期刊
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
卷 114, 期 29, 页码 7647-7652出版社
NATL ACAD SCIENCES
DOI: 10.1073/pnas.1614778114
关键词
animal migration; mass drowning; nutrient cycling; Serengeti wildebeest; stable isotope
资金
- Yale Institute for Biospheric Studies
- Robert and Patricia Switzer Foundation
- National Geographic Society Committee for Research and Exploration
- National Science Foundation [DEB 1354053, DEB 1354062]
- Direct For Biological Sciences
- Division Of Environmental Biology [1354053] Funding Source: National Science Foundation
- Division Of Environmental Biology
- Direct For Biological Sciences [1354062] Funding Source: National Science Foundation
The annual migration of similar to 1.2 million wildebeest (Connochaetes taurinus) through the Serengeti Mara Ecosystem is the largest remaining overland migration in the world. One of the most iconic portions of their migration is crossing of the Mara River, during which thousands drown annually. These mass drownings have been noted, but their frequency, size, and impact on aquatic ecosystems have not been quantified. Here, we estimate the frequency and size of mass drownings in the Mara River and model the fate of carcass nutrients through the river ecosystem. Mass drownings (>100 individuals) occurred in at least 13 of the past 15 y; on average, 6,250 carcasses and 1,100 tons of biomass enter the river each year. Half of a wildebeest carcass dry mass is bone, which takes 7 y to decompose, thus acting as a long-term source of nutrients to the Mara River. Carcass soft tissue decomposes in 2-10 wk, and these nutrients are mineralized by consumers, assimilated by biofilms, transported downstream, or moved back into the terrestrial ecosystem by scavengers. These inputs comprise 34-50% of the assimilated diet of fish when carcasses are present and 7-24% via biofilm on bones after soft tissue decomposition. Our results show a terrestrial animal migration can have large impacts on a river ecosystem, which may influence nutrient cycling and river food webs at decadal time scales. Similar mass drownings may have played an important role in rivers throughout the world when large migratory herds were more common features of the landscape.
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