scholarly journals Distribution patterns of Recent pteropods in surface sediments of the western continental shelf of India

2005 ◽  
Vol 24 (1) ◽  
pp. 39-54 ◽  
Author(s):  
Arun Deo Singh ◽  
Neelakantan Ravindran Nisha ◽  
Thadickal Viswanathan Joydas
Keyword(s):  
Continental Shelf ◽  
Surface Sediments ◽  
Salinity Gradient ◽  
Distribution Patterns ◽  
Qualitative And Quantitative ◽  
Profound Influence ◽  
Minimum Zone ◽  
Quantitative Analyses ◽  
Oxygen Minimum ◽  
Upper Slope

Abstract. This paper is the first contribution to the knowledge of pteropods in surficial sediments of the entire western continental shelf of India. Both qualitative and quantitative analyses of pteropod assemblages were carried out on 50 coarse fractions (>125 μm) of topmost portions of grab samples recovered along 12 transects covering the inner shelf to the upper slope (30–200 m water depths). The distribution of eight significant species was mapped. The resultant maps were correlated with the bathymetric, hydrographic and aragonite preservation conditions in the investigated area. This study reveals a bathymetric control over the distribution of Limacina inflata, Creseis acicula and Creseis chierchiae across the shelf. Furthermore, a marked difference in vertical salinity gradient from south to north along the shelf appears to have a profound influence on the abundance of these species. The pteropod shells in sediments of the northern offshore region with anoxic bottom conditions are generally well preserved, unlike the southern region, where oxygen concentration of the bottom water is relatively high enough to cause dissolution or even elimination of many shells of the most susceptible pteropods like C. acicula and C. chierchiae. The variation in the intensity of the oxygen minimum zone along the western continental shelf of India has significant influence upon the distribution pattern of Clio convexa.

scholarly journals FORAMINIFERA CHECK LIST AND THE MAIN SPECIES DISTRIBUTION IN THE AVEIRO LAGOON AND ADJACENT CONTINENTAL SHELF (PORTUGAL)

2019 ◽  
Vol 4 (1) ◽  
pp. 1-52 ◽  
Author(s):  
Maria Virgínia Alves Martins ◽  
Johann Hohenegger ◽  
Fabrizio Frontalini ◽  
Cristina Sequeira ◽  
Paulo Miranda ◽  
...  
Keyword(s):  
Continental Shelf ◽  
Distribution Patterns ◽  
Check List ◽  
Outer Continental Shelf ◽  
Depth Functions ◽  
Main Species ◽  
Components Analysis ◽  
Foraminíferos Bentónicos ◽  
Aveiro Lagoon ◽  
Upper Slope

This work is based on a compilation of benthic foraminiferal data collected in the Aveiro Lagoon and in the adjacent continental shelf and upper slope (center of Portugal). It intends to provide an overall analysis from transitional to the outer continental shelf of the occurrence and distribution of species in living and to present updated taxonomic data and illustrations of most of the species found in the in the Aveiro Lagoon and in the adjacent continental shelf including in total assemblages. Cluster analysis (CA) and Principal Components Analysis (PCA) interpreted as depth functions allow us to identify the main species in different ecoenvironments and sectors of the study area. The most unusual living assemblage was documented in the lagoon inlet under very strong tidal currents activity, composed mostly by the following species (both in living and total assemblages): Rotaliammina concava, Lepidodeuterammina ochracea, Quinqueloculina seminula, Gavelinopsis praegeri, Paratrochammina haynesi, Remaneica helgolandica and Remaneicella gonzalezi. The distribution patterns of some Trochamminidae and Remaneicidae species whose ecology and distribution pattern are poorly known, have proved to be a marker of more or less hydrodynamic and stable/unstable environments in coastal and transitional marine environments. OCORRÊNCIA DE FORAMINÍFEROS E DISTRIBUIÇÃO DAS PRINCIPAIS ESPÉCIES NA LAGOA DE AVEIRO E NA PLATAFORMA CONTINENTAL ADJACENTE (PORTUGAL)ResumoEste trabalho baseia-se numa compilação de dados foraminíferos bentónicos recolhidos na Laguna de Aveiro e na plataforma continental adjacente (centro de Portugal). Pretende efetuar uma análise geral da distribuição de espécies nas associações vivas e totais (vivas e mortas) na área de estudo, em função da profundidade. Pretende ainda apresentar dados taxonómicos e ilustrações da maioria das espécies encontradas na Laguna de Aveiro e na plataforma continental adjacente. A análise de agrupamento (CA) e a análise de componentes principais (PCA), em função da profundidade, permitem identificar as principais espécies em diferentes ecossistemas e setores da área de estudo. A associação viva mais invulgar foi encontrada na embocadura da Laguna de Aveiro, um ambiente sujeito a forte corrente de maré. Essa associação era composta principalmente pelas seguintes espécies (na associação viva e total): Rotaliammina concava, Lepidodeuterammina ochracea, Quinqueloculina seminula, Gavelinopsis praegeri, Paratrochammina haynesi, Remaneica helgolandica and Remaneicella gonzalezi. Os padrões de distribuição de algumas espécies de Trochamminidae e Remaneicidae, cuja ecologia e padrão de distribuição são pouco conhecidos, mostraram ser um marcador de ambientes mais ou menos hidrodinâmicos e de estabilidade/instabilidade do substrato em ambientes marinhos costeiros e de transição. Palavras-chave: Ecologia. Taxonomia. Imagens digitais. Análise Estatística. Ambientes Transicionais e Costeiros Marinhos.

scholarly journals Short-term fate of phytodetritus in sediments across the Arabian Sea Oxygen Minimum Zone

2008 ◽  
Vol 5 (1) ◽  
pp. 43-53 ◽  
Author(s):  
J. H. Andersson ◽  
C. Woulds ◽  
M. Schwartz ◽  
G. L. Cowie ◽  
L. A. Levin ◽  
...  
Keyword(s):  
Arabian Sea ◽  
Inorganic Carbon ◽  
Surface Sediments ◽  
Dissolved Inorganic Carbon ◽  
Oxygen Minimum Zone ◽  
Short Term ◽  
Minimum Zone ◽  
Algal Material ◽  
Oxygen Minimum

Abstract. The short-term fate of phytodetritus was investigated across the Pakistan margin of the Arabian Sea at water depths ranging from 140 to 1850 m, encompassing the oxygen minimum zone (~100–1100 m). Phytodetritus sedimentation events were simulated by adding ~44 mmol 13C-labelled algal material per m2 to surface sediments in retrieved cores. Cores were incubated in the dark, at in situ temperature and oxygen concentrations. Overlying waters were sampled periodically, and cores were recovered and sampled (for organisms and sediments) after durations of two and five days. The labelled carbon was subsequently traced into bacterial lipids, foraminiferan and macrofaunal biomass, and dissolved organic and inorganic pools. The majority of the label (20 to 100%) was in most cases left unprocessed in the sediment at the surface. The largest pool of processed carbon was found to be respiration (0 to 25% of added carbon), recovered as dissolved inorganic carbon. Both temperature and oxygen were found to influence the rate of respiration. Macrofaunal influence was most pronounced at the lower part of the oxygen minimum zone where it contributed 11% to the processing of phytodetritus.

scholarly journals Sedimentary phosphorus and iron cycling in and below the oxygen minimum zone of the northern Arabian Sea

2012 ◽  
Vol 9 (7) ◽  
pp. 2603-2624 ◽  
Author(s):  
P. Kraal ◽  
C. P. Slomp ◽  
D. C. Reed ◽  
G.-J. Reichart ◽  
S. W. Poulton
Keyword(s):  
Arabian Sea ◽  
Bottom Water ◽  
Surface Sediments ◽  
Lower Boundary ◽  
Oxygen Minimum Zone ◽  
Apatite Formation ◽  
Northern Arabian Sea ◽  
Minimum Zone ◽  
Oxygen Minimum ◽  
Burial Efficiency

Abstract. In this study, we investigate phosphorus (P) and iron (Fe) cycling in sediments along a depth transect from within to well below the oxygen minimum zone (OMZ) in the northern Arabian Sea (Murray Ridge). Pore-water and solid-phase analyses show that authigenic formation of calcium phosphate minerals (Ca-P) is largely restricted to where the OMZ intersects the seafloor topography, likely due to higher depositional fluxes of reactive P. Nonetheless, increased ratios of organic carbon to organic P (Corg/Porg) and to total reactive P (Corg/Preactive) in surface sediments indicate that the overall burial efficiency of P relative to Corg decreases under the low bottom water oxygen concentrations (BWO) in the OMZ. The relatively constant Fe/Al ratio in surface sediments along the depth transect suggest that corresponding changes in Fe burial are limited. Sedimentary pyrite contents are low throughout the ~25 cm sediment cores at most stations, as commonly observed in the Arabian Sea OMZ. However, pyrite is an important sink for reactive Fe at one station in the OMZ. A reactive transport model (RTM) was applied to quantitatively investigate P and Fe diagenesis at an intermediate station at the lower boundary of the OMZ (bottom water O2: ~14 μmol L−1). The RTM results contrast with earlier findings in showing that Fe redox cycling can control authigenic apatite formation and P burial in Arabian Sea sediment. In addition, results suggest that a large fraction of the sedimentary Ca-P is not authigenic, but is instead deposited from the water column and buried. Dust is likely a major source of this Ca-P. Inclusion of the unreactive Ca-P pool in the Corg/P ratio leads to an overestimation of the burial efficiency of reactive P relative to Corg along the depth transect. Moreover, the unreactive Ca-P accounts for ~85% of total Ca-P burial. In general, our results reveal large differences in P and Fe chemistry between stations in the OMZ, indicating dynamic sedimentary conditions under these oxygen-depleted waters.

scholarly journals Benthic archaea as potential sources of tetraether membrane lipids in sediments across an oxygen minimum zone

2018 ◽  
Vol 15 (13) ◽  
pp. 4047-4064 ◽  
Author(s):  
Marc A. Besseling ◽  
Ellen C. Hopmans ◽  
R. Christine Boschman ◽  
Jaap S. Sinninghe Damsté ◽  
Laura Villanueva
Keyword(s):  
16S Rrna ◽  
Relative Abundance ◽  
Surface Sediments ◽  
Membrane Lipids ◽  
Oxygen Minimum Zone ◽  
Rrna Gene ◽  
Polar Head Group ◽  
Group I ◽  
Minimum Zone ◽  
Oxygen Minimum

Abstract. Benthic archaea comprise a significant part of the total prokaryotic biomass in marine sediments. Recent genomic surveys suggest they are largely involved in anaerobic processing of organic matter, but the distribution and abundance of these archaeal groups are still largely unknown. Archaeal membrane lipids composed of isoprenoid diethers or tetraethers (glycerol dibiphytanyl glycerol tetraether, GDGT) are often used as archaeal biomarkers. Here, we compare the archaeal diversity and intact polar lipid (IPL) composition in both surface (0–0.5 cm) and subsurface (10–12 cm) sediments recovered within, just below, and well below the oxygen minimum zone (OMZ) of the Arabian Sea. Archaeal 16S rRNA gene amplicon sequencing revealed a predominance of Thaumarchaeota (Marine Group I, MG-I) in oxygenated sediments. Quantification of archaeal 16S rRNA and ammonia monoxygenase (amoA) of Thaumarchaeota genes and their transcripts indicated the presence of an active in situ benthic population, which coincided with a high relative abundance of hexose phosphohexose crenarchaeol, a specific biomarker for living Thaumarchaeota. On the other hand, anoxic surface sediments within the OMZ and all subsurface sediments were dominated by archaea belonging to the Miscellaneous Crenarchaeota Group (MCG), the Thermoplasmatales and archaea of the DPANN (superphylum grouping Micrarchaeota, Diapherotrites, Aenigmarchaeota, Nanohaloarchaeota, Parvarchaeota, Nanoarchaeota, Pacearchaeota and Woesearchaeota). Members of the MCG were diverse, with a dominance of subgroup MCG-12 in anoxic surface sediments. This coincided with a high relative abundance of IPL GDGT-0 with an unknown polar head group. Subsurface anoxic sediments were characterized by higher relative abundance of GDGT-0, -2 and -3 with dihexose IPL types, GDGT-0 with a cyclopentanetetraol molecule and hexose, as well as the presence of specific MCG subgroups, suggesting that these groups could be the biological sources of these archaeal lipids.

Sign in / Sign up

Export Citation Format

Share Document