Research Repository :: Browsing by Author "Shilla, Daniel"

Browsing by Author "Shilla, Daniel"

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AquaEco 40 (2006) Decomposition of Zizania latifolia AGB and BGB
(2013-04) Sanderson, Brian; Shilla, Daniel; Fujino, Takeshi; Asaeda, Takashi
Decomposition of aboveground and belowground organs of the emergent macrophyte Z.latifolia wasinvestigated using a litterbag technique for a period of 359 days in a freshwater marsh in Japan. Above-ground parts were classified into: leaves, sheaths and stems. Belowground parts were classified into: hor-izontal rhizomes (new rhizome, hard rhizome, soft rhizome) and vertical rhizome (stembase). The decayrate (k) was 0.0036 day)1, 0.0033 day)1and 0.0021 day)1for leaves, sheaths and stems, respectively. Forbelowground parts, the decay rate varied considerably from 0.0018 day)1to 0.0079 day)1, according todifferences in the initial chemical compositions of rhizomes. After 359 days of decay, new rhizomes lost94% of their original dry mass, compared with a loss of 48 –84% for the other rhizomes. There was asignificant positive relationshi p between litter quality and decay rate for horizontal rhizomes. For the newrhizomes, which had an internal nitrogen content of 24.2 mg N g)1dry mass, the mass loss was 40% higherthan that of soft rhizomes, which had an internal N content of 9.8 mg N g)1dry mass. Over the period of359 days, the nitrogen concentration in all rhizome types decreased to levels lower than initial values, butthe phosphorus concentration remained constant after an initial leaching loss. Most nitrogen and phos-phorus were lost during the first 45 days of decay. Changes in carbon to nitrogen (C:N) and carbon tophosphorus (C:P) ratios basically followed inversed trends of the nitrogen and phosphorus concentrations.
Chemical and Isotopic Composition of Estuarine Organic Matter: Implications for the Relative Contribution and Reactivity of Anthropogenic Sources of Organic Matter
(Taylor and Francis, 2014) Shilla, Daniel
Abstract The source and composition of suspended particulate organic matter in the Manko estuary, Okinawa Island, Japan, has been evaluated using fatty acid biomarkers and stable carbon and nitrogen isotopes. Fatty acid signature and stable isotope data have revealed that terrestrial organic matter (including terrestrial vascular plants), bacteria, phytoplankton produced within the estuary and coastal sea, green macroalgae and mixed planktonic-sources predominantly contributed to the organic matter pool in the estuary. The combined approach has also allowed for the prediction of the following mixing regime and distribution of organic matter sources along the estuarine salinity gradient; Allochthonous, both terrestrial and river-borne organic matter which dominate the riverine section of the estuary seem to be slightly diluted with autochthonous organic matter in the middle estuary (site M) and thereafter, in the lower reaches of the estuary (Site SW2) are measurably admixed with tidally introduced marine organic matter. However, the autochthonous primary production within the estuary seems to be highly dependent on the discharges of terrestrial organic matter and nutrients as depicted in fatty acid signatures and isotopic composition of residential and agricultural wastewater runoff. Isotopic composition of dissolved constituents (particularly, ammonia and nitrate) highly influences the composition of autochthonous primary producers. The linkage between suspended organic matter sources and the diet of tilapia (Oreochromis mossambicus [Peters]) is also discussed.
Decomposition Rate of Submerged Plants
(Springer Link, 2013-04) Shilla, Daniel; Asaeda, Takashi; Fujino, Takeshi; Sanderson, Brian
Breakdown and nutrient dynamics of submerged macrophytes were studied in Myall Lake, Australia. Mass loss of Myriophyllum sulsagineum was the lowest (64.90%) among the studied macrophytes during the 322 days followed by charophytes (60.79%), whereas Najas marina and Vallisneria gigantea lost 91.15 and 86.02% of their respective initial mass during that time. The overall exponential breakdown rates of Najas marina and Vallisneria gigantea were similar, with k-values of 0.24 and 0.23 day 1 , respectively. These rates were significantly higher than the break down rates of charophytes (0.007 day 1 ) and M. sulsagineum (0.008 day 1 ). During growth phase, water column depicted lower nutrient concentrations while during decay period, significant increase in water column nutrients resulted. Release of nutrients from decomposing macrophytes and incorporation of these nutrients into sedimentary phase as well as uptake of nutrients by the growing macrophytes, can present a considerable cycling pathway of nutrients in Myall lake system. The results of this study suggest that different submerged macrophytes may differ appreciably in quality and may exhibit different decomposition rates, patterns and nutrient dynamics in aquatic ecosystems in general, and Myall lakes in particular.
The effects of catchment land use on water quality and macroinvertebrate assemblages in Otara Creek, New Zealand
(2011-09) Shilla, Dativa; Shilla, Daniel
The effect of catchment land use on water quality and macroinvertebrate communities was examined by using data gathered during a 2004 reconnaissance of nine sites in the Otara Creek, New Zealand. Data collected included macroinvertebrate, water chemistry and sediments characteristics. Macroinvertebrate data were used in metric and index calculations. A total of 61 macroinvertebrate taxa, with 3032 total individuals, were identified from the macroinvertebrates samples collected from nine sites in Otara Creek. The greatest number of macroinvertebrate taxa was recorded within bush sites (mean>25), while the urban sites had the least number of taxa (mean=10). Pasture sites were intermediate with the mean>17. Taxa number differed significantly across land use. Mean macroinvertebrates abundance varied across the sites and land uses. The highest macroinvertebrates mean abundance was recorded in urban and pasture sites, while bush sites had significantly lower mean abundance. Physico-chemical parameters decreased from bush toward urban streams. Biotic indices were sensitive to changes in macroinvertebrates community structure across land uses with mean scores decreasing from bush to urban and pasture streams. Ordination of biological data showed a clear separation of bush from urban and pastures streams. Analysis of similarities revealed significant differences in macroinvertebrates between both stream groups and land-use groups. The observed macroinvertebrate assemblage pattern was best correlated with a single variable, conductivity, temperature, turbidity, nitrate and dissolved oxygen. The combination of these environmental variables best explained the changes in the macroinvertebrate assemblages between sites. This study demonstrates that catchment land use may significantly affect the water quality and macroinvertebrate communities in an ecosystem.
Effects of riparian vegetation and bottom substrate on macroinvertebrate communities at selected sites in the Otara Creek, New Zealand
(2012-08) Shilla, Dativa; Shilla, Daniel
The effects of riparian vegetation and bottom substrate on water quality and macroinvertebrate communities were assessed by utilising data gathered during a 2004 reconnaissance of nine sites in the Otara Creek, New Zealand. The aim of the study was to use multivariate statistical techniques to better explain the specific environmental factors that drive biological communities in an environment. During the survey, macroinvertebrate assemblages were sampled along with water quality, bottom substrate, riparian vegetation and habitat assessments. Multivariate statistical analyses of habitat and channel characteristics, physical conditions and water quality data were used to determine the relationship between environmental variables and the macroinvertebrate community structure. Ordination of biological and environmental data showed a clear separation of bush from urban and pastures streams. The observed macroinvertebrates assemblage pattern was best correlated with a single variable, riparian width (r = 0.81), a combination of two variables: cobbles and riparian width (r = 0.88), three variables: boulders, nitrate and riparian width (r = 0.91) and five variables: habitat score, shade, boulders, nitrate and riparian width (r = 0.94). The BIO-ENV procedure showed that habitat and channel characteristics had the greatest relationship to macroinvertebrate community structure followed by water chemistry.
Effects of Riparian Vegetation and Bottom Substrate on Macroinvertebrate Communities at Selected Sites in the Otara Creek, New Zealand
(Taylor and Francis, 2012-09) Shilla, Dativa; Shilla, Daniel
The effects of riparian vegetation and bottom substrate on water quality and macroinvertebrate communities were assessed by utilising data gathered during a 2004 reconnaissance of nine sites in the Otara Creek, New Zealand. The aim of the study was to use multivariate statistical techniques to better explain the specific environmental factors that drive biological communities in an environment. During the survey, macroinvertebrate assemblages were sampled along with water quality, bottom substrate, riparian vegetation and habitat assessments. Multivariate statistical analyses of habitat and channel characteristics, physical conditions and water quality data were used to determine the relationship between environmental variables and the macroinvertebrate community structure. Ordination of biological and environmental data showed a clear separation of bush from urban and pastures streams. The observed macroinvertebrates assemblage pattern was best correlated with a single variable, riparian width (r = 0.81), a combination of two variables: cobbles and riparian width (r = 0.88), three variables: boulders, nitrate and riparian width (r = 0.91) and five variables: habitat score, shade, boulders, nitrate and riparian width (r = 0.94). The BIO-ENV procedure showed that habitat and channel characteristics had the greatest relationship to macroinvertebrate community structure followed by water chemistry.
Fluxes and Retention of Nutrients and Organic Carbon in Manko Estuary, Okinawa, Japan: Influence of River Discharge Variations
(2014) Shilla, Daniel
Estuaries are often considered important filters for inorganic and organic nutrients, as they are located between the land and sea. This study reports on the fluvial fluxes and estuarine transformations and retention of dissolved nutrients (total oxidized nitrogen [TON = NO2− and NO3−]), NH4+, PO43−, and dissolved organic carbon (DOC) in Manko estuary, Okinawa, Japan. The transport and transformation of dissolved nutrients and DOC varied widely among the eight conducted surveys due to variations in freshwater discharge and subsequent flushing times. Under high fluvial discharge, particularly during the May–June rainy season, the transport of nutrients and DOC accounted for up to 70%, 88%, 93%, and 53% of the annual transport of TON, NH4+, PO43−, and DOC, respectively. The flushing times of river water into the estuary, which varied from 0.5 to 46 days, were important in determining the degree to which fluvial nutrients were transformed and retained within the estuary. The effect of long flushing times was evident during the dry months (December–March), when biological and geochemical processes within the estuary removed most of the fluvial nutrients and DOC.
Hydrobiologia 541 (2005) Decomposition of Eichhornia crassipes
(2013-04) Sanderson, Brian; Shilla, Daniel; Fujino, Takeshi; Asaeda, Takashi
The water hyacint h (Eichhornia crassipes (Mart.) Solms.) plants in lakes and reservoirs have gained con-siderable attention in tropical and sub-tropical parts of the world due to its rapid growth. The amount ofnutrients released from the dead plant materials is of particular interest. Thus, decomposition of waterhyacinth plant parts under aerobic conditions was studied in the laboratory. Roots , petioles, and leaves ofwater hyacinth were enclosed separately in one litre polypropylene bottles which contained 500 ml of lakewater. To study the inﬂuence of bacteria on the decomposition, antibiotics were added to half of the bottles.We observed that decomposition of leaves and petioles without antibiotics were relatively rapid throughday 61, with almost 92.7 and 97.3% of the dry mass removed, respectively. Weight loss due to bacterialactivities during 94 days decomposition was 22.6, 3.9, and 30.5% from leaf, petiole, and root litter.Decomposition of litter in lake water indica ted that after 94 days 0.6, 0, and 0.6 g m)2of leaf, petiole, androot N was dissolved in leachate, while 23.1, 14.4, and 6.0 g m)2of leaf, petiole, and root N was eithervolatilized or remained as particulate organic N. Moreover, 0.2, 0, and 0.1 g m)2of leaf, petiole, and root Premained dissolved in the leachate, while 3.1, 3.4, and 1.1 g m)2of leaf, petiole, and root P was eitherprecipitated or remained as particulate organic P. The carbon dynamics during the decomposition indicatedthat 7.4, 28.8, and 3.7 g m)2of leaf, petiole, and root C remained dissolved in the leachate afte r 94 dayswhile 228.0, 197.6, and 107.4 g m)2of leaf, petiole, and root C was either diﬀused or remained as par-ticulate organic C. These ﬁndings are useful for quantifying the nutrient cycles of very shallow lakes withwater hyacinth under aerobic water environment. Further examination of the fate of the plant litter as itmoves down in deep anaerobic water environment, is necessary to understand the leaching process better
Modelling Faecal Streptococci Mortality in Constructed Wetlands Implanted with Eichhornia Crassipes
(2008) Kalibbala, Martin; Mayo, Aloyce W.; Asaeda, Takashi; Shilla, Daniel
Faecal streptococci mortality was investigated in a water hyacinth (Eichhornia crassipes) constructed wetland pond. The wetland was 7.5 m long, 1.5 m wide and 1.0 m deep, and was implanted with E. crassipes. In order to assess the performance of the system towards bacterial mortality, a mathematical model, based on plug flow philosophy was developed. The model incorporated the role of factors, namely solar intensity, pH, dissolved oxygen, temperature, sedimentation, and root attached growth. Model analysis strongly suggests that bacterial mortality rate constant was largely influenced by two factors, namely solar intensity and root biofilm attachment, with both contributing approximately 70.5% of removal. The contribution of other factors like temperature, dissolved oxygen, pH and sedimentation on bacterial mortality rate were less significant. For example, dissolved oxygen, pH and sedimentation contributed 5%, 8% and 0.82%, respectively. Thus, the sedimentation factor was omitted from the model because of its insignificant contribution. The same was done for temperature, due to low ambient temperature range (3.1°C) in the study area. The overall model bacterial removal efficiency was 83%.
Phosphorus speciation in Myall Lake sediment, NSW, Australia
(2009-03) Shilla, Daniel; Asaeda, Takashi; Kalibbala, Martin
The amount of phosphorus and its fractions in the sediment of Lake Myall, NSW, Australia, was assessed using a sequential extraction technique. Five sedimentary phosphorus reservoirs were measured, namely loosely sorbed phosphorus (NH4Cl–P), iron associated phosphorus (BD–P), calcium bound phosphorus (HCl–P), metal oxide bound phosphorus (NaOH–P) and residual phosphorus (organic and refractory P, Res-P). Samples were taken from the deep and shallow sites of the lake. During the analysis, the average concentrations of each fraction of phosphorus was calculated. The results depicted that the total phosphorus (TP) content and chemically extractable phosphorus in both fine and coarse sediment fractions from the deep sites of the lake were significantly higher than those of the shallow sites, except for HCl–P extracted from the fine sediment fraction. Sediment TP was also strongly and positively correlated to sediment Fe. The phosphorus in the sediment mainly consisted of BD–P and Res-P, while NH4Cl–P and HCl–P only contributed a minor part. The rank order of the different phosphorus extracts was similar for the two sites, namely Residual-P>BD–P>NaOH–P>HCl–P>NH4Cl–P.
Speciation of heavy metals in sediments from the Scheldt estuary, Belgium
(2011-01) Shilla, Daniel; Dativa, J.
A simple three-step sequential extraction procedure was applied to study the speciation of heavy metals in sediment from Scheldt estuary, and their relationship to sediment grain size and organic matter content. The sedimentary metal content was fractionated into carbonate and exchangeable, metals bound to organic matter and residual fractions. Sedimentary total metal content was also determined using an industrial microwave (ETHOS 900) HF/HNO3 extraction method. The extracts were analysed for metals using inductively coupled plasma atomic emission spectrometry. The bioavailable fraction (exchangeable and metals bound to organic matter) comprised less than the other forms. Residue metals were the dominant form of metals in almost all studied sites. The average total metal content for the studied sites decreased in the order Fe>Cr>Cu>Co>Zn>Pb>Cd. Based on average values for the studied sites, the highest bioavailable metals in sediments were Cd (38%) from Westkapelle, Zn (17%) from Yerseke, Co (12%) from Domburg, Cr (9%) from Vlissingen, Fe and Pb each (2%) from Yerseke, and Cu (1%) from Domburg. Metal recovery was good, with<10% difference between the total metal recovered through the extractant steps and the total metal determined using HF/HNO3 extract.
Terrigenous Nutrient and Organic Matter in a Subtropical River Estuary, Okinawa, Japan: Origin, Distribution and Pattern across the Estuarine Salinity Gradient
(Taylor and Francis, 2011) Shilla, Dativa; Tsuchiya, Makoto; Shilla, Daniel
Estuaries and their associated rivers are organically rich sites that play an important role in the removal and transformation of organic matter and nutrients derived from terrigenous and anthropogenic sources. This study conducted comprehensive field surveys from March 2010 to January 2011 to study the downstream pattern and distribution of nutrients (NO , NO , NH and PO ) and dissolved organic carbon (DOC) and particulate organic carbon (POC) and nitrogen (PN) in the surface waters of the Manko estuary, a subtropical estuary in Okinawa, Japan. Fatty acid (FA) analysis and POC–C/N ratios were used to further identify variations in the sources of particulate organic matter along the estuary during summer (July) and winter (January). The results suggest that the estuary contains high concentrations of dissolved inorganic (N and P) and organic (DOC) nutrients, which are largely influenced by terrestrial sources from the Kokuba and Noha rivers, and moderate levels of particulate nitrogen and carbon. In general, suspended particles and dissolved nutrients followed sedimentation and biotic uptake patterns common in other subtropical estuaries. Thus, an important fraction of terrestrial materials was rapidly sinking along the estuary and was replaced with estuarine and marine-derived materials at mid- to high-salinity along the estuary. The FA signatures suggested that bacteria, domestic and agricultural waste-derived organic matter were the dominant sources of suspended organic matter in the Manko estuary. Overall, despite the relatively high terrestrial and anthropogenic influences in the Manko estuary, effective processing of different sources and forms of terrigenous organic matter in the estuarine salinity gradient significantly reduces their signatures prior to export to the coastal ocean.
Terrigenous nutrient and organic matter in a subtropical river estuary, Okinawa, Japan: Origin, distribution and pattern across the estuarine salinity gradient
(2011-11) Shilla, Dativa; Tsuchiya, Makoto; Shilla, Daniel
Estuaries and their associated rivers are organically rich sites that play an important role in the removal and transformation of organic matter and nutrients derived from terrigenous and anthropogenic sources. This study conducted comprehensive field surveys from March 2010 to January 2011 to study the downstream pattern and distribution of nutrients (NO , NO , NH and PO ) and dissolved organic carbon (DOC) and particulate organic carbon (POC) and nitrogen (PN) in the surface waters of the Manko estuary, a subtropical estuary in Okinawa, Japan. Fatty acid (FA) analysis and POC–C/N ratios were used to further identify variations in the sources of particulate organic matter along the estuary during summer (July) and winter (January). The results suggest that the estuary contains high concentrations of dissolved inorganic (N and P) and organic (DOC) nutrients, which are largely influenced by terrestrial sources from the Kokuba and Noha rivers, and moderate levels of particulate nitrogen and carbon. In general, suspended particles and dissolved nutrients followed sedimentation and biotic uptake patterns common in other subtropical estuaries. Thus, an important fraction of terrestrial materials was rapidly sinking along the estuary and was replaced with estuarine and marine-derived materials at mid- to high-salinity along the estuary. The FA signatures suggested that bacteria, domestic and agricultural waste-derived organic matter were the dominant sources of suspended organic matter in the Manko estuary. Overall, despite the relatively high terrestrial and anthropogenic influences in the Manko estuary, effective processing of different sources and forms of terrigenous organic matter in the estuarine salinity gradient significantly reduces their signatures prior to export to the coastal ocean.

Browsing by Author "Shilla, Daniel"

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