Marine food webs are an important source of nutrients on isolated terrestrial ecosystems, including many important breeding habitats. Guano-derived nutrients from seabirds and marine mammals may be essential to maintain biodiversity on low productivity islands. Globally, seabirds are especially valuable proxies for environmental and climate change studies. Our work reconstructs the dynamic interaction of the climate system with marine and terrestrial ecosystems using paleoenvironmental reconstructions and establishes a baseline for ecologists and conservation biologists to contextualize the sensitivity of seabirds and their habitats to global change. This study addressed three main questions: 1) How have seabirds and marine mammals responded to abrupt shifts in the climate system during the Holocene? 2) How has terrestrial vegetation responded to fluctuations in seabird nutrient inputs? 3) Did seabirds, marine mammals, and vegetation respond to changes in the latitudinal position and intensity of the Southern Hemisphere westerly wind belt? Using multi-proxy analyses of sedimentary records found in tussac grass peatlands in the Falkland Islands, we evaluated proxies for marine-derived nutrients from guano (bioelements), plant species assemblages (pollen analysis), and fire frequency (charcoal) and natural abundance of δ15N to identify shifts in the trophic position of marine top predators breeding on the Falkland Islands.
Results/Conclusions
Multi-proxy analyses of tussac grass (Poa flabellata) peat cores from two locations were used to reconstruct environmental changes over the last 13,000 years. Reconstructions of past vegetation, seabirds, and marine trophic structure test the sensitivity of the terrestrial-marine linkage to climate change, and its impacts on coupled island plant and animal communities. Results indicate that an abrupt decline in the relative abundance of seabird and marine mammal populations at (~6,000 cal yr BP) occurred in sync with changes in island plant communities that provide important breeding habitat. Secondly, our work provides the first evidence that fire is a frequent component of tussac grasslands in the Falklands, though whether these were natural or set by humans remains under investigation. These results improve our understanding of how the climate system and specifically changes in the position and strength of the southwesterly winds influenced tussac grasslands and nutrient input through fluctuations in populations of marine fauna. Providing a significant baseline of the relative abundance of top predators breeding on the Falkland Islands, relative changes in the marine trophic structure, and the nutrients deposited into tussac grasslands supporting higher-level terrestrial consumers will inform habitat restoration ecologists who are currently working to restore tussac grasslands.