Spatial and seasonal variations of subtidal free-living nematode assemblages in the northern Beibu Gulf, South China Sea

2011 ◽  
Vol 92 (2) ◽  
pp. 255-264 ◽  
Author(s):  
S.J. Fu ◽  
L.Z. Cai ◽  
J. Yang ◽  
X.P. Zhou ◽  
X. Peng ◽  
...  
Keyword(s):  
Organic Matter ◽  
South China Sea ◽  
Water Depth ◽  
Environmental Variables ◽  
Beibu Gulf ◽  
Free Living ◽  
Deposit Feeders ◽  
Free Living Nematode ◽  
Offshore Station ◽  
The Mean

This study determined the spatial and seasonal density, number of genera, genera composition, maturity index and trophic structure of free-living nematode assemblages in the subtidal waters of the northern Beibu Gulf, South China Sea, and explored whether these five biotic characteristics were related to various environmental variables. Based on the data derived from samples collected seasonally at nine stations, the mean densities of nematodes decreased from alongshore to offshore station in the northern Beibu Gulf. However, the number of nematode genera increased from alongshore to offshore station. Non-parametric multidimensional scaling analysis showed no clear seasonal changes for nematode assemblages in most sampling stations. Higher densities of the generaElzaliaandTricomawere found in offshore sampling stations, and a higher density of the genusCheironchuswas found in alongshore sampling stations. The mean percentage of each feeding type compared to the total numbers was highest in epigrowth feeders (2A), second highest in non-selective deposit feeders (1B), third highest in predators (2B), and lowest in selective deposit feeders (1A). There were significant negative correlations between nematode density and water depth and temperature; significant positive correlations between the number of nematode genera and water depth and salinity; and significant negative correlation between the maturity index of the nematode assemblage and organic matter. BIOENV analysis indicated that water depth, salinity, pH, median sediment particle size and organic matter were the most correlated combination of environmental variables affecting the nematode assemblages.

Characteristics of tide-water calving at Glaciar San Rafael, Chile

1995 ◽  
Vol 41 (138) ◽  
pp. 273-289 ◽  
Author(s):  
Charles R. Warren ◽  
Neil F. Glasser ◽  
Stephan Harrison ◽  
Vanessa Winchester ◽  
Andrew R. Kerr ◽  
...  
Keyword(s):  
Water Depth ◽  
Environmental Variables ◽  
Empirical Relationship ◽  
Glacier Surface ◽  
Frequency Distributions ◽  
Low Salinity ◽  
The Mean ◽  
Oceanographic Data ◽  
San Rafael ◽  
Tidal Stage

AbstractGlacial calving is a poorly understood process. This study tests the influence of local environmental variables on the magnitude and frequency distributions of calving behaviour at Glaciar San Rafael, Chile. Near the terminus of the glacier, surface speeds average 17 m d −1 in summer and calving is profuse and continual. The size, location and characteristics of over 7000 calving events were recorded during 32d in 1991 and 1992, together with meteorological, bathymetric and oceanographic data. Mean daily calving exceeds 400 events per day and the mean calving flux is more than 2 Mm3d1. Mean annual calving speed and calving flux are about 4500 m a −1 and 2.0 km3 a−1, respectively. This calving speed is higher than that predicted by the established empirical relationship between tide-water calving speed and water depth. This is surprising, given the low salinity of Laguna San Rafael and that fresh-water calving speeds are commonly much lower than those in ride water. Daily patterns of calving frequency and flux correlate poorly or not at all with meteorological variables, but tidal stage may have some control over the timing of large submarine calving events. Submarine calving produced the largest bergs. However, the relatively small total flux recorded from the submerged pars of the ice cliff may imply unusually rapid melt rates.

scholarly journals Circulation and oxygenation of the glacial South China Sea

2016 ◽  
Author(s):  
Shuh-Ji Kao ◽  
Tzu-Ling Chiang ◽  
Da-Wei Li ◽  
Yi-Chia Hsin ◽  
Li-Wei Zheng ◽  
...  
Keyword(s):  
Organic Matter ◽  
South China Sea ◽  
Residence Time ◽  
Primary Productivity ◽  
Circulation Pattern ◽  
Water Residence Time ◽  
Reducing Environment ◽  
The Mean ◽  
Monsoon Wind ◽  
Wind Intensity

Abstract. Degree of oxygenation in intermediate water modulates the downward transferring efficiency of primary productivity (PP) from surface water to deep water for carbon sequestration, consequently, the storage of nutrients versus the delivery and sedimentary burial fluxes of organic matter and associated biomarkers. To better decipher the PP history of the South China Sea (SCS), appreciation about the glacial-interglacial variation of the Luzon Strait (LS) throughflow, which determines the mean residence time and oxygenation of water mass in the SCS interior, is required. Based on a well-established physical model, we conducted a 3-D modeling exercise to quantify the effects of sea level drop and monsoon wind intensity on glacial circulation pattern, thus, to evaluate effects of productivity and circulation-induced oxygenation on the burial of organic matter. Under modern climatology wind conditions, a 135 m sea level drop results in a greater basin closeness and a ~ 23 % of reduction in the LS intermediate westward throughflow, consequently, an increase in the mean water residence time (from 19 to 23 year). However, when the wind intensity was doubled during glacial low, the throughflow restored largely to reach a similar residence time (18.4 years) as today regardless its closeness. Comparing with present day SCS, surface circulation pattern in glacial model exhibits (1) stronger upwellings at the west off Luzon Island and the east off Vietnam, and (2) an intensified southwestward jet current along the western boundary of the SCS basin. Superimposed hypothetically by stronger monsoon wind, the glacial SCS conditions facilitate greater primary productivity. Manganese, a redox sensitive indicator, in IMAGES core MD972142 at southeastern SCS revealed a relatively reducing environment in glacial periods. Considering the similarity in the mean water residence time between modern and glacial cases, the reducing environment of the glacial southeastern SCS was thus ascribed to a productivity-induced rather than ventilation-induced consequence.

Characteristics of tide-water calving at Glaciar San Rafael, Chile

1995 ◽  
Vol 41 (138) ◽  
pp. 273-289 ◽  
Author(s):  
Charles R. Warren ◽  
Neil F. Glasser ◽  
Stephan Harrison ◽  
Vanessa Winchester ◽  
Andrew R. Kerr ◽  
...  
Keyword(s):  
Water Depth ◽  
Environmental Variables ◽  
Empirical Relationship ◽  
Glacier Surface ◽  
Frequency Distributions ◽  
Low Salinity ◽  
The Mean ◽  
Oceanographic Data ◽  
San Rafael ◽  
Tidal Stage

AbstractGlacial calving is a poorly understood process. This study tests the influence of local environmental variables on the magnitude and frequency distributions of calving behaviour at Glaciar San Rafael, Chile. Near the terminus of the glacier, surface speeds average 17 m d−1in summer and calving is profuse and continual. The size, location and characteristics of over 7000 calving events were recorded during 32d in 1991 and 1992, together with meteorological, bathymetric and oceanographic data. Mean daily calving exceeds 400 events per day and the mean calving flux is more than 2 Mm3d1. Mean annual calving speed and calving flux are about 4500 m a−1and 2.0 km3a−1, respectively. This calving speed is higher than that predicted by the established empirical relationship between tide-water calving speed and water depth. This is surprising, given the low salinity of Laguna San Rafael and that fresh-water calving speeds are commonly much lower than those in ride water. Daily patterns of calving frequency and flux correlate poorly or not at all with meteorological variables, but tidal stage may have some control over the timing of large submarine calving events. Submarine calving produced the largest bergs. However, the relatively small total flux recorded from the submerged pars of the ice cliff may imply unusually rapid melt rates.

scholarly journals Two new free-living nematode species (Trefusiina: Trefusiidae) from the Chatham Rise crest, Southwest Pacific Ocean

2013 ◽  
Author(s):  
Daniel Leduc
Keyword(s):  
New Species ◽  
Pacific Ocean ◽  
Water Depth ◽  
Nematode Species ◽  
Valid Species ◽  
Free Living ◽  
Southwest Pacific ◽  
The Family ◽  
Two New Species ◽  
Free Living Nematode

Two new species of the family Trefusiidae, viz., Trefusia piperata sp. nov. and Trefusialaimus idrisi sp. nov., are described from the crest of the Chatham Rise, Southwest Pacific Ocean (350 m water depth). The present study provides the first species records for this family in the region. Trefusia and Trefusialaimus comprise twenty and three valid species, respectively. A key to males of Trefusia is provided.

The effect of gonadotropins on the in vitro growth of the free-living nematode Cephalobus sp. Bastian

1971 ◽  
Vol 49 (7) ◽  
pp. 1059-1061 ◽  
Author(s):  
Cyril H. S. Thong ◽  
John M. Webster
Keyword(s):  
In Vitro Growth ◽  
Environmental Condition ◽  
Stress Reactions ◽  
Free Living ◽  
Rate Of Development ◽  
Free Living Nematode ◽  
The Mean ◽  
Gravid Females ◽  
As Stress

Cephalobus sp. was exposed to four concentrations of testosterone and oestradiol in an in vitro culture. The rate of development was not affected. There was a significant increase in the mean body lengths of gravid females and mature males at concentrations of oestradiol between 0.001 and 0.05 mg and at concentrations of testosterone between 0.01 and 0.05 mg. These changes are interpreted as stress reactions of the nematodes to an unnatural environmental condition.

scholarly journals Characteristics of Organic Matter and Biomarkers in Core Sediments From the Offshore Area of Leizhou Peninsula, South China Sea

2021 ◽  
Vol 9 ◽  
Author(s):  
Yuan Gao ◽  
Jingqian Tan ◽  
Jia Xia ◽  
Yao-Ping Wang ◽  
Sibo Wang ◽  
...  
Keyword(s):  
Organic Matter ◽  
South China Sea ◽  
South China ◽  
Sediment Cores ◽  
Petroleum Exploration ◽  
Beibu Gulf ◽  
Rock Outcrops ◽  
Offshore Area ◽  
Leizhou Peninsula ◽  
China Sea

Total organic carbon (TOC), total nitrogen (TN) and multi-biomarker indexes were analyzed for two sediment cores from the eastern coastal area of the Beibu Gulf (core 45, AMS 14C dated) and Qiongzhou Strait (core 29), South China Sea. The results showed that the TOC and TN content of the samples studied were 0.32–0.62% and 0.02–0.07%, respectively. The hydrocarbons in offshore sediments of Leizhou Peninsula were consisted of biogenic hydrocarbons and petrogenic hydrocarbons. The Core 29 sediments contain more terrigenous organic matter than that of sediments in core 45 due to the difference in hydrodynamic conditions. The composition and distribution of various lipid biomarkers indicate the presence of petrogenic hydrocarbons in the sediments of the whole profile of two sediment cores. There are multiple natural sources of hydrocarbons that could potentially contribute to the petroleum background through oil seeps and erosion of carbon-rich rock outcrops or bitumen deposits. Deep sourced hydrocarbon inputs from the submarine hydrocarbon seepage cannot be excluded. Further study is needed to resolve the specific sources for the petrogenic hydrocarbons and may be significant to petroleum exploration in the study area.

scholarly journals Effect of sand-dune slope orientation on soil free-living nematode abundance and diversity

2010 ◽  
Vol 47 (3) ◽  
pp. 179-188 ◽  
Author(s):  
S. Pen-Mouratov ◽  
C. Hu ◽  
E. Hindin ◽  
Y. Steinberger
Keyword(s):  
Organic Matter ◽  
Soil Moisture ◽  
Sand Dune ◽  
Temporal Dynamics ◽  
Nematode Species ◽  
Sampling Location ◽  
Free Living ◽  
Free Living Nematode ◽  
The Impact ◽  
Slope Orientation

AbstractThe spatial and temporal dynamics and composition of a soil free-living nematode community were studied in order to determine the impact of slope orientation on the community on the xeric south- and the mesic north-facing sand-dune slopes.A significant effect of sampling location on organic matter, total number of free-living nematodes, and trophic diversity was found. Although soil moisture had a significant effect on separate nematode trophic groups and on most of the applied ecological indices, no differences in soil moisture were observed between slopes. Organic matter was found to have a significant effect on the fungivore nematodes. The obtained results indicate that the south-facing slope is more favorable for the observed free-living nematodes than the other sampling sites. Twenty-four of the 77 nematode species that were found in the observed area showed dependence on dune slope orientation. The fungibacteria ratio, Simpson’s dominance index, and basal index were useful tools for determining slope differences.

The prediction of voluntary intake of grazing dairy cows

1986 ◽  
Vol 107 (1) ◽  
pp. 43-54 ◽  
Author(s):  
Lindsey Caird ◽  
W. Holmes
Keyword(s):  
Organic Matter ◽  
Measurement Techniques ◽  
Live Weight ◽  
Simple Equation ◽  
Factors Affecting ◽  
Farm Planning ◽  
Sward Height ◽  
The Mean ◽  
Major Factors ◽  
Grazing Dairy Cows

SUMMARYInformation on the total organic matter intake, concentrates supplied (C), live weight (LW), week of lactation (WL), milk yield (MY), herbage organic matter digestibility (HOMD), herbage mass, sward height (SHT) or herbage allowance (HAL) measured individually for 357 cows at one of three sites was assembled. Observed intake was compared with intakes predicted by existing intake equations and new prediction equations based on regression models or regression and least-squares constants were developed. Major factors affecting intake were MY, LW, WL, C and HAL or SHT. Although HOMD was correlated with intake, better predictions were obtained when HOMD was omitted. There were differences between sites possibly associated with differences in measurement techniques.The predictive value of some existing equations and new equations were tested against independent sets of data. A simple equation (A) based on MY and LW (Ministry of Agriculture, Fisheries and Food, 1975) gave satisfactory average predictions but the mean square prediction error (MSPE) was high. The equations of Vadiveloo & Holmes (1979) adjusted for bias gave a relatively low MSPE. The preferred new equations for grazing cattle included MY, LW, WL, C and HAL or SHT, and their MSPE were similar to or lower than for indoor equations.The discussion indicates that a simple equation (A) would give adequate predictions for farm planning. The more detailed equations illustrate the inter-relations of animal with sward conditions and concentrate allowances. Predicted intakes may deviate from actual intakes because of short-term changes in body reserves.

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