From species sensitivity to hypoxia to effect factors modelling in life cycle impact assessment (LCIA)

Nutrient enrichment of coastal waters fuels planktonic growth. The subsequent sinking of this organic matter and its aerobic respiration by heterotrophic bacteria in bottom waters results in the consumption of dissolved oxygen (DO) there. If excessive amounts of organic carbon reach the benthic layer DO depletion may drop it down to hypoxic or anoxic levels.

Acute and chronic effects on biota may then be expected. The sensitivity of relevant demersal (benthic and benthopelagic) species (n=91) to DO levels, as lowest-observed-effect-levels (LOEL), was used to estimate the community’s sensitivity in five climate zone (polar, subpolar, temperate, subtropical, tropical).

Species Sensitivity Distribution (SSD) curves combining DO concentrations and Potentially Affected Fractions (PAF) of species were plotted to estimate hazard concentrations (HC50LOEL) per climate zone, and Effect Factors (EF, [(PAF)·m3.kgO2-1]). Preliminary EF results range from 220 (PAF)·m3·kgO2-1 (polar zone) to 310 (PAF)·m3·kgO2-1 (tropical zone).

A site-generic value of 260 (PAF)·m3·kgO2-1 is useful when no relevant spatial differentiation is to consider. The proposed method for effects modelling contributes with an essential component in the characterisation of eutrophying emissions in Life Cycle Impact Assessment (LCIA) and is applicable in a global assessment framework of marine eutrophication impacts.