Volume 59, Issue 1

The intertidal marine red alga Porphyra umbilicalis reproduces asexually in the Northwest Atlantic. We looked for population substructure among typical open-coastal and atypical estuarine habitats in seven asexual populations of P. umbilicalis from Maine to New Hampshire using eight expressed sequence tag-simple sequence repeats (EST-SSR) or microsatellite loci. Six genotypes were identified, four of which may represent recombinant genotypes from a recombination event that took place locally, or that took place prior to introduction to the Northwest Atlantic. Genotypic diversity was lowest in a population from Wiscasset, Maine, which inhabits an atypical habitat high in the intertidal zone of a bridge piling in an estuarine tidal rapid. Genotypic diversity was highest in the southernmost populations from New Hampshire; we identified two genotypes that were unique to the southernmost populations, and probably represent the most derived genotypes. We looked at genetic distances among populations in similar habitats, and found that populations were more closely related to their closest neighboring population than to a population in a similar habitat. We show that genotypic diversity within P. umbilicalis populations in the Gulf of Maine is relatively high and thus fits a model of high steady-state variation within asexual populations.

Using plastid-encoded rbc L and mitochondrial COI-5P sequence data, the species in Bermuda formerly recognized as Dichotomaria marginata was found to be a cryptic species in a wide complex of species all falling under the morphologically broad species concept for this supposed pantropical species. The new species, Dichotomaria huismanii , shows subtle anatomical and morphological differences when compared to D. marginata , and at present is only known from Bermuda. Bermuda specimens were compared with our isolates of D. marginata from St. Croix (Virgin Is.), as well as rbc L sequenced specimens with those from Guadeloupe and Puerto Rico in GenBank as D. marginata . Morphological and molecular characterization of D. marginata is provided along with the new species.

The calcified encrusting brown-algal genus Newhousia was collected in 2012 from two sites in Madang Lagoon, northern Papua New Guinea. This is the first report of that enigmatic genus since its original description in 2004 from Oahu in the Hawaiian Islands. Morphologies of thalli from both Papuan localities agree with the original diagnosis and the published figures of the Hawaiian Newhousia imbricata . Ribulose-1,5-biphosphate carboxylase large subunit ( rbc L) sequences of Papuan specimens were 96% identical to those of N. imbricata , and although there were no outstanding morphological differences between the Hawaiian and the Papuan specimens, the genetic divergence between the two strongly indicates they are not conspecific. A formal description of the new species, Newhousia yhaga , is provided and the phylogenetic implications of concatenated cox 3, psb A and rbc L sequences evaluated. A multi-marker phylogeny was generated in the hope to establish the precise phylogenetic position of Newhousia within the order Dictyotales. Even though both Bayesian inference (BI) and maximum likelihood (ML) analysis point to Newhousia being sister to Lobophora , these results are not supported by ML bootstrap values. The present documentation of Newhousia in a southwest Pacific locality considerably extends the geographical range of this unusual genus.

Dispersal of dioecious floating seaweeds could be limited due to biological constraints. This study examined for benthic and floating populations (stranded individuals) of the rafting kelp Durvillaea antarctica whether male and female individuals cohabit within one holdfast. As a previous study had indicated colour differences between sexes, we also examined whether these colour differences are consistent and possibly related to pigment and phlorotannin concentrations. Our large-scale survey of rafted holdfasts and a small-scale survey of benthic holdfasts at two sites found that reproductive males and females do travel together in coalesced holdfasts, although this proportion is relatively low (5–17%). There were no sex-specific differences in pigment and phlorotannin concentrations, but there were significant differences between the two benthic populations. There was no relationship between the colouration of thalli and the concentration of pigments but there was a slight colour difference between vegetative and reproductive sexual stages. Based on these results we conclude that biological conditions are not the cause for the lack of genetic connectivity between D. antarctica populations from central Chile. Instead, we suggest that ecological processes, such as density-blocking and physical factors (i.e. currents and winds), limit the potential for successful rafting dispersal.

Epiphytism is a major problem world-wide for the Gracilaria mariculture industry that reduces the productivity of commercial farms. Most of the epiphytes associated with Gracilaria chilensis belong to the order Ceramiales. Under laboratory conditions we studied the infection process of Ceramium rubrum rhizoids on G. chilensis collected from a northern Chilean farm. The rhizoid penetration was intercellular. The host cell wall and cortical cells adjacent to the epiphyte appeared compressed and disorganized. The rhizoids presented an extensive dynamic complex endomembrane system, mainly represented by a plentiful endoplasmic reticulum (ER) network, dictyosomes, electron dense material surrounded by ER membranes, membrane bodies and vacuolar sacs with fibrillar material. Two types of cell wall deposition can be suggested: i) one characterized by the direct contact of ER vesicles with the plasmalemma and ii) another represented by the ER contributing material to the cell wall indirectly through vacuolar sacs. This study provides the basis for a better understanding of the infection process involved in the epiphyte-host interaction.

Kelp harvesting has increased globally in recent decades and is expected to continue rising as the demand for kelp-derived products for use in aquaculture and industrial applications increases. In response, numerous studies have examined how harvesting impacts kelp populations and their associated communities, but the effects of repeated harvesting of the same individuals on the chemical properties for which they are extracted remain poorly understood. This knowledge gap may be especially crucial in areas where the same kelps are necessarily harvested multiple times per year due to their overall low abundance. To address this, we examined how repetitive harvesting of the same individuals of giant kelp, Macrocystis pyrifera , over a 3-month period influences tissue chemical properties (i.e. alginate yield, viscosity and strength, nutritional quality, such as protein, carbohydrate, lipid, crude fiber, ash and energy content, and tissue carbon/nitrogen ratios). Our results indicate that, while these properties vary over time, presumably due to variability in oceanographic conditions, repetitive harvesting of the same individuals does not significantly impact these properties.

Two Mediterranean Cystoseira taxa, namely Cystoseira foeniculacea f. schiffneri and Cystoseira funkii , are added to the macroalgal flora of Greek seas, both of them being described for the first time in the Eastern Mediterranean Sea. Descriptions, photographs, habitat type and distribution details, as well as brief notes, are provided for each taxon. Both taxa are rare, protected by the Barcelona Convention, and were found within three Natura 2000 marine Sites of Community Importance, highlighting the importance of establishing and enforcing site-specific management measures to ensure conservation of these rare, Mediterranean endemic, and little known taxa.

The pantropical seagrass Halophila decipiens (Hydrocharitaceae), representing a new record for the Andaman and Nicobar Islands, was reported from two locations: Scissostris Bay of Port Blair at 6–7 m deep and Nursery of Neil Island at 10–12 m deep. Observations on the reproductive and vegetative characters indicate that the flowering plant is monoecious, has a pair of petiolated leaves with a hairy surface and serrated leaf blade margins with 5–9 cross leaf veins. Leaf morphometric characters varied significantly between the two sites. The leaves of the Scissostris Bay specimens were smaller (1.11×0.4 cm) than the leaves of the specimens from Neil Island (1.73×0.59 cm), which might be due to the deeper depth ranges at Neil Island or other environmental factors. The present record is the 11th seagrass species from the Islands and this species could have been overlooked due to its habitat in deeper water.