Volume 63, Issue 3

Although extensive studies have been made on Posidonia oceanica ecosystems, in terms of their phenological characteristics, shoot density, biomass, and associated faunal assemblages, little attention has been given to the depth distribution of this species in the Adriatic Sea. The depth limits of the Mediterranean endemic seagrass P. oceanica growing along the eastern coast of the Croatian Adriatic Sea were examined by the use of SCUBA diving. Fifty-two independent measurements show that the lower depth limit of P. oceanica in the Croatian Adriatic Sea ranges from 24 m in the north to 36 m in the south, with a strong latitudinal gradient. The information on maximum depth distribution is an important asset when the increased human pressure and rapid environmental changes pose a threat to the survival of this slow-growing marine species.

Halodule wrightii meadows in Southern Brazil have been regressing in an unsheltered area of the subtropical Paranaguá Bay, near their southern limit in the SW Atlantic, since 2006. To identify early indicators of regression events, we assessed variations in plant and macrobenthic structure in two local meadows under unsheltered and protected conditions. Differences between sites increased after an epiphytic overgrowth of the alga Hincksia mitchelliae at the unsheltered site. Seagrass growth was suppressed and the numbers of burrowing and opportunistic benthic species increased with the increase of algal biomass. In the protected meadow, seagrass biomass and number of leaves changed seasonally, but macrobenthic abundance and species richness remained stable. Ecosystem changes were evident when the unsheltered meadow was already collapsing. The number of leaves per shoot, the horizontal internode length, the abundance and structure of the macrofaunal associations, and the host-epiphyte surface interactions, were the first variables to reflect the early stages of seagrass regression. Our results suggest that the persistence of H. wrightii meadows at their southern distribution limit in the SW Atlantic will be affected by local hydrodynamics and their ability to compete with ephemeral macroalgal species under stress conditions.

Taxonomic difficulties have persisted within the genus Ruppia for a long time. We first unravel misconceptions as perceived on different continents and subsequently present a revised interpretation of the identity and typification of three European taxa at species level: Ruppia maritima L., Ruppia spiralis L. ex Dumortier, and Ruppia cirrhosa (Petagna) Grande. To do this, historical specimens, illustrations and original descriptions were studied. We supersede a previous choice of the figure of Buccaferrea maritima, foliis minus acutis Micheli (1729) as the lectotype of R. maritima and type species of the genus Ruppia owing to a serious conflict with the protologue. Based on a meticulous interpretation of protologues and figures in a historical context, we reject the recent view of assigning R. cirrhosa and its proposed lectotype (iconotype) as a homotypic synonym of R. maritima . We agree with an earlier lectotypification of R. spiralis , though for another reason than the above-mentioned abused homotypy. Consequently, R. cirrhosa is a synonym of neither R. maritima or R. spiralis , based on material from Petagna in the Herbarium of Naples designated as the holotype of R. cirrhosa . We argue for three species to be considered as fully independent taxa: R. maritima , R. spiralis and R. cirrhosa .

In this study we report the first finding of the red alga Acanthosiphonia echinata in the Mediterranean Sea. Specimens were identified using the DNA barcoding method and, in particular, the plastidial rbc L and the mitochondrial COI-5P markers. This species has been considered to be restricted to the western Atlantic and was reported in blooms from North Carolina to South Carolina. In 2015 the introduction of this species in Southeast Asia (Indonesia) was reported. Probably this taxon was introduced in the Mediterranean Sea from Indonesian populations associated with seaweed farming activities or hull fouling, via the western Atlantic-Mediterranean-Indonesia ship route.

Multiple abnormal individuals of Ecklonia stolonifera with thalli that developed numerous shoot-like structures on the lateral blades were found in two littoral regions of Nakanoshima in the Oki Islands, Shimane Prefecture, Japan. Except for the presence of these diagnostic structures, no other morphological differences were observed between the abnormal and normal individuals. The development of the shoot-like structures isolated from the lateral blade was the same as that of typical vegetative reproductive sporophytes that formed on stolons. In the abnormal individuals, when cultivation was performed using zoospores, the shoot-like structures were observed on the progeny after 18 months of culture and 20.0% of individuals exhibited these structures.

This review article explores the state of DNA barcoding of macroalgae in the Mediterranean Sea. Data from the Barcode of Life Data System (BOLD) were utilised in conjunction with a thorough bibliographic review. Our findings indicate that from around 1124 records of algae in the Mediterranean Sea, only 114 species have been barcoded. We thus conclude that there are insufficient macroalgal genetic data from the Mediterranean and that this area would greatly benefit from studies involving DNA barcoding. Such research would contribute to resolving numerous questions about macroalgal systematics in the area and address queries related to biogeography, especially those concerned with non-indigenous species. It could also possibly result in the development and application of better, cost-effective biodiversity monitoring programmes emanating from UN conventions and EU Directives. One possible way of achieving this is to construct DNA libraries via sequencing and barcoding, subsequently enabling better cost-effective biodiversity monitoring through environmental DNA metabarcoding.

Previously, we reported seasonal variation in iodine contents in the seagrass Zostera marina . Herein, we sought the factors controlling this variation, and investigated relationships between iodine and carbohydrate contents, using extracts and residues of seagrass samples extracted with 0.1 N HCl. In plants, carbohydrates in HCl-extracted and residual fractions are considered to represent storage and structural carbohydrates, respectively. On average, 44% and 56% of total iodine in samples was contained in the HCl-extracted and residual fractions, respectively. Both HCl-extracted and residual iodine contents showed seasonal trends similar to that of total iodine, being high in winter–spring and low in summer. Total and HCl-extracted carbohydrate contents showed reverse seasonal trends from those of iodine, whereas residual carbohydrate contents had comparable values throughout the sampling period. In the total and HCl-extracted fractions, negative correlations between iodine and carbohydrate contents were confirmed, suggesting that carbohydrates do not play important roles in iodine accumulation. Although most monosaccharide contents were not correlated with iodine contents in these two fractions, residual galactose content was positively correlated with residual iodine. We accordingly suggest that one or more specific structural carbohydrate constituents may potentially function as an iodine store in Z. marina .

Fifteen attached macroalgae from the Madeira Archipelago, comprising three green, three red and nine brown algal species, as well as two beach-cast macroalgal samples, collected along the north shore of Gran Canaria, were assessed for their biochemical properties. The analysis included the determination of total minerals, total carbohydrates, protein, lipids, chlorophyll a , total carotenoids, total phenolic content, fucoxanthin and phycobilins (allophycocyanin, phycocyanin and phycoerythrin). The results showed a high variability of biochemical composition, allowing for the targetting of specific bioresources for particular purposes, including functional foods. This work provides the foundation for a biorefinery strategy implementation plan, for which specific macroalgae may be targeted for valuable and beneficial compounds.