Habitat complexity alters predator-prey interactions in a shallow water ecosystem
- Froneman, P William, Cuthbert, Ross N
- Authors: Froneman, P William , Cuthbert, Ross N
- Date: 2022
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/479242 , vital:78277 , https://doi.org/10.3390/d14060431
- Description: Habitat complexity can profoundly influence interactions between predators and their prey due to changes to foraging efficiencies. In aquatic systems, habitat alterations can alter pursuit times and swimming behaviours of predator–prey participants, which in turn could mediate the strength of their interactions and, thus, population dynamics. The lower reaches of estuarine ecosystems are typically characterised by extensive beds of submerged macrophytes that might influence the trophic dynamics between pelagic predators and their prey. Here, we investigate the influence of increasing habitat complexity on the consumption of the calanoid copepod, Paracartia longipatella, by adult male and female mysid, Mesopodopsis wooldridgei, by means of a comparative functional response approach. Using structures that resembled aquatic vegetation, we quantified and compared feeding rates, attack rates, and handling times across the habitat gradient, and we questioned whether responses to habitat complexity are different between sexes. Feeding rates related significantly negatively to increasing habitat complexity for both males and females, with Type II functional responses consistently displayed. Functional response differed significantly across habitat complexities, with feeding rates at low and intermediate prey densities significantly greater in the absence of habitat compared to more complex structures for both predator sexes. Results of the current study demonstrate that increased habitat complexity mediates outcomes of interactions between M. wooldridgei and the calanoid copepod, P. longipatella across predator sexes, and possibly for other predators and prey in shallow waters. Owing to spatiotemporal differences in habitat structure within shallow waters, the strength of interactions in this predator–prey system likely differs in areas where they co-exist.
- Full Text:
- Date Issued: 2022
- Authors: Froneman, P William , Cuthbert, Ross N
- Date: 2022
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/479242 , vital:78277 , https://doi.org/10.3390/d14060431
- Description: Habitat complexity can profoundly influence interactions between predators and their prey due to changes to foraging efficiencies. In aquatic systems, habitat alterations can alter pursuit times and swimming behaviours of predator–prey participants, which in turn could mediate the strength of their interactions and, thus, population dynamics. The lower reaches of estuarine ecosystems are typically characterised by extensive beds of submerged macrophytes that might influence the trophic dynamics between pelagic predators and their prey. Here, we investigate the influence of increasing habitat complexity on the consumption of the calanoid copepod, Paracartia longipatella, by adult male and female mysid, Mesopodopsis wooldridgei, by means of a comparative functional response approach. Using structures that resembled aquatic vegetation, we quantified and compared feeding rates, attack rates, and handling times across the habitat gradient, and we questioned whether responses to habitat complexity are different between sexes. Feeding rates related significantly negatively to increasing habitat complexity for both males and females, with Type II functional responses consistently displayed. Functional response differed significantly across habitat complexities, with feeding rates at low and intermediate prey densities significantly greater in the absence of habitat compared to more complex structures for both predator sexes. Results of the current study demonstrate that increased habitat complexity mediates outcomes of interactions between M. wooldridgei and the calanoid copepod, P. longipatella across predator sexes, and possibly for other predators and prey in shallow waters. Owing to spatiotemporal differences in habitat structure within shallow waters, the strength of interactions in this predator–prey system likely differs in areas where they co-exist.
- Full Text:
- Date Issued: 2022
Inter-and intra-specific trophic interactions of coastal delphinids off the eastern coast of South Africa inferred from stable isotope analysis
- Caputo, Michelle, Bouveroux, Thibaut N, Van der Bank, Megan, Cliff, Geremy, Kiszka, Jeremy J, Froneman, P William, Plön, Stephanie
- Authors: Caputo, Michelle , Bouveroux, Thibaut N , Van der Bank, Megan , Cliff, Geremy , Kiszka, Jeremy J , Froneman, P William , Plön, Stephanie
- Date: 2022
- Subjects: To be catalogued
- Language: English
- Type: article
- Identifier: http://hdl.handle.net/10962/466545 , vital:76745 , https://doi.org/10.1016/j.marenvres.2022.105784
- Description: Dietary tracers, such as bulk stable carbon (δ13C) and nitrogen (δ15N) isotopes, can be used to investigate the trophic interactions of marine predators, which is useful to assess their ecological roles within communities. These tracers have also been used to elucidate population structure and substructure, which is critical for the better identification of management units for these species affected by a range of threats, particularly bycatch in fishing gears. Off eastern South Africa, large populations of Indo-Pacific bottlenose (Tursiops aduncus) and common dolphins (Delphinus delphis) co-occur and are thought to follow the pulses of shoaling sardines (Sardinops sagax) heading north-east in the austral winter. Here we used δ13C and δ15N to investigate the trophic interactions and define ecological units of these two species along a ≈800 km stretch of the east coast of South Africa, from Algoa Bay to the coast of KwaZulu-Natal. Common and bottlenose dolphin dietary niche overlapped by 39.7% overall in our study area, with the highest overlap occurring off the Wild Coast (40.7% at Hluleka).
- Full Text:
- Date Issued: 2022
- Authors: Caputo, Michelle , Bouveroux, Thibaut N , Van der Bank, Megan , Cliff, Geremy , Kiszka, Jeremy J , Froneman, P William , Plön, Stephanie
- Date: 2022
- Subjects: To be catalogued
- Language: English
- Type: article
- Identifier: http://hdl.handle.net/10962/466545 , vital:76745 , https://doi.org/10.1016/j.marenvres.2022.105784
- Description: Dietary tracers, such as bulk stable carbon (δ13C) and nitrogen (δ15N) isotopes, can be used to investigate the trophic interactions of marine predators, which is useful to assess their ecological roles within communities. These tracers have also been used to elucidate population structure and substructure, which is critical for the better identification of management units for these species affected by a range of threats, particularly bycatch in fishing gears. Off eastern South Africa, large populations of Indo-Pacific bottlenose (Tursiops aduncus) and common dolphins (Delphinus delphis) co-occur and are thought to follow the pulses of shoaling sardines (Sardinops sagax) heading north-east in the austral winter. Here we used δ13C and δ15N to investigate the trophic interactions and define ecological units of these two species along a ≈800 km stretch of the east coast of South Africa, from Algoa Bay to the coast of KwaZulu-Natal. Common and bottlenose dolphin dietary niche overlapped by 39.7% overall in our study area, with the highest overlap occurring off the Wild Coast (40.7% at Hluleka).
- Full Text:
- Date Issued: 2022
Photoautotrophic euendoliths and their complex ecological effects in marine bioengineered ecosystems
- Dievart, Alexia M, McQuaid, Christopher D, Zardi, Gerardo I, Nicastro, Katy R, Froneman, P William
- Authors: Dievart, Alexia M , McQuaid, Christopher D , Zardi, Gerardo I , Nicastro, Katy R , Froneman, P William
- Date: 2022
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/479286 , vital:78283 , https://doi.org/10.3390/d14090737
- Description: Photoautotrophic euendolithic microorganisms are ubiquitous where there are calcium carbonate substrates to bore into and sufficient light to sustain photosynthesis. The most diverse and abundant modern euendolithic communities can be found in the marine environment. Euendoliths, as microorganisms infesting inanimate substrates, were first thought to be ecologically irrelevant. Over the past three decades, numerous studies have subsequently shown that euendoliths can colonize living marine calcifying organisms, such as coral skeletons and bivalve shells, causing both sub-lethal and lethal damage. Moreover, under suitable environmental conditions, their presence can have surprising benefits for the host. Thus, infestation by photoautotrophic euendoliths has significant consequences for calcifying organisms that are of particular importance in the case of ecosystems underpinned by calcifying ecosystem engineers. In this review, we address the nature and diversity of marine euendoliths, as revealed recently through genetic techniques, their bioerosive mechanisms, how environmental conditions influence their incidence in marine ecosystems and their potential as bioindicators, how they affect live calcifiers, and the potential future of euendolithic infestation in the context of global climate change and ocean acidification.
- Full Text:
- Date Issued: 2022
Photoautotrophic euendoliths and their complex ecological effects in marine bioengineered ecosystems
- Authors: Dievart, Alexia M , McQuaid, Christopher D , Zardi, Gerardo I , Nicastro, Katy R , Froneman, P William
- Date: 2022
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/479286 , vital:78283 , https://doi.org/10.3390/d14090737
- Description: Photoautotrophic euendolithic microorganisms are ubiquitous where there are calcium carbonate substrates to bore into and sufficient light to sustain photosynthesis. The most diverse and abundant modern euendolithic communities can be found in the marine environment. Euendoliths, as microorganisms infesting inanimate substrates, were first thought to be ecologically irrelevant. Over the past three decades, numerous studies have subsequently shown that euendoliths can colonize living marine calcifying organisms, such as coral skeletons and bivalve shells, causing both sub-lethal and lethal damage. Moreover, under suitable environmental conditions, their presence can have surprising benefits for the host. Thus, infestation by photoautotrophic euendoliths has significant consequences for calcifying organisms that are of particular importance in the case of ecosystems underpinned by calcifying ecosystem engineers. In this review, we address the nature and diversity of marine euendoliths, as revealed recently through genetic techniques, their bioerosive mechanisms, how environmental conditions influence their incidence in marine ecosystems and their potential as bioindicators, how they affect live calcifiers, and the potential future of euendolithic infestation in the context of global climate change and ocean acidification.
- Full Text:
- Date Issued: 2022
Predator Diversity Does Not Contribute to Increased Prey Risk: Evidence from a Mesocosm Study
- Authors: Froneman, P William
- Date: 2022
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/479319 , vital:78286 , https://doi.org/10.3390/d14080584
- Description: Predation plays an important organisational role in structuring aquatic communities. Predator diversity can, however, lead to emergent effects in which the outcomes of predator–prey interactions are modified. The importance of predator diversity in regulating predator–prey interactions was investigated during a 9-day mesocosm study conducted in the middle reach of a temporarily open/closed, temperate, southern African estuary. The zooplankton community, comprising almost exclusively (>95% of total counts) calanoid and cyclopoid copepods of the genera Pseudodiaptomus, Paracartia and Oithona, was subject to three different juvenile fish predator treatments at natural densities: 1. predation by Gilchristella aestuaria, (Gilchrist, 1913; SL 15.3 ± 2.4 mm); 2. predation by Myxus capensis (Valenciennes, 1836; SL 12.8 ± 3.7 mm); and 3. a combination of the two predators. The presence of the predators contributed to a significant decline in the total zooplankton abundances, with a concurrent increase in total chlorophyll-a (Chl-a) concentrations, consistent with the expectations of a trophic cascade (ANCOVA; p 0.05 in all cases). There were no significant differences in the total Chl-a concentration or total zooplankton abundances between the different predator treatments, suggesting that the increase in predator diversity did not contribute to increased prey risk or to the strength of the trophic cascade.
- Full Text:
- Date Issued: 2022
- Authors: Froneman, P William
- Date: 2022
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/479319 , vital:78286 , https://doi.org/10.3390/d14080584
- Description: Predation plays an important organisational role in structuring aquatic communities. Predator diversity can, however, lead to emergent effects in which the outcomes of predator–prey interactions are modified. The importance of predator diversity in regulating predator–prey interactions was investigated during a 9-day mesocosm study conducted in the middle reach of a temporarily open/closed, temperate, southern African estuary. The zooplankton community, comprising almost exclusively (>95% of total counts) calanoid and cyclopoid copepods of the genera Pseudodiaptomus, Paracartia and Oithona, was subject to three different juvenile fish predator treatments at natural densities: 1. predation by Gilchristella aestuaria, (Gilchrist, 1913; SL 15.3 ± 2.4 mm); 2. predation by Myxus capensis (Valenciennes, 1836; SL 12.8 ± 3.7 mm); and 3. a combination of the two predators. The presence of the predators contributed to a significant decline in the total zooplankton abundances, with a concurrent increase in total chlorophyll-a (Chl-a) concentrations, consistent with the expectations of a trophic cascade (ANCOVA; p 0.05 in all cases). There were no significant differences in the total Chl-a concentration or total zooplankton abundances between the different predator treatments, suggesting that the increase in predator diversity did not contribute to increased prey risk or to the strength of the trophic cascade.
- Full Text:
- Date Issued: 2022
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