The measurement and distribution of living microscopic plant matter, commonly referred to as phytoplankton or algae, has been of interest to scientists, researchers, and aquatic resource managers for decades. An understanding of phytoplankton populations and their distribution enables researchers to draw conclusions about an aquatic system's health, composition, and ecological status.
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Phytoplankton populations are typically estimated by measuring chlorophyll a, the primary photosynthetic pigment present in all forms of algae. Currently, chlorophyll can be estimated in lakes, rivers, reservoirs, and coastal and open ocean waters across the globe.

​In vivo chlorophyll analysis is the fluorescent detection of chlorophyll in live algal cells in water. In this technique, the excitation light from the fluorometer passes through the untreated sample of water and causes the chlorophyll within the cells to fluoresce. Environmental conditions, presence of interfering compounds, cellular physiology, morphology, and light history can influence the relationship between the in vivo fluorescence and the actual concentration of chlorophyll in the sample. These factors cause in vivo fluorescence to be a qualitative measure. Despite its qualitative nature, in vivo fluorescence data can supply valuable information on the spatial and temporal distribution of chlorophyll concentrations quickly and easily.

To obtain semi-quantitative data, the in vivo fluorescence data may be correlated with extracted chlorophyll data that can be obtained through the extraction and measurement of the pigment from grab samples on a laboratory fluorometer, spectrophotometer or HPLC.

For correlations with grab samples, collect “grab” samples for chlorophyll extraction and make sure to note the in vivo reading at the time the sample is collected. Several samples should be collected within each niche or environment.

Once the chlorophyll concentration has been determined through extraction, the concentration should be correlated with the corresponding in vivo value similar to what is shown in Graph 1 below.

Notes for AquaFluor: As an alternative, users may purchase Rhodamine WT 400 ppb standard PN 6500-120 from Turner Designs to convert the in vivo CHL channel’s measurement from relative fluorescence to CHL µg/L concentration estimate via calibration. Refer to the Technical Note: AquaFluor Calibration Using Turner Designs Liquid Dye Standards for instructions. The AquaFluor® calibration also requires a Blank sample and the best “true blank” is natural water that has been filtered through a GF/F or membrane filter in order to remove the algal cells but still retain any dissolved components. However, in most cases distilled water is used for the Blank sample since the in vivo readings are semi-quantitative at best.

Graph 1 example:

For more details on chlorophyll analysis visit our application notes here:

In extractive analysis, fluorometric measurements are made on solvent extracts from algal cells to determine quantitative concentrations of chlorophyll and pheophytin.
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​Notes for AquaFluor: A Primary Chlorophyll standard P/N 10-850 is used for calibration and the measurements are made using the 12 x 75 mm glass test tubes.

EPA Method 445.0 is a popular Chlorophyll extractive method that was developed using a Turner Designs Model 10 fluorometer and is published by the United States Environmental Protection Agency. Both the AquaFluor® channel and Trilogy chlorophyll a acidification modules require acidification to correct for pheophytin. This is referred to as the “corrected chlor a” method in section 12.2 of Method 445.0.
EPA Method 445.0 is available on Turner Designs’ website under Application or on the application notes here:
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Absorbance measurements are used for calculating concentrations of carotenoids such as Fucoxanthin, a dominant pigment in diatoms, or Peridinin, a diagnostic pigment of dinoflagellates. Absorbances are also used for calculating concentrations of fluorescing pigments such as chlorophyll a, b, or c. Other absorbance applications include the determination of chemicals/nutrients in water systems (i.e.Nitrate, Silicate, Phosphate, Ammonium, etc).

Absorbance is a measurement of light absorption by solid, liquid or gas. The electrons of the atoms in the absorbing substance reduce the amount of light being passed through that material. As the quantity of atoms increases so does the reduction of photons being transmitted. Beer's Law states that the amount of light transmitted by the sample is proportional to the concentration of the absorbing species and the path length traveled by the light.

​View our available documentation on absorbance with application notes on getting started:

General

Absorbance Theory & Application
​Absorbance Overview

Nitrate

Nitrate Analysis
​Nitrate Comparison Data
​Nitrate/Nitrite Reagents and Test Procedures Adapted from Strickland and Parsons (1968)
​Nitrate/Nitrite LaMotte Test Kit Procedure

​Silicate

Silicate Application Note

​Phosphate

Phosphate Application Note

Active fluorescence methods were developed over 30 years ago to monitor and assess mechanisms of photosynthesis in phytoplankton and higher plants. Active fluorescence methods utilize the relationship between chlorophyll fluorescence and photosynthesis to characterize phytoplankton ‘health’. Phytoplankton photosynthetic efficiency is one of the biological signals that rapidly reacts to changes in nutrient availability as well as naturally occurring or anthropogenically introduced contaminants. The results can be used as an indicator of system-wide change or phytoplankton health.
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For more information on how to run your own analysis, visit our application notes:

Notes for AquaFluor: Readings on the ammonium channel using plastic cuvettes have a maximum range of approximately 10 µM. Minicells are required to achieve readings of 10 µM - 100 µM.

Accurate determination of ammonium in aquatic environments is a critical measurement when investigating Nitrogen cycling and nutrient dynamics. Historically, methods for ammonium determination have been a source of frustration within the scientific community due to the lack of a simple, accurate and affordable method, particularly for measurements in the submicromolar range.

The ammonium technique offers researchers and technicians an excellent alternative to the existing colorimetric indophenol blue method. Benefits of the fluorometric method include:

The colorimetric indophenol blue method is susceptible to inconsistent results, particularly with submicromolar ammonium concentrations, whereas the new fluorometric technique has been proven to provide accurate and precise data over a wide range of water quality, ammonium concentrations and salinities. This method is particularly useful for work in oligotrophic systems, where natural ammonium concentrations are commonly in the submicromolar range.
For more information on ammonium visit our application links below.

The inadvertent introduction of invasive aquatic species to coastal waters when discharging ballast water has been known to cause both ecological and economic damage. Accordingly, regulations are established specifying low levels of living/viable organisms and how to detect them before releasing ballast water.

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Treatment systems are being employed and the challenge of how to show compliance is under examination. One of the methods for determining compliance that is receiving a lot of attention is active fluorescence which looks at the viability of the organisms in the ballast water. Coupling this with fluorescence measurements, giving an indication of quantity of cells in the ballast water, enables rapid assessments of risk of non-compliance with the standards. Portable, easy-to-use, not requiring reagents, and giving results in less than 1 minute make the Ballast-Check 2 a very attractive solution for indicative ballast water monitoring.

Read more about this application through our application notes:

Cyanobacteria have been found to be a numerically abundant faction of the phytoplankton community. Their roles in primary production, community structure, and spatial and temporal distribution are of interest for numerous scientific studies as well as natural water monitoring. Since chlorophyll fluorescence cannot be used to accurately determine cyanobacterial presence, analyzing phycobilin concentrations is essential for detecting, quantifying, and monitoring cyanobacterial levels.

Notes for AquaFluor: The Cyanobacteria channel of the AquaFluor® detects the fluorescence of either phycocyanin (PC) or phycoerythrin (PE) pigments unique to Cyanobacteria.
Readings on the Phycocyanin channel using cuvettes or vials have a maximum range of approximately 3,500 ppb. Minicells P/N 7000-950 and Minicell adaptor P/N 8000-936 are required to achieve maximum range of approximately 20,000 ppb.

The fluorescence is measured in vivo, without extraction or chemical treatment. For many types of qualitative work, in vivo measurements alone may provide sufficient information. For quantitative measurements, in vivo data is correlated with other measurements, such as cell counts or extracted pigment analysis.

Users may purchase Rhodamine WT calibration standards from Turner Designs to convert the PC and PE channel’s measurement from relative fluorescence to PC and PE ppb concentration estimate via calibration on the AquaFluor or the Trilogy.
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For more information on Cyanobacteria visit Turner Designs’ website under Applications.

Monitoring the chromophoric or colored fraction of dissolved organic matter (CDOM) in natural waters can be an extremely useful tool in a variety of marine and freshwater applications. Scientists have developed numerous methods for measuring or estimating DOM concentration for a variety of biological, chemical and physical research and monitoring topics. Fluorescence detection of CDOM is the easiest and fastest means of estimating DOM by taking advantage of CDOM's natural fluorescent property. CDOM measurement is also of interest to researchers due to its effect on light in surface waters and as a natural water-mass tracer.

Dissolved Organic Material (DOM) exists in many forms ranging from naturally occurring humic acids to by-products or secretions excreted from organisms. DOM is a highly abundant form of organic matter and represents a major reservoir of reactive carbon. It is also a dynamic substrate which can undergo reactions to become accessible to bacteria, plants, and animals as an energy source or it can photodegrade resulting in the production of volatile compounds that can have adverse effects on organisms and the environment. DOM typically contain chromophores that absorb UV and visible light, hence the term Chromophoric (or colored) Dissolved Organic Materials (CDOM). CDOM will also fluoresce (hence the term FDOM) after light absorption allowing researchers a way to detect and quantify its abundance in water systems using fluorometry.
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Detection of DOM levels in water systems greatly increases the power of monitoring efforts and helps explain events such as a sudden decrease in primary productivity, phytoplankton regime shifts, algal blooms, and changes in an environment.
For more information on CDOM / FDOM visit our application notes:
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Optical Brightener Agents (OBAs) are primarily added to laundry soaps, detergents, and cleaning agents for the purpose of brightening fabrics and/or surfaces. Laundry wastewater is the largest contributor of OBAs to wastewater systems because it retains a large portion of dissolved OBAs. Water municipalities and researchers are evaluating OBA concentrations in lakes, rivers, and coastal ocean to determine the efficiency of wastewater treatment protocols and wastewater systems. When wastewater systems fail, human waste leaks into natural aquatic systems and might cause an increase in fecal coliform bacteria, which may impact ecosystems.

In an effort to determine source contaminations, researchers are correlating fluorescence of OBAs to bacterial levels. These studies may help decrease this type of anthropogenic input. The AquaFluor® has been used in studies conducted by county health departments and water municipalities to detect OBAs.

For more information on examples to run your own Optical Brightner analysis, visit our application notes as well as the video page:

Oil in water can have great impacts on ecosystems causing an increase in mortality rates of animals and mammals, leading to a shutdown of aquaculture farms, and resulting in costly clean-up efforts to name a few. Therefore, monitoring of oils in natural water systems can be an extremely useful tool for a variety of marine and freshwater applications. Several fluorometers we produce are able to detect the fluorescence of crude oils or crude oil products and can provide on-site measurements to quickly check the oil content of water systems and/or track oil. It can also be used to measure the relative concentrations of oils or hydrocarbon compounds long after the unsightly slick has dispersed. Fluorometric measurements have been successfully used to determine the presence/absence of oil where oil in water was expected. This is extremely important when new installations or operations involving oil are contemplated or for water systems that are in close proximity to structures that use oil in their daily processes.
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​Notes for AquaFluor: Users may purchase PTSA 100ppb standard PN 10-608 from Turner Designs to convert the Oil channel’s measurement from relative fluorescence to Oil ppb concentration estimate via calibration.

Fluorometers are a common environmental research tool because they are specific, require no reagents, and are well established in the industry. Once mounted on a mobile platform, fluorometers can be used to pinpoint contamination sources, track oil spills, or study general water quality over vast areas. Turner Designs offers fluorometers easily integrated into vehicles for both deep water and surface measurement.

For more information on Oil visit Turner Designs website under Applications or visit our application notes here:

Carbon dioxide can enter the water through multiple pathways. Some primary land sources can include decay of organic matter, dissolution of carbonate rocks, wastewater discharge, and watershed draining. Other natural sources include biological respiration, sediment diagenesis, or volcanic activity. A major source/sink of CO₂ is atmospheric exchange at the air/water interface. Simply, carbon dioxide gas dissolves in water.
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An increase in pCO₂ concentrations in water causes a drop in pH. As many biological, chemical, and physical processes are pH dependent, sudden or rapid changes in pH may have adverse effects on the regulation of these processes. Along with pH effects, high levels of CO₂ have been shown to be detrimental to the development of certain organisms such as finfish, shellfish and other calcifying organisms, including phytoplankton.

​View our available application notes for pCO₂ detection:

How the C-sense probe is used for measuring pCO₂ in water

Tryptophan is an amino acid dissolved in water that has a specific excitation and emission. It is classified as protein-like organic matter and sources may include water systems with high biological activity and wastewater or industrial discharge. Tryptophan is yet another parameter researchers can measure to track wastewater effluent, which may greatly impact habitats and wildlife.

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Many of the instruments available for measuring fluorescence of Tryptophan are cumbersome, complex, expensive, and require a high degree of training and expertise to operate. These instruments may also provide too much information to end users who are looking for a simple measure of fluorescence response from, and relative changes of, Tryptophan in water.
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Turner Designs’ C-FLUOR Submersible Probes are simple, low-cost, analog output fluorometers that provide a 0-5 volt signal proportional to the fluorescence response of a certain fluorophore in water. These fluorometers are designed to be integrated with almost any data logger currently on the market. They are small, lightweight instruments that can be hand carried to multiple locations or moored in a fixed location to be used for in situ fluorescence measurements. The figure below shows a typical response curve for varying Tryptophan concentrations in water.

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The calculated maximum for this detection range is 1300 ppb. However, the fluorometers have the capability to detect beyond this calculated maximum by two orders of magnitude because they utilize three gains to provide users with a broad range of detection. Because Tryptophan has a saturation point, the overall maximum detection limit is ~20,000 ppb.
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In a recent study, Synchronous Fluorescence Spectroscopy (SFS) was used to detect low levels of Tryptophan in water (Reynolds 2003). Concentrations ranged from 1.7 – 7.0 ppb with 1.7 ppb being the lowest concentration detected in drinking water. With a limit of detection of 3 ppb Turner Designs' Tryptophan Fluorometers enable users to detect Tryptophan within the stated low level range of Tryptophan in water for the purpose of identifying the presence/absence of protein-like organic matter that may indicate wastewater discharge in the water system under study.
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Polystyrene cuvettes are preferred for the best turbidity results on both AquaFluor Turbidity channels and Trilogy turbidity modules. You may also use disposable glass test tubes in place of polystyrene cuvettes.
We recommend using a Turbidity standard that can be purchased from GFS Chemicals.

What is Turbidity?
Turbidity is described as "an expression of the optical property that causes light to be scattered and absorbed rather than transmitted in straight lines through the sample" (Standard Methods, 1995). As light passes through pure water, it travels along a relatively undisturbed path. The light passed through fluids, with suspended particles present, is greatly distorted by absorption or scattering, caused by these particles. Nephelometry, International Standard Method (ISO 7027), is a method for detecting this scattered light and has been approved by the Environmental Protection Agency (EPA), for testing water quality in producing products destined for human consumption, manufacturing operations, and surface/wastewater.

​Why Measure Turbidity?

All bodies of water have a turbidity component that can be measured. Flux rates of particles between bodies of water or sediment deposition rates can be determined from turbidity measurements. Turbidity can also be measured as a parameter to simply characterize a body of water. For example, systems with higher turbidities will absorb sunlight warming the water or scatter light causing a decrease in photosynthetic activity in algae. Turbidity also provides a substrate and interferes with treatment of water, therefore promoting microbial growth, allowing for the presence of disease-causing organisms such as bacteria, viruses, and parasites that can cause nausea, cramps, diarrhea, and associated headaches. Water and wastewater industries monitor turbidity in drinking water treatment plants to make sure incoming raw water will not inhibit the chlorination process that helps disinfect and purify municipal drinking water.

For more examples of how to run how to run your own analysis on Turbidity, visit our documentation:
​Effects of Turbidity on In Vivo Chlorophyll
​Turbidity Methods & Calibration