Increased Capacity for Polycyclic Aromatic Hydrocarbon Mineralization in Bioirrigated Coastal Marine Sediments

Figures & data

FIGURE 1 Sampling locations for stations P17 and P04 in Paleta Creek in San Diego Bay, CA.

FIGURE 2 Bacterial production (μ g C kg^{− 1} day^{− 1}) with depth (cm) for cores from stations P17 and P04. Error bars on bacterial production are the standard deviation of triplicate samples.

FIGURE 3 Pore water concentrations for sulfide (A), sulfate (B), alkalinity (C), manganese (D), and iron (E) for P17 (filled) and P04 (empty) cores.

FIGURE 4 Total PAH concentrations (ppm) with depth (cm) for core sections from P17 for P04 cores.

TABLE 1 Average (AVG) and Standard Deviation (SD) of PAH Mineralization Rates and Turnover Time

		Mineralization rate (μ g C kg^− 1 day^− 1)
		Naphthalene		Phenanthrene		Fluoranthene		Turnover time (days)
Core	Depth (cm)	AVG	SD	AVG	SD	AVG	SD	Phenanthrene	Fluoranthene
P17-1	0–2	1.06	0.162	3.48	1.20	0.445	0.232	14	530
	2–4	0.271	0.0416	0.435	0.180	0.105	0.114	119	1598
	4–6	0	0	0.592	0.128	0.244	0.177	90	436
	6–8	0	0	0.990	0.812	0	0	59	ND
	8–11	0	0	1.42	0.700	1.09	0.543	35	345
	11–14	0	0	0.418	0.080	0	0	78	ND
	14–17	0	0	0.718	0.526	0.497	0.056	60	236
P17-2	0–2	0	0	1.20	1.05	0.848	0.275	42	278
	2–4	0.521	0.031	0.742	0.125	0	0	70	ND
	4–6	0.064	0.007	0	0	0.065	0.029	ND	1632
	6–8	1.05	0.126	0.758	0.392	0.615	0.291	77	250
	8–11	0	0	1.73	0.547	0.476	0.166	28	790
	11–14	0.049	0.002	1.37	0.484	0.608	0.215	31	193
	14–17	0.284	0.009	0.762	0.245	0.133	0.048	43	684
P04	0–2	0	0	7.86	1.07	5.09	0.807	3	20
	2–4	2.65	0.193	8.57	5.50	1.80	1.75	3	5
	4–6	0	0	3.53	0.508	2.38	1.85	7	27
	6–8	0	0	5.09	2.13	1.99	1.37	6	43
	8–11	0	0	2.69	0.726	0.790	0.491	8	67
	11–14	0.183	0.021	5.02	1.32	0.872	0.149	5	91
	14–17	0	0	3.51	0.602	3.07	2.52	4	15
Note. Mineralization rates and turnover time were measured for each of the three cores with depth (cm). ND = not determined.

TABLE 2 Bacterial Production and PAH Mineralization Rate Averages

		AVG rate of core section (μ g C kg^− 1 day^− 1)
Rate parameter	Station	No sulfide	Sulfide present
Bacterial production	P17	99.4	33.4
	P04	110.1	18.9
Naphthalene mineralization	P17	0.48	0.20
	P04	0.66	0.06
Phenanthrene mineralization	P17	0.68	0.33
	P04	2.53	1.54
Fluoranthene mineralization	P17	0.42	0.35
	P04	6.88	0.88
Note. Bacterial production and PAH mineralization rate averages were higher for core sections that did not have sulfide present compared with those that had measurable sulfide concentrations.

FIGURE 5 Model-calculated irrigation coefficients are shown as functions of depth. The model results indicate that the DIC profile of core P17-1 was a result of strong bioirrigation near the sediment-water interface, and that of core P04 was a result of deep-penetrating bioirrigation as a significant bioirrigation was hindcasted for 13 to 14 cm below the interface. The DIC profile of core P17-2 indicates a lack of bioirrigation.

TABLE 3 Irrigation Coefficient and Intrinsic Degradation Rates

		Intrinsic biodegradation capacity (μ g C m^− 2 day^− 1 for top 17-cm sediment)
Core	Irrigation coefficient 10^− 7 cm^2 s^− 1 (depth, cm)	Naphthalene	Phenanthrene	Fluoranthene
P17-1	0–4	27	187	64
P17-2	0	43	170	67
P04	0–17	58	837	692
Note. The irrigation coefficient was greater than 10^− 7 cm^2 s^− 1 in the top 0 to 4 cm at P17 but extended throughout the 17-cm depth of the core from P04. The intrinsic degradation rates for each PAH were used to calculate the degradation capacity of 1 m^2 of surface sediment integrated to the 17-cm depth of the core measurements.