns of subtropical and tropical planktic foraminifers in the Caribbean Sea were obtained from plankton samples collected in spring 2009 and 2013. The spatial distribution in surface waters (3.5 m water depth) and depth habitat patterns (surface to 400 m) of 33 species were compared with prevailing water-mass conditions (temperature, salinity, and chlorophyll-a concentration) and planktic foraminiferal test assemblages in surface sediments. Distribution patterns indicate a significant relationship with seawater temperature and trophic conditions. A reduction in standing stocks was observed close to the Orinoco River plume and in the Gulf of Paria, associated with high turbidity and concomitant low surface-water salinity. In contrast, a transient mesoscale patch of high chlorophyll concentration in the eastern Caribbean Sea was associated with higher standing stocks in near surface waters, including high abundances of Globigerinita glutinata and Neogloboquadrina dutertrei. Globorotalia truncatulinoides mainly lives close to the seasonal pycnocline and can be linked to winter conditions indicated by lower sea-surface temperatures (SSTs) of ∼20°C. Globigerinoides sacculifer and Globoturborotalita rubescens were associated with oligotrophic conditions in the pelagic Caribbean Sea during early spring and showed a synodic lunar reproduction cycle. The live assemblages in the water column from 2009 and 2013 were similar to those reported in earlier studies from the 1960s and 1990s and to assemblages of tests in the surface sediments. Minor differences in faunal proportions were attributed to seasonal variability and environmental differences at the local scale. An exception was the low relative abundance of Globigerinoides ruber in the Caribbean Sea in 2009 compared to surface sediment samples and plankton net samples collected in the 1960s and 1990s. Decreasing abundance of Gs. ruber white in the Caribbean Sea may be associated with increasing SSTs over past decades and changes in nutrient flux and primary production.

scholarly journals STUDY OF SOME ENVIRONMENTAL IMPLICATIONS DUE TO THE DISPOSAL OF ASHES FROM THE SÃO JERÔNIMO POWER STATION - RS

1997 ◽  
Vol 5 (5) ◽  
pp. 7-19
Author(s):  
Haidi D. Fiedler ◽  
Manuel Carneiro ◽  
Elba C. Teixeira
Keyword(s):  
Surface Waters ◽  
Surface Sediments ◽  
River Sediments ◽  
Cumulative Effect ◽  
Environmental Standards ◽  
Power Station ◽  
Short Term ◽  
Environmental Implications ◽  
Ph Values ◽  
Brazilian Legislation

The residues (ash agglomerates from combustion) generated at the São Jerônimo Power Station (UTSJ) were characterized with the main objective of evaluating, in pre-established conditions, the release of Cd, Co, Cu, Pb, Ni, Zn, Mn, Al, and Fe to the environment. Results revealed that, at different pH values, Fe, Zn, Mn, and Al were present in higher contents. In surface waters, for all sites analyzed, Fe and Al surpass the environmental standards imposed by Brazilian Legislation for class II surface waters. Surface sediments at the sites studied are basically composed by ashes from UTSJ, and a cumulative effect of deposition of the metals on the river sediments was verified. The experimental results are strongly indicative of an imperative need for a change in criteria in relation to the final disposal of residues from UTSJ. Otherwise, there is a high risk that the environmental impact in the short term will irreversibly damage the environment.

scholarly journals Global temperature calibration of the alkenone unsaturation index (UK′37) in surface waters and comparison with surface sediments

2006 ◽  
Vol 7 (2) ◽  
pp. n/a-n/a ◽  
Author(s):  
Maureen H. Conte ◽  
Marie-Alexandrine Sicre ◽  
Carsten Rühlemann ◽  
John C. Weber ◽  
Sonja Schulte ◽  
...  
Keyword(s):  
Surface Waters ◽  
Surface Sediments ◽  
Unsaturation Index ◽  
Global Temperature ◽  
Temperature Calibration

scholarly journals Nutrient dynamics and oceanographic features in the central Namibian upwelling region as reflected in δ15N-signals of suspended matter and surface sediments

Fossil Record ◽  
2011 ◽  
Vol 14 (2) ◽  
pp. 153-169 ◽  
Author(s):  
S. Meisel ◽  
U. Struck ◽  
K.-C. Emeis
Keyword(s):  
Surface Waters ◽  
Nutrient Dynamics ◽  
Surface Sediments ◽  
Sediment Cores ◽  
Deep Penetration ◽  
High Productivity ◽  
Surface Ocean ◽  
N Enrichment ◽  
Bottom Oxygen ◽  
Shelf Region

The study deals with the modern situation of the northern Benguela Upwelling, directing particular attention to the shelf region off central Namibia (21 to 24° S). At the centre of the investigation is the comparison of &delta;<sup>15</sup>N-records in surface sediments (&delta;<sup>15</sup>N<sub>sediment</sub>) with suspended particulate matter (&delta;<sup>15</sup>N<sub>SPM</sub>) from the surface ocean. In addition to that, water column profiles (including hydrographic data) provide an insight into changes of &delta;<sup>15</sup>N<sub>SPM</sub> with depth and elucidate potential offsets between &delta;<sup>15</sup>N<sub>SPM</sub> and &delta;<sup>15</sup>N<sub>sediment</sub>. The parallel spatial trend of &delta;<sup>15</sup>N<sub>sediment</sub> and surface ocean &delta;<sup>15</sup>N<sub>SPM</sub> shows that secondary processes are not so pronounced as to obliterate the signal generated in the surface waters. Highest &delta;<sup>15</sup>N-signatures are found right off the coast where water temperatures are lowest. Concomitantly high productivity rates and low bottom oxygen suggest the upwelling of denitrified source waters. With increasing distance offshore, &delta;<sup>15</sup>N declines unexpectedly, reaching a minimum above the shelf break. Beyond that, the trend reverses to "normal" with &delta;<sup>15</sup>N-signals continuously increasing towards the mesopelagic ocean. The decrease in &delta;<sup>15</sup>N<sub>sediment</sub> and surface ocean &delta;<sup>15</sup>N<sub>SPM</sub> with increasing distance to the coast disagrees with the concept of Rayleigh fractionation kinetics, viz. the progressive <sup>15</sup>N-enrichment of the nitrate pool as it is gradually used up by phytoplankton growth. On the basis of the available evidence, the downward trend of &delta;<sup>15</sup>N results from decreased relative nitrate consumption, resting on a combination of reduced primary production and the existence of an ulterior source of nutrients. Nutrient replenishment seems to occur via an additional upwelling front at the edge of the shelf as well as tapping of subsurface nitrate through sufficiently deep penetration of wind- and wave-induced mixing over large areas of the shelf. Both mechanisms are considered capable of working against the expected nutrient drawdown (i.e. <sup>15</sup>N-enrichment) as surface waters travel offshore. It is important to keep these caveats in mind when interpreting &delta;<sup>15</sup>N-variations in sediment cores retrieved from this area. <br><br> doi:<a href="http://dx.doi.org/10.1002/mmng.201100005" target="_blank">10.1002/mmng.201100005</a>

Sign in / Sign up

Export Citation Format

Share Document