OTUs related to organic enrichment status
ANOVA revealed six OTUs with significant differences in relative
abundances among organic enrichment statuses (Table 2). Of these, one
OTU showed highest relative abundance in oxic A sediments and one showed
highest relative abundance in oxic B sediments, and both of these two
OTUs were taxonomically assigned to a nematode species Sabatieria
punctata . The other four OTUs showed higher relative abundances in
hypoxic and/or anoxic sediments.
Pearson’s phi coefficient analyses revealed 35 OTUs correlated
significantly with organic enrichment status, with 26, eight, zero, and
one OTUs for oxic A, oxic B, hypoxic, and anoxic categories,
respectively (Table 3). Machine learning returned an overall prediction
accuracy for organic enrichment status based on pore-water sulphide
concentration of 0.77, with an accuracy of 0.91, 0.64, 0.40, and 0.85
for oxic A, oxic B, hypoxic, and anoxic samples, respectively. The three
OTUs with highest importance scores for prediction of organic enrichment
status were assigned to Sabatieria punctata , Capitella
capitata , and Gunnarea capensis , respectively (Table 4); all
these three OTUs showed preference for oxic B sediments. The OTU (OTU
id: c94fc2ac2f0dc7c32b3decffc60bfc12) with highest importance score for
predicting organic enrichment status had highest relative abundance in
oxic B sediments.