Table 5.
Selected environmental variables from the sampling sites in the Gulf of Mexico
| All sampling sites | Group 1 | Group 2 | Group 3 | |||||
|---|---|---|---|---|---|---|---|---|
| Physicochemical variables | Mean ± SD | Range | Mean ± SD | Range | Mean ± SD | Range | Mean ± SD | Range |
| Alkalinity (meq.L-1) | 2.64 ± 0.41 | 2.92-0.84 | 2.72 ± 0.13 | 2.55-2.92 | 2.60 ± 0.59 | 0.84-2.92 | 2.55 ± 0.50 | 1.44-2.92 |
| Clay (%) | 24.41 ± 15.10 | 0-55.00 | 24.53 ± 1.00 | 0- 55.00 | 28.00 ± 0.00 | 0- 55.00 | 18.49 ± 0.00 | 0-30.00 |
| Silt (%) | 15.00 ± 9.92 | 0-30.00 | 13.40 ± 8.87 | 2.00-30.00 | 17.73 ± 10.51 | 0- 30.00 | 14.14 ± 11.68 | 0.00-30.00 |
| PCNM58K | −3.04 ± 21.20 | −62.31-21.62 | −8.36 ± 20.47 | −39.63-21.62 | −0.45 ± 25.65 | −62.31-21.62 | 4.31 ± 13.33 | −12.28-21.62 |
| pH sediments | 7.73 ± 0.21 | 7.45-8.33 | 7.61 ± 0.13 | 7.45-8.33 | 7.82 ± 0.26 | 7.59-8.33 | 7.84 ± 0.16 | 7.72-8.17 |
| Porosity (%) | 0.51 ± 0.08 | 0.26-0.64 | 0.53 ± 0.07 | 0.34-0.64 | 0.50 ± 0.10 | 0.26-0.60 | 0.49 ± 0.09 | 0.33-0.60 |
| Sand (%) | 60.59 ± 21.55 | 20.00-100 | 62.07 ± 19.34 | 20.00-97.00 | 54.27 ± 25.65 | 20.00-100 | 67.37 ± 19.40 | 47.00-100.00 |
| Heavy metals | ||||||||
| Aluminum (μg.g−1) | 4.75 ± 4.14 | 0.24-18.52 | 2.83 ± 3.15 | 0.24-12.15 | 7.68 ± 5.00 | 1.00-18.52 | 4.25 ± 1.19 | 1.78-5.76 |
| Cobalt (μg.g−1) | 0.23 ± 0.07 | 0.05-0.49 | 0.24 ± 0.10 | 0.05-0.49 | 0.21 ± 0.07 | 0.05-0.31 | 0.24 ± 0.01 | 0.23-0.26 |
| Vanadium (μg.g−1) | 0.59 ± 0.87 | 0.02-4.01 | 1.17 ± 1.05 | 0.10-4.01 | 0.10 ± 0.05 | 0.02-0.20 | 0.13 ± 0.07 | 0.04-0.28 |
| Zinc (μg.g−1) | 0.88 ± 0.54 | 0-1.86 | 0.44 ± 0.34 | 0.00-1.14 | 1.09 ± 0.36 | 0.49-1.86 | 1.52 ± 0.20 | 1.11-1.78 |
| Hydrocarbons | ||||||||
| Aliphatics (μg.g−1) | 0.30 ± 0.32 | 0-1.28 | 0.18 ± 0.00 | 0-0.45 | 0.45 ± 0.00 | 0-1.28 | 0.31 ± 0.00 | 0-0.74 |
| Total PAH (μg.g−1) | 1.31 ± 0.51 | 0.48-2.37 | 1.29 ± 0.52 | 0.48-2.37 | 1.38 ± 0.58 | 0.69-2.15 | 1.24 ± 0.44 | 0.79-2.09 |
| UCM (μg.g−1) | 11.65 ± 8.66 | 0.72-30.98 | 12.24 ± 8.41 | 1.45-26.79 | 13.96 ± 10.04 | 0.72-30.98 | 6.74 ± 5.27 | 0.91-16.23 |
| Nutrients | ||||||||
| Nitrates (μM) | 1.90 ± 3.04 | 0.06-15.74 | 2.75 ± 4.28 | 0.20-15.74 | 1.25 ± 1.09 | 0.06-2.69 | 1.10 ± 1.06 | 0.20-2.69 |
| Phosphorus (μM) | 5.37 ± 1.22 | 1.85-6.50 | 5.27 ± 1.29 | 2.30-6.50 | 5.42 ± 1.32 | 1.85-6.38 | 5.53 ± 1.06 | 3.38-6.38 |
The variables in bold are the ones that explained the highest percentage of variance in the redundancy analysis for both the overall analysis (33 sampling sites) and for each one of the groups of sampling sites in Figure 2. The PCNM58K corresponds to a spatial variable acting at the spatial scale of 58 km. Total PAH = total polycyclic aromatic hydrocarbons, UCM = unresolved complex mixture.