Effects of the Razor Clam Tagelus plebeius on the Fate of Petroleum Hydrocarbons: A Mesocosm Experiment

Abstract

The relationship between organisms and contaminants may be a two-way interaction: contaminants affecting the biota and the biota affecting the environmental fate and distribution of the contaminants. This may be especially so for sediment-dwelling organisms, because their burrowing and feeding can drastically influence sediment characteristics. The present study looked at the influence of the suspension-feeding stout razor clam Tagelus plebeius on the distribution of crude oil and pyrene in greenhouse mesocosm experiments. Water column turbidity and sediment redox also were monitored during the 15- to 30-day exposures to provide information on the influence of hydrocarbons and the razor clams on environmental conditions. For the experiment with crude oil, sediment was taken from the mesocosms at the end of the experiment, and the hydrocarbon-degradation potential was assessed in incubations with C-naphthalene. The experiments used four treatments: hydrocarbons present/absent and razor clams present/absent. Hydrocarbon dosing levels were relatively low (1 mL of oil or 30 mg of pyrene per mesocosm with 22 L of natural sediment and 11 L of seawater). The presence of the razor clams resulted in hydrocarbon concentrations at the sediment surface being 25% lower than in mesocosms without clams. No consistent effects were noted for polycyclic aromatic hydrocarbon (PAH) concentrations in the water column or in subsurface sediment. The naphthalene-degradation potential was elevated for sediment from mesocosms dosed with oil, but the presence of the clams did not affect this potential. The presence of the razor clams resulted in a lowering of water column turbidity, but no effect on sediment redox. The hydrocarbon addition had no effect on turbidity, but sediment redox was lowered. While results show that the presence of the razor clams resulted in a loss of hydrocarbons from the surface sediment, the other results do not provide a clear picture of the underlying mechanisms and the fate of the PAHs lost from the sediment surface. We hypothesize that the loss of surface sediment PAHs was due to burial of surface sediment and possibly bioaccumulation by the clams. While additional research is needed for further insights into underlying mechanisms, the present work demonstrates that the presence of sediment-burrowing suspension feeders decreases hydrocarbon levels in surface sediment. This means that assessments of the impact of an oil spill should pay attention to effects on these organisms and to their influence on the fate and distribution of the spilled oil.

A Mesocosm Assessment of the Effect of Bioturbation by the Ghost Shrimp (Lepidophthalmus louisianensis) on the Fate of Petroleum Hydrocarbons in the Intertidal Zone

“…For dosing, a 3‐mL volume of oil was thoroughly mixed with 300 g of air‐dried Bay St. Louis sediment (using a spatula and mixed until all of the sediment had a uniform brown color), and this mixture was spread over the surface of the sediment in a mesocosm by pouring it from a container submerged below the water surface, resulting in the addition of 16.7 mL of oil/m 2 of sediment surface. Concentrations of individual PAHs in the sparged oil and in the dosing sediment have been reported previously (Klerks et al 2018); total concentrations for priority PAHs were approximately 2400 mg/L and 1170 mg/kg for the oil and dosing sediment, respectively. Mesocosms not dosed with oil received 300 g of the air‐dried sediment.…”

“…Samples were placed in 500‐mL glass containers and transported to the laboratory in a cooler. Samples were stored at –4 °C for a maximum of 24 h. Hydrocarbons were extracted using liquid–liquid extraction, and pyrene or the 16 US Environmental Protection Agency (USEPA) priority‐pollutant PAHs were quantified by gas chromatography flame ionization detector (GC‐FID), as described (Klerks et al 2018; see Supplemental Data, Online Resource 2). Replicates of several of the samples for oil and pyrene treatments were analyzed to assess reproducibility; the coefficient of variation ( CV ) averaged 12.6%.…”

“…Collected sediment samples were placed in a cooler and transferred to the laboratory, where they were frozen, freeze‐dried, and homogenized. Hydrocarbons were extracted from sediment using microwave extraction and concentrated in hexane under nitrogen, and PAHs were analyzed by GC‐FID, as described (Klerks et al 2018; Supplemental Data, Online Resource 2). Detection limits for individual PAHs ranged from 0.6 to 7.2 µg/kg (Klerks et al 2018), and replicated analysis had average CV s of 3.7 and 12.6% for, respectively, surface sediment and subsurface sediment.…”

Bioturbation by the razor clam Sinonovacula constricta affects benthic nutrient fluxes in aquaculture wastewater treatment ecosystems

“…In the shellfish filtering area, bioturbation by benthic shellfish may enhance the mineralization of organic matter; the release of nutrients from the sediment significantly improves nutrient recycling in the effluent treatment ecosystem because the feeding, burrowing and other activities of the shellfish alters the physical, chemical and ecological properties of the sediment (Thayer 1979, Meysman et al 2006, Creed et al 2010, Nicholaus & Zheng 2014, Zheng et al 2017. Shellfish, such as razor clams Sinonovacula constricta and Tagelus plebeius (Klerks et al 2018), may then feed on the phytoplankton that is promoted by the released nutrients and suspended organic particulates in the water. Thus, organically enriched sediment may be bioremediated by benthic shellfish, and the released nutrients may further promote the growth of phytoplankton, which could be reabsorbed by the shellfish (Meysman et al 2006, Tian et al 2016, Zheng et al 2017.…”