Fig. 2: Coral- and otolith-bound δ15N for fossil (~7 ka) and modern (0.1 ka) time periods.
From: Fossil isotope evidence for trophic simplification on modern Caribbean reefs
a, Descriptions of the taxa analysed in both time periods to generate an ecosystem nitrogen isotope distribution for coral reef trophic reconstruction. Top row: larger reef-associated fishes; middle rows, smaller reef-associated fishes; bottom row, primary consumers. b, Measurements of otolith- and coral-bound nitrogen isotopes (δ15N) for each fish family, where each symbol denotes an individual coral fragment or fish otolith. Each symbol represents the mean ± 1 s.d. of replicate measurements from individual otoliths or coral fragments. The n value below each category reflects the number of biologically independent individuals (coral fragments or fish) measured for each family, time period and region. c, Family-level patterns in δ15N (trophic level) for fossil and modern time periods (where n is the same as for b). Statistical tests for whether mean δ15N has changed since the mid-Holocene are shown below each fish silhouette (Wilcoxon, two-sided; *P < 0.05, **P < 0.01, ***P < 0.001). δ15N declined for Dominican Republic cardinalfishes (P = 2.5 × 10−4, W = 100, r = 0.873) and grunts (P = 0.048, W = 20, r = 0.82) (Extended Data Table 2). Data from Bocas del Toro, Panama, are shown on the left; data from the southeast Dominican Republic are shown on the right for b and c. d, Regional and family-level patterns in isotopic niche width (diet-driven δ15N diversity), calculated as the 1 s.d. of the individual-level measurements in b. The percent decline compared with the mid-Holocene niche width is shown above each modern bar. Statistical tests for whether the variances have changed since the mid-Holocene are shown below each fish silhouette (F-test, two-sided; *P < 0.05, **P < 0.01, ***P < 0.001). Panama gobies (P = 0.043, F = 3.0), silversides (P = 0.0042, F = 8.53) and grunts (P = 0.0004, F = 10.22) declined significantly (Extended Data Table 4). Grey arrows (from b, pointing towards c and d) indicate that the metrics shown in c (trophic position) and d (dietary diversity) are calculated from all data shown in b. Insets in each of c and d illustrate how each metric was calculated. Fish silhouettes in a–d reproduced from ref. 51, GitHub, under a GPL-2 license.
