Elkhorn Slough (ELK) NERR Nutrient Metadata (January- December 2004) Latest Update: November 11, 2005

Nutrient monitoring is conducted at 26 National Estuarine Research Reserves (NERR) from
four locations within or adjacent to the reserve on a monthly basis of the following parameters:
orthophosphate, ammonium, nitrite, nitrate, and chlorophyll a. Note: Reserves may collect
additional parameters which are available by searching the Yearly Files directory. Research
objectives Elkhorn Slough (ESNERR) is a unique estuary along the central Californian coast.
There are fresh water inputs during the wet season (October through May) causing a brackish
environment, while during the dry season (June through September) there is very little
freshwater input resulting in a much more saline environment. The surrounding area is mostly
farmlands, which causes concern, as they may be a source of significant amounts of nutrients
entering the slough. With the base monitoring program we are able to quantify the variability of
these nutrients in different areas of the slough as well as through different seasons of the
year. a) Monthly Grab Monthly grab samples are collected to quantify the spatial variability of
important nutrients in the water column at sites representing the estuarine endpoints of the
Elkhorn Slough estuary. b) Diel Sampling Program Once per month, samples are collected every
hour through a 24-hour tidal cycle to quantify the temporal variability of important nutrients
in the water column as a function of tidal forcing.

SUPPLEMENTAL INFORMATION:
Associated researchers and projects Ken Johnson et al. are looking at nutrient budgets in the slough with
real time nitrate loggers in the main channel of the slough. Adina Paytan, Scott Wankle et al
are looking at nitrogen isotopes to assess the contributions of nitrogen through ground water.
Nicholas Welschmeyer et al are looking at nutrients and phytoplankton populations in the main
channel of the slough on a weekly basis. Marc Los Huertos et al are investigating nutrient
budgets in the Elkhorn Slough watershed and identifying "hot spots" of nutrients in the slough
while working with local farmers to attempt to decrease high nutrient loads. Robert Burton from
Moss Landing Marine Laboratories is investigating the functionality of wetlands as nitrate
source reduction. Other Remarks a. The following nitrate data were deleted due to negative
values, indicating an error in measurement: Date Site Monitoring Program Time 05/04/04 Azevedo
Pond Grab Sample (Rep 1 and 2) 16:05- 16:06 06/14/04 Azevedo Pond Grab Sample (Rep 2) 13:25
09/08/04 Azevedo Pond Grab Sample (Rep 1 and 2) 12:15- 12:16 09/09/04 South Marsh Diel Sample
00:23 b. Due to ISCO malfunction, the following data points are missing: 03/17/04 ISCO collected
samples from only the first 17 hours. The last 7 hours of data are therefore missing. These data
points would have corresponded to the times 07:19-13:31 08/02/04 ISCO failed to collect samples
from the first four hours and only sampled the last 20 hours. Missing data would have
corresponded to the times 06:39 09:45 09/08/04 ISCO failed to collect samples from
the first 9 hours and also from hours 21-22. Missing data would have corresponded to the times
00:37- 08:53 and 21:17- 22:19 10/05/04 ISCO collected samples from only the first 15 hours. The
last 9 hours of data are therefore missing. These data points would have corresponded to times
14:00- 22:16 11/02/04 ISCO failed to collect samples from hour 4, 10, and 11. Missing data would
have corresponded to times 09:22, 15:34- 16:36 12/07/04 All samples are missing from December 07
due to ISCO failure c. The following grab samples are missing due to collection errors: 11/02/04
South Marsh 12/07/04 Vierra Mouth d. The following samples are below the MDL and replaced with a
9999 and comment coded with a "B" in the data section. If a sample is used in a
calculation, the calculated value is also replaced with a 9999 and comment coded with
a B. Date Site Monitoring Program Parameter Time 03/16/04 NM Grab Sample
(Rep 1) Nitrite 12:00 09/08/04 SM Grab Sample (Rep 1 and 2)Ammonia 11:02- 11:03 09/08/04 SM Diel
Sample Nitrite 09:55 09/08/04 VM Diel Sample Ammonia 12:46 11/02/04 AP Grab Sample (Rep 1 and
2)Nitrite 17:53- 1754 e. The following diel data are missing due to lab error: 09/08/2004 0955
NO2 for 09/08 0955 was analyzed but due to an error in the lab there was no value for this
sample. Due to this error NO3 also could not be calculated. f. Daily, Monthly, and Annual
Precipitation Totals Jan-Dec 2004 elkcwmet Caspian Weather Station Date Daily Precip Totals (mm)
01/01/2004 23.4 01/02/2004 0.8 01/03/2004 0.3 01/06/2004 1.0 01/07/2004 0.3 01/11/2004 0.3
01/13/2004 0.3 01/14/2004 0.8 01/23/2004 0.3 01/24/2004 13.0 01/27/2004 2.5 01/28/2004 0.5
01/30/2004 0.3 01/31/2004 0.3 January Monthly Total (mm) 44.1 02/05/2004 0.3 02/06/2004 0.5
02/07/2004 0.3 02/08/2004 0.3 02/09/2004 0.3 02/12/2004 0.3 02/16/2004 13.7 02/17/2004 18.5
02/18/2004 9.4 02/19/2004 1.5 02/20/2004 1.5 02/21/2004 1.3 02/22/2004 0.8 02/23/2004 0.3
02/24/2004 4.6 02/25/2004 30.0 02/26/2004 9.1 02/27/2004 1.8 02/28/2004 0.3 February Monthly
Total (mm) 94.8 03/01/2004 5.8 03/03/2004 0.3 03/04/2004 0.3 03/06/2004 0.3 03/07/2004 0.3
03/10/2004 0.3 03/11/2004 0.3 03/13/2004 0.3 03/14/2004 0.3 03/16/2004 0.3 03/18/2004 0.3
03/20/2004 0.3 03/25/2004 9.1 03/27/2004 0.3 March Monthly Total (mm) 18.5 04/01/2004 0.3
04/10/2004 0.3 04/14/2004 0.3 04/20/2004 2.3 April Monthly Total (mm) 3.2 05/28/2004 2.5 May
Monthly Total (mm) 2.5 07/04/2004 0.3 July Monthly Total (mm) 0.3 09/17/2004 0.3 09/19/2004 0.5
September Monthly Total (mm) 0.8 10/16/2004 5.6 10/17/2004 10.9 10/18/2004 0.3 10/19/2004 23.6
10/29/2004 0.3 October Monthly Total (mm) 40.7 11/03/2004 13.0 11/04/2004 5.6 11/06/2004 0.3
11/09/2004 0.5 11/10/2004 1.8 11/11/2004 10.2 11/12/2004 0.3 11/14/2004 0.3 11/16/2004 0.3
11/17/2004 0.3 11/18/2004 0.3 11/19/2004 0.3 11/24/2004 0.3 11/25/2004 0.3 11/27/2004 4.6
November Monthly Total (mm) 38.4 12/07/2004 28.4 12/08/2004 21.6 12/09/2004 1.8 12/10/2004 0.3
12/12/2004 0.3 12/22/2004 0.3 12/28/2004 33.5 12/30/2004 7.1 12/31/2004 34.3 December Monthly
Total (mm) 127.6 Annual Total (mm) 370.9

CURRENTNESS REFERENCE:
Observed

SPATIAL DATA ORGANIZATION INFORMATION:
Indirect Spatial Reference: Site location and character Elkhorn Slough
is located on the West Coast of the United States in Central California. It connects with the
Pacific Ocean in central Monterey Bay near Moss Landing, California. There are four sampling
sites. a. Azevedo Pond (AP) (36( 50; 44.64; N, 121( 45;
13.24; W) receives fertilizer and pesticide runoff from a strawberry field in
year-round production. The YSI is located about 10m from a culvert connecting the pond to the
slough. Tide ranges from 0 to 1.3 meters while salinity ranges from 8.8 during heavy runoff to
41 ppt during strong evaporation. The sonde is located approximately 30 cm off the bottom, which
is composed of silty mud. b. North Marsh (NM) (36( 50; 04.75; N, 121(
44; 18.33; W) is located in between South Marsh and Azevedo Pond. This site
is impacted by both agricultural and urban runoff. The tidal range is approximately 0.4 meters
while salinity ranges between 20 and 40 parts per thousand. There is freshwater runoff from
upland and agricultural sites. The sonde is approximately 30 cm off the bottom, which is
composed of silty mud. c. South Marsh (SM) (36( 49; 05.00; N, 121(
44; 21.83; W), located about 3 km south of NM, is in a side channel of the
slough and is relatively free from impact by anthropogenic influences as it is surrounded by
mostly reserve land. The YSI is located on the side of a bank in one of the secondary slough
channels. This site receives runoff mostly from uplands and some from cattle ranches, receiving
the least amount of pollution. Tidal ranges from 0 to 3 meters while the salinity range is from
22 to 36 parts per thousand. The sonde is approximately 30 cm off the bottom, which is composed
of compacted silty mud. d. The fourth site, Vierra Mouth (VM) (36( 48;
39.95; N, 121( 44; 45.40; W), is located at the mouth of the
slough and is used to identify oceanic influence. The tidal range is from 0 to 3.2 meters while
salinity ranges from 26 to 34 parts per thousand. The sonde is located approximately 30 cm off
the bottom which is composed of compacted mud and sand due to strong tidal currents. This site
receives drainage from the entire watershed due to its location at the mouth. There are several
auto wreaking yards located approximately 2 km east of this site.