Boring Sponge Research Articles

Sibling species of mutualistic Symbiodinium clade G from bioeroding sponges in the western Pacific and western Atlantic oceans.

Dinoflagellates in the genus Symbiodinium associate with a broad array of metazoan and protistian hosts. Symbiodinium-based symbioses involving bioeroding sponge hosts have received less attention than those involving popular scleractinian hosts. Certain species of common Cliona harbor high densities of an ecologically restricted group of Symbiodinium, referred to as Clade G. Clade G Symbiodinium are also known to form stable and functionally important associations with Foraminifera and black corals (Antipatharia) Analyses of genetic evidence indicate that Clade G likely comprises several distinct species. Here, we use nucleotide sequence data in combination with ecological and geographic attributes to formally describe Symbiodinium endoclionum sp. nov. obtained from the Pacific boring sponge Cliona orientalis and Symbiodinium spongiolum sp. nov. from the congeneric western Atlantic sponge Cliona varians. These species appear to be part of an adaptive radiation comprising lineages of Clade G specialized to the metazoan phyla Porifera and Cnidaria, which began prior to the separation of the Pacific and Atlantic Oceans.

Endo‐ and epilithic faunal succession in a Pliocene–Pleistocene cave on Rhodes, Greece: record of a transgression

AbstractA fossil cave and associated sediments and fossil fauna located on the Greek island of Rhodes in the eastern Aegean Sea is reported here, and the depositional history discussed. The sediments were deposited during the late Pliocene, in the interstitial space between basement boulders of up to 1500 tons. The depositional history of the cave comprises eight stages. From initial flooding, the basin experienced a continuous transgression with sea‐level rise in excess of 500 m, followed by a rapid, forced regression of similar magnitude. The recognition of a succession of fossil communities illustrates this transgression, with a seemingly abrupt shift from endolithic to epilithic biota dominance late in the transgressive cycle. The communities recording the increasing water depth from 0 to >150 m are: The Gatrochaenolithes torpedo (bivalve boring) and Entobia gonioides (sponge boring) ichnocoenosis, with peak distribution between 0 and 1 m water depth; the E. gonioides – E. magna ichnocoenosis, with 1–5 m depth peak distribution; the exclusive E. magna ichnocoenosis, with 5–40 m depth peak distribution; and the E. gigantea ichnocoenosis, with a peak distribution approaching 150–200 m. Below this depth, an epilithic community without boring organisms takes over, characterized by the calcareous sponge Merlia cf. normani, and the inarticulate brachiopod Novocrania turbinata. Simultaneously with the succession of the endo‐ and epilithic cave wall fossil communities, skeletal calcarenite accumulated on the cave floor; the erosional remnants of this sediment are insufficient to further expand the overall transgression–regression model.

The dynamics of a Mediterranean coralligenous sponge assemblage at decennial and millennial temporal scales.

This paper concerns the changes occurred over both decennial and millennial spans of time in a sponge assemblage present in coralligenous biogenic build-ups growing at 15 m depth in the Ligurian Sea (Western Mediterranean). The comparison of the sponge diversity after a time interval of about 40 years (1973–2014) showed a significant reduction in species richness (about 45%). This decrease affected mainly the massive/erect sponges, and in particular the subclass Keratosa, with a species loss of 67%, while the encrusting and cavity dwelling sponges lost the 36% and 50%, respectively. The boring sponges lost only one species (25%). This changing pattern suggested that the inner habitat of the bioconstructions was less affected by the variations of the environmental conditions or by the human pressures which, on the contrary, strongly affected the species living on the surface of the biogenic build-ups. Five cores extracted from the bioherms, dating back to 3500 YBP, allowed to analyse the siliceous spicules remained trapped in them in order to obtain taxonomic information. Changes at generic level in diversity and abundance were observed at 500/250-years intervals, ranging between 19 and 33 genera. The number of genera showed a sharp decrease since 3500–3000 to 3000–2500 YBP. After this period, the genera regularly increased until 1500–1250 YBP, from when they progressively decreased until 1000–500 YBP. Tentatively, these changes could be related to the different climatic periods that followed one another in the Mediterranean area within the considered time span. The recent depletion in sponge richness recorded in the Ligurian coralligenous can be considered relevant. In fact, the analysis of the spicules indicated that the sponges living in these coralligenous habitats remained enough stable during 3000 years, but could have lost a significant part of their biodiversity in the last decades, coinciding with a series of warming episodes.

Natural Casts of Early Eocene Entobia from the Kachchh Basin, India

ABSTRACTExcellently preserved natural casts of sponge borings Entobia Bronn from the Early Eocene rocks of the Kachchh basin, India are reported for the first time. The entobian bioerosion is represented by four ichnospecies viz., Entobia cateniformis, E. geometrica, E. ovula, and E. paradoxa. Molds and casts of bivalves belonging to family Carditidae served as substrate for these sponge borings. The relation between mode of preservation of the natural casts, sea water chemistry, and time of emplacement of borings is discussed. The bored bioclasts are associated with Schaubcylindrichnus, Thalassinoides, and Rhizocorallium. This study indicates that the sediments of Assilina Limestone Member were deposited in turbidity-free, shallow water with nil or low rates of sedimentation.

Assessment of the effectiveness of natural coral fragmentation as a dispersal mechanism for coral reef‐boring sponges

AbstractEastern Pacific reefs are mostly made up of interlocking coral branches of Pocillopora, which are easily broken by physical forces associated with heavy swells and winds. In this study we investigated the potential of these coral fragments to enable propagation of boring sponges. For this, we quantified the frequency of occurrence and diversity of boring sponges in fragments of corals recently trapped among the branches of live colonies, and later tested the hypothesis that these sponges colonize new branches of corals. Nearly 80% of the coral colonies investigated had coral fragments among their branches, and 69% of these coral fragments contained boring sponges (11 species), some of these sponges in reproduction (23% of them carried oocytes). To test whether sponges inhabiting coral fragments could colonize new branching corals we transplanted them to healthy branches, and to branches whose living tissue was mechanically eliminated to simulate damage produced by grazing and death after bleaching and other causes of coral tissue mortality. All the transplanted coral fragments cemented to each new colony by means of calcification, and of the three sponge species tested (Cliona vermifera, Cliona tropicalis and Thoosa mismalolli) only C. vermifera was able to colonize both new living branches (26.9%) and cleaned branches (65.5%). The apparent capability of C. vermifera to colonize by direct contact may be another key ability of this species to maintain high frequency of occurrence in Pacific coral reefs. However, although C. tropicalis and T. mismalolli were not able to colonize new coral substrata by direct contact, coral fragments have the potential to contribute to local persistence of these sponges and to their dispersal, both by asexual (fragments) and sexual means (transport of sexual products). The present findings may partly explain the current increase of excavating sponges on deteriorating reefs with a large availability of dead branching corals.

Are oysters being bored to death? Influence of Cliona celata on Crassostrea virginica condition, growth and survival.

The boring sponge Cliona celata is a nuisance species that can have deleterious effects on eastern oyster Crassostrea virginica growth, condition, and survival. Surprisingly, however, these effects have not been well documented and when examined, results have been equi-vocal. In this study, we provide a direct comparison of growth, condition, and survival of sponge-colonized and uncolonized oysters in southeast North Carolina in 2 separate experiments. In the first experiment, sponge-colonized oysters exhibited significantly slower growth rates, reduced condition, and lower survival relative to uncolonized oysters, although results may have been confounded by oyster source. In the second experiment, using smaller oysters from the same source population, growth rate was again significantly reduced in colonized oysters relative to uncolonized oysters, however neither condition nor survival differed. In field surveys of the same population, colonized individuals across a range of sizes demonstrated significantly reduced condition. Further, condition index was negatively correlated with sponge biomass, which was positively correlated with oyster size, suggesting that the impact of the sponge changes with ontogeny. By investigating clearance rates, tissue isotopic and nutrient content, as well as caloric value, this study provides further evidence that sponge presence causes the oysters to divert energy into costly shell maintenance and repair at the expense of shell and somatic growth. Thus, although variable, our results demonstrate negative impacts of sponge infestation on oyster demographics, particularly as oysters grow larger.

Histological and Ultra Structural Changes in the Mantle of Perna indica (Brown Mussel, Kuriakose and Nair, 1976) Infested by Bioeroding Sponges

The effect of boring sponge infestation on histology and ultra structure of mantle tissue in Perna indica was studied. Transmission Electron Microscopy (TEM) of the mantle tissue infested by boring sponges indicates that they cause irreparable damage to the cell organelles. The variations in the anatomy of the various cell organelles are discussed. Increased cellular autophagy, haemocytosis, hypertrophy of nucleus and endoplasmic reticulum, vesicle formation in nucleolus and whorl formation of mitochondria are noted in sponge infested specimens. The most consistent change was dystrophy of mantle in ultra thin sections. Sponge infested tissues also exhibited histopathological changes like degeneration of the mantle and infiltration of haemocytes.

Sponge erosion under acidification and warming scenarios: differential impacts on living and dead coral.

Ocean acidification will disproportionately impact the growth of calcifying organisms in coral reef ecosystems. Simultaneously, sponge bioerosion rates have been shown to increase as seawater pH decreases. We conducted a 20-week experiment that included a 4-week acclimation period with a high number of replicate tanks and a fully orthogonal design with two levels of temperature (ambient and +1°C), three levels of pH (8.1, 7.8, and 7.6), and two levels of boring sponge (Cliona varians, present and absent) to account for differences in sponge attachment and carbonate change for both living and dead coral substrate (Porites furcata). Net coral calcification, net dissolution/bioerosion, coral and sponge survival, sponge attachment, and sponge symbiont health were evaluated. Additionally, we used the empirical data from the experiment to develop a stochastic simulation of carbonate change for small coral clusters (i.e., simulated reefs). Our findings suggest differential impacts of temperature, pH and sponge presence for living and dead corals. Net coral calcification (mgCaCO3 cm(-2) day(-1) ) was significantly reduced in treatments with increased temperature (+1°C) and when sponges were present; acidification had no significant effect on coral calcification. Net dissolution of dead coral was primarily driven by pH, regardless of sponge presence or seawater temperature. A reevaluation of the current paradigm of coral carbonate change under future acidification and warming scenarios should include ecologically relevant timescales, species interactions, and community organization to more accurately predict ecosystem-level response to future conditions.

Marine bioerosion of lapideous archaeological artifacts found in the Grotta Azzurra (Capri, Naples, Italy): Role of microbiota and boring Porifera

This research has been conducted on archaeological artifacts collected from the Grotta Azzurra (Capri, Naples, Italy). Endolithic microbiota and boring Porifera responsible for bioerosion and micro-erosion were analysed. SEM observations permitted the analysis of biodegradation. Embedding casting procedure with polyester resins allowed the identification of three different microborer traces, corresponding to green algae, fungi and boring sponges. According to spicule complement two excavating species and other four sponge species were recorded inside the bored cavities. In addition, the species Cliona janitrix is here reported, for the first time, into archaeological artifacts. Traces of the green alga Ostreobium quekettii (ichnospecies Ichnoreticulina elegans) were found to dominate in all samples; traces of three species of microfungi were abundant. Microscopic pitting patterns and resin casts produced by different boring sponges into marble samples have been examined. Different kinds of micro-erosion are characterized by various types of ornamentation and sculpturing patterns. The data confirm that endolithic chlorophytes and fungi together with macroboring organisms, especially boring sponges, play a significant role in biodeterioration processes of submerged lapideous artifacts.

Bioerosional ichnotaxa and the fossilization barrier

For the establishment of a new ichnogenus or ichnospecies, the type material shall be fossil, not unfossilized material. This is not always possible, because the transition between the two states, the fossilization barrier, is extremely vague defined. In most fossil material, this is not a problem. However, in the case of bioerosion structures (borings, rasping traces, attachment scars in hard substrates), the problem is serious. For example, when does a sponge boring in an oyster shell become fossilized? The question arises when Recent and sub-Recent materials are considered. Two examples are discussed. (1) Microborings are described and named in foraminifera dredged from the sea floor. In this material, it is not possible to distinguish between “fossilized” and “unfossilized” foraminifera. Bioturbation and other processes may have mixed recently dead, Pleistocene and older foraminifera in the sea-floor sediments. (2) Small, characteristic borings are made by slipper limpets in pagurized gastropod shells. The structures would constitute a new ichnospecies of Oichnus , but these borings have not been found in “fossilized material” and the borings therefore remain nameless. Because bioerosion structures constitute “ready-made fossils”, it is suggested that the onset of fossilization be equated with the death of the bioeroding tracemaker.

Borings and etchings in the Upper Bathonian-Lower Callovian oolite of the Paris Basin (France)

The oolite of the Dalle Nacree Formation in the Paris Basin is made of marine calcareous ooids with, from base to top, radial (and therefore likely to have been calcite), concentric and micritic fabrics, each corresponding to a discrete stratigraphic unit. Several hardgrounds and oolitic pebble-cobble layers in the succession are encrusted and bored. Three main types of boring have been identified ranging in sizes from some tens of µm (sponge borings) to centimeters (bivalve borings), with an intermediate category (worm borings). Some worm borings have rough walls, where early marine fibrous cement is less corroded than the cortices of cemented ooids. The key to understanding this differential dissolution could be related to organic matter, present within the ooid cortices but lacking in the fibrous cement. Polychaete worms that use chemical means (enzymes or acids) to bore are probably responsible for these peculiar borings. A secondary conclusion is that partly or fully leached ooid cortices do not necessarily indicate an original aragonitic mineralogy of the dissolved parts.

Effects of Substrate Type on Demographic Rates of Eastern Oyster (Crassostrea virginica)

ABSTRACT Several restored oyster (Crassostrea virginica Gmelin) reefs in Pamlico Sound, North Carolina, have experienced recent population crashes, potentially caused in part by clionid boring sponge infestation of the marl rock (a calcium carbonatemud composite material) commonly used as a reef substrate and of the shells of oysters that colonize the marl reef foundation. The composition and porosity of marl may make it vulnerable to infestation by carbonate bioeroders, particularly clionid sponges. The objective of this study was to quantify the effects of carbonate (CaCO3; oyster shell, marl) versus noncarbonate (non-CaCO3; granite, concrete) reef-building substrates on C. virginica demographic rates, including oyster density and oyster growth, on experimental reefs constructed along the salinity gradients of two estuaries in coastal North Carolina. There were no differences in oyster density among substrate types through the first 6 mo of reef sampling, although at 12 mo after reef construction, diffe...

Commensal borings from the Middle Devonian of central New York: ecologic and taxonomic review ofClionoides, Clionolithes, andCanaliparvan. ichnogen

The examination of 730 borings within 88 brachiopod hosts form the Middle Devonian of central New York State revealed four ichnospecies belonging to three ichnogenera that have taxonomic histories riddled with confusion, controversy and contradiction. New observations of the ichnotaxa question long-held views of a simple morphologic differentiation between sponge borings and worm borings.ClionoidesFenton and Fenton, 1932 is here considered a sponge boring, which is comprised of a complex, multi-dimensional system of tunnels, shafts, canals, microterraced bowl-shaped structures and cone extensions, and is a senior synonym ofPaleosabella(McCoy 1855) andVermiforichnusCameron, 1969a.ClionolithesClarke, 1908 is a sponge boring possessing a rosette, branching network extending from a central node and is a senior synonym ofNododendrinaVogel et al., 1987 andRamodendrinaVogel et al., 1987. The creation ofCanaliparva circularisn. ichnogen. n. ichnosp. is needed to accommodate simple, vertically oriented, U-shaped tunnels that are indicative of worm activity. Paleoecologic evidence supports a commensal relationship between the endoliths and hosts based upon boring site frequencies in the hosts, boring patterns and five inter-specific co-occurrences between traces. These new data suggest greater diversity and ecologic complexity in ichnofaunal paleocommunities from the Middle Devonian than previously recognized.

Habitat characteristics and environmental factors related to boring sponge assemblages on coral reefs near populated coastal areas on the Mexican Eastern Pacific coast

Coral reefs are undergoing global decline due to the environmental degradation of coastal areas through increasing human impacts from urban coastal development. Increases in the abundance of boring organisms are suggested to be a direct consequence of coral mortality and the exposure of calcareous substrates associated with deteriorated reef environments. The Mexican Pacific coast harbors coral reefs undergoing rapid degradation. In this study, we analyzed species richness and abundance of boring sponges associated with living corals, dead coral framework, and coral rubble from five coral reefs near the tourist destination of Zihuatanejo Bay, Guerrero. Environmental and habitat parameters indicative of human impacts on coral reefs were also recorded and analyzed. All coral reefs exhibited similar species richness (10–12 species), but sponge abundance (25–60 %) varied among the study sites. While dead coral framework and coral rubble were the preferred substrate types for boring sponges, the sites with the highest coverage of dead corals did not show the highest abundance of boring sponges. In fact, the reefs closest to the tourist site, which were weakly or moderately conserved, exhibited the highest levels of sponge abundance. These reefs also had the highest levels of δ15N (up to 9.5 ‰) and δ13C (−13.3 ‰) and high concentrations of chlorophyll a (1.8 mg m−3), which are indicative of wastewater impacts. In contrast, sites more distant from the tourist area, which were moderately or highly conserved, had less well-developed sponge assemblages. The analysis of environmental indicators showed comparatively high environmental quality for these sites, with water clarity values up to 7.5 m and chlorophyll a concentrations as low as 0.27 mg m−3. Differences in species composition were also evident among coral reef sites, with species such as Pione carpenteri, Thoosa calpulli, Siphonodictyon crypticum, Cliona mucronata and C. tropicalis dominating the more highly impacted sites. These results indicate that anthropogenic sources of nutrients may have a greater positive influence on the abundance of boring sponges on coral reefs near human populated sites.

Environmental factors shaping boring sponge assemblages at Mexican Pacific coral reefs

AbstractRecent studies suggest a future increase in sponge bioerosion as an outcome of coral reef decline around the world. However, the factors that shape boring sponge assemblages in coral reefs are not currently well understood. This work presents the results of a 17‐month assessment of the presence and species richness of boring sponges in fragments collected from living corals, dead coral reef matrix and coral rubble from Punta de Mita and Isabel Island, two coral reefs from the central coast of the Mexican Pacific Ocean. Both localities have a high cover of dead corals generated by past El Niño Southern Oscillation events, but Punta de Mita was also highly exposed to anthropogenic impacts. Additionally, environmental factors (water transparency, water movement, temperature, sediment deposition, SST, and chlorophyll concentration) were assessed to test the hypothesis that environmental conditions which are potentially harmful for corals can enhance sponge bioerosion. Isabel Island and Punta de Mita showed a similar species richness (13 and 11 species, respectively) but boring sponge presence in both live and dead corals was higher at Isabel Island (57.6%) than at Punta de Mita (35.7%). The same result was obtained when each type of substrate was analysed separately: dead coral reef matrix (81.3% versus 55.5%), coral rubble (47.7% versus 20.0%) and living corals (43.7% versus 31.7%). A principal components analysis showed a higher environmental heterogeneity at Punta de Mita, as well as important environmental differences between Punta de Mita and Isabel Island, due to sediment deposition (2.0 versus 0.2 kg·m−2·d−1) and water movement (24.5% versus 20.5% plaster dissolution day−1), that were also negatively correlated with boring sponge presence (r = −0.7). By analysing the boring sponge assemblage, we found that environmental settings, together with habitat availability (i.e., dead coral substrate) differentiated assemblage structure at both localities. Major structural differences were largely due to species such as Cliona vermifera, Cliona tropicalis and Aka cryptica. In conclusion, factors such as habitat availability favored the presence of boring sponges but some environmental factors such as abrasion resulting from moving sediment acted restrictively, and exerted a major role in structuring boring sponge assemblages in the Mexican Pacific.

Effects of seawater temperature and pH on the boring rates of the sponge Cliona celata in scallop shells

Warmer, more acidic water resulting from greenhouse gas emissions could influence ecosystem processes like bioerosion of calcifying organisms. Based on summer-maxima values (temperature = 26 °C; pH = 8.1) at a collection site in New York (40°56″ N, 72°30″ W), explants of the boring sponge Cliona celata Grant, 1826 were grown for 133 days on scallop shells in seawater ranging from current values to one scenario predicted for the year 2100 (T = 31 °C; pH = 7.8). High water temperature had little effect on sponge growth, survival, or boring rates. Lower pH slightly reduced sponge survival, while greatly influencing shell boring. At pH = 7.8, sponges bored twice the number of papillar holes and removed two times more shell weight than at pH = 8.1. Greater erosion resulted in weaker scallop shells. This study suggests that lower seawater pH may increase boring rates of C. celata in shellfish, with potentially severe implications for wild and farmed shellfish populations.

Bioerosive structures from Miocene marine mobile‐substrate communities in southern Spain, and description of a new sponge boring

Abstract: Neogene palaeoshore sediments are abundantly represented along the Mediterranean coast of Iberia. An outcrop north of the Sierra Tejeda, named La Resinera, exposes concentrations of pebbles and boulders of marble, comprising an upper Miocene marine beach deposit. The high diversity of bioerosion trace fossils present in these boulders includes structures produced by polychaete annelids, demosponges, echinoids and endolithic bivalves, which indicate a shallow shoreface environment. The ichnotaxa represented are Maeandropolydora sulcans, Caulostrepsis taeniola, Entobia geometrica, Entobia ovula, Circolites kotoncensis, Gastrochaenolites torpedo, Gastrochaenolites lapidicus, Gastrochaenolites ornatus and Gastrochaenolites turbinatus. The borings are Tortonian (late Miocene) in age. Also present, and particularly abundant, are large sponge borings that have a single chamber from which radiating canals emerge. This trace fossil is designated as Entobia resinensis isp. nov.

Spatial–temporal variability of epibenthic assemblages on subtidal biogenic reefs in the northern Adriatic Sea

Spatial distribution and temporal variation of epibenthic assemblages of coralligenous biogenic rocky outcrops occurring in the northern Adriatic Sea (45°04′–45°24′N; 12°23′–12°43′E) were investigated by photographic sampling from 2003 to 2006 at 12 randomly selected sites. The dominant reef-forming organisms were the encrusting calcareous algae (Lithophyllum stictaeforme, Lithothamnion minervae and Peyssonnelia polymorpha), while the main bioeroders were boring sponges (Cliona viridis, C. celata, C. thoosina, C. rhodensis, Piona vastifica) and the bivalve Gastrochaena dubia. Composition of the assemblages varied thorough years and among sites. Spatial heterogeneity, at local and regional scale, prevailed over temporal variation. This variability was related both to the geo-morphological features of the outcrops and to environmental variables. Sites clearly differed in the percent cover of reef builder and bioeroder species while only limited temporal variation within site was found. Some taxa revealed complex intra-site temporal trends. These results provide valuable information on the diversity and variability of epibenthic assemblages of the northern Adriatic coralligenous reefs, essential for the management and conservation of these unique biogenic habitats.

Infestation of the invasive mollusc Crepidula fornicata by the native shell borer Cliona celata: a case of high parasite load without detrimental effects

The temporal prevalence of the widespread boring sponge Cliona celata and its effects were analysed in a population of the invasive mollusc Crepidula fornicata. This mollusc produces extra shell material when infested with the endolithic sponge, suggesting that infestation may be detrimental for C. fornicata growth and/or reproduction. For 37 months, size, sex, female reproductive status and sponge-infestation stage were recorded for 300 individuals sampled every month in the Bay of Morlaix (France). In the 12,049 individuals examined, the prevalence of C. celata was high with a monthly average of 43.1% of the individuals hosting the sponge. The relative proportion of heavily infested individuals generally increased over time. Nevertheless, a cyclic decrease occurred every 10 months, suggesting putative episodes of mortality of heavily infested individuals. The gregarious behaviour of the mollusc seemed to promote the high prevalence of the sponge, which may propagate through contact between neighbouring C. fornicata individuals. Due to the sex-size relationship in protandrous C. fornicata, females were far more infested than males. We did not find evidence for a cost of producing extra shell material on somatic growth or on female fertility, and the boring sponge is unlikely to substantially affect the sex-change patterns in C. fornicata. The limited effects of the endolithic sponge on C. fornicata contrasts with the documented damage to some local species, including commercially exploited shellfish, suggesting that C. fornicata may alter the infestation dynamics in the surrounding native community. Dedicated studies are now needed to investigate the extent and mechanisms of these species interactions.

Infection of Cultured Eastern OystersCrassostrea virginicaby the Boring SpongeCliona celata, with Emphasis on Sponge Life History and Mitigation Strategies

ABSTRACT The boring sponge Cliona celata poses an ongoing threat to the quality of eastern oysters Crassostrea virginica cultured in Baie St-Simon, Shippagan, New Brunswick, Canada. Although grown primarily off-bottom, 25–30% of cultured oysters develop severe sponge infections, leading to the culling of otherwise marketable individuals. The main objectives of the current study were to identify the areas with the highest prevalence of infected oysters, determine the primary mode of sponge infection, document the rate of shell bioerosion, and develop an effective treatment for eliminating the sponge without harming the oysters. A bottom survey of wild oysters throughout the bay indicated a high prevalence of sponge infection in certain areas, possibly related to seasonal salinity patterns. No evidence of sponge infection via shell-to-shell contact, or proximity to wild oysters, was detected during the winter months when oyster shells were deployed in bags lying on the bottom. Histological sectioning of spo...