OriginaUy, all 145 water samples from the primary study area were examined for 

 presence of G. breve cells. A 2 ml aliquot of the Utermohl preserved material, settled at the 

 bottom of one liter sample jars, was observed using an inverted microscope. Of these, some 

 from the deepest bottles from the near-bottom sampling contained too much sediment to 

 allow reliable observations. Initial observations indicated that more than 78% of 123 

 remaining samples contained G. breve cells (Appendix V). 



Results and Discussion 



Seventy-two of the original samples (from the upper half of the water column) were 

 reexamined in detail and quantitative counts of G. breve cells were made. More than 91% 

 (66 of 72) of these samples contained G. breve cells and 35% (25 of 72) had cell numbers 

 >50 cells 1"^ (Appendix V). Areas of highest G. breve concentration at the surface had a 

 broad seaward distribution with a tongue of higher cell counts onshore near Station 25 

 (Figure 1). Information or evidence of an offshore bloom outside the primary study area 

 at the time of sampling was lacking. 



The discolored water areas noted during our aerial observations of the primary study 

 area were caused by high concentrations (9 x 10^ cells 1'^) oiNoctUuca (scintUlans = miliaris), 

 a phagotrophic dinoflagellate not generally thought to be toxic. Note the distribution of the 

 Noctiluca bloom (Figure 1, open circles) parallels the western edge of the high G. breve 

 concentrations. 



Since the numbers of G. breve cells in samples from the primary study area were not 

 high enough to be considered a bloom, we needed some information on "normal" or 

 background concentrations of G. breve to put our results in context. Surface water samples 

 were collected from the NOAA Ships OREGON II and FERREL during their routine work 

 in the Gulf. Examination and quantitative counts of these "comparative samples" allow the 

 following observations: 1. The incidence of G. breve in the primary study area was high 

 (89%) but compared well with other nearshore areas of the northern Gulf (Table 1, Figs. 



1. 2 (box) and 3). 



2. The proportion of samples in the primary study area during March 1990 with G. breve 

 concentrations >50 cells 1'^ is 2 to 3 times greater than in other nearshore areas of the 

 northern Gulf or from the same area in September 1990 (Table 1, Figs. 1, 2 and 3), 



3. Both the incidence and concentration of G. breve cells is lower in offshore (open water) 

 areas than on the shelf/nearshore areas (Table 1, Figure 4). 



During the examination of "comparative samples" we noted, on two occasions, high 

 concentrations (5 x 10^ cells T') of the toxic dinoflagellate Gonyaulax monilata (Connell and 

 Cross 1950). These samples were taken on two different cruises during Sept. and Oct. 1990 

 from stations very near the Mississippi delta region in the northern Gulf. No G. monilata 

 were seen in the primary study area. 



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