type of transitions (i.e., sudden (pulse) transitions or more gradual changes) in the chosen ecological time series, some indicators and methods may result in clear early-warning signals, as demonstrated by the shiftogram and alertogram approaches, while other methods may have limited utility in informing ecosystem-based management, as they show no or weak (i.e., too late for a management measure to implement) early-warning potential (Table 1). Hence, we suggest that a multiple method approach may provide a sound scientific basis for detecting and evaluating early- warning signals and thus provide timely advice for immediate management actions in the face of future ecosystem changes [37]. Such a multiple method approach should be based on (i) the availability and quality of monitoring data; (ii) a thorough sensitivity analysis of key methodological assumptions and potential sources of bias of a given methodology; and (iii) a scientifically sound interpretation of results based on the best available knowledge concerning the ecological variable in ques- tion. Eventually, early-warning systems, including suitable indica- tors and related methods, for detecting and preventing unwanted catastrophic changes must be tailored to the local ecosystem characteristics. Supporting Information Figure S1 Map of the Baltic Sea and its location within Northern Europe. The central part of the Baltic Sea encompasses three deep (,70 m) basins important for marine biota, the Bornholm Basin (BB), the Gdansk Deep (GD) and the Gotland Basin (GB); largely corresponding to the International Council for the Exploration of the Sea (ICES) official sub-divisions 25, 25 and 28, respectively (thin lines). Furthermore, these basins are part of a long-term spatially and temporally disaggregated zooplankton monitoring program in the Baltic Sea. (JPG) Figure S2 Temporal variance of Pseudocalanus acuspes (circles) and Acartia spp. (triangles) estimated by standard deviations (SD) and the first-order autocorre- lation coefficient (AR(1)) of detrended time-series for a sliding window of 10 (A, D), 15 (B, E) and 20 (C, F) years. Vertical dashed bars mark the timing of the Central Baltic Sea regime shift in the late 1980s. (TIF) References 1. Venegas J, Winkler T, Musch G, Melo M, Layfield D, et al. 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Acceleration in the rate of change (slope) in each year are shown by statistically significant second derivatives (f99’), where black and white dots represent major downward- and upward trends, respectively. (PPTX) Table S1 Test results for recent trends and changes in trends over 3-year periods before the regime shift in 1988 using intersection–union tests. P-values from a x2 goodness-of-fit test indicate whether the GAM fits satisfactory to the entire time-series. Significant negative (2) or positive (+) time trends in the rate of change (f9), as well acceleration (+) or deceleration (2) of the current trend (f99) are shown. Hence, an increase in a rate of decline is indicated by negative f9 and a positive f99. 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