Spatial characterisation of the Benguela ecosystem for ecosystem-based management

Kirkman, SP; Blamey, Laura K.; Lamont, Tarron; Field, J. G.; Bianchi, G.; Huggett, Jenny A.; Hutchings, L.; Jackson-Veitch, J; Jarre, Astrid; Lett, Christophe; Lipiński,; Mafwila, SW; Pfaff, Maya C.; Samaai, Toufiek; Shannon, Lynne J.; Shin, Yun Ji; Lingen, CD van der; Yemane, Dawit

doi:10.2989/1814232x.2015.1125390

Cited by 43 publications

(29 citation statements)

References 55 publications

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“…Nevertheless, these ocean color observations, together with the application of models to assess variations in size structure, as presented in this study, among others (Brewin et al, , ; Hirata et al, ; Lamont, Barlow, et al, ; Lamont, Brewin, et al, ) provide new data sets which afford the opportunity for more detailed investigations of phytoplankton communities, as well as their responses to climate change and variation. Since phytoplankton communities form the base of marine ecosystems (Chassot et al, ; Field et al, ; Sathyendranath et al, ), such as the highly productive BUS which supports large fisheries and other ecosystem goods and services of substantial economic value (Kirkman et al, ; Verheye et al, ), understanding and monitoring variations in phytoplankton biomass and community structure is crucial to evaluating the functioning and health status of these ecosystems. To adequately monitor and understand ecosystem variability and change, long‐term data sets are essential.…”

Section: Discussionmentioning

confidence: 99%

“…Standard monthly averaged SeaWiFS (NASA Goddard Space Flight Center et al, ) and MODIS‐Aqua Chla concentrations (NASA Goddard Space Flight Center et al, ), with a spatial resolution of 9 km, for the 1997–2018 period, were used to generate seasonal means of Chla and the fractional contributions of microphytoplankton, nanophytoplankton, and picophytoplankton in three regions of the BUS, namely, the NB, SB, and AB (Figure ). These regions were delineated on the basis of spatial variations in physical driving forces, biological responses, and trophic structuring (Hutchings et al, ; Kirkman et al, ). SeaWiFS data for the period from September 1997 to December 2007 were used, while MODIS‐Aqua data covered the period from July 2002 to February 2018.…”

Section: Methodsmentioning

confidence: 99%

“…Detailed reviews of the influence of large‐scale modes of variability in these systems have been presented by Shillington et al () and Reason et al (), among others. South of South Africa, the Agulhas Bank (AB; Figure ) is ecologically and economically important since it comprises the major spawning grounds for numerous fish species which recruit to the west coast (Hutchings et al, ; Kirkman et al, ). Large‐scale climate modes, such as El Niño Southern Oscillation and the Antarctic Annual Oscillation, are known to impact these regions, but their effects are not always clearly discernible (Reason et al, ; Rouault et al, ).…”

Section: Introductionmentioning

confidence: 99%

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Long‐Term Trends in Phytoplankton Chlorophyll a and Size Structure in the Benguela Upwelling System

2019

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The Benguela Upwelling System (BUS) is among the most productive ecosystems globally, supporting numerous fisheries and ecosystem services in Southern Africa. Sea‐viewing Wide Field‐of‐view Sensor and Moderate‐resolution Imaging Spectroradiometer‐Aqua chlorophyll a (Chla) concentrations between September 1997 and February 2018 were used to investigate long‐term trends in phytoplankton biomass and size structure (microphytoplankton [>20 μm], nanophytoplankton [2–20 μm], and picophytoplankton [<2 μm]) in the Northern Benguela, Southern Benguela (SB), and Agulhas Bank (AB) shelf and open ocean regions of the BUS. Trends in upwelling and correlations with Chla and size structure were examined. Increasing Chla and microphytoplankton trends occurred in the Northern Benguela shelf and open ocean, while decreases were evident on the SB shelf in all seasons. In the SB open ocean, small increases occurred during austral winter, with a decrease in spring. On the AB shelf, increases in Chla and microphytoplankton occurred in summer with decreases during the other seasons. Patterns differed in the AB open ocean, with increases in winter and spring and decreases in summer and autumn. Although R2 values indicated that linear trends accounted for a reasonable portion of the variance, and most trends were statistically significant, they showed only small changes on the shelf domains and little to no change in the open ocean. Strong correlations between upwelling, Chla, and the size classes were observed, but distinct seasonal differences occurred in each region. This is the first 20‐year analysis of phytoplankton biomass and community structure in the BUS and provides a baseline against which future changes can be monitored.

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Section: Discussionmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Long‐Term Trends in Phytoplankton Chlorophyll a and Size Structure in the Benguela Upwelling System

2019

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“…The existence of the three morphological domains listed above necessitates further revision of the existing life cycle, taking into consideration temporal and spatial scales, as well as the fine-scale oceanography of the region. The morphological differences coincide with major oceanographic features of southern African waters (eastern and central Agulhas Bank -Agulhas Current; western Agulhas Bank and west coast of South Africa -Benguela Current; southern Angola -Angola Current), which are summarised inKirkman et al (2016). The new revised life-cycle scheme for chokka-squid is presented inFigures 3 and 4.…”

mentioning

confidence: 81%

“…in beaks or statoliths) and ultimately stable genetic differences ( component of this metapopulation is not isolated genetic ally from the more southerly components, but differs morphologically. Given that mixing with the nearest abundant group (St Helena Bay to western Agulhas Bank) is minimal, because of the scarcity of individuals over nearly 1 800 km of coastline between St Helena Bay and the Cunene River mouth (where existing barriers include the Orange River outwelling, the Lüderitz upwelling cell and hypoxic water off the Namibian coast, features that are described in Kirkman et al [2016] and references therein), the Angolan subpopulation is likely to represent a recent extension of the species' range northwards and might have its own breeding and paralarval transport regime. Morphological differences between the West Coast/western Agulhas Bank and eastern Agulhas Bank/Plettenberg Bay-Port Alfred are maintained throughout by two different paralarval pools, which are further divided into smaller groups.…”

Section: Proposed New Life-cycle Scheme For Chokka-squidmentioning

confidence: 99%

Life cycle of chokka-squidLoligo reynaudiiin South African waters

Lipiński

Vyver

Shaw

et al. 2016

African Journal of Marine Science

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Geographical, temporal, and individual‐based differences in the trophic ecology of female Cape fur seals

Botha

Trueman

Kirkman

et al. 2023

Ecology and Evolution

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Information on resource use and trophic dynamics of marine predators is important for understanding their role in ecosystem functioning and predicting population‐level responses to environmental change. Where separate populations experience different local environmental conditions, geographic variability in their foraging ecology is often expected. Within populations, individuals also vary in morphology, physiology, and experience, resulting in specialization in resource use. In this context, isotopic compositions of incrementally grown tissues such as keratinous hairs offer a valuable opportunity to study long‐term variation in resource and habitat use. We investigated the trophic ecology of female Cape fur seals ( Arctocephalus pusillus pusillus ) using carbon and nitrogen isotopic compositions of serially sampled whiskers collected at four breeding sites along the coast of South Africa. Drawing on over 900 isotopic measurements, we assessed geographic variability in isotopic niche width between colonies and the degree of individual specialization. We found slight, but clear geographic differences in isotopic ratios and isotopic niche widths, seemingly related to ecological setting, with niche widths being proportional to the area of available shelf and shelf‐slope habitat surrounding the colony. We further identified periodic oscillations in isotopic ratios, which likely reflect temporal patterns in foraging distribution and prey type, linked to shifts in the availability of prey resources and their interaction with constraints on individual females throughout their breeding cycle. Finally, individual specialization indices revealed that each of the study populations contain specialist individuals that utilize only a small subset of the total population niche width. The degree of individual specialization was, however, not consistent across colonies and may reflect an interactive influence between density‐dependent effects and habitat heterogeneity. Overall, this study provides important information on the trophic ecology of Cape fur seals breeding in South Africa and highlights the need to consider geographic and individual variability when assessing the foraging ecology of marine predators.

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Spatial characterisation of the Benguela ecosystem for ecosystem-based management

Cited by 43 publications

References 55 publications

Long‐Term Trends in Phytoplankton Chlorophyll a and Size Structure in the Benguela Upwelling System

Long‐Term Trends in Phytoplankton Chlorophyll a and Size Structure in the Benguela Upwelling System

Life cycle of chokka-squidLoligo reynaudiiin South African waters

Geographical, temporal, and individual‐based differences in the trophic ecology of female Cape fur seals

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