GSC Seascape Map of the Bay of Fundy now available

This map depicts seascapes of the Bay of Fundy.  We define seascapes as underwater landscapes with recurring patterns of geomorphology, texture, and biota.

Geomorphology – The various geomorphologic classes are prime drivers for the seascape classification, since they integrate geological processes over time and tend to control the distribution of textures and biota.  The essential method of delineating topographic units is the analysis of shaded-relief elevation models derived from gridded multibeam sonar bathymetry data.  In an integrated seascape approach it is necessary to understand the genesis of the geomorphic classes, and towards this end we use sub-bottom seismic reflection profiling (both high- and low-resolution) to determine the acoustic characteristics of sediment with depth, and hence delineate the surficial geology classes

Texture and mobility – While texture conventionally refers to sediment grain size at the seafloor, we also expand the definition to describe sediment properties at depth and sediment mobility at the sea floor.  A critical component of delineating sediment texture is backscatter strength map, a proxy for sea floor texture.  In the map area this parameter is broadly bi-modal:  areas of high backscatter strength correspond to bedrock and gravel at the sea floor, while areas of low backscatter strength correspond to sand, muddy sand, and mud.  Sidescan sonar was used in the study to ascertain the presence or absence of bedforms such as megaripples, which are below the resolution of the multibeam sonar data.  Inferences about mobility were made using bedform characteristics as a guide.  However, the modeled sediment mobility index (Fig. 4) was also a guide.

Biota – Biota were observed on sea floor photographs (Figs. 5–10) and video collected in areas considered representative of the geomorphic and textural classes.  In general, hard substrates have attached biota, in contrast to sandy and muddy seafloors that may contain infauna.  The long, linear, horse mussel reefs constitute a unique seascape unit, and host horse mussels (Modiolus modiolus) in association with the bryozoan Flustra foliacea, and Polymastia sp. in sponge gardens.  Generally the analysis of biota was not systematic, and we have taken the approach that geomorphology and texture are important determinants.  

To access the map go to the GEOSCAN website (http://geoscan.ess.nrcan.gc.ca/starweb/geoscan/servlet.starweb?path=geoscan/geoscan_e.web) and search for OPEN FILE 7028.