Effects of bleached kraft mill effluent on macroinvertebrate and fish populations in weedbeds in a New Zealand hydro‐electric lake

Abstract

Abstract Effects of bleached kraft mill effluent on macroinvertebrate and fish communities in weedbeds were investigated in Lake Maraetai in December 1987 and February and March 1988. Water from polluted sites was highly coloured (absorbance at 270 nm: 0.25–1.80), had relatively high concentrations of suspended solids (5.2–25.0 g m‐3), high biochemical oxygen demand (2.1–12.3 g m‐3), but low dissolved oxygen concentrations (4.5–8.5 g m‐3) and Secchi disc visibility (< 0.8 m). In contrast, unpolluted lake water was relatively clear (Secchi disc visibility 1.2–1.5 m, absorbance at 270 nm: 0.09), biochemical oxygen demand was 1.5–2.1 g m‐3 and concentrations of dissolved oxygen exceeded 10.0 g m‐3. Invertebrate numbers were greatest at polluted sites where Chironomidae and tubificid oligochaetes predominated. Taxonomic richness and species diversity of invertebrates were highest at unpolluted sites where Gastropoda (6 species), and Chironomidae were numerically dominant. Overall catch of fishes was 1.5–2.8 t...