Sla Report Ss

Causal Effects of Increased Suspended Sediments on the Aquatic Biota of the Fraser River Watershed Introduction One of the largest sources of water pollution in the Fraser river watershed is suspended solids. Suspended solids consist of inorganic (silt, soil, clays, etc.) and organic (algae, zooplankton, bacteria and detritus) components (Bisson & Bilby 1982). The inorganic components of these suspended solids are often more harmful as is the case in the Fraser river system (Figure. 1). Primarily, these solids would be produced or originate from the agricultural and urban areas surrounding the Fraser River. At high ambient concentrations, it is possible for suspended solids to have adverse effects on the aquatic biota of a system (Bisson & Bilby 1982). Knowledge of the relationship between ambient concentrations and contaminating emissions is imperative to sustaining stable aquatic environments. This paper investigates the possibility of current and past effects of suspended solids on the aquatic biota of the Fraser River, estuary and surrounding oceanic waters. It is predicted that if there is an increase in suspended solids, there will be a changes in species abundance in the resident communities. Also, if any species abundance changes do occur, they will be more pronounced in the Fraser estuary.

Discussion The sources of suspended solids in the Fraser river system were found to originate from anthropogenic activities. The main sources are intrinsically linked to agriculture. It was found that land clearing for agriculture and associated soil degradation

over several years led to the uptake of large amounts of soil by rainwater annually. Similar studies report that approximately 2 billion tones of soil are lost each year in the surrounding area of the Fraser River and that 55% is agricultural runoff (Laws, pg 137, 2000). The majority of the agricultural runoff is nitrogen and phosphorus enriched material at 35% and 20% respectively (Laws, pg 133, 2000). Another source of pollution was identified as the logging practice which is considerable in the British Columbian region. The clearing of forest for lumber and associated road production, creates a floodplain due to the water sequestration usually performed by the trees being eliminated. Consequently, this allows for the underlying soil to be eroded and carried off to contribute to the sediment load of the river systems. Associatively, when the trees are formed into logs and floated on the river, wood debris which displays a high BOD upon decomposition is created and accumulates in the sediment. One further cause to high sediment load in the fraser river watershed is the anthropogenic waste and storm water from urban areas. Ecological ramifications of these water pollution sources are readily apparent upon study. The salmon fisheries are largely affected due to suspended sediments acting directly on free living fish either by killing them or reducing their growth rate and disease resistance (Figure. 2). This can occur due to suspended solids interfering with the development of eggs and larvae, modification of natural migrations and reducing food available to the salmon (Lisle and Lewis 1992). A similar effect is depicted when studying periphyton. Land runoff due to cleared forests in combination with sewer inputs into the system can create a high flow within the Fraser river systems. High flow and suspended sediments can have adverse effects on light penetration thus, decreasing algal

production, and if flow is fast enough, scour algae from substrates (Newcombe and Macdonald 1991). In direct association with the effect on periphyton, benthic invertebrates are impacted due to the reduction in periphyton population. Additionally, suspended sediments can reduce the filter feeding efficiency of the macro-invertebrate if sediments clog the feeding structures. These effects, if consistent, would ultimately lead to reduced growth rates of the macro-invertebrates and periphyton of the Fraser River watershed (Langer 1980). The Frazer estuary is a fragile environment with inhabitants that are only able to coincide with very finite salinities changes. Due to this fragile environment, it is feasible to assume that any slight change may push the equilibrium too far and thus be readily identifiable in the aquatic inhabitants of the system. This was investigated in a study by Burd in 2008 in which the heavily deposited areas on the south arm of the estuary underwent a shift from bivalves to polychaetes as the dominant filter feeder. This research correlates with research done by Monbet in 1992 in which the large amounts of suspended solids were found to alter the natural salt wedge in the estuary and thus, the dominant fauna. Furthermore, upon investigation of the Georgia strait surrounding the estuary, elevated sulphides in the outflow from the river have stimulated enrichmentrelated invertebrate faunal changes (MacPherson et al. 2007). This combined research provides support for the hypothesis and presents suspended solids as a possible effecter in the Fraser River system. Remediation of the practices that have lead to the increased suspended sediments can be accomplished through riparian forests, conservation tillage and combined sewer and storm water systems. The installation of riparian forests between agricultural areas

and the river systems can be instrumental in reducing agricultural runoff. A study done by Peterjohn and Correll in 1984 on a standard farming plot in which the installed riparian forest retained 89% of the nitrogen in the runoff and 80% of the phosphorus. This practice, coupled with a change in farming practices to conservation tillage in which cultivation is done in the fall to allow a cover crop to grow over the winter which protects the soil and decreases soil runoff due to less degradation (Gaynor and Findlay 1995), can reduce sediment loads in the Fraser River watershed. Additionally, the combination of waste and storm water sewer systems can reduce suspended sediment and BOD content by 85% (Laws, pg 142, 2000). The incorporation of all three of these practices could potentially lower fraser river sediment loads a substantial amount allowing for a sustainable river system and overall biotic health of the Fraser River watershed.

Conclusion The results of the study support the hypothesis in that obvious species abundance changes were observed in the Fraser River watershed due to increased suspended solids present in the system. Similarly, these findings support both predictions in that change in species abundances were identified and were especially evident in the Fraser estuary. Possible remediation of the increased sediment loads are perceived through methods such as riparian forests, combined sewer systems and conservation tillage. Occurrences like this can be avoided in the future if scientists or ecological managers were provided with information that related the magnitude of pollution episodes to effects on aquatic ecosystems so effects of new development schemes can be

properly evaluated for their potentially ecologically harmful side-effects. Unfortunately, this cannot be accomplished with the current implicit concentration-response model of suspended sediment effects. Implementation of a model which could provide scientists with this knowledge is possible, and restructuring of the economy before sustainable management mindset present in the government today is mandatory for the continued health of the Fraser River watershed.

Appendix

Figure. 1: Visual depiction of the Fraser River watershed

Figure. 2: relationship between log (ln) of suspended sediment concentration and severity of impact on salmonid and aquatic invertebrates.

References Bisson P. A, Bilby R. E. 1982. Avoidance of suspended sediment by juvenile coho salmon. N.Amer. J. of Fish Manag. 2:371-374 Burd B.J, MacDonald R.W, Johannesson S.C, van Roodselaar A. 2008. Responses of subtidal benthos of the strait of Georgia, British Columbia, Canada to ambient sediment conditions and natural and anthropogenic depositions. Mari. Env. Res. 66: S62-S79 Crosbie B, Chow-Fraser P. 1999. Percentage land use in the watershed determines the water and sediment quality of 22 marshes in the Great lakes basin. Can. J. Fish. Aquat. Sci. 56: 1781-1791 Gaynor, J.D., and Findlay, W.I. 1995. Soil and phosphorus loss from conservation and conventional tillage in corn production. J. Environ. Qual. 24: 734–741. Gobas F.A.P.C, Pasternak J, Lien K, Duncan K.R. 1998. Development and field validation of a multimedia exposure assessment model for waste load allocation in aquatic ecosystems: application to 2,3,7,8-Tetrachlorodibenzo-p-dioxin and 2,3,7,8Tetrachlorodibenzofuran in the Fraser River watershed. Envir. Sci. Technol. 32: 24422449 Langer, O. E. 1980. Effects of sedimentation on salmonid stream life. In K. Weagle, editor. Report on the technical workshop on suspended solids and the aquatic environment. Department of Indian Affairs and Northern Development, Contract Ott-80019,Whitehorse, Yukon Territory. Laws E.A. Aquatic Pollution: an introductory text. John Wiley & Sons Inc. 2000. Lisle E.T, Lewis J. 1992. Effects of sediment transport on survival of salmonid embryos in a natural stream: a simulation approach. Can. J. Fish. Aquat. Sci. 49: 2337-2344 Monbet Y. 1992. Control of phytoplankton biomass in estuaries: a comparative analysis of microtidal and macrotidal estuaries. Estuaries. 15(4): 563-571 Newcombe C.P, MacDonald D.D. 1991. Effects of suspended sediments on aquatic systems. N. Amer. J. of Fish. Manag. 11: 72-82 Peterjohn, W.T., and Correll, D.L. 1984. Nutrient dynamics in an agricultural watershed: observations on the role of a riparian forest. Ecology, 65: 1466–1475.