Ichnofossils are well developed in clastic rock reservoirs in marine and transitional facies, which can considerably change the physical properties of the reservoir. However, this influence is not well understood, rai...Ichnofossils are well developed in clastic rock reservoirs in marine and transitional facies, which can considerably change the physical properties of the reservoir. However, this influence is not well understood, raising an important problem in the effective development of petroleum reservoirs. This paper analyzes continental shelf margin delta reservoirs through core observation, cast thin section observation and reservoir physical property test. Some important scientific insights are obtained:(1) The presence of Cruziana ichnofacies, including Asterosoma, Ophiomorpha, Planolites, Skolithos, Thalassinoides, and other ichnofossils can be used to identify in subaqueous distributary channels, subaqueous levee, frontal sheet sand, abandoned river channels, crevasse channels, main channels and channel mouth bars. Considerable differences in the types of ichnofossils and the degree of bioturbation can be observed in the different petrofacies.(2) Ichnofossils and bioturbation play a complex role in controlling reservoir properties. The reservoir physical properties have the characteristics of a decrease–increase–decrease curve with increasing bioturbation degree. This complex change is controlled by the sediment mixing and packing of bioturbation and the diagenetic environment controlled by the ichnofossils.(3) Sea-level cycle changes affect the modification of the reservoir through sediment packing. Bioturbation weakens the reservoir's physical property when sea level slowly rises and improves the reservoir's physical property when base level slowly falls.展开更多
Filter-feeding shellfish are common benthos and significantly affect the biogeochemical cycle in the shallow coastal ecosystems.Ark clam Scapharca subcrenata is one of the widely cultured bivalve species in many coast...Filter-feeding shellfish are common benthos and significantly affect the biogeochemical cycle in the shallow coastal ecosystems.Ark clam Scapharca subcrenata is one of the widely cultured bivalve species in many coastal areas owing to its tremendous economic value.However,there is little information regarding the effects of the bioturbation of S.subcrenata on the fluxes of nutrient exchange in the sediment-water interface(SWI).In this regard,S.subcrenata was sampled during October 2016 to determine the effects of its bioturbation activity on the nutrient exchange flux of the SWI.The results showed that the biological activity of S.subcrenata could increase the diffusion depth and the rate of the nutrients exchange in the sediments.The bioturbation of S.subcrenata could allow the nutrients to permeate into the surface sediments at 6-10cm and increase the release rate of nutrients at the SWI.The releasing fluxes of DIN and PO43−-P in the culture area were found to be around three times higher than that in the non-cultured region.The culture of S.subcrenata has been proved to be an important contributor to nutrient exchange across the SWI in the farming area of Haizhou Bay.Nutrients exchange in the SWI contributes a part of 86%DIN,71%PO43−-P and 18%SiO32−-Si for the aquaculture farm.展开更多
Trace fossils were discovered in the Middle Ordovician Badou Member of Fengfeng Formation and the Member 1 of Jinsushan Formation in Mt. Jinsu of the Fuping region which lies at the southeastern margin of the Ordos ba...Trace fossils were discovered in the Middle Ordovician Badou Member of Fengfeng Formation and the Member 1 of Jinsushan Formation in Mt. Jinsu of the Fuping region which lies at the southeastern margin of the Ordos basin. The rocks of the fore-mentioned parts contain a considerable amount of bioturbation structures, in which ichnogenus and ichnospecies can not be identified, and abundant stromatolites.The distributions and characteristics of the bioturbation structures are analyzed and summarized in this paper. The paleoenvironments of related formations and members were interpreted in the method of semiquantitative analysis of bioturbation structures with researches on stromatolites and sedimentology. It is suggested that Fuping zone, located in the southeastern margin of the Ordos basin, was a carbonate platform where stromatolite-developing tidal flat and low-energy subtidal open platform environments dominated. Also that this zone experienced three paleogeographic evolutions from tidal flat to low-energy subtidal open platform environments, that is, three larger-scale eustatisms occurred during the sedimentary period of Middle Ordovician Badou Member of Fengfeng Formation to the Member 1 of Jinsushan Formation.展开更多
The transformation mechanism of muddy carbonate rock by the coupling of bioturbation and diagenesis was stud-ied based on core,cast thin section and physical property data of Cretaceous strata in the Mesopotamia Basin...The transformation mechanism of muddy carbonate rock by the coupling of bioturbation and diagenesis was stud-ied based on core,cast thin section and physical property data of Cretaceous strata in the Mesopotamia Basin,the Middle East.There are 3 ways of biological transformation of rocks:(1)The living creatures transformed formations mechanically to make the rocks looser and intergranular pores increase.(2)After formation,burrows were backfilled with coarse-grained debris,and then unsaturated fluid infiltrated into the burrows during the penecontemporaneous period,resulting in dissolution.(3)Chemical alteration occurred in abandoned burrows and dolomitization produced a large number of intercrystalline pores.The·coupling of bioturbation and dissolution occurred mainly in the penecontemporaneous phase,and was controlled by rock type,sea level decline,burrow abundance,infillings,and water environment etc.As the burrows had better physical properties than the matrix,unsaturated fluid preferentially migrated along the burrows,leading to dissolution and expansion of the burrows first and then dissolution of the matrix.The coupling of bioturbation and dolomitization occurred mainly in the burial phase.The rich organic matter and reducing bacteria in the burrow provided material basis,reducing conditions and alkaline envi-ronment for dolomitization.The metasomatism in the penecontemporaneous period had little effect on the physical properties of the burrows.When the burrows were se parated from the deposition interface,equimolar metasomatism occurred in the burrows in a closed environment,forming euhedral fine-crystalline dolomite with intercrystalline pores.The transformation degree of bioturbation to muddy carbonate reservoir depends on rock type,density,connectivity,infillings and structure of the burrows.With the increase of the carbonate mud content,the im provement to rock physical properties by bioturbation be-comes more prominent.When the burrows are filled with coarse-grained debris or fine-crystalline dolomite,the greater the density,the higher the connectivity,and the lower the tortuosity of burrows,the better the physical properties of the muddy carbonate rocks are.展开更多
As an important factor influencing the physical,chemical and biological processes of sediments,the bioturbation of macrobenthos has received extensive attention in the study of the biogeochemical processes of sediment...As an important factor influencing the physical,chemical and biological processes of sediments,the bioturbation of macrobenthos has received extensive attention in the study of the biogeochemical processes of sediments.However,previous studies provided limited scope for the effects of the bioturbation on the biogeochemical processes of sediments.Based on the analysis of recently published data,this paper presented an integrated overview to summarize the forms of bioturbation (rework,bioirrigation,biodeposition,bioresuspension,biodiffusion),and the effects of bioturbation on the organic matter decomposition,microorganisms,and nutrient flux at the sediment-water interface.To better understand the impacts of bioturbation on biogeochemical processes of sediments,the research should be strengthened in the following aspects in the future: the combination of field experiment and lab simulation test should be strengthened as for the research method;much more attention should be paid to the other sea areas besides hot sea areas and different ecosystems regarding the research area;and the biogenic elements except nitrogen and phosphorus,microorganisms,and heavy metals should be deepened regarding the research content.展开更多
In the Elkhorn River,burrows,tubes,and sediment mounds created by invertebrate bioturbation were observed in the exposed streambed and commonly concentrated on the fine-sediment patches,which consist of silt,clay,and ...In the Elkhorn River,burrows,tubes,and sediment mounds created by invertebrate bioturbation were observed in the exposed streambed and commonly concentrated on the fine-sediment patches,which consist of silt,clay,and organic matter.These invertebrate activities could loosen the thin layer of clogging sediments and result in an increase of pore size in the sediments,leading to greater vertical hydraulic conductivity of the streambed(Kv).The measurements of the vertical hydraulic gradient across the submerged streambed show that vertical flux in the hyporheic zone can alter directions(upward versus downward)for two locations only a few meters apart.In situ permeameter tests show that streambed Kv in the upper sediment layer is much higher than that in the lower sediment layer,and the calculated Kv in the submerged streambed is consistently greater than that in the clogged sediments around the shorelines of the sand bars.Moreover,a phenomenon of gas bubble release at the water-sediment interface from the subsurface sediments was observed in the groundwater seepage zone where flow velocity is extremely small.The bursting of gas bubbles can potentially break the thin clogging layer of sediments and enhance the vertical hydraulic conductivity of the streambed.展开更多
Bioturbation plays an important role in enhancing the reservoir capacity of tight reservoirs.This study aims to understand the alteration mechanism and effects of bioturbation on oil and gas reservoirs,to clarify the ...Bioturbation plays an important role in enhancing the reservoir capacity of tight reservoirs.This study aims to understand the alteration mechanism and effects of bioturbation on oil and gas reservoirs,to clarify the key control factors and constraints influencing the production of bioturbation.The petrophysical characteristics of bioturbation and host sediments in carbonate rocks,such as mineral composition,pore spaces,porosity and permeability,were studied based on the detailed observation and description of the Ordovician cores from the Tahe oilfield.The effect of bioturbation on petrophysical properties of carbonate rocks were carefully analyzed.The results show:(1)Two types of bioturbation,Thalassinoides-like burrows and Planolites-like burrows,mainly occur in the Ordovician cores of the Tahe oilfield,ranging from the Lower-Middle Ordovician Yingshan Formation to the Middle Ordovician Yijianfang Formation.The burrow-fills are mainly composed of dolomite with subhedral and euhedral crystals.The host sediments mainly consist of micrite.(2)The pores in the host sediments are poorly developed and are incapable of forming effective reservoir spaces.However,well-developed intercrystalline pores among dolomites and microfractures in bioturbated sediments with better connectivity can form effective pore spaces.The results of porosity and permeability show that the host sediments without bioturbation are characterized by poor porosity and permeability.However,with the increase of bioturbation intensity,the porosity of the bioturbated sediments firstly increases and then decreases,whereas the permeability increases all the time.(3)Multiple burrows overprinted in the Ordovician carbonate rocks,forming a large-scale bioturbated carbonate rocks with lateral continuity and vertical connectivity,due to the suitable sedimentary setting,ecological conditions,favorable spatiotemporal sediment matching,and abundant organism-substrate interaction.Subsequently,diagenesis(particularly dolomitization and dissolution)has played a positive role in altering the rock fabric and improving the petrophysical properties of bioturbated carbonates.展开更多
Organic matter(OM) is an important component of sediment. Bioturbation/bioirrigation can remobilize OM and heavy metals that were previously buried in the sediment. The remobilization of buried organic matter, thalliu...Organic matter(OM) is an important component of sediment. Bioturbation/bioirrigation can remobilize OM and heavy metals that were previously buried in the sediment. The remobilization of buried organic matter, thallium(Tl), cadmium(Cd), copper(Cu) and zinc(Zn) from sediment was studied in a laboratory experiment with three organisms: tubificid,chironomid larvae and loach. Results showed that bioturbation/bioirrigation promoted the release of dissolved organic matter(DOM) and dissolved Tl, Cd, Cu and Zn, but only dissolved Zn concentrations decreased with exposure time in overlying water. The presence of organisms altered the compositions of DOM released from sediment,considerably increasing the percentage of fulvic acid-like materials(FA) and humic acidlike materials(HA). In addition, bioturbation/bioirrigation accelerated the growth and reproduction of bacteria to enhance the proportion of soluble microbial byproduct-like materials(SMP). The DOM was divided into five regions in the three-dimensional excitation emission matrix(3 D-EEM), and each part had different correlation with the dissolved heavy metal concentrations. Dissolved Cu had the best correlation with each of the DOM compositions, indicating that Cu in the sediment was in the organic-bound form.Furthermore, the organism type and heavy metal characteristics both played a role in influencing the remobilization of heavy metal.展开更多
[Objective] The purpose of this study was to investigate the role of breeding Misgurnus anguillicaudatus in paddy field in vertical distribution of sediment particles. [Method] Using chemically stable glass beads as t...[Objective] The purpose of this study was to investigate the role of breeding Misgurnus anguillicaudatus in paddy field in vertical distribution of sediment particles. [Method] Using chemically stable glass beads as tracers, the effects of Misgurnus anguillicaudatus bioturbation on the vertical distribution of sediment particles in paddy field were investigated, and the bioturbation role of benthic fish in the coupling process of benthic-pelagic interface was discussed. [Result] After ten days of Misgurnus anguillicaudatus bioturbation, 43.2% of the glass beads on the surface were transferred downwardly with the maximum distance of 7.5 cm, and the vertical transportation rate of sediment particles was 7.676×10-4g-1·cm-2·d-1. At a depth of 6 cm, 39.7% and 9.9% of the glass beads were respectively transferred upwards and downwards, to the maximum distanc of 4.5 cm and 5.1 cm, respectively; and the vertical transportation rates of sediment particles were 7.597×10-4g-1·cm-2·d-1 and 1.894×10-4g-1·cm-2·d-1, respectively. [Conclusion] Misgurnus anguillicaudatus bioturbation could promote the circulation and transformation of nutrients at water/soil interface through affecting the vertical distribution of sediment particles.展开更多
The relationships between nutrient dynamics,microbial community,and macrofauna are important in bioremediation systems.In this study,we examined the effects of marine clam Scapharca subcrenata sedimentary activities o...The relationships between nutrient dynamics,microbial community,and macrofauna are important in bioremediation systems.In this study,we examined the effects of marine clam Scapharca subcrenata sedimentary activities on the microbial assemblages,benthic nutrient chemistry,and its subsequent remediation impacts on organic effluent in the sediment of an aquaculture wastewater bioremediation system.The results showed that microbial community composition differed significantly in the clam area(ANOSIM,R=0.707,P=0.037).Pyrosequencing of bacterial 16S rRNA gene revealed a total of 48 unique phyla,79 classes,107 orders,197 families,and 321 genera amongst all samples.The most dominant bacterial assemblages were Proteobacteria,Bacteroidetes,Acidobacteria,Firmicutes,Verrucomicrobia,and Actinobacteria,with Bacteroidetes and Firmicutes significantly higher in all treatment samples than control(P<0.001).All dominant phyla in the list were shared across all samples and accounted for 89%(control)and 97%(treatment)of the total 16S rRNA.The nutrient flux rates from the sediments into the water(treatment group)were 51%(ammonium),88%(nitrate),77%(nitrite)and 45%(phosphate)higher,relative to the control implying increased mineralization,degradability,and mobility of the benthic nutrients.Similarly,significantly increased oxygen consumption rates were evident in the clam area signifying improved oxygen distribution within the sediment.The organic effluent contents associated with total-organic matter,carbon,nitrogen,and,phosphate were lower among the clam treatments relative to the control.Our results describe the potential roles and mechanisms contributed by marine bivalve S.subcrenata on benthic-bacterial-community assembly,nutrient balance,and effluent reduction in the sediments of aquaculture wastewaters bioremediation system.展开更多
This study investigated the change in denitrification rate in muddy tidal flats sediment by chemical and biological remediation. Column experiments were conducted to determine the dependence of denitrification rate on...This study investigated the change in denitrification rate in muddy tidal flats sediment by chemical and biological remediation. Column experiments were conducted to determine the dependence of denitrification rate on the redox potential. Filtered seawater was fed continuously to the pipe filled with sediment from the muddy tidal flats. An increase in the redox potential from -198 mV to 21 mV with bioturbation led to increases in the denitrification rate from 24.2 mg/m2/day to 29.8 mg/m2/day. The increase in denitrification was explained by the acceleration of mass transfer in the sediment. Redox-potential increased from -400 mV to -200 mV by the addition of 10 g calcium nitrate, acid volatile sulfide was below the detection limit to 20 cm depth, and denitrification rate was increased from 21.3 mg/m2/day to 36.4 mg/m2/day. It is considered that the increased nitrogen concentration led to an increase in microbial activity.展开更多
Since the mud snail Bullacta exarata was introduced for economic aquaculture in the Huanghe River(Yellow River) Delta in 2001, its quick population growth and expanded distribution make it a key-species in the interti...Since the mud snail Bullacta exarata was introduced for economic aquaculture in the Huanghe River(Yellow River) Delta in 2001, its quick population growth and expanded distribution make it a key-species in the intertidal zone of this area. This significantly contributed to the economic income of the local people, but its potential ecological impact on the benthic ecosystem remains unknown. A mesocosm study was conducted to test whether its bioturbation activities affect the microphytobenthos(MPBs;i.e., sedimentary microbes and unicellular algae)productivity and the nutrient exchange between the sediment-water interface. Our results show that the mud snail significantly impacted the dissolved oxygen(DO) flux across the sediment-water interface on the condition of normal sediment and light treatment, and significantly increased the ammonium efflux during recovery period in the defaunated sediment and dark treatment. The presence of micro-and meiofauna significantly increased the NH4-N flux in dark treatment. Whereas, in light treatment, these small animals had less effects on the DO and NH4-N flux between sediment-water interface. Our results provide better insight into the effect of the mud snail B.exarata on the ecosystem functioning via benthic fluxes.展开更多
The contribution of benthic foraminifera to sediment bioturbation has widely been overlooked despite their huge abundance in intertidal soft sediments. In this preliminary study, we specifically chose to focus on two ...The contribution of benthic foraminifera to sediment bioturbation has widely been overlooked despite their huge abundance in intertidal soft sediments. In this preliminary study, we specifically chose to focus on two key species of benthic foraminifera in temperate intertidal mudflats, <i><span style="font-size:12px;font-family:Verdana;">Quinqueloculina seminula</span></i><span style="font-size:12px;font-family:Verdana;"> and </span><i><span style="font-size:12px;font-family:Verdana;">Ammonia</span></i> <i><span style="font-size:12px;font-family:Verdana;">tepida</span></i><span style="font-size:12px;font-family:Verdana;">, and first experimentally investigated their individual movements at the sediment surface. We subsequently derived from these observations the individual-level surface sediment reworking rates, and used the actual abundance of these species to extrapolate these rates at the population level. Individual surface sediment reworking rates </span><i><span style="font-size:12px;font-family:Verdana;">SSRR</span><sub><span style="font-size:12px;font-family:Verdana;">i</span></sub></i><span style="font-size:12px;font-family:Verdana;"> ranged between 0.13 and 0.32 cm<sup>2</sup><span style="white-space:nowrap;">·</span></span><span style="font-size:12px;"><sup><span style="font-family:Verdana;"></span></sup></span><span style="font-size:12px;font-family:Verdana;">ind</span><span style="font-family:Verdana;font-size:8.33333px;"><sup>-1</sup><span style="white-space:nowrap;">·</span></span><span style="font-size:12px;font-family:Verdana;">day<sup>-1</sup></span> <span style="font-size:12px;font-family:Verdana;">for</span><span style="font-size:10pt;font-family:;" "=""> <i><span style="font-size:12px;font-family:Verdana;">Q. seminula</span></i><span style="font-size:12px;font-family:Verdana;">, and between 0.12 and 0.28 cm<sup>2</sup><span style="white-space:nowrap;">·</span></span><span style="font-size:12px;font-family:Verdana;">ind<sup>-1</sup><span style="white-space:nowrap;">·</span></span><span style="font-size:12px;font-family:Verdana;">day<sup>-1</sup></span><span style="font-size:12px;font-family:Verdana;"> for </span><i><span style="font-size:12px;font-family:Verdana;">A. tepida</span></i><span style="font-size:12px;font-family:Verdana;">. Population-level surface sediment reworking rates were subsequently estimated as ranging between 11,484 and 28,710 cm<sup>2</sup><span style="white-space:nowrap;">·</span></span><span style="font-size:12px;font-family:Verdana;">m<sup>-2</sup><span style="white-space:nowrap;">·</span></span><span style="font-size:12px;font-family:Verdana;">day<sup>-1</sup></span><span style="font-size:12px;font-family:Verdana;"> for </span><i><span style="font-size:12px;font-family:Verdana;">Q. seminula</span></i><span style="font-size:12px;font-family:Verdana;"> and 27,876 and 65,044 cm<sup>2</sup><span style="white-space:nowrap;">·</span></span><span style="font-size:12px;font-family:Verdana;">m<sup>-2</sup><span style="white-space:nowrap;">·</span></span><span style="font-size:12px;font-family:Verdana;">day<sup>-1</sup></span><span style="font-size:12px;font-family:Verdana;"> for </span><i><span style="font-size:12px;font-family:Verdana;">A. tepida</span></i><span style="font-size:12px;font-family:Verdana;">. Noticeably, these reworking rates are comparable to, and eventually even higher than, the rates reported in the literature for populations of intertidal macro-invertebrates, such as the annelid polychaete </span><i><span style="font-size:12px;font-family:Verdana;">Melinna palmata</span></i><span style="font-size:12px;font-family:Verdana;"> and the bivalve </span><i><span style="font-size:12px;font-family:Verdana;">Abra</span></i> <i><span style="font-size:12px;font-family:Verdana;">ovata</span></i><span style="font-size:12px;font-family:Verdana;">. Taken together these results suggest that despite their minute size intertidal benthic foraminifera are, thanks to their abundance, non-negligible contributors to the reworking of surface sediment, and may then play an unanticipated role in the benthic ecosystem functioning, through e.g. the enhancement of fluxes at the sediment-water interface.</span></span>展开更多
Six ichnogenera,Chondrites,Palaeophycus,Planolites,Rhizocorallium,Skolithos,and Thalassinoides,were identified from the drilling cores near the Global Stratotype Section and Point(GSSP) of Permian-Triassic boundary at...Six ichnogenera,Chondrites,Palaeophycus,Planolites,Rhizocorallium,Skolithos,and Thalassinoides,were identified from the drilling cores near the Global Stratotype Section and Point(GSSP) of Permian-Triassic boundary at Meishan,Zhejiang Province.The ichnological indices,including abundance,bioturbation index,and disturbed depth of trace fossils,show two episodes of intense changes near the Permian-Triassic Boundary(PTB).Episode I occurred in Beds 25-27b when the ecologically complicate forms such as Chondrites,Skolithos,Rhizocorallium,and Thalassinoides disappeared hereafter,the bioturbation index reduced from 1-5 to 1-3,and the disturbed depth declined from 5-66 to 2-5 cm.Episode II took place at the base of Bed 33 with the disappearance of Palaeophycus and Planolites,and subsequent absence of trace fossils and bioturbation till the middle-upper part of Bed 41 when the disturbed structures reoccurred,but they are only tiny Planolites and the bioturbation index was never higher than 3 and the disturbed depth less than 4 mm.Episode I shows an intense change,corresponding to the main stage of the end-Permian mass extinction,whereas Episode II is relatively weak,corresponding to the epilogue of the mass extinction of trace makers in the Early Triassic.Subsequently,ichnofossils were dominated by surface tracks in simple ecological habit and structures.This phenomenon indicates that the Early Triassic benthonic fauna is changed from sessile benthic system to mobile benthic system after the end-Permian mass extinction.In other words,the evolution of the trace fossils across the Permian-Triassic transition had an episodic process similar to the body fossils.In addition,the change of ichnofabrics is well coincided with the negative excursion of carbon isotopes and the expansion of cyanobacteria.As the results of physical and biogenic processes,trace fossils provided unique materials for the study of the biotic and environmental events,as well as their coupling evolution through the great Permian-Triassic transition.展开更多
The continuous excavation of burrows by fiddler crabs generates bioturbation in the sediment,which can be estimated from burrow morphology.The aim of the present study was to describe the burrow morphology of Uca urug...The continuous excavation of burrows by fiddler crabs generates bioturbation in the sediment,which can be estimated from burrow morphology.The aim of the present study was to describe the burrow morphology of Uca uruguayensis and U.leptodactylus and its relationship with demography of resident individuals and to estimate the level of bioturbation in the sediment generated by each species.For all individuals from each of the 2 species,sex was determined and the carapace width(CW;mm)measured.Burrows were characterized according to burrow diameter(BD;mm),maximum burrow depth(MBD;mm)and burrow volume(BV;cm^(3)).The density of each species in the study area was also evaluated.In both species,the males were larger and occupied burrows with higher BV compared to females.Differences between sexes in relation to the burrow characteristics might reflect sexual dimorphism within the group and are probably related to the fact that males use the burrows for mating.BD and BV showed significant positive relationships with the size of resident crabs.The amount of sediment removed per burrow was estimated from mean BV:10.78 cm^(3)of sediment/burrow for U.uruguayensis and 12.38 cm^(3)of sediment/burrow for U.leptodactylus.Despite the density and depth differences between the 2 species,the similarity in burrow volume suggests that U.uruguayensis and U.leptodactylus present the same importance in terms of the bioturbation process.Burrow morphology is highly associated with characteristics of the occupant,although extrinsic factors should also be considered,and its description can provide estimates on the bioturbation generated by Uca species in mangrove forests.展开更多
基金The National Natural Science Foundation of China under contract Nos 41872112 and 42077410the Key Research Project of Higher Education Institutions in Henan University under contract No. 20A170010+1 种基金the Program for Innovative Research Team (in Science and Technology) of Henan Polytechnic University under contract No. T2022-05the Foundation of Shandong Provincial Key Laboratory of Depositional Mineralization and Sedimentary Mineral under contract No. DMSM2018027。
文摘Ichnofossils are well developed in clastic rock reservoirs in marine and transitional facies, which can considerably change the physical properties of the reservoir. However, this influence is not well understood, raising an important problem in the effective development of petroleum reservoirs. This paper analyzes continental shelf margin delta reservoirs through core observation, cast thin section observation and reservoir physical property test. Some important scientific insights are obtained:(1) The presence of Cruziana ichnofacies, including Asterosoma, Ophiomorpha, Planolites, Skolithos, Thalassinoides, and other ichnofossils can be used to identify in subaqueous distributary channels, subaqueous levee, frontal sheet sand, abandoned river channels, crevasse channels, main channels and channel mouth bars. Considerable differences in the types of ichnofossils and the degree of bioturbation can be observed in the different petrofacies.(2) Ichnofossils and bioturbation play a complex role in controlling reservoir properties. The reservoir physical properties have the characteristics of a decrease–increase–decrease curve with increasing bioturbation degree. This complex change is controlled by the sediment mixing and packing of bioturbation and the diagenetic environment controlled by the ichnofossils.(3) Sea-level cycle changes affect the modification of the reservoir through sediment packing. Bioturbation weakens the reservoir's physical property when sea level slowly rises and improves the reservoir's physical property when base level slowly falls.
基金supported by the Young Orient Scholars Programme of Shanghaithe Doctoral Scientific Research Starting Foundation of Shanghai Ocean University+2 种基金the Shanghai Special Research Fund for Training College’s Young Teachersthe Fund for Ministry of Agriculture Readjusting the Industrial Structure: Sea Farming Demonstration Project of Haizhou Bay in Jiangsu Province (Nos. D-8006-12-0018, D8006-15-8014)the Special Fund for Agro-Scientific Research in the Public Interest (No. 201303047)
文摘Filter-feeding shellfish are common benthos and significantly affect the biogeochemical cycle in the shallow coastal ecosystems.Ark clam Scapharca subcrenata is one of the widely cultured bivalve species in many coastal areas owing to its tremendous economic value.However,there is little information regarding the effects of the bioturbation of S.subcrenata on the fluxes of nutrient exchange in the sediment-water interface(SWI).In this regard,S.subcrenata was sampled during October 2016 to determine the effects of its bioturbation activity on the nutrient exchange flux of the SWI.The results showed that the biological activity of S.subcrenata could increase the diffusion depth and the rate of the nutrients exchange in the sediments.The bioturbation of S.subcrenata could allow the nutrients to permeate into the surface sediments at 6-10cm and increase the release rate of nutrients at the SWI.The releasing fluxes of DIN and PO43−-P in the culture area were found to be around three times higher than that in the non-cultured region.The culture of S.subcrenata has been proved to be an important contributor to nutrient exchange across the SWI in the farming area of Haizhou Bay.Nutrients exchange in the SWI contributes a part of 86%DIN,71%PO43−-P and 18%SiO32−-Si for the aquaculture farm.
文摘Trace fossils were discovered in the Middle Ordovician Badou Member of Fengfeng Formation and the Member 1 of Jinsushan Formation in Mt. Jinsu of the Fuping region which lies at the southeastern margin of the Ordos basin. The rocks of the fore-mentioned parts contain a considerable amount of bioturbation structures, in which ichnogenus and ichnospecies can not be identified, and abundant stromatolites.The distributions and characteristics of the bioturbation structures are analyzed and summarized in this paper. The paleoenvironments of related formations and members were interpreted in the method of semiquantitative analysis of bioturbation structures with researches on stromatolites and sedimentology. It is suggested that Fuping zone, located in the southeastern margin of the Ordos basin, was a carbonate platform where stromatolite-developing tidal flat and low-energy subtidal open platform environments dominated. Also that this zone experienced three paleogeographic evolutions from tidal flat to low-energy subtidal open platform environments, that is, three larger-scale eustatisms occurred during the sedimentary period of Middle Ordovician Badou Member of Fengfeng Formation to the Member 1 of Jinsushan Formation.
基金Supported by the China National Science and Technology Major Project(2017ZX05030-001)。
文摘The transformation mechanism of muddy carbonate rock by the coupling of bioturbation and diagenesis was stud-ied based on core,cast thin section and physical property data of Cretaceous strata in the Mesopotamia Basin,the Middle East.There are 3 ways of biological transformation of rocks:(1)The living creatures transformed formations mechanically to make the rocks looser and intergranular pores increase.(2)After formation,burrows were backfilled with coarse-grained debris,and then unsaturated fluid infiltrated into the burrows during the penecontemporaneous period,resulting in dissolution.(3)Chemical alteration occurred in abandoned burrows and dolomitization produced a large number of intercrystalline pores.The·coupling of bioturbation and dissolution occurred mainly in the penecontemporaneous phase,and was controlled by rock type,sea level decline,burrow abundance,infillings,and water environment etc.As the burrows had better physical properties than the matrix,unsaturated fluid preferentially migrated along the burrows,leading to dissolution and expansion of the burrows first and then dissolution of the matrix.The coupling of bioturbation and dolomitization occurred mainly in the burial phase.The rich organic matter and reducing bacteria in the burrow provided material basis,reducing conditions and alkaline envi-ronment for dolomitization.The metasomatism in the penecontemporaneous period had little effect on the physical properties of the burrows.When the burrows were se parated from the deposition interface,equimolar metasomatism occurred in the burrows in a closed environment,forming euhedral fine-crystalline dolomite with intercrystalline pores.The transformation degree of bioturbation to muddy carbonate reservoir depends on rock type,density,connectivity,infillings and structure of the burrows.With the increase of the carbonate mud content,the im provement to rock physical properties by bioturbation be-comes more prominent.When the burrows are filled with coarse-grained debris or fine-crystalline dolomite,the greater the density,the higher the connectivity,and the lower the tortuosity of burrows,the better the physical properties of the muddy carbonate rocks are.
文摘As an important factor influencing the physical,chemical and biological processes of sediments,the bioturbation of macrobenthos has received extensive attention in the study of the biogeochemical processes of sediments.However,previous studies provided limited scope for the effects of the bioturbation on the biogeochemical processes of sediments.Based on the analysis of recently published data,this paper presented an integrated overview to summarize the forms of bioturbation (rework,bioirrigation,biodeposition,bioresuspension,biodiffusion),and the effects of bioturbation on the organic matter decomposition,microorganisms,and nutrient flux at the sediment-water interface.To better understand the impacts of bioturbation on biogeochemical processes of sediments,the research should be strengthened in the following aspects in the future: the combination of field experiment and lab simulation test should be strengthened as for the research method;much more attention should be paid to the other sea areas besides hot sea areas and different ecosystems regarding the research area;and the biogenic elements except nitrogen and phosphorus,microorganisms,and heavy metals should be deepened regarding the research content.
基金the Program for Changjiang Scholars and Innovative Research Team of China Ministry of Education(No.IRT0811).
文摘In the Elkhorn River,burrows,tubes,and sediment mounds created by invertebrate bioturbation were observed in the exposed streambed and commonly concentrated on the fine-sediment patches,which consist of silt,clay,and organic matter.These invertebrate activities could loosen the thin layer of clogging sediments and result in an increase of pore size in the sediments,leading to greater vertical hydraulic conductivity of the streambed(Kv).The measurements of the vertical hydraulic gradient across the submerged streambed show that vertical flux in the hyporheic zone can alter directions(upward versus downward)for two locations only a few meters apart.In situ permeameter tests show that streambed Kv in the upper sediment layer is much higher than that in the lower sediment layer,and the calculated Kv in the submerged streambed is consistently greater than that in the clogged sediments around the shorelines of the sand bars.Moreover,a phenomenon of gas bubble release at the water-sediment interface from the subsurface sediments was observed in the groundwater seepage zone where flow velocity is extremely small.The bursting of gas bubbles can potentially break the thin clogging layer of sediments and enhance the vertical hydraulic conductivity of the streambed.
基金Project supported by the National Natural Science Foundation of China(Grants No.41472104 to YBN).The property characterization and interpretation of controlling factor and restriction mechanism of those ichnofabrics enhanced reservoir capacity in marine carbonate rocksProject supported by National Natural Science Foundation of China(Grants No.41102076 to YBN).Ichnofabrics and their reservoir modification effecs in the carbonate rocks from the Ordovician Majiagou Formation,Northwest Henan Province,China+4 种基金Project supported by Natural Science Foundation of Henan Province,China(Grants Nos.202300410185to YBN,and 212300410349 to LJZ)Project supported by The Science and Technology Major Project of Shanxi Province,China(Grant No.20181101013-1)the Program for Innovative Research Team(in Science and Technology)in Universities of Henan Province,China(Grant No.21IRTSTHN007)the Program for Innovative Research Team(in Science and Technology)of Henan Polytechnic University(Grants Nos.T2022-5 and T2020-4)The Funddamental Research Funds for the Universities of Henan Province(Grant No.NSFRF200340to LJZ)。
文摘Bioturbation plays an important role in enhancing the reservoir capacity of tight reservoirs.This study aims to understand the alteration mechanism and effects of bioturbation on oil and gas reservoirs,to clarify the key control factors and constraints influencing the production of bioturbation.The petrophysical characteristics of bioturbation and host sediments in carbonate rocks,such as mineral composition,pore spaces,porosity and permeability,were studied based on the detailed observation and description of the Ordovician cores from the Tahe oilfield.The effect of bioturbation on petrophysical properties of carbonate rocks were carefully analyzed.The results show:(1)Two types of bioturbation,Thalassinoides-like burrows and Planolites-like burrows,mainly occur in the Ordovician cores of the Tahe oilfield,ranging from the Lower-Middle Ordovician Yingshan Formation to the Middle Ordovician Yijianfang Formation.The burrow-fills are mainly composed of dolomite with subhedral and euhedral crystals.The host sediments mainly consist of micrite.(2)The pores in the host sediments are poorly developed and are incapable of forming effective reservoir spaces.However,well-developed intercrystalline pores among dolomites and microfractures in bioturbated sediments with better connectivity can form effective pore spaces.The results of porosity and permeability show that the host sediments without bioturbation are characterized by poor porosity and permeability.However,with the increase of bioturbation intensity,the porosity of the bioturbated sediments firstly increases and then decreases,whereas the permeability increases all the time.(3)Multiple burrows overprinted in the Ordovician carbonate rocks,forming a large-scale bioturbated carbonate rocks with lateral continuity and vertical connectivity,due to the suitable sedimentary setting,ecological conditions,favorable spatiotemporal sediment matching,and abundant organism-substrate interaction.Subsequently,diagenesis(particularly dolomitization and dissolution)has played a positive role in altering the rock fabric and improving the petrophysical properties of bioturbated carbonates.
基金sponsored by the National Natural Science Foundation of China (Nos.21677156,41201498,21107125,51290282,51608515)the National Water Pollution Control and Treatment Science and Technology Major Project (No.2015ZX07205-003)the special fund from the State Key Joint Laboratory of Environment Simulation and Pollution Control (Research Center for Eco-environmental Sciences,Chinese Academy of Sciences) (No.16Z02ESPCR)
文摘Organic matter(OM) is an important component of sediment. Bioturbation/bioirrigation can remobilize OM and heavy metals that were previously buried in the sediment. The remobilization of buried organic matter, thallium(Tl), cadmium(Cd), copper(Cu) and zinc(Zn) from sediment was studied in a laboratory experiment with three organisms: tubificid,chironomid larvae and loach. Results showed that bioturbation/bioirrigation promoted the release of dissolved organic matter(DOM) and dissolved Tl, Cd, Cu and Zn, but only dissolved Zn concentrations decreased with exposure time in overlying water. The presence of organisms altered the compositions of DOM released from sediment,considerably increasing the percentage of fulvic acid-like materials(FA) and humic acidlike materials(HA). In addition, bioturbation/bioirrigation accelerated the growth and reproduction of bacteria to enhance the proportion of soluble microbial byproduct-like materials(SMP). The DOM was divided into five regions in the three-dimensional excitation emission matrix(3 D-EEM), and each part had different correlation with the dissolved heavy metal concentrations. Dissolved Cu had the best correlation with each of the DOM compositions, indicating that Cu in the sediment was in the organic-bound form.Furthermore, the organism type and heavy metal characteristics both played a role in influencing the remobilization of heavy metal.
基金Supported by the Project of Talent Exploitation Foundation of Jilin ProvinceScientific and Technological Developing Scheme of Jilin Province(20060577)+5 种基金the Science and Technology Planning Project of Education Department of Jilin Province(200716920061132006117)High-level Overseas Returned Talents by Ministry of Personnel,Ministry of Personnelthe Scientific Research Foundation for the Returned Overseas Chinese Scholars,State Education Ministry(2005-546)Science Foundation for Young Teachers of Northeast Normal University(20050406)~~
文摘[Objective] The purpose of this study was to investigate the role of breeding Misgurnus anguillicaudatus in paddy field in vertical distribution of sediment particles. [Method] Using chemically stable glass beads as tracers, the effects of Misgurnus anguillicaudatus bioturbation on the vertical distribution of sediment particles in paddy field were investigated, and the bioturbation role of benthic fish in the coupling process of benthic-pelagic interface was discussed. [Result] After ten days of Misgurnus anguillicaudatus bioturbation, 43.2% of the glass beads on the surface were transferred downwardly with the maximum distance of 7.5 cm, and the vertical transportation rate of sediment particles was 7.676×10-4g-1·cm-2·d-1. At a depth of 6 cm, 39.7% and 9.9% of the glass beads were respectively transferred upwards and downwards, to the maximum distanc of 4.5 cm and 5.1 cm, respectively; and the vertical transportation rates of sediment particles were 7.597×10-4g-1·cm-2·d-1 and 1.894×10-4g-1·cm-2·d-1, respectively. [Conclusion] Misgurnus anguillicaudatus bioturbation could promote the circulation and transformation of nutrients at water/soil interface through affecting the vertical distribution of sediment particles.
基金This study was supported by the Zhejiang Public Welfare Technology Research Program of China(ZPWTP)(No.LGN18C190008)the Zhejiang Provincial Natural Science Foundation of China(No.LQ20C190003)the Ningbo Municipal Natural Science Foundation(Nos.2019A610421,2019A610443),and the K.C.Wong Magna Fund in Ningbo University.
文摘The relationships between nutrient dynamics,microbial community,and macrofauna are important in bioremediation systems.In this study,we examined the effects of marine clam Scapharca subcrenata sedimentary activities on the microbial assemblages,benthic nutrient chemistry,and its subsequent remediation impacts on organic effluent in the sediment of an aquaculture wastewater bioremediation system.The results showed that microbial community composition differed significantly in the clam area(ANOSIM,R=0.707,P=0.037).Pyrosequencing of bacterial 16S rRNA gene revealed a total of 48 unique phyla,79 classes,107 orders,197 families,and 321 genera amongst all samples.The most dominant bacterial assemblages were Proteobacteria,Bacteroidetes,Acidobacteria,Firmicutes,Verrucomicrobia,and Actinobacteria,with Bacteroidetes and Firmicutes significantly higher in all treatment samples than control(P<0.001).All dominant phyla in the list were shared across all samples and accounted for 89%(control)and 97%(treatment)of the total 16S rRNA.The nutrient flux rates from the sediments into the water(treatment group)were 51%(ammonium),88%(nitrate),77%(nitrite)and 45%(phosphate)higher,relative to the control implying increased mineralization,degradability,and mobility of the benthic nutrients.Similarly,significantly increased oxygen consumption rates were evident in the clam area signifying improved oxygen distribution within the sediment.The organic effluent contents associated with total-organic matter,carbon,nitrogen,and,phosphate were lower among the clam treatments relative to the control.Our results describe the potential roles and mechanisms contributed by marine bivalve S.subcrenata on benthic-bacterial-community assembly,nutrient balance,and effluent reduction in the sediments of aquaculture wastewaters bioremediation system.
文摘This study investigated the change in denitrification rate in muddy tidal flats sediment by chemical and biological remediation. Column experiments were conducted to determine the dependence of denitrification rate on the redox potential. Filtered seawater was fed continuously to the pipe filled with sediment from the muddy tidal flats. An increase in the redox potential from -198 mV to 21 mV with bioturbation led to increases in the denitrification rate from 24.2 mg/m2/day to 29.8 mg/m2/day. The increase in denitrification was explained by the acceleration of mass transfer in the sediment. Redox-potential increased from -400 mV to -200 mV by the addition of 10 g calcium nitrate, acid volatile sulfide was below the detection limit to 20 cm depth, and denitrification rate was increased from 21.3 mg/m2/day to 36.4 mg/m2/day. It is considered that the increased nitrogen concentration led to an increase in microbial activity.
基金The Strategic Priority Research Program of the Chinese Academy of Sciences under contract Nos XDA23050304 and XDA23050202the Key Research Project of Frontier Science of Chinese Academy of Sciences under contract No.QYZDB-SSWDQC041+3 种基金the Program of Ministry of Science and Technology of the People’s Republic of China under contract No.2015FY210300the National Natural Science Foundation of China under contract No.41061130543the Netherlands Organization for Scientific Research under contract No.843.10.003 as part of the NSFC-NOW “Water ways,Harbours,Estuaries and Coastal Engineering” schemethe self-deployment project of Yantai Institute of Coastal Zone Research,Chinese Academy of Sciences under contract No.YIC755021012
文摘Since the mud snail Bullacta exarata was introduced for economic aquaculture in the Huanghe River(Yellow River) Delta in 2001, its quick population growth and expanded distribution make it a key-species in the intertidal zone of this area. This significantly contributed to the economic income of the local people, but its potential ecological impact on the benthic ecosystem remains unknown. A mesocosm study was conducted to test whether its bioturbation activities affect the microphytobenthos(MPBs;i.e., sedimentary microbes and unicellular algae)productivity and the nutrient exchange between the sediment-water interface. Our results show that the mud snail significantly impacted the dissolved oxygen(DO) flux across the sediment-water interface on the condition of normal sediment and light treatment, and significantly increased the ammonium efflux during recovery period in the defaunated sediment and dark treatment. The presence of micro-and meiofauna significantly increased the NH4-N flux in dark treatment. Whereas, in light treatment, these small animals had less effects on the DO and NH4-N flux between sediment-water interface. Our results provide better insight into the effect of the mud snail B.exarata on the ecosystem functioning via benthic fluxes.
文摘The contribution of benthic foraminifera to sediment bioturbation has widely been overlooked despite their huge abundance in intertidal soft sediments. In this preliminary study, we specifically chose to focus on two key species of benthic foraminifera in temperate intertidal mudflats, <i><span style="font-size:12px;font-family:Verdana;">Quinqueloculina seminula</span></i><span style="font-size:12px;font-family:Verdana;"> and </span><i><span style="font-size:12px;font-family:Verdana;">Ammonia</span></i> <i><span style="font-size:12px;font-family:Verdana;">tepida</span></i><span style="font-size:12px;font-family:Verdana;">, and first experimentally investigated their individual movements at the sediment surface. We subsequently derived from these observations the individual-level surface sediment reworking rates, and used the actual abundance of these species to extrapolate these rates at the population level. Individual surface sediment reworking rates </span><i><span style="font-size:12px;font-family:Verdana;">SSRR</span><sub><span style="font-size:12px;font-family:Verdana;">i</span></sub></i><span style="font-size:12px;font-family:Verdana;"> ranged between 0.13 and 0.32 cm<sup>2</sup><span style="white-space:nowrap;">·</span></span><span style="font-size:12px;"><sup><span style="font-family:Verdana;"></span></sup></span><span style="font-size:12px;font-family:Verdana;">ind</span><span style="font-family:Verdana;font-size:8.33333px;"><sup>-1</sup><span style="white-space:nowrap;">·</span></span><span style="font-size:12px;font-family:Verdana;">day<sup>-1</sup></span> <span style="font-size:12px;font-family:Verdana;">for</span><span style="font-size:10pt;font-family:;" "=""> <i><span style="font-size:12px;font-family:Verdana;">Q. seminula</span></i><span style="font-size:12px;font-family:Verdana;">, and between 0.12 and 0.28 cm<sup>2</sup><span style="white-space:nowrap;">·</span></span><span style="font-size:12px;font-family:Verdana;">ind<sup>-1</sup><span style="white-space:nowrap;">·</span></span><span style="font-size:12px;font-family:Verdana;">day<sup>-1</sup></span><span style="font-size:12px;font-family:Verdana;"> for </span><i><span style="font-size:12px;font-family:Verdana;">A. tepida</span></i><span style="font-size:12px;font-family:Verdana;">. Population-level surface sediment reworking rates were subsequently estimated as ranging between 11,484 and 28,710 cm<sup>2</sup><span style="white-space:nowrap;">·</span></span><span style="font-size:12px;font-family:Verdana;">m<sup>-2</sup><span style="white-space:nowrap;">·</span></span><span style="font-size:12px;font-family:Verdana;">day<sup>-1</sup></span><span style="font-size:12px;font-family:Verdana;"> for </span><i><span style="font-size:12px;font-family:Verdana;">Q. seminula</span></i><span style="font-size:12px;font-family:Verdana;"> and 27,876 and 65,044 cm<sup>2</sup><span style="white-space:nowrap;">·</span></span><span style="font-size:12px;font-family:Verdana;">m<sup>-2</sup><span style="white-space:nowrap;">·</span></span><span style="font-size:12px;font-family:Verdana;">day<sup>-1</sup></span><span style="font-size:12px;font-family:Verdana;"> for </span><i><span style="font-size:12px;font-family:Verdana;">A. tepida</span></i><span style="font-size:12px;font-family:Verdana;">. Noticeably, these reworking rates are comparable to, and eventually even higher than, the rates reported in the literature for populations of intertidal macro-invertebrates, such as the annelid polychaete </span><i><span style="font-size:12px;font-family:Verdana;">Melinna palmata</span></i><span style="font-size:12px;font-family:Verdana;"> and the bivalve </span><i><span style="font-size:12px;font-family:Verdana;">Abra</span></i> <i><span style="font-size:12px;font-family:Verdana;">ovata</span></i><span style="font-size:12px;font-family:Verdana;">. Taken together these results suggest that despite their minute size intertidal benthic foraminifera are, thanks to their abundance, non-negligible contributors to the reworking of surface sediment, and may then play an unanticipated role in the benthic ecosystem functioning, through e.g. the enhancement of fluxes at the sediment-water interface.</span></span>
基金supported by National Basic Research Program of China (Grant No. 2006CB80640)National Natural Science Foundation of China (Grant Nos. 40830212,40772022)
文摘Six ichnogenera,Chondrites,Palaeophycus,Planolites,Rhizocorallium,Skolithos,and Thalassinoides,were identified from the drilling cores near the Global Stratotype Section and Point(GSSP) of Permian-Triassic boundary at Meishan,Zhejiang Province.The ichnological indices,including abundance,bioturbation index,and disturbed depth of trace fossils,show two episodes of intense changes near the Permian-Triassic Boundary(PTB).Episode I occurred in Beds 25-27b when the ecologically complicate forms such as Chondrites,Skolithos,Rhizocorallium,and Thalassinoides disappeared hereafter,the bioturbation index reduced from 1-5 to 1-3,and the disturbed depth declined from 5-66 to 2-5 cm.Episode II took place at the base of Bed 33 with the disappearance of Palaeophycus and Planolites,and subsequent absence of trace fossils and bioturbation till the middle-upper part of Bed 41 when the disturbed structures reoccurred,but they are only tiny Planolites and the bioturbation index was never higher than 3 and the disturbed depth less than 4 mm.Episode I shows an intense change,corresponding to the main stage of the end-Permian mass extinction,whereas Episode II is relatively weak,corresponding to the epilogue of the mass extinction of trace makers in the Early Triassic.Subsequently,ichnofossils were dominated by surface tracks in simple ecological habit and structures.This phenomenon indicates that the Early Triassic benthonic fauna is changed from sessile benthic system to mobile benthic system after the end-Permian mass extinction.In other words,the evolution of the trace fossils across the Permian-Triassic transition had an episodic process similar to the body fossils.In addition,the change of ichnofabrics is well coincided with the negative excursion of carbon isotopes and the expansion of cyanobacteria.As the results of physical and biogenic processes,trace fossils provided unique materials for the study of the biotic and environmental events,as well as their coupling evolution through the great Permian-Triassic transition.
基金The Fundação de AmparoàPesquisa do Estado de São Paulo provided the first author a scientific undergraduate scholarship(2010/01252-5)。
文摘The continuous excavation of burrows by fiddler crabs generates bioturbation in the sediment,which can be estimated from burrow morphology.The aim of the present study was to describe the burrow morphology of Uca uruguayensis and U.leptodactylus and its relationship with demography of resident individuals and to estimate the level of bioturbation in the sediment generated by each species.For all individuals from each of the 2 species,sex was determined and the carapace width(CW;mm)measured.Burrows were characterized according to burrow diameter(BD;mm),maximum burrow depth(MBD;mm)and burrow volume(BV;cm^(3)).The density of each species in the study area was also evaluated.In both species,the males were larger and occupied burrows with higher BV compared to females.Differences between sexes in relation to the burrow characteristics might reflect sexual dimorphism within the group and are probably related to the fact that males use the burrows for mating.BD and BV showed significant positive relationships with the size of resident crabs.The amount of sediment removed per burrow was estimated from mean BV:10.78 cm^(3)of sediment/burrow for U.uruguayensis and 12.38 cm^(3)of sediment/burrow for U.leptodactylus.Despite the density and depth differences between the 2 species,the similarity in burrow volume suggests that U.uruguayensis and U.leptodactylus present the same importance in terms of the bioturbation process.Burrow morphology is highly associated with characteristics of the occupant,although extrinsic factors should also be considered,and its description can provide estimates on the bioturbation generated by Uca species in mangrove forests.