Invertebrates field collections

Measurements of effluent concentration must also be taken at the effluent outfall and at fish and benthic invertebrate field collection sites during the surveys. 

Levels of total organic carbon (TOC) followed a gradient pattern, and ranged from 4.9% at the near-field to 0.7% in the far-far field (mean 3.1%), primarily due to historical fibre deposits. Oil contamination was present in the near-field and far-field sediments. Triplicate samples were collected using a standard Ponar grab and pooled. Invertebrates were preserved until they were counted and identified. Statistically significant differences between reference and exposure areas were observed for three of the five invertebrate community indices calculated (Tab. 8). 

The benthic invertebrate study design used at the Provincial Papers site was a Multiple Control/Impact study including near-field (NF) and far-field (FF) areas in both exposure and reference areas. The NF exposure area was located as close as possible to the outfall (Fig. 2) in the area showing elevated conductivity, while the FF exposure area was located approximately 1000 m from the NF area. A petite Ponar was used to collect duplicate samples at six stations in each exposure and reference area. Substrates in the reference and exposure areas were different the exposure area was 100% organic, comprised of wood chips, while the reference area was dominated by silt and clay with small amounts of fine sand at two stations. 

Any effects on populations may ultimately be manifested as effects on communities because, by definition, communities are collections of interacting populations of several species (e.g., an aquatic community may consist of populations of fish, worms, plants, insects). Individual populations within a community may interact by competing for resources (food, habitat, etc.) or by predator/prey relationships. Environmental contaminants can affect the structure of communities as well as the interactions of species within them. For example, it is well known that exposure to chemicals may cause a reduction in community diversity (e.g., relative number of species), and changes in community composition. In addition, the trophic structure of fish and invertebrate communities may also be affected by exposure to anthropogenic chemicals. Changes in community structure and diversity may be determined by field sampling or manipulative studies. Alternatively, computer simulations using food web or linked population models may be used to assess community-level effects. 

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