Geochemical data on otoliths of chaetodon speculum from New Caledonia
Coral reefs are one of the most diverse ecosystems on Earth. They are currently exposed to increasing levels of anthropogenic perturbations. Several recent reviews point to the lack of good indicators for these perturbations especially to monitor their effects on fish populations or fish assemblages. The SW lagoon of New Caledonia is an ideal location to test indicator species in this context as contrasting sites are present within a small geographical range. This study analysed fish from four sites, one with heavy industrial pollution, another dominated by domestic waste, a third with historic mining activities, and the fourth as a control. The butterfly fish, Chaetodon speculum, was chosen to determine C. speculum’s potential as an indicator species due to its link to coral, its sedentary behaviour and its wide geographical distribution. The size distribution, growth rate, age distribution and whole otolith composition were analysed at each site. Age and mean growth rate were analysed from daily increments of the otoliths. The concentrations of eight elements (Li, Mg, Co, Cu, Rb, Sr, and Ba) were measured by ICP-MS in the otoliths.
The sites under anthropogenic impact were distinct from the control site by fish size frequencies, age distributions, and the chemical content of their otoliths. The chemical elements Mg, Co, Cu, and Rb showed differences amongst sites. Fish belonging to the sites furthest from Noume´a could be discriminated in nearly 80% of samples or 60% of the cases when otolith weight or fish age respectively were taken into account. Ni concentrations of the otoliths were also higher in the bays where water concentrations of this element were known to be higher, but these differences were no longer significant once corrected for otolith weight.
otoliths, ICP MS, Trace elements, spatial variations, New Caledonia, geochemistry
-18.947145N, -23.412157S, 168.980894E, 162.784605W
These data include trace element concentrations (Li, Mg, Co, Cu, Rb, Sr, and Ba) from Chaetodon speculum otoliths, as well as biometric data from individuals. The fish were collected by spear-fishing in October 2002 at 4 locations in the SW lagoon of New Caledonia: Grand Rade (22°14'42.7 "S 166°24'41.6 "E), Prony (22°19'28.2 "S 166°49'57.5 "E), Baie St Marie (22°17'17.4 "S 166°28'38.5 "E), and the ilot of Sèche Croissant (22°19'20.8 "S 166°22'14.2 "E).
Both sagittae were extracted from the fresh fish with ceramic forceps rinsed with diluted HNO3 to avoid contamination. Otoliths were soaked in ultra pure nitric acid for 5 min to remove surface chemical contamination, and then they were rinsed with milli-Q_ water. Each sagitta was weighed to the nearest 10 mg on a microbalance before being individually dissolved in ultra pure HNO3 15 N. The solution was then diluted proportionally to the mass of the sagittae and analysed with an ICP-MS Varian_ Ultramass_at Pôle de spectrométrie Océan , Plouzané, France.
The ICP-MS data were collected using the following isotopes: 7Li, 25Mg, 59Co, 60Ni, 63Cu, 85Rb, 84Sr, 137Ba. To ensure precision and accuracy between sessions, Indium was used as an internal standard to correct for instrumental drift during analytical sessions when the otolith standard NIES 22 was analysed. The NIES standard was measured at the beginning and end of each session. Four multi-element standards with increasing concentrations were used for external calibration.