Because phytoplankton are relatively short-lived and 

 are mobile within the water column, they integrate the 

 effects of changes in their environment over very small 

 temporal scales. Therefore, nutrient and primary 

 production responses in the water column (e.^., by 

 phytoplankton) and on the surface sediments (e.^., by 

 microphytobenthos) often occur within the time 

 period of a few hours to several days. This relatively 

 short response time creates a challenge to collect 

 measurements in appropriate time scales. A water 

 column monitoring approach sensitive enough to 

 record bi-weekly or even weekly changes in water 

 column productivity could result in a major imposition 

 on project budgets and collection logistics. After 

 consideration of available resources and funding for 

 monitoring activities, sampling of water column 

 productivity during the demonstration project was 

 scheduled on a monthly basis. This schedule, although 

 possibly limiting the ability to assess the immediate 

 effects of project diversions on phytoplankton and 

 microphytobenthos, provided an opportunity to assess 

 changes in broader column productivity characteristics. 



Measurements 



Hydrography 



Physical hydrographic measvirements were made at the 

 surface at each sampling site. Parameters recorded 

 were sampling location, date, time, latitude, longitude, 

 sample depth(s), temperature, salinity, dissolved 

 oxygen, per cent oxygen saturation, pH, Secchi depth, 

 water depth and weather conditions. A multi- 

 parameter YSI model 610 profiler instrument was used 

 for /« situ measurements of salinity and depth 

 parameters. The units of measure (and their nominal 

 accuracy) were: salinity, after conversion from in situ 

 conductivity and temperature (0.2 practical salinity 

 units (psu)) and depth (1 cm). Salinity was also 

 measured by field refractometer in many samples and 

 reported as parts per thousand (ppt) for comparison 

 purposes. Differences as large as 4 ppt are often 

 observed due to the high variability of salinity in 

 estuarine waters, the difficulty of maintaining 

 calibration in the electronic instrument and keeping the 

 field refractometer clean and dry. Dissolved oxygen. 



pH and Secchi depth were not analyzed, but the data 

 were logged for the sake of completeness. 



Nutrients 



Ambient Nutrient Concentrations - The 



concentrations of nitrate, nitrite, ammonium, 

 orthophosphate and silicate were determined in all 

 water samples according to published methods of 

 Environmental Protection Agency (1983) and 

 Whidedge et al. (1981) using automated continuous 

 flow analyzers. All nutrient samples were analyzed 

 with a Technician AutoAnalyzer II. The water samples 

 were collected in pre-numbered polyethylene bottles 

 and immediately placed in the dark and on ice. 

 Chemical analysis of the samples occurred within 

 24 hours of collection and was often completed within 

 5 to 6 hours. Calibration of the automated nutrient 

 channels were performed with each set of samples. A 

 series of five concentrations for each analyte was 

 analyzed prior to analysis of field samples in order to 

 ascertain proper operation. A detailed protocol of 

 standards and their preparation are described by 

 Whidedge et al. (1981) and have been used for 

 estuarine/marine samples from 1975 through the 

 present. All standards were prepared in the laboratory' 

 using either ultra-pure grade deionized distilled water 

 or, as a standard addition, low nutrient sea water. 



Nutrient Amendment Bioassay Studies — Bioassay 

 techniques were employed in the field to evaluate the 

 relative influence of nitrogen, phosphorus, or trace 

 metal additions to changes in phytoplankton biomass 

 [i.e.. Chlorophyll A). These botde assays were 

 enrichment modifications of the productivity estimates 

 and are useful to determine possible nutrient 

 limitations. The bioassay amendment studies were 

 accomplished in screw cap test tubes that contained 

 50 milliliters (ml) of sample. Initial samples were 

 analyzed for extracted chlorophyll content. Four 

 replicates of each sample were amended with 10 micro- 

 moles per liter (jimole/l) of ammonium, 10 (omole/l of 

 phosphate, 10 jimole/l of ammonium plus 10 ^mole/1 

 of phosphate or 100 micro-liters (jj) of "f/2" trace 

 metal stock solution. Four replicates of a control 

 sample with no additions were also utilized. After the 

 additions, the caps were tightened and in vivo 



Chapter Four ♦ 4-3 



