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1.
Abstract. The importance of sponge spicules in the turnover of biogenic silica (BSi) in the detritic bottoms of the Eastern Ligurian Riviera was evaluated by studying sediment cores and the detrital matter collected by a trap over a one year period.
This study made evident that: i) Sponge spicules represent the main component of the BSi both in the sediments and in the trapped matter; ii) A correlation exists between the sponge biomass present on the overhanging cliff and the amount of sponge spicules found in the sediment below; iii) Inside the sediments, a superficial layer (10 cm deep) characterized by intensive silica dissolution processes can be observed; and iv) The amount of spicules collected using the trap is not constant throughout the year, but shows a characteristic trend with low values in spring and summer and high values in autumn and winter.  相似文献   

2.
Abstract. The abundance, distribution, and species richness of the littoral sponges (0–55 m) from the Cabrera Archipelago (Balearic Islands) were studied along light gradients from the surface to the sea bottom and from cave mouths to their inner parts. A total of 98 species (11 Calcarea and 87 Demospongiae ) were recorded, 8 of which are new records for the Spanish coast.
Cluster and correspondence analyses enabled the identification of a sciophilous sponge group including three subgroups: sponges found only in semi-dark cave habitats, a subgroup common to the coralligenous, precoralligenous, and semi-dark cave biocoenoses, and a third subgroup exclusive to the coralligenous biocoenosis. A small number of photophilic species and other species having a wide bathymetric distribution made up another separate group. No species clusters for the different semi-sciophilous (either fleshy or carbonate) or photophilic seaweed communities were discernible. The number of sponge species was negatively correlated with the irradiance level.  相似文献   

3.
Biogenic silica (BSi) in marine sediments is an important indicator of siliceous organism distributions and paleoproductivities. Organisms that have BSi skeletons include diatoms, silicoflagellates, radiolarians and sponges. This study presents, for the first time, the distribution of biogenic siliceous fragments in shallow water sediments around Taiwan and the Sunda Shelf, which belong to this rarely studied region of the South China Sea (SCS). Thirty-one surface sediment samples were collected from intertidal to depths of 1,100?m. Only sponge spicules were found in this study and the abundance varied in the range of 3?C7,910?n?g?1 sediment. Combining previous studies with ours, from shallow to deep, it was observed that BSi composition in the surface sediment of this area changed from sponge spicules in the Sunda Shelf, followed by sponge spicules and radiolarians in the southwestern SCS, to sponge spicules, radiolarians and diatoms in the southern SCS. Based on this study, the abundance of sponge spicules correlated positively and negatively with water depth and sediment grain size when coral reef sites were excluded. The low spicule abundance in shallow waters may have resulted from local current conditions and the dilution effect through riverine input of terrestrial sediment. Other possible explanations for the varying spicule abundance among sites are the difference in local fauna, such as coral reefs which usually have high diversity and abundance of sponges. The findings provide additional information on the process of recent BSi deposition which may help future studies in sedimentology, paleogeography and paleoenvironments.  相似文献   

4.
The nematofauna associated with a cold-water coral degradation zone in the Porcupine Seabight (NE Atlantic) was investigated. This is the first comprehensive study of nematodes associated with cold-water corals. This research mainly aimed to investigate the influence of microhabitat type on nematode community structure. Three distinct microhabitats for nematodes were distinguished: dead coral fragments, glass sponge skeletons and the underlying sediment. The nematode assemblages associated with these three microhabitats were significantly different from each other. Coral and sponge substrata lie relatively unprotected on the seafloor and are consequently more subjected to strong currents than the underlying sediment. As a result, both large biogenic substrata were characterized by higher abundances of taxa that are less vulnerable and more adapted to physical disturbance, whereas the underlying sediment yielded more slender, sediment-dwelling taxa. Typically epifaunal taxa, such as Epsilonematidae and Draconematidae, were especially abundant on dead coral fragments, where they are thought to feed on the microbial biofilm which covers the coral surface. Several epifaunal genera showed significant preferences for this microhabitat, and Epsilonema (Epsilonematidae) was dominant here. Sponge skeletons are thought to act as efficient sediment traps, resulting in a lower abundance of epifaunal taxa compared to coral fragments. The underlying sediment was dominated by taxa typical for slope sediments. The considerable degree of overlap between the communities of each microhabitat is attributed to sediment infill between the coral branches and sponge spicules. It is assumed that the nematofauna associated with large biogenic substrata is composed of a typical sediment-dwelling background community, supplemented with taxa adapted to an epifaunal life strategy. The extent to which these taxa contribute to the community depends on the type of the substratum. Selective deposit feeders were dominant on sponge skeletons and in the underlying sediment, whereas coral fragments were dominated by epistratum feeders. The presence of a microbial biofilm on the coral fragments is proposed as an explanation for the significant preference of epistratum feeders for this microhabitat. Densities in the underlying sediment were low in comparison with other studies, but biodiversity was higher here than on the coral and sponge fragments, a difference which is attributed to lower disturbance. Nevertheless, the large biogenic substrata provide a microhabitat for rare, epifaunal taxa, and fragments of both substrata within the sediment increase habitat complexity and hence biodiversity.  相似文献   

5.
Recent 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.  相似文献   

6.
Spongivory by Parrotfish in Florida Mangrove and Reef Habitats   总被引：7，自引：0，他引：7  
Abstract. Although parrotfish are generally reported to be herbivorous, increasing evidence suggests that some Caribbean species feed on sponges. After observing grazing scars on the barrel sponge, Xestospongia muta , 40 sponges were videotaped on three reefs for >0.5 h to determine the frequency of parrotfish bites on this species. A total of 10 h of video recording captured 45 bites on normally coloured X. muta and 527 bites on four bleached X. muta by the parrotfish Sparisoma aurofrenarum, Scarus croicensis and Scarus taeniopterus. The viscera gut and liver of 55 parrotfish collected from mangrove and reef habitats were digested in nitric acid and analysed for spicule content. The parrotfish collected in the mangroves mostly Scarus guacamaia and Sparisoma chrysopterum had significantly higher masses of spicules in their viscera than did parrotfish collected on the reef Sparisoma aurofrenatum, Sparisoma viride, Sparisoma chrysopterum, Scarus vetula, Scarus coelestinus and Scarus taeniopterus . The spicules of Geodia gibhrrosa, a chemically undefended sponge that is common in the mangroves but rare in exposed locations on the reef, were abundant in the viscera of parrotfish collected in the mangroves. These results provide further evidence that fish predation has an important effect on the distribution and abundance of Caribbean sponges.  相似文献   

7.
The present work investigated the modifications induced by the spread of the green macroalga Caulerpa racemosa var. cylindracea (Bryopsidales, Chlorophyta) on the sponge assemblage of Apulian coralligenous concretions (Ionian Sea – Torre Ovo, Italy). The study of qualitative and quantitative sponge composition was carried out before (2004) and after (2006) the spread of this invasive alga by means of traditional (quadrat scraping) and photographic sampling methods. Results indicate that the spread of the green alga is concomitant with a significant decrease in percentage sponge cover both on horizontal- and on vertical-oriented substrates. In addition, strong modifications to the structure of the community in terms of repartition of the available substrate have been observed since the algal spread. Conversely, no major changes have affected the specific composition of the sponge assemblage, suggesting that at this stage of colonization the algal spread has not produced a loss of sponge biodiversity. However, there is a clear need to monitor closely the C. racemosa invasion to verify its long-term impact on the sponge assemblage.  相似文献   

8.
In a core from the outer Skagerrak, the content of biogenic opal is higher in Late Pleistocene (Younger Dryas) than in Holocene deposits. In terms of opal accumulation, rates are 1 g/cm2/1,000 y during the Holocene and five to ten times larger during the Younger Dryas. Intensive dissolution has greatly reduced the Holocene opal content and does not allow calculation of paleoproductivity. The intensity of opal dissolution is reflected by dissolution stages of both the diatomParalia sulcata and sponge spicules. The intensity of dissolution is negatively correlated to the sedimentation rate and appears to be controlled by silica-undersaturated environment on the sea floor and the uppermost sediment layer.  相似文献   

9.
Paramuricea clavata (Cnidaria, Octocorallia) is an important ecosystem engineer of coralligenous assemblages increasingly threatened by anthropogenic activities and climate changes. As climate warming is predicted to continue in the coming years it is important to hypothesize future scenarios. Here we tested the influence of gorgonian colonies on sedimentation rates and vagile fauna trends, comparing sediments collected by traps inside and outside a gorgonian garden, in a coralligenous community of the Western Ligurian Sea, at 32 m depth, over a period of 1 year. The results indicated that sea fans created a sort of homeostatic effect on the surrounding habitat. We found evidence that where gorgonian colonies were present, the monthly fluctuations of sediments rate were lower than outside a garden. Gorgonian colonies also influenced the distribution of the associated vagile fauna; these organisms were generally more abundant inside than outside the garden. The data collected in this work appear to confirm the role of P. clavata as an ecosystem engineer, affecting biomass and variability of the surrounding habitat at both spatial and temporal scales.  相似文献   

10.
This study applied the loss after combustion (LAC) method and the acid decalcification (ADC) method to quantify different components of an excavating sponge. Samples of dried coral skeleton of Favia sp. invaded by the Indo‐Pacific excavating sponge Cliona orientalis Thiele, 1900 were used. The sponge tissue penetrated the 12‐mm‐thick samples to approximately 10 mm. The average proportional weight of organic matter, siliceous spicules, calcareous substrate and salts in the entire samples was found to be respectively 2.5%, 4.4%, 90.5% and 2.5% of dry weight applying the LAC method, and 2.9%, 5.9%, 89.0% and 2.3% of dry weight applying the ADC method. Respective volumetric proportions of the organic matter, spicules, substrate and salts were then calculated to be 6.4%, 5.5%, 85.2% and 3.0% of volume with the LAC method, and 7.4%, 7.2%, 82.7% and 2.7% of volume with the ADC method. The LAC method showed low variability of data and is simple and fast and therefore is recommended. The ADC method generated very similar results to the LAC method. However, due to the handling involved in the ADC method, more than half of the spicules may be lost and the method is therefore not recommended unless careful data corrections are considered. In addition, the buoyant weight method was used to quantify actual substrate weight in the fresh sponge‐substrate samples. This method was found to be at least 97% effective, revealing that buoyant weights can potentially be used to quantify bioerosion rates of excavating sponges. To our knowledge, this is the first study to systemically quantify organic and inorganic components of an excavating sponge and its calcareous substrate, providing improved standard methods for future studies.  相似文献   

11.
We report on a hexactinellid sponge new to science, Walteria demeterae sp. nov., which was collected from the northwestern Pacific seamounts at depths of 1271–1703 m. Its tubular and basiphytous body, extensive lateral processes, numerous oval lateral oscula which are irregularly situated in the body wall, the presence of microscleres with oxyoidal, discoidal and onychoidal outer ends, and the absence of anchorate discohexasters, indicate it belongs to the genus Walteria of family Euplectellidae, which is also supported by molecular phylogenetic evidence from 18S, 28S, 16S rRNA and cytochrome c oxidase subunit I (COI) gene sequences. The unique morphotype, which is structured by a thin and rigid framework of body wall and lateral processes consisting of diactins, characterizes it as a new species. Local aggregations of individuals of this new species coupled with their associated macrofauna in the Suda Seamount are reported, highlighting its functional significance in providing biogenic microhabitats in the deep sea.  相似文献   

12.
The study of epibionts on habitat engineering ascidians is of increasing interest because changes in the population structure of the latter may affect associated communities, especially in the case of commercially exploited species. The solitary ascidian Microcosmus sabatieri lives on rocky cliffs in the Eastern Mediterranean and is harvested in certain Aegean areas. Its hard, wrinkled tunic is usually fouled by various epibionts both sessile and motile. Sponges are an important component of this complex and their biomass may be higher than that of the ascidian itself, strongly affecting diversity and abundance of the motile epifauna. The aim of this study was to examine in detail the structure of the epibiotic sponge assemblage on ascidians collected from their main fishing grounds in the South Aegean Sea. A rich (41 species) and taxonomically diverse sponge assemblage was found, while only eight species contributed 80% of the total sponge cover. Most of the epibiotic sponges commonly grow on the surrounding sublittoral cliffs. The encrusting sponge growth form prevailed in cover of the ascidian tunic, while two massive species dominated in terms of frequency of appearance and abundance. Ascidian dimensions, weight and volume were significantly correlated with sponge diversity, abundance and cover area, thus structuring the epibiotic sponge assemblage. Spatial patterns in sponge cover were not clear, but a general declining NW to SE trend in sponge richness, abundance and cover appeared in accordance with previous records. Sponge distribution on the ascidian tunic presented a clear pattern related with characteristic features of the ascidian: the posterior zone supported the richest and most expansive sponge fauna. The ecosystem-engineering process performed by the ascidian is enhanced by the diverse epibiotic sponge assemblage, thus further increasing habitat complexity in this space-limited, temperate, sublittoral, rocky environment.  相似文献   

13.
The present study focuses on the reproductive success of transplants of the bath sponge Spongia officinalis Linnaeus, 1759, with the aim of investigating the possibility of restocking this species, one of the most endangered organisms of the Mediterranean sessile zoobenthos. Transplants of S. officinalis, collected from a wild population along the Apulian coasts (Ionian Sea, Italy), have been moved into an area where the species was present in the past. The transplants consisted both of specimens in toto and of fragments of different sizes, obtained after having cut the mother sponge into pieces. All transplanted sponges showed complete cicatrisation of the cut surfaces within a month of the initial manipulation and had a survival rate of 100% throughout the 12 months of the study. From the present investigation, it has emerged that the reproductive effort and the larval release by the transplants do not differ significantly from those shown by the source population. This successful technical approach supports its application as a strategy for restocking the population of this endangered species.  相似文献   

14.
Particulate matter was sampled for hydrocarbon analyses at three anchor stations in Kiel Bight during different seasons (autumn, winter and spring). Additionally, the following parameters were measured: salinity, temperature, nutrients, chlorophyll, dissolved organic carbon and phytoplankton composition. From these concomitant measurements showing normal hydrographic or meteorologic situations, it was concluded that no intrusions of water masses occurred during the sampling periods; all collected material was produced at or near the sampling location under biological conditions which are encountered normally in this region at these times. During every season the concentration of biogenic hydrocarbons exceeded that of the petrogenic ones. Among the biogenic hydrocarbons the concentration of heneicosahexaene (HEH) was predominant, but in highly variable concentrations, depending on phytoplankton activity. No direct correlation between individual hydrocarbons and plankton species could be established, but a quantitative relationship between the biogenic hydrocarbons and the biological summation parameter was obvious.  相似文献   

15.
Phosphatized biogenic limestones and phosphorites with initial Fe-Mn mineralization dredged from the summit surface of the Kammu Seamount (Milwaukee Seamounts, northwestern Pacific) are studied. The rocks are largely composed of nannofossils and planktonic foraminifers with an admixture of benthic foraminifers, bryozoans, and other organic remains, presumably including bacterial ones. The nannofosssil and foraminiferal assemblages indicate the Quaternary age of the sediments, and their phosphatization is consistent with the phosphatization age determined previously based on nonequilibrium uranium (within the limits of 1 My). The age of phosphatization and the Fe-Mn mineralization in the sediments from Pacific seamounts that young implies the dependence of these ore-forming processes on oceanic environments favorable for ore accumulation rather than on their age.  相似文献   

16.
硅元素深刻影响着地表物质循环,是地表过程、陆海相互作用和全球碳循环研究的关键元素之一。在已有的陆-海生物硅研究中,大多数没有考虑生物硅组成在区域硅循环中的作用,因此开展不同来源与组成生物硅参与下的地表与陆-海硅循环研究是非常必要的。硅藻、硅鞭毛藻、植硅体、放射虫和海绵骨针是生物硅的主要存在形式,不同来源的生物硅由于化学性质的差异在硅生物地球化学循环过程中扮演着不同的角色,影响着生物硅的溶解速率与硅的埋藏等过程。今后应采用复合技术手段,重视"新硅"和"老硅"在硅循环中的差异化作用以及对分析测定结果的影响,并加强这方面的定量研究、过程与机理研究以及系统的综合性研究,特别是针对复杂的环境样品的多学科交叉综合研究。  相似文献   

17.
A late Paleocene‐early Eocene (c. 60–53 Ma) poriferan fauna, comprising hexactinellids (Class Hexactinellida), astrophorids (Class Demospongiae: Family Astrophorida), and lithistids ("lithistid” Demospongiae) has been identified from the Tutuiri Greensand outcropping on the north coast of Chatham Island, New Zealand. Most of the fossils are hexactinellids, comprising extremely delicate siliceous networks embedded in friable sandstone. The sediment matrix within and around these skeletons contains numerous siliceous demosponge spicules, many of which are exceptionally well preserved. The soft friable matrix of the Tutuiri Greensand has made extraction a relatively simple process, making taxonomic identification of the material, and comparison with adjacent Recent and other New Zealand Eocene faunas possible. These sponge body fossils and spicule microfossils indicate a fauna that was once dominated by hexactinellids, lithistid, and astrophorid demosponges. A qualitative comparison of the abundance and diversity of the Tutuiri Greensand sponge fauna with the present‐day Chatham Rise sponge fauna indicates that the late Paleocene‐early Eocene fauna is as diverse as the Recent fauna, for the hexactinellid sponges and astrophorid demosponges, and much more diverse for lithistid sponges. The paleoecology of the Tutuiri Greensand has been interpreted as inner to mid shelf water depths (50–250 m) but the poriferan fauna described here is more like that of the present‐day soft sediment benthic environment of the Chatham Rise at 800–1200 m.  相似文献   

18.
The calcarean sponge Paraleucilla magna is classified as being an invasive species on the Mediterranean Sea, where it causes economic damages to mollusc farms. On the Brazilian coast, this species is considered to be cryptogenic, and information on its ecology is scarce. The same is true for Sycettusa hastifera, another calcarean sponge with a worldwide distribution. Data on the ecology of these species could help in elucidating their potential to become a threat if they are found to be exotic species in Brazil. In the present work, we studied habitat selection, growth and mortality of early juveniles of P. magna and habitat selection of S. hastifera in a Marine Reserve from Southeastern Brazil, where these species are abundant in the benthic community. Granite plates were used for habitat selection analysis, varying in substrate inclination (vertical and horizontal) and exposure to light and hydrodynamism (exposed and sheltered). To analyse the growth and mortality rates, sponges were mapped and then measured once a week for 10 weeks. If a monitored sponge was not found in the following week, it was considered to be dead. Our results showed that, although P. magna and S. hastifera are capable of inhabiting substrates exposed to different environmental conditions, they showed habitat preferences. Growth of the juveniles of P. magna seemed not to have damaged any neighbouring invertebrates. The mortality of juveniles of this species was higher during the first 2 weeks of life but its causes could not be elucidated.  相似文献   

19.
The diatom species composition of settling biogenic silica particles collected in sediment traps was compared with the underlying sediment to determine the preservation of the various diatom species and to investigate the potential of biogenic silica as an indicator for changes in paleo-upwelling intensity. During the Netherlands Indian Ocean Programme (NIOP), settling particles were collected at two sampling sites off Somalia (NW Indian Ocean) for 9 months, from June 1992 to February 1993. One sediment trap array was deployed on the Somali slope directly below one of the main upwelling gyres, and a second array, meant as a reference site to reflect pelagic sedimentation, was moored in the Somali Basin away from direct coastal upwelling influence. At both sites diatoms represented over 90% of the total opal microorganisms. On the Somali slope, total annual diatom flux was 12.6×109 valves m−2, 76% of which was collected during the 112 d of the southwest monsoon, with peak fluxes in October, the end of the upwelling season. In the Somali Basin, the total annual flux was lower, 4.8×109 valves m−2, and only 39% was collected during the SW monsoon period (98 d). At both sampling sites, a distinct seasonal diatom species succession of ‘pre-upwellers’, ‘upwellers’ and ‘oceanic species’ was apparent. Although only a small part of the diatom assemblage escaped dissolution at the sediment–water interface, two species, Thalassionema nitzschioides and Chaetoceros resting spores, were preserved in the sediment, indicating that they are resistant to dissolution at the sediment–water interface. Eighty one percent of the deposition of Thalassionema nitzschioides and 78% of the deposition of Chaetoceros occurred during the upwelling period. Since these two species are the dominant component of the diatom assemblage in the sediments, and thus determine the biogenic silica content, we conclude that this preserved biogenic silica reflects the upwelling in the surface layer of the water column. On the Somali Margin, variations in biogenic silica flux as inferred from sedimentary records can therefore be used as an indicator for changes in paleo-upwelling intensity.  相似文献   

20.
Abstract. The macrofaunas associated with the three morphologically different North Aegean Sea sponge species Agelas oroides, Aplysina aerophoba , and Axinella cannabina were compared. The faunal abundance was not related to sponge surface area for any of the three species. Each sponge species supported a significantly different number of individuals per unit canal volume; A. aerophoba supported the most, A. oroides the least. A. aerophoba supported the highest species richness, A. cannabina the lowest. Canal volume was a good predictor of associated faunal abundance and species richness for two of the three sponge species. Faunal abundance was also directly related to sponge mean canal diameter. The species composition of associated fauna was similar on A. aerophoba and A. oroides and significantly different on A. cannabina .  相似文献   

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