Trends in Ecology & Evolution
OpinionEmergent Properties Delineate Marine Ecosystem Perturbation and Recovery
Section snippets
Are there Fundamental Patterns of Marine Ecosystems?
The question remains whether there are common patterns from ecosystems that arise from underlying, fundamental ecosystem processes [1]. Several have been proposed [2] and often such proposed patterns are emergent properties of ecosystems 3, 4. Yet, whether such emergent patterns are germane for marine ecosystems remains unclear due to the distinctiveness of the marine environment 5, 6 (Box 1). Detecting any such common emergent patterns in marine ecosystems is useful to understand the effects
Indicators and Patterns
Indicators are needed to assess the degree of perturbation or recovery of marine ecosystems 11, 16. Addressing elements of marine ecosystem response to perturbations has typically emphasized a population or habitat level that disregards community- or systemic-level compensation and dynamics. However, aggregative or system-level patterns tend to be more robust and integrative 17, 18. Further, if changes in aggregative or system-level patterns are persistent, they represent bigger concerns than
Pattern Detection
The cumB–TL plots exhibit the sigmoidal shape as expected (Figure 2). Even the widest percentiles from empirical data encompassing at least 95% of all upwelling, continental shelf, reef, and open ocean ecosystems show relatively limited variance from the median pattern. Estuaries also exhibit this pattern, but have a wider range of variance near the base of the curve (Figure 2E). There is a distinct and repeatable sigmoidal pattern across TL for cumB, with a noticeable increase usually between
Consistency of Perturbation Effects and Thresholds
Time series from over 20 marine ecosystems demonstrate that curve parameters exhibit notable responses to perturbation (Figure 4A–D; Box 2). For instance, the Black Sea is a system known to have experienced significant and major perturbations related to fishing pressure and an invasive jellyfish outburst 36, 37, and these are reflected in the time series of inflection points (Figure 4A,C) and slopes (Figure 4B,D), which exhibit high variability and an overall decline in both parameters. Other
Explanation Based on Trophic Theory
Basic ecosystem theory clearly emphasizes an energetic context within which ecological systems function. Thermodynamic constraints limit the overall productivity of a system, reflected directly in the observation that transfer efficiencies, or the efficiency that the energy in an ecosystem is transferred from TL to succeeding TL, are always <1, such that there is a decline in production rate with increasing TLs 40, 41, 42. The TL concept posited by Lindeman and others, which summarizes the
Delineating Thresholds of Perturbation and Recovery
From this theoretical background, widespread empirical support, and common values of curve parameters, can we delineate when a marine ecosystem is in an abnormal state, indicative of probable perturbation (Box 4)? Or, conversely, can we delineate when a marine ecosystem has ‘recovered’? As noted, changes in the slope and inflection points of the cumB–TL and cumP–cumB curves can be tracked over time and related to particular pressures (Figure 4A–D) [50]. Similar to population- or habitat-level
Acknowledgments
This work was conceptualized and conducted as part of visiting scientist exchanges between F.P. and J.L. via support from the University of Ca’Foscari and NOAA, a visiting scientist exchange via a Frohlich Fellowship (J.L.) and support from CSIRO and NOAA between J.L. and E.F., NOAA support for J.L. to visit S.L. and C.S., CAMEO support for MENU2, and in conjunction with numerous ICES working groups in which several of the authors participated. We thank Selina Heppel, Eva Plaganyi-Lloyd, Tim
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