Molecular genetic diversity of seaweeds morphologically related to Ulva rigida at three sites along the French Atlantic coast

Foliose species of the genus Ulva are notoriously difficult to identify due to their variable morphological characteristics and high phenotypic plasticity. We reassessed the taxonomic status of several distromatic foliose Ulva spp., morphologically related to Ulva rigida, using DNA barcoding with the chloroplastic tufA and rbcL (for a subset of taxa) genes for 339 selected attached Ulva specimens collected from three intertidal rocky sites. Two of the collection sites were in Brittany and one site was in Vendée, along the Atlantic coast of France. Molecular analyses included several museum specimens and the holotype of Ulva armoricana Dion, Reviers & Coat. We identified five different tufA haplotypes using a combination of phylogenetic analysis, with the support of several recently sequenced holotypes and lectotypes, and a species delimitation method based on hierarchical clustering. Four haplotypes were supported by validly named species: Ulva australis Areschoug, Ulva fenestrata Postels & Ruprecht, Ulva lacinulata (Kützing) Wittrock and U. rigida C. Agardh. The later was additionally investigated using rbcL. The fifth haplotype represented exact sequence matches to an unnamed species from European Atlantic coasts. Our results support: (1) the synonymy of both U. rigida sensu Bliding non C. Agardh and U. armoricana with U. lacinulata. This finding is based on current genetic analysis of tufA from the U. armoricana holotype and recent molecular characterization of the lectotype of U. laetevirens, which is synonymous to U. australis, (2) the presence of U. australis as a misidentified introduced species in Brittany, and (3) the presence of U. fenestrata and U. rigida in southern Brittany. The taxonomic history of each species is discussed, highlighting issues within distromatic foliose taxa of the genus Ulva and the need to genetically characterize all its available type specimens.

Ulva australis as a tool for monitoring metal-polluted estuarine system; spatial and temporal considerations

<p>This study investigated temporal and spatial patterns of heavy metal content in Ulva australis. Samples were collected from the Derwent Estuary, Tasmania, Australia, over 3 years (2013-2015) at locations where historically arsenic, cadmium, lead and zinc were high in sediments and seawater. Zinc and lead content were high in U. australis at all sampling times, with levels consistent with the spatial distribution of metal within the system. Zinc in Ulva varied seasonally (4.8 – 320.7 mg·kg-1), but lead did not. Zinc and lead were highest in the middle-upper estuary, close to the zinc smelter, where seawater concentrations were higher. The results suggest that spatial variation of metal content in Ulva is a reflection of variability in the seawater, which in turn indicates that U. australis could be used for monitoring the effects of metals in estuarine systems, and that U. australis could be a useful addition to existing management strategies.</p>