Jane Fromont

Assessing the complex sponge microbiota: core, variable and species-specific bacterial communities in marine sponges.

Marine sponges are well known for their associations with highly diverse, yet very specific and often highly similar microbiota. The aim of this study was to identify potential bacterial sub-populations in relation to sponge phylogeny and sampling sites and to define the core bacterial community. 16S ribosomal RNA gene amplicon pyrosequencing was applied to 32 sponge species from eight locations around the worlds oceans, thereby generating 2567 operational taxonomic units (OTUs at the 97% sequence similarity level) in total and up to 364 different OTUs per sponge species. The taxonomic richness detected in this study comprised 25 bacterial phyla with Proteobacteria, Chloroflexi and Poribacteria being most diverse in sponges. Among these phyla were nine candidate phyla, six of them found for the first time in sponges. Similarity comparison of bacterial communities revealed no correlation with host phylogeny but a tropical sub-population in that tropical sponges have more similar bacterial communities to each other than to subtropical sponges. A minimal core bacterial community consisting of very few OTUs (97%, 95% and 90%) was found. These microbes have a global distribution and are probably acquired via environmental transmission. In contrast, a large species-specific bacterial community was detected, which is represented by OTUs present in only a single sponge species. The species-specific bacterial community is probably mainly vertically transmitted. It is proposed that different sponges contain different bacterial species, however, these bacteria are still closely related to each other explaining the observed similarity of bacterial communities in sponges in this and previous studies. This global analysis represents the most comprehensive study of bacterial symbionts in sponges to date and provides novel insights into the complex structure of these unique associations.

Climate-driven regime shift of a temperate marine ecosystem

No turning back? Ecosystems over time have endured much disturbance, yet they tend to remain intact, a characteristic we call resilience. Though many systems have been lost and destroyed, for systems that remain physically intact, there is debate as to whether changing temperatures will result in shifts or collapses. Wernburg et al. show that extreme warming of a temperate kelp forest off Australia resulted not only in its collapse, but also in a shift in community composition that brought about an increase in herbivorous tropical fishes that prevent the reestablishment of kelp. Thus, many systems may not be resilient to the rapid climate change that we face. Science, this issue p. 169 Rapid warming tropicalizes a temperate kelp forest. Ecosystem reconfigurations arising from climate-driven changes in species distributions are expected to have profound ecological, social, and economic implications. Here we reveal a rapid climate-driven regime shift of Australian temperate reef communities, which lost their defining kelp forests and became dominated by persistent seaweed turfs. After decades of ocean warming, extreme marine heat waves forced a 100-kilometer range contraction of extensive kelp forests and saw temperate species replaced by seaweeds, invertebrates, corals, and fishes characteristic of subtropical and tropical waters. This community-wide tropicalization fundamentally altered key ecological processes, suppressing the recovery of kelp forests.

The Biogeography and Phylogeny of Unicellular Cyanobacterial Symbionts in Sponges from Australia and the Mediterranean

The distribution, host associations, and phylogenetic relationships of the unicellular cyanobacterial symbionts of selected marine sponges were investigated with direct 16s rDNA sequencing. The results indicate that the symbionts of the marine sponges Aplysina aerophoba, Ircinia variabilis, and Petrosia ficiformis from the Mediterranean, four Chondrilla species from Australia and the Mediterranean, and Haliclona sp. from Australia support a diversity of symbionts comprising at least four closely related species of Synechococcus. These include the symbionts presently described as Aphanocapsa feldmannii from P. ficiformis and Chondrilla nucula. A fifth symbiont from Cymbastela marshae in Australia is an undescribed symbiont of sponges, related to Oscillatoria rosea. One symbiont, Candidatus Synechococcus spongiarum, was found in diverse sponge genera in the Mediterranean Sea and the Indian, Pacific, and Southern oceans, whereas others were apparently more restricted in host association and distribution. These results are discussed in terms of the biodiversity and biogeographic distributions of cyanobacterial symbionts.

Inter-generational transmission of microbial symbionts in the marine sponge Chondrilla australiensis (Demospongiae)

Mechanisms for the biparental transmission of microbial symbionts to offspring in the marine sponge Chondrilla australiensis are reported. The observation of microbial mutualists in the sperm of C. australiensis is the first report of this kind in any organism, as far as we are aware. The developing eggs were shown by transmission electron microscopy (TEM) to incorporate intercellular cyanobacterial and bacterial symbionts. Nurse cells appeared to transport cyanobacterial symbionts from the surface layers of the sponge to eggs deeper in the matrix, where they were incorporated into the egg cytoplasm prior to spawning. This suggests that a host mechanism exists to actively recognise and incorporate symbionts, ensuring that larvae contain these mutualists before settlement. In addition, an average of 1.64% of mature sperm of C. australiensis contained cyanobacterial symbionts in their cytoplasm. The successful transmission of cyanobacterial symbionts to larvae was demonstrated by autofluorescent microscopy and TEM. The occurrence of organisms with functional mechanisms for transmission of symbionts from both parents to offspring provides the potential for new insights into the nature of host-symbiont interactions.

Marine sponges of the Dampier Archipelago, Western Australia: patterns of species distributions, abundance and diversity

Quantitative surveys revealed high diversity (species richness) of sponges (150 species) in the previously little explored Dampier Archipelago, northwestern Australia. Classification analyses disclosed 11 station groups with high internal heterogeneity in species composition, however some spatial patterns were evident. The composition of sponge assemblages varied with environmental factors such as substrate type (coral, igneous rock, limestone rock), aspect (exposed, protected), substrate configuration (limestone platform, dissected reef) and depth. Most of the species (61%) reported from the Dampier Archipelago were rare (found at one or two stations). The number of species found at only one location was high (48%), supporting previous findings that northwestern Australia has high sponge endemism. As a result of all sponge surveys undertaken in the archipelago (qualitative and quantitative, subtidal and intertidal), 275 sponge species have now been reported from the area. This number indicates high species diversity in the region. Estimations of diversity based on non-parametric modelling suggests that there are potentially more species (range 245–346) than presently recorded in the archipelago.

Nakijiquinones G-I, new sesquiterpenoid quinones from marine sponge.

Three new sesquiterpenoid quinones, nakijiquinones G-I (1-3), containing a different amino group derived from amino acids have been isolated from Okinawan marine sponges of the family Spongiidae, and the structures and relative stereochemistry of 1-3 were elucidated on the basis of the spectral data. Nakijiquinones G-I (1-3) showed modest cytotoxicity and inhibitory activity against HER2 kinase, while nakijiquinone H (2) exhibited antimicrobial activity.

Bromopyrrole alkaloids from marine sponges of the genus Agelas.

Four new bromopyrrole alkaloids, nagelamides O (1) and P (2) and mukanadins E (3) and F (4), were isolated from three collections of Okinawan marine sponges of the genus Agelas. The structures and stereochemistry of 1-4 were elucidated on the basis of their spectroscopic data.

Sexual reproduction in Chondrilla australiensis (Porifera : Demospongiae)

Increasingly, sponges are being used as models for a wide range of biological systems. However, little is known about the reproductive biology of a group that has been shown to lack gonads or gonadal ducts. The development of gametes in the oviparous demosponge Chondrilla australiensis at Fremantle, Western Australia, was investigated using light microscopy and transmission electron microscopy over 5 years. Results indicate that C. australiensis is gonochoric and oviparous. Egg and sperm development were first apparent inside choanocyte chambers, with both types of gamete apparently developing from choanocytes. During egg development, large numbers of nurse cells appeared attached to eggs, with which they fused at the time of spawning. The origin of the nurse cells remains unclear, but they may also have a choanocyte origin. Eggs took 4 weeks to develop and sperm took approximately 2 weeks, during which time the nucleus condensed and the cytoplasm reduced. Mature sperm could occupy almost the entire matrix of fecund males and were not contained in cysts. Spawning occurred in late summer and autumn over a period of 4-5 days, when the tides were at the maximum height for the month.

Nagelamides K and L, Dimeric Bromopyrrole Alkaloids from Sponge Agelas Species

Two new dimeric bromopyrrole alkaloids, nagelamides K (1) and L (2), have been isolated from Okinawan marine sponges Agelas species, and the structures and stereochemistry were elucidated from spectroscopic data. Nagelamide K (1) is a bromopyrrole alkaloid possessing a rare piperidinoiminoimidazolone ring with an aminoimidazole ring and a taurine unit, while nagelamide L (2) is a unique dimeric bromopyrrole alkaloid containing an ester linkage. Nagelamides K (1) and L (2) exhibited antimicrobial activity.

The sponge gardens of Ningaloo Reef, Western Australia

Preliminary results from biodiversity surveys in the deeper waters of Ningaloo Marine Park, Western Australia revealed that while much of the area is composed of sediments and rhodolith fields with low densities of macro- epibenthos, locally dense and extensive filter feeding communities exist. They were distinctly dominated by demosponges, both in biomass and diversity. A subsample of dominant taxa determined by fresh weight yielded 155 different demosponge species from over 350 transects between 18-102 m depth. Data from three successive years of sampling indicated that only a few species were ubiquitous, suggesting that as minor species are identified the cumulative species list will significantly exceed the present species record. This implies greatly enhanced biodiversity values associated with Ningaloo Marine Park, complementing records attributed to the shallow coral reef environment. The richness of the observed filter feeding communities adds additional weight to the increasing perception of Australia as a global hotspot for Porifera biodiversity.