Band 58, Heft 1

Endophytic organisms are known to have varied effects on their host organism in terrestrial and marine environments. In previous studies on marine algae, these symbioses range from innocuous to pathogenic depending on the host and endophyte species. The present study further assessed a pathogenic relationship between filamentous algal endophytes and a red algal host from the western Antarctic Peninsula. We analyzed endophyte presence (appearance of filamentous thalli) in the three life history stages of Iridaea cordata and potential impacts on fertility in the fertilized female gametophytes (carposporophytes) and tetrasporophytes. We found that endophytes proliferate throughout significantly more thallus area in tetrasporophyte and unfertilized gametophyte hosts than in carposporophyte hosts, but there was no correlation between endophyte cover and fertility in these individuals. This study also provides a demographic analysis of I. cordata populations surrounding Palmer Station, Antarctica, showing that these populations are haploid dominated (∼78% of individuals). The differential presence of filamentous algal endophytes indicates that endophyte pathogenicity indirectly has greater effect on tetrasporophytes and unfertilized gametophytes than on the carposporophytes, which house the products of sexual recombination.

The so-called unarmoured dinoflagellates are not a “natural” (phylogenetic) group but they lack thecal plates, share fragility and possess relatively few morphological characters that can be positively identified. This study depicts the species composition of unarmoured dinoflagellates collected from sites along the coasts of the Gulf of Mexico and the Mexican Pacific and includes their descriptions and illustrations. We identified a total of 25 species belonging to 13 genera and six families that were studied through various techniques using light and scanning electron microscopy. Seven new records for the Mexican Pacific are annotated here that include Amphidinium flagelans Schiller, Gyrodinium cochlea Lebour, G . glaebum Hulburt, G . metum Hulburt, Karenia selliformis Haywood, Steidinger et MacKenzie , Karlodinium ballantinum de Salas, and K . veneficum (Ballantine) Larsen . The genera Karenia and Karlodinium belong to the family Kareniaceae, characterised for encompassing the largest number of toxic species among the unarmoured dinoflagellates, and many species produce algal blooms around the world. Ceratoperidinium falcatum and Levanderina fissa are names recently proposed elsewhere as new taxonomic combinations and are also included here. The diversity of unarmoured dinoflagellates has been strongly underestimated in the past and the new records reported here confirm this. Further studies, including traditional and modern concepts and protocols (including molecular tools), should be undertaken in the near future to understand their real diversity.

This study investigated the diversity and toxin production of cyanobacteria forming microbial mats on the soil surface and mangrove pneumatophores in three different mangrove swamps in the Red Sea off the southern coast of Saudi Arabia. In total, 34 species belonging to 15 genera and five families were recorded. Benthic mats had higher numbers of species (25–31) than pneumatophore mats (10–12). Cyanobacterial biodiversity ( H ) and species evenness ( E ) were greater in benthic mats ( H =2.52–2.83 and E =0.79–0.83) than in pneumatophore mats ( H =1.7–1.82 and E =0.73–0.74). The results showed high similarity of species between different mangrove sites (67.6%–91.7%) and low similarity between benthic and pneumatophore mats at the same site (32.3%–35.75%). During this study, only nine cyanobacterial species were successfully isolated and tested for their toxicity. The extracts of these species exhibited toxicity to Artemia salina (LC 50 =0.3–5.1 mg l -1 ). Based on the results of ELISA and HPLC analyses , four species were found to produce microcystins (683–974 μg g -1 ) and three species produced saxitoxins (58.9–93.8 μg g -1 ). The presence of toxic cyanobacteria and their toxins in mangrove swamps may pose a risk for marine animals because these toxins can accumulate in aquatic food webs with a potential for transfer to higher trophic levels.

Increasing threats to natural ecosystems from local and global stressors are reinforcing the need for baseline data on the distribution and abundance of organisms. We quantified spatial and/or temporal patterns of seagrass distribution, shoot density, leaf area index, biomass, productivity, and sediment carbon content in shallow water (0–5 m) at Lizard Island, Great Barrier Reef, Australia, in field surveys conducted in December 2011 and October 2012. Seagrass meadows were mapped using satellite imagery and field validation. A total of 18.3 ha of seagrass, composed primarily of Thalassia hemprichii and Halodule uninervis, was mapped in shallow water. This was 46% less than the area of seagrass in the same region reported in 1995, although variations in mapping methods may have influenced the magnitude of change detected. There was inter-annual variability in shoot density and length, with values for both higher in 2011 than in 2012. Seagrass properties and sediment carbon content were representative of shallow-water seagrass meadows on a mid-shelf Great Barrier Reef island. The data can be used to evaluate change, to parameterize models of the impact of anthropogenic or environmental variability on seagrass distribution and abundance, and to assess the success of management actions.

Sexual reproduction has hardly ever been reported in the Lessepsian seagrass Halophila stipulacea in the Mediterranean Sea. In the present study, fertile plants bearing fruits are reported for the first time from the North Aegean Sea, and for the second time from the whole Mediterranean Basin, confirming a successful and complete sexual reproduction of the species in the Mediterranean environment. In August 2012 on Chios Island, a large population of this plant in the northernmost limit of its Aegean Sea distribution was found and it was concluded that the fertility of the plants could be a response to the warming of the Mediterranean Sea, and may suggest that a further expansion of the species is occurring.