Elkhorn Slough (ELK) NERR Nutrient Metadata April - December 2002 Latest Update: June 16, 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 during this time. During the dry season (June through September) there is very
little freshwater input, creating a much more saline environment. The surrounding area is mostly
farmlands, which 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. 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 and working with local farmers to attempt to
decrease high nutrient loads to the slough. Other Remarks

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. 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. Depth for this site is approximately 1 meter. 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. With
a mean depth of 1 meter, 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. 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. Depth for
this site is approximately 2 meters. 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. With a mean depth of 2.5 meters, 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.