Phytoplankton of Owhi Lake

Spring phytoplankton (May 8, 1987) of Owhi lake were dominated by centric diatoms (including Cyclotella sp.). They represented approximately 50 to 97 % of the population at all depths sampled. The blue-greens (Chlamydomonas and two unidentified species) were a minor component in the spring phytoplankton.

The unicellular blue-green alga Chroococcus sp. dominated the fall phytoplankton (September 16, 1986) of Owhi Lake. Chroococcus constituted approximately 50% to as high as 92% of the population. Associated algae occurred in significantly lower percentages. These included the blue-greens Gloeotrichia echninulata, Lyngbya, and Oscillatoria sp and the diatom Nitzschia

.

Trophic status of Owhi Lake based on phytoplankton analysis.

Members of the Owhi Lake phytoplankton assemblages considered common in eutrophic conditions are Anabaena and Gloeotrichia echinulata. Some species of Oscillatoria are commonly found in mesotrophic or hypertrophic conditions. Certain species of Cyclotella are considered oligotrophic; others mesotrophic. Many species of the diatom Nitzschia are typical of eutrophic waters.

The phytoplankton assemblages identified from the Owhi Lake collections contain several taxa tyical of meso- to eutrophic conditions. The abundance of these algae in Owhi Lake indicates that the lake is eutrophic.

Literature Cited

OWHI LAKE PHYTOPLANKTON FOR SPRING AND AUTUMN 1987
Autumn, 16 September 1987
Station A
Sample Depth	Phytoplankton	Algal Cells per ml	Percentage
Surface	Chroococcus sp.	145	66%
	Oscillatoria sp.	14	21%
	pennate diatoms	4	6%
	unicellular green alga	4	6%
	Achnanthes sp.	2	2%
1 Meter	Oscillatoria sp.	44	73%
	Nitzschia sp.	8	12%
	Chroococcus sp.	16	10%
	Chroococcus sp.	21	2%
	unicellular green alga	2	2%
5 Meter	Chroococcus sp.	155	88%
	unicellular green alga	4	6%
	Anabaena sp.	3	4%
	Trachelomonas sp.	2	2%
Station B
Sample Depth	Phytoplankton	Algal Cells per ml	Percentage
Surface	Chroococcus sp.	145	66%
	Oscillatoria sp.	14	21%
	pennate diatoms	4	6%
	unicellular green alga	4	6%
	Achnanthes sp.	1	2%
1 Meters	Oscillatoria sp.	44	73%
	Nitzschia sp.	7	12%
	Chroococcus sp.	16	10%
	Chroococcus sp.	21	2%
	unicellular green alga	1	2%
5 Meter	Chroococcus sp.	153	49%
	Gloeotrichia echinulata	40	38%
	Oscillatoria sp.	11	10%
	Nitzschia sp.	2	2%
	Trachelomonas sp.	2	2%
10 Meter	Chroococcus sp.	117	100%
Spring ,8 May 1987
Station A
Sample Depth	Phytoplankton	Algal Cells per ml	Percentage
Surface	centric diatoms	10	92%
	Cryptomonas sp.	1	3%
	spherical green alga	1	3%
1 Meter	centric diatom	3	42%
	Anabaena sp.	3	34%
	spherical blue-green alga (tetrad)	1	16%
	Synedra sp.	1	4%
	Gloeocystis gigas	1	4%
5 Meter	Cyclotella sp.	20	82%
	pennate diatoms	2	7%
	Schizochlamys sp.	1	5%
	unidentified blue-green alga	1	4%
10 Meter	Cyclotella sp.	75	65%
	centric diatoms	24	21%
	unidentified filamentous blue-green alga	9	7
	Anabaena sp.	3	3%
	Synedra cf. acus	2	2%
Spring, 8 May 1987
Station B
Sample Depth	Phytoplankton	Algal Cells per ml	Percentage
Surface	Cyclotella cf. kutzingiana	8	58%
	Chlamydomonas sp.	4	27%
	Gloeocystis gigas	1	8%
	Synedra acus	1	4%
	centric diatom	1	4%
1 Meter	Cyclotella sp.	7	64%
	Chlorella sp.	1	9%
	Synedra cf. acus	1	9%
	centric diatom	1	5%
	unicellular blue-green alga	1	5%
	pennate diatom	1	5%
	Gloeocystis gigas	1	5%
5 Meter	centric diatoms	21	53%
	Spherical blue-green alga	7	18%
	Anabaena sp.	6	15%
	Schizochlamys sp.	4	10%
10 Meter	centric diatoms	175	97%
	small unidentified green alga	2	2%