Spatial variation of meiofaunal tardigrades in a small tropical estuary (~6°S; Brazil)

2019 ◽  
Vol 70 (8) ◽  
pp. 1094 ◽  
Author(s):  
Sebastião Tilbert ◽  
Francisco J. V. de Castro ◽  
Géssica Tavares ◽  
Miodeli Nogueira Júnior
Keyword(s):  
Redundancy Analysis ◽  
Dry Season ◽  
Spatial Variations ◽  
Total Abundance ◽  
Soft Bottom ◽  
Medium Sand ◽  
Tropical Estuaries ◽  
Explanatory Variables ◽  
Abundant Taxon ◽  
Meiofaunal Abundance

Spatial variations and organism–sediment relationship are paramount subjects of soft-bottom ecology. However, these issues have been unexplored for most minor meiofaunal taxa such as tardigrades. In the present study, we explore this subject on a small tropical (~6°S) estuary. Total meiofaunal abundance ranged from 4 to 1036 individuals per 10cm2, averaging (mean±s.d.) 324.8±245.9 individuals per 10cm2. Nematodes dominated in both seasons, representing >70% of total abundance. Tardigrades were the second-most abundant taxon, representing 15% of the total and up to 71%. Tardigrades were represented by two species, Batillipes dandarae and B. pennaki, the latter dominating in the rainy season, and both with similar abundances in the dry season. Abundance of total meiofauna and both tardigrade species differed significantly (ANOVA; P<0.05) among stations and in the interaction between stations and seasons, but only B. dandarae varied seasonally, with higher values occurring in the dry season. The spatial variations observed were mostly related to differences in the sediment granulometry. Environmental explanatory variables explained 72.6% of the variance of dominant meiofaunal taxa in the Redundancy Analysis. Nematodes and ostracods were mostly associated with fine and very fine sands, both tardigrades with medium sand and oligochaetes with larger size-fractions of the sediment and organic matter. The data gathered here suggest that granulometry was the most important environmental factor in the meiofaunal spatial structure in tropical estuaries and both tardigrade species were closely associated with medium sand.

Landscape Influences on Stream Habitats and Biological Assemblages

2006 ◽  
Keyword(s):  
Landscape Scale ◽  
Riparian Zones ◽  
Total Abundance ◽  
Stream Channels ◽  
Urban Centers ◽  
Explanatory Variables ◽  
Agricultural Areas ◽  
Abundance And Distribution ◽  
Shallow Stream ◽  
Agricultural Regions

<em>Abstract.</em>—Wood is an important component of small to medium-sized streams in forested regions, but has been poorly studied in agricultural areas. Our goals were to (1) characterize the abundance, size, and distribution of wood in low-gradient streams in two agricultural regions, (2) quantify the influence of reach- and landscape-scale factors on the abundance and distribution of wood in these streams, and (3) compare trends across two study areas. Wood abundance was quantified in stream reaches in two diverse agricultural regions of the Midwestern United States: central Michigan and southeastern Minnesota. Wood abundance was quantified in 71 stream reaches, and an array of channel, riparian zone, and landscape features were characterized. Multiple regressions were conducted to predict abundance from those explanatory variables. We found that large wood was relatively scarce in these low-gradient streams compared to low-gradient streams in forested regions. Mean log size was greater, but total abundance was lower in Minnesota than Michigan. In Minnesota, greatest wood abundance and greatest extent of accumulations were predicted in wide, shallow stream channels with high substrate heterogeneity and woody riparian vegetation overhanging the channel. Models were dominated by reach-scale variables. In Michigan, largest densities of wood and accumulations were associated with catchments in hilly regions containing urban centers, with low soil water capacity, wide, shallow stream channels, low coarse particular organic matter standing stocks, and woody riparian zones. Models contained both reach- and landscape-scale variables. Difference in the extent of agricultural and forest land use/cover between Michigan and Minnesota may explain the differences in the models predicting wood variables. Patterns in wood abundance and distribution in these Midwestern streams differ from those observed in high gradient regions, and in low-gradient streams within forested regions. This has important implications for ecosystem processes and management of headwater streams in agricultural regions.

scholarly journals Spatial Variations in Groundwater Quality Around Dumpsite in Igando

2015 ◽  
Vol 6 (1) ◽  
pp. 179-186
Author(s):  
Akoteyon ◽  
S Isaiah
Keyword(s):  
Heavy Metals ◽  
Water Quality ◽  
Drinking Water ◽  
Groundwater Quality ◽  
Anthropogenic Activities ◽  
Dry Season ◽  
Spatial Variations ◽  
T Test ◽  
Drinking Water Quality ◽  
Wet Season

Water samples collected from fifteen hand dug wells in November (dry season), 2011 and July (Wet season), 2012 using random sampling technique. In situ parameters were measured for pH, electrical conductivity, total dissolved solids using portable meters. Heavy metals were analyzed for; Fe, Cu, Zn, Cd, Pb, and Cr using Atomic Absorption Spectrophotometer (AAS). The study aimed at examining the spatial variations in groundwater quality around dumpsite in Igando using paired sample T-test statistical technique. The result shows that the measured pH values were below the minimum WHO standard for drinking water quality in wet and dry seasons in about73.3% and 26.7% respectively. Also, approximately, 13.3% of EC, and 6.7% exceeded the prescribed standard limit of WHO in dry and wet seasons respectively. Concentration of Fe exceeded drinking water quality in all the sampling locations during wet season and only about 46.7% in dry season. Pb, Zn, and Cu exceeded WHO limit in about 86.7%, 80%, and 26.7% respectively in dry season. Concentration of Pb, Cd , Cu and Cr were under detection limit in all the locations except at locations G2 for Cu in wet season. The paired samples statistics and correlation revealed that the mean values of all the parameters were higher in dry season with the exception of Fe. No significant correlations exist among the paramet er for both seasons at p<0.05. The paired T-test show significant seasonal variations among four heavy metals including Fe, Cd, Pb and Zn.The study concluded that, samples in dry season are of low quality compared to wet. The study recommends public enlightenment on solid waste disposal, controlled anthropogenic activities, and treatment /recycling of waste to prevent heavy metal from leaching unto the sub-surface.DOI: http://dx.doi.org/10.3329/jesnr.v6i1.22063 J. Environ. Sci. & Natural Resources, 6(1): 179-186 2013

scholarly journals Nitrous oxide and methane in two tropical estuaries in a peat-dominated region of northwestern Borneo

2016 ◽  
Vol 13 (8) ◽  
pp. 2415-2428 ◽  
Author(s):  
Denise Müller ◽  
Hermann W. Bange ◽  
Thorsten Warneke ◽  
Tim Rixen ◽  
Moritz Müller ◽  
...  
Keyword(s):  
Nitrous Oxide ◽  
Inorganic Nitrogen ◽  
Monsoon Season ◽  
Peat Soil ◽  
Dry Season ◽  
N2o Emissions ◽  
Wet Season ◽  
Tropical Estuaries ◽  
Ch4 Emissions ◽  
Nitrogen Concentrations

Abstract. Estuaries are sources of nitrous oxide (N2O) and methane (CH4) to the atmosphere. However, our present knowledge of N2O and CH4 emissions from estuaries in the tropics is very limited because data are scarce. In this study, we present first measurements of dissolved N2O and CH4 from two estuaries in a peat-dominated region of northwestern Borneo. Two campaigns (during the dry season in June 2013 and during the wet season in March 2014) were conducted in the estuaries of the Lupar and Saribas rivers. Median N2O concentrations ranged between 7.2 and 12.3 nmol L−1 and were higher in the marine end-member (13.0 ± 7.0 nmol L−1). CH4 concentrations were low in the coastal ocean (3.6 ± 0.2 nmol L−1) and higher in the estuaries (medians between 10.6 and 64.0 nmol L−1). The respiration of abundant organic matter and presumably anthropogenic input caused slight eutrophication, which did not lead to hypoxia or enhanced N2O concentrations, however. Generally, N2O concentrations were not related to dissolved inorganic nitrogen concentrations. Thus, the use of an emission factor for the calculation of N2O emissions from the inorganic nitrogen load leads to an overestimation of the flux from the Lupar and Saribas estuaries. N2O was negatively correlated with salinity during the dry season, which suggests a riverine source. In contrast, N2O concentrations during the wet season were not correlated with salinity but locally enhanced within the estuaries, implying that there were additional estuarine sources during the wet (i.e., monsoon) season. Estuarine CH4 distributions were not driven by freshwater input but rather by tidal variations. Both N2O and CH4 concentrations were more variable during the wet season. We infer that the wet season dominates the variability of the N2O and CH4 concentrations and subsequent emissions from tropical estuaries. Thus, we speculate that any changes in the Southeast Asian monsoon system will lead to changes in the N2O and CH4 emissions from these systems. We also suggest that the ongoing cultivation of peat soil in Borneo is likely to increase N2O emissions from these estuaries, while the effect on CH4 remains uncertain.

Polychaetes of the shallow sublittoral of Admiralty Bay, King George Island, South Shetland Islands

1993 ◽  
Vol 5 (2) ◽  
pp. 161-167 ◽  
Author(s):  
Jacek Sicinski ◽  
Ewa Janowska
Keyword(s):  
South Shetland Islands ◽  
Published Data ◽  
Total Biomass ◽  
Depth Range ◽  
Total Abundance ◽  
Soft Bottom ◽  
Shetland Islands ◽  
Capitella Capitata ◽  
The Antarctic ◽  
Main Factor

Twenty five species of Polychaeta were recorded in soft bottom samples collected from 4–30 m. Total abundance of polychaetes ranged from 60 to 3300 m-2. High abundance values were locally recorded for Microspio moorei, Tharyx epitoca and Ophelina syringopyge. These species, together with more regularly distributed Capitella capitata and Scoloplos marginatus, constituted over 70% of all specimens. Total biomass value of the polychaetes varied between 3.8 and 46.4 gm-2. Travisia kerguelenensis and Aglaophamus ornatus constituted over 75% of total biomass. Species composition, richness and diversity of the polychaete assemblage varied with depth. Two parts of the investigated bottom section, differing in the polychaete assemblages structure, were distinguished; the first one in the depth range from 4–20 m and the second one at the depths of 25–30 m. On the basis of both new and previously published data two types of polychaete assemblages of the shallow soft bottom of the Antarctic sublittoral were distinguished. The type of sediment seems to be the main factor influencing the composition of polychaete assemblages.

scholarly journals Temporal and Spatial Variation Trends in Water Quality Based on the WPI Index in the Shallow Lake of an Arid Area: A Case Study of Lake Ulansuhai, China

Water ◽  
2019 ◽  
Vol 11 (7) ◽  
pp. 1410 ◽  
Author(s):  
Qi Zhang ◽  
Ruihong Yu ◽  
Ye Jin ◽  
Zhuangzhuang Zhang ◽  
Xinyu Liu ◽  
...  
Keyword(s):  
Water Pollution ◽  
Water Quality ◽  
Cluster Analysis ◽  
Shallow Lake ◽  
Yellow River ◽  
Dry Season ◽  
Spatial Variations ◽  
Wet Season ◽  
Pollution Indicators ◽  
Pollution Indicator

Ulansuhai, the largest shallow lake of the Yellow River of China, is an important component of the Hetao region irrigation system. Many concerns have concentrated on its water quality, which affects the local water security and sustainable economic development. In this study, the water pollution index (WPI), an effective water quality evaluation method, was used to compare the pollution levels among pollution indicators and to determine the major pollution indicators. The regime shift index (RSI) approach was employed to identify the water quality trends. Cluster analysis and Daniel trend test methods were employed to analyse the inner-annual and inter-annual spatio-temporal trends of the typical water quality indicators (e.g., total nitrogen (TN), total phosphorus (TP), dissolved oxygen (DO), and chemical oxygen demand (COD)) in Lake Ulansuhai. The results show that the water quality of Ulansuhai improved from 1998 to 2017; spatial variations in the WPITN, WPITP, and WPIDO followed the order of inlet > centre and outlet, while spatial variations in the WPICOD showed the order of outlet > inlet > centre. TN was the critical pollution indicator throughout the year. In 2017, the dry season and wet season were determined using cluster analysis. The WPICOD was higher than the WPITN, WPITP, and WPIDO in the dry season, while the WPITN, WPITP, and WPIDO were higher than the WPICOD in the wet season. WPI was grouped into three clusters: highly polluted regions, moderately polluted regions, and less polluted regions, However, there is a discrepancy between the three polluted regions that were divided into the dry season and the wet season. The WPICOD was highest among all pollution indicators in 2017. Major sources of pollution that contribute to the deterioration of water quality include inner-annual or inter-annual pollution, agricultural non-point pollution, point source pollution, and internal pollution. This study provides useful information for authorities to effectively manage water quality and control water pollution.

scholarly journals Alkalinity, inorganic carbon and CO2 flux variability during extreme rainfall years (2010-2011) in two polluted tropical estuaries NE Brazil

2018 ◽  
Vol 66 (1) ◽  
pp. 115-130 ◽  
Author(s):  
Felipe Lima Gaspar ◽  
Barbara Ramos Pinheiro ◽  
Carlos Esteban Delgado Noriega ◽  
Moacyr Araujo ◽  
Nathalie Lefèvre ◽  
...  
Keyword(s):  
Dissolved Oxygen ◽  
Rainy Season ◽  
Inorganic Carbon ◽  
Co2 Flux ◽  
Extreme Rainfall ◽  
Dry Season ◽  
Rainfall Event ◽  
Total Alkalinity ◽  
Extreme Rainfall Event ◽  
Tropical Estuaries

Abstract The susceptibility of coastal environments to shifts in the biogeochemical cycles of carbon and nutrients driven by anthropogenic pressure and climate change is a real challenge for the scientific community. This paper evaluated the effects of an extreme rainfall event over the nutrients and carbonate parameters in two polluted tropical estuaries. Surface water samples were taken seasonally along a salinity gradient in the Capibaribe and Barra de Jangadas estuaries in order to investigate the spatial and seasonal variability of dissolved nutrients, chlorophyll-a, dissolved oxygen, total alkalinity, inorganic carbon, partial pressure of CO2 (pCO2) and CO2 fluxes. The increased riverine influence caused by the fluvial flooding during the extremely rainy season augmented the nitrogen concentrations in the plumes, which also presented reduced salinity, alkalinity and dissolved oxygen values. In the Capibaribe plume it has also shifted the mean CO2 flux value of - 4.01 mmolC m-2 d-1 during the dry season, to a positive mean flux of + 5.7 mmolC m-2 d-1 during the rainy season. Within the estuaries the BOD5,20 and dissolved phosphorus values were higher during the dry season (p<0.0001), they showed positive correlation with the phytoplanktonic blooms that reached a chl-a value of 85 mg m-3 in the Capibaribe. The high alkalinity found in both estuaries, with mean values between dry and wet seasons respectively from 1808 to 1373 µmol kg-1 in the Capibaribe estuary and 1616 to 1058 µmol kg-1 in Barra de Jangadas estuary, may act as a buffer to the process of coastal acidification due to eutrophication. The increased rivers discharge lead to a greater transport of organic matter and nutrients to the coast, decreasing the oxygen availability and shifting the metabolic status of the estuarine plume to heterotrophic, whereas increased the water quality within the estuaries due the flushing promoted by the extreme rainfall event.

Multiblock modelling to assess the overall risk factors for a composite outcome

2011 ◽  
Vol 140 (2) ◽  
pp. 337-347 ◽  
Author(s):  
S. BOUGEARD ◽  
C. LUPO ◽  
S. Le BOUQUIN ◽  
C. CHAUVIN ◽  
E. M. QANNARI
Keyword(s):  
Risk Factors ◽  
Redundancy Analysis ◽  
Complex Disease ◽  
Linear Models ◽  
Epidemiological Data ◽  
Health Issues ◽  
Explanatory Variables ◽  
Modelling Framework ◽  
Several Variables ◽  
Veterinary Epidemiology

SUMMARYResearch in epidemiology may be concerned with assessing risk factors for complex health issues described by several variables. Moreover, epidemiological data are usually organized in several blocks of variables, consisting of a block of variables to be explained and a large number of explanatory variables organized in meaningful blocks. Usual statistical procedures such as generalized linear models do not allow the explanation of a multivariate outcome, such as a complex disease described by several variables, with a single model. Moreover, it is not easy to take account of the organization of explanatory variables into blocks. Here we propose an innovative method in the multiblock modelling framework, called multiblock redundancy analysis, which is designed to handle most specificities of complex epidemiological data. Overall indices and graphical displays associated with different interpretation levels are proposed. The interest and relevance of multiblock redundancy analysis is illustrated using a dataset pertaining to veterinary epidemiology.

scholarly journals Abundance and stratification of soil macroarthropods in a Caatinga Forest in Northeast Brazil

2010 ◽  
Vol 70 (3 suppl) ◽  
pp. 737-746 ◽  
Author(s):  
VFP Araújo ◽  
AG Bandeira ◽  
A Vasconcellos
Keyword(s):  
Rainy Season ◽  
Dry Season ◽  
Soil Biology ◽  
Taxa Richness ◽  
Abundant Taxon ◽  
Dry Seasons ◽  
Physical Effects ◽  
Arid And Semiarid Ecosystems ◽  
Arid And Semiarid ◽  
Dry And Rainy Seasons

In arid and semiarid environments, seasonality usually exerts a strong influence on the composition and dynamics of the soil community. The soil macroarthropods were studied in a Caatinga forest located in the Reserva Particular do Patrimônio Natural (RPPN) Fazenda Almas, São José dos Cordeiros, Paraíba, Brazil. Samples were collected during the dry and rainy seasons following the method proposed by the Tropical Soil Biology and Fertility Program (TSBF), with minor modifications. At each station, 15 soil blocks (20 × 20 × 30 cm: 12 L) were extracted and divided into three layers: A (0-10 cm), B (10-20 cm), and C (20-30 cm). In the rainy and dry seasons 1,306 ± 543(se) and 458 ± 212 ind.m-2 macroarthropods were found, respectively, with 35 and 18 respective taxa recorded. The abundance of individuals and taxa were significantly higher in the rainy season. Isoptera (57.8%) was the most abundant taxon, followed by Hymenoptera: Formicidae (17.2%), Coleoptera larvae (7.3%), and Araneae (3.5%). In the rainy season, abundance in layer A (576 ± 138 ind.m-2) was significantly higher than that of layer C (117 ± 64 ind.m-2), but was not different from layer B (613 ± 480 ind.m-2). There was also no difference between the layer B and C abundances. In the dry season, abundance in layer B (232 ± 120 ind.m-2) was not significantly different compared to layer A (182 ± 129 ind.m-2), but was significantly higher than abundance in layer C (44 ± 35 ind.m-2). During the rainy season, layer A (34 taxa) was significantly richer in taxa than layers B (19 taxa) and C (11 taxa). On the other hand, during the dry season the richness of layers A (12 taxa) and B (12 taxa) was equal, but significantly higher than that of layer C (6 taxa). Richness of taxa and abundance were positively correlated with soil organic matter and negatively correlated with soil temperature. The community of soil macroarthropods in the area of Caatinga studied has taxonomic and functional structures that are relatively complex and is therefore likely to exert an influence on ecosystem productivity due to its physical effects on soil profile and necromass fragmentation, as occurs in other arid and semiarid ecosystems throughout the world.

scholarly journals Composition and diversity of benthic macroinvertebrates in a Brazilian Cerrado stream

2020 ◽  
Vol 110 ◽  
Author(s):  
Jéssica F. G. Pio ◽  
Eunice de F. E. Santiago ◽  
Carlos E. Copatti
Keyword(s):  
Species Richness ◽  
Rainy Season ◽  
Dry Season ◽  
Benthic Macroinvertebrate ◽  
Brazilian Cerrado ◽  
The Family ◽  
Family Level ◽  
Abundant Taxon ◽  
Number Of Individuals ◽  
Dry And Rainy Seasons

ABSTRACT This study aimed to analyse the diversity and composition of benthic macroinvertebrate assemblages in the dry and rainy seasons in a Brazilian Cerrado stream, where it was hypothesized that the dry season has higher diversity and it differs in terms of organism composition in relation to the rainy season. Sampling was carried out in the dry (May and August/2016 and August/2017) and rainy seasons (November/2016 and February and November/2017). Individuals were identified at the family level and classified according to functional feeding group (FFG). There were 3,776 individuals, in which Chironomidae was the most abundant taxon with 2,226 organisms. The FFG with the highest number of individuals and species richness were collector-gatherer and predator, respectively. The species richness was higher in the dry season than in the rainy season. The ordinance generated by NMDS showed that there was no distinction in the composition of the assemblage between the dry and rainy seasons. Seasonal variations do not alter the abundance and composition of the benthic macroinvertebrate assemblage, but the species richness does decrease in rainy seasons.

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