Species Sensitivity Distributions for Suspended Clays, Sediment Burial and Grain Size Change in the Marine Environment

Abstract

Assessment of the environmental risk of discharges, containing both chemicals and suspended solids (e.g., drilling discharges to the marine environment), requires an evaluation of the effects of both toxic and nontoxic pollutants. To date, a structured evaluation scheme that can be used for prognostic risk assessments for nontoxic stress is lacking. In the present study we challenge this lack of information by the development of marine species sensitivity distributions (SSDs) for three nontoxic stressors: suspended clays, burial by sediment, and change in sediment grain size. Through a literature study, effect levels were obtained for suspended clays, as well as for burial of biota. Information on the species preference range for median grain size was used to assess the sensitivity of marine species to changes in grain size. The 50% hazardous concentrations (HC50) for suspended barite and bentonite based on 50% effect concentrations (EC50s) were 3,010 and 1,830 mg/L, respectively. For burial the 50% hazardous level (HL50) was 5.4 cm. For change in median grain size, two SSDs were constructed; one for reducing and one for increasing the median grain size. The HL50 for reducing the median grain size was 17.8 m. For increasing the median grain size this value was 305 m. The SSDs have been constructed by using information related to offshore oil-and gas-related activities. Nevertheless, the results of the present study may have broader implications. The hypothesis of the present study is that the SSD methodology developed for the evaluation of toxic stress can also be applied to evaluate nontoxic stressors, facilitating the incorporation of nontoxic stressors in prognostic risk assessment tools.

Toxicological evaluation of clay minerals and derived nanocomposites: A review

“…In another study performed by Oosterhout and Lürling (2011), Phoslock s induced toxic effects on a Daphnia galeata population, although these researchers stated that these toxic effects could be due to several factors acting in synergy. Other researchers studied the species sensitivity distribution of 12 species and four taxonomic groups exposed to bentonite, concluding that the organisms living in sediments are accommodated to address these clays at high density (Smit et al, 2008). Strachan and Kingston (2012) observed that different species of bivalves (Modiolus modiolus, Venerupis senegalensis, Dosinia exoleta, and Chlamys varia) increased their normal filtration rate when bentonite was added to the aqueous media.…”

Effects of the Terra Nova offshore oil development on benthic macro-invertebrates over 10 years of development drilling on the Grand Banks of Newfoundland, Canada

“…Barium, as barite, in drill muds is basically toxicologically inert (Neff, 2008;Smit et al, 2008). Suspended solids (e.g., barite, bentonite and cuttings particles) at high concentrations in the water column near the sediment-water interface can irritate gills and have other physical effects on benthic invertebrates (Barlow and Kingston 2001;Armsworthy et al, 2005;Smit et al, 2008). At the suspended solids levels (usually less than 5 mg/L) observed at Terra Nova (Suncor, 2011), any effects should be restricted to plankton and filter-feeding bivalves (Smit et al, 2008).…”

“…Suspended solids (e.g., barite, bentonite and cuttings particles) at high concentrations in the water column near the sediment-water interface can irritate gills and have other physical effects on benthic invertebrates (Barlow and Kingston 2001;Armsworthy et al, 2005;Smit et al, 2008). At the suspended solids levels (usually less than 5 mg/L) observed at Terra Nova (Suncor, 2011), any effects should be restricted to plankton and filter-feeding bivalves (Smit et al, 2008). However, abundances of Telliniade (Macoma), the dominant bivalve at Terra Nova, increased rather than decreased near drill centres and at higher sediment barium concentrations.…”

“…Drilling waste includes drill cuttings (crushed formation rock from well holes) and drilling muds (also called drilling fluids) used to facilitate the drilling process (DeBlois et al, 2014a, this issue). Drill muds may be water-based (WBM), oil-based (OBM) or synthetic-based (SBM) (OGP, 2003;Melton et al, 2004;Neff et al, 2000Neff et al, , 2005Neff, 2008). The upper sections of most wells at Terra Nova were drilled with lightly treated WBM (containing up to 10% particulate barite and bentonite clay) and the mud and cuttings were discharged directly to the seafloor adjacent to the drill centres.…”

“…Most WBMs contain low concentrations of biodegradable organic compounds and effects of the muds and associated cuttings usually are physical, through accumulation of fine particles that might disrupt filter feeding in bivalves (Cranford and Gordon, 1992) or bury epi-and in-faunal benthic organisms (Smit et al, 2008;Veltman et al, 2011). Nevertheless, some WBMs, particularly those containing glycols or organic polymers, have caused sediment organic enrichment, resulting in a reduction in number of taxa, abundance, biomass and diversity of macrofauna (Trannum et al, 2010), and all drilling muds contain metals, associated primarily with drilling mud barite, that could lead to toxic effects in high concentrations, if they are bioavailable (Neff, 2008).…”