Effects of substrate on essential fatty acids produced by phytobenthos in an austral temperate river system
- Dalu, Tatenda, Galloway, Aaron W E, Richoux, Nicole B, Froneman, P William
- Authors: Dalu, Tatenda , Galloway, Aaron W E , Richoux, Nicole B , Froneman, P William
- Date: 2016
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/68002 , vital:29179 , https://doi.org/10.1086/688698
- Description: Publisher version , Aquatic and riparian habitats increasingly are affected by anthropogenic stressors, but the effects of these stressors on the nutritional quality of primary producers are often unknown. We compared essential fatty acids (EFAs) in the phytobenthos (benthic algae) growing on different substrate types (bricks, clay tiles, rocks, macrophytes, and sediments) at 2 river sites subject to differing anthropogenic stressors (using nutrient concentration as a proxy) in a temperate southern hemisphere location. We hypothesized that the fatty acid (FA) content of phytobenthos changes in response to shifts in local nutrient availability but not substrate type. EFA content (18∶2ω6, 18∶3ω3, 20∶4ω6, 20∶5ω3, and 22∶6ω3) in the phytobenthos differed overall among substrates, sites, and seasons and was generally greater in summer than in autumn and winter. EFA content was significantly greater on artificial than natural substrates and was greater at the nutrient-enriched downstream site than at the upstream site. The response of EFA content at the downstream site suggests that land use affected the synthesis of EFAs by phytobenthos and, hence, food quality for aquatic consumers. These findings indicate a potential link between physical factors, such as substrate availability and land management, and the quality of basal food resources available to primary consumers in aquatic food webs.
- Full Text: false
- Date Issued: 2016
- Authors: Dalu, Tatenda , Galloway, Aaron W E , Richoux, Nicole B , Froneman, P William
- Date: 2016
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/68002 , vital:29179 , https://doi.org/10.1086/688698
- Description: Publisher version , Aquatic and riparian habitats increasingly are affected by anthropogenic stressors, but the effects of these stressors on the nutritional quality of primary producers are often unknown. We compared essential fatty acids (EFAs) in the phytobenthos (benthic algae) growing on different substrate types (bricks, clay tiles, rocks, macrophytes, and sediments) at 2 river sites subject to differing anthropogenic stressors (using nutrient concentration as a proxy) in a temperate southern hemisphere location. We hypothesized that the fatty acid (FA) content of phytobenthos changes in response to shifts in local nutrient availability but not substrate type. EFA content (18∶2ω6, 18∶3ω3, 20∶4ω6, 20∶5ω3, and 22∶6ω3) in the phytobenthos differed overall among substrates, sites, and seasons and was generally greater in summer than in autumn and winter. EFA content was significantly greater on artificial than natural substrates and was greater at the nutrient-enriched downstream site than at the upstream site. The response of EFA content at the downstream site suggests that land use affected the synthesis of EFAs by phytobenthos and, hence, food quality for aquatic consumers. These findings indicate a potential link between physical factors, such as substrate availability and land management, and the quality of basal food resources available to primary consumers in aquatic food webs.
- Full Text: false
- Date Issued: 2016
Trophic interactions in an austral temperate ephemeral pond inferred using stable isotope analysis
- Dalu, Tatenda, Weyl, Olaf L F, Froneman, P William, Wasserman, Ryan J
- Authors: Dalu, Tatenda , Weyl, Olaf L F , Froneman, P William , Wasserman, Ryan J
- Date: 2016
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/68022 , vital:29185 , https://doi.org/10.1007/s10750-015-2533-5
- Description: Publisher version , Ephemeral ponds are vulnerable aquatic habitats which are difficult to protect given their dynamic nature and sensitivity to degradation during dry periods. Little information is available on these habitats in austral regions, with almost no information on food-web structure and complexity. The study aimed to assess trophic interactions among dominant organisms in an ephemeral pond food web, and investigate the importance of autochthonous and allochthonous carbon, using 13C and 15N isotopes. Results of the investigation suggest that the food web comprised four trophic levels, with the top predators being Notonectids (Notonecta sp.) and diving beetles (Cybister tripunctatus (Olivier)). Intermediary trophic levels comprised zooplankton (daphniids and copepodids), macroinvertebrates (e.g. micronectids and molluscs) and tadpoles. Generalist feeders dominated the higher trophic levels (>3) with specialists comprising the lower trophic levels (≤3). The consumers preferred autochthonous fine particulate organic matter, epiphyton and submerged macrophyte organic matter sources over allochthonous sources. Autochthonous organic matter was transferred to the food web via zooplankton and select macroinvertebrates including Micronecta sp. and Physa sp. The food-web structure within the pond appeared to reflect the secondary stage of trophic structural complexity in the evolution of ephemeral ponds over the course of their hydro-period.
- Full Text: false
- Date Issued: 2016
- Authors: Dalu, Tatenda , Weyl, Olaf L F , Froneman, P William , Wasserman, Ryan J
- Date: 2016
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/68022 , vital:29185 , https://doi.org/10.1007/s10750-015-2533-5
- Description: Publisher version , Ephemeral ponds are vulnerable aquatic habitats which are difficult to protect given their dynamic nature and sensitivity to degradation during dry periods. Little information is available on these habitats in austral regions, with almost no information on food-web structure and complexity. The study aimed to assess trophic interactions among dominant organisms in an ephemeral pond food web, and investigate the importance of autochthonous and allochthonous carbon, using 13C and 15N isotopes. Results of the investigation suggest that the food web comprised four trophic levels, with the top predators being Notonectids (Notonecta sp.) and diving beetles (Cybister tripunctatus (Olivier)). Intermediary trophic levels comprised zooplankton (daphniids and copepodids), macroinvertebrates (e.g. micronectids and molluscs) and tadpoles. Generalist feeders dominated the higher trophic levels (>3) with specialists comprising the lower trophic levels (≤3). The consumers preferred autochthonous fine particulate organic matter, epiphyton and submerged macrophyte organic matter sources over allochthonous sources. Autochthonous organic matter was transferred to the food web via zooplankton and select macroinvertebrates including Micronecta sp. and Physa sp. The food-web structure within the pond appeared to reflect the secondary stage of trophic structural complexity in the evolution of ephemeral ponds over the course of their hydro-period.
- Full Text: false
- Date Issued: 2016
An assessment of the effect of rotenone on selected non-target aquatic fauna:
- Dalu, Tatenda, Wasserman, Ryan J, Jordaan, Martine, Froneman, P William, Weyl, Olaf L F
- Authors: Dalu, Tatenda , Wasserman, Ryan J , Jordaan, Martine , Froneman, P William , Weyl, Olaf L F
- Date: 2015
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/143247 , vital:38214 , https://doi.org/10.1371/journal.pone.0142140
- Description: Rotenone, a naturally occurring ketone, is widely employed for the management of invasive fish species. The use of rotenone poses serious challenges to conservation practitioners due to its impacts on non-target organisms including amphibians and macroinvertebrates. Using laboratory studies, we investigated the effects of different rotenone concentrations (0, 12.5, 25, 37.5, 50, 100 μg L-1) on selected invertebrate groups; Aeshnidae, Belostomatids, Decapods, Ephemeroptera, Pulmonata and zooplankton over a period of 18 hours. Based on field observations and body size, we hypothesized that Ephemeropterans and zooplankton would be more susceptible to rotenone than Decapods, Belostomatids and snails.
- Full Text:
- Date Issued: 2015
- Authors: Dalu, Tatenda , Wasserman, Ryan J , Jordaan, Martine , Froneman, P William , Weyl, Olaf L F
- Date: 2015
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/143247 , vital:38214 , https://doi.org/10.1371/journal.pone.0142140
- Description: Rotenone, a naturally occurring ketone, is widely employed for the management of invasive fish species. The use of rotenone poses serious challenges to conservation practitioners due to its impacts on non-target organisms including amphibians and macroinvertebrates. Using laboratory studies, we investigated the effects of different rotenone concentrations (0, 12.5, 25, 37.5, 50, 100 μg L-1) on selected invertebrate groups; Aeshnidae, Belostomatids, Decapods, Ephemeroptera, Pulmonata and zooplankton over a period of 18 hours. Based on field observations and body size, we hypothesized that Ephemeropterans and zooplankton would be more susceptible to rotenone than Decapods, Belostomatids and snails.
- Full Text:
- Date Issued: 2015
- «
- ‹
- 1
- ›
- »