4-15 



dance pattern was characterized by low densities (usually less than 10 



cells/liter) from October through February and higher levels from March 



through September; peak densities (2 x 10 to 2 x 10 cells/liter) 



generally occurred during July and/or August. In 1976, the seasonal 



pattern changed to a rapid development from low January levels to a 



7 

 dramatic peak (1-3 x 10 cells/liter) in February; in the outer harbor, 



a decline to a June minimum was followed by a second peak in August, 



while in the inner harbor the spring/summer peaks were more sporadic. 



In 1977, the February peak reoccurred (January was not sampled) , and was 



followed by June and August peaks with additional station-dependent 



pulses during April and October (Figure 4-4) . 



From 1974 through 1977, the New Haven Harbor phytoplankton 

 community was dominated by several species of centric diatoms (primarily 

 Skeletonema costatum and a suite of Thalassiosira/Cyclotella species) ; 

 microflagellates including cryptophytes {Chroomonas sp., Rhodomonas sp. 

 and Cryptomonas sp. ) , chrysophytes {Calycomonas sp. and Olisthodiscus 

 luteus and unspecified microflagellates) ; dinof lagellates (including 

 Heterocapsa triquetra and Katodinium rotundatum] ; and pennate diatoms 

 (primarily Thalassionema nitzschioides) (Table 4-1) . Skeletonema cos- 

 tatum, Thalassiosira/Cyclotella species and microflagellates were among 

 the ten dominant taxa during every month, while more seasonal contri- 

 butions to community dominance were made by other taxa including dino- 

 f lagellates (generally late spring and summer) (Table 4-2) . 



The centric diatom, Skeletonema costatum, is eurythermal , 

 euryhaline and cosmopolitan in distribution (Smayda, 1958) and has 

 historically been an important component of the Long Island Sound 

 phytoplankton community (Conover, 1956; Riley and Conover , 1967). In 

 New Haven Harbor, S. costatum has been present ubiquitously and during 

 all seasons since 1974 (Figure 4-5). In 1974 and 1975,' blooms occurred 

 from May through July and/or October. Abundance of this species has 



increased during the four-year period reported here; S. costatum has 



7 

 been present in bloom proportions (cell densities greater than 10 /li 



in July 1975, February 1976 and 1977, and June 1977 (Figure 4-5) . 



(Text continued on page 4-19) 



