Volume 60, Issue 1

Variations in utricle morphology may be responsible for different tolerances to ocean acidification (OA) within the macroalgal genus Halimeda , an important sediment producer on reefs. However, differences in species’ utricle morphology and their relationship to calcification and crystal formation have not been well articulated. In the present study, we characterized the utricle morphologies of six Halimeda species. Primary utricle ultrastructure was quantitatively and qualitatively compared to tissue inorganic content and crystal microstructure. Morphologies differed across species and several morphometric relationships were revealed. Primary utricle size (r 2 =0.70) and diffusion pathway length (r 2 =0.87) had inverse relationships with inorganic content based on regression analyses, and corresponded to crystal microstructure form. Species with large utricles and long diffusion pathways contained more narrow (~0.15 μm) aragonite needles and minimal micro-anhedral crystal formations. In contrast, species with small utricles and short diffusion pathways elucidated aggregates of micro-anhedral crystals and wider aragonite needles (~0.30 μm). Species’ utricle characteristics generally corresponded to specific evolutionary lineages. Thus, characteristics of Halimeda utricle morphology may control long-term adaptive responses to OA, an idea articulated in the broader literature.

Red algal parasites are diverse organisms that are unusual due to the fact that many are closely related to their hosts. Parasitism has developed many times within different red algal groups, but the full extent of parasite biodiversity is unknown, as parasites are easily overlooked due to their small size and often low abundance. Additionally, the literature on red algal parasites is dispersed and has not been compiled in over 30 years. Although criteria have been proposed to define what constitutes a red algal parasite, many parasites are poorly described, and the cellular interactions with their host are poorly known. A few studies have demonstrated that parasites transfer organelles to host cells, which can alter the physiology of the host to the benefit of the parasite. Here, we apply a set of defining criteria for parasites to a compiled list of all described red algal parasites. Our results highlight the lack of knowledge of many key parasitic processes including early parasite development, host cell “control”, and parasite origin. Until the biology of more parasites is studied, generalisations on the processes of parasitism in red algae may be premature. We hope this synopsis will stimulate research into this fascinating group.

The aim of the present work was to evaluate the effects of copper (Cu) and cadmium (Cd) on the physiology of the red macroalga Porphyra haitanensis Chang and Zheng. The alga was cultured in media with different Cu or Cd concentrations for 7 days. The relative growth rate was significantly reduced at Cu concentrations of 0.10 mg l −1 and above or at Cd concentrations of 4 mg l −1 and above. Chlorophyll a (Chl a ), carotenoids (Car), phycoerythrin (PE) and phycocyanin (PC) contents decreased at high Cu or Cd concentrations, and PE content increased at 0.10 mg l −1 Cu or 4–8 mg l −1 Cd. Moreover, the optimal quantum yield, maximum net photosynthetic rate (P m ) and apparent photosynthetic efficiency (α) were significantly reduced at high Cu or Cd concentrations. In contrast, malondialdehyde (MDA) content and superoxide dismutase (SOD) activity increased in response to Cu or Cd treatment. Catalase activity increased at 2–8 mg l −1 Cd and significantly declined at 0.50 mg l −1 Cu or 10 mg l −1 Cd. Nitrate reductase (NR) activity declined at high Cu or Cd concentrations. Consequently, both Cu and Cd were physiological stressors for P. haitanensis , with Cu being more toxic than Cd. This work has generated valuable knowledge about the toxic effects of Cu and Cd on macroalgae.

The aim of this study was to determine the temperature effects on photosynthesis, growth and reproduction in gametophytes of Alaria esculenta (Linnaeus) Greville and Saccharina latissima (Linnaeus) C.E. Lane, C. Mayes, Druehl et G.W. Saunders from the Artic waters. After 24 days of culture, no gametophytes of either species survived at 20°C. Most growth parameters were greater at 10–15°C than at 5°C. Length and width were similar for both species, but area was greater for A. esculenta and cell number was greater for S. latissima . Female gametophytes were larger than male gametophytes in width and area, but the opposite was observed in cell number. In A. esculenta , but not for S. latissima , the percentage of female gametophytes decreased with increasing temperature. Alaria esculenta female gametophytes produced more sporophytes at 5°C than at 10°C, with no sporophytes at 15°C. In S. latissima , all female gametophytes produced sporophytes at both 5°C and 10°C, with a small percentage of sporophytes at 15°C. Saccharina latissima still had a measurable F v /F m at 20°C, while the F v /F m of A. esculenta was zero at this temperature. Maximum relative electron transport rate (rETR max ) and non-photochemical quenching (NPQ) were constant in the male and female gametophytes of A. esculenta and the male gametophytes of S. latissima at temperatures between 5°C and 15°C. Photosynthesis was saturated at a higher irradiance in A. esculenta than in S. latissima .

The aim of the study was to evaluate the role of the presence of an adult canopy on the recruitment of the habitat-forming seaweed Cystoseira brachycarpa var. balearica , in the northwestern Mediterranean Sea. To achieve this objective, a field experiment was performed and recruitment was estimated both in the middle and at the edge of cleared patches, as well as within the bed, on ceramic tiles anchored to the rocky substrate. At the end of the study, neither the number nor the heights of Cystoseira thalli were significantly different among the positions, suggesting that there were no facilitating or inhibiting effects on recruitment.

Most data on the White Sea flora are scattered in Russian publications and are largely inaccessible to researchers. The aim of the present work is to compile a checklist as well as to provide verification of the species composition of the Rhodophyta of the White Sea. This checklist is based on an exhaustive bibliographic search. As a result of a careful revision, a total of 61 species of Rhodophyta has been revealed, and 17 species and one forma were excluded on the basis of being doubtful records or misidentifications. The distribution of four species in the White Sea was clarified. Nineteen species occur throughout the White Sea, six species are widespread except for Mezen Bay, whereas seven taxa are restricted to the northern regions of the White Sea. The analysis of the species composition permits the red algal flora of the White Sea to be interpreted as representing the depleted Barents Sea flora. An extensive bibliography and data on the presence of the specimens in the Komarov Botanical Institute of the Russian Academy of Sciences are given.

Eight collections of the type material of Lithothamnion engelhartii from Cape Jaffa and Kingston (South Australia) were re-examined and two disparate entities were shown to be included. Some specimens exhibit embedded conceptacles in the thallus where the perithallium dominates. The other specimens lack embedded conceptacles and the thallus is formed by unattached-superimposed lamellae where the hypothallium prevails. The lectotype selected here fits the second description and is in agreement with most other type specimens and recent material collected at Eyre Peninsula (South Australia). The lectotype specimen displays dorsiventral organization lacking perithallial protuberances. The hypothallium is polystromatic with coaxial to non-coaxial regions and forms a relatively thin ascending perithallium. Subepithallial cells are elongate and support single flattened epithallial cells. Multiporate conceptacles are bisporangial, develop in dense aggregations, and do not become embedded in the thallus (except via superimposition of new lamellae). Pore canals are conical to pyriform and develop differentiated cells lining the canals along the base. Syntype material exhibits simple spermatangia, and this character, together with the presence of elongate basal pore cells and the lack of a predominantly coaxial hypothallium, suggests an affiliation with the temperate species of Leptophytum from the NE Pacific.

The aim of this study was to describe the morphology of species of the benthic dinoflagellate genus Sinophysis from the tropical South Atlantic. Species were collected from four sampling sites and were identified based on light and epifluorescence microscopy. Sinophysis microcephala was found at three sites. Cells were elongated and oval in lateral view. Sinophysis canaliculata was recorded at two sites. Cells were round in lateral view and a short cut was present at the H 2 plate. To the best of our knowledge, this is the first record of the genus Sinophysis from the South Atlantic Ocean.