The British Columbia Marine Ecological Classification

The British Columbia Marine Ecological Classification (BCMEC) is a hierarchical classification that delineates Provincial marine areas into Ecozones, Ecoprovinces, Ecoregions and Ecosections. The classification was developed from previous Federal and Provincial marine ecological classifications which were based on 1:2,000,000 scale information. The BCMEC has been developed for marine and coastal planning, resource management and a Provincial marine protected areas strategy. A new, smaller level of classification termed "ecounits" developed using 1:250,000 scale depth, current, exposure, subsurface relief and substrate was created to verify the larger ecosections, and to delineate their boundaries. This paper reviews the creation of the ecounits and the results of this ecosection assessment. Twelve ecosections are identified and delineated as a result of this research.

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Marine Ecoprovinces
Marine Ecoregions
Marine Ecosections

Provincial Marine Ecounits

Criteria for the assessment and possible further subdivision of the marine ecosections were selected on their ecological relevance and availability of systematic Provincial coverage. Potential criteria were initially identified by a Steering Committee formed from the CTF. These criteria were compiled for a test area and the results subsequently reviewed at a workshop involving the Steering Committee, westcoast representatives from Provincial and Federal Agencies, and marine contractors. Based on workshop discussions and the test results, the following themes were identified as initial criteria for defining marine ecounits: wave exposure, depth, subsurface relief, seabed substrate and current regimes.

Wave exposures was identified as a controlling factor in marine environments due to its usefulness in delineating open coast from island groups and inlets, and its influence on nearshore and shoreline community composition. High exposure coastlines have different intertidal and nearshore biota than protected shorelines, a result of the mechanical wave action on the shore and shallow seabed. Exposure is less significant to benthic (bottom dwelling) species in deeper waters, but is a useful measure in separating intertidal and nearshore species. Wave exposure was estimated from two sources. Exposure information was generalized from detailed digital information (1:40,000 scale) from the Provincial Oil Spill Response and Information System (OSRIS) and on the basis of maximum fetch estimates from Canadian Hydrographic Service (CHS) Chart 3000. Exposure categories followed those developed for the RIC British Columbia Physical Shore-Zone Mapping System and are presented in Table 2 (Howes et al. 1993).

Depth was selected as it provides a major ecological division based on the photic (light penetration and photosynthesis) zone and deeper areas. The break between the photic zone and the non-photic zone is considered more significant than the further subdivisions within the non-photic zone. Water depths were obtained from the Natural Resources Series bathymetric 1:250,000 scale maps. Where the natural resource maps were not available, depth was obtained from detailed nautical charts.

Subsurface relief refers to bottom morphology and is a function of shape and elevation range. Areas of high relief tend to have irregular surface morphologies and high elevation ranges; low relief areas have uniform slopes with small ranges in elevation. Relief was included as a criteria as it is an indirect indication of mixing and areas with high relief environments provide habitat to many benthic and demersal organisms including the Lingcod (Ophiodon elongatus) and Rockfish (Sebastes spp.) (Hart 1973, Ilg & Walton 1979). Subsurface relief was estimated from the charts and depth data sets. High relief areas were identified by Dr. John Harper and Peter Wainwright (Wainwright et al. 1995). Care was taken to ensure consistency given the differences in scales and contour intervals between the charts and bathymetric maps.

Currents were identified as they are important in controlling marine biota and provide an index of water stratification. Areas of high currents increase circulation and the availability of water-borne food to sessile organisms, are almost always well-mixed, and typically represent areas of high biological productivity (Dyer 1973, Pritchard 1955). Information on high and low current velocity was hindered by the lack of detailed and systematic information outside of the Strait of Georgia and Strait of Juan de Fuca. As a result, high current areas were defined as areas where current velocities frequently exceed 3 knots. This information was obtained from CHS sailing directions (CHS 1987, 1990) and a review of the 1:40,000 and larger scale hydrographic charts of the coast.

Seabed substrate provides an important constraint for benthic and demersal communities and yields an indirect index of substrate mobility. For example, bottom areas consisting of mud are usually an indicator of low energy, depositional conditions, whereas rock or gravel substrates can indicate higher current activity and non-depositional conditions. Community response to substrate is most evident within the photic zone, but certain species such as the English (Lemon) Sole (Pleuronectes vetulus) and Starry Flounder (Platichtys stellatus) occur in conjunction with sand and silt substrates in deeper areas (Lamb & Edgell 1986, Tyler et al. 1987).

The preferred source of seabed substrate was the Geological Survey of Canada surfical sediment distribution maps (Barrie et al. 1989a,b,c,d, Conway et al. 1985a,b, Luternauer 1986, Luternaurer and Murray 1983, Luternauer et al. 1989, Pharo and Barnes 1976). These maps provide good coverage of Hecate Strait, Queen Charlotte Sound, Vancouver Island Shelf and the Strait of Georgia. There are no systematic sediment data for the continental slope and rise, offshore ridges or the abyssal plain. These areas cannot be assumed to be muddy (McCoy and Sancetta 1987, Price 1977, Scrimger and Bird 1969) and were catalogued as unknown. For the remaining areas in shallow water (< 200 metres) and where there are no surficial sediment maps, chart substrate data were used. Although these data are obtained by leadline sampling and are less reliable than the surficial geology maps, it was considered adequate for this project.

Information on the thematic data was transferred from the various sources onto the 1:250,000 scale Natural Resource Maps and digitized into ARC/INFO. All data were converted to Albers polyconic projection using a datum of NAD83. The landward boundary for the thematic information and the marine ecosections was defined as the coastline on the 1:250,000 Natural Resource Maps. This coastline is equivalent to the coastline on the Provincial 1:250,000 digital National Topographic Service maps which is defined as the shoreline at high water mark.

The ecounits were created by combining the five themes into a single map using GIS technology to create a digital coverage of the data set. Each ecounit on the map consists of one subclass value for each of the five themes. Sliver ecounit polygons from this combined data set were then eliminated in an iterative fashion by gradually increasing the minimum size threshold from 0.10 to 10.0 square kilometers. Sliver polygons were added to the adjacent polygon that had the most similar combination of subclasses.

The next step involved the reconciliation of the ecosection boundaries to the ecounits. The original boundaries of the ecosections were defined at 1:2,000,000 scale. These boundaries were overlaid onto the ecounit map and adjusted by manual editing involving human judgment. This was done as the original boundaries displayed substantial inaccuracies when compared to the 1:250,000 thematic data and ecounit map.

All polygons below a minimum size threshold of 15 square kilometers were identified and examined once the ecosections boundaries were established. Most of these small areas were eliminated by aggregation with the appropriate polygons; a few polygons less than 15 square kilometers had their boundaries adjusted in a manner consistent with the available thematic data that resulted in an area greater than 15 square kilometers.

The final step in the preparation of the ecounit map involved a review of the resulting ecounit classes. The ecounits were grouped into repetitive classes and the frequency of occurrence and cumulative area of each class was reviewed. Rare classes with one occurrence were individually examined. Most were incorporated with other classes through a review of the thematic data; a few were retained as they were considered unique.

Marine Ecological Classification Ecounits

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Last Updated: 06.06.2006