Connectivity through allochthony: Reciprocal links between adjacent aquatic and terrestrial ecosystems in South Africa
- Richoux, Nicole B, Moyo, Sydney, Chari, Lenin D, Bergamino, Leandro, Carassou, Laure, Dalu, Tatenda, Hean, Jeffrey W, Sikutshwa, Likho, Gininda, Simphiwe, Magoro, Mandla L, Perhar, Gurbir, Ni, Felicity, Villet, Martin H, Whitfield, Alan K, Parker, Daniel M, Froneman, P William, Arhonditsis, George, Craig, Adrian J F K
- Authors: Richoux, Nicole B , Moyo, Sydney , Chari, Lenin D , Bergamino, Leandro , Carassou, Laure , Dalu, Tatenda , Hean, Jeffrey W , Sikutshwa, Likho , Gininda, Simphiwe , Magoro, Mandla L , Perhar, Gurbir , Ni, Felicity , Villet, Martin H , Whitfield, Alan K , Parker, Daniel M , Froneman, P William , Arhonditsis, George , Craig, Adrian J F K
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , report
- Identifier: http://hdl.handle.net/10962/438363 , vital:73454 , ISBN 978-1-4312-0679-7 , https://wrcwebsite.azurewebsites.net/wp-content/uploads/mdocs/2186-1-15.pdf
- Description: An important aspect of the dynamics of nutrients and pollutants in natural systems is captured in the concept of allochthony, founded on the observation that nutrients and energy in a variety of forms are transferred between adjacent habitats, com-munities and ecosystems that are not routinely considered as connected. Different forms of nutrients and energy move across the conceptual boundaries of habitats via organisms’ activities or physical processes such as wind or water currents, and these transfers can represent important food subsidies. Such cross-partition ecolog-ical subsidies can augment the nutritional condition, biomass and biodiversity of communities, particularly where local production (or autochthony) alone may be inadequate to support local food webs. Furthermore, organic subsidies can influ-ence population dynamics, community interactions and ecosystem processes, and can represent dominant flux inputs in ecosystem budgets. Our intention was to ex-plore organic nutrient fluxes in relation to a primarily lotic (i.e. flowing) aquatic sys-tem at the scale of a hydrological catchment.
- Full Text:
- Date Issued: 2015
- Authors: Richoux, Nicole B , Moyo, Sydney , Chari, Lenin D , Bergamino, Leandro , Carassou, Laure , Dalu, Tatenda , Hean, Jeffrey W , Sikutshwa, Likho , Gininda, Simphiwe , Magoro, Mandla L , Perhar, Gurbir , Ni, Felicity , Villet, Martin H , Whitfield, Alan K , Parker, Daniel M , Froneman, P William , Arhonditsis, George , Craig, Adrian J F K
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , report
- Identifier: http://hdl.handle.net/10962/438363 , vital:73454 , ISBN 978-1-4312-0679-7 , https://wrcwebsite.azurewebsites.net/wp-content/uploads/mdocs/2186-1-15.pdf
- Description: An important aspect of the dynamics of nutrients and pollutants in natural systems is captured in the concept of allochthony, founded on the observation that nutrients and energy in a variety of forms are transferred between adjacent habitats, com-munities and ecosystems that are not routinely considered as connected. Different forms of nutrients and energy move across the conceptual boundaries of habitats via organisms’ activities or physical processes such as wind or water currents, and these transfers can represent important food subsidies. Such cross-partition ecolog-ical subsidies can augment the nutritional condition, biomass and biodiversity of communities, particularly where local production (or autochthony) alone may be inadequate to support local food webs. Furthermore, organic subsidies can influ-ence population dynamics, community interactions and ecosystem processes, and can represent dominant flux inputs in ecosystem budgets. Our intention was to ex-plore organic nutrient fluxes in relation to a primarily lotic (i.e. flowing) aquatic sys-tem at the scale of a hydrological catchment.
- Full Text:
- Date Issued: 2015
Food preferences of the estuarine crab Sesarma catenata estimated through laboratory experiments
- Bergamino, Leandro, Richoux, Nicole B
- Authors: Bergamino, Leandro , Richoux, Nicole B
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/457256 , vital:75620 , xlink:href="https://doi.org/10.1071/MF14122"
- Description: Feeding by sesarmid crabs on plants represents an important energy pathway within some estuarine ecosystems. We examined the trophic ecology of estuarine sesarmid crabs Sesarma catenata through a series of laboratory feeding-preference experiments. Our experiments considered decomposed and mature leaves of terrestrial riparian trees, marsh plants Chenolea diffusa and Sarcocornia perennis and the marshgrass Spartina maritima as potential food items. S. catenata preferred decomposed leaves of terrestrial riparian trees, followed by decomposed and mature leaves of S. maritima. We suggest that the low carbon:nitrogen (C:N) ratios of S. maritima and high bacterial production associated with decomposed terrestrial leaves may explain the trophic behaviour of S. catenata. The faecal production by S. catenata during these experiments confirmed the preferential assimilation of decomposed material by the crabs. By combining the consumption rates with an estimated density of S. catenata within the local estuary that it inhabits, we suggest that moderate proportions of the leaf material can potentially be consumed by this species (34% of total leaf litter), leaving substantial amounts of unconsumed leaf litter that may represent an important subsidy for adjacent environments. Our results validate previously published trophic data, showing the value of linking feeding experiments with biological tracers to improve food-web models.
- Full Text:
- Date Issued: 2015
- Authors: Bergamino, Leandro , Richoux, Nicole B
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/457256 , vital:75620 , xlink:href="https://doi.org/10.1071/MF14122"
- Description: Feeding by sesarmid crabs on plants represents an important energy pathway within some estuarine ecosystems. We examined the trophic ecology of estuarine sesarmid crabs Sesarma catenata through a series of laboratory feeding-preference experiments. Our experiments considered decomposed and mature leaves of terrestrial riparian trees, marsh plants Chenolea diffusa and Sarcocornia perennis and the marshgrass Spartina maritima as potential food items. S. catenata preferred decomposed leaves of terrestrial riparian trees, followed by decomposed and mature leaves of S. maritima. We suggest that the low carbon:nitrogen (C:N) ratios of S. maritima and high bacterial production associated with decomposed terrestrial leaves may explain the trophic behaviour of S. catenata. The faecal production by S. catenata during these experiments confirmed the preferential assimilation of decomposed material by the crabs. By combining the consumption rates with an estimated density of S. catenata within the local estuary that it inhabits, we suggest that moderate proportions of the leaf material can potentially be consumed by this species (34% of total leaf litter), leaving substantial amounts of unconsumed leaf litter that may represent an important subsidy for adjacent environments. Our results validate previously published trophic data, showing the value of linking feeding experiments with biological tracers to improve food-web models.
- Full Text:
- Date Issued: 2015
Spatial and temporal changes in estuarine food web structure: differential contributions of marsh grass detritus
- Bergamino, Leandro, Richoux, Nicole B
- Authors: Bergamino, Leandro , Richoux, Nicole B
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/457295 , vital:75623 , xlink:href="https://doi.org/10.1007/s12237-014-9814-5"
- Description: We measured stable isotope signatures and fatty acid profiles in dominant consumers and basal food sources to assess spatial and temporal changes in the trophic structure within an estuarine ecosystem. The consumers analyzed included zooplankton, benthic invertebrates and fishes from the upper, middle and lower reaches of the estuary collected over four seasons. The contributions of different food sources to the consumers were assessed using the isotopic mixing model stable isotope analysis in R (SIAR). Our stable isotope and fatty acid data indicated that the food webs differed significantly among reaches and seasons within the estuary. Benthic invertebrates exhibited lower carbon isotopic (δ13C) values in the upper reaches of the estuary during all seasons, with lowest values occurring during autumn. In contrast, nitrogen isotopic (δ15N) values of consumers were higher in the upper reaches of the estuary and were highest during summer and spring. SIAR models and fatty acid compositional data both indicated greater utilization of marsh grass by consumers inhabiting the lower reaches of the estuary, particularly during autumn and winter. Our data indicated that differential inputs of detritus contributed to spatial changes in the benthic estuarine food web structure and that the trends changed throughout the year.
- Full Text:
- Date Issued: 2015
- Authors: Bergamino, Leandro , Richoux, Nicole B
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/457295 , vital:75623 , xlink:href="https://doi.org/10.1007/s12237-014-9814-5"
- Description: We measured stable isotope signatures and fatty acid profiles in dominant consumers and basal food sources to assess spatial and temporal changes in the trophic structure within an estuarine ecosystem. The consumers analyzed included zooplankton, benthic invertebrates and fishes from the upper, middle and lower reaches of the estuary collected over four seasons. The contributions of different food sources to the consumers were assessed using the isotopic mixing model stable isotope analysis in R (SIAR). Our stable isotope and fatty acid data indicated that the food webs differed significantly among reaches and seasons within the estuary. Benthic invertebrates exhibited lower carbon isotopic (δ13C) values in the upper reaches of the estuary during all seasons, with lowest values occurring during autumn. In contrast, nitrogen isotopic (δ15N) values of consumers were higher in the upper reaches of the estuary and were highest during summer and spring. SIAR models and fatty acid compositional data both indicated greater utilization of marsh grass by consumers inhabiting the lower reaches of the estuary, particularly during autumn and winter. Our data indicated that differential inputs of detritus contributed to spatial changes in the benthic estuarine food web structure and that the trends changed throughout the year.
- Full Text:
- Date Issued: 2015
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