13-6 



peak reoccurred, and was followed by June and August peaks. Additional 

 localized pulses occurred during April and October. Common Long Island 

 Sound diatoms, Skeletonema costatum and Thalassiosira/Cyclotella species, 

 and microflagellates were among the ten dominant taxa during every 

 month, while more seasonal contributions to corranunity dominance were 

 made by other taxa including nontoxic dinof lagellates (generally late 

 spring and summer) . 



Zooplankton 



Zooplankton populations were studied by a program of monthly 

 sampling using towed nets. From 1973 through 1976, total zooplankton 

 abundances in New Haven Harbor were usually at lowest seasonal levels in 

 December and January. Abundances generally increased to seasonal peaks 

 by March or April, remained at peak levels with some fluctuations 

 through June, and declined by July or August. 



Early spring zooplankton-density increases reflected the 

 appearance of larval stages of calanoid copepod species (particularly 

 Acartia hudsonica) and barnacles. Late spring and early summer was a 

 period of particularly intense reproductive activity for many benthic 

 invertebrates including barnacles, polychaetes, bivalves and gastropods. 

 Production of planktonic larvae continued throughout the simmier with 

 peak abundances during the warmest months of the year (July and August) . 

 Acartia tonsa was an important mid- to late summer dominant. In autumn, 

 a winter faunal assemblage, consisting of calanoid copepods and barnacle 

 larvae, returned to prominence. 



Copepods were the most abundant planktonic group in New Haven 

 Harbor. Acartia tonsa and Acartia hudsonica (= clausi)., the dominant 

 copepods, together comprised up to 93% of the total copepod assemblage. 

 A. hudsonica normally reached peak densities in the spring and was 

 succeeded by A. tonsa populations during mid- to late summer. Other 

 abundant calanoid copepods, all common to Long Island Sound, were 



I 



