Discontinuity Analysis Reveals Alternative Community Regimes During Phytoplankton Succession

Abstract

It is well-recognized in plankton ecology that phytoplankton development can lead to distinct peaks (i.e., blooms) during spring and summer. We used a 5-year (2007-2011) phytoplankton data set and utilized discontinuity analysis to assess resilience attributes of spring and summer blooms based on the cross-scale resilience model. Using the size structure (i.e., cross-scale structure as an indicator of resilience) in the sampled plankton data, we assessed whether spring and summer blooms differ substantially between but not within blooms; that is, whether they comprise alternative community regimes. Our exploratory study supported this expectation and more broadly resilience theory, which posits that ecological systems can manifest in and change between alternative regimes. The dynamics of regimes receives increased attention because rapid environmental change potentially irreversibly alters ecosystems. Model organisms are needed that allow revealing patterns and processes of various aspects of regime dynamics at tractable time scales. Our preliminary findings suggest that phytoplankton can be suitable models for assessing the intricacies of regimes and regime changes.

How do ecological resilience metrics relate to community stability and collapse?

“…Instead, resilience metrics predicted maintenance of overall community structure per their synchrony with abrupt community shifts across scales. That is, resilience metrics predict significant abrupt community shifts but not community similarity over time (Angeler et al, 2019b). However, higher resilience metrics did weakly predict maintenance of community composition over time as well as constraining mean species turnover which still supports a connection between species composition and resilience.…”

“…unresponsive metric if systems reorganize around similar numbers of scale domains during and post-collapse, meaning this metric may only detect extreme collapse events (Angeler et al, 2019b;Roberts et al, 2019).…”

“…It is not obvious that a system with more body mass aggregations is more resilient than a system with fewer (Allen et al, 2005). Likewise, it is not clear that when resilience erodes and regime shifts occur that the number of body mass aggregations will change; they may simply reorganize around a similar number of scale domains (Angeler et al, 2019b;Gunderson et al, 2012). Also, it is unclear what increases versus decreases in resilience metrics mean for propensity toward regime shifts (Allen et al, 2005;Fischer et al, 2007).…”

“…Within-scale redundancy, cross-scale redundancy, and number of scale domains are expected to most strongly predict community collapse (Nash et al, 2016;Roberts et al, 2019;Spanbauer et al, 2016). Finally, the second resilience-collapse prediction is cross-scale resilience metrics will only weakly predict maintenance of specific species assemblages: we test this by determining how cross-scale resilience metrics relate to changes in community similarity over time (Gunderson, 2000;Angeler et al, 2019b).…”