I 



& 6-1 Maximum and Minimum Tide Levels 



FMAMJJASOND 



Figure 4.1. Seasonal dynamics in channels 

 and creeks sampled monthly during 1985. 

 Data for nutrient concentrations and algal 

 abundance are presented in order of the time 

 of their maximum value. Phytoplankton data 

 are from a tidal creek; all data are from Fong 

 (1986) and Rudnicki (1986). 



stage, the algae may be dislodged, float to the 

 surface, and be moved about by wind and water 

 currents. As a result, cover can be highly 

 variable in both space and time, and areas of 

 similar cover can have very different 

 biomass. The field survey was devised to 

 identify conditions that led to maximum 

 biomass (called blooms); thus, areas with the 

 greatest volume of algae were sampled at each 

 monitoring station. 



Of the five habitats sampled, phyto- 

 plankton were most dense in the tidal creek 

 that had the lowest tidal circulation. Seasonal 

 peaks in chlorophyll and cell counts occurred 

 in spring when weather was warm and tidal 

 action minimal. Together, the 1984 observa- 

 tions of blooms during closure and the 1985 

 field study suggested that phytoplankton 

 accumulate when water currents are reduced 

 and when nutrients are plentiful (Table 4.1). 

 At other times, tides continually remove algae 

 and maintain clearer water. 



Table 4.1. Water quality at Tijuana Estuary 

 during nontidal (1984) and tidal conditions 

 (summary data from Fong 1986 and Rudnicki 

 1986). 



80 



