Post 1: Observations

I have chosen Bronte Marsh as a study area. The marsh is a remnant coastal wetland area at the downstream limit of Bronte Creek before it flows into Lake Ontario. It is surrounded by urban development within the Town of Oakville, Ontario. Despite the urban development around the marsh, the Bronte Creek watershed is mostly undeveloped, with only 4% settled between urban and rural settlements (Conservation Halton, 2002). The marsh is bisected by Bronte Creek, with a total area of approximately 2.64 hectares on the south side of the creek and 1.63 hectares on the north side of the creek. The open water in the south marsh is approximately 0.53 hectares. The marsh is contained within a natural valley corridor/ravine with steep slopes that are predominately shale, with an exposed shale outcrop at the north limit of the valley slope, immediately upstream of the marsh.

For the purpose of this study, I have chosen to focus on the south marsh and the adjacent valley slope due to accessibility of this area. I frequently walk the south marsh area as it is close to home and it’s bordered by Riverview Park with a walking path adjacent to the marsh. The path traverses the top of the slope on the southwest side of the marsh, and adjacent to the open water area on the southeast side of the marsh. The north marsh is mostly inaccessible as it borders private property.

I conducted my initial site visit on April 30, 2020. I have provided observations below summarized from my digital notes from my mobile device. I have included my digital field notes and some photographs following these observations.

Date: April 30, 2020

Time on site: 18:45

Time off site: 20:15

Temperature / Weather: 10°C / Cloudy, light fog, changing to light rain

Observations

Wildlife- Visual

• Blue Heron
• Double-crested Cormorant
• Mute Swan- nesting
• Red-winged Blackbird
• Common Grackle
• Canada Goose
• Beaver
• American Robin
• Grey Squirrel
• Gull species
• Horsefish- dead
• Black-crowned Night-Heron
• Red-necked Grebe- nesting

Wildlife- Audio

• Red-tailed Hawk Flicker
• Spring Peepers
• American Toad
• Northern Cardinal

Trees, Shrubs and Herbaceous

• White Oak
• White Pine
• Red-osier Dogwood
• Gray Dogwood
• Sugar Maple
• Ironwood
• Basswood
• Willow species
• Black Walnut
• Cattails

Invasive Species

• Common Buckthorn
• Vine species

Notes

• Study area from south limit of ravine in Riverview Park to exposed shale valley wall adjacent to and including the marsh on the southwest side of Bronte Creek
• The soil on the slopes was red shale with minimal ground cover
• Large trees along full length of the ravine slope- mainly deciduous with mix of coniferous, many with tree cavities observed
• Exposed shale valley wall with no vegetation at upstream limit of study site
• Storm sewer outlet near north limit of study area
• The most dominate understory was common buckthorn
• Granular pathway west of the ravine varying in distance from 4 to 10 m from the top of the ravine slope
• The marsh area was dominated by cattails with no Phragmites observed
• The dominant wildlife observed in the marsh included red-winged blackbird and common grackle
• A staff gauge was observed at the Marsh inlet/outlet with a depth noted as 0.58 m.
• The water in the marsh and the creek was clear

As noted in the field notes, the marsh is dominated by cattails (Typha spp.) in the wetted areas with a surface area almost four times the surface area of open water. There was abundant wildlife observed with red-winged blackbirds being the dominant species. The water was clear with no offensive odour.

The upland area is a steep valley slope with a mainly deciduous canopy cover of white oak (Quercus alba), maple species (Acer spp.), and eastern white pine (Pinus strobus). The understory consists of native species such as gray dogwood (Cornus racemosa), red-osier dogwood (Cornus sericea), and invasive species including common buckthorn (Rhamnus cathartica) and climbing vine species (unidentified). The ground cover is very limited with minimal grasses and herbaceous species identified as part of this initial site visit.

Three questions that I find interesting from my observations include:

1. How is the dominant understory of common buckthorn impacting the establishment of native understory/woodland species? What are the effects on the biodiversity of the ravine ecosystem as a result?
2. How has the marsh maintained minimal to no impact by invasive Phragmites and what are ways in which it can be prevented from being impacted in the future?
3. With the recent rise in Lake Ontario water levels, how does this affect the marsh ecosystem? More specifically, how might it impact the viability of breeding marsh birds or what sort of effects does it have on the aquatic vegetation?

References

Conservation Halton. 2002. Bronte Creek Watershed Study. Retrieved from: https://conservationhalton.ca/uploads/bronte_creek_watershed_study_-_a_-_final_-_2002.pdf