Can δ15N and δ13C stable isotopes and fatty acid signatures indicate changes in phytobenthos composition on an artificial substrate?
- Dalu, Tatenda, Froneman, P William
- Authors: Dalu, Tatenda , Froneman, P William
- Date: 2014
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/68086 , vital:29197 , https://doi.org/10.2989/16085914.2014.974018
- Description: Publisher version , Temporal changes in fatty acid composition and δ15N, δ13C stable isotope values of the phytobenthos growing on artificial clay substrates under natural conditions over a 28-day period at an upstream and a downstream site in the Kowie River near Grahamstown were investigated in 2012. High concentrations of diatom markers 16:1ω7 and 20:5ω3 fatty acids were recorded, especially at the downstream site, reflecting the importance of diatoms in contributing to the phytobenthos communities at that station. After day 7 at the downstream site the average δ15N value of the phytobenthos was lighter, gradually increasing by ∼2‰ and ∼5‰ overall to heavier values on day 28. At the upstream site there were no significant changes (<1‰ increase) in δ15N values of the phytobenthos over time. Stable nitrogen (δ15N) and carbon (δ13C) signatures in the phytobenthos communities were significantly different between sites (one-way ANOVA; p < 0.001). The stable isotope values and fatty acid concentrations of phytobenthos at the downstream site were different to those of the phytobenthos at the upstream site, and they changed concurrently with changes in the phytobenthos community structure. At the downstream site there was a strong correlation of the δ15N of phytobenthos with nitrates (R = 0.56) and time (weeks; R = 0.81). However, the fatty acids were not specific enough to characterise the composition of phytobenthos communities. Other biomarker methods, such as stable isotopes and microscopic examination of the communities, were found to be useful. The results from this relatively small-scale tile experiment indicate the complexity of changes in fatty acid composition and δ15N, δ13C stable isotope values of a phytobenthos community. Stable isotope and fatty acid composition can be successfully used to map changes in phytobenthos composition and carbon and nitrogen flow patterns along a river continuum.
- Full Text: false
- Authors: Dalu, Tatenda , Froneman, P William
- Date: 2014
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/68086 , vital:29197 , https://doi.org/10.2989/16085914.2014.974018
- Description: Publisher version , Temporal changes in fatty acid composition and δ15N, δ13C stable isotope values of the phytobenthos growing on artificial clay substrates under natural conditions over a 28-day period at an upstream and a downstream site in the Kowie River near Grahamstown were investigated in 2012. High concentrations of diatom markers 16:1ω7 and 20:5ω3 fatty acids were recorded, especially at the downstream site, reflecting the importance of diatoms in contributing to the phytobenthos communities at that station. After day 7 at the downstream site the average δ15N value of the phytobenthos was lighter, gradually increasing by ∼2‰ and ∼5‰ overall to heavier values on day 28. At the upstream site there were no significant changes (<1‰ increase) in δ15N values of the phytobenthos over time. Stable nitrogen (δ15N) and carbon (δ13C) signatures in the phytobenthos communities were significantly different between sites (one-way ANOVA; p < 0.001). The stable isotope values and fatty acid concentrations of phytobenthos at the downstream site were different to those of the phytobenthos at the upstream site, and they changed concurrently with changes in the phytobenthos community structure. At the downstream site there was a strong correlation of the δ15N of phytobenthos with nitrates (R = 0.56) and time (weeks; R = 0.81). However, the fatty acids were not specific enough to characterise the composition of phytobenthos communities. Other biomarker methods, such as stable isotopes and microscopic examination of the communities, were found to be useful. The results from this relatively small-scale tile experiment indicate the complexity of changes in fatty acid composition and δ15N, δ13C stable isotope values of a phytobenthos community. Stable isotope and fatty acid composition can be successfully used to map changes in phytobenthos composition and carbon and nitrogen flow patterns along a river continuum.
- Full Text: false
Colonisation and community structure of benthic diatoms on artificial substrates following a major flood event: a case of the Kowie River (Eastern Cape, South Africa)
- Dalu, Tatenda, Froneman, P William, Chari, Lenin D, Richoux, Nicole B
- Authors: Dalu, Tatenda , Froneman, P William , Chari, Lenin D , Richoux, Nicole B
- Date: 2014
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/143357 , vital:38239 , http://dx.doi.org/10.4314/wsa.v40i3.10
- Description: A major flooding event that occurred during October–November 2012 caused major changes in the Kowie River hydromorphology and aquatic communities. The aim of our study was to identify the environmental variables that structure riverine benthic diatom communities at upstream and downstream locations 25 km apart on the Kowie River, South Africa. This was undertaken using tiles as artificial substrates so that we could study how the communities developed after the flood disturbance. The diatom community structure was assessed over a 28-day period following a flood event in October 2012. The Mann Whitney test indicated that there was a statistically significant difference (p 0.05) in total dissolved solids, salinity, pH and oxygen reduction potential between the two sites. In total, 58 diatom species belonging to 30 genera were identified over the 28-day study.
- Full Text:
- Authors: Dalu, Tatenda , Froneman, P William , Chari, Lenin D , Richoux, Nicole B
- Date: 2014
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/143357 , vital:38239 , http://dx.doi.org/10.4314/wsa.v40i3.10
- Description: A major flooding event that occurred during October–November 2012 caused major changes in the Kowie River hydromorphology and aquatic communities. The aim of our study was to identify the environmental variables that structure riverine benthic diatom communities at upstream and downstream locations 25 km apart on the Kowie River, South Africa. This was undertaken using tiles as artificial substrates so that we could study how the communities developed after the flood disturbance. The diatom community structure was assessed over a 28-day period following a flood event in October 2012. The Mann Whitney test indicated that there was a statistically significant difference (p 0.05) in total dissolved solids, salinity, pH and oxygen reduction potential between the two sites. In total, 58 diatom species belonging to 30 genera were identified over the 28-day study.
- Full Text:
Evidence of spatial and temporal changes in sources of organic matter in estuarine sediments
- Bergamino, Leandro, Dalu, Tatenda, Richoux, Nicole B
- Authors: Bergamino, Leandro , Dalu, Tatenda , Richoux, Nicole B
- Date: 2014
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/457242 , vital:75619 , xlink:href="https://doi.org/10.1007/s10750-014-1853-1"
- Description: We investigated spatial and temporal changes in sources of organic matter in sediments within an estuarine environment in South Africa using fatty acids (FA) and stable isotopes (SI). Samples of sediments and sources of organic matter [i.e., particulate organic matter, microphytobenthos (MPB), macrophytes, salt marsh plants, and terrestrial leaves] were collected during spring and summer 2012, and autumn and winter 2013 from the upper, middle, and lower reaches. A Stable Isotope Analysis in R (SIAR) mixing model was used to identify the organic matter sources contributing to sediments in each estuarine reach and season. We found that diatom-associated fatty acids (20:5ω3; 16:1ω7) increased toward the upper reaches, while long-chained terrigenous fatty acids (24:0) tended to be more prevalent in lower reach sediments. In support of the FA results, the SI mixing model showed a substantial contribution from the marsh grass Spartina maritima in sediments of the lower estuary during periods of low-freshwater discharge (autumn and winter), while MPB was the main component in sediments from the upper and middle reaches during all seasons. Our results have implications for evaluating estuarine food webs since the spatial and seasonal variability in the organic matter deposited can influence estuarine community structure.
- Full Text:
- Authors: Bergamino, Leandro , Dalu, Tatenda , Richoux, Nicole B
- Date: 2014
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/457242 , vital:75619 , xlink:href="https://doi.org/10.1007/s10750-014-1853-1"
- Description: We investigated spatial and temporal changes in sources of organic matter in sediments within an estuarine environment in South Africa using fatty acids (FA) and stable isotopes (SI). Samples of sediments and sources of organic matter [i.e., particulate organic matter, microphytobenthos (MPB), macrophytes, salt marsh plants, and terrestrial leaves] were collected during spring and summer 2012, and autumn and winter 2013 from the upper, middle, and lower reaches. A Stable Isotope Analysis in R (SIAR) mixing model was used to identify the organic matter sources contributing to sediments in each estuarine reach and season. We found that diatom-associated fatty acids (20:5ω3; 16:1ω7) increased toward the upper reaches, while long-chained terrigenous fatty acids (24:0) tended to be more prevalent in lower reach sediments. In support of the FA results, the SI mixing model showed a substantial contribution from the marsh grass Spartina maritima in sediments of the lower estuary during periods of low-freshwater discharge (autumn and winter), while MPB was the main component in sediments from the upper and middle reaches during all seasons. Our results have implications for evaluating estuarine food webs since the spatial and seasonal variability in the organic matter deposited can influence estuarine community structure.
- Full Text:
Phytoplankton community diversity along a river-estuary continuum
- Dalu, Tatenda, Froneman, P William, Richoux, Nicole B
- Authors: Dalu, Tatenda , Froneman, P William , Richoux, Nicole B
- Date: 2014
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/457284 , vital:75622 , xlink:href="https://hdl.handle.net/10520/EJC156752"
- Description: In this paper we examine the aspects of phytoplankton communities along a riverine-estuarine continuum in the Kowie system, Eastern Cape (South Africa). This study aims to relate the phytoplankton population community structure to physicochemical parameters and estimate the different chlorophyll-a concentrations for the Kowie system. Eight sampling sites along a 70 km reach of the Kowie system were sampled over a one-year period. One hundred and seventy-eight species belonging to 78 genera were recorded within the riverine-estuarine continuum. Diatoms were predominant, accounting for 81.9% of the total abundance. The estuary had 98 species (55 genera) recorded whereas the river had 141 species (67 genera). Using a two-way analysis of variance (ANOVA), species richness was found to differ significantly amongst seasons. The chl-a concentration along the estuarine-riverine continuum increased from spring to a high in summer (river mean = 7.9 mg m -3 and estuary mean = 3.3 mg m -3 ) before decreasing to a low in winter. Kruskal Wallis ANOVA showed significant differences among chl-a concentration with seasons and sites. Redundancy analysis identified five factors salinity, water depth, aerial cover, nitrates and ammonia that were significant (p is less than 0.05) in affecting phytoplankton variation. The relatively small study indicates the need for further monitoring to gain a better understanding of Kowie system phytoplankton.
- Full Text:
- Authors: Dalu, Tatenda , Froneman, P William , Richoux, Nicole B
- Date: 2014
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/457284 , vital:75622 , xlink:href="https://hdl.handle.net/10520/EJC156752"
- Description: In this paper we examine the aspects of phytoplankton communities along a riverine-estuarine continuum in the Kowie system, Eastern Cape (South Africa). This study aims to relate the phytoplankton population community structure to physicochemical parameters and estimate the different chlorophyll-a concentrations for the Kowie system. Eight sampling sites along a 70 km reach of the Kowie system were sampled over a one-year period. One hundred and seventy-eight species belonging to 78 genera were recorded within the riverine-estuarine continuum. Diatoms were predominant, accounting for 81.9% of the total abundance. The estuary had 98 species (55 genera) recorded whereas the river had 141 species (67 genera). Using a two-way analysis of variance (ANOVA), species richness was found to differ significantly amongst seasons. The chl-a concentration along the estuarine-riverine continuum increased from spring to a high in summer (river mean = 7.9 mg m -3 and estuary mean = 3.3 mg m -3 ) before decreasing to a low in winter. Kruskal Wallis ANOVA showed significant differences among chl-a concentration with seasons and sites. Redundancy analysis identified five factors salinity, water depth, aerial cover, nitrates and ammonia that were significant (p is less than 0.05) in affecting phytoplankton variation. The relatively small study indicates the need for further monitoring to gain a better understanding of Kowie system phytoplankton.
- Full Text:
Stable isotope evidence of food web connectivity by a top predatory fish (Argyrosomus japonicus: Sciaenidae: Teleostei) in the Kowie Estuary, South Africa
- Bergamino, Leandro, Dalu, Tatenda, Whitfield, Alan K, Carassou, Laure, Richoux, Nicole B
- Authors: Bergamino, Leandro , Dalu, Tatenda , Whitfield, Alan K , Carassou, Laure , Richoux, Nicole B
- Date: 2014
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/457322 , vital:75625 , xlink:href="https://doi.org/10.2989/1814232X.2014.923782"
- Description: In this study, food web connectivity within the Kowie Estuary on the south-east coast of South Africa was evidenced by the trophic behaviour of the predominantly piscivorous Argyrosomus japonicus. We examined stable isotopes of carbon (δ13C) and nitrogen (δ15N) in the dominant consumers (zooplankton, invertebrates and fishes) and food sources (particulate organic matter, epibionts and benthic microalgae) in the system. An SIAR (Stable Isotope Analysis in R) mixing model was used to interpret the possible food sources for this dominant top predatory fish. Small fishes and large epibenthic invertebrates dominated the diet of A. japonicus. Based on the contrasting diet of these prey fish and invertebrates, we propose that organic matter enters the predatory fish community via two major pathways: (1) a littoral pathway dominated by benthic microalgae production and epibionts, and (2) a channel pathway dominated by suspended particulate organic matter (including phytoplankton). We conclude that the highly mobile A. japonicus consumes both pelagic and benthic fauna from the littoral and channel zones of the estuary, thereby playing a key functional role in linking food webs. This dietary diversity may help explain the success of A. japonicus as a dominant top predator in the system, primarily by increasing the energy available to this species.
- Full Text:
- Authors: Bergamino, Leandro , Dalu, Tatenda , Whitfield, Alan K , Carassou, Laure , Richoux, Nicole B
- Date: 2014
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/457322 , vital:75625 , xlink:href="https://doi.org/10.2989/1814232X.2014.923782"
- Description: In this study, food web connectivity within the Kowie Estuary on the south-east coast of South Africa was evidenced by the trophic behaviour of the predominantly piscivorous Argyrosomus japonicus. We examined stable isotopes of carbon (δ13C) and nitrogen (δ15N) in the dominant consumers (zooplankton, invertebrates and fishes) and food sources (particulate organic matter, epibionts and benthic microalgae) in the system. An SIAR (Stable Isotope Analysis in R) mixing model was used to interpret the possible food sources for this dominant top predatory fish. Small fishes and large epibenthic invertebrates dominated the diet of A. japonicus. Based on the contrasting diet of these prey fish and invertebrates, we propose that organic matter enters the predatory fish community via two major pathways: (1) a littoral pathway dominated by benthic microalgae production and epibionts, and (2) a channel pathway dominated by suspended particulate organic matter (including phytoplankton). We conclude that the highly mobile A. japonicus consumes both pelagic and benthic fauna from the littoral and channel zones of the estuary, thereby playing a key functional role in linking food webs. This dietary diversity may help explain the success of A. japonicus as a dominant top predator in the system, primarily by increasing the energy available to this species.
- Full Text:
Using multivariate analysis and stable isotopes to assess the effects of substrate type on phytobenthos communities
- Dalu, Tatenda, Richoux, Nicole B, Froneman, P William
- Authors: Dalu, Tatenda , Richoux, Nicole B , Froneman, P William
- Date: 2014
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/68123 , vital:29201 , https://doi.org/10.5268/IW-4.4.719
- Description: Publisher version , For more than a century, artificial substrates have been employed in phytobenthos studies. In the present study, we compared the phytobenthos community structure in a field experiment over 3 seasons (summer, autumn, and winter) on 3 types of artificial substrates (brick, brown clay tiles, and grey clay tiles) and 3 natural substrates (macrophytes, rocks, and sediment) in a small, temperate system. A combination of multivariate analyses (cluster, multi-response permutation procedure, indicator species [IndVal], and canonical correspondence analysis [CCA]) and stable isotope analysis was used. We identified 96 total phytobenthos taxa. Artificial substrates resulted in different substrate communities, as shown by stable isotope analysis, cluster analysis, and a multi-response permutation procedure, with only those communities growing on grey tiles being similar to natural substrate communities. Overall, artificial substrates exhibited slightly higher species richness compared to natural substrates over the 3 seasons, although there were no significant differences (p> 0.05). Phytobenthos grown on brown tiles, rocks, and bricks showed seasonal variability of the carbon isotope δ13C values using one-way ANOVA (p< 0.05). Phytobenthos community structure did not show great seasonal variation; however, CCA identified water flow, conductivity, ammonium, phosphate, and water depth as important in structuring phytobenthos communities on different substrates. IndVal analysis showed that common phytobenthos taxa were not restricted to a single substrate, but preference was generally high for natural substrate, especially rocks, compared to artificial substrates. Substrate microhabitat type seems to influence the communities within the study areas.
- Full Text: false
- Authors: Dalu, Tatenda , Richoux, Nicole B , Froneman, P William
- Date: 2014
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/68123 , vital:29201 , https://doi.org/10.5268/IW-4.4.719
- Description: Publisher version , For more than a century, artificial substrates have been employed in phytobenthos studies. In the present study, we compared the phytobenthos community structure in a field experiment over 3 seasons (summer, autumn, and winter) on 3 types of artificial substrates (brick, brown clay tiles, and grey clay tiles) and 3 natural substrates (macrophytes, rocks, and sediment) in a small, temperate system. A combination of multivariate analyses (cluster, multi-response permutation procedure, indicator species [IndVal], and canonical correspondence analysis [CCA]) and stable isotope analysis was used. We identified 96 total phytobenthos taxa. Artificial substrates resulted in different substrate communities, as shown by stable isotope analysis, cluster analysis, and a multi-response permutation procedure, with only those communities growing on grey tiles being similar to natural substrate communities. Overall, artificial substrates exhibited slightly higher species richness compared to natural substrates over the 3 seasons, although there were no significant differences (p> 0.05). Phytobenthos grown on brown tiles, rocks, and bricks showed seasonal variability of the carbon isotope δ13C values using one-way ANOVA (p< 0.05). Phytobenthos community structure did not show great seasonal variation; however, CCA identified water flow, conductivity, ammonium, phosphate, and water depth as important in structuring phytobenthos communities on different substrates. IndVal analysis showed that common phytobenthos taxa were not restricted to a single substrate, but preference was generally high for natural substrate, especially rocks, compared to artificial substrates. Substrate microhabitat type seems to influence the communities within the study areas.
- Full Text: false
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