Latitudinal changes in the structure of marine food webs in the Southwestern Atlantic Ocean

Saporiti, Fabiana; Bearhop, Stuart; Vales, Damián G.; Silva, L.; Zenteno, Lisette; Tavares, Maurício; Crespo, Enrique A.; Cardona, Luís

doi:10.3354/meps11464

Cited by 33 publications

(31 citation statements)

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“…Although eared seals do not eat mussels, the latter are informative about changes in the stable isotope baseline of the R ıo de la Plata ecosystem. This is because mussels are suspension feeders, and stable isotope ratios in mussels match those in particulate organic matter (POM) along the coasts of the Southwestern Atlantic Ocean (Saporiti et al 2015). Furthermore, POM of both terrestrial and estuarine/marine origin is the major source of fixed carbon for the food web in R ıo de la Plata, with a negligible contribution from benthic macrophytes because of the high water turbidity (Acha et al 2008;Botto et al 2011;Saporiti et al 2015).…”

Section: Discussionmentioning

confidence: 99%

“…This is because mussels are suspension feeders, and stable isotope ratios in mussels match those in particulate organic matter (POM) along the coasts of the Southwestern Atlantic Ocean (Saporiti et al 2015). Furthermore, POM of both terrestrial and estuarine/marine origin is the major source of fixed carbon for the food web in R ıo de la Plata, with a negligible contribution from benthic macrophytes because of the high water turbidity (Acha et al 2008;Botto et al 2011;Saporiti et al 2015). Second, although the topology of the prey community within the d 13 C-d 15 N space may have changed over time, neither the depletion in d 13 C of pelagic prey compared with demersal prey nor the increase in the d 15 N values with trophic position may have changed, since these relationships are general across ecosystems (Post 2002).…”

Section: Discussionmentioning

confidence: 99%

“…To allow comparison, original stable isotope values in the bone of both species were corrected (d 13 C cor and d 15 N cor ) in accordance with the changes in the isotopic baseline. estuary (Botto et al 2011;Marchese et al 2014;Saporiti et al 2015).…”

Section: Discussionmentioning

confidence: 99%

“…; Saporiti et al . ); therefore, differences in the diet of South American fur seals in these two regions might be because of other ecosystem attributes and deserve further research.…”

Section: Introductionmentioning

confidence: 99%

“…Such a pattern might be related to the opposite trends in size of the sympatric populations of South American sea lions in these two regions, as the sea lion population is declining in both the R ıo de la Plata and the adjoining Atlantic while increasing in northern Patagonia (Grandi et al 2012). Nevertheless, the R ıo de la Plata estuary (with the adjacent Atlantic Ocean coast) and northern Patagonia currently support very different ecosystems (Acha et al 2004;Saporiti et al 2015); therefore, differences in the diet of South American fur seals in these two regions might be because of other ecosystem attributes and deserve further research.…”

Section: Introductionmentioning

confidence: 99%

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Isotopic niche partitioning between two apex predators over time

Drago

Cardona

Franco‐Trecu

et al. 2017

Journal of Animal Ecology

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Stable isotope analyses have become an important tool in reconstructing diets, analysing resource use patterns, elucidating trophic relations among predators and understanding the structure of food webs. Here, we use stable carbon and nitrogen isotope ratios in bone collagen to reconstruct and compare the isotopic niches of adult South American fur seals (Arctocephalus australis; n = 86) and sea lions (Otaria flavescens; n = 49) - two otariid species with marked morphological differences - in the Río de la Plata estuary (Argentina - Uruguay) and the adjacent Atlantic Ocean during the second half of the 20th century and the beginning of the 21st century. Samples from the middle Holocene (n = 7 fur seals and n = 5 sea lions) are also included in order to provide a reference point for characterizing resource partitioning before major anthropogenic modifications of the environment. We found that the South American fur seals and South American sea lions had distinct isotopic niches during the middle Holocene. Isotopic niche segregation was similar at the beginning of the second half of the 20th century, but has diminished over time. The progressive convergence of the isotopic niches of these two otariids during the second half of the 20th century and the beginning of the 21st century is most likely due to the increased reliance of South American fur seals on demersal prey. This recent dietary change in South American fur seals can be explained by at least two non-mutually exclusive mechanisms: (i) the decrease in the abundance of sympatric South American sea lions as a consequence of small colony size and high pup mortality resulting from commercial sealing; and (ii) the decrease in the average size of demersal fishes due to intense fishing of the larger class sizes, which may have increased their accessibility to those eared seals with a smaller mouth gape, that is, South American fur seals of both sexes and female South American sea lions.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

“…; Saporiti et al . ); therefore, differences in the diet of South American fur seals in these two regions might be because of other ecosystem attributes and deserve further research.…”

Section: Introductionmentioning

confidence: 99%