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Single-cell visualization indicates direct role of sponge host in uptake of dissolved organic matter
Proceedings of the Royal Society B: Biological Sciences, 2019
Marine sponges are set to become more abundant in many near-future oligotrophic environments, where they play crucial roles in nutrient cycling. Of high importance is their mass turnover of dissolved organic matter (DOM), a heterogeneous mixture that constitutes the largest fraction of organic matter in the ocean and is recycled primarily by bacterial mediation. Little is known, however, about the mechanism that enables sponges to incorporate large quantities of DOM in their nutrition, unlike most other invertebrates. Here, we examine the cellular capacity for direct processing of DOM, and the fate of the processed matter, inside a dinoflagellate-hosting bioeroding sponge that is prominent on Indo-Pacific coral reefs. Integrating transmission electron microscopy with nanoscale secondary ion mass spectrometry, we track 15 N- and 13 C-enriched DOM over time at the individual cell level of an intact sponge holobiont. We show initial high enrichment in the filter-feeding cells of the sp...
Marine Ecology Progress Series
Sponge-microbe symbioses underpin the ecological success of sponges in many aquatic benthic ecosystems worldwide. These symbioses are often described as mutually beneficial, but identifying positive symbiotic interactions and quantifying the contribution of partners to physiological processes is challenging. For example, our understanding of the relative contribution of sponge cells and their microbial symbionts to the uptake and exchange of dissolved organic matter (DOM)—a major component of sponge diet—is limited. Here, we combined host-symbiont cell separation with pulse-chase isotopic labelling in order to trace the uptake of13C- and15Nenriched DOM into sponge cells and microbial symbionts of the encrusting Caribbean spongesHaliclona vansoestiandScopalina ruetzleri, which are low microbial abundance (LMA) species. Sponge cells were responsible for >99% of DOM assimilation during the pulse-chase experiment for both sponge species, while the contribution of symbiotic microbes t...
Scientific Reports
Deep-sea sponges create hotspots of biodiversity and biological activity in the otherwise barren deep-sea. However, it remains elusive how sponge hosts and their microbial symbionts acquire and process food in these food-limited environments. Therefore, we traced the processing (i.e. assimilation and respiration) of 13C- and 15N-enriched dissolved organic matter (DOM) and bacteria by three dominant North Atlantic deep-sea sponges: the high microbial abundance (HMA) demosponge Geodia barretti, the low microbial abundance (LMA) demosponge Hymedesmia paupertas, and the LMA hexactinellid Vazella pourtalesii. We also assessed the assimilation of both food sources into sponge- and bacteria-specific phospholipid-derived fatty acid (PLFA) biomarkers. All sponges were capable of assimilating DOM as well as bacteria. However, processing of the two food sources differed considerably between the tested species: the DOM assimilation-to-respiration efficiency was highest for the HMA sponge, yet u...
Limnology and Oceanography
Sponges are commonly divided into high (HMA) and low (LMA) microbial-abundance species according to the bacterial biomass in their tissue. These two groups reflect distinct aquiferous structures and feeding strategies. In the NW Mediterranean coralligenous community, HMA and LMA sponges are often packed in dense, multispecies assemblages that cover many pinnacles and overhangs. We investigated the metabolism of HMA and LMA species that cohabitate the coralligenous community by sampling in situ the inhaled and exhaled water. Sponges consumed plankton, dissolved organic carbon (DOC), and ammonium in relation to their abundance in ambient water. The plankton retention efficiency was high for all species. DOC was the main source of C for the sponge species, accounting for 90% of the examined sources. Nitrogen fluxes markedly differed between the two groups: plankton was the main source of nitrogen for LMAs that excreted dissolved organic nitrogen (DON) and ammonium. The nitrogenous waste products of LMAs were found to be the major source of nitrogen (up to 97%) for HMAs that efficiently removed DON and ammonium and excreted nitrate. The different capacity of both sponge strategies to use dissolved resources suggests a partial trophic niche separation related to HMA-LMA dichotomy as a mechanism facilitating their dense coexistence in the community. Our findings suggest that a mixed assemblage of sponges (and their associated microbes) is able to utilize the suspended particulate and dissolved material more efficiently than a single species population and may contribute to the understanding of the phenomena of the stability and diversity of dense sponge assemblages in oligotrophic habitats.
Single-cell measurement of ammonium and bicarbonate uptake within a photosymbiotic bioeroding sponge
The ISME journal, 2018
Some of the most aggressive coral-excavating sponges host intracellular dinoflagellates from the genus Symbiodinium, which are hypothesized to provide the sponges with autotrophic energy that powers bioerosion. Investigations of the contribution of Symbiodinium to host metabolism and particularly inorganic nutrient recycling are complicated, however, by the presence of alternative prokaryotic candidates for this role. Here, novel methods are used to study nutrient assimilation and transfer within and between the outer-layer cells of the Indopacific bioeroding sponge Cliona orientalis. Combining stable isotope labelling, transmission electron microscopy (TEM) and nanoscale secondary ion mass spectrometry (NanoSIMS), we visualize and measure metabolic activity at the individual cell level, tracking the fate of N-ammonium and C-bicarbonate within the intact holobiont. We found strong uptake of both inorganic sources (especially C-bicarbonate) by Symbiodinium cells. Labelled organic nut...
Limnology and Oceanography, 2003
The vast majority of organic matter in the world ocean is found in the dissolved pool. However, no evidence has been demonstrated for direct uptake of bulk dissolved organic matter (DOM) by organisms other than bacteria and some invertebrate larvae. The total organic carbon (TOC) is 10-30% higher in coral reefs than in adjacent open waters. The dissolved organic carbon (DOC) accounts for Ͼ90% of the TOC. Using a new in situ technique for clean sampling of the seawater inhaled and exhaled by benthic suspension feeders, we measured directly the removal of DOC in the symbiont-bearing reef sponge Theonella swinhoei. The sponge removed up to 26% (mean Ϯ SD: 12% Ϯ 8%) of the TOC (dissolved and particulate) from the water it filtered during a single passage through its filtration system. Most of the carbon gained by the sponge was from the dissolved pool (10 Ϯ 7 mol C L Ϫ1 ), an order of magnitude greater than the carbon gained from the total living cells (phytoplankton and bacteria) the sponge removed (2 Ϯ 1 mol C L Ϫ1 ). In T. swinhoei, over two-thirds of the sponge biomass consists of symbiotic bacteria, which likely play an important role in DOC uptake. Our findings indicate that the role of DOC in metazoan nutrition and the role of metazoans in DOC cycling may have been grossly underestimated.
The Life of a Sponge in a Sandy Lagoon
Biological Bulletin, 1995
Infaunal soft-bottom invertebrates benefit from the presence of sediment, but sedimentation is potentially harmful for hard-bottom dwellers. Most sponges live on hard bottom, but on coral reefs in the Red Sea, the species Biemna ehrenbergi (Keller, 1889) is found exclusively in soft-bottom lagoons, usually in the shallowest part. This location is a sink environment, which increases the deposition of particulate organic matter. Most of the sponge body is covered by sediment, but the chimneylike siphons protrude from the sediment surface. The sponge is attached to the buried beach-rock, which reduces the risk of dislodgment during storms. Dye injected above and into the sediment revealed, for the first time, a sponge pumping interstitial water (rich with particles and nutrients) into its aquiferous system. Visual examination of plastic replicas of the aquiferous system and electron microscopical analysis of sponge tissue revealed that the transcellular ostia are mostly located on the buried surface of the sponge. The oscula, however, are located on top of the siphons; their elevated position and their ability to close combine to prevent the filtering system outflow from clogging. The transcellular ostia presumably remain open due to cellular mobility. The sponge maintains a large population of bacteriocytes, which contains bacteria of several different species. Some of these bacteria disintegrate, and may be consumed by the sponge.
Particulate organic matter as a food source for a coral reef sponge
Journal of Experimental Biology, 2009
The ability of sponges to feed in diverse (including oligotrophic) ecosystems significantly contributes to their ubiquitous aquatic distribution. It was hypothesized that sponges that harbour small amounts of symbiotic bacteria in their mass feed mainly on particulate organic matter (POM). We examined the nearly symbiont-free (by microscopic observation) filter-feeding Red Sea sponge Negombata magnifica in order to: (a) study removal efficiency of naturally occurring organic particles, (b) measure the total amount of absorbed particulate organic carbon (POC) and nitrogen (PON), and (c) estimate organic carbon and nitrogen flux in this sponge. Total amount of organic carbon and nitrogen in the Gulf of Aqaba was found to be 48.46±5.69gl -1 and 6.45±0.7gl -1 , respectively. While detritus contributed 54% of POC, most PON (84%) came from planktonic microorganisms, mainly prokaryotes. Particle removal efficiency ranged from 99% (the cyanobacterium Synechococcus sp.) to 37% (for eukaryotic cells >8m). On average, N. magnifica ingested 480gCday -1 g -1 (wet mass, WM) sponge and 76.6gNday -1 g -1 sponge. Ingested POC balanced 85% of the spongeʼs energetic demand but more is needed for biomass production because it cannot digest all of the carbon. 54.4±16.1gNday -1 g -1 (WM) nitrogen was excreted as total ammonia nitrogen (TAN); however, nitrogen allowance should be higher because more nitrogen is deposited for sponge biomass during growth. It is hypothesized that the discrepancy in the nutritional requirements should be covered by the sponge absorbing carbon and nitrogen from sources that are not dealt with in the present research, such as dissolved organic carbon and nitrogen. This study highlights the significance of detritus as a carbon source, and prokaryotes as a PON source in sponge feeding.
Nutrient utilisation by shallow water temperate sponges in New Zealand
Hydrobiologia, 2012
Major nutrients such as phosphate, nitrate, ammonium and silicate, are involved in the metabolic processes of marine organisms. Sponges take up and produce inorganic nutrients and the extent at which they affect the budgets available for other organisms has received little attention. For this reason, we investigated nutrient fluxes for several sponge species in order to estimate whether sponges were net producers or consumers of nutrients from the water column, and how these patterns changed over time. Nutrient fluxes were examined on the south coast of Wellington, New Zealand. For the nutrient analysis (nitrate, nitrite, ammonium, phosphate and silicate), water samples were collected in situ from the inhalant and exhalant water of different sponge species. Samples were analysed both in a multi-species survey and over a two-year period for three other species to determine any temporal changes in fluxes. Our results yielded significant differences in nutrient concentrations between the inhalant and exhalant water for some of the species, but there was no clear pattern associated with the time of year. The levels of dissolved inorganic nutrients in the ambient water varied considerably over the 2-year study period. It is possible that a lack of a clear pattern of nutrient uptake/release of nutrients in some of the study species, and the fact that not all species showed significant uptake/release at different times of the year, may be related to high levels of temporal and spatial variation in the ambient nutrient availability, as well as other temporal fluctuations in parameters, such as water temperature, sponge size, and concentration of food in the water column. Finally, we believe that the activity of specific microbial communities associated with these sponges may be important in explaining the fluxes we have reported.
Sponge waste that fuels marine oligotrophic food webs: a re‐assessment of its origin and nature
Marine Ecology, 2015
It has recently been realized that sponges take up much of the dissolved organic matter (DOM) available in the water of reefs. The energy derived from this DOM is suggested to be invested in renewing the sponge filter cells (choanocytes) every few hours, generating an outflow of detrital particulate organic matter (POM) that is rapidly ingested by other invertebrates. By this DOM-to-POM recycling, sponges are proposed to fuel the food web of oligotrophic marine communities, including reefs, caves and deep-sea environments. In four species studied herein by electron microscopy, the POM found in the outgoing aquiferous canals had a complex composition, with large between-species differences. It may include choanocytes (0-52%), and also mesohyl cells, such as archeocytes (9-20%) and spherulous, and granular cells with inclusions (27-90%). Exocytosed vesicles also occurred. Surprisingly, to end up into the outgoing canals, the internal mesohyl cells are squeezed between the epithelial cells (endopinacocytes) of the canal wall. Mesohyl cells were also able to transfer their inclusions to the endopinacocytes, which in turn extruded their acquired vesicle loads into the canal lumen. The unanticipated abundant participation of mesohyl cells and endopinacocytes in the production of POM appears to be an ordinary process that occurs continuously in the sponges, mostly related to elimination of digestion leftovers and excretion by-products. Therefore, POM is generated by sponges irrespective of whether the primary food source is particulate (evidence from this study) or DOM (previous literature). Altogether, these results indicate that the cellular mechanisms behind the relevant organicmatter recycling carried out by sponges are more diverse than initially anticipated. The varying ratios of choanocytes/mesohyl cells in the POM across species suggest that different sponge species may impact differently the energetics of food webs of the respective oligotrophic habitats where they dominate.
Sponges (Porifera) and eukaryotic, unicellular plankton
Journal of Experimental Marine Biology and Ecology, 2009
Sponges (Porifera), in general, are pumping water through their bodies. This water contains planktonic eukaryotic and procaryotic organisms as well as particulate and dissolved organic matter as potential food source. We analyzed the eukaryotic unicellular plankton fraction from water surrounding sponges of the species Aplysina aerophoba, Nardo 1886, from sponge tissue, as well as from water expelled from those sponges. We found sponges without any remnants of plankton in their tissue, as well as specimens which incorporated high numbers of remnants of organisms after planktonic “blooms”. In laboratory experiments, sponges were not showing any uptake of plankton from their surrounding water. Sponges are generally considered as inner filter feeders. However, our results indicate that eukaryotic unicellular plankton organisms are not the main food resource of the common sponge A. aerophoba. This raises the question if filter feeding is actually the main characteristic of the poriferan lifestyle.
Re-plumbing in a Mediterranean sponge
Biology Letters, 2007
Observations are reported for Dysidea avara sponges where once functioning oscula (outlets) are converted through internal re-plumbing into functioning oversized ostia (OSO; inlets). Flow tank studies employed high-speed photography and particle tracking of laser-illuminated 0.5–6.0 μm diameter glass beads to trace particles streaming into OSO. A fluorescein dye/glass bead uptake experiment showed that an oversized ostium was connected through internal structures to the lone osculum. Beginning 30 s after uptake and continuing over a 20 min period, dye streamed from the osculum, but no beads emerged. Scanning electron microscopy revealed that beads were deposited only on the inhalant side of particle filtering choanocyte chambers and not on the exhalant side, suggesting that internal re-plumbing had occurred. Functioning OSO were also found on freshly collected specimens in the field, making it highly unlikely that formation of OSO was only an artefact of sponges being held in a labo...
Natural Diet of Coral-Excavating Sponges Consists Mainly of Dissolved Organic Carbon (DOC)
PLoS ONE, 2014
Coral-excavating sponges are the most important bioeroders on Caribbean reefs and increase in abundance throughout the region. This increase is commonly attributed to a concomitant increase in food availability due to eutrophication and pollution. We therefore investigated the uptake of organic matter by the two coral-excavating sponges Siphonodictyon sp. and Cliona delitrix and tested whether they are capable of consuming dissolved organic carbon (DOC) as part of their diet. A device for simultaneous sampling of water inhaled and exhaled by the sponges was used to directly measure the removal of DOC and bacteria in situ. During a single passage through their filtration system 14% and 13% respectively of the total organic carbon (TOC) in the inhaled water was removed by the sponges. 82% (Siphonodictyon sp.; mean6SD; 13617 mmol L 21 ) and 76% (C. delitrix; 10612 mmol L 21 ) of the carbon removed was taken up in form of DOC, whereas the remainder was taken up in the form of particulate organic carbon (POC; bacteria and phytoplankton) despite high bacteria retention efficiency (72615% and 87610%). Siphonodictyon sp. and C. delitrix removed DOC at a rate of 4616773 and 3546562 mmol C h 21 respectively. Bacteria removal was 1.860.9610 10 and 1.760.6610 10 cells h 21 , which equals a carbon uptake of 46.0621.2 and 42.5614.0 mmol C h 21 respectively. Therefore, DOC represents 83 and 81% of the TOC taken up by Siphonodictyon sp. and C. delitrix per hour. These findings suggest that similar to various reef sponges coral-excavating sponges also mainly rely on DOC to meet their carbon demand. We hypothesize that excavating sponges may also benefit from an increasing production of more labile algal-derived DOC (as compared to coral-derived DOC) on reefs as a result of the ongoing coral-algal phase shift.
Bacterial Uptake by the Marine Sponge Aplysina aerophoba
Microbial Ecology, 2007
Sponges (Porifera) are filter feeders that take up microorganisms from seawater and digest them by phagocytosis. At the same time, many sponges are known to harbor massive consortia of symbiotic microorganisms, which are phylogenetically distinct from those in seawater, within the mesohyl matrix. In the present study, feeding experiments were performed to investigate whether phylogenetically different bacterial isolates, hereafter termed Bfood bacteria,^microbial seawater consortia, and sponge symbiont consortia are taken up and processed differently by the host sponge. Aplysina aerophoba retained high numbers of bacterial isolates and microbial seawater consortia with rates of up to 2.76 Â 10 6 bacteria (g sponge wet weight)-1 h-1 , whereas the retention of sponge symbionts was lower by nearly two orders of magnitude [5.37 Â 10 4 bacteria (g sponge wet weight)-1 h-1 ]. In order to visualize the processing of a food bacterium within sponge tissues, the green fluorescent protein-labeled Vibrio strain MMW1, which had originally been isolated from A. aerophoba, was constructed. Incubation of this strain with A. aerophoba and subsequent visualization in tissue cryosections showed its presence in the choanocytes and/or endopinacocytes lining the canals but, unlike latex beads, not in deeper regions of the mesohyl, which suggests digestion of the bacteria upon contact with the host. Denaturing gradient gel electrophoresis (DGGE) was performed on the incubation seawater to monitor the changes in phylogenetic composition after incubation of the sponge with either seawater or sponge symbiont consortia. However, the DGGE experiment provided no evidence for selective processing of individual lineages by the host sponge. In conclusion, this study extends early studies by Wilkinson et al. (Proc R Soc London B 220:519-528, 1984) that sponges, here A. ae-rophoba, are able to differentiate between food bacteria and their own bacterial symbionts. Construction of a GFP-Labeled Vibrio Strain SB177 and Its Visualization in Host Tissues.
Limnology and Oceanography, 2010
The oxygen dynamics and pumping behavior in Dysidea avara and Chondrosia reniformis (Porifera, Demospongiae) were investigated using oxygen microelectrodes and heated thermistor flow sensors. Both field and laboratory experiments showed the common occurrence of low oxygenation approaching anoxia in both species, lasting up to 1 h. Strong temporal and spatial heterogeneity of oxygen concentrations were observed with replicate oxygen profile series across the sponge surface, though tissue close to an osculum was generally better oxygenated than deeper in the sponge body. Because of observed lag times between a pumping event and the respective oxygenation response, the state of oxygenation of sponge tissue could only be partially attributed to its pumping activity. Ambient flow also influenced oxygenation patterns of sponges. Larger individuals possessing a functional aquiferous system regulated their pumping activity according to the ambient flow regime, whereas a small D. avara sponge, yet to possess its first osculum, was passively oxygenated by ambient flow and became anoxic approximately 30 min after ambient flow was stopped in its laboratory tank. These studies showed (1) sponge tissue metabolism switched frequently from aerobic to anaerobic, (2) temporally and spatially dynamic oxygen-depleted regions were commonly found within those sponges, both in captivity and in the field, and (3) tissue oxygenation was regulated both by active behavior (pumping) and passive environmental events (ambient water flow). We concluded that the metabolism of both sponge cells and sponge microbes will be influenced by the sponges' ability to control oxygen concentrations in different regions of its body at any particular time. In addition, when a sponge is actively pumping in a particular region of its body, higher oxygen concentrations will favor aerobic symbionts and aerobic metabolism, whereas when active pumping ceases, anaerobic symbionts and anaerobic tissue metabolism will be favored.
Limnology and Oceanography, 2010
The oxygen dynamics and pumping behavior in Dysidea avara and Chondrosia reniformis (Porifera, Demospongiae) were investigated using oxygen microelectrodes and heated thermistor flow sensors. Both field and laboratory experiments showed the common occurrence of low oxygenation approaching anoxia in both species, lasting up to 1 h. Strong temporal and spatial heterogeneity of oxygen concentrations were observed with replicate oxygen profile series across the sponge surface, though tissue close to an osculum was generally better oxygenated than deeper in the sponge body. Because of observed lag times between a pumping event and the respective oxygenation response, the state of oxygenation of sponge tissue could only be partially attributed to its pumping activity. Ambient flow also influenced oxygenation patterns of sponges. Larger individuals possessing a functional aquiferous system regulated their pumping activity according to the ambient flow regime, whereas a small D. avara sponge, yet to possess its first osculum, was passively oxygenated by ambient flow and became anoxic approximately 30 min after ambient flow was stopped in its laboratory tank. These studies showed (1) sponge tissue metabolism switched frequently from aerobic to anaerobic, (2) temporally and spatially dynamic oxygen-depleted regions were commonly found within those sponges, both in captivity and in the field, and (3) tissue oxygenation was regulated both by active behavior (pumping) and passive environmental events (ambient water flow). We concluded that the metabolism of both sponge cells and sponge microbes will be influenced by the sponges' ability to control oxygen concentrations in different regions of its body at any particular time. In addition, when a sponge is actively pumping in a particular region of its body, higher oxygen concentrations will favor aerobic symbionts and aerobic metabolism, whereas when active pumping ceases, anaerobic symbionts and anaerobic tissue metabolism will be favored.
Marine Biotechnology, 2001
The rate of food particle uptake of the tropical sponge Pseudosuberites aff. andrewsi was studied in relation to particle concentrations and particle size. A range of different concentrations of either the marine microalga Dunaliella tertiolecta (∼5-8 µm) or the marine cyanobacterium Synechococcus sp. (∼1 µm) was supplied to the sponges. D. tertiolecta had a pronounced effect on the filtration activity of the sponges: at concentrations higher than approximately 4 × 10 5 cells/cm 3 , the filtration rates dropped dramatically. Such a clear effect was not found for Synechococcus sp. The results further showed that the maximal amount of food (when expressed in organic carbon) that can be taken up per cubic centimeter of sponge volume per unit of time should in principle be sufficient to enable growth (irrespective of the food particle type). At the maximal food particle concentration that did not affect the filtration rates, the uptake of organic carbon is already highly in excess of the amount of organic carbon that the sponges need to cope with their respiratory demand. Based on these findings, a series of growth experiments was carried out in which the sponges were subjected to a constant concentration of different types of food particles (Synechococcus sp. and the microalgae Chlorella sorokiniana and Nannochloropsis sp). Although initial growth was sometimes observed, continuous growth at a constant rate could not be obtained. It is concluded that qualitative aspects of feeding rather than quantitative aspects are the key to successful in vivo sponge culture.
Complex interactions between marine sponges and their symbiotic microbial communities
Limnology and Oceanography, 2011
To investigate the importance of symbiont-derived nutrition to host sponges, we coupled manipulative shading experiments with stable isotope analyses of isolated symbiont and host cell fractions. Experiments were conducted with four common reef sponges: Aplysina cauliformis, A. fulva, Neopetrosia subtriangularis, and Niphates erecta. The sponge N. erecta lacks photosymbionts, had a higher growth rate under shaded conditions, and displayed no difference in chlorophyll a (Chl a) concentrations across treatments. Isotope values suggested that this sponge obtains nutrition from particulate organic matter in the water column. In contrast, sponges hosting cyanobacterial symbionts (Aplysina spp. and Neopetrosia) had lower growth rates and lower Chl a concentrations under shaded conditions, suggesting that these hosts rely on photosymbiont nutrition. d 15 N and d 13 C values of sponge and microbial cell fractions demonstrated that, while both carbon and nitrogen are transferred from symbionts to host cells in A. cauliformis, only carbon is transferred in N. subtriangularis, and only nitrogen is transferred in A. fulva. Under shaded conditions, shifts in symbiont d 13 C values were coupled to shifts in host d 13 C values in some, but not all, host species, suggesting that the stability of these interactions varies across host species. Symbiont-derived nutrients are transferred to the cells of host sponges, and the variability observed among host species indicates that these interactions are more complex than originally hypothesized.