Table S1. Metagenomic library statistics Table S2. Bacterial SSU rRNA amplicon library statistics Table S3. Environmental measurements used for 25 m analyses Table S4. Environmental measurements used for 500 m analyses Table S5. Comparison of 25 m and 500 m shared and unique OTUs. To calculate relative abundances all amplicon reads from samples within the same depth were combined. * also in previous category. Table S6. Number of reads in each 25 m metagenomic dataset assigned to each taxonomic group Table S7. Number of reads in each 500 m metagenomic dataset assigned to each taxonomic group Table S8a. Correlations between microbial community alpha diversity and environmental properties at 25 m. Legend. All diversity indices were resampled using rarefaction. Read depths as follows: All SSU rRNA reads from metagenomic data: 892 Amplicon reads: 9661 Protein-coding reads from metagenomic data: 476661. Symbols: § averaged over previous 4 days ¶ averaged over previous 30 days *significant below P< 0.1 after applying the Benjamini-Hochberg procedure to account for multiple tests (n=24 hours of day light not included due to similarity with shortwave radiation). Table S8b. Correlations between microbial community alpha diversity and pigments (organism containing pigments) at 25 m. Legend. All diversity indices were resampled using rarefaction. Read depths as follows: All SSU rRNA reads from metagenomic data: 892 Amplicon reads: 9661 Protein-coding reads from metagenomic data: 476661. Symbols: *significant below P< 0.1 after applying the Benjamini-Hochberg Procedure to account for multiple tests (n=6). Table S9. Mantel tests comparing microbial community beta diversity and environmental properties at 25 m. Legend. All diversity indices were resampled using rarefaction. Read depths as follows: All SSU rRNA reads from metagenomic data: 892 Amplicon reads: 9661 Protein-coding reads from metagenomic data: 476661. The Spearman correlation coefficient was used for mantel tests. Symbols: § averaged over previous 4 days ¶ averaged over previous 30 days *significant below P< 0.1 after applying the Benjamini-Hochberg Procedure to account for multiple tests (n=24 hours of day light not included due to similarity with shortwave radiation). Table S10. Correlations between microbial community alpha diversity and environmental properties at 500 m. Legend. All diversity indices were resampled using rarefaction. Read depths as follows: All SSU rRNA reads from metagenomic data: 1475^ Amplicon reads: 6909 Protein-coding reads from metagenomic data: 930072^. Symbols: ^HOT194_500m excluded due to low sequencing depth § averaged over previous 4 days ¶ averaged over previous 30 days *significant below P< 0.1 after applying the BenjaminiHochberg procedure to account for multiple tests (n=12). Table S11. Mantel tests comparing microbial community beta diversity and environmental properties at 500 m. Legend. All diversity indices were resampled using rarefaction. Read depths as follows: All SSU rRNA reads from metagenomic data: 1475^ Amplicon reads: 6909 Protein-coding reads from metagenomic data: 930072^. The Spearman correlation coefficient was used for mantel tests. Symbols: ^HOT194_500m excluded due to low sequencing depth § averaged over previous 4 days ¶ averaged over previous 30 days *significant below P< 0.1 after applying the Benjamini-Hochberg procedure to account for multiple tests (n=12). Table S12. Correlations between OTU module eigengenes and the most strongly correlated environmental measurements at 25 m. Legend. Modules were calculated using the 193 most abundant OTUs in the amplicon datasets (see methods). Both positively and negatively correlated OTUs were included in the same module. All environmental parameters that significantly correlated with ME1 and ME2 are shown. For modules 3-6 only the environmental parameter with the strongest correlation is shown as no environmental parameters significantly correlated with these modules. P-values were adjusted using the Benjamini-Hochberg procedure to account for multiple tests (n=144 24 environmental measurements (as in table S8a) x 6 modules.) Symbols: §averaged over previous 4 days ¶ averaged over previous 30 days. Table S13. Correlations between protein ortholog module eigengenes and the most strongly correlated environmental measurements at 25 m. Legend. Modules were calculated for protein orthologs from abundant taxonomic groups in the metagenomic datasets (see methods). Both positively and negatively correlated OTUs were included in the same module. All environmental parameters that significantly correlated with modules are shown plus the environmental parameter with the strongest correlation if no parameter significantly correlated. Pvalues were adjusted using the Benjamini-Hochberg procedure to account for multiple tests (n=576 24 environmental measurements (as in table S8a) x 24 modules.) Symbols: ¶ averaged over previous 30 days. Table S14. Correlations between module eigengenes and the most strongly correlated environmental measurements at 500 m. Modules were calculated using the 330 most abundant OTUs in the amplicon datasets (see methods). Both positively and negatively correlated OTUs were included in the same module. P-values were adjusted using the BenjaminiHochberg procedure to account for multiple tests (n=408 12 environmental measurements (as in table S10) x 34 modules. Symbols: § as measured at ocean surface and averaged over previous 4 days ¶ as measured at ocean surface and averaged over previous 30 days.