Volume 61, Issue 5

Seagrass ecosystems are important contributors to mitigation of climate change, since they are responsible for large carbon sinks. However, there is limited knowledge regarding the importance of variability of carbon storage in various ecosystems. In this study, we estimated carbon storage in several structurally different seagrass meadows along the west coast of Thailand and determined whether degree of exposure, human disturbance, and meadow type influenced carbon storage within these meadows. Carbon content within the living vegetation was on average 3±2.7 Mg ha −1 , whilst average storage of carbon in the sediment was 122±35.3 Mg ha −1 . Meadow type and disturbance had a significant influence on total carbon storage in the ecosystem, while the degree of exposure of the bay did not show great differences. Uniform meadows had a higher average total carbon storage than mixed meadows (133±36.2 and 110±41.3 Mg ha −1 , respectively). Undisturbed meadows had a higher average total carbon storage than disturbed ones (140±36.5 and 103±34.8 Mg ha −1 , respectively). The results obtained contribute to our understanding of carbon storage on an ecosystem scale and can provide a baseline for proper management, conservation, and climate change studies in the region.

Seagrasses are known as engineering ecosystems that play important roles in coastal environments. Globally, seagrass areas have been declining, and many conservation projects have been carried out to prevent further decline. The goal of this work was to determine how successful conservation efforts have been in a seagrass meadow at Koh Tha Rai in the Nakhon Si Thammarat Province of southern Thailand in terms of meadow extent, coverage and organic carbon storage. A study was conducted in 2017 and compared to a previous study from 2006 to determine the effects of the various conservation efforts devoted to this area. The results show that the total seagrass area increased by 0.7 ha with a rate of increase of approximately 0.06 ha year −1 . The total coverage of seagrass increased by approximately 3 times. The organic carbon in existing seagrass meadows (2006) was 53.35 Mg ha −1 , while growth was 32.34 Mg ha −1 in the areas of new seagrass. Moreover, the total organic carbon storage in the sediment increased by 26.86 MgC from 2006 to 2017 (from 211.60 MgC to 235.46 MgC). In conclusion, this study demonstrated the importance of successful conservation efforts in terms of increasing seagrass meadow areas, seagrass coverage and carbon storage within the meadow.

The overgrowth and shading of several alien species along the European Atlantic coast are expected to reduce photosynthesis of maerl, decreasing its growth and fitness. In this work, three shade levels (0, 20 and 50%) were set up under laboratory conditions to simulate different competitive scenarios potentially affecting maerl beds. Live individuals of Sargassum muticum and Undaria pinnatifida were placed over maerl cultures, and the effects of shading were assessed by chlorophyll a fluorescence using a pulse-modulated fluorescence monitoring system. Photosystem II efficiency was measured as the ratio of variable to maximal fluorescence (F v /F m ) as a proxy for the stress experienced by maerl. According to our data, irradiance reduction results in a small, yet significant, impact on the PSII efficiency of maerl, which could have fitness consequences.

Completion of the Porphyra umbilicalis genome and ongoing research on this species by many investigators suggest the need for wider appreciation of regional specialisation of the P. umbilicalis blade. Here we use light and electron microscopy to describe four distinct regions of the blade: rhizoid cells with abundant floridean starch, vegetative cells, differentiating neutral sporangia, and mature neutral spores. The holdfast, densely covered by microorganisms, presents an intriguing biomechanical structure: thousands of very thin, long rhizoid tips course through the thick, secreted polysaccharide to the substratum. Wild blades in culture have more microorganisms than when collected, including filamentous cyanobacteria.

Challenges in morphology come to bear when assigning specific names in foliose Bangiales. Recent studies suggest that the integration of molecular and phenotypic data is essential, particularly in setting species boundaries and revealing the true species diversity of a given area. In an attempt to further elucidate the diversity of foliose Bangiales in the Philippines, two new species, Pyropia lunae sp. nov. and Pyropia islae sp. nov. are described. Each species differs from other closely related taxa by a combination of morphological and anatomical characters, and nucleotide sequences. Phylogenetic reconstruction based on rbc L gene sequences supports the sister relationship of P. lunae and Pyropia acanthophora , whereas P. islae is recovered as a species allied to Pyropia tanegashimensis and Pyropia denticulata . These two previously undescribed species increase the number of confirmed Philippine Pyropia species to four. So far, P. lunae and P. islae are found only from the Batanes Islands while P. acanthophora and P. tanegashimensis are known to extend their native distributions across into the Indo-Pacific waters. Questions remain, however, with regard to the true species diversity of foliose Bangiales in the Philippines. A wider sampling effort and the application of molecular methods will make it possible to resolve the remaining gaps in the taxonomy of Philippine foliose Bangiales.

An updated checklist of the benthic marine algae (seaweeds) of the Northern Arabian Sea coast of the Sultanate of Oman is presented, with a total of 402 taxa, consisting of 75 taxa of brown algae (Phaeophyceae), 238 taxa of red algae (Rhodophyta), and 89 taxa of green algae (Chlorophyta). Obsolete names and taxonomic synonyms as well as information on mis-identified names are provided. The classification in many instances reflects new ideas derived from the results of molecular-based phylogenetics. A total of 18 taxa of benthic marine algae are newly reported for Oman.

Molecular resources and transgenic studies in red algae are lagging behind those for green algae. The Agrobacterium -mediated gene-transfer method routinely used in plant transformation has not been fully utilised in the red algae, which, as an important source of phycocolloids, warrant more studies. In this regard, a stepwise methodology was developed for Agrobacterium -mediated transformation of the carrageenophyte Chondrus crispus using pCAMBIA 1301 and a construct featuring a codon-optimized beta-glucuronidase ( GUS ) reporter gene driven by the endogenous Chondrus actin promoter. The effects of several factors on transformation efficiency were investigated. An intimate association of Chondrus and bacterial cells was observed using scanning electron microscopy. GUS transient expression within Chondrus cortical and medullary cells with both expression cassettes testified to the amenability of Chondrus to Agrobacterium -mediated transformation. Darker staining, indicative of higher GUS activity, was observed with the Chondrus -specific construct, suggesting its superiority over the pCAMBIA 1301. Presence of acetosyringone, the wounding method and the type of co-cultivation medium significantly affected the transformation outcome and efficiency. The Agrobacterium -mediated transient expression presented here constitutes a first step towards tailoring a transformation strategy for Chondrus , which can serve to facilitate further transgenic studies in this important red alga.

Plant respiratory burst oxidase homologs (rbohs), a source of reactive oxygen species (ROS), play a central role in the response to biotic and abiotic stresses in plants. Here, an rboh gene from the seaweed Gracilariopsis lemaneiformis ( Glrboh ) was characterized and analyzed in terms of its structure and changes in its expression profile in response to high salinity, high temperature and phytohormone treatments. The results show that high salinity and high temperature mostly induced Glrboh expression at the mRNA, protein and enzyme activity levels within 3–6 h, and the levels decreased thereafter, but there was an almost continuous decline in Glrboh mRNA during the 24 h following exposure to high temperature. Under heat stress, abscisic acid (ABA) dramatically enhanced the levels of Glrboh mRNA at 3 h and increased Glrboh protein expression and enzyme activity throughout most of the 24-h period. However, salicylic acid (SA) and methyl jasmonate (MJ) had only slight and varied effects on Glrboh expression. These results indicate that Glrboh is involved in heat and salt stress responses and that the phytohormone ABA is more closely related to ROS production in this alga than SA and MJ.