Gemmules of sponges from a warm lake

1. Two types of gemmules were found, each in a different species of sponge, from the warm monomictic Lake Kinneret: (i) clustered gemmules, sharing the pneumatic layer of the gemmular capsule and resembling gemmules of Eunapius ; (ii) gemmules that develop non-synchronously, containing amphidisc spicules within the gemmular capsule and resembling those of Ephydatia . Algal cells were not detected within either type of gemmule although they exist in the developed sponges.
2. Sponges began producing gemmules in the lake with the onset of lake drawdown and ceased when lake level was minimal. The gemmules hatched when the lake level began to rise.
3. Under experimental conditions gemmules hatched between 13 and 35 °C. Germination was optimal at 20–25 °C. Chilling of young gemmules prior to incubation at 25 °C improved germination rate.
4. The percentage of germinating dry gemmules diminished 4–6 months after their collection from the lake. None germinated after 10 months. Submerged gemmules maintained high viability with ageing (up to 100% germination 18 months after collection). Desiccation influenced gemmule viability over time, by both decreasing the percentage of germinating gemmules and increasing the lag time before onset of germination.
5. Gemmules kept in the dark germinated significantly less than those illuminated for 12 h day     

Vulnerability of a large monomictic lake (Lake Biwa) to warm winter event

Detailed cross-sectional temperature and oxygen distributions during winter were examined over 5 years (2003–2007) in large, warm, monomictic Lake Biwa. The distribution patterns showed year-to-year variation in the degree of spatial heterogeneity and indicated that both convective mixing and gravity currents contributed to the delivery of oxygen to the profundal zone. We encountered a warm winter in 2007, when deep-water oxygenation was delayed by more than a month relative to normal years. Data obtained during the period of oxygenation in 2007 suggest that the timing of complete oxygenation of the bottom water (or lower layers of the hypolimnion) was controlled by physical processes responsible for destruction of the weak thermal stratification near the bottom. This study revealed that Lake Biwa is sensitive to year-to-year variations in winter meteorological conditions. Specifically, the bottom environments are highly susceptible to a warm winter, especially when it follows a cold winter.     

Biogeochemical response to physical forcing in the water column of a warm monomictic lake

Based on microstructure measurements of temperature and horizontalcurrent velocity the physical structure in the water column of Lake Kinneretwascharacterized as a five layer system consisting of a surface mixed layer, lowerepilimnion, metalimnion, upper hypolimnion and benthic boundary layer. Usingoxygen and hydrogen sulfide as natural chemical tracers, the time scale ofchemical change was identified in relation to advection, mixing and biologicalprocesses. Rapid changes due to advection that took place on an hourly timescale were removed by referring the data back to the temperature of the water.Biological activity dominated the hydrochemical changes observed in the meta-and upper hypolimnion. These were expressed by DO depletion rates of 2.0 and0.4g m^–2 d^–1, respectively.Verticaland horizontal mixing were shown to occur on a seasonal time scale. Once thechemical stratification process was completed the slow mixing through thebenthic boundary layer became the limiting factor for subsequent reactions inthe water column.     

Sterols from some sponges

The sterol composition of four sponges was determined by a combination of gas chromatography and mass spectrometry. Cliona viridis and Chondrosia reniformis contained mainly C₂₇-C₂₉Δ⁵ mono- and di-unsaturated sterols. Halichondria bowerbanki and Hymeniacidon sanguinea contained stanols and Δ⁵-sterols. Cholestanol was the major component of the sterol mixtures.     

Tropical macrophytes promote phytoplankton community shifts in lake mesocosms: relevance for lake restoration in warm climates

Hydrobiologia - Macrophytes can be crucial for maintaining clear water conditions in temperate shallow lakes. However, their restorative potential and role in regulating phytoplankton remains...     

Marine lake populations of jellyfish,mussels and sponges host compositionally distinct prokaryotic communities

Hydrobiologia - Marine lakes represent a unique aquatic environment. Here, we tested if prokaryotic communities of water, sediment, jellyfish, mussel and sponge biotopes differed in composition,...     

Novel actinobacteria from marine sponges

Actinobacteria exclusively within the sub-class Acidimicrobidae were shown by 16S rDNA community analysis to be major components of the bacterial community associated with two sponge species in the genus Xestospongia. Four groups of Actinobacteria were identified in Xestospongia spp., with three of these four groups being found in both Xestospongia muta from Key Largo, Florida and Xestospongia testudinaria from Manado, Indonesia. This suggests that these groups are true symbionts in these sponges and may play a common role in both the Pacific and Atlantic sponge species. The fourth group was found only in X. testudinaria and was a novel assemblage distantly related to any previously sequenced actinobacterial clones. The only actinobacteria that were obtained in initial culturing attempts were Gordonia, Micrococcus and Brachybacterium spp., none of which were represented in the clone libraries. The closest cultured actinobacteria to all the Acidimicrobidae clones from Xestospongia spp. are Microthrix parvicella and Acidimicrobium spp. Xestospongia spp. can now be targeted as source material from which to culture novel Acidimicrobidae to investigate their potential as producers of bioactive compounds. Isolation of sponge-associated Acidimicrobidae will also make it possible to elucidate their role as sponge symbionts.     

Antiproliferative homoscalarane sesterterpenes from two Madagascan sponges

Dereplication of the antiproliferative ethyl acetate fraction of the Madagascan sponge Carteriospongia sp. led to the detection and isolation of the two known homoscalarane-type sesterterpenes 1 and 2. Investigation of a similar sponge containing closely related compounds afforded the four new antiproliferative homoscalarane sesterterpenes (3 and 5?7). The structures of all isolated compounds were elucidated by spectroscopic methods, including UV, IR and 1D and 2D NMR. Compounds 1, 3 and 5 displayed submicromolar antiproliferative activity against the A2780 ovarian cell line with IC₅₀ values of 0.65, 0.26 and 0.28 μM, respectively, while compounds 6 and 7 showed moderate activity (4.5 and 8.7 μM, respectively). Compounds 3 and 5 also displayed anti-proliferative activity against the H522-T1 non-small cell lung and A2058 human melanoma cancer cell lines.     

Classes of lipids in marine sponges from Kenya

The classes of lipid demonstrated in eight species of African sponges are described. Structural lipids are dominant while glycerides are common although variable in quantity. There are triglycerides, and glyceryl ether diesters. Steryl esters were found in all except one species.A wide variety of pigmented substances, up to ten in one species, is characteristic of most of the species studied.     

Observations on Chrysophyceae from a Norwegian mountain lake

Chrysosphaerella coronasircumspina Wujek & Kristiansen and Spiniferomonas bilacunosa Takahashi have been shown by electron microscopy to be regular members of the phytoplankton society in an oligotrophic Norwegian mountain lake. This is the first published record of these species in Norway.     

Lipase-producing microorganisms from a Kenyan alkaline soda lake

Lipolytic enzyme production of 150 isolated strains from samples of Lake Bogoria (Kenya) was examined. Among these, fifteen isolates were selected on the basis of their lipolytic activities and subjected to morphological and 16S rRNA gene sequencing analyses for their identification. All the microorganisms have been selected under culture conditions with pH ranges between 7-10 and temperatures of 37-55 degrees C. Most of them showed optimal growth at 37 degrees C and tolerated salinity up to 10% (w/v). Ten of the isolates were Gram-negative, nine of which were closely related to the Pseudomonas cluster and one to the Halomonas cluster sharing high similarity profile with Halomonas desiderata. The remaining Gram-positive isolates were closely related to the Bacillus cluster, and were grouped with Bacillus halodurans, Bacillus alcalophilus and Bacillus licheniformis. Four members of the Bacillus cluster and the Halomonas sp. produced lipolytic activity under alkaline conditions, while others did so at neutral pH values.     

The denitrification capacity of sediment from a hypereutrophic lake

SUMMARY.

• 1 In sediment from Wintergreen Lake, Michigan, denitrification was not detectable by the acetylene inhibition method at in situ nitrate concentrations. When nitrate was added to sediment slurries, denitrification capacities up to 18.8μg N g^-1 h^-1 were measured. The denitrification capacities decreased with increasing sediment depth and distance from shore.
• 2 The high denitrification capacities in these sediments which under natural conditions had no supply of nitrate and oxygen suggested that denitrifies with alternative mechanisms for anaerobic energy conversion were present. Nitrous oxide was a significant portion of the N-gas produced immediately after the nitrate addition. Small amounts (4–5% of the total N-gas production) of nitric oxide accumulated in the early phase of nitrate reduction. Presumably after depletion of nitrate and nitrite both N₂O and NO were further reduced to N₂.
• 3 About 70%r of the added nitrate was denitrified, and the remainder was assumed to have been reduced to ammonium.

     

Molecular evidence for a uniform microbial community in sponges from different oceans

Sponges (class Porifera) are evolutionarily ancient metazoans that populate the tropical oceans in great abundances but also occur in temperate regions and even in freshwater. Sponges contain large numbers of bacteria that are embedded within the animal matrix. The phylogeny of these bacteria and the evolutionary age of the interaction are virtually unknown. In order to provide insights into the species richness of the microbial community of sponges, we performed a comprehensive diversity survey based on 190 sponge-derived 16S ribosomal DNA (rDNA) sequences. The sponges Aplysina aerophoba and Theonella swinhoei were chosen for construction of the bacterial 16S rDNA library because they are taxonomically distantly related and they populate nonoverlapping geographic regions. In both sponges, a uniform microbial community was discovered whose phylogenetic signature is distinctly different from that of marine plankton or marine sediments. Altogether 14 monophyletic, sponge-specific sequence clusters were identified that belong to at least seven different bacterial divisions. By definition, the sequences of each cluster are more closely related to each other than to a sequence from nonsponge sources. These monophyletic clusters comprise 70% of all publicly available sponge-derived 16S rDNA sequences, reflecting the generality of the observed phenomenon. This shared microbial fraction represents the smallest common denominator of the sponges investigated in this study. Bacteria that are exclusively found in certain host species or that occur only transiently would have been missed. A picture emerges where sponges can be viewed as highly concentrated reservoirs of so far uncultured and elusive marine microorganisms.     

Phytoplankton succession and diversity in a warm monomictic,relatively shallow lake: Lake Volvi,Macedonia, Greece

In Lake Volvi, phytoplankton dominance was examined in relation to the main phases of the fluctuating physical state of the water column and nutrient levels. Four stages of algal succession were identified. The successional pattern was, in general, similar from year to year. External disturbances such as increased wind mixing and high floods had the effect of setting the succession back to an earlier stage.Nanoplanktic diatoms and flagellates dominated during the first stages of succession. The succession was running from r-selected species in early stages to K-strategists in summer and towards a mixed community in the terminal stage.Diversity was expressed by the indices of Gleason and Shannon (based on physical units and biomass). Interpretation of species diversity took into account the differential variations of its two components, the number of species and the evenness of their distribution. Diversity was more affected by evenness than by number of species.Diversity increased in late stages of succession corresponding to the complexity of the community (high number of species, high evenness). Physical disturbances influenced positively the diversity. The maximal diversity appeared in the transition periods between the compositional changes generated by disturbances and the true successional development. Disturbances may generate a more uniform distribution of diversity throughout the whole water column.The role of physical disturbances in increasing the phytoplankton diversity may be demonstrated from comparisons of diversity — evenness — species number of the same stages under different meteorological conditions.     

Fatty acids of sponges from the Sea of Okhotsk

The fatty acid (FA) composition of Demospongiae species from the Sea of Okhotsk was studied. Fifteen sponge species were investigated for the first time, and the previously studied species Desmacella rosea and Myxilla incrustans were reexamined for their FA composition. Gas chromatography-mass spectrometry revealed 150 different fatty acids, of which 15 have not been identified in sponge lipids previously. The relative content of saturated FAs varied from 7.6 in Melonachora kobjakovae to 29.6% in Amphilectus digitata, with an average of 14.6% of total FAs. The relative content of monoenic FAs ranged from 12.8 in T. dirhaphis to 27.0% in Polymastia sp., with an average of 20.6% of total FAs. Non-methylen-interrupted, primarily unsaturated Δ5,9-FAs contributed a significantly to the amount of polyunsaturated fatty acids of sponges; this being a distinguishing feature of the FA composition of the investigated group of organisms.     

Characterization of a Chromobacterium haemolyticum population from a natural tropical lake

Aim: To study genetic diversity of Chromobacterium haemolyticum isolates recovered from a natural tropical lake. Methods and Results: A set of 31 isolates were recovered from a bacterial freshwater community by conventional plating methods and subjected to genetic and phenotypic characterization. The 16S ribosomal RNA (rRNA) gene phylogeny revealed that the isolates were related most closely with C. haemolyticum. In addition to the molecular data, our isolates exhibited strong β‐haemolytic activity, were nonviolacein producers and utilized i‐inositol, d ‐mannitol and d ‐sorbitol in contrast with the other known chromobacteria. Evaluation of the genetic diversity in the 16S rRNA gene, tRNA intergenic spacers (tDNA) and 16S‐23S internal transcribed spacers (ITS) unveiled different levels of genetic heterogeneity in the population, which were also observed with repetitive extragenic palindromic (rep)‐PCR genomic fingerprinting using the BOX‐AR1 primer. tDNA‐ and ITS‐PCR analyses were partially congruent with the 16S rRNA gene phylogeny. The isolates exhibited high resistance to β‐lactamic antibiotics. Conclusion: The population genetic heterogeneity was revealed by 16S rRNA gene sequence, ITS and BOX‐PCR analysis. Significance and Impact of the Study: This study provides for the first time an insight into the genetic diversity of phylogenetically close isolates to C. haemolyticum species.