Effects of sedimentation and periphyton communities on embryonic rainbow smelt, Osmerus mordax.

摘要

The decline of anadromous rainbow smelt (Osmerus mordax) populations has been suspected to be linked to anthropogenic causes. Increased runoff from agriculture and urbanization has led to additional sediment inputs and eutrophying compounds in rivers. The aim of this study was to assess the survival of embryonic rainbow smelt from fertilization through hatching under varying levels of sedimentation (0.00, 0.25, 1.00, and 6.00 g per 45.6 cm 2) and with periphyton communities of different biomass and algal composition. Additionally, embryo survival was assessed when cultured on periphyton in combination with sterilized sediment or eutrophying compounds (nitrates and phosphates). Oxygen consumption was monitored from embryos cultured alone, on periphyton layers, and under sediment. Survival was significantly reduced under the highest sediment treatment and attributed to low oxygen availability to the embryos. Embryonic survival was also significantly reduced on the highest periphyton biomass (251.5 g/m2 dry weight, 15.7 g/m 2 ash free dry weight), and periphyton containing a high cyanobacteria content (50%). These results suggest that embryonic survival could be reduced in rivers with heavy sedimentation or a high standing biomass of periphyton.