Soft Bottom Sediments Research Articles

Kinorynchs from sea-grass beds in south eastern Australia - with notes on a new collecting method

Kinorhynchs are usually collected from soft bottom and sandy sediments, whereas their occurrence in sea-grass beds rarely has been explored. In the present study we developed two new collecting methods that can recover specimens from amongst sub-tidal sea-grass beds and mangrove mud. Several species of kinorhynchs were found and one could be identified as Echinoderes teretis Brown, 1985. The species was originally found in silty mud and described from localities in Sydney Harbour and Broken Bay. We recorded the species in the Clyde River Estuary and Candlagan Creek, some 250 km further south, and in sub-tidal mud and tidal mud, also in Lake Wellington in the Gippsland Lakes, Victoria. The presence of E. teretis and several unidentifiable kinorhynch species in sea-grass beds and mangrove vegetation indicates that the provided collecting methods can reveal new information about kinorhynch diversity in such habitats.

Ecosystem engineering at the sediment–water interface: bioturbation and consumer-substrate interaction

In soft-bottom sediments, consumers may influence ecosystem function more via engineering that alters abiotic resources than through trophic influences. Understanding the influence of bioturbation on physical, chemical, and biological processes of the water-sediment interface requires investigating top-down (consumer) and bottom-up (resource) forces. The objective of the present study was to determine how consumer bioturbation mode and sediment properties interact to dictate the hydrologic function of experimental filtration systems clogged by the deposition of fine sediments. Three fine-grained sediments characterized by different organic matter (OM) and pollutant content were used to assess the influence of resource type: sediment of urban origin highly loaded with OM and pollutants, river sediments rich in OM, and river sediments poor in OM content. The effects of consumer bioturbation (chironomid larvae vs. tubificid worms) on sediment reworking, changes in hydraulic head and hydraulic conductivity, and water fluxes through the water-sediment interface were measured. Invertebrate influences in reducing the clogging process depended not only on the mode of bioturbation (construction of biogenic structures, burrowing and feeding activities, etc.) but also on the interaction between the bioturbation process and the sediments of the clogging layer. We present a conceptual model that highlights the importance of sediment influences on bioturbation and argues for the integration of bottom-up influence on consumer engineering activities.

Uca marionis Mud Volcanoes: A Unique Ichnological Tool from the Bay of Bengal Coast of India for Ready Assessment of Beach Stability

Formation of burrow-head mud volcanoes by the mud-loving amphibious crab Uca marionis (Alcock) selectively on the either sides of estuary mouths along the Bay of Bengal coast, eastern India, requires peculiar substratal and biological conditions where soft muddy bottom sediments of the coastal mudflats are covered by a thin blanket of relatively rigid beach sands that provide a false substrate stability. Shallow-seated mud layers, being within the substrate penetration power, allow opportunistic burrowing by the crab and consequent oozing out of internal mud slur to form conical heaps of mud resembling volcanic cones. Removal of this thin sand cover prompts very fast erosion of the bottom mud and consequent widening of the estuary mouth and rapid beach erosion. A thick and rigid sand cover restricts deeper burrowing by the crabs. Uca marionis mud volcanoes, by virtue of limited power of vertical penetration down to required muddy substrate and requirement of special substrate conditions and geomorphic position along the coastal zone, are considered as unique ichnological tools that readily identify and precisely demarcate highly unstable or erosion-prone beach sectors, and thus help in planning, protection and execution of various coastal developmental programs. Wide zoogeographic distribution of Uca in tropical-subtropical sea coasts greatly enhances the application potential of this new ichnological tool. Fossilized biogenic mud volcanoes in post-Jurassic geologic records would ease taxonomic identification of the ancient trace producers and coastal marine palaeogeomorphic interpretations.

Ontogenetic patterns of concentration indicate lagoon nurseries are essential to common grunts stocks in a Puerto Rican bay

Estimates of abundance and size of three commercially exploited grunt species indicate ontogenetic changes in habitat utilization concentrate their juveniles within the lagoon of the Bay of La Parguera, Puerto Rico. Eleven biotopes, defined by four benthic structures (reef, mangrove, vegetation beds and unconsolidated sediments) and three geographic zones (inner lagoon, outer lagoon and bank shelf) were sampled randomly by visual surveys. French, bluestriped and white grunt ( Haemulon flavolineatum, Haemulon sciurus and Haemulon plumeri) were common in the bay and appeared to exhibit similar life history patterns of cross-shelf migration and habitat selection. Recently settled grunts were dispersed over vegetated and unconsolidated soft-bottom sediments of the bay. The juvenile stage occurred in highest densities in shallow lagoon biotopes among the submerged prop-roots of mangrove stands and on inshore reefs. Length data indicates that grunts migrate offshore to adult habitat via increasingly deep reefs. Indices of biotope nursery function based on standing stock estimates of juveniles identified three biotopes, all within the inner lagoon as essential habitat for juveniles of 5–10 cm length interval. This concentration of juveniles within biotopes of the lagoon could represent a bottleneck to recruitment for grunt stocks. Evidence that quantity and quality of lagoon nurseries may limit recruitment indicates that these areas represent a key component of a marine protected area designed to restore fisheries within the bay.

The invasive red alga Gracilaria vermiculophylla in the Baltic Sea: adaptation to brackish water may compensate for light limitation

The recent introduction of Gracilaria vermiculophylla (Rhodophyta) to the Kiel Fjord area was a reason for concern, since this red macroalga performs best under mesohaline conditions and thus appears well adapted to thrive and spread in the Baltic Sea environment, A systematic survey on a coastal range of 500 km in 2006 and 2007 indicated considerable Multiplication and spreading of G. vermiculophylla within Kiel Fjord, but provided little evidence of long-distance transport. Nonetheless, flow-through growth experiments conducted at a range of salinities under ambient light showed that G. vermiculophylla should be able to grow in most of the Baltic Sea. Growth declined only below a salinity of 5.5. High water temperatures in summer seem to reduce resistance against low salinity. Growth of G, vermiculophylla in the SW Baltic is limited by light and is only possible during summer and above a depth of 3 m. Drifting fragments are dispersed by currents. Either they sink to deeper waters, where they degrade, or they accumulate in shallow and sheltered waters, where they form perennial mats. These overgrow not only soft bottom sediments, but also stones, which are an important habitat to Fucus vesiculosus, the main native perennial alga in the Baltic Sea. As compared to F. vesiculosus, G. vermiculophylla seems to represent a preferred refuge for mesograzers and other invertebrates, particularly in winter. Nonetheless, feeding trials showed that potential grazers avoided G. vermiculophylla relative to F vesiculosus. Daily biomass uptake by grazers associated with G. vermiculophylla in nature did not exceed 2 g kg(-1) and is <11% of average daily net growth (18.5 g kg(-1)) in the first 2 m below sea level. Consequently, feeding may not be sufficient to control the spread of G. vermiculophylla in the SW Baltic. Our study suggests that absence of feeding enemies and adaptation to brackish water may allow G. vermiculophylla to invade most shallow coastal waters of the inner Baltic Sea despite light limitation.

Infaunal Macrobenthic Community of Soft Bottom Sediment in a Tropical Shelf

Abstract Studies of benthic communities in tropical shelf waters are limited. In this study, we deal with the infaunal benthic community of soft bottom sediment of the tropical eastern Arabian Sea shelf. Benthic macroinfauna was sampled with a Smith–McIntyre grab at 30 stations on the continental shelf of the eastern Arabian Sea (northwest coast of India) during January–February (premonsoon) and November (postmonsoon) 2003 from 30 to 200 m depth. The faunal composition, abundance, and diversity of species together with environmental parameters are reported. The sites were clustered into “associations” on the basis mainly of sediment texture and depth. Mean benthic abundance was high in the shallow and intermediate depths and decreased toward deeper areas. Diversity increased with depths up to 100 m during both seasons and decreased beyond 100 m depth. The dominant benthic group was Polychaeta during both seasons. Species richness and diversity were higher during premonsoon compared with postmonsoon. Shall...

Spartina anglica eradication experiment and in situ monitoring assess structuring strength of habitat complexity on marine macrofauna at high tidal level

The cordgrass Spartina anglica is an introduced species that tends to invade sheltered sand and mudflats, at the upper low marsh level. In Arcachon Bay, a lagoon in South West of France, the cordgrass can also replace Zostera noltii beds. The consequence of cordgrass presence on macrobenthic fauna was estimated and compared to adjacent habitats (bare sands, Z. noltii sea grass beds) during one year. The communities of the three habitats were characterised by low species richness, low abundance and biomass (when Hydrobia ulvae, 90% of abundance, is not considered) and high seasonal stability. The infaunal assemblages were particularly homogeneous between habitats without any characteristic species. Cordgrass eradication experiments were performed and zoobenthic recolonisation was observed the following year. Modifications in benthic fauna were observed on epifauna only. These results highlight the limited structuring effect of habitat heterogeneity at high tidal levels and in soft-bottom sediments where desiccation becomes the dominant factor determining infauna community structure.

Brittle stars (Echinodermata: Ophiuroidea) in the German Bight (North Sea)—species diversity during the past 130 years

In this study, an overview of the current species composition of ophiuroids off Helgoland, German Bight (North Sea) is given. In addition, abundance and distribution of ophiuroids on different types of soft bottom sediments taken by van Veen grab samples around Helgoland were recorded. The literature was reviewed in order to outline the diversity of ophiuroid species over the past 130 years in the inner German Bight. In the historical literature, quantitative references often apply to verbal descriptions and thus make comparisons to modern data and assessment of possible changes in abundance rather subjective.In total, six ophiuroid species were identified off Helgoland: Acrocnida brachiata, Amphiura filiformis, Amphipholis squamata, Ophiothrix fragilis, Ophiura albida and Ophiura ophiura. The species found in this study had also been reported by previous investigators and are regarded as ‘common’ species in the German Bight. Occasional findings in this area refer to Amphiura chiajei, Ophiopholis aculeata, Ophiocten affinis and Ophiura sarsi, which are regarded here as ‘rare’ species. These findings, however, do not indicate sustainable changes in the species diversity over time.Apart from Acrocnida brachiata, a newcomer in the 1970s, findings of the common species mentioned above can be dated back to 1875. Therefore, a fairly stable composition of brittle stars is represented in the inner German Bight during the past 130 years.

Response of Benthic Protozoa and Thraustochytrid Protists to Fish Farm Impact in Seagrass (Posidonia oceanica) and Soft-Bottom Sediments

We investigated the impact of fish farm biodeposition on benthic bacteria, thraustochytrid protists, and heterotrophic protozoa (nanoflagellates and ciliates) in an oligotrophic area of the Mediterranean Sea. The fish farm impact was investigated both on a seagrass (Posidonia oceanica) bed and on soft bottom sediments. In both systems, sediment samples were collected with a multicontrol sampling strategy (i.e., beneath the fish farm and at three control sites per system). The uneaten food pellets supplied to the fish determined the accumulation of sediment organic matter and the enhancement of protein content in impacted sediments (both seagrass bed and soft sediments). In both systems, the abundance and biomass of heterotrophic protists increased significantly beneath the fish farm, but the structure of the protist assemblages responded differently in vegetated and unvegetated sediments. Thraustochytrid abundance increased significantly in impacted seagrass. These results provide evidence that the structure of protist assemblages respond significantly to fish farm biodeposition and indicate that the monitoring of these benthic components provides complementary information for the assessment of the fish farm impact on the benthic systems.

Nutritional value of sediments for macroinvertebrate communities in shallow eutrophic waters

The role of the nutritional quality of non-polluted soft-bottom sediments as a factor structuring in situ macroinvertebrate communities was studied in shallow eutrophic waters in The Netherlands. Sediments from clean sites were collected and analyzed for general characteristics (e.g. grain-size distribution) and nutritional value (e.g. C, N, P, polyunsaturated fatty acids). Also, macroinvertebrates were collected from these sediments and identified. In laboratory bioassays, Chironomus riparius midge larvae were exposed to these sediments to assess the nutritional value of each sediment. The abundance of detritivore taxa was positively associated with polyunsaturated fatty acids, bacterial fatty acids, pigments, and mineralization rate. These variables represent newly produced organic matter originating from the pelagic part of watersystems. Therefore, there seems to be a strong connection between the organic matter production in the pelagic part of watersystems and sediment food quality. The growth response of C. riparius larvae measured in the bioassay showed strong correlations with the abundance of detritivorous Chironomidae taxa in the sediment samples. Herbivorous and carnivorous taxa did not correlate with the bioassay results. Highest growth of C. riparius was observed in sediments with abundant detritivorous Chironomidae taxa and lowest growth was observed in sediments with taxa with other modes of feeding. Therefore, growth of C. riparius seems to effectively indicate the nutritional value of sediments for sediment bulk feeders. The use of bioassays with midge larvae permits evaluation of the importance of organic matter as a determinant of community structure without the confounding effects of other factors such as oxygen regime or stability of the substrate, which tend to covary with organic content. It is postulated that such non-food variables select the species that dominate sites. Yet, nutritional value determines the overall density of detritivores and, therefore, is concluded to be a major factor influencing faunal communities in shallow eutrophic waters

Manganese induced immune suppression of the lobster, Nephropsnorvegicus

Manganese (Mn) is one of the most abundant elements on earth, particularly in the soft bottom sediments of the oceans. As a micronutrient Mn is essential in the metabolic processes of organisms. However, at high concentrations the metal becomes a neurotoxin with well-documented effects. As a consequence of euthrophication, manganese is released from bottom sediments of coastal areas and the Norway lobsters, Nephrops norvegicus, can experience high levels of bioavailable Mn 2+. Here, we present the first report showing that Mn also affects several fundamental processes in the mobilisation and activation of immunoactive haemocytes. When N. norvegicus was exposed to a realistic [Mn 2+] of 20 mg l −1 for 10 days 24.1 μg ml −1 was recorded in the haemolymph. At this concentration the total haemocyte count was reduced by ca. 60%. By using BrdU as a tracer for cell division, it was shown that the proliferation rate in the haematopoietic tissue did not increase, despite the haemocytepenia. A gene coding for a Runt-domain protein, known to be involved in maturation of immune active haemocytes in a variety of organisms, was identified also in haemocytes of N. norvegicus. The expression of this gene was >40% lower in the Mn-exposed lobsters as judged by using a cDNA probe and the in situ hybridisation technique. In response to non-self molecules, like lipopolysaccharide (LPS), the granular haemocytes of arthropods are known to degranulate and thereby release and activate the prophenoloxidase system, necessary for their immune defence. A degranulation assay, tested on isolated granular haemocytes, showed about 75% lower activity in the Mn-exposed lobsters than that for the unexposed. Furthermore, using an enzymatic assay, the activation per se of prophenoloxidase by LPS was found blocked in the Mn-exposed lobsters. Taken together, these results show that Mn exposure suppressed fundamental immune mechanisms of Norway lobsters. This identifies a potential harm that also exists for other organisms and should be considered when increasing the distribution of bioavailable Mn, as has been done through recently introduced applications of the metal.

Benthic macroinvertebrate community structure in relation to food and environmental variables

The relative contribution of sediment food (e.g. organic matter, carbohydrates, proteins, C, N, polyunsaturated fatty acids) and environmental variables (e.g. oxygen, pH, depth, sediment grain size, conductivity) in explaining the observed variation in benthic macroinvertebrates is investigated. Soft bottom sediments, water and benthic macroinvertebrates were sampled in several water systems across The Netherlands. The variance partitioning method is used to quantify the relative contributions of food and environmental variables in structuring the benthic macroinvertebrate community structure.It is assumed that detritivores show a significant relationship with sediment food variables and carnivores and herbivores do not. The results of the variance partitioning method with data sets containing only detritivores, herbivores or carnivores confirm this assumption. This indicates that the variance partitioning method is a useful tool for analyzing the impact of different groups of variables in complex situations. Approximately 45% of the total variation in the macroinvertebrate community structure could be explained by variables included in the analyses. The variance partitioning method shows that sediment food variables contributed significantly to the total variation in the macroinvertebrate dataset. The relative importance of food depends on the intensity of other environmental factors and is lower on broad spatial scales than on smaller scales.The results of the partitioning depend on the selected variables that are included in the analyses. The method becomes problematic in case variables from different groups of variables (e.g. one food variable and one environmental variable) have a high inflation factor and thus are collinear. The choice of the variable that is left out impacts the variance allocated to the different groups of variables.The variance partitioning method was able to detect the spatial scale dependent contribution of food variables in structuring macroinvertebrate communities. This spatial scale dependency can also be caused by the size, the composition, and the heterogeneity of the dataset. Performing extra analyses in which specific samples are removed from the original dataset can give insight in under- or overestimation of the impact of certain factors and offers the possibility to test the robustness of the obtained results.

Macrobenthic community structure of soft-bottom sediments at the Belgian Continental Shelf

Within the frame of different research projects, a large number of sites at the Belgian Continental Shelf (BCS) have been sampled for the macrobenthos between 1994 and 2000. These samples cover a diverse range of habitats: from the sandy beaches to the open sea, from the gullies between the sandbanks to the tops of the sandbanks, and from clay to coarse sandy sediments. To investigate the large-scale spatial distribution of the macrobenthos of the Belgian Continental Shelf, the data of all these research projects—728 samples—were combined and analysed. By means of several multivariate techniques, 10 sample groups with similar macrobenthic assemblage structure were distinguished. Each sample group is found in a particular physico-chemical environment and has a specific species composition. Four sample groups differ drastically, both in habitat and species composition, and are considered to represent four macrobenthic communities: (1) the muddy fine sand Abra alba– Mysella bidentata community is characterized by high densities and diversity; (2) the Nephtys cirrosa community occurs in well-sorted sandy sediments and is characterized by low densities and diversity; (3) very low densities and diversity typify the Ophelia limacina– Glycera lapidum community, which is found in coarse sandy sediments and (4) the Eurydice pulchra– Scolelepis squamata community is typical for the upper intertidal zone of sandy beaches. These macrobenthic communities are not isolated from each other, but are linked through six transitional species assemblages. The transition between the A. alba– M. bidentata community and the N. cirrosa community is characterized by a reduction in the mud content and is dominated by Magelona johnstoni. The transition between the N. cirrosa and the O. limacina– G. lapidum community is distinctive by decreasing densities and coincides with a gradual transition between medium and coarse sandy sediments. From the N. cirrosa to the E. pulchra– S. squamata community, transitional species assemblages related to the transition from the subtidal to the intertidal environment were found. Each community or transitional species assemblages was found over a specific range along the onshore–offshore gradient, four types can be discerned: (1) almost restricted to the near-shore area, but possible wider distribution; (2) distributed over the full onshore–offshore gradient; (3) restricted to the near-shore area and (4) restricted to the sandy beach environment. The diversity pattern on the BCS follows this division, with species rich and poor assemblages in the near-shore area to only species poor assemblages more offshore. The distribution and diversity patterns are linked to the habitat type, distinguished by median grain size and mud content.

Horizontal and vertical variabilities of mercury concentration and speciation in sediments of the Gdansk Basin, Southern Baltic Sea

The mercury compounds introduced to the environment because of anthropogenic activity are accumulated, mainly, in marine sediments. Both distribution of mercury in the Baltic Sea and factors affecting it are remain largely unknown. Due to its complex chemistry and variable conditions in the Baltic Sea bottom sediments, mercury may be reemitted to the overlaying water, and thus to the environment. The aim of this study was twofold. Total mercury contents were measured in sediments of the Gdansk Basin along a Vistula mouth (main source)––Gdansk Deep (deposition area) transect in order to assess spatial distribution of the element. Soft and sandy bottom sediment cores were collected and cut into slices. The mercury measurements consisted of acid digestion followed by CV-AAS determination. A five-step sequential extraction procedure involving measurements of mercury species water soluble, bound to humic substances and insoluble, was employed in order to investigate mercury speciation. On the basis of speciation results stability and remobilisation potential was assessed. The second aim was demonstrating that mercury gradients in vertical profiles of the investigated sediment cores exist. Total mercury contents varied in range from 28 ng/g dw to 844 ng/g. Mercury associated with organic matter and sulphides, (respectively 39% and 49%) were the dominant species of the element. The results indicated that the river run-off is a source of mercury in the area. Vertical gradients of both total content and speciation of mercury in the soft sediments were attributed to both remobilisation from sediments, and decreasing trend in the anthropogenic load of the element deposited to sediments.

Pore water nutrient profiles and dynamics in soft bottoms of the northern Baltic Sea

Chemical profiles of nutrients at the sediment–water interface were measured in the northern Baltic Sea. A whole core squeezer technique capable of mm-scale resolution was used to obtain the vertical profiles of NO3 −, NO2 −, o-P, NH4 + and Si in the soft bottom sediments. The profiles were compared with nutrient flux and denitrification measurements. In the Gulf of Finland, the profiles revealed a marked chemical zonation in NO3 − and NO2 − distribution indicating strong potential of nitrification just under the sediment surface followed by a layer of denitrification down to a depth of 30 mm. Below the depth of 20 mm NO3 − was usually absent, whereas other nutrients were increasing steadily in concentration. A distinct minimum of NO3 − was observed at the sediment–water interface, suggesting NO3 − uptake by a microbial biofilm and/or active denitrification at the suboxic microniches usually present in organic-rich sediments. At the deep stations in the Baltic Proper, the NO3 − concentration in pore water, as well as denitrification, were very low. The concentrations of NH4 +, o-P and Si were usually increasing steadily with depth.

Macrobenthic resources of the shallow soft-bottom sediments in the eastern English Channel and southern North Sea

To obtain a baseline for future comparisons and to assist in the conservation of marine biodiversity, the distribution patterns and faunal composition of shallow (0–15 m depth) macrobenthic assemblages were studied along the French coast of the eastern English Channel and southern North Sea from two surveys conducted in 1998 and 2000. A total of 227 sites were sampled from Cap d’Ailly to the Belgian border, from which a total of 167 species were collected. Species richness, abundance and biomass were all increased in the vicinity of outflows from harbours, major bays and estuaries. Three principal macrobenthic assemblages were defined: (i) an Ophelia borealis medium to fine sand assemblage; (ii) a muddy heterogeneous sediment assemblage; and (iii) an Abra alba muddy fine sand assemblage. The Abra alba assemblage covered approximately 80% of the seabed in the survey area. Sediment characteristics and a latitudinal gradient accounted for a significant proportion of the observed variability in assemblage distribution patterns. In the eastern English Channel, the distribution patterns of species diversity, abundance and biomass values were most continuous, whereas in the southern North Sea a more heterogenous distribution was observed. 2003 International Council for the Exploration of the Sea. Published by Elsevier Science Ltd.

Distribution of benthic diatoms in relation to environmental variables in lowland streams

The composition (% relative abundance) of diatom assemblages from soft bottom sediments was studied at 75 sites situated in 46 rivers, brooks, and ditches in the islands of Hiiumaa and Saaremaa and in the lowland of West Estonia. Although the total number of recorded taxa was 205, the studied diatom assemblages consisted of 54, 55, 48, and 50 constant species in the drainage basin of Moonsund, the Gulf of Riga, Hiiumaa, and Saaremaa, respectively. The habitats of the dominating taxa were heterogenous and the most widespread species were Achnanthidium minutissimum, Martyana martyi, Meridion circulare, Cocconeis placentula, Planothidium lanceolatum, and Amphora pediculus. The Shannon–Weaver diversity (H′) index varied from 2.09 to 4.63. Multivariate analyses were used to identify the environmental variables governing the composition and structure of the benthic diatom assemblage. Principal Component Analysis (PCA) and Redundancy Analysis (RDA), based on 56 most abundant taxa, indicated differences in the composition and structure of diatom assemblages between different drainage basins as well as between the upper and lower stream courses. In the headwaters there prevailed small epipsammic diatoms (Martyana, Planothidium, Staurosira, Staurosirella). Different motile epipelic species from the genera Amphora, Navicula, Nitzschia, etc. were distributed abundantly in the lower courses of the streams. There was a positive correlation between order of the stream site and trophic level of water (R=0.35; p<0.05). Along a river system, the increasing order of the stream was accompanied by higher trophic level of water.

Distribution of a tetrabrominated diphenyl ether and its metabolites in soft-bottom sediment and macrofauna species

Sediment spiked with 14 C-2,2', 4, 4'-tetrabrominated diphenyl ether (BDE-47) was added as a single pulse, at a low or a high concentration, to intact soft-bottom sediments in a box-cosm system. The vertical distribution of the pollutant and the bioaccumulation in 39 different taxa of macro- fauna were analysed after 10, 20 and 29 wk exposure. Throughout the experimental period, 90% of the recovered BDE-47-derived radioactivity in the sediment was found within the upper 5 cm. The BSAF (biota-sediment accumulation factor) in the different taxa after 29 wk exposure varied between 0.4 and 16.3. The correlation between bioaccumulation and lipid content of all individual specimens in each box-cosm was significantly positive and explained between 11 and 64% of the variation. When the fauna was divided into groups with different feeding strategies, it was found that the mean BSAF was significantly higher for the surface deposit-feeders than for the suspension-feeders, subsurface feeders and the predators. The difference increased with time and was larger after 29 wk exposure than after 10 wk. We also tested whether there was a correlation between 15 N enrichment, i.e. trophic position, in the analysed species and bioaccumulation, but no such correlation was found. Water-soluble metabolites of BDE-47 were detected in 15 of the 39 macrofaunal species. There was no observable correlation between the presence of metabolites in the macrofauna and bioaccumulation of the pollutant.

New well-preserved scleritomes of Chancelloridae from the early Cambrian Yuanshan Formation (Chengjiang, China) and the middle Cambrian Wheeler Shale (Utah, USA) and paleobiological implications

From the early Cambrian of Yunnan, China, new chancellorid scleritomes assigned to Allonnia junyuani new species are described and compared with scleritomes of Chancelloria eros Walcott, 1920 from the Middle Cambrian of Utah, USA and isolated phosphatized chancellorid sclerites from the Georgina Basin of North Australia. Characters of the entirely preserved chancellorids offer new insight into the paleobiology of Chancelloridae. An irregular thickening at the inferred base of the narrow body end of Chancelloria eros from Utah is interpreted as a root bulb that anchored the sessile animal in the soft bottom sediment. Sclerites show gradual increase in size from the narrower towards the broader upper end of the chancellorid body. A central “gastral” lumen was not directly observed in any of the investigated specimens, but the orientation of sclerites towards the outer body surface indicates that the fossils are secondarily flattened due to compaction and were originally hollow. Taphonomy of isolated chancellorid sclerites from the Georgina Basin, Australia, indicates a biomineralization very different from that of sponge spicules, including the spongin spiculoids of demospongid Keratosa. Allonnia junyuani from Chengjiang (Yunnan) exhibits a prominent epidermis, probably with stable epithelian cell-to-cell connections. This feature excludes a sponge affiliation of the Chancelloridae and points towards a systematic position of this group within the epithelian-bearing animals and thus well above the Porifera.

NEW WELL-PRESERVED SCLERITOMES OF CHANCELLORIDAE FROM THE EARLY CAMBRIAN YUANSHAN FORMATION (CHENGJIANG, CHINA) AND THE MIDDLE CAMBRIAN WHEELER SHALE (UTAH, USA) AND PALEOBIOLOGICAL IMPLICATIONS

Abstract From the early Cambrian of Yunnan, China, new chancellorid scleritomes assigned to Allonnia junyuani new species are described and compared with scleritomes of Chancelloria eros Walcott, 1920 from the Middle Cambrian of Utah, USA and isolated phosphatized chancellorid sclerites from the Georgina Basin of North Australia. Characters of the entirely preserved chancellorids offer new insight into the paleobiology of Chancelloridae. An irregular thickening at the inferred base of the narrow body end of Chancelloria eros from Utah is interpreted as a root bulb that anchored the sessile animal in the soft bottom sediment. Sclerites show gradual increase in size from the narrower towards the broader upper end of the chancellorid body. A central “gastral” lumen was not directly observed in any of the investigated specimens, but the orientation of sclerites towards the outer body surface indicates that the fossils are secondarily flattened due to compaction and were originally hollow. Taphonomy of isolate...