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Research Focus


Researchers Investigate Ultra-low Mediterranean Nutrient Levels Author Details: Lalicia Potter, lpotter@seal-us.com


Researchers at Haifa University’s Marine Biological Station in Israel are exploiting the ultra-low detection limits of advanced laboratory equipment to measure extremely low nutrient concentrations in marine water. The University’s Professor Krom said: “We work in the Eastern Mediterranean which has the lowest regional concentration of dissolved nutrients anywhere in the global ocean. We therefore utilise an automated segmented fl ow analyser from SEAL Analytical, which has been specially adapted to accommodate ultra-low measurements.”


Lalicia Potter


The SEAL AutoAnalyzer 3 (AA3) is a 4 channel system, measuring Phosphate with a long fl ow cell which has a detection limit of 2 nM. Ammonia is measured using a Jasco fl uorometer with a similar ultra-low detection limit, and Silicate, which has a higher concentration, is measured using SEAL’s high resolution colorimetric technology.


the lowest values anywhere in the world. Professor Krom said: “The maximum levels of nutrients measured in the EMS are 250 nM phosphate, 6 uM nitrate and 6-12 uM silicate. Ammonia is often in the low nanomolar range. By contrast, in the North Atlantic, values are 1000 nM phosphate,16 uM nitrate and 20 uM silicate, and the levels in the North Pacifi c are even higher.”


The Value of Data


The low levels of plankton caused by low nutrient levels, result in a low biomass of fi sh. Nevertheless, coastal areas generally support more fi sh than offshore, so the research will seek to quantify and understand the nutrient cycle in the coastal regions, which is poorly understood at present. Professor Krom continued: “We plan to develop understandings which will inform stakeholders such as government. For example, there is a discussion about the potential for fi sh farms off the Israeli coast, so our work will enable science- based decisions regarding the quantity of fi sh that the system can support.”


To-date, three data sets have been taken from the EMS, and the fi rst publishable paper is in the process of being prepared.


Choosing the Right Analyser


The measurement data are being used to determine the season nutrient cycling in the system, which will then be used to help understand the nature of the food web and the effects of global environmental and climate change.


Low Nutrient Levels in the Mediterranean


The eastern Mediterranean Sea (EMS) has an almost unique water circulation. The surface waters (0-200m) fl ow into the Mediterranean through the Straits of Gibraltar and from there into the EMS at the Straits of Sicily. As the water fl ows towards the east it becomes increasingly saline and hence denser. When it reaches the coast of Turkey in winter it also cools and then fl ows back out of the Mediterranean under the surface waters to Sicily, and then eventually through the Straits of Gibraltar to the North Atlantic. This outfl owing layer exists between 200m and 500m depth.


Phytoplankton grow in the surface waters (0-200m) because that is the only layer with suffi cient light. This layer receives nutrients from the adjacent land, from rivers and wastewater discharges, and also from aerosols in the atmosphere. These nutrients are utilised by the plankton as they photosynthesise. When the plants die (or are eaten) their remains drop into the lower layer and are jetted out of the EMS. Because the water fl ows are so fast (it takes just 8 years for the entire surface layers of the EMS to be replaced), these nutrient rich intermediate waters rapidly expel nutrients from the basin. The result is very low nutrient concentrations and very low numbers of phytoplankton – some of


Professor Krom said that his fi rst ‘real’ job was working for the (then) Water Research Centre at Medmenham in the UK, where he was involved in the development of chemical applications for the Technicon AA-II autoanalyzers, which included going on secondment to Technicon for several months. SEAL Analytical now own and manufacture the AutoAnalyzer brand of Continuous Segmented Flow Analyzers, so Professor Krom’s career has been connected with autoanalyzers for decades. For example, Professor Krom


INTERNATIONAL LABMATE - JANUARY/FEBRUARY 2018


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