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Introduction

Climate change and human impacts continually effect coastal wetlands and ecology in British Columbia. There are multiple factors effecting the biological stability of the Fraser River estuary in British Columbia in general, and the salmon populations in particular. Some of the major influences on these costal estuaries are sea level rise, invasive species, pH changes and temperature rise. Specifically, these factors affect the salmon populations. Estuaries are vulnerable ecosystems critical for survival of the young stages in a salmon’s life. Global warming negatively affects the salmon’s food supply. Additionally, the increasing aquaculture has caused many environment issues for the Fraser River estuary. Estuaries are fragile ecosystems which house and bear salmon populations, however, the shift in food supply caused by global warming and the constant development of human activities threaten the stability of the salmon species.

How salmon benefit from estuaries

Estuaries provide essentials for young salmon such as food and protection from predators. This protection comes from high turbidity and vegetation. Estuaries are transition zones where juvenile salmon can grow rapidly and physiologically adapt to the saltwater environment. The early life stages of salmon par are critical for the species, it will determine whether they will live long enough to be reproducing adults or die off due to poor development. The Fraser River estuary provides food and production to young salmon par, presenting the species with the chance to develop into healthy, reproducing fish.

Human Impact

The rapid growth and development of human demand in aquaculture significantly affects the overall environmental condition, and populations that inhibit the Fraser River estuary. Even though estuaries are recognized globally as one of the world’s most productive ecosystems, they are also some of the most threatened ecosystems. A common threat to estuaries originates within the watersheds that drain into them. The development for agriculture, forestry, residential and industrial land has caused an increase in sediment, debris, nutrient and pollutant levels in estuaries which can suffocate plants and animals and cause hypoxia or anoxia conditions in the waters. Additionally, activities such as logging, aquaculture, dredging and vessel traffic can cause loss or degradation of habitat, contamination of waters, erosion of sediment and invasion by foreign species. Salmon, their food and habitat, can all be greatly altered by these human activates. Floodgates are another example of human caused stress on the salmon’s environments. Floodgates are known to alter organism’s community structures by impounding water and acting as a physical barrier to migratory species. This means that when the salmon attempt to migrate downstream towards the estuary, they may not be able to, due to these floodgates. This can hinder the salmon’s chances of having enough food, which can eventually have a negative effect on the salmon’s development.

Algae Blooms

A large portion of the salmon’s diet includes algae. These algae blooms usually occur in late summer near shore areas like estuaries, but due to warming in the global climate, algae blooms have been occurring earlier in the summer season than they once did. This shift in blooms have greatly affected the 9000 salmon par that are being released from the hatcheries and migrating towards estuaries in the late summer because they have a much more limited food sources than the salmon that are being released and migrating earlier in the season. Therefore, salmon stocks that leave natal streams and migrate to estuaries earlier in the summer season may be favoured over later-migrating fish. Reviewing the data and charts in reference “Mapping cumulative impacts to coastal ecosystems in British Columbia”. , there is a high intensity of large vessel activity in the Fraser River estuary. Research shows that these vessels are a contributing factor in algae bloom abnormalities because they emit greenhouse gases. Therefore, because these vessels threaten algae blooms, they also threaten the chance of survival for the salmon.

Sea Level Rise

Estuary in BC

Climate change and human impacts effect sea level rise which is one of the major risks put on costal estuaries and ecosystems. SLR and storms combined with costal developments may put important habitats at danger, like intertidal zones, low lying areas near estuaries. Implications of urbanization like costal development or dam construction of rivers affects SLR. Costal development intensifies costal erosion and amplifies SLR, and also has reclaimed estuary land for development which cause the destruction of many habitats in these costal estuaries. Damming of rivers reduce the amount of nutrient supply needed for the survival of many species, it interferes with the natural sediments and can cause the river course to change. When nutrients to species are cut off it can reduce productivity in estuaries, which can hinder arrival time of some species like migratory fish and birds that correspond with the estuary’s productivity when it is at its highest. Dam construction causes the ecosystems to become flooded, which is destroying communities. Fluctuating water levels are destroying habitats, due to changes in the flood system. Seawalls/dams can prevent estuaries for moving inland so they become extremely vulnerable to SLR which can fluctuate the salinity levels and habitats can cease to exist. SLR is forcing estuaries to drift landward which can enhance stress on these ecosystems, the enhanced stress can cause native species to lose against alien species. The intensity of storms also affects SLR which and both of them affect costal erosion which leads to the destruction of habits. If SLR is rapidly increased it can be a major issue, since it often destroys many estuaries and their habitats.

Invasive species

Alien species both plants and animals is a common risk to costal estuaries. Native species have to fight to stay dominant, over the alien species. Some alien species positively contribute to the ecosytsems, like in the Straight of Georgia aquaculture in BC. Some species were oysters, mussels and scallops, that were introduced to help. Majority of the time invative species being brought is accidental, by marine traffic, like ships and ballast water on these ships. Ships coming into ports are carrying ballast water which are containing many invasive species, like green crabs and causing them to become more numerous. Some more invasive species that are becoming more common in costal estuaries are creeping bent-grass, purple loose-strife, English cordgrass, these are more frequently replacing native species. Another way that alien plants and animals are initiated is by climate change and contaminants which cause stress on the native species. When native species become stressed they may no longer be able to fight against the alien species, to dominant. The alien species may also adapt to the climate change better than the native species do, which can also cause the aliens species to take over. Storms are one way in which native species undergo stress, which could result in them being unable to compete for the environment. Stress can also be caused by a river changing course, temperature rise and salinity level change. Degraded habitats can become more susceptible to invasion of alien species. Some other common causes of stress to costal ecosystems are storms, floods and drought years.

pH

Ocean acidification drivers

Acidification of costal waters, caused by CO2 increasing affects biochemical cycling and chemical species. One consequence of low pH can be dissolution of carbonate shells. Some species at risk are bivalves, corals, calcareous plankton and some benthic species. Benthic species are extemely important to these types of environments, they contribute greatly to the food chain, since they consume dead organic matter and are consumed by many other species. They also produce oxygen , increase activity and clean water which allows light to enter. A decrease in pH also affects fish survival, by reducing nutrience availability. CO2 increasing has caused the waters acidity levels to increase, which has reduced some species and destroyed communities. Eutrophication helps with this process and makes the costal water more prone to acidification. Large amounts of algae in water also has increased acidity because it consumes O2 and produces CO2, which can further reduce pH. High water temperatures and reduced oxygen together, with reduced pH cause more stress on species.

Temperature Change

Temperature change and circulation patterns affect costal zones, which also affects costal ecosystems. Climate change, like increasing levels of greenhouse gases are causing the sea temperatures to rise. Heating of the sea is unevenely distributed which can intensely affect the sea currents and ecosystems. Temperature increase combined with circulation can cause extreme changes, things like drought years. Which can modify the amount of discharge, which results in high salinity levels in costal water and landward extension, both which can greatly damage a ecosystem and its species. Drought years can also bring about stress, making the native species more vulnerable to invasion of alien species. The turbidity of water can also be affected by a change in temperature. Turbidity fluctuates with seasons, but with the climate change causing warming, turbidity has also been increasing in all seasons. As the water temperatures increase, the periods of bioturbation have lengthened, which has raised turbidity levels. This could affect productivity because in some seasons the light intensity could be decreased, which could harm some species like benthic species or plankton. Turbidity levels can affect nutrients supplied to ecosystems and how much oxygen is dissolved. Climate change can cause high amounts of precipitation and runoff often to bring in pollutants and nutrients to costal zones which can alter biochemical processes, but when the water is warmer, bioactivity and the readiness of pollutants are amplified which increases the threat of toxics costal species. Discharge of rivers are strongly seasonal, with peaks being either small of large depending on the sediment fed to it. When the hydrological cycle patterns are disrupted it can severely damage the ecosystems.

Conclusion

Salmon are heavily dependent on estuaries for food and protection. Estuaries, like the one found in the Fraser River, provides essentials for young salmon par to develop into healthy, reproducing adults. However, the negative repercussion of human activities, such as aquaculture and land development, threaten salmon populations. Global warming has also caused the species food supply availability to shift and manmade floodgates has disenabled salmon to migrate throughout the river systems as needed. Sea level rise, invasive species, pH and temperature changes are some additional factors threatening the ecosystems and its population. The Fraser River estuary is a delicate ecosystem that supports many aquatic lives, such as salmon. Without proper efforts to maintain the natural environment of this ecosystem a major biological delicacy could indeed be lost.

References

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https://wwf.ca/wp-content/uploads/2020/03/Estuaries-of-British-Columbia_january-2013-1.pdf

2.^ British Columbia Ministry of Environment. (2006). Estuaries in British Columbia. Retrieved from BC Conservation Data Centre Ministry of Environment: https://www2.gov.bc.ca/assets/gov/environment/plants-animals-and-ecosystems/species-ecosystems-at-risk/brochures/estuaries_bc.pdf

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https://portals.iucn.org/library/sites/library/files/documents/MRN-013.pdf#page=44

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