Ecology of Esquimalt Lagoon. 1. Nutrient inputs: the role of sewage
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An investigation has been conducted into the importance of sewage as a source of nutrients to a small, eutrophic lagoon. Weekly months of nitrate, ammonia and orthophosphate in lagoon water and in five streams discharging into the lagoon. It was found that lagoon fecal coliform counts were generally low (mean, <20/100 ml), while mean levels in the streams ranged from 17.9 to 2,931/100 ml. Animal sources were estimated to account for at least 40% of stream coliforms. Stream water was found to constitute a significant source of nutrients, primarily nitrate, to Esquimalt Lagoon and as such was deemed an important influence on the growth of phytoplankton there. Sewage was found to be the primary source of orthophosphate and ammonia but not of nitrate -- other sources accounted for at least 50% of the latter -- and since nitrate was considered to have the greatest ecological impact, it was concluded that sewage has only a partial influence on the trophic status of Esquimalt Lagoon.