Native, invasive and cryptogenic Ulva species from the Israeli Mediterranean Sea: risk and potential

Abstract

The genus Ulva (Chlorophyta) is ubiquitous along Israeli Mediterranean shores where it has been studied extensively due to its important ecological role and potential value in biotechnology and aquaculture. Previous identifications of Ulva in Israel were based only on morphology. Here, we compare species found in 2002 and in 2014-2016. Analyses of ribulose-1,5-bisphosphate carboxylase/oxygenase (rbcL) and elongation factor 1-alpha (tufA) plastid genes (2014-2016 samples only), combined with morphological data, identified six Ulva species, three of which are new records for Israel and probably originate from the Indo-Pacific. Ulva compressa, rarely found in 2002, is now the most abundant species and exhibits two fairly distinct morphologies correlated with different haplotypes for both genes.  Ulva fasciata was found more commonly in 2002 than in 2014-16, whereas the morphologically similar, and closely related, invasive species U. ohnoi seemed more frequent in recent samples.  The finely branched tubular Ulva tepida was found in 2002 and 2015/16, and U. chaugulii and U. mediterranea were discovered for the first time in 2015/16.  The changing Ulva flora of the Israeli Mediterranean may be correlated with major environmental changes including 3°C increase in sea surface temperatures over the last two decades, as well as a generally increasing prevalence of non-native species.  The local Ulva species now found in Israel could be of value for various industrial uses.