Sequencing the 'Sea Lettuces'; key links between terrestrial agriculture and marine ecosystems

The green macroalgae, or seaweeds, are one of the most common sights on beaches and shorelines around the UK, providing food and shelter for many marine animals. The most familiar of these green seaweeds are the Ulva species; the 'sea lettuces'. These are particularly important because they act as a link between the land and the seas; increased nutrient run-off from agricultural fertilisers, or from urban sewage treatment plants, can lead to higher nutrient levels in the rivers and seas that border farmlands and cities. These enriched waters, which can also occur naturally through the spring upwelling of nutrient-rich deeper sea waters, can, in turn, see extraordinarily rapid growth of the seaweeds that live in them; the so-called 'green tides' that can choke coastal waters worldwide and which are responsible for threatening the Olympic sailing regatta at Qingdao in 2008, covering beaches along the south coast of the UK in 2010, and fouling the Breton coast annually.

We still know very little, however, about these astonishingly important organisms. The proposed research aims to provide the first genome sequence of one of these green seaweeds, Ulva compressa, giving us a first look at their genomic architecture and at the genes which allow them to grow so dramatically. The UK has a strong tradition of green seaweed research, and this proposal would add to that tradition by providing a framework on which to hang 'Next Generation' genomic experiments that look at the ecology and biology of marine seaweeds.

As detailed in the Case for Support, the Ulva genome and transcriptome sequences will stimulate the development of a molecular toolkit for the green seaweeds, including a) higher-resolution taxonomic markers, b) population genomic tools, and c) improved green seaweed transformation techniques. Once these have been developed and applied, which is expected to take 1-2 years of work beyond the end of this Small grant proposal, an improved molecular toolkit will benefit the following groups:

I. The Environment Agency, and its devolved counterparts, which will benefit from improved understanding of the ways in which invasive species spread and affect marine biodiversity. The green seaweeds contain a number of such invasive species, most notably Caulerpa taxifolia and Codium fragile, but the factors which determine whether or not a particular green seaweed species will become invasive are not well understood. Given the huge effect which invasive species can have on biodiversity, and given that guidelines established by the Convention on Biological Diversity recommend the prevention of migration by possible invasive species, the development of high resolution taxonomic markers from the Ulva genome and transcriptome will help the EA, SEPA, and NIEA by elucidating the various pathways by which marine invasive seaweeds may be introduced and spread.

II. Policy makers and advisors, such as the Government Office for Science and the Joint Nature Conservation Committee. Under certain conditions, Ulva species bloom to give green tides. These foul tourist beaches, are increasingly common in areas with rising populations, and the EU Water Framework Directive has identified them as an important indicator of estuarine quality. As Ulva growth is usually nitrogen limited, green tides are thought to be triggered by sudden increases in the levels of nitrate run-off from agricultural fertilisers and sewage plants. A compounding factor is that water treatment plants are not designed to remove nitrate from sewage, nor are they well designed to cope with surges in rainfall, and the concomitant surges in nutrient influx into estuarine catchment areas. There is, moreover, much debate in European policy circles about how green tides should be managed, partly because we do not know the extent to which bloom formation is dependent on specific Ulva haplotypes. The elucidation of any genetic component to green tide formation would bolster the UK's commitment to evidence-based science policy, helping to decide whether efforts to combat green tides should focus on water treatment plants, altering fertiliser composition, or improving marine bioremediation, possibly through the use of other, non-bloom forming, seaweeds.

III. Algal and 'blue' biotechnology companies. Although Ulva grows abundantly in a diverse range of habitats and its mariculture as a human and animal food staple is common in Asia, its economic potential remains underexploited in European waters. The green seaweeds are, however, attracting increased interest as potential biofuel and biotechnology sources, with particular efforts being made to counter, or exploit, their biofouling and bioadhesive ability. The Ulva genome and transcriptome sequences will, therefore, be of immediate interest to biotechnology companies interested in the economic potential of algal secondary metabolites; this impact of our proposal will be further enhanced by the development of improved transformation techniques, which will allow genetic modification of green seaweed metabolism for bioprospecting and 'white' biotechnology.