Biological Survey — Oswego Watershed 151 



Nannoplankton. Cyanophyceae. — Gloeothece and Gompho- 

 sphaeria were the two most abundant blue-green algae in Seneca 

 lake. They were both found in large numbers, especially between 

 0-25 meters, during August and September. Microcystis was fairly 

 common at the north station in August but occurred in only a few 

 samples at the south station. Gloeocapsa, Aphanocapsa and Meris- 

 mopedia were found in only a few samples at the north station, 

 but the latter two were found in large numbers at the south 

 station. 



Chlorophyceae. — Scenedesmus and Oocystis were the most 

 abundant green algae. Scenedesmus occurred only in traces in 

 June but during the other three months it was rather common. 

 Oocystis occurred in July and August. Other genera observed in 

 some of the samples were Characmm, Coelastrum, Crucigenia, 

 Gloetaenium, Pediastrnm, Quadrigula, Elactothrix, Cosmarium, 

 Closterium, Eudorina, Staurastrum and Tetraedon. The last six 

 of these genera were found in only one station. 



Oneida Lake. — The waters of Oneida lake were very rich in 

 plankton organisms during the entire period covered by the ob- 

 servations. 



Net plankton. Cladocera. — Daphnia was the most common 

 genus, occurring in greatest abundance from 0-3 meter depth, in 

 late June and September. Traces of Leptodora were found each 

 time, at 9-12 meters. Sida and Pseudosida were found in small 

 numbers on July 26 and later. 



Copepoda. — Diaptomus, most abundant from 0-3 meters, and 

 Cyclops, less common but more or less uniformly distributed be- 

 tween 0-6 meters, together with Nauplii were the only Copepoda 

 observed. There seemed to be a striking decline in the number of 

 Copepoda duing July. 



Kotifera. — Polyarthra was found in nearly every sample al- 

 though it was most abundant near the surface in June and again 

 in late August. Early in the season Anuraea occurred only near 

 the surface but later it was found at all depths, reaching its greatest 

 abundance on August 22. Notholca and Pleosoma were found 

 several times at various depths. Triarthra was found only once, 

 August 9, at 12-15 meters, and Asplanchna occurred from 0-12 

 meters on Sept. 6. 



Protozoa. — Ceratium was absent on June 28, appeared in traces 

 on July 12, and reached a maximum abundance, nearly 6000 per 

 liter, on August 23. By September 6, it had decreased in numbers. 

 It occurred at all depths later in the season but it was most abund- 

 ant between 0-6 meters. Dinooryon, which was very abundant 

 from 0-6 meters and less so in deeper water, showed a consistent 

 increase in numbers up to early August and then began to decline. 

 Mallomonas, found at all depths, was most abundant during late 

 July and August. Vorticella, mostly attached to colonies of Ana- 

 oaena, occurred near the surface early in the season, and during 

 late July and early August also appeared at the 3-9 meter depth. 

 Difflugia was found throughout the season, but, except for small 

 traces, only near the surface. 



