| Introduction: Note from the Environmental Marketing Manager
In the Spotlight: New Trilogy™ Laboratory Fluorometer
Instruments In Action: SCUFA Used For HAB Monitoring Off South African Coast
Tom's Corner: Description of the10AU Basic Operating Level Adjustment
Instruments In Action: Investigating the Carrying Capacity of the Menai Strait in Terms of Mussel Aquaculture
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|Welcome to another edition of TD News. I'd like to take a moment to introduce myself. My name is Chelsea Donovan and I am the new Environmental Marketing Manager. I've spent the past ten years as an Environmental Scientist working in marine and freshwater systems and recently completed a year as Turner's Application Scientist. I am looking forward to working closer with all of you to continually improve and expand our fluorometer line.
In this issue of TD News, I am excited to announce our newest instrument, the Trilogy™ Laboratory Fluorometer. It's a unique and dynamic laboratory fluorometer with absorbance and turbidity capabilities. We are eager to open up a new realm of applications with the absorbance functionality while maintaining the accuracy and efficiency of our long-standing product line.
We hope you enjoy this edition of TD News. We are always interested in hearing from you; please do not hesitate to contact us with feedback on the newsletter or our products and services.
Introducing the new Trilogy™ Laboratory Fluorometer
The standard Fluorescence Modules are available for chlorophyll a, (extractive acidification and non-acidification plus in vivo), rhodamine and fluorescein dye, cyanobacteria (phycocyanin and phycoerythrin pigments), CDOM and ammonium. For extracted chlorophyll measurements using EPA 445, Trilogy™ automatically calculates the concentration. Customers are also able to order custom filter configurations for additional applications.
The Turner Designs Turbidity Module uses an Infra Red (IR) LED with a wavelength of 860nm to meet ISO 7027 requirements for turbidity water quality measurements. Turbidity is "an expression of the optical property that causes light to be scattered and absorbed rather than transmitted in straight lines through a sample" (Standard Methods, 1995). As light passes through "pure" water, the light beam travels along relatively undisturbed paths. When light passes through a fluid containing suspended solids, the light beam interacts with the particles, and the particles absorb the light energy and re-radiate light in all directions. Due to particle size interference and concentration affects, turbidimeters measure the scatter of light at a 90 degree angle to the incident beam. Common turbidimeters use incandescent lamps (polychromatic) with wide spectral bands that include many wavelengths. Natural color and organic matter in a sample can absorb specific wavelengths and reduce the intensity of scattered light introducing interference. Turner Designs uses a monochromatic IR LED, which have narrow band light wavelengths. The narrow bandwidth of the IR LED is less susceptible to natural color and organic matter reducing interference. A photodetector detects the light produced from the interaction of the incident light and the sample volume and produce an electronic signal that is then converted to a turbidity value.
The Turner Designs Absorbance Module allows the user to install filter paddles with varying wavelengths to measure specific compounds. The Absorbance Module utilizes the Beer-Lambert law (Beer's law) which is the linear relationship between absorbance and concentration of an absorbing species.
The Trilogy™ currently offers Absorbance Modules with filter paddles of 560/10, 600/10, and 750/10nm. The Absorbance Modules can be configured for various colorimetric applications that can be determined with a single wavelength.
SCUFA Used for HAB Monitoring Off South African Coast
The Benguela system suffers from frequent occurrences of a variety of toxic and otherwise harmful algal blooms (HABs). Such blooms can have severe negative impacts on local marine ecosystems and communities. The mooring has been constructed as part of a BCLME (Benguela Current Large Marine Ecosystem) project to demonstrate the utility of real time bio-optical data as an integrated management tool for coastal agencies, and an early warning system with regard to HAB detection and ecosystem protection.
The mooring is deployed on the southern Benguela Namaqua shelf, three and a half kilometers offshore from Lamberts Bay. This area is subject to frequent occurrences of HABs, predominantly composed of dinoflagellate and ciliate species. The buoy has been deployed here as research in the region is ongoing and the area is perhaps the most studied and well understood region of the Benguela system with regard to the dynamics, formative mechanisms and typical assemblage structure of harmful algal blooms.
The buoy provides real time ocean colour reflectance, temperature and fluorescence data transmitted using cell phone telemetry. Considerations in the design of the mooring were that it should be cost-effective and robust whilst minimising shading of the optical sensors and allowing for field calibration and deployment from small vessels.
A second buoy has subsequently been developed utilising a pencil buoy design on a two anchor tight line mooring for enhanced sea-keeping abilities. It was deployed in the same position as the trial mooring off Lamberts Bay in January 2005.
Data are collected from all the instruments simultaneously for two minutes every half an hour. These data are stored on a Compact Flash card in the Ocean-i Sensor Unit. Data are retrieved from the buoy by dialing into the buoy from an external modem. This process is automated at the University of Cape Town so that the most recent data acquisition is downloaded four times a day. Data are then processed using Matlab - remote sensing reflectance is calculated from the radiometer data and locally developed reflectance algorithms are applied to the data to calculate algal biomass and effective assemblage size. The website is updated with these data twice daily when data are available.
This article is from the Harmful Algae Blooms in South Africa website (http://www.hab.org.za) which is intended as a resource for information and data related to harmful algal blooms in the Benguela system. It is a joint effort between the University of Cape Town, Marine and Coastal Management and the Benguela Current Large Marine Ecosystem (BCLME) programme.
Investigating the Carrying Capacity of the Menai Strait in Terms of Mussel Aquaculture
University of Wales, Bangor School of Ocean Sciences
Among many of the projects undertaken at the School, several PhD.-studentships are since October 2004 being conducted through the help of the European Social Fund (ESF). These studentships are always linked to a Small/Medium-sized Enterprise (SME) located in so-called "Objective 1 areas" in Wales. Under its policy to "promote harmonious development" within its boundaries, the European Union (EU) aims to specifically "narrow the gap between the development levels of the various regions". Hence, the EU is supporting development in these less prosperous regions. Under these missives, the ESF-funded projects, through training people and businesses in the Objective 1 regions, aim to increase employment and investment in the region.
Myti Mussels Ltd was established in Bangor in 1982. The cultivation of mussels had been practised in the Menai Strait since the late 1950's, but had gone into decline. By investing in new vessels and adopting new techniques, this decline was reversed and the Menai Strait is now the leading production area for mussels in the entire U.K. The company operates two vessels and farms some 120 Ha with annual production levels ranging from 2400 to 8000 tonnes. All this production is exported live to the continent for further processing.
Figure 3 shows the fluorometer signal over a period of two weeks. It can be seen that the chlorophyll concentrations exhibit a strong semi-diurnal pattern. This occurs due to the water being advected over the mussel beds on the ebb tide (convention in the Menai Strait is to call the stage of the tide where currents are flowing to the south-west, i.e. through the Strait, as the ebb tide), and the phytoplankton suspended in the water column is depleted due to mussel feeding. It is then advected back northwards on the flood, where it can be seen the concentration is significantly lower.
The chlorophyll concentrations also show a greater variability in the signal at the site near the large sand flat area (Penmaen Swatch), compared to the site near the main channel (Penmon Bay). It is thought this is due to the presence of the intertidal area, and the effects it has on the local hydrodynamics. Further research is currently being done in this area, more specifically to clarify the flow environment in this region.
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