Reproductive Ecology and Body Burden of Resident ... - The Love Lab

of non-drilling associated discharges from offshore oil platforms, but along with sanitary/domestic waste,
this discharge is only a source of residual chlorine (Steinberger et al. 2005). Produced waters are natural
geological formation water and includes introduced seawater recovered with the extraction of oil (Raco
1994). The produced water is separated from the oil and gas mixture on site at an offshore platform or is
sent via pipeline to an onshore facility. After separation, the produced water is treated and discharged to the
ocean. If processed onshore, the produced water is transferred by pipeline back to the source platform and
discharged. The release of produced water is intermittent over hours or days and discharge rate and volume
varies over time and among platforms (D. Panzer, U.S. Minerals Management Service, pers. comm.).
Over the life of the well as the amount of oil in the well decreases, the quantity of produced water
extracted with oil and gas increases as the process of water-flooding with seawater is used to enhance hydrocarbon
production from an aging well. Consequently, the concentrations of constituent elements, such as
Ba, in the discharge often decreases over time. Eleven platforms were discharging produced water in 1990;
14 platforms in 1996, and14 platforms in 2000. Steinberger et al (2005) reported that discharges of produced
water were 2.3% higher in 1996 than in 1990, and 7.3% higher in 2000 than in 1990. All of the platforms in
federal waters included in our study (the exception is Platform Holly in State waters) presently discharge
produced water.
Ba is the largest metal constituent in mass emissions from produced water discharged from platforms
(Steinberger et al. 2005). Higashi et al (1997) reported that Ba and Sr were the only elements among Al,
As, Cd, Co, Cu, Cr, Fe, Mn, Mo, Pb, Sn, Zn that were consistently in high concentration in produced water
from an oil processing facility in Carpinteria. Only one element, Cu, among Mg, Sr, Mn, Fe, and Ba included
in our otolith chemistry statistical analysis, is monitored and reported in Discharge Monitoring Reports
(DMRs) submitted by individual platforms in compliance with NPDES permit requirements. Metals included
in the DMRs are Cd, Cr, Cu, Pb, Hg, Ni (Nickel), Se (Selenium), Ag, and Zn. Steinberger et al. (2005)
estimated 1734 kg of Ba was released from federal Southern California platforms in 1996; in comparison,
0.19 kg of Cu was released in the same year. Estimated flow-weighted concentrations were 323 µg l -1 (2.352
µM) for Ba and 0.04 µg l -1 (6.295x10 -4 µM) for Cu in produced water discharges in 1996 (Steinberger et al.
2005). The general platform permit limit for Cu discharge is 20 µg l -1 (0.315 µM).
Ba enrichment in otoliths of kelp rockfish from platforms may have been related to the discharge of
produced water. Kelp rockfish inhabiting the midwater structure of the platform may be exposed to elevated
Ba Ca -1 which we were unable to detect from our water samples. Higashi et al (1997) reported that M. californianus
showed a clear decreasing trend in Ba accumulation levels in newly grown shell material with increasing
distance from a produced water outfall off Carpinteria in some but not all outplanting experiments
conducted over the course of a year suggesting that seasonal currents patterns may have affected dispersal
of the discharge.
As in our study, Warner et al. (2005) found no relationship between Ba from the outermost material of
adult kelp rockfish otoliths and Ba Ca -1 from seawater collected at the time fish were sampled in 2002 from
rocky reef sites off west Santa Barbara, northeast Santa Cruz Island, and south Santa Cruz Island. Laboratory
and field studies have determined that otolith Ba correlates with ambient Ba in seawater (Bath et al. 2000,
Elsdon and Gillanders 2003, Elsdon and Gillanders 2005). The field studies compared estuarine and coastal
habitats where differences in otolith Ba are more extreme than open coastal site comparisons (e.g., Brown
2006).
If found to be temporally consistent, unique signatures of elements incorporated in the structure of
otoliths of kelp rockfish potentially can be used as a tool to reconstruct an individual’s history of movement
among habitats. However, we suspect that otolith Ba is temporally variable. For example, Warner et
al. (2005) reported the mean Ba Ca -1 in seawater was 3.97 (S.E.=0.05, n=12) µmol/mol from the vicinity of
our kelp rockfish natural site in the west Santa Barbara area and 3.75 (SE=0.107, n=6) µmol/mol from a
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