Burrow Walls Research Articles

Oxygen dynamics and porewater transport in sediments inhabited by the invasive polychaete Marenzelleria viridis

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 504:181-192 (2014) - DOI: https://doi.org/10.3354/meps10737 Oxygen dynamics and porewater transport in sediments inhabited by the invasive polychaete Marenzelleria viridis Zeljko Jovanovic1, Morten Larsen1,2,3, Cintia Organo Quintana1, Erik Kristensen1, Ronnie N. Glud1,2,3,4,* 1Institute of Biology, University of Southern Denmark, Campusvej 55, 5230 Odense M, Denmark 2Scottish Association for Marine Science, Dunstaffnage Marine Laboratory, Oban PA37 1QA, UK 3Greenland Climate Research Center (CO Greenland Institute of National Resources), Kivioq 2, Box 570, 3900 Nuuk, Greenland 4Artic Research Center, C. F. Møllers Allè 8, 8000 Aarhus University C, Denmark *Corresponding author: rnglud@biology.sdu.dk ABSTRACT: The polychaete Marenzelleria viridis is an invasive species and often replaces the native Nereis diversicolor. This shift leads to more reduced conditions and changes in the biogeochemical function of the sediments. By combining imaging techniques for O2 (planar optodes) and irrigation patterns (rhodamine WT and brilliant blue), we investigated the relationship between irrigation and O2 dynamics in burrows of M. viridis. The investigated animals shifted between 2 modes of ventilation: ciliary pumping for 77% of the time and muscular pumping for 23% of the time. On average, muscular pumping was induced every 0.4 h. During ciliary pumping, oxic water was pumped into blind-ended burrows and into the surrounding sediment, inducing an upward porewater transport of O2-depleted water. This pattern was reversed during muscular pumping. The 2 pumping modes induced oscillating O2 penetration along the burrow wall and along the primary sediment-water interface. The average net downward irrigation rate, including both pumping modes, amounted to 11.1 × 10-3 ± 2.4 × 10-3 ml min-1. The estimated average oxic sediment volume was 2.1 ± 0.5 cm3 per burrow, and the burrow-specific O2 consumption was 45.6 ± 18.1 nmol min-1. M. viridis burrows and the ambient sediment are relatively O2 depleted, with intensified rates of O2 consumption, compared to similar-sized native N. diversicolor. The complex O2 dynamics induced a unique microenvironment that must favor meiofauna and microbial communities that are tolerant to oxic-anoxic oscillations or that have the ability to migrate along with the pulsing oxic-anoxic interface. KEY WORDS: Bioirrigation · Oxygen dynamics · Marenzelleria viridis · Planar optode · Rhodamine Full text in pdf format PreviousNextCite this article as: Jovanovic Z, Larsen M, Organo Quintana C, Kristensen E, Glud RN (2014) Oxygen dynamics and porewater transport in sediments inhabited by the invasive polychaete Marenzelleria viridis. Mar Ecol Prog Ser 504:181-192. https://doi.org/10.3354/meps10737 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 504. Online publication date: May 14, 2014 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2014 Inter-Research.

Quantitative estimation of bioturbation based on digital image analysis

Quantitative determination of modification of primary sediment features, by the activity of organisms (i.e., bioturbation) is essential in geosciences. Some methods proposed since the 1960s are mainly based on visual or subjective determinations. The first semiquantitative evaluations of the Bioturbation Index, Ichnofabric Index, or the amount of bioturbation were attempted, in the best cases using a series of flashcards designed in different situations. Recently, more effective methods involve the use of analytical and computational methods such as X-rays, magnetic resonance imaging or computed tomography; these methods are complex and often expensive. This paper presents a compilation of different methods, using Adobe® Photoshop® software CS6, for digital estimation that are a part of the IDIAP (Ichnological Digital Analysis Images Package), which is an inexpensive alternative to recently proposed methods, easy to use, and especially recommended for core samples. The different methods — “Similar Pixel Selection Method (SPSM)”, “Magic Wand Method (MWM)” and the “Color Range Selection Method (CRSM)” — entail advantages and disadvantages depending on the sediment (e.g., composition, color, texture, porosity, etc.) and ichnological features (size of traces, infilling material, burrow wall, etc.). The IDIAP provides an estimation of the amount of trace fossils produced by a particular ichnotaxon, by a whole ichnocoenosis or even for a complete ichnofabric. We recommend the application of the complete IDIAP to a given case study, followed by selection of the most appropriate method. The IDIAP was applied to core material recovered from the IODP Expedition 339, enabling us, for the first time, to arrive at a quantitative estimation of the discrete trace fossil assemblage in core samples.

Oxygen penetration through invertebrate burrow walls in Korean tidal flat

Macrofaunal burrows increase the surface area of the sediment-water interface, which has a great impact on the metabolism of aerobic microbes and the oscillation of reduced metabolites within the sediment. Given the importance of macrofauna in surficial sediments, the aim of this study is to examine the effects of burrow architectures on dissolved oxygen diffusion rates in comparison with unburrowed sediment, and thereby to evaluate the theoretical assumption used for modeling solute distribution in the burrow system using field samples. Employing microsensors, horizontal oxygen profiles were measured on a micrometer scale around burrows of seven invertebrates in tidal flats of the west coast of Korea. Oxygen diffusion distance through the burrow walls of seven invertebrates showed spatio-temporal variation with a range of 0.6 to 2.9 mm. Two groups of burrows were identified based on their oxygen diffusive properties relative to unburrowed sediments: 1) oxygen penetration similar to that of ambient sediments and 2) clearly enhanced oxygen penetration. Differences in the diffusive properties of the burrow wall were related to the burrow depth and diameter, existence of mucus lining on the wall, sediment grain size, and tidal phases. Also inhabitant activity was an important factor affecting oxygen penetration, which is discussed in the paper. These results further demonstrate that simplified assumptions (i.e. burrow structures are viewed as direct biogeochemical extensions of the sediment-water interface) may not be exact representation of the nature.

A cadaver unearthed: the anatomy of the Japanese living fossil <italic>Stirpulina ramosa</italic> (Bivalvia: Anomalodesmata: Clavagellidae) – the unique specimen in the collections of Emperor Shōwa

The only extant, preserved and complete specimen of Stirpulina ramosa has been discovered in the collections of the late Emperor Shōwa (Hirohito) and is described herein. Hitherto, only shells and the adventitious tubes of this species have been described. This study of the anatomy complements previous ones and adds further information as to how the adventitious tube is formed: that is, by the laying down of an organic, periostracum-like, template that is then biomineralized internally to form the tube and is externally plastered with the clasts that constitute the enclosing burrow wall. Such secretions are produced by pallial lobes that unite on the right side to create the characteristic sutured pleat in this region of the tube. The periostracum enclosing the so-interred animal is then secreted against the internal template of the tube. The shell of S. ramosa and, as a consequence, the musculature, is greatly disfigured as a result of the incorporation of the left valve into the fabric of the adventitious tube. This valve can, however, continue to grow within the tube, especially posteriorly. The right valve remains free inside the tube but grows only a little more anteriorly. The anterior mantle, with a minute pedal gape, is greatly thickened and secretes the watering pot component of the tube. In many anatomical respects, for example simultaneous hermaphroditism, S. ramosa still reflects the basic anomalodesmatan plan and such modifications as there are from the clavagellid form relate principally to the structure, formation and thus functioning of the adventitious tube. This study of S. ramosa has allowed the full spectrum of clavagellid adaptive radiation to be analysed and an evolutionary picture created which suggests that species of Clavagella/Dacosta and Stirpulina are Mesozoic (Late Cretaceous) remnants. Conversely, species of Bryopa and Dianadema are more modern, Late Oligocene and Palaeocene (Cenozoic), respectively, and possibly evolved in association with the emergence of the Indo-West Pacific centre of coral diversity, with a postulated average age of just 30 Myr. © 2013 The Linnean Society of London

A cadaver unearthed: the anatomy of the Japanese living fossilStirpulina ramosa(Bivalvia: Anomalodesmata: Clavagellidae) - the unique specimen in the collections of Emperor Shōwa

The only extant, preserved and complete specimen of Stirpulina ramosa has been discovered in the collections of the late Emperor Shōwa (Hirohito) and is described herein. Hitherto, only shells and the adventitious tubes of this species have been described. This study of the anatomy complements previous ones and adds further information as to how the adventitious tube is formed: that is, by the laying down of an organic, periostracum-like, template that is then biomineralized internally to form the tube and is externally plastered with the clasts that constitute the enclosing burrow wall. Such secretions are produced by pallial lobes that unite on the right side to create the characteristic sutured pleat in this region of the tube. The periostracum enclosing the so-interred animal is then secreted against the internal template of the tube. The shell of S. ramosa and, as a consequence, the musculature, is greatly disfigured as a result of the incorporation of the left valve into the fabric of the adventitious tube. This valve can, however, continue to grow within the tube, especially posteriorly. The right valve remains free inside the tube but grows only a little more anteriorly. The anterior mantle, with a minute pedal gape, is greatly thickened and secretes the watering pot component of the tube. In many anatomical respects, for example simultaneous hermaphroditism, S. ramosa still reflects the basic anomalodesmatan plan and such modifications as there are from the clavagellid form relate principally to the structure, formation and thus functioning of the adventitious tube. This study of S. ramosa has allowed the full spectrum of clavagellid adaptive radiation to be analysed and an evolutionary picture created which suggests that species of Clavagella/Dacosta and Stirpulina are Mesozoic (Late Cretaceous) remnants. Conversely, species of Bryopa and Dianadema are more modern, Late Oligocene and Palaeocene (Cenozoic), respectively, and possibly evolved in association with the emergence of the Indo-West Pacific centre of coral diversity, with a postulated average age of just 30 Myr. © 2013 The Linnean Society of London

Bioturbation determines the response of benthic ammonia-oxidizing microorganisms to ocean acidification

Ocean acidification (OA), caused by the dissolution of increasing concentrations of atmospheric carbon dioxide (CO2) in seawater, is projected to cause significant changes to marine ecology and biogeochemistry. Potential impacts on the microbially driven cycling of nitrogen are of particular concern. Specifically, under seawater pH levels approximating future OA scenarios, rates of ammonia oxidation (the rate-limiting first step of the nitrification pathway) have been shown to dramatically decrease in seawater, but not in underlying sediments. However, no prior study has considered the interactive effects of microbial ammonia oxidation and macrofaunal bioturbation activity, which can enhance nitrogen transformation rates. Using experimental mesocosms, we investigated the responses to OA of ammonia oxidizing microorganisms inhabiting surface sediments and sediments within burrow walls of the mud shrimp Upogebia deltaura. Seawater was acidified to one of four target pH values (pHT 7.90, 7.70, 7.35 and 6.80) in comparison with a control (pHT 8.10). At pHT 8.10, ammonia oxidation rates in burrow wall sediments were, on average, fivefold greater than in surface sediments. However, at all acidified pH values (pH ≤ 7.90), ammonia oxidation rates in burrow sediments were significantly inhibited (by 79-97%; p < 0.01), whereas rates in surface sediments were unaffected. Both bacterial and archaeal abundances increased significantly as pHT declined; by contrast, relative abundances of bacterial and archaeal ammonia oxidation (amoA) genes did not vary. This research suggests that OA could cause substantial reductions in total benthic ammonia oxidation rates in coastal bioturbated sediments, leading to corresponding changes in coupled nitrogen cycling between the benthic and pelagic realms.

Ocean acidification and climate change: advances in ecology and evolution

Atmospheric CO2 concentration [CO2] has increased from a pre-industrial level of approximately 280 ppm to approximately 385 ppm, with further increases (700–1000 ppm) anticipated by the end of the twenty-first century [[1][1]]. Over the past three decades, changes in [CO2] have increased global

Micro-scale dry bulk density variation around earthworm (Lumbricus terrestris L.) burrows based on X-ray computed tomography

The burrowing activity of earthworms leads to soil structural changes by compaction of surrounded soil matrix, which represents the so-called drilosphere. This is a distinct volume around the resulting macropore, which controls various soil processes. In the aim to detect the bulk density variation around earthworm burrows, two repacked soil columns from a silt loam with defined water content and bulk density were created, separately inoculated with the anecic earthworm species Lumbricus terrestris, stored under constant conditions for 7weeks and finally analyzed by means of X-ray computed tomography. A basic voxel approach was developed to conduct a gapless analysis of the drilosphere and surrounding soil matrix. The measured Hounsfield Units of basic voxels (pixel size of 0.25mm and slice thickness of 0.625mm) were converted into the corresponding dry bulk density (BD). The initial mean BD of an entire horizontal soil slice was 1.34Mgm−3 (core 1) and 1.38Mgm−3 (core 2). Due to burrowing L. terrestris compacted the inner boundary of the drilosphere (burrow wall) up to a BD of at least 1.75Mgm−3 which equates to more than 30% compared to the soil matrix. The BD decreased from the inner boundary of the drilosphere to its outer boundary, which is a transition zone to the surrounding soil matrix. However, the BD decrease was not concentrically uniform but revealed heterogeneous patterns of zones with different BD-classes. This locally heterogeneous BD distribution is an evidence of radial earthworm forces acting anisotropically. We conclude that BD heterogeneity in the drilosphere of L. terrestris might have notable implications for the understanding of lateral transfer of water and solutes in the soil profile.

Agricultural soil and drilosphere as reservoirs of new and unusual assimilators of 2,4‐dichlorophenol carbon

2,4-Dichlorophenol (2,4-DCP) is a potential soil and groundwater contaminant. Earthworms modulate growth and activities of soil microbiota. Thus, active 2,4-DCP degraders in agricultural soil and drilosphere (i.e. burrow walls, gut content and cast) were identified by comparative amplicon pyrosequencing-based 16S rRNA stable isotope probing in soil columns. In situ relevant concentrations of [U-(13) C]2,4-DCP were consumed in soil within 19 and 41 days in the presence and absence of the endogeic earthworm Aporrectodea caliginosa, respectively. [U-(14) C]2,4-DCP mineralization was higher in cast, burrow wall and soil from columns with than without earthworms. [U-(14) C]2,4-DCP mineralization was lowest in gut contents. Data indicated a strong impact of earthworms on the active microbial community. Novosphingobium, Comamonas and Desulfitobacterium sp. assimilated 2,4-DCP-[(13)C] in the absence of earthworms. Pseudomonas, Flavobacterium and Clostridium sp. assimilated 2,4-DCP-[(13)C] in the drilosphere. Novosphingobium- and Variovorax-related taxa dominated [U-(13)C]2,4-DCP consumers in soil slurries with drilosphere and bulk soil material. 16S rRNA sequences suggested species level novelty. The collective data demonstrates that new Bacteroidetes and Alphaproteobacteria/Betaproteobacteria were involved in 2,4-DCP-C transformation and indicated that diverse and hitherto unknown microbes associated with carbon flow from 2,4-DCP are shaped by earthworms.

Fiddler crab (Uca spp.) burrows have little effect on surrounding sediment oxygen concentrations

In the literature, it is commonly stated that Uca spp. (fiddler crab) burrows aerate marsh sediment. However, to date few studies have attempted to determine the pore water oxygen (O2) concentrations associated with Uca spp. burrows; instead most studies have looked at redox potential, a measure of oxidation and not of O2. In an in situ study conducted in salt marshes on the Atlantic coast of Virginia, USA, O2 concentrations surrounding individual burrows were measured to assess the potential of burrows to aerate bulk sediment. Using an O2 microelectrode, concentration profiles were measured at depth intervals of 500μm to a depth of 10mm. The O2 profiles were measured at distances of 2, 4, 6, 8, and 10mm from the burrow wall. Measurements were made surrounding natural and artificial burrows as well as where burrows were absent as a control.Contrary to convictions in the literature, this study determined that, within poorly drained muddy sediments, oxygen penetration depth only had a significant increase out to a distance of 2mm from the burrow wall, and the increase in oxygen depth penetration was only 0.5mm compared to areas not affected by the presence of the burrow. In typical muddy sediments of salt marshes along the mid-Atlantic coast, USA, the presence of Uca pugnax burrows increased the oxic zone little, but may have had an effect on the extent of the suboxic zone. Therefore, generalizations should not be made concerning the ability of burrows to aerate surrounding bulk sediments. In addition, the capacity of sediments to drain is an important factor in determining the potential for increased sediment aeration due to the presence of Uca spp. burrows.

The polychaete worm Nereis diversicolor increases mercury lability and methylation in intertidal mudflats

The polychaete worm Nereis diversicolor engineers its environment by creating oxygenated burrows in anoxic intertidal sediments. The authors carried out a laboratory microcosm experiment to test the impact of polychaete burrowing and feeding activity on the lability and methylation of mercury in sediments from the Bay of Fundy, Canada. The concentration of labile inorganic mercury and methylmercury in burrow walls was elevated compared to worm-free sediments. Mucus secretions and organic detritus in worm burrows increased labile mercury concentrations. Worms decreased sulfide concentrations, which increased Hg bioavailability to sulfate-reducing bacteria and increased methylmercury concentrations in burrow linings. Because the walls of polychaete burrows have a greater interaction with organisms, and the overlying water, the concentrations of mercury and methylmercury they contain is more toxicologically relevant to the base of a coastal food web than bulk samples. The authors recommend that researchers examining Hg in marine environments account for sediment dwelling invertebrate activity to more fully assess mercury bioavailability.

Consumers of 4-chloro-2-methylphenoxyacetic acid from agricultural soil and drilosphere harborcadA,r/sdpA, andtfdA-like gene encoding oxygenases

Microbial degradation of 2-methyl-4-chlorophenoxyacetic acid (MCPA) in soil is enhanced by earthworms and initiated by tfdA-like, cadA and r/sdpA gene encoding oxygenases. Copy numbers of such genes increased during MCPA degradation in soil, and MCPA stimulated transcription of tfdA-like and r/sdpA genes up to 4×. Transcription of cadA was detected in the presence of MCPA only. DNA stable isotope probing after consumption of 0.6-0.8mg 13C-MCPA gdw -1 in oxic microcosms indicated diverse labeled oxygenase genes in bulk soil, burrow walls, and cast. 9, 6, and 3 operational taxonomic units of tfdA-like, cadA, and r/sdpA genes, respectively, were labeled and affiliated with group 2 Alphaproteobacteria including Bradyrhizobia and group 1 class III Betaproteobacteria. New genes encoding putative MCPA degrading oxygenases were identified. Diversity of labeled OTUs tended to be lower for cast than for bulk soil. The collective data indicate (1) hitherto unknown active MCPA degraders and/or oxygenase genes in soil; (2) that multiple oxygenases are associated with MCPA degradation in soil at the same time; (3) that earthworms impact the capability of MCPA degraders in soil to respond to MCPA; and (4) the collective data enable a more in-depth analysis of MCPA degrader communities in soil by future structural gene-based experimental strategies.

Formation of methane-related authigenic carbonates within the bioturbated zone — An example from the upwelling area off Vietnam

In the biologically high-productive area off Vietnam authigenic carbonates formed in the bioturbated zone while methane was oxidized microbially under anaerobic conditions. Open crustacean burrows (Spongeliomorpha) connected to the seafloor acted as conduits for methane as suggested by intense cementation of burrow walls having a light C-isotope signature. Although seawater circulated within these open, inhabited tubes, conditions favorable for anaerobic oxidation of methane (AOM) occurred <1mm away from the tubes. Trace fossils document a gradual stiffening and induration of the material finally reaching hardground condition (indicated by Trypanites). Cementation started at several spots that coalesced later to form the nodule. Carbon isotopes indicate a biogenic methane source (δ13Ccarb reaching −49 to −40‰ V-PDB), while higher δ13C values imply mixing with carbon from other sources that is very likely within the bioturbated zone. The cement is generally fine grained (<5μm); calcite forms about 3/4 of the cement, dolomite about 1/4, and aragonite a minor proportion. High δ18O values of +5±1‰ reflect the general 18O-enriched isotope signature of the bottom water in South China Sea especially during glacial times, but influence of water released from decaying gas hydrate cannot be excluded. The studied nodule was found on top of a slump that displaced it.

Effects of the invasive polychaete Marenzelleria spp. on benthic processes and meiobenthos of a species-poor brackish system

The effects of the invasive polychaete Marenzelleria spp. on sediment processes and meiobenthos with an emphasis on free-living nematodes of the Vistula Lagoon (southern Baltic Sea) were investigated in a laboratory microcosm experiment. Marenzelleria occupies an open niche and its deep burying behaviour and feeding strategy represent a new function in the study area. Halos of oxidized sediment along Marenzelleria burrow walls indicated oxygen penetration into the burrows but the polychaete had no significant effect on porewater nutrient concentrations. The results showed, however, the density dependent effects of Marenzelleria on ammonium transport. An enhanced ammonium efflux was recorded at high polychaete densities (2000ind.m−2) but not at low polychaete densities (300ind.m−2).There was no observable impact of the polychaete on total meiobenthic numbers. There was, therefore, no indication that Marenzelleria caused meiofauna mortality. On the contrary, the polychaete significantly affected vertical distribution of meiofauna facilitating the colonization of deeper sediment depths and thus extending the habitat to be used by meiobenthos. In addition, Marenzelleria had a positive impact on the survival of turbellarians.Nevertheless, there was no effect of Marenzelleria on nematode assemblage structure and diversity, indicating that neither the physical presence nor the biological activity of the worm affected the nematode community. This suggests either 1. the limited impact of Marenzelleria on nematodes, resulting from the creation of simple, narrow and un-branched burrows, 2. poor response of nematode community resulting from their low abundance and diversity in the study area, or 3. the overriding role of the harsh chemical environment typical of sediments of the Vistula Lagoon, masking the effect of the bioturbator.

Influence of a burrowing, metal-tolerant polychaete on benthic metabolism, denitrification and nitrogen regeneration in contaminated estuarine sediments

We investigated the effects of the burrowing cirratulid polychaete Cirriformia filigera (Delle Chiaje, 1828) on benthic respiration and nitrogen regeneration in metal-contaminated estuarine sediments using laboratory mesocosms. C. filigera is a dominant component of assemblages in the most severely contaminated sediments within the Derwent estuary, southern Australia. In the presence of C. filigera sediment O2 consumption doubled, with approximately 55% of this increase due to their respiration and the remaining 45% attributable to oxidation reactions and increased microbial respiration associated with burrow walls. Combined NO3 and NO2 fluxes were unaffected. The addition of labile organic matter did not affect benthic fluxes, in the presence or absence of C. filigera, presumably due to the short timeframe of the experiment and naturally enriched test sediments. The results suggest that a combination of tolerance and burrowing activity enables this species to provide an ecosystem service in the removal of N from contaminated sites.

Effect of reoxygenation and Marenzelleria spp. bioturbation on Baltic Sea sediment metabolism

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 482:43-55 (2013) - DOI: https://doi.org/10.3354/meps10232 Effect of reoxygenation and Marenzelleria spp. bioturbation on Baltic Sea sediment metabolism S. Bonaglia1,*, M. Bartoli2, J. S. Gunnarsson3, L. Rahm4, C. Raymond3, O. Svensson3, S. Shakeri Yekta4, V. Brüchert1 1Department of Geological Sciences, and 3Department of Systems Ecology, Stockholm University, 10691 Stockholm, Sweden 2Department of Environmental Sciences, University of Parma, 43124 Parma, Italy 4Department of Thematic Studies—Water and Environment, Linköping University, 58183 Linköping, Sweden *Email: stefano.bonaglia@geo.su.se ABSTRACT: Nutrient reduction and the improvement of bottom water oxygen concentrations are thought to be key factors in the recovery of eutrophic aquatic ecosystems. The effects of reoxygenation and bioturbation of natural hypoxic sediments in the Baltic Sea were studied using a mesocosm experiment. Anoxic sediment box cores were collected from 100 m depth in Kanholmsfjärden (Stockholm Archipelago) and maintained in flow-through mesocosms with 3 treatments: (1) hypoxic: supplied with hypoxic water; (2) normoxic: supplied with oxic water; and (3) Marenzelleria: supplied with oxic water and the polychaete Marenzelleria spp. (2000 ind. m–2). After a 7 wk long conditioning period, net fluxes of dissolved O2, CH4, Fe2+, Mn2+, NH4+, NO2-, NO3-, PO43- and H4SiO4, and rates of nitrate ammonification (DNRA), denitrification and anammox were determined. Phosphate was taken up by the sediment in all treatments, and the uptake was highest in the normoxic treatment with Marenzelleria. Normoxic conditions stimulated the denitrification rate by a factor of 5. Denitrification efficiency was highest under normoxia (50%), intermediate in bioturbated sediments (16%), and very low in hypoxic sediments (4%). The shift from hypoxic to normoxic conditions resulted in a significantly higher retention of NH4+, H4SiO4 and Mn2+ in the sediment, but the bioturbation by Marenzelleria reversed this effect. Results from our study suggest that bioturbation by Marenzelleria stimulates the exchange of solutes between sediment and bottom water through irrigation and enhances bacterial sulfate reduction in the burrow walls. The latter may have a toxic effect on nitrifying bacteria, which, in turn, suppresses denitrification rates. KEY WORDS: Hypoxia · Macrofauna · Mesocosm · Denitrification · Dissimilatory nitrate reduction to ammonium · DNRA · Benthic Flux · Baltic Sea Full text in pdf format PreviousNextCite this article as: Bonaglia S, Bartoli M, Gunnarsson JS, Rahm L and others (2013) Effect of reoxygenation and Marenzelleria spp. bioturbation on Baltic Sea sediment metabolism. Mar Ecol Prog Ser 482:43-55. https://doi.org/10.3354/meps10232 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 482. Online publication date: May 22, 2013 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2013 Inter-Research.

The Recognition of Ophiomorpha irregulaire on the Basis of Pellet Morphology: Restudy of Material from the Type Locality

Serial grinding of a specimen of Ophiomorpha irregulaire collected from Coal Creek Canyon in the Book Cliffs of Utah, USA—the type locality of the ichnospecies—allows us to assess the validity of pellet morphology as an ichnotaxobase for species-level identification. The importance of O. irregulaire stems from its abundance in petroliferous shallow marine strata of post-Paleozoic age. Our three-dimensional reconstruction of the burrow wall of O. irregulaire demonstrates for the first time that it is composed of sand-cored pellets. The typically spiky nature of the pellets in cross-section is inferred to result from differential compaction of the sand core and pelletal lining. Rupturing of the thin outer clay coating of the sand pellets is considered to produce the distinctively attenuated, spiky outer surface to the burrow wall of this ichnospecies. This study demonstrates the utility of pellet morphology in species-level classification of Ophiomorpha and lends support to O. irregulaire being a cosmopolitan ichnospecies present in post-Paleozoic strata. It also demonstrates the need to ensure that ichnotaxonomic identifications are based on three-dimensional knowledge of the trace fossil in question.

Alteration ofChironomus plumosusventilation activity and bioirrigation-mediated benthic fluxes by changes in temperature, oxygen concentration, and seasonal variations

Abstract. Burrowing benthic organisms promote water and solute fluxes across the sediment–water interface. Water and solutes penetrate the burrow walls and are transported into/out of the sediment when organisms flush their burrows with overlying water. Few studies have been done to investigate bioirrigation under shifting environmental conditions. We experimentally quantified bioirrigation by Chironomus plumosus larvae in the laboratory at 3 ranges of O2 saturation (low, medium, and high O2 concentrations), 2 temperatures (10 and 20°C), and over different seasons. We measured ventilation activities with O2 and flow-velocity microsensors, flow velocities during pumping periods with color tracers, pumping rates with conductivity exchange experiments, and rates of advective and diffusive water influx into the sediment by influx assays (NaCl was the tracer in both latter experiments). O2 saturations <12% extended pumping durations/h, whereas saturations <3% decreased pumping durations to ∼0. Flow velocities...

Preliminary Data on the Bioturbation Activity of Hediste Diversicolor (Polychaeta, Nereididae) from the Loire Estuary, France

The ragworm Hediste diversicolor (O. F. Muller, 1776) plays a key role in the estuarine water-sediment interface. This scientific project comes under the framework of the International network Nereis Park Experiment gathering 27 laboratories from all over the world. The experiments were carried out concurrently in spring 2007 using a common protocol. In the Loire estuary, the samples were collected in the intertidal zone of the Saint-Nazaire Bridge. During the field experiment, we estimated the surface area of the burrow walls (Sb) value varied from Sb = 0.26 m2.m-2 to 2.18 m2.m-2 (mean Sb = 0.75 m2.m-2), and the pumping rate (Pr) value from Pr = 0.9 l.d-1m-2 to 7.7 l.d-1 m-2 (mean value Pr = 2.7 l.d-1m-2). The density and the biomass of H. diversicolor populations largely controlled the amount of reworked sediment. In the laboratory, we estimated the pseudo-diffusive mixing, Db value varied from Db = 1.2 to 1.6 (mean Db = 1.5). The non-local transport (r) from the upper layers to the bottom of the tubes varied from r = 1 to 7.2 (mean r = 4.3). A positive relationship could be established between Db and the temperature while on the contrary a negative relationship could be established between the Db and biomass. It seems that small individuals are more efficient reworkers than big ones.

A combined sensor for simultaneous high resolution 2‐D imaging of oxygen and trace metals fluxes

A new sandwich sensor, consisting of an O2 planar optode overlain by a thin (90 µm) DGT layer is presented. This sensor can simultaneously resolve 2‐D O2 dynamics and trace metal fluxes in benthic substrates at a high spatial resolution. The DGT layer accumulates metals on a small particle size (0.2 µm) chelating resin and records the locally induced trace metal flux during the deployment, whereas the planar optode resolves the O2 dynamic in near real time at the same location in the sediment. Despite its ultrathin composition, the DGT layer has high carrying capacity for trace metals with no saturation problems during application to typical coastal‐ or contaminated sediments. Combined with laser ablation, accumulated metal fluxes could be resolved at a resolution of ~200 µm, whereas the O2 images had a resolution of ~100 µm. A 2‐D diffusion‐reaction model showed that the enhanced smearing and reduced response time of the O2 signal associated with the additional DGT layer were marginal. To test sensor performance at realistic conditions, it was applied to an artificial burrow system consisting of permeable dialysis tubing flushed with oxygenated seawater. The measurements demonstrated localized mobilization of Ni, Cu, and Pb close to the burrow wall, where O2 was elevated. The latter was also confirmed for Cu and Pb in natural sediments irrigated by the polychaete Hediste diversicolor. The sandwich sensor has great potential for investigating interrelations between O2 dynamics and metal mobilization in complex benthic systems such as burrows, rhizospheres, permeable sands, and microbial mats.