NOAA PROFESSIONAL PAPER 11 



grazed and dispersed before significant quantities sinic into 

 the bottom layer. Sinking fecal material produced by graz- 

 ing zooplankton may be a major mechanism by which 

 organic matter of phytoplankton origin reaches the bottom 

 layer during summer. 



Rough calculations indicate that the ammonia input to 

 the Apex via regeneration provides 40 to 50 percent of 

 the nitrogen required to support observed levels of phy- 

 toplankton productivity in the Apex during spring and 

 summer (table 9.1-1). The importance of ammonia re- 

 generation is especially apparent during summer when 

 phytoplankton productivity is high and dissolved inorganic 

 nitrogen (DIN) concentration is low. Based on observed 

 concentrations of DIN (typically less than 2.0 jjig-at/l) and 

 primary productivity (usually greater than 1 g C/m"/d) in 

 the Apex, DIN turnover times in the surface layer ranged 

 from 12 hours to 2 days. Thus, zooplankton grazing, am- 

 monia regeneration, and phytoplankton productivity ap- 

 pear to be closely coupled during the warm summer 

 months when the water column is well stratified. 



Vertical mixing and nutrient regeneration are the major 

 mechanisms of euphotic zone enrichment over most of the 

 Bight outside the plume of the Hudson River. Nutrient 

 supplies are more discontinuous than in the plume, and 

 thermal stratification limits rather than enhances the flux 

 of nutrients into the euphotic zone. Consequently, phy- 

 toplankton productivity is low throughout the summer and 

 blooms are greatest in magnitude and most frequent dur- 

 ing late winter and spring. 



Distribution 



The abundance and distribution of phytoplankton was 

 reviewed by Malone (1977c). Phytoplankton cell densities 

 usually range from W to 10'^ cells/1 in estuarine and coastal 

 waters compared to 10^ to 10^ cells/1 in the Apex and 10^ 

 to IC^ cells/1 in the outer Bight. Phytoplankton populations 

 are typically dominated by diatoms (cold months) and 

 chlorophytes (warm months) in estuarine and Apex water 

 and by diatoms in the outer Bight. 



The diatoms Skeletonema costatum, Asterionella japon- 

 ica, Leptocylindriis danicus, Thalassionema nitzschioides, 

 and Chaeloceros debilis are abundant in both estuarine 

 and Bight waters. Rhizosolenia alata, R. faeroense. Chae- 

 loceros socialis. and Nitzschici closterium usually make up 

 a larger proportion of the diatoms present in the outer 

 Bight than in the Apex. The chlorophyte Nannochloris 

 atonuis frequently dominates estuarine and Apex phyto- 

 plankton during summer. The dinoflagellates Prorocen- 

 trum micans, Peridiniiim spp. , and Ceratium spp. are often 

 abundant during spring, summer, and autumn. 



Mandelli et al. ( 1970) described the species composition 

 of the netplankton along the southern coast of Long Is- 

 land. Phytoplankton biomass peaked during autumn and 

 late winter. Blooms of S. costatum produced both peaks. 



Diatoms dominated the September-March 1966 period, 

 whereas dinoflagellates were most abundant during the 

 April-August 1966 period. Among the diatoms, S. cos- 

 tatum, Thalassiosira sp., Chaetoceros sp., and R. alata 

 were successively abundant from September through De- 

 cember, and apparently again during February and March. 

 Peridiniutn depressum and Ceratium massUence bloomed 

 in April and May, respectively. Ceratium tripos was the 

 dominant netplankton from June to August. During 

 March 1967 a succession of species was observed: S. cos- 

 tatum dominated during the first week; Thalassionema 

 nitzschioides, Rhizosolenia sp., v4. japonica, and Nitzschia 

 seriata, the second week; and Ceratium tripos, C. macro- 

 ceros, C. furca. and Peridinium depressum. the last 2 

 weeks. This alternating pattern of diatom and dinoflagel- 

 late abundance appears characteristic of shallow coastal 

 waters off western Long Island. 



Recent observations along the New Jersey coast indicate 

 that C. tripos was abundant during the summers of 1974 

 and 1975 (Myra Cohn, personal communication). Cell 

 densities ranged from 40/ml to 740/ml (geometric mean 

 = 133/ml in June 1975 and 222/ml in July 1975). Increases 

 in C. tripos cell densities are also typical of Fire Island 

 Inlet on the Long Island coast (Sylvia Weaver, New York 

 University, personal communication). From 1973 to 1975, 

 peaks in cell density (as high as 5/ml) occurred in May and 

 June following slow increases beginning as early as Jan- 

 uary 1974. 



Biology of Ceratium tripos 



Ceratium tripos (O. F. Mueller) Nitzsch, a large (cell 

 volume 1-10 x 10*^ M-m') armored dinoflagellate (fig. 

 9.1-2), is a holoplanktonic, cosmopolitan species com- 

 monly found along the east coast of North America from 

 Cape Hatteras to the Gulf of Maine. Based on its distri- 

 bution and on experimental growth studies (Cleve 1900; 

 Bigelow 1926; Graham 1941; Nordli 1957), C. tripos is 

 euryhaline and eurythermal, with a preference for the 

 cooler waters (10°-20° C) and lower salinities (<33%p) of 

 the continental shelf. 



The organism seldom occurs in large numbers (greater 

 than 500 cells/1) and may often be overlooked. Maximum 

 concentrations typically range from 1 to 5 x 10' cells/I; 

 peaks reportedly occur during spring and summer. 



Two varieties of the species have been described. The 

 larger, Atlantica Ostenfeld, is 100 to 170 p,m long and has 

 equally well-developed anapical horns. Baltica Schutt is 

 smaller (90 to 120 ixm long) with unequal anapical horns. 

 C tripos var. Atlantica dominated the Ceratium popula- 

 tion in New York Bight during the 1976 bloom. C. tripos 

 var. Baltica was more abundant during 1977. 



C. tripos is photosynthetic, with maximum light-de- 

 pendent division rates of about 0.3/d (Nordli 1957). As 

 with most other species of Ceratium, cell division usually 



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