Correlations in the presence of contaminants in Ulva lactuca spp : part of KB Project on Marine lower trophic systems (KB-34-007-004 1-2C-4)

Seaweed is now relatively commonly consumed across all population strata in the Netherlands and may provide a sustainable, plant-based protein source for humans and animals. Previous studies have revealed that seaweeds can accumulate high concentrations of iodine and heavy metals, although with high variation among seaweed species, geographic location, harvesting season, seaweed metabolic activity, and cultivation method. Food safety of seaweed is an important condition for bringing seaweed food products to the market. Better understanding on the uptake and metabolism of total arsenic is necessary for advising the industry towards a production of seaweeds that are safe for human consumption. In the first three years of this KB project a broad screening of possible food safety risks on fresh seaweed and seaweed based animal feed has been performed. In the last year of the KB project the focus has been put on combining data collected in several projects within WFSR considering contaminants such as the heavy metals and iodine in Ulva Lactuca spp. This increased our knowledge about the ratio’s found between the different contaminant levels, and contributes to understanding the complex uptake mechanisms of seaweeds in general. Therefore, several experiments and data analysis exercises were performed within this project. One of the experiments concerned the manipulation of the nitrogen to phosphorus ratio available to Ulva lactuca spp, an experiment that exposed Ulva lactuca spp to two different water flow schemes. In the second one, an experimental test set-up was designed for future experiments with addition or depletion of nutrients, that can prove our current theories about the uptake of arsenic in seaweeds. The experiments performed on Ulva lactuca spp give good insight in the possibilities of optimizing the set-up for future experiments which are foreseen for the brown seaweed species Saccharina Latissima, and where the uptake of arsenic and iodine is one of the show stoppers for a large scale market introduction in the Netherlands. The different nutritional conditions of the Ulva lactuca spp in the mesocosms resulted only in slightly different concentrations of arsenic, heavy metals and iodine in the seaweed harvested. The scenario in which nutrients are added at a regular flow rate (2 L/min water) showed a statistically enhanced concentration for the analytes nickel, mercury, iodine and bromine. Moreover, iodine and mercury showed statistically enhanced concentrations within the scenario that the flow rate of the water was enhanced from 2 L/min to 25 L/min. Lastly, no statistical differences were found in the concentrations of the analytes when the high flow rate scenario (25 L/min) was compared with the scenario where nutrients were added. The higher flow of 25 L/min translates into a higher flow of nutrients that continuously passes through the tanks, which may level out the effect of the first scenario. From the experiments performed it is concluded that before starting additional experiments an acclimatization period before starting the experiment of four to six weeks is advised. Besides this, the experimental set-up can be improved by monitoring weekly some relevant parameters like the weight of the seaweed growing in the mesocoms, and the concentrations of the nitrate and phosphate levels. The XRF technique can help to reduce costs during this experiments significantly. The experiments performed have resulted in an optimized monitoring strategy for future addition or depletion experiments. Finally, in future experiments it is advised to make use of triplicate test set ups for every addition or depletion experiment. This can lead to increased statistical relevance of the experiments. Considering the data analysis part of the project reviewed the results obtained with standard analysing method of ICP-MS and an alternative way using XRF technique. Comparing the analysis results obtained with ICP-MS and XRF techniques linear correlations and uniform correlation slopes were found for the concentrations of arsenic, lead, mercury, cadmium versus the iodine concentrations. This provides great opportunities to develop a screening method with the XRF technique for certain analytes within Ulva lactuca spp. It is expected that this will also be valid for other seaweed species, although additional experiments should confirm this. The concentrations of the various heavy metals and iodine within Ulva lactuca spp were also evaluated on time dependency on time and on location dependency. Also here good correlations were observed: almost identical ratio’s were found for heavy metals concentrations of arsenic, lead, mercury, cadmium when they are compared to the iodine concentrations. This means that when one of the concentrations of these elements (e.g. arsenic) is measured, the amount of other elements like lead, mercury, cadmium and iodine can be predicted quite well. These observations provide great insight in the uptake mechanisms of contaminants in Ulva lactuca spp, and can lead to lowering the operational costs for seaweed farmers significantly by analysing their seaweed during the growth on the presence of contaminants with the XRF technique. Also the moment that contaminant concentrations found in the seaweeds cultivated tend to increase significantly can be determined much more easily, which can result in the decision to harvest the seaweeds earlier or later than planned originally. If the research performed could be expanded and extrapolated to other cultivation areas in national or international waters, the XRF technique could be used to predict the presence of heavy metals and iodine accurately and cost very effectively. This could lead to a better and low-cost method for coping with possible food safety issues on several seaweed species, and a large scale market introduction of some edible seaweed species in and outside the Netherlands.

Bibliographic Details

Main Authors:	van Tuinen, S.T., Gsell, A., Faassen, E.J., Klijnstra, M.D., Beerman, A.A.A.
Format:	External research report biblioteca
Language:	English
Published:	Wageningen Food Safety Research
Subjects:	Life Science,
Online Access:	https://research.wur.nl/en/publications/correlations-in-the-presence-of-contaminants-in-ulva-lactuca-spp-
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