Band 59, Heft 5

We present the first characterization of fungal community diversity of natural mixed-species biofilms on artificial marine reefs. Four artificial reefs in the Mississippi (MS) Sound, USA, representing low-profile (underwater) and high-profile (periodically air-exposed) conditions were sampled every 3 months over a 23-month period to investigate changes in fungal diversity within reef biofilms. Fungal presence was assessed via PCR amplification of the internal transcribed spacer (ITS) region of fungal ribosomal DNA, and by terminal restriction fragment length polymorphism (T-RFLP) analysis of fungal ITS regions – the latter being used to track variation in fungal community structure with respect to season, location, and reef profile type. Fungal communities were also characterized taxonomically through both morphological identification and phylogenetic comparisons of ITS gene sequences, with 36 fungal genera cultured from reef biofilms. Using a multivariate statistical approach, significant temporal and spatial differences in fungal biofilm communities were detected. High-profile reefs differed significantly in biofilm fungal community composition across the 10 sampling periods. This assessment of marine fungal biofilm communities over time provides novel insights into the fungal diversity present on artificial reefs in an understudied region, the north-central Gulf of Mexico.

The study of genetic variation in fungi has been poor since the development of the theoretical underpinnings of population genetics, specifically in marine taxa. Corollospora maritima sensu lato is an abundant cosmopolitan marine fungus, playing a crucial ecological role in the intertidal environment. We evaluated the extent and distribution of the genetic diversity in the nuclear ribosomal internal transcribed spacer region of 110 isolates of this ascomycete from 19 locations in the Gulf of Mexico, Caribbean Sea and Pacific Ocean. The diversity estimates demonstrated that C. maritima sensu lato possesses a high genetic diversity compared to other cosmopolitan fungi, with the highest levels of variability in the Caribbean Sea. Globally, we registered 28 haplotypes, out of which 11 were specific to the Caribbean Sea, implying these populations are genetically unique. We detected populations inhabiting human-impacted sites with null genetic variation. As long-term exposure to contaminants has been proven to decrease genetic diversity, a conservation genetics approach to assess this matter is urgent. Our results revealed the occurrence of five genetic lineages with distinctive environmental preferences and an overlapping geographical distribution, agreeing with previous studies reporting physiological races within this species.

A total of 33 tropical thraustochytrid isolates were isolated from fallen leaves of Malaysian mangroves. Phylogenetic analysis based on the 18S rRNA gene revealed that the majority of the 33 isolates belonged to the genus Aurantiochytrium , and only one isolate belonged to Parietichytrium . The specific growth rate and biomass productivity of the strains ranged from 0.17 to 0.93 day −1 and 0.03 to 0.62 g l −1 day −1 , respectively. Lipid productivity ranged from 1.27 to 70.86 mg l −1 day −1 . Fifteen fatty acids, dominated by C16:0 [19.5%–71.6% total fatty acid (TFA)], C15:0 (3.3%–43.1% TFA), C22:6n3 (1.5%–38.4% TFA) and C18:0 (2.9%–28.6% TFA), were identified. The total carotenoid content was shown to be a better chemotaxonomic character than fatty acid composition for the isolates. Aurantiochytrium sp. UMACC-T024 had the highest lipid productivity (70.86 mg l −1 day −1 ), and this was selected for an optimisation study. The optimal conditions for lipid production of Aurantiochytrium sp. UMACC-T024 were salinity 32, pH 7.5, 1% w/v glucose and 0.5 g l −1 yeast extract, which resulted in an enhanced lipid productivity of 263.37 mg l −1 day −1 at day 5.

We investigated fresh collections and an isotype of Phyllophora peruviana from central Peru using morphology and sequencing the plastid rbc L gene. In the rbc L phylogenetic tree, P . peruviana consisted of three genetic groups, forming a clade. As this P. peruviana clade was distantly related to Phyllophora including the generitype Phyllophora crispa and also distinct from other genera in the Phyllophoraceae, we describe Phyllophorella peruviana gen. et comb. nov. and two new species, Phyllophorella humboldtiana sp. nov. and Phyllophorella limaensis sp. nov. The genus Phyllophorella is distinguished from Phyllophora by a compressed stipe rather than a terete stipe, and tetrasporangia in nemathecia rather than sori scattered over the thallus surface. Phyllophorella humboldtiana sp. nov. is characterized by broad blades with slightly lobate margins. Phyllophorella limaensis sp. nov. is recognized by its small, ligulate blades. Phyllophorella peruviana is distinguished by dichotomo-flabellate blades that arise from a short compressed stipe. All three species of Phyllophorella are currently known only from Peru but may be more widely distributed.

Recent phylogenetic studies of the genus Pterosiphonia suggest that Pterosiphonia dendroidea and Pterosiphonia tanakae are conspecific and show its wide geographic distribution in the Pacific. Pterosiphonia dendroidea was originally described as Polysiphonia dendroidea from Peru and later transferred to Pterosiphonia . Pterosiphonia dendroidea was characterized by diagnostic features such as its light cortication, the presence of trichoblasts, 8–12 pericentral cells, branches with the production of 3- to 5-order laterals, and congenital fusion of 2–3 segments. Pterosiphonia tanakae shares these features. Our phylogenetic analysis using rbc L sequences reveals a low gene sequence divergence (0.5%–0.7%) between the samples of P. dendroidea and P. tanakae. We propose that P. tanakae is a later synonym of P. dendroidea, and our study indicates the wide distribution of P. dendroidea in the northern and the southern Pacific Ocean.

Algal diversity has been extensively investigated using combinations of morphological and molecular approaches. These combined approaches are especially relevant for organisms where cryptic species are known to exist. Bostrychia is a widely distributed red alga commonly associated with mangroves and often exhibits cryptic diversity. Most previous studies of diversity of Bostrychia in Thailand were based solely on morphological identifications. Distribution based on morphospecies may not reveal the same phylogeographic patterns that are identifiable with genetic data. In the present study, we employed RuBisCo spacer sequences to observe patterns of genetic diversity of Bostrychia species along the coasts of the Andaman Sea (Indian Ocean) and Gulf of Thailand (Pacific Ocean) in Thailand. Our results show that, of the eight morphospecies of Bostrychia recognized on both coasts of Thailand, four ( B. binderi , B. calliptera , B. tenella and B. moritziana ) consist of multiple cryptic species. We found different distribution patterns for two cryptic species of B. binderi , one restricted to the Gulf of Thailand and the other to the Andaman Sea. Several new haplotypes were discovered for B. binderi , B. tenella and the B. moritziana / B. radicans species complex, which are mostly distributed along separate coasts of Thailand. Only through the use of molecular data were we able to determine differences in the distribution of cryptic Bostrychia species along the two coasts. These results highlight the importance of molecular data for red algal species distribution studies and also reinforce the differences between the two sides of the Thai-Malay peninsula.

Sarcothalia lanceata is a New Zealand carrageenophyte with tetrasporophytic thalli that produce carrageenan very close to the idealised structure of lambda-carrageenan. As such there is interest in its potential for commercial utilisation. There is no information on the biology and ecology of natural populations of this species, but this knowledge is critical for determining whether a species is a suitable candidate for sustainable wild harvest or for aquaculture. Population studies were conducted at two sites in New Zealand’s South Island in order to provide fundamental information on this species. The structure (abundance and composition of male, female, tetrasporophytic and non-reproductive clumps) of the two populations was assessed monthly over a year, and population biomass estimated using regression methods. Seasonal variation was not evident in most of the parameters measured, but differences between sites were found in total population density, the density of different life-history phases, and clump size and structure. The turnover in biomass occurs more frequently at the blade level than at the clump level and the presence of a basal crust in this species promotes population stability.

The seagrasses Halophila ovalis and Thalassia hemprichii commonly occur in the upper-intertidal zone where they are subjected to prolonged desiccation during low tides. This study investigated their desiccation tolerance and the mechanisms underlying their eventual recovery. Halophila ovalis exhibited a faster decline in photosynthetic efficiency, measured as effective quantum yield of photosystem II (φ PSII ), during 90 min of desiccation and did not recover when rehydrated. Thalassia hemprichii , however, showed a nearly full recovery. Desiccation also imposed greater membrane damage on H. ovalis as indicated by a higher electrolyte leakage. In a subsequent experiment, seagrasses were desiccated for 60 min before being rehydrated with seawater containing either chloramphenicol (CMP), cycloheximide (CHX), dithiothreitol (DTT) or no metabolic inhibitor (control). Recovery of φ PSII of H. ovalis was hindered by CMP and DTT while CHX had little effect. Recovery of φ PSII of T. hemprichii , however, was partially affected by both CMP and CHX to a similar extent and not by DTT. The results indicate that H. ovalis relies substantially on the synthesis of chloroplast-encoded proteins and excess energy dissipation by the xanthophyll cycle whereas T. hemprichii requires limited protein synthesis in both chloroplast and cytoplasm to completely recover their photosynthetic function from desiccation stress.