parts of the Sound. This approach demonstrates the significant 
differences in the toxicity of sediments from the urban waterways as 
compared to that of the central basin and rural bays. 
Also, samples considered to be toxic are those in which 75% or fewer of 20 
amphipods survive after ten days' exposure to the sediments. Areas in 
which a half or more of the samples were toxic are: off the Denny Way CSO 
in Elliott Bay, off the mouth of Whatcom Creek Waterway in Bellingham Bay, 
much of Sinclair Inlet, inner half of Everett Harbor, the lower Duwamish 
Waterway, Hylebos and City Waterways in Commencement Bay, a part of outer 
Quilcene Bay, much of Case Inlet, part of Eagle Harbor, off south 
Bellingham Bay and outer Dabob Bay. Areas in which less than half the 
samples were toxic include: Sequim Bay, Possession Sound, outer Elliott 
Bay (including the Four Mile Rock dump site), outer Sinclair Inlet, off 
the west shore of Whidbey Island, outer Commencement Bay, all of East 
Passage in the central basin and most of inner Bellingham Bay. 
Sediment samples that are toxic to these amphipods are often collected 
from areas that are most contaminated with toxic chemicals. However, the 
amphipods used in this bioassay are also apparently sensitive to the 
amount of organic matter and fine particles in sediments (they normally 
are found living in sandy habitats). So some of the "toxic" response 
observed in the bioassays may be due, in part, to these natural 
properties of sediments that these animals find intolerable. 
Table 2. Synopsis 
of sediment bioassays performed in Puget Sound. 
Biological Group/ 
Media Tested 
Type of Measurement 
Where Observed 
Oyster larvae/ 
elutriates 
96-h mortality 
and abnormality 
Parts of: Tacoma Waterways, 
Bellingham Bay, Everett Harbor, 
Duwamish, Sinclair Inlet 
Amphipod/bul k 
sediments 
10-d mortality 
Parts of: Tacoma Waterways, 
Elliott Bay, Bellingham Bay, 
Everett Harbor, Eagle Harbor, 
Quilcene Bay, Case Inlet 
Bacteria /n\ 
(Microtox'^M/ 
organic extracts 
5-min. EC 50 for 
reduction in bio¬ 
luminescence 
Parts of: Duwamish, Tacoma 
Waterways, Eagle Harbor 
Cultured trout 
cells/organic 
extracts 
Anaphase aberrations 
and cytotoxicity 
Parts of: Everett Harbor, 
Bellingham Bay, Elliott Bay, 
Duwamish, Tacoma Waterways, 
inner Sinclair Inlet, Birch Bay 
01 igochaete/ 
elutriates 
Altered respiration 
rate 
Parts of: Elliott Bay, Tacoma 
Waterways, Duwamish, off West 
Point 
35 
