Dissipation of seabird‐derived nutrients in a terrestrial insular trophic web

Gaiotto, Juliana Vallim; Nunes, Guilherme Tavares; Bugoni, Leandro

doi:10.1111/aec.13196

Cited by 7 publications

(5 citation statements)

References 59 publications

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“…Sampling soils within the seabird colony resulted in soil samples mixed with dry guano that had apparently not yet been mineralized, which therefore could explain the lower δ 15 N in soils observed in colony sites, especially on Santa B arbara Island. This must have had a larger impact on our results because none of the control areas were truly free of seabird influence, whereas it seems that, in some other studies (e.g., Caut et al, 2012;Gaiotto et al, 2022), sampling conditions allowed a clearer distinction of areas with and without seabird influence.…”

Section: Effects Of Seabirds On the Terrestrial Food Webmentioning

confidence: 83%

Seabirds subsidize terrestrial food webs and coral reefs in a tropical rat‐invaded archipelago

Linhares

Bugoni

2022

Ecological Applications

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Allochthonous resource fluxes mediated by organisms crossing ecosystem boundaries may be essential for supporting the structure and function of resource‐limited environments, such as tropical islands and surrounding coral reefs. However, invasive species, such as black rats, thrive on tropical islands and disrupt the natural pathways of nutrient subsidies by reducing seabird colonies. Here, we used stable isotopes of nitrogen and carbon to examine the role of seabirds in subsidizing the terrestrial food webs and adjacent coral reefs in the Abrolhos Archipelago, Southwest Atlantic Ocean. By sampling invasive rats and multiple ecosystem compartments (soil, plants, grasshoppers, tarantulas, and lizards) within and outside seabird colonies, we showed that seabird subsidies led to an overall enrichment in 15N across the food web on islands. However, contrary to other studies, δ15N values were consistently lower within the seabird colonies, suggesting that a higher seabird presence might produce a localized depletion in 15N in small islands influenced by seabirds. In contrast, the nitrogen content (%N) in plants and soils was higher inside the colonies, corresponding to a higher effect of seabirds at the base of the trophic web. Among consumers, lizards and invasive rats seemed to obtain allochthonous resources from subsidized terrestrial organisms outside the colony. Inside the colony, however, they showed a more direct consumption of marine matter, suggesting that subsidies benefit these native and invasive animals both directly and indirectly. Nonetheless, in coral reefs, scleractinian corals assimilated seabird‐derived nitrogen only around the two smaller and lower‐elevation islands, as demonstrated by the substantially higher δ15N values in relation to the reference areas. This provides evidence that island morphology may influence the incorporation of seabird nutrients in coral reefs around rat‐invaded islands, likely because guano lixiviation toward seawater is facilitated in small and low‐elevation terrains. Overall, these results showed that seabirds affected small islands across all trophic levels within and outside colonies and that these effects spread outward to coral reefs, evidencing resiliency of seabird subsidies even within a rat‐invaded archipelago. Because rats are consumers of seabird chicks and eggs, however, rat eradication could potentially benefit the terrestrial and nearshore ecosystems through increased subsides carried by seabirds.

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Section: Effects Of Seabirds On the Terrestrial Food Webmentioning

confidence: 83%

Seabirds subsidize terrestrial food webs and coral reefs in a tropical rat‐invaded archipelago

Linhares

Bugoni

2022

Ecological Applications

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“…Although both seabird colonies had higher soil nutrient concentrations than the control site, soil macro‐ and inorganic nutrient levels were higher in the tern colony than in the red‐footed booby colony. This is linked to the higher nest density of terns (Table S1) but it may also be influenced by the terns being ground‐nesters, in contrast to the tree‐nesting habits of red‐footed boobies (Gaiotto et al., 2022). Furthermore, the red‐footed booby colony's presence on South Island is relatively recent (ICS, unpublished data), in contrast to the long‐established tern colony, where nutrients have accumulated over several decades.…”

Section: Discussionmentioning

confidence: 99%

“…but it may also be influenced by the terns being ground-nesters, in contrast to the tree-nesting habits of red-footed boobies (Gaiotto et al, 2022). Furthermore, the red-footed booby colony's presence on South Island is relatively recent (ICS, unpublished data), in contrast to the long-established tern colony, where nutrients have accumulated over several decades.…”

Section: Nutrient Levels In Terrestrial and Nearshore Habitatsmentioning

confidence: 99%

Seabird presence and seasonality influence nutrient dynamics of atoll habitats

Appoo,

Bunbury,

Letori

et al. 2024

Biotropica

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Marine nutrients underpin productivity and functioning of oceanic island ecosystems. On islands where they nest, seabirds represent a primary source of marine nutrients. In tropical regions, some of the largest seabird populations nest on atolls, yet there is limited information available on seabird contributions to atoll ecosystem nutrient dynamics. To investigate the spatial and seasonal dynamics of seabird contributions, we assessed seabird colonies of different taxa, including red‐footed boobies and terns, nesting on separate islands of Farquhar Atoll, Seychelles. We assessed nutrient concentrations of guano, soil, coastal plants, and nearby seagrass in seabird colonies and at a control island with no seabirds, during the wet and dry seasons. Sooty terns contributed the highest quantities of nutrients, estimated at 71.2 N tonne/year and 52.2 P tonne/year. Seabird‐derived nutrient transfer occurred year‐round from seabird colonies to soil, coastal plants and seagrass. Soil macro‐ and inorganic nutrients were higher in the high‐density tern colony and during the dry season, coinciding with the breeding period of sooty terns. Both red‐footed booby and tern colonies maintained high nitrogen levels in coastal plants year‐round, while phosphorus levels did not differ between islands or seasons. Seabird‐derived nitrogen reversed nitrogen limitation of seagrass during the dry season. We provide the first insights into seabird nutrient contributions to atoll ecosystems in Seychelles, with recommendations for seabird conservation to boost and support atoll and island ecosystem resilience. Our results from a relatively undisturbed atoll serve as a baseline with which more impacted atolls and future changes can be assessed.

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“…This is linked to the higher nest density of terns (Table S1) and nesting location (Smith et al, 2011). Nutrients from tree-nesters, like red-footed boobies, are more sparsely distributed and less likely to reach the soil compared to ground-nesters (Gaiotto et al, 2022). Furthermore, the red-footed booby colony’s presence on South Island is relatively recent (ICS, unpubl.…”

Section: Discussionmentioning

confidence: 99%

Seabird traits and seasonality modulate nutrient dynamics of terrestrial and marine habitats on atolls

Appoo,

Bunbury,

Letori

et al. 2023

Preprint

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Marine nutrients underpin productivity and functioning of oceanic island ecosystems. Seabirds represent a primary source of marine nutrients. In tropical regions, some of the largest seabird populations nest on atolls, yet there is limited information available on seabird contributions to atoll ecosystem nutrient dynamics. To investigate the spatial and seasonal dynamics of seabird contributions, we assessed seabird colonies of different taxa, including red-footed boobies and terns, nesting on separate islands of Farquhar Atoll, Seychelles. We assessed nutrient concentrations of guano, soil, coastal plants and nearby seagrass in seabird colonies and at a control island with no seabirds, during the wet and dry seasons. Sooty terns contributed the highest quantities of nutrients, estimated at 71.2 N tonne.yr-1and 52.2 P tonne.yr-1. Seabird-derived nutrient transfer occurred year-round from seabird colonies to soil, coastal plants and seagrass. Soil macro- and inorganic nutrients were higher in the high-density, ground-nesting tern colony and during the dry season, coinciding with the breeding period of sooty terns. Both red-footed booby and tern colonies maintained high nitrogen levels (%N) in coastal plants year-round, while phosphorus levels (%P) did not differ between islands or seasons. Seabird-derived nitrogen reversed nitrogen limitation (log C:N) of seagrass during the dry season. We provide the first insights into seabird nutrient contributions to atoll ecosystems in Seychelles, with recommendations for seabird conservation to boost and support atoll and island ecosystem resilience. Our results from a relatively undisturbed atoll serve as a baseline with which more impacted atolls and future changes can be assessed.

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Dissipation of seabird‐derived nutrients in a terrestrial insular trophic web

Cited by 7 publications

References 59 publications

Seabirds subsidize terrestrial food webs and coral reefs in a tropical rat‐invaded archipelago

Seabirds subsidize terrestrial food webs and coral reefs in a tropical rat‐invaded archipelago

Seabird presence and seasonality influence nutrient dynamics of atoll habitats

Seabird traits and seasonality modulate nutrient dynamics of terrestrial and marine habitats on atolls

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