In EffetsCumulatifsNavigation/ceanav: Research compendium for project on the assessment cumulative effects of marine vessel activities in the St. Lawrence

Marine pollution {#pollutionmaritime}

meta <- read_yaml("../data/data-metadata/int_st_pollution_maritime.yml")
show_source(meta$rawData, lang = "en")

We introduced an environmental stressor to replace operational discharges on the environmental stressor side, and water quality on the valued component side. This new stressor was used to address the difficulties in characterizing these two elements initially identified as concerns by the parties involved in the project.

On the operational discharge side, this decision was made due to the lack of data covering the entire study area. From a legislative perspective, vessels transiting Canadian waters must exchange any ballast water within pre-established areas called “Canada’s Designated Alternate Ballast Water Exchange Areas” [@tc2021; @tc2021b]. However, the area closest to the study area is located at the entrance to the Gulf of St. Lawrence, meaning it does not affect the study area covered by our assessment (Figure \@ref(fig:ballast)). Data specific to operational discharges from vessels is apparently available for only a small proportion of the Canadian fleet operating in the study area and would have triggered a considerable data capture effort. As such, these data were not considered in the assessment.

knitr::include_graphics("./figures/data0051-ballast.png")

On the water quality side, this decision was made due to the difficulty of attributing variations in water quality specifically to marine vessel activities. There are many other factors that influence water quality in coastal, aquatic and marine environments, and differentiating these effects was beyond the scope of this pilot project. More details are available in the section on water quality.

As in @halpern2019, marine pollution was characterized by combining environmental stressors related to marine vessel activities. This choice assumes that water quality is more at risk from shipping activities and the resulting pollution via operational discharges, gas leaks, waste discharges, etc. In the absence of exhaustive data on operational discharges and the difficulty of establishing a direct link between water quality and cumulative marine vessel activities, we used the marine pollution index as a proxy to identify the environments most at risk from pollution from marine vessel activities.

The marine pollution index is obtained by combining the relative intensity of all stressors directly associated with shipping activities, i.e. anchorage sites, dredging activities, shipping-related activities and commercial fishing. Characterization of the accidental spills is not included since it has already been explained in detail in the issue of toxic spills in the environment rather than as a stressor related to regular shipping problems. The marine pollution intensity ($I_{pollution}$) within a cell $j$ is the sum of the intensity of selected environmental stressors normalized between 0 and 1:

$$I_{pollution,j} = \frac{1}{|S|} \sum_{s \in S} I_{s,j}$$

where $|S|$ is the number of environmental stressors considered, $s$ are the individual environmental stressors, and $I_{s,j}$ is the relative intensity of the stressor $s$ within cell $j$.

knitr::include_graphics("./figures/figures-integrated/pollution_maritime-pollution_maritime.png")

EffetsCumulatifsNavigation/ceanav documentation built on April 17, 2023, 1:02 p.m.