THE AQUATIC ENVIRONMENT
Description
The following is a summary of section 4.4 "Description of the existing environment - Aquatic Environment" of the New Darlington Project Environmental Impact Statement document, as well as the "Aquatic Environment – Existing Environmental Conditions Technical Support Document, New Nuclear - Darlington Environmental Assessment" document. The Aquatic environment at the new project site is comprised of various wetland ponds, Darlington Creek and its intermittent tributaries, an intermittent Lake Ontario tributary and the nearshore area of lake Ontario. Baseline or existing conditions were described for both the aquatic habitat and biota present on these aquatic features.
ON-Site Features
Lake Ontario Nearshore Environment
The site study area also comprises part of the north shore of lake Ontario. This nearshore environment is a very important aquatic feature at the Darlington site. It is quite exposed to wind, waves and currents, making it a harsh and high-energy environment. The shore's substrate is characterized by cobble and gravel, while underwater substrates are comprised of glacial till, bedrock and boulders. There is little cover for fish and invertebrates and plant life is limited to attached algae, which is why this area is only used as permanent habitat by only a few species.
Longshore and offshore currents influence sediment transport and deposition. These currents have already been present prior to the development of the DNGS. The effects of the diffuser discharge on the lake's currents are only localized around the diffuser's area and it is not believed that the DNGS has had an significant effect in current directions and speeds since 1990.
The nearshore ambient temperatures in this region are seasonal. It can reach temperatures of up to 20 degrees C during the July/August, and stay around 0 - 4 degrees C from November to April.
The following is a summary of section 4.4 "Description of the existing environment - Aquatic Environment" of the New Darlington Project Environmental Impact Statement document, as well as the "Aquatic Environment – Existing Environmental Conditions Technical Support Document, New Nuclear - Darlington Environmental Assessment" document. The Aquatic environment at the new project site is comprised of various wetland ponds, Darlington Creek and its intermittent tributaries, an intermittent Lake Ontario tributary and the nearshore area of lake Ontario. Baseline or existing conditions were described for both the aquatic habitat and biota present on these aquatic features.
ON-Site Features
- Darlington Creek is a lake Ontario tributary that has been affected by channelization and realignment due to the accommodation of road and rail corridors, as well as by the operation of a nearby cement company. The quality of habitat at Darlington creek varies greatly, with its upper reaches having much better quality habitat than its lower reaches which are located near the entrance to Lake Ontario. The upper reaches have clear water, cobble and gravel, while the lower reaches are channelized and very murky. The fish community is comprised principally by warm water species, although the presence of rainbow trout has been confirmed as well. The channel is blocked by large amounts of debris, which create barriers to upstream migration.
- Three wetland ponds (Polliwog, Treefrog and Dragonfly) present at the site were constructed by OPG to promote on-site biodiversity. These areas do not support fish and can become completely dry during extended periods of dry weather. For this reason they are not being considered in the EIA as direct fish habitat. Furthermore, because of their lack of connectivity between each other and on-site watercourses such as Darlington Creek, they are not considered indirect fish habitat and do not fall under the fish habitat protections of the federal Fisheries Act. These ponds will be destroyed during the construction phase of the project.
- Coot's pond was built by OPG as a stormwater runoff and settling pond. Even though it was intended to be fish-free in order to support amphibian production, northern redbelly dace have become established and have become very abundant. However, amphibian reproduction is still supported. The pond has been managed according to the Darlington Nuclear (DN) Biodiversity Program and provides wetland and terrestrial contribution to the DN site. This is why the EIA considers Coot's pond a valuable on-site aquatic habitat.
- Two intermittent tributaries of Darlington Creek are comprised of marshy areas covered in cattail, reed canary and many other emergent wetland species. The EIA doesn't consider these tributaries as sensitive habitat because they don't support fish and lack permanent aquatic habitat. However, they are considered as indirect fish habitats since they have the function of conveying water and nutrients to downstream fish communities.
- One lake Ontario tributary also present in the site is considered direct fish habitat because beaver ponds provide permanent aquatic habitat even during periods where there is no water flow.
Lake Ontario Nearshore Environment
The site study area also comprises part of the north shore of lake Ontario. This nearshore environment is a very important aquatic feature at the Darlington site. It is quite exposed to wind, waves and currents, making it a harsh and high-energy environment. The shore's substrate is characterized by cobble and gravel, while underwater substrates are comprised of glacial till, bedrock and boulders. There is little cover for fish and invertebrates and plant life is limited to attached algae, which is why this area is only used as permanent habitat by only a few species.
Longshore and offshore currents influence sediment transport and deposition. These currents have already been present prior to the development of the DNGS. The effects of the diffuser discharge on the lake's currents are only localized around the diffuser's area and it is not believed that the DNGS has had an significant effect in current directions and speeds since 1990.
The nearshore ambient temperatures in this region are seasonal. It can reach temperatures of up to 20 degrees C during the July/August, and stay around 0 - 4 degrees C from November to April.
Aquatic Biota
The EIA places emphasis on benthic invertebrates and fish, as their responses are usually understood and they are generally the subject of management and conservation objectives.
Phytoplankton and zooplankton are not residents at the DN site, but they are constantly being carried by lake currents and they can have brief interactions with the habitats present on the site.
The nearshore environment supports a limited density and diversity of benthic invertebrate communities, mostly due to the hard substrates and hight energy environment. Since the mid-1990's the benthic communities have been changed due to the invasion of exotic quagga and zebra mussels. These mussels are able to persist in the nearshore's harsh conditions and they have had a great impact in the aquatic environment of Lake Ontario by altering nutrient flow, food webs and productivity, as well as promoting the proliferation of attached algae along the shoreline. Low invertebrate densities have been recorded on the New Darlington proposed lake infill zone. Sampling in this area has also indicated the presence of the bloody red shrimp, an invasive species that has the potential to cause great ecological harm in Lake Ontario.
The fish community of Lake Ontario is relatively sparse. The nearshore environment is characterized by a diverse and seasonally dynamic mix of resident and migratory fish species. These species form part of both the benthic and pelagic food webs. However, most of them migrate over large areas of Lake Ontario and are not residents to the site study area. The round goby, an exotic benthic fish that has recently colonized Lake Ontario, is one of the few residents at the site and the most common species found. Several other species that have been recorded during OPG's fish community monitoring in the vicinity of the DNGS are the white sucker, lake trout, brown trout, round whitefish, walleye, sculpin sp., alewife, emerald shiner, rainbow smelt and lake chub. No fish species at risk were recorded during OPG's monitoring. However, some fish species at risk (SAR) are known to reside in lake Ontario and therefore there is a possibility that they may be found on the nearshore area at the DN site. These include the deepwater sculpin (Special Concern), lake sturgeon (Threatened), Atlantic salmon (Extirpated) and American eel (Special Concern). The site study area, however, does not contain critical habitat for these species.
The EIA places emphasis on benthic invertebrates and fish, as their responses are usually understood and they are generally the subject of management and conservation objectives.
Phytoplankton and zooplankton are not residents at the DN site, but they are constantly being carried by lake currents and they can have brief interactions with the habitats present on the site.
The nearshore environment supports a limited density and diversity of benthic invertebrate communities, mostly due to the hard substrates and hight energy environment. Since the mid-1990's the benthic communities have been changed due to the invasion of exotic quagga and zebra mussels. These mussels are able to persist in the nearshore's harsh conditions and they have had a great impact in the aquatic environment of Lake Ontario by altering nutrient flow, food webs and productivity, as well as promoting the proliferation of attached algae along the shoreline. Low invertebrate densities have been recorded on the New Darlington proposed lake infill zone. Sampling in this area has also indicated the presence of the bloody red shrimp, an invasive species that has the potential to cause great ecological harm in Lake Ontario.
The fish community of Lake Ontario is relatively sparse. The nearshore environment is characterized by a diverse and seasonally dynamic mix of resident and migratory fish species. These species form part of both the benthic and pelagic food webs. However, most of them migrate over large areas of Lake Ontario and are not residents to the site study area. The round goby, an exotic benthic fish that has recently colonized Lake Ontario, is one of the few residents at the site and the most common species found. Several other species that have been recorded during OPG's fish community monitoring in the vicinity of the DNGS are the white sucker, lake trout, brown trout, round whitefish, walleye, sculpin sp., alewife, emerald shiner, rainbow smelt and lake chub. No fish species at risk were recorded during OPG's monitoring. However, some fish species at risk (SAR) are known to reside in lake Ontario and therefore there is a possibility that they may be found on the nearshore area at the DN site. These include the deepwater sculpin (Special Concern), lake sturgeon (Threatened), Atlantic salmon (Extirpated) and American eel (Special Concern). The site study area, however, does not contain critical habitat for these species.
For more information, please refer to the Aquatic Environment - Existing Environmental Conditions Technical Support Document