Acute Toxicities of Spruce and Hemlock Bark Extracts to some Estuarine Organisms in Southeastern Alaska

Abstract

Sitka spruce bark extracts were found to be toxic to adult and larval pink shrimp (Pandalus borealis) and larval Dungeness crab (Cancer magister). Sitka spruce and western hemlock bark extracts were found to be toxic to pink salmon (Oncorhynchus gorbuscha) fry. For salmon fry, toxic effects were observed as soon as 3 h after exposure to hemlock bark extracts. After a 96-h exposure, 50% of the test fry were killed at a concentration of 56 mg/liter (96-h LC50). With a 96-h exposure of spruce extracts, 50% of the fry were killed at concentrations of 100–120 mg/liter.Spruce bark extracts were consistently toxic to all invertebrates tested. The 96-h LC50 with larval shrimp, adult shrimp, and larval crabs were 415, 205, and 530 mg/liter, respectively. Using loss of swimming as the criterion, the 96-h EC50s for larval shrimp and larval crabs were 155 and 225 mg/liter, respectively (EC50: median effective concentration). Spruce bark pulp was found to be 2–6 times more toxic than extracts to shrimp larvae.