Pigments progress

Pigments progress


PML has attained the ‘gold standard’ in its work on analysing the pigments contained in some of the ocean’s smallest organisms.

Phytoplankton, the tiny plants that float at the sea surface providing much of the oxygen we breathe and most of the primary food that sustains food chains and life in our seas contain complex mixes of pigments. Knowing with accuracy and precision the pigments that are present in phytoplankton is fundamental to understanding many aspects of ocean biology and chemistry and a keystone for ocean research including studies on fisheries and climate change, which are relevant to all of us.

Sampling the world’s oceans by research vessels remains an important although expensive activity but is increasingly being complemented by remote sensing using orbiting satellites that can ‘read’ many ocean features, including the pigments that reflect light at various wavelengths. Interpreting the images the satellites obtain is very complex and relies upon detailed analysis of samples that have been collected at the sea surface to establish exactly what the satellite images are seeing. The pigments the phytoplankton contain and show up on the images are essential in identifying the various groups, which in turn play differing roles in the marine system. So it is fundamental that analysis of the pigments is both precise and accurate. Despite sounding simple this involves some very complex processes of collection, filtration, extraction, cell disruption and the identification of the pigments themselves.

“There is plenty of room for error”, says Dr Ruth Airs of PML, who led the project, “Phytoplankton pigment analysis is relatively complex and the use of High Performance Liquid Chromatography (HPLC) can separate out upwards of twenty identifiable pigments, so it is very easy to get things wrong; pigments can be misidentified, overlooked, or be recorded as present when there are actually missing. The highest levels of quality control at all stages are crucial to accuracy, and that is what we have achieved at PML.”

The need for accuracy in analysis is a prerequisite for comparing scientific results using pigment and satellite data so attempting to reach an internationally recognised standard is a critical step in making sure that results from a number of laboratories are comparable. PML took part in an inter-comparison assessment along with another 13 laboratories worldwide. Each was sent identical samples to analyse and PML performed among the best with degrees of accuracy and precision that earned it a place in the top three of the 14 labs participating worldwide. What this means is that many other aspects of PML science that use pigments  can be confident that data they are using are among the best available and most reliable. PML scientists now also have a quality benchmark for pigment data from other laboratories. Achieving this standard is a testament to the quality of PML science and hard work over the last few years, but this is not a one-off, said Ruth Airs: “We are thrilled to have gained this standard and we want to maintain it, that means continuing the high levels of quality control that have made us one of the best in the world”.

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