Turbidity results from the scattering of light in water by organic and inorganic particles; however, high turbidities usually are caused by suspended inorganic particles, particularly sediment. For several Alaskan lakes, we found that the depth to which 1% of subsurface light penetrated had a strong inverse correlation with sediment‐induced turbidity. We also developed a model that describes the decrease in primary production in shallow interior Alaskan streams caused by sediment‐induced turbidity. Euphotic volume in lakes correlated strongly with production of juvenile sockeye salmon (Oncorhynchus nerka). We also observed reduced abundance of zooplankton, macroinvertebrates, and Arctic grayling (Thymallus arcticus) in naturally and artificially turbid aquatic systems. Turbidity measurements correlated less consistently with measures of suspended sediment concentration (total nonfilterable residue), but provided an adequate estimator for use as a water quality standard to protect aquatic habitats.

Evidence both of trophic level changes induced by reduction in light penetration and of more direct effects of sediment and turbidity on aquatic life indicates that turbidity constitutes a valid and useful water quality standard that can be used to protect aquatic habitats from sediment pollution. A review of studies conducted in Alaska and elsewhere indicated that water quality standards allowing increases of 25 or 5 nephelometric turbidity units above ambient turbidity in clear coldwater habitats provide moderate and relatively high protection, respectively, for salmonid fish resources in Alaska. Even stricter limits may be warranted to protect extremely clear waters, but such stringent limits apparently are not necessary to protect naturally turbid systems.

A small group of northern fur seals (Callorhinus ursinus) including one male with two females, each with a small pup, and two lone males was discovered on Bogoslof Island, Alaska in the Bering Sea on 20 July 1980. This is the first evidence of breeding on Bogoslof, or on any island in the eastern Bering Sea other than the Pribilof Islands. We suggest that these fur seals require breeding islands adjacent to the continental shelf break where they are supported by the pelagic food web characteristic of the oceanic and outer shelf domains.