USGS Scientific Investigations Report 2012–5017  - Geomorphic Setting, Aquatic Habitat, and Water-Quality Conditions of the Molalla River, Oregon, 2009

Table 13. Diatom indicator species (guilds) in the Molalla River, Oregon, July and August 2010. 

[Percent relative abundance for each periphyton guild. Guild information from Porter (2008). Replicate samples from Goods Bridge in August were averaged. Bahls’ pollution tolerance from Bahls (1993)] 

Date	Site	Abundance expression (percent)	Nutrients		Oxygen and pH			Lange-Bertalot pollution tolerance		Bahls’ pollution tolerance
Date	Site	Abundance expression (percent)	(Low) Oligotrophic	(High) Eutrophic	High dissolved oxygen	Low- moderate dissolved oxygen	High pH	Less tolerant	Tolerant- very tolerant	Pollution sensitive	Pollution tolerant
July 30, 2010	Molalla River at Glen Avon Bridge	Biovolume	14	68	75	25	61	80	20	70	0.0
	Molalla River at Highway 211		9.1	78	76	24	89	77	23	70	0.0
	Molalla River at Highway 213		7.0	89	39	51	90	49	51	45	0.0
	Molalla River at Goods Bridge		8.4	88	80	0.3	74	99	0.3	88	0.0
	Molalla River downstream of Knights Bridge		7.4	64	43	56	62	49	50	42	0.0
	Molalla River at Glen Avon Bridge	Density	41	38	94	6.3	18	98	2.2	85	0.0
	Molalla River at Highway 211		37	51	90	10	42	93	7.8	76	0.0
	Molalla River at Highway 213		31	62	78	21	38	78	20	68	0.0
	Molalla River at Goods Bridge		44	44	98	1.0	20	98	1.0	85	0.0
	Molalla River downstream of Knights Bridge		19	57	68	29	27	82	17	69	0.0
Aug. 15, 2010	Molalla River at Glen Avon Bridge	Biovolume	14	62	76	24	59	94	6.3	60	0.3
	Molalla River at Highway 211		7.3	77	45	40	69	59	37	48	0.0
	Molalla River at Highway 213		11	57	79	20	63	75	20	68	0.0
	Molalla River at Goods Bridge		26	39	77	23	45	74	25	59	0.2
	Molalla R. downstream of Knights Bridge		13	49	89	11	40	83	17	65	0.5
	Molalla River at Glen Avon Bridge	Density	27	55	76	23	37	91	8.6	65	0.8
	Molalla River at Highway 211		28	56	80	19	27	82	14	67	0.0
	Molalla River at Highway 213		22	59	82	16	21	76	13	74	0.0
	Molalla River at Goods Bridge		47	31	92	7.0	18	93	5.6	79	0.7
	Molalla River downstream of Knights Bridge		41	21	94	6.0	14	92	7.7	77	0.8
Averages	July	Biovolume	9	77	63	31	75	71	29	63	0.0
	August		14	57	73	24	55	77	21	60	0.2
	July	Density	35	50	85	14	29	90	10	76	0.0
	August		33	44	85	14	23	87	10	72	0.5
Overall averages			23	57	76	21	46	81	17	68	0.2

Geomorphic Setting, Aquatic Habitat, and Water-Quality Conditions of the Molalla River, Oregon, 2009–10

Geomorphic Setting, Aquatic Habitat, and Water-Quality Conditions of the Molalla River, Oregon, 2009–10 