Water Quaility Monitoring for the Neuse River Estuary (10AU &
Center for Applied Aquatic Ecology (CAAE) is part of the Botany
Department of North Carolina State University and is dedicated
to research involving aquatic botany, ecology and water quality.
One of the Center's key water quality research projects is the
long-term water quality monitoring and modeling of the mesohaline
Neuse River Estuary. The Neuse River is a highly eutrophied system
in eastern North Carolina and was listed as one of the 20 most
threatened rivers in the nation in from 1995 - 1997. Sections
of the river are currently classified by the USEPA as "nutrient
sensitive". The monitoring has been conducted since 1994
and includes 20 stations, seven of which are permanent solar powered
platforms (see photo) that house a sonde sensor bundle from Hydrolab,
a Turner Designs corporate partner. These stations provide continuous
measurement and vertical profiling of temperature, dissolved oxygen,
redox, salinity, and turbidity. The CAAE
website displays near real-time (2 hour update interval) data
upload for these parameters from the Neuse River stations.
The CAAE has
utilizes a Turner Designs, Self Contained Underwater Fluorescence
Apparatus (SCUFA) for in vivo chlorophyll a measurement
in the field. The system allows for quick calibration with a very
stable solid form standard. The Center's field crews are currently
performing SCUFA casts at key stations as part of routine sampling.
The data values and trends will be compared to chlorophyll data
from extracted chlorophyll-a measurements of water samples collected
in parallel with the SCUFA measurements. Deployment of the SCUFA
on a platform is planned to enable continuous vertical profiling
of chlorophyll, which will also provide an opportunity to evaluate
the unit's antifouling system. The resulting data will be available
in the near future via the website link referenced above.
samples are also collected from all stations for analysis in the
CAAE analytical chemistry lab. Samples are routinely collected
for nutrients, solids, BOD, and extracted pigment (chlorophyll
a) analysis. A Turner Designs 10-AU Fluorometer is employed
for routine analysis of chlorophyll extracts and has proven to
be highly stable and versatile for over seven years of use in
our laboratory. US EPA method 445.0 (acidification - optical kit
10-037) has been the method historically employed within the laboratory
and recent side-by-side studies have shown good agreement with
the Welschmeyer method (optical kit 10-040). The Welschmeyer method
produced results approximately 5% higher on average.
therefore chlorophyll will tend to demonstrate significant spatial
heterogeneity in the environment, more so than the other analytical
parameters/indicators we measure. This trait makes it advisable
to collect and filter of a significant sample volume (200 - 500
mL). A large sample volume from a eutrophied system, such as the
Neuse River produces high levels of analyte. We extract the sample
into 14 mL of 90% acetone, instead of the standard 10 mL. in order
to lower the extract concentration, however, the pre-acidification
measurements in particular are still high enough to warrant calibration
at high levels. The wide dynamic range of the instrument allows
us to achieve high linearity at high levels over a large range
with low residuals. Calibration in the high range with a span
of approximately 20% and removal of the reference filter enables
these high yet accurate measurements, which minimizes the number
of samples requiring error vulnerable dilution. The table and
graph below includes the data from a recent calibration. The calibration
standard used was diluted from a spinach extract stock prepared
in 90% acetone, which was purity adjusted via spectrophotometric
620 Hutton Street Suite 104
Raleigh, NC 27606
Limitation Research in African Great Lakes using 10AU
is a doctoral student under the supervision of Dr. Stephanie Guildford
and Dr. Ralph Smith at the University of Waterloo. She was awarded
an International Development Research Centre (IDRC, Ottawa, Canada)
doctoral research grant to continue her studies on nutrient limitation
in African Great Lakes by visiting Lake Tanganyika and Lake Victoria
in the fall of 2004. The goal of her thesis project is to understand
the relationships between phosphorus (P), nitrogen (N), iron (Fe)
and light in controlling algal biomass in temperate and tropical
Great Lakes: Lake Erie, Lake Malawi, Lake Victoria and Lake Tanganyika.
has identified which nutrients, P, N, or Fe, are limiting to the
phytoplankton communities in the pelagic and littoral zones of
the lakes. These issues are important as changing nutrient regimes
can affect all freshwater systems and it is critical to understand
which type of nutrient inputs can have the most impact. She investigated
the nutrient status of the Lake Tanganyika phytoplankton and the
role of iron in mediating nutrient uptake and interactions.
The Lake Tanganyika
data will be incorporated into her Ph.D. thesis entitled “The
influence of Fe bioavailability on the nutrient status of phytoplankton
communities in temperate and tropical Great lakes” as well as
in primary scientific journals. Her hypothesis is that the bioavailability
of Fe affects N and P limitation of phytoplankton communities
in Great Lakes. Lake Tanganyika is a N limited system where Fe
appears to influence the availability and species of N and P utilized
by the phytoplankton communities. Ammonium assimilation is the
only means of meeting N demands of the phytoplankton communities
that does not require Fe.
10-AU Field Fluorometer and employing a new sensitive fluorometric
technique for the detection of low concentrations of ammonium
[Holmes et al. 1999] has allowed her to measure the extremely
low ammonium concentrations in Lake Tanganyika. Her research will
build upon previous studies of Lake Tanganyika and its phytoplankton
by Dr. Piet Verburg and Dr. Robert Hecky at the University of
Waterloo [Verburg et al. 2003].
research published in 2003 has established that the nutrient regime
of the lake may be changing due to a warming climate and this
may be increasing the probability of iron limitation of algal
growth. Her specific program for Lake Tanganyika was to measure
a variety of nutrient status indicators for the nutrients N, P,
and Fe and incorporate this data into a summary of the phytoplankton
nutrient status of Lake Tanganyika. Her research will greatly
expand on the understanding of phytoplankton-nutrient relationships
on the lake to support ongoing efforts to manage the lake’s productivity
and in particular, its valuable fishery.
M., Aminot, A., Kerouel, R., Hooker, B. A., and Peterson, B. J.
A simple and precise method for measuring ammonium in marine and
freshwater ecosystems. Canadian Journal of Fisheries and Aquatic
Sciences 56, 1801-1808. 1999.
Verburg, P., Hecky, R. E., and Kling, H. Ecological consequences
of a century of warming in Lake Tanganyika. Science 301, 505-507.
Data Transfer to a Computer
The data from
our fluorometer is not being displayed on our computer. What are
the things that we can check?
problems of this nature can be caused by faulty cabling or issues
related to the configuration of the computer serial port. It may
also be possible that the port in question is being used by another
program. Check the serial cable first. Make sure that the cable
is properly seated at both ends and the captive screws are tightened.
Inspect the cable for physical damage or bent pins. If you are using
a gender changing connector on the cable, make sure the transmit
and receive data lines are not reversed. Try a different cable if
you have any doubts and have one available. The port settings in
your terminal program can also be a source of communication failure.
If you are using a windows based terminal program, the port settings
should be at the following: 9600 bps, 8 data bits, no parity, 1
stop bit and flow control set to none. The 10-AU, Aquafluor and
TD-700 can all be used with any RS-232 serial printer or Windows
based terminal program. For more information refer to the instrument
operational manuals. The operational manuals are available in pdf
format on the web at http://www.turnerdesigns.com.
Use the table below for a current software and serial cable reference.
Provided Serial Cable p/n:
Program Version 2.1
If you purchased your SCUFA unit prior to February 2001. You
do not have the latest firmware and your SCUFA must be updated
prior to using 2.1.
** The 10-AU and the Algaewatch have datalogger interface programs
to facilitate downloading and data incorporation into Excel.
*** May be used with typical terminal type programs for interface
and data capture.
also has Spreadsheet Interface Software available for direct data
import into Excel.
below show the Spreadsheet Interface Software with and without a
com port available.
Speaking, It All Adds Up…….
is a series
of articles for people who want to obtain the best possible results
from their fluorometer. This month's article explains how time and
temperature affect the repeatability and consistency of fluorometer
readings. It includes some ideas on minimizing the effects of these
two parameters' contribution to measurement uncertainty.
There are many different fluorescent materials measured with a fluorometer,
and they can be measured in several different ways. For example,
chlorophyll a can be measured by taking discrete samples or by using
a continuous flow configuration.
To get repeatable
solution concentration readings, (same reading is obtained when
measured with another fluorometer); and consistent readings, (readings
do not change with duplicated measurements), the effects of instrument
warm-up time and changes in measurement environment temperature
need to be factored in to the measurement procedures.
The Turner Designs 10-AU and TD-700 use lamps and photomultiplier
tubes, so the effects of warm-up drift will be more noticeable than
their solid-state counterparts including SCUFA, CYCLOPS-7 and the
Aquafluor. (These use LEDs and Photodiodes).
Graph 1 shows
the warm-up drift of a 10-AU when measuring a solid secondary standard.
The secondary standard is a passive device that far exceeds the
stability of the 10-AU. The graph shows that readings will be more
consistent after 2 minutes warm up time. This is important to take
into account when using the 10-AU or TD-700 for discrete samples.
click for larger view
state fluorometers stabilize much faster, and typically require
only a few seconds to provide consistent readings.
To reduce the effect of drift immediately after turning on the
fluorometer, take a minimum of three readings and record the
average value. If possible, leave the fluorometer on continuously
to achieve instrument thermal stability.
It is important to measure at the same temperature as when calibrating
the fluorometer. Typically, solutions and hardware will be at a
different temperature in the lab than when taking measurements in
materials have fairly high temperature coefficients. Usually, as
temperature increases, the fluorescence signal decreases. Unless
corrected for, this can produce significant errors. The 10-AU features
an automatic temperature compensation option for use when making
continuous flow measurements. Manual corrections need to be applied
to measurements made with other Turner Designs fluorometers.
Record the temperature during instrument calibration and operation,
and apply a temperature correction to your data for improved
repeatability and consistency.
Additional information on improving the integrity of your data can
be found in the many technical articles in the application section
Designs web site:
on the Turner Designs Databank
In response for more 'real-world' data from our customers, Turner
Designs has launched the TD
DataBank Program where we present examples of customer research
for all instruments and applications. The DataBank is organized
according to instrument type and application and offers our users
real-world examples of how researchers and technicians are using
Turner Designs instruments in their work. In addition to providing
meaningful information for our customers, by having a description
of your work highlighted on our website, it will serve as a means
of reaching a greater number of scientists around the globe. We
see this as a highly effective means of assisting our users in making
informed decisions. In order for this type of program to succeed,
we need information from you on your application and how a Turner
Designs fluorometer is helping you.
have designed the TD DataBank to make submitting an application
summary as easy as possible. The entire process should not take
more than 20 minutes. We ask for a brief description of your research,
and how you use Turner instruments. Also, a picture or graph of
data collected with Turner instruments is requested. To show our
appreciation for your data bank articles, we will send you a Turner
Designs sports bag. Claim your sports bag now by submitting
your DataBank article!
We hope you will join us in this exciting and useful program by
sharing your knowledge and experience with scientists and technicians
around the globe. To take part, please visit the following link
or call us directly at 1(877) 316-8049 ext 163.