Distribution of benthic diatom communities in a permanently open temperate estuary in relation to physico-chemical variables
- Dalu, Tatenda, Richoux, Nicole B, Froneman, P William
- Authors: Dalu, Tatenda , Richoux, Nicole B , Froneman, P William
- Date: 2016
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/67943 , vital:29172 , https://doi.org/10.1016/j.sajb.2015.06.004
- Description: Publisher version , The spatial and temporal patterns in benthic diatom community structure in temperate permanently open estuaries are poorly understood. In this study, we used a combination of multivariate and diversity indices to elucidate environmental factors associated with diatom community structure in the Kowie Estuary, South Africa. Benthic diatom samples were collected from three sites corresponding to the upper, middle and lower reaches of the estuary on four occasions over the period early spring 2012 to winter 2013. Among the 89 benthic diatoms observed, Entomoneis paludosa (W Smith) Reimer, Nitzschia reversa W Smith, Nitzschia closterium (Ehrenberg) W Smith, Pleurosigma elongatum W Smith, P. salinarum (Grunow) Grunow, Staurosira elliptica (Schumann) DM Williams & Round, Surirella brebissonii Krammer & Lange-Bertalot, and Surirella ovalis Brébisson were the numerically dominant species. Principal component analysis demonstrated that the diatom community structure was determined by a variety of factors including nutrient (ammonia, nitrate) concentrations, hydrology (e.g., water depth and flow) and pH. Hierarchical cluster analysis revealed the absence of any distinct spatial patterns, although distinct benthic diatom communities were recorded during the different sampling periods. The species richness was highest in the middle reach, decreasing from early spring to summer in all reaches. The results of the study provide important insights into the various factors that structure benthic diatom community composition within a permanently open temperate southern African estuary.
- Full Text: false
- Date Issued: 2016
- Authors: Dalu, Tatenda , Richoux, Nicole B , Froneman, P William
- Date: 2016
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/67943 , vital:29172 , https://doi.org/10.1016/j.sajb.2015.06.004
- Description: Publisher version , The spatial and temporal patterns in benthic diatom community structure in temperate permanently open estuaries are poorly understood. In this study, we used a combination of multivariate and diversity indices to elucidate environmental factors associated with diatom community structure in the Kowie Estuary, South Africa. Benthic diatom samples were collected from three sites corresponding to the upper, middle and lower reaches of the estuary on four occasions over the period early spring 2012 to winter 2013. Among the 89 benthic diatoms observed, Entomoneis paludosa (W Smith) Reimer, Nitzschia reversa W Smith, Nitzschia closterium (Ehrenberg) W Smith, Pleurosigma elongatum W Smith, P. salinarum (Grunow) Grunow, Staurosira elliptica (Schumann) DM Williams & Round, Surirella brebissonii Krammer & Lange-Bertalot, and Surirella ovalis Brébisson were the numerically dominant species. Principal component analysis demonstrated that the diatom community structure was determined by a variety of factors including nutrient (ammonia, nitrate) concentrations, hydrology (e.g., water depth and flow) and pH. Hierarchical cluster analysis revealed the absence of any distinct spatial patterns, although distinct benthic diatom communities were recorded during the different sampling periods. The species richness was highest in the middle reach, decreasing from early spring to summer in all reaches. The results of the study provide important insights into the various factors that structure benthic diatom community composition within a permanently open temperate southern African estuary.
- Full Text: false
- Date Issued: 2016
Temporal and spatial variability in the abundance, biomass and distribution of Palaemon peringueyi (Decapoda: Crustacea) are influenced by biological but not physico-chemical factors in the permanently open Kariega Estuary, South Africa
- Nyalungu, Nonhlanhla P, Hodgson, Alan N, Froneman, P William, Dopolo, M, Masubelele, M
- Authors: Nyalungu, Nonhlanhla P , Hodgson, Alan N , Froneman, P William , Dopolo, M , Masubelele, M
- Date: 2014
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/68106 , vital:29200 , https://doi.org/10.2989/16085914.2014.960792
- Description: Publisher version , Biological and physico-chemical factors affecting abundance and biomass of shrimp Palaemon peringueyi were investigated in 2010–2011 in the lower, middle and upper reaches of the freshwater-deprived permanently open Kariega Estuary. Shrimp abundance and biomass ranged from 0 to 88 ind. m−2 and 0 to 4.4 g wwt m−2, respectively. Shrimps were most abundant in the lower reach, and highest abundances and biomasses were recorded in the lower reach in June when salinities were low. The shrimps were almost always absent in the upper reach. Juveniles were found mostly in the lower and middle reaches, whereas adults were distributed in all three reaches. Regression analyses showed no statistically significant relationship for either abundance or biomass of the shrimps with temperature, salinity and dissolved oxygen (p > 0.05). The relationship between shrimp abundance and biomass and vegetation cover was positive and statistically significant (R2 = 0.109 and 0.185, respectively; p < 0.05). Vegetation cover plays an important role in determining the presence, distribution and abundance or biomass of P. peringueyi in this estuary.
- Full Text: false
- Date Issued: 2014
- Authors: Nyalungu, Nonhlanhla P , Hodgson, Alan N , Froneman, P William , Dopolo, M , Masubelele, M
- Date: 2014
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/68106 , vital:29200 , https://doi.org/10.2989/16085914.2014.960792
- Description: Publisher version , Biological and physico-chemical factors affecting abundance and biomass of shrimp Palaemon peringueyi were investigated in 2010–2011 in the lower, middle and upper reaches of the freshwater-deprived permanently open Kariega Estuary. Shrimp abundance and biomass ranged from 0 to 88 ind. m−2 and 0 to 4.4 g wwt m−2, respectively. Shrimps were most abundant in the lower reach, and highest abundances and biomasses were recorded in the lower reach in June when salinities were low. The shrimps were almost always absent in the upper reach. Juveniles were found mostly in the lower and middle reaches, whereas adults were distributed in all three reaches. Regression analyses showed no statistically significant relationship for either abundance or biomass of the shrimps with temperature, salinity and dissolved oxygen (p > 0.05). The relationship between shrimp abundance and biomass and vegetation cover was positive and statistically significant (R2 = 0.109 and 0.185, respectively; p < 0.05). Vegetation cover plays an important role in determining the presence, distribution and abundance or biomass of P. peringueyi in this estuary.
- Full Text: false
- Date Issued: 2014
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
- Date Issued: 2014
- 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
- Date Issued: 2014
Biological responses to a resumption in river flow in a freshwater-deprived, permanently open Southern African estuary
- Vorwerk, Paul D, Froneman, P William, Paterson, Angus W, Strydom, Nadine A, Whitfield, Alan K
- Authors: Vorwerk, Paul D , Froneman, P William , Paterson, Angus W , Strydom, Nadine A , Whitfield, Alan K
- Date: 2008
- Language: English
- Type: text , Article
- Identifier: vital:6886 , http://hdl.handle.net/10962/d1011645
- Description: The Kariega Estuary is a freshwater-deprived system due to numerous impoundments in the catchment. This system has had little or no horizontal salinity gradient over the last 15 years, with hypersaline conditions sometimes predominating in the upper reaches. Following high rainfall events in the catchment during the spring of 2006, including a flood event (approximate 1:10 year) in August 2006, a series of riverine pulses entered the estuary and a horizontal salinity gradient was established. This study examined the influence of this freshwater pulse on four components of the biota within the estuary, namely the zooplankton, and larval, littoral and demersal fishes. The study demonstrated that in three of these components elevated densities were recorded following the riverine input, with only the littoral fishes retaining an almost constant density. In addition, changes in the relative contributions of the estuarine utilisation classes for all three fish groups examined indicated that freshwater input into these systems positively influences the abundances. This has significant implications for water managers as it demonstrates the importance of an Ecological Reserve (defined as ‘the water required to protect the aquatic ecosystems of the water resource’) for this system.
- Full Text:
- Date Issued: 2008
- Authors: Vorwerk, Paul D , Froneman, P William , Paterson, Angus W , Strydom, Nadine A , Whitfield, Alan K
- Date: 2008
- Language: English
- Type: text , Article
- Identifier: vital:6886 , http://hdl.handle.net/10962/d1011645
- Description: The Kariega Estuary is a freshwater-deprived system due to numerous impoundments in the catchment. This system has had little or no horizontal salinity gradient over the last 15 years, with hypersaline conditions sometimes predominating in the upper reaches. Following high rainfall events in the catchment during the spring of 2006, including a flood event (approximate 1:10 year) in August 2006, a series of riverine pulses entered the estuary and a horizontal salinity gradient was established. This study examined the influence of this freshwater pulse on four components of the biota within the estuary, namely the zooplankton, and larval, littoral and demersal fishes. The study demonstrated that in three of these components elevated densities were recorded following the riverine input, with only the littoral fishes retaining an almost constant density. In addition, changes in the relative contributions of the estuarine utilisation classes for all three fish groups examined indicated that freshwater input into these systems positively influences the abundances. This has significant implications for water managers as it demonstrates the importance of an Ecological Reserve (defined as ‘the water required to protect the aquatic ecosystems of the water resource’) for this system.
- Full Text:
- Date Issued: 2008
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