Print PageBiodiversity loss has prompted the rapid development of research examining the relationships between biodiversity and ecosystem functioning. Understanding how biodiversity affects the functioning of an ecosystem requires expanding our scope to include realistic scenarios of species loss and multi-trophic interactions. We examined effects of realistic biodiversity loss across a multitrophic food web on ecosystem structure and function of seasonally isolated tropical floodplain lagoons. Lagoons were replicated using 1000 L mesocosms, and realistic scenarios of fish assemblage structure (species composition and abundance) were created based on seven years of data on fish assemblages provided by the Upper Paraná River Floodplain LTER (Brazil). Diversity treatments replicate the sequential loss of rare species from assemblages (species richness = 18, 14, 10, 6, 2, and no fish species), which occur across all trophic levels of these complex food webs.
Results/Conclusions
Total fish survivorship differed across treatments (ANOVA, P =0.016) and among species within treatments, with a general trend of increasing mortality with greater species richness due to the presence of multiple piscivores. However, the highest species richness treatment had reduced mortality due to intraguild predation by piranha, reducing the effective number of piscivores present in those assemblages. Fish diversity and time significantly affected total zooplankton abundance, with increases over time across all treatments but especially in species rich assemblages (rmANOVA, time: P = < 0.001; treatment: P = 0.03). Nutrients were also correlated with total zooplankton abundance, and our combined results indicate differences in the relative importance of bottom-up and top-down effects on zooplankton abundance across diversity levels. Loss of rare species from these complex isolated floodplain lagoon food webs can have both direct and indirect effects on ecosystem structure and function.
