Fig. 4. Phenolic compounds inhibit the degradation of sucrose.

a,b, Sediments from replicate cores (n = 3) collected from inside a Mediterranean P. oceanica meadow off the Island of Elba, Italy, consumed ¹³C₁₂-sucrose (a) and produced ¹³CO₂ (b) over the course of oxic and anoxic experiments conducted over 24 h. Individual points in both a and b represent treatment means ± s.e.m. across independent replicates (n = 3). Under oxic conditions, the production rate of ¹³CO₂ from ¹³C₁₂-sucrose was similar across treatments and at least 2.5× higher than rates observed under anoxia (note different y axis scales). However, in the anoxic incubations, the addition of phenolics extracted from P. oceanica tissues inhibited the microbial degradation of sucrose to CO₂. c, The estimated measured respiration rates under anoxia show that the production of ¹³CO₂ from sucrose in the presence of phenolic compounds is at least eight times lower than that of natural or artificial seawater condition (Supplementary Table 5). The size of the arrows is proportional to the potential rate of CO₂ released from sucrose in mmol(C) m⁻² d⁻¹.