Sublethal Effects of Pentachlorophenol in Abalone (Haliotis rufescens) Veliger Larvae as Measured by 31P-NMR

Toxicity tests with larval marine organisms are widely used as water quality-monitoring tools. Often employing a single morphological endpoint, they provide only limited insight into toxic action mechanisms. Since mechanistic observations can provide more sensitive endpoints of toxicity, the goal of this study was to modify existing in vivo31P-NMR techniques to evaluate the effects of pentachlorophenol (PCP) on high-energy phosphates in veliger larvae of the red abalone (Haliotis rufescens), a species and life stage commonly used in developmental toxicity tests. Fluxes of phosphoarginine (PA), nucleoside triphosphates (NTPs), sugar phosphates (SPs), and inorganic phosphate (Pi), as well as in intracellular pH (pHi), were monitored via NMR using a flow-through exposure system. The exposure protocol included 1 h of clean seawater, 2 h of PCP (1.2 mg L−1) exposure, and 2 h of recovery in clean seawater. During PCP exposure, veligers displayed maximum declines in PA and NTP resonance intensities to 38±10% (P<0.01) and 61±16% (P<0.05) of reference values (represented by the average resonance intensities taken from 1 h of preexposure spectral acquisition). Inorganic phosphate concentrations rose to 302±63% (P<0.01), and pHi declined from a reference period average of 7.12±0.03 to 7.04±0.04 (P<0.05). On exposure to clean seawater, veligers recovered within 2 h, returning to 196±53, 89±12, and 89±13% of the reference intensities for Pi, PA, and NTPs, respectively (P>0.05 for all values), while pHi increased to 7.08±0.11. When compared with adult abalone, veliger larvae responded similarly to PCP, differing mainly in their rapid recovery (2 h for larvae versus 6 h adults) and more severe acidification (a 0.08 pH unit decline versus a 0.03 pH unit decline). This report describes an application of NMR for small (≥200 μ) marine organisms using commonly available vertical-bore NMR magnets; it should prove adaptable for use with other similar larval forms.