However, some SBF cuttings may be deposited out to 1 to 2 km from the discharge point. SBF base fluid concentrations in sediments usually decrease with time due to resuspension, bed transport, mixing, and biodegradation. Sediment dwelling bacteria and fungi are able to use SBF base fluids as a source of nutrition, releasing simple non-toxic metabolic degradation products. Biodegradability of SBF base fluids under different conditions in sediments varies widely. Biodegradation of SBF base fluids in sediments results in depletion of oxygen concentrations in the sediments.
Oxygen depletion slows biodegradation and adversely affects resident benthic fauna.
SBF base fluids have a low bioavailability and toxicity to water column and sediment dwelling marine organisms. Their toxicity is much less than that of OBF base oils. The toxicity of SBFs is comparable to that of WBFs. Several field studies have been performed to monitor the biological effects of SBF cuttings discharges on the benthic environment. The studies show that where SBF base fluids accumulate to high concentrations in sediments, adverse effects in benthic communities are evident.