Eight co-culture combinations, each compared against what their individual strains predict. Bar length is the synergy index — how far observed degradation exceeds the additive expectation. Every bar points right.
Co-culture composition determines alginate degradation efficiency. Synergy index S for eight co-culture combinations, sorted by magnitude. S = (observed − expected) / expected, where expected ΔV% is the mean of constituent monoculture performance (ADE-III). All eight values are positive, confirming synergistic degradation. F13 combinations — built from the weakest individual degraders — show the strongest synergy (S = +76 to +102%; Cohen's d = 1.10–1.44, all P < 0.001), while F10 combinations show moderate synergy (S = +11 to +22%); 13B01+9ZC77 did not reach significance. Significance from one-sample t-tests against the additive null. Bars draw in on view; in a static preview the final state is shown.