4-26 



sp. was not a dominant taxon; Rhodomonas sp. was a dominant in May 

 (1976) and Cryptomonas sp. was a dominant in April (1977) , October (1976 

 and 1977) and November (1976) (Table 4-2) . Abundance of Cryptophyceae 

 from 1974 through 1977 is presented in Figure 4-11; their apparent 

 reduced occurrence and dominance during the latter half of 1976 and in 

 1977 may have been an artifact resulting from the inclusion of members 

 of this group with the unspecified flagellate group during this period. 



In summary, phytoplankton cell densities and chlorophyll a 

 concentrations in New Haven Harbor from 1974 through 1977 were generally 

 lowest from October through January. During this period the diatoms, 

 Skeletonema costatum and Thalassiosira/Cyclotella spp., and microflag- 

 ellates usually dominated the phytoplankton assemblage. Other diatoms, 

 most notably Thalassionema nitzschioides , Leptocylindrus minimus, and 

 Asterionella spp. also appeared during this period. From February 

 through April, during which time cell densities and chlorophyll a 

 concentrations generally peaked, several diatoms and microf lagellates 

 achieved prominence. In 1975 during this late-winter/early spring 

 period, Thalassiosira/Cyclotella spp. , unspecified pennate diatoms and 

 flagellates, Thalassionema nitzschioides, Asterionella formosa, Caly- 

 comonas sp. , Chroomonas sp. , and Rhodomonas sp. were dominants. In 1976 

 a major bloom of Skeletonema costatum was responsible for the cell 

 density maximum in February and was succeeded by blooms of T. nitzschi- 

 oides , T. rotula, Schroderella delicatula and Asterionella glacialis in 

 March, and Leptocylindrus minimus and Calycomonas sp. in April. In 

 1911 , a major February bloom of Skeletonema costatum reoccurred, and 

 persisted into March when it was accompanied by unspecified flagellates, 

 Chaetoceros sp. , Thalassiosira nordenskioldii and Thalassiosira sp. , 

 and Phaeodactylum tricornutum; in April, of T. pseudonana, unspecified 

 flagellates, Olisthodiscus luteus, and the dinof lagellate, Katodinium 

 rotundatum, were dominant. In May from 1974 through 1976 Skeletonema 

 costatum and Thalassiosira/Cyclotella spp. were dominant; in 1976, 

 however, T. nitzschioides was also important. In May 1911, unspecified 

 flagellates and Olisthodiscus luteus as well as the diatoms, Thalas- 

 siosira sp. and Rhizosolenia spp., were dominant. During June and July, 

 Thalassiosira/Cyclotella species (including T. pseudonana) , dinoflag- 



