Diel shifts in the structure and function of nearshore estuarine fish communities.

Day-night shifts in the nearshore fish fauna of a temperate microtidal estuary were assessed using a holistic suite of structural and functional community attributes. Mean fish species richness and diversity (taxonomic distinctness) were higher at night across all regions of the estuary and seasons, concurring with the findings of numerous comparable studies reviewed worldwide, while the diel period in which mean abundance was higher varied among seasons. Likewise, species and functional guild compositions (the latter based on feeding modes and habitat use) both differed significantly between day and night, with the extent of the diel shift again varying seasonally. Daytime fish communities were characterized by higher abundances of Atherinidae, Sillaginidae and Mugilidae, while Gobiidae were far more abundant at night. Marked shifts in size composition were also evident, with smaller fishes (<100 mm total length, LT ) being more prevalent during the day and larger fishes (≥200 mm LT ) proportionally more abundant at night. The above diel shifts were feasibly related to a range of predator-prey interactions and feeding-related movements, namely a nocturnal decrease in top-order avian piscivory coupled with an increase in invertebrate prey availability, resulting in changes in the presence and catchability of certain fish species in shallow estuarine waters.

A complex life cycle in a warming planet: gene expression in thermally stressed sponges.

Sponges are abundant, diverse and functionally important components of aquatic biotopes with crucial associations for many reef fish and invertebrates. Sponges have strict temperature optima, and mass mortality events have occurred after unusually high temperatures. To assess how sponges may adapt to thermal stress associated with a changing climate, we applied gene expression profiling to both stages of their bipartite life cycles. Adult Rhopaloeides odorabile are highly sensitive to thermal stress (32 °C), yet their larvae can withstand temperatures up to 36 °C. Here, we reveal the molecular mechanisms that underpin these contrasting thermal tolerances, which may provide sponges with a means to successfully disperse into cooler waters. Heat shock protein 70 was induced by increasing temperature in adult sponges, and genes involved in important biological functions including cytoskeleton rearrangement, signal transduction, protein synthesis/degradation, oxidative stress and detoxification were all negatively correlated with temperature. Conversely, gene expression in larvae was not significantly affected until 36 °C when a stress response involving extremely rapid activation of heat shock proteins occurred. This study provides the first transcriptomic assessment of thermal stress on both life history stages of a marine invertebrate facilitating better predictions of the long-term consequences of climate change for sponge population dynamics.

Same, same but different: symbiotic bacterial associations in GBR sponges.

Symbioses in marine sponges involve diverse consortia of microorganisms that contribute to the health and ecology of their hosts. The microbial communities of 13 taxonomically diverse Great Barrier Reef (GBR) sponge species were assessed by DGGE and 16S rRNA gene sequencing to determine intra and inter species variation in bacterial symbiont composition. Microbial profiling revealed communities that were largely conserved within different individuals of each species with intra species similarity ranging from 65-100%. 16S rRNA gene sequencing revealed that the communities were dominated by Proteobacteria, Chloroflexi, Acidobacteria, Actinobacteria, Nitrospira, and Cyanobacteria. Sponge-associated microbes were also highly host-specific with no operational taxonomic units (OTUs) common to all species and the most ubiquitous OTU found in only 5 of the 13 sponge species. In total, 91% of the OTUs were restricted to a single sponge species. However, GBR sponge microbes were more closely related to other sponge-derived bacteria than they were to environmental communities with sequences falling within 50 of the 173 previously defined sponge-(or sponge-coral) specific sequence clusters (SC). These SC spanned the Acidobacteria, Actinobacteria, Proteobacteria, Bacteroidetes, Chloroflexi, Cyanobacteria, Gemmatimonadetes, Nitrospira, and the Planctomycetes-Verrucomicrobia-Chlamydiae superphylum. The number of sequences assigned to these sponge-specific clusters across all species ranged from 0 to 92%. No relationship between host phylogeny and symbiont communities were observed across the different sponge orders, although the highest level of similarity was detected in two closely related Xestospongia species. This study identifies the core microbial inhabitants in a range of GBR sponges thereby providing the basis for future studies on sponge symbiotic function and research aiming to predict how sponge holobionts will respond to environmental perturbation.

Temperature and spatiotemporal variability of Salicylihalamide A in the sponge Haliclona sp.

The production of salicylihalamide A by the marine sponge Haliclona sp. was investigated. Samples of the two morphologies (green and brown) were collected from four locations covering approximately 1,200 km of coastline. Temporal variation between winter and summer was also examined at Bremer Bay. Chemical profiling by using liquid chromatography coupled with ultra violet detection and mass spectrometry showed that salicylihalamide A was produced only by the green morphology. Salicylihalamide A concentration was significantly correlated to water temperature but not to the size or depth of the sponge. Salicylihalamide A concentration was found to differ significantly among locations (Bremer Bay 13.5 microg g(-1), Hamelin Bay 11 microg g(-1), Rottnest Island 9.9 microg g(-1), and Jurien Bay 8.5 microg g(-1)) partially accounted for by the influence of water temperature. A difference between seasons was also observed in Bremer Bay (summer concentration of 13.5 microg g(-1) vs. winter concentration of 8.2 microg g(-1)). Environmental and physiological factors appear to be important in the production of salicylihalamide A by the green morphology. Additionally, the brown morphology does not produce salicylihalamide A, thus adding to the evidence that this morphology may be a different species.

The multiplex-PCR-based detection and genotyping of diarrhoeagenic Escherichia coli in diarrhoeal stools.

In several hospitals in Beirut, Lebanon, 77 isolates of Escherichia coli were successfully derived from the stools of patients with diarrhoeal diseases, by culture on MacConkey or MacConkey-sorbitol agar. When the isolates were screened, using a multiplex PCR, 14 (from 14 different patients) were each found positive for one of the various genes defining the enterotoxigenic (five), enteroinvasive (four), enteroaggregative (three) or enteropathogenic (two) groups. Genotyping of these 14 diarrhoeagenic isolates, by pulsed-field gel electrophoresis, indicated that all were genomically distinct with the exception of two of the enteroaggregative isolates (which were of the same genotype). The E. coli apparently involved in diarrhoeal disease in Beirut therefore belong to at least four different diarrhoeagenic groups and show strain variation within each group. Diarrhoea in the absence of diarrhoeagenic E. coli may be the result of infection with bacteria other than E. coli or viral or parasitic enteropathogens.