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

Channel region. Miller and Shanks (2004) found that Mg concentrations, and Zn and Pb concentrations
to a lesser extent, in otoliths of black rockfish (Sebastes melanops) were good discriminators of open coast
habitats along the Washington and Oregon coasts. Nishimoto (2009) examined the variability in otolith
chemistry in relation to temperature and salinity and determined that Ba, Mg, and Fe concentrations in
otoliths distinguished shortbelly rockfish (Sebastes jordani) from geographically distant regions with contrasting
oceanographic conditions.
Brown (2006) found that Pacific sanddab living in estuaries and sandy coastal habitats along the central
California coast had different elemental signatures defined by Sr, Li, Ba, and Mn. The signatures defining
the two habitats for Pacific sanddab were similar for English sole (Pleuronectes vetulus), another flatfish species
that resides in the same habitats. Sr was consistently higher and Li consistently lower in estuarine fish.
Ba and Mn differed between habitats in only some years.
Forrester and Swearer (2002) compared Cu, Sr, Ba, and Pb concentrations in otoliths of California halibut
from bay and open coast habitats in the southern California Bight including the Santa Barbara Channel.
In contrast to Brown (2006), Sr and Ba showed no significant difference in concentration in juveniles from
bays and open coast habitats. Mn, Cu, and Pb were higher in otoliths from bays than from coastal habitats
in the single year, 1998, when fish were collected from both kinds of habitats. Forrester and Swearer (2002)
also compared the otolith element concentrations from one year of sampling open coast habitats with four
previous years of sampling fish from bays. Mn was ruled out as a good marker, because otolith concentrations
from the open coast habitat in 1998 did not differ from otolith Mn from bays the four previous years.
Although Ba concentrations in otoliths did not differ between bay and open coast habitats in 1998; Ba in
otoliths from bay habitats in some years were significantly higher than coastal habitats sampled in 1998.
Otolith concentrations of Pb varied less than Cu between years among the bay sites. Findings from these
studies indicate that some elements may be more temporally stable than others in otolith elemental signatures.
Success in discriminating otoliths from the two different habitat types in this study was not associated
with observed seawater element concentrations. Regression analysis showed variability in otolith element
concentration among sites was not related to the concentration of the elements in our seawater samples
from kelp rockfish and sanddab habitats.
The variability in seawater sample concentrations of most elements within sites (platform or natural
habitat) was substantial (Fig. 8) indicating a source of error may have been our seawater collection method.
The seawater samples were taken from aboard an unanchored boat at the platforms and natural sanddab
habitat sites. Although the boat was repositioned between casts to adjust for drift particularly when near
a platform, and movement may have been (tens of meters at platforms; tens of meters to several hundred
meters from natural sanddab habitat collection sites). Although care was taken to minimize contamination
of the seawater collected from the Niskin bottle sampler, we cannot fully rule out contamination from the
bottle which was not acid-leached. For some trace elements (e.g., Ba, V, As, Se) contamination is relatively
easy to control, whereas for other elements (e.g., Pb, Zn, Fe, Hg, and Sn) more painstaking procedures are
required to collect uncontaminated samples (Donat and Bruland 1995).
Another source of error in estimating the relationship between element concentrations in otoliths and
seawater is that seawater was sampled only during a single visit to each site; whereas, the otolith elemental
concentration was measured from ablated samples integrating months of recent growth preceding capture
of the fish. We suspect that the element concentrations from the ablated otolith sample is affected by temporal
variability in seawater element concentrations over multiple time scales ranging from hours to months
due to changes in the rate of produced water discharge from a platform and oceanographic variability.
Produced water is the primary discharge associated with oil and gas recovery and is the second largest
non-drilling associated discharge from oil platforms. Cooling water discharges comprise the largest volume
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