Trends in tuna carbon isotopes suggest global changes in pelagic phytoplankton communities

Lorrain, Anne; Pethybridge, Heidi; Cassar, Nicolas; Receveur, Aurore; Allain, Valérie; Bodin, Nathalie; Bopp, Laurent; Choy, C. Anela; Duffy, Leanne M.; Fry, Brian; Goñi, Nicolás; Graham, Brittany; Hobday, Alistair J.; Logan, John M.; Ménard, Frédéric; Menkès, Christophe E.; Olson, Robert J.; Pagendam, Dan; Point, David; Revill, Andrew T.; Somes, Christopher J.; Young, Jock

doi:10.1111/gcb.14858

Cited by 56 publications

(54 citation statements)

References 71 publications

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“…However, these studies have shown a small magnitude of change in δ 13 C (e.g. −1.4‰ from 2004 to 2017 for elephant seals in Mestre et al, 2020; and −1.8‰ for three tuna species from 2000 to 2015 in Lorrain et al, 2020) in the direction of the Suess effect, compared with the mean increase in δ 13 C we present for South African SRWs from −23.76 ‰ in the 1990s to −20.98 ‰ in the 2010 (i.e. +2.78 ‰).…”

Section: Discussionmentioning

confidence: 95%

“…Disentangling whether a change in a consumer's stable isotope values represents a shift in foraging behaviour or a shift in isotopic baseline is challenging (McMahon et al, 2013b). However, the increase in δ 13 C in South African SRWs is unlikely to be due to ecosystem baseline changes, as it is both substantial and in the opposite direction to the general trend of decreases in oceanic baseline 13 C values (de la Vega et al, 2019;Hanson et al, 2009;Lorrain et al, 2020;Mestre et al, 2020;Newsome, Etnier, et al, 2007).…”

Section: Caveatsmentioning

confidence: 99%

“…As a result, several studies have detected decreases in marine predator δ 13 C values that could not be attributed to shifts in foraging strategies, but rather to changes in abiotic conditions and/ or other biotic components of the Southern Ocean (i.e. Suess effect or changes in biological productivity; de la Vega et al, 2019;Hanson et al, 2009;Lorrain et al, 2020;Mestre et al, 2020;Newsome, Etnier, et al, 2007;Quillfeldt et al, 2010). However, these studies have shown a small magnitude of change in δ 13 C (e.g.…”

Section: Caveatsmentioning

confidence: 99%

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Decadal shift in foraging strategy of a migratory southern ocean predator

Berg

Vermeulen

Valenzuela

et al. 2020

Global Change Biology

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Rapid anthropogenic environmental change is expected to impact a host of ecological parameters in Southern Ocean ecosystems. Of critical concern are the consequences of these changes on the range of species that show fidelity to migratory destinations, as philopatry is hypothesized to help or hinder adaptation to climate change depending on the circumstances. Many baleen whales show philopatry to feeding grounds and are also capital breeders that meet migratory and reproductive costs through seasonal energy intake. Southern right whales (Eubalaena australis, SRWs) are capital breeders that have a strong relationship between reproductive output and foraging success. The population dynamics of South Africa's population of SRWs are characterized by two distinct periods: the 1990s, a period of high calving rates; and the late 2010s, a period associated with lowered calving rates. Here we use analyses of stable carbon (δ13C) and nitrogen (δ15N) isotope values from SRW biopsy samples (n = 122) collected during these two distinct periods to investigate foraging ecology of the South African population of SRWs over a time period coincident with the demographic shift. We show that South African SRWs underwent a dramatic northward shift, and diversification, in foraging strategy from 1990s to 2010s. Bayesian mixing model results suggest that during the 1990s, South African SRWs foraged on prey isotopically similar to South Georgia/Islas Georgias del Sur krill. In contrast, in the 2010s, South African SRWs foraged on prey isotopically consistent with the waters of the Subtropical Convergence, Polar Front and Marion Island. We hypothesize that this shift represents a response to changes in preferred habitat or prey, for example, the decrease in abundance and southward range contraction of Antarctic krill. By linking reproductive decline to changing foraging strategies for the first time in SRWs, we show that altering foraging strategies may not be sufficient to adapt to a changing ocean.

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Section: Discussionmentioning

confidence: 95%

Section: Caveatsmentioning

confidence: 99%

Section: Caveatsmentioning

confidence: 99%

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Decadal shift in foraging strategy of a migratory southern ocean predator

Berg

Vermeulen

Valenzuela

et al. 2020

Global Change Biology

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“…Variation in the regional isotopic composition of baseline producers, or isoscapes, occurs due to nutrient input, dominating phytoplanktonic composition, and oceanographic conditions (McMahon et al 2013, Magozzi et al 2017, Lorrain et al 2019), and precludes the direct comparison of raw δ 13 C and δ 15 N between skate assemblages (Manlick et al 2019). Therefore, we calculated region‐specific estimates of trophic position (TP) using the R package tRophicPosition (Quezada‐Romegialli et al 2018).…”

Section: Methodsmentioning

confidence: 99%

Evolution of realized Eltonian niches acrossRajidaespecies

et al. 2021

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The notion that closely related species resemble each other in ecological niche space (i.e., phylogenetic dependence) has been a long‐standing, contentious paradigm in evolutionary biology, the incidence of which is important for predicting the ecosystem‐level effects of species loss. Despite being examined across a multitude of terrestrial taxa, many aspects of niche conservatism have yet to be explored in marine species, especially for characteristics related to resource use and trophic behavior (Eltonian niche characteristics, ENCs). We combined ENCs derived from stable isotope ratios at assemblage‐ and species‐levels with phylogenetic comparative methods, to test the hypotheses that benthic marine fishes (1) exhibit similar assemblage‐wide ENCs regardless of geographic location and (2) display phylogenetically dependent ENCs at the species level. We used a 12‐species sub‐set of the monophyletic group Rajidae sampled from three independent assemblages (Central California, Gulf of Alaska, and Northwest Atlantic), which span two ocean basins. Assemblage‐level ENCs implied low trophic diversity and high evenness, suggesting that Rajidae assemblages may exhibit a well‐defined trophic role, a trend consistent regardless of geographic location. At the species level, we found evidence for phylogenetic dependence of ENCs relating to trophic diversity (i.e., isotopic niche width; SEAc). Whether individuals can be considered functional equivalents across assemblages is hard to ascertain because we did not detect a significant phylogenetic signal for ENCs relating to trophic function (e.g., trophic position). Thus, additional, complimentary approaches are required to further examine the phylogenetic dependence of species functionality. Our approach illustrates the potential of stable isotope‐derived niche characteristics to provide insight on macroecological processes occurring across evolutionary time, which could help predict how assemblages may respond to the effects of species loss.

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“…Functional trait-based diversity of phytoplankton is mostly unexplored throughout the ocean, even though this approach (functional trait diversity) gives ecological information about species in changing environments (stratification, nutrient availability, cell size, and community structure) (Lorrain et al, 2019;Tuerena et al, 2019). Global climate change may favor opportunistic plankton species (e.g., Van de Waal and Litchman, 2020).…”

Section: Introductionmentioning

confidence: 99%

Is Oligotrophy an Equalizing Factor Driving Microplankton Species Functional Diversity Within Agulhas Rings?

et al. 2020

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From the southwestern termination of the Agulhas current, anticyclonic eddies are emitted and drift across the South Atlantic Ocean. This study is based on a FORSA (Following Ocean Rings in the South Atlantic) oceanographic cruise, from Cape Town (South AFRica) to Arraial do Cabo (Brazil) in June 2015, during which three eddies of different ages (E1, 7 months; E3, 11 months; E5, 24 months) from the Agulhas current were sampled for microplankton identification and determination of functional traits. The stations where sampling occurred at each eddy included a control outside the eddy and three stations inside the eddy—border, midway (between the border and center), and center (identified through satellite images of sea level anomaly—SLA). Functional traits were determined based on microscopic observations and consultation of the literature. An evident decay in the Agulhas eddies toward the west was observed, and each eddy proved to be different. E1 represented a younger and more robust structure. At the same time, the other eddies, E3 and E5, were more alike with similar physical, chemical, and ecological characteristics and almost the same indices values of functional diversity, demonstrating that although their species compositions were different, the strategies used by the species were the same. The most crucial ecological trait for microplankton was nutrition mode. The microplankton contained mainly mixotrophic dinoflagellates and cyanobacteria adapted to oligotrophic conditions. The functional strategy of microplankton did not differ among the eddies and stations, with mixotrophy being the most striking trait. Therefore, the older eddies’ microplankton community fits the neutrality theory, whereby species perform similar ecological functions, and the younger eddy fits in the niche complementarity. Even with the species composition being different in each eddy and/or within the same eddy, the functional strategy was the same, with scarce resources and species selected that best use any source of nutrients or use evolutionary advantages to live in an oligotrophic environment.

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Trends in tuna carbon isotopes suggest global changes in pelagic phytoplankton communities

Cited by 56 publications

References 71 publications

Decadal shift in foraging strategy of a migratory southern ocean predator

Decadal shift in foraging strategy of a migratory southern ocean predator

Evolution of realized Eltonian niches acrossRajidaespecies

Is Oligotrophy an Equalizing Factor Driving Microplankton Species Functional Diversity Within Agulhas Rings?

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