Eelgrass (Z. marina) extent at sites along the Central Coast, British Columbia

This polygon dataset contains a time series for the spatial extent of eelgrass (Zostera marina) meadows delineated from aerial imagery at several long-term monitoring sites located on the Central Coast of British Columbia.

The areal extent of eelgrass (Zostera marina) meadows is an important metric for understanding the broader dynamics of eelgrass habitats. Since 2015, the Hakai Geospatial Program has been using remotely piloted aerial systems (RPAS, aka drone) imagery to record change in eelgrass meadow extent at monitoring sites on the Central Coast of BC. Prior to 2015, eelgrass extent at monitoring sites has been conducted using aerial fixed wing aircraft and helicopter imagery and towed underwater video (see 2014 metadata record for eelgrass sites delineated using towed underwater video). Existing methods for mapping eelgrass (e.g. low-tide walking surveys, towed video, or boat-based SCUBA surveys) can be difficult to apply repeatedly and efficiently across large geographic extents. RPASs are portable and efficient tools for mapping nearshore marine environments, such as eelgrass habitat. Despite some limitations of RPAS mapping (e.g. weather, flight time, survey size), RPASs are able to collect high-resolution data (<10 cm) during short windows of opportunity (e.g. low tide).

Core monitoring sites at the Hakai Institute include three eelgrass beds (Pruth Bay, Choked Pass and Koeye) that are mapped annually and three others (Triquet Bay, Goose SW, and McMullin North) which are mapped bi-annually (Fig. 1). Other sites have been mapped advantageously or as part of shorter-term projects and are included in this data package.

For each site, eelgrass extent was delineated using a combination of object-based image analysis (eCognition Developer 9) and manual delineation within a GIS environment (ArcGIS, v 10.8). In brief, image objects area created via a multiresolution segmentation algorithm within eCognition and the site orthomosaic. These objects are exported to a GIS environment where an analyst classifies objects as eelgrass. The minimum mapping unit for a patch of eelgrass or patch within a bed is 4 m2.

Access and Use

Licence: Creative Commons Attribution 4.0
Limitations: Appropriate credit must be given to Hakai Institute and the authors of the dataset.

Data and Resources

Citation

Keywords

Dataset extent

Map data © OpenStreetMap contributors

Metadata Reference Date(s) March 02, 2022 (Publication)
March 02, 2022 (Revision)
Dataset Reference Date(s) December 07, 2020 (Publication)
Frequency of Update As Needed

Responsible Party 1
Name
Luba Reshitnyk
Affiliation
Hakai Institute
Role
  • Author
  • Point of Contact
  • Principal Investigator
  • Processor
Responsible Party 2
Name
Thea Mai
Affiliation
Hakai Institute
Email
data@hakai.org
Role
Author
Responsible Party 3
Name
Hakai Geospatial Technology Team
Affiliation
Hakai Institute
Email
data@hakai.org
Role
  • Custodian
  • Distributor
  • Originator
  • Owner
  • Point of Contact
  • Principal Investigator
Responsible Party 4
Affiliation
Hakai Institute
Email
data@hakai.org
Role
  • Distributor
  • Owner
  • Resource Provider

Field Value
Ocean Variables Other
Scope Dataset
Status On Going
Topic Category oceans
Maintenance Note Generated from https://cioos-siooc.github.io/metadata-entry-form
Spatial Extent { "coordinates": [ [ [ -128.65354407, 51.37817421 ], [ -127.69773286, 51.37817421 ], [ -127.69773286, 52.1127963 ], [ -128.65354407, 52.1127963 ], [ -128.65354407, 51.37817421 ] ] ], "type": "Polygon" }
North Bounding Latitude 52.1127963
South Bounding Latitude 51.37817421
East Bounding Longitude -127.69773286
West Bounding Longitude -128.65354407
Vertical Extent
Min
0.0
Max
0.0
Default Locale English
Citation identifier
Code
10.21966/03pw-2190