TY - JOUR

T1 - Seabird diversity and biomass enhance cross-ecosystem nutrient subsidies

AU - Benkwitt, Cassandra E.

AU - Carr, Peter

AU - Wilson, Shaun K.

AU - Graham, Nicholas A. J.

PY - 2022/5/11

Y1 - 2022/5/11

N2 - Mobile consumers are key vectors of cross-ecosystem nutrients, yet have experienced population declines which threaten their ability to fill this role. Despite their importance and vulnerability, there is little information on how consumer biodiversity, in addition to biomass, influences the magnitude of nutrient subsidies. Here, we show that both biomass and diversity of seabirds enhanced the provisioning of nutrients across tropical islands and coral reefs, but their relative influence varied across systems. Seabird biomass was particularly important for terrestrial and near-shore subsidies and enhancing fish biomass, while seabird diversity was associated with nutrient subsidies further offshore. The positive effects of diversity were likely driven by high functional complementarity among seabird species in traits related to nutrient storage and provisioning. However, introduced rats and non-native vegetation reduced seabird biomass and diversity, with rats having a stronger effect on biomass and vegetation having a stronger effect on diversity. Accordingly, the restoration of cross-ecosystem nutrient flows provided by seabirds will likely be most successful when both stressors are removed, thus protecting both high biomass and diversity. Recognizing the importance of mobile consumer diversity and biomass, and their underlying drivers, is a necessary step to conserving these species and the ecosystem functions they provide.

AB - Mobile consumers are key vectors of cross-ecosystem nutrients, yet have experienced population declines which threaten their ability to fill this role. Despite their importance and vulnerability, there is little information on how consumer biodiversity, in addition to biomass, influences the magnitude of nutrient subsidies. Here, we show that both biomass and diversity of seabirds enhanced the provisioning of nutrients across tropical islands and coral reefs, but their relative influence varied across systems. Seabird biomass was particularly important for terrestrial and near-shore subsidies and enhancing fish biomass, while seabird diversity was associated with nutrient subsidies further offshore. The positive effects of diversity were likely driven by high functional complementarity among seabird species in traits related to nutrient storage and provisioning. However, introduced rats and non-native vegetation reduced seabird biomass and diversity, with rats having a stronger effect on biomass and vegetation having a stronger effect on diversity. Accordingly, the restoration of cross-ecosystem nutrient flows provided by seabirds will likely be most successful when both stressors are removed, thus protecting both high biomass and diversity. Recognizing the importance of mobile consumer diversity and biomass, and their underlying drivers, is a necessary step to conserving these species and the ecosystem functions they provide.

KW - Ecology

KW - Research articles

KW - biodiversity

KW - coral reef

KW - functional diversity

KW - nutrient subsidy

KW - restoration

KW - seabird

U2 - 10.1098/rspb.2022.0195

DO - 10.1098/rspb.2022.0195

M3 - Journal article

VL - 289

JO - Proceedings of the Royal Society B: Biological Sciences

JF - Proceedings of the Royal Society B: Biological Sciences

SN - 0962-8452

IS - 1974

M1 - 20220195

ER -