Whole-body ConCentrations of elements in three fish speCies from offshore oil platforms and natural areas in the southern California bight, usa

There is concern that offshore oil platforms off Southern California may be contributing to environmental contaminants accumulated by marine fishes. To examine this possibility, 18 kelp bass (Paralabrax clathratus Girard, 1854), 80 kelp rockfish (Sebastes atrovirens Jordan and Gilbert, 1880), and 98 Pacific sanddab (Citharichthys sordidus Girard, 1854) were collected from five offshore oil platforms and 10 natural areas during 2005–2006 for whole-body analysis of 63 elements. Forty-two elements were excluded from statistical comparisons as they (1) consisted of major cations that were unlikely to accumulate to potentially toxic concentrations; (2) were not detected by the analytical procedures; or (3) were detected at concentrations too low to yield reliable quantitative measurements. The remaining 21 elements consisted of aluminum, arsenic, barium, cadmium, chromium, cobalt, copper, gallium, iron, lead, lithium, manganese, mercury, nickel, rubidium, selenium, strontium, tin, titanium, vanadium, and zinc. Statistical comparisons of these elements indicated that none consistently exhibited higher concentrations at oil platforms than at natural areas. However, the concentrations of copper, selenium, titanium, and vanadium in Pacific sanddab were unusual because small individuals exhibited either no differences between oil platforms and natural areas or significantly lower concentrations at oil platforms than at natural areas, whereas large individuals exhibited significantly higher concentrations at oil platforms than at natural areas. twenty-seven active and seven decommissioned offshore oil-and-gas production platforms (henceforth referred to as “oil platforms”) are located within the southern California bight between point arguello in the north and the us-mexico border in the south. over the next few decades, many active platforms are expected to undergo decommissioning as their economic profit margins decline. decommissioned platforms in southern California historically have undergone complete removal. however, recent ecological studies indicate that platforms provide artificial structure for marine life, including many fish species of recreational and commercial importance, and may contribute to rebuilding overfished stocks (love et al. 2000, 2005, 2006). platform decommissioning options range from leaving the entire intact structure in place to removal of part or all of the structure. regardless of the option selected, resource managers are concerned that environmental contaminants associated with the drilling process (i.e., contaminated drilling mud and cuttings), the produced water, and other platform-related activities (e.g., sanitary and domestic wastes) could pose toxic risks to fishes and consumers of tainted fishes, including marine birds, mammals, and humans. BULLETIN OF MARINE SCIENCE. VOL 89, NO 3. 2013 718 drilling muds or fluids are specially formulated mixtures of fresh water or seawater with clays, minerals, chemicals, and other materials used for cleaning drill bits, transporting cuttings, reducing friction, and stabilizing the borehole (raco 1993). drill cuttings are particles of crushed sedimentary rock produced in the process of drilling. barium sulfate is added to drill muds as a weighting agent, and the appearance of barium in cuttings is due to drilling mud adhering to the cuttings (raco 1993). Chromium can originate from chrome or ferrochrome lignosulfonate, which are drilling mud additives (phillips et al. 2006). drill cuttings can contain elevated concentrations of lead and zinc, possibly as a result of using pipe-thread compound to lubricate the threads of drill pipes (raco 1993, phillips et al. 2006). These and other metals also originate from formation of solids and mud additives. most produced water is a brine that may contain dissolved solids, metals, organic compounds, and sulfur at substantially higher concentrations than in seawater. produced water can contain trace elements, and various petroleum hydrocarbons, including monoaromatic compounds, polycyclic aromatic hydrocarbons, and polar compounds [gale et al. (2013) report on polycyclic aromatic hydrocarbons in fishes living around California oil platforms]. nickel and vanadium are components of crude oil (phillips et al. 2006). sanitary and other domestic wastes are generated by platform personnel, and include sewage, garbage, and waste water, and any associated contaminants (raco 1993). previous surveys of inorganic contaminants in liver, kidneys, gonads, and axial muscle of marine fishes from the southern California bight included measurements of aluminum, antimony, arsenic, barium, beryllium, cadmium, chromium, copper, iron, manganese, mercury, molybdenum, nickel, lead, selenium, silver, thallium, tin, vanadium, and zinc (e.g., stapleton 1968, mcdermott et al. 1976, pollock et al. 1991, sCCWrp 1994, phillips et al. 1997, allen et al. 2004, iec 2007, groce and gartman 2008). however, these early studies generally focused on runoff from urban areas or discharge from nearshore sewage outfalls. relatively little attention has been given to documenting elemental body burdens in fishes from oil platforms (bascom et al. 1976, mcdermott-ehrlich and alexander 1976). The purpose of our study was to determine if offshore oil platforms in the southern California bight represent a major source of contamination by trace elements in fish species of economic (commercial and recreational) importance. natural hard substrates (i.e., rocky outcrops or reefs) and soft substrates (i.e., mud and sand) located somewhat away from selected platforms were intended to serve as relatively uncontaminated reference sites. specific objectives were to document body burdens of elements in representative midwater and bottom-dwelling fish species and to determine if elemental concentrations in fishes from platforms differed from those at natural areas.