Flow network indices signal a directional change in ecosystems: Evidence from a small mountain lake (Lake Santo, northern Italy)

Empirical evidence of the theoretically expected trends of ecosystem development is scarce so far. In this research, we used long-term empirical data about the plankton community of a small mountain lake (Lake Santo, northern Apennines, Italy) to reconstruct its developmental trajectory during a period comprised between early 1970 s and 2010 s. We exploited these data to build yearly ecological networks and from their configuration of energy flows we computed network information indices. The trends of these indices enlighten about the developmental trajectory of this ecosystem during the period covered by the data set. In particular, they indicate that Lake Santo evolved in the direction of increasing stability at the expense of efficiency in energy transfer. We compared these results with current hypotheses about the directionality of ecosystem development, which are rooted in ecosystem theory, and discussed the possibility that, counter to some theoretical models of ecosystem development, Lake Santo followed an unimpeded direction of development rather than a trajectory typical of an ecosystem under stress. Finally, the long-term trends of flow network indices provided insights about the health status of the ecosystem.

Automated summary

Empirical evidence for the expected trends in ecosystem development is lacking. This study used long-term empirical data from Lake Santo, a small mountain lake in the northern Apennines, Italy, to reconstruct its developmental trajectory. The findings suggest that the lake evolved towards increased stability at the expense of energy transfer efficiency. These results challenge previous hypotheses and suggest that Lake Santo followed an unimpeded developmental trajectory rather than a stress-induced trajectory. The long-term trends in network indices also provided insights into the health status of the ecosystem.