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The influence of bioturbation on sandy reservoirs: the delta front sand of the lower Zhujiang Formation, Baiyun Depression, Zhujiang River Mouth Basin
Zhifeng Xing, Wei Wu, Juncheng Liu, Yongan Qi, Wei Zheng
2023, 42(9): 27-43. doi: 10.1007/s13131-022-2116-z  Published:2023-09-01
Keywords: bioturbation, reservoir physical properties, sedimentary petrofacies, shelf margin delta, Baiyun Sag
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.
Bioturbation coefficients and organic carbon degradation rates of deep-sea sediments in the central-eastern tropical Pacific
Feng Lin, Cai Lin, Xiuwu Sun, Hui Lin, Li Lin, Fangfang Deng, Kaiwen Tan, Peng Lin
Keywords: 210Pb, 226Ra, bioturbation, Tropical Pacific, organic carbon, degradation rate
The biogeochemical processes of marine sediments are influenced by bioturbation and organic carbon decomposition, which is crucial for understanding global element cycles and climate change. Two sediment cores were acquired in 2017 from abyssal basins in the central-eastern tropical Pacific to determine the bioturbation and organic carbon degradation processes. The radioactivity concentrations of 210Pb and 226Ra in the sediment cores were measured, indicating the presence of significant excess 210Pb (210Pbex) signals in the sediment cores. Besides, a manganese nodule was discovered in one core, which had a substantial influence on the distribution of 210Pbex. With the exception of this anomalous finding, the bioturbation coefficients in the remaining core were estimated to be 10.6 cm2/a using a steady-state diffusion model, greater than most of the deep-sea sediments from the Equatorial Eastern Pacific. By using a bio-diffusion model, we further calculated the degradation rates of organic carbon (8.02 ka-1), which is also higher than other areas of the Pacific. Our findings displayed the presence of a biologically active benthic ecosystem in the central-eastern tropical Pacific.
Effects of key species mud snail Bullacta exarata (Gastropoda) on oxygen and nutrient fluxes at the sediment-water interface in the Huanghe River Delta, China
Li Baoquan, Bouma Tjeerd J., Wang Quanchao, Soissons Laura M., Cozzoli Francesco, Feng Guanghai, Li Xiaojing, Zhou Zhengquan, Chen Linlin
2019, 38(8): 48-55. doi: 10.1007/s13131-019-1430-6
Keywords: bioturbation, mud snail Bullacta exarata, oxygen flux, nutrient flux, benthic metabolism, Huanghe River (Yellow River) Delta
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.
Studies on the regional feature of organic carbon in sediments off the Huanghe River Estuary waters
YUAN Huamao, LIU Zhigang, SONG Jinming, LÜ Xiaoxia, LI Xuegang, LI Ning, ZHAN Tianrong
2004(1): 129-134.
Keywords: regional feature, organic carbon, sediments, Huanghe River Estuary
Organic carbon (OC) in definitely small area sediments(according to marine dimension)off the Huanghe River Estuary is investigated in order to evaluate the feature of regional difference of physical and chemical properties in marginal sea sediments. The distributions of OC in sediments with natural grain size and the relationship with the pH,Eh,Es and Fe3+/Fe2+ are discussed. In addition, OC decomposition rates in surfacial/subsurfacial sediments are estimated. OC concentrations range from 0.26% to 1.8%(wt)in the study area. Significant differences in OC content and in horizontal distribution as well as various trends in surfacial/subsurfacial sediments exhibit the feature of regional difference remarkably in marginal sea sediments. The complicated distribution of OC in surface sediments is due to the influence of bacterial activity and abundance, bioturbation of benthos and physical disturbance. The OC decomposition rate constant in surfacial/subsurfacial sediments ranges from 0.009 7 to 0.076 a-1 and the relatively high values may be mainly related to bacteria that are mainly responsible for OC mineralization;meio-and macrofauna affect OC degradation both directly, through feeding on it, and indirectly through bioturbation and at the same time coarse sediments are also disadvantageous to OC preservation. In almost all the middle and bottom sediments the contents of Ocdecrease with the increase of deposition depth, which indicates that mineralization of OC in the middle and bottom sediments has occurred via processes like SO42- reduction and Fe-oxide reduction.
Sedimentary facies and paleoenvironmental interpretation of a Holocene marsh in the Gironde Estuary in France
WANG Jianhua, MASSE Laurent, TASTET Jean-Pierre
2006(6): 52-62.
Keywords: marsh, sedimentation, benthic foraminifera, 14C dating, Holocene sea-level fluctuation, paleoenvironment
The Monards Marsh is located on the northeastern bank of the Gironde Estuary in France.Lithological, sedimentological and micropalaeontological investigations were made on four cores to determine the evolution of Holocene sedimentary environments and processes in this area over the last 6 000 a.Three main lithological facies are distinguished from bottom to top:(1) grey laminated silty-sandy clay; (2) homogeneous dark grey silty clay; and (3) compact silty clay.About 26 benthic foraminifera species are identified and divided into six groups according to their ecological characteristics.In association with lithology, sedimentary structures and grainulometry, the distribution of foraminifera group is used to define external slikke, internal slikke, external schorre, internal schorre, and continental marsh facies.Combined with 14C (AMS) dating, these data indicate four successive paleoenvironments in the Monards Marsh:(1) Holocene transgression resulted in the development of a basal schorre facies overlying fluvial deposits that transformed to slikke facies sedimentation; the transgression maximum occurred around 5 600 to 5 400 a BP and was inferred to be associated with the last phase of the rapid Holocene sea-level rise; (2) post-trangressive maximum sedimentation resulted in a regressive sequence of deposits prograding towards the estuary, corresponding to the stabilisation of sea level after 5 400 a BP; (3) a slight positive tendency in the sea level around 2 800 a BP recorded in the central part of the marsh; and (4) the wetland to a continental marsh environment.The sequential pattern for the evolution of wetlands in this estuarine area during the Holocene is fluvial facies-blackish schorre facies-slikke facies-blackish schorre facies-continental marsh facies.Characteristics of sedimentary facies distribution and evolution reveal that the development of Holocene salt marsh in this area was controlled by the sea-level change and tidal range.The sedimentary facies show an obvious surficial and vertical banding distribution in which the texture and structure, authigenic mineral, foraminifera distribution and bioturbation indicate many distinct difference characteristics.
Enhancement of the benthic communities around an isolated island in the Antarctic Ocean
José I Saiz, Nuria Anadón, Javier Cristobo, Oscar García-Alvarez, Gerardo García-Castrillo, Eduardo López, Cruz Palacín, Jesús S Troncoso, Ana Ramos
2013, 32(6): 47-55. doi: 10.1007/s13131-013-0321-5
Keywords: Antarctica, Bellingshausen Sea, benthos, Peter I Island, PRIMER
Insular marine biotas are often richer in faunal diversity than those from the open sea in the same geographical region. The existence of particular island effects were tested under polar conditions by comparing infaunal benthic assemblages on Peter I Island with those of similar latitudes in the open ocean at the Bellingshausen Sea and also from the coast of the Antarctic Peninsula. Sampling was carried out aboard the R/V Hespérides during the expedition named BENTART-2003 from 24 January to 3 March 2003. Benthic samples were collected at 18 stations ranging from 90 to 2 044m depth, using anUSNEL-type box corer (BC) dredge. Representatives of 32 higher taxa of invertebrates were found. Univariate and multivariate analyses revealed various patterns in the data. First, significant differences in polychaete abundance were detected between the stations located in the open sea and the remaining sites (island plus mainland sites). Bivalve abundances were also distinct between island and mainland sampling sites. Sediment columns taken from the island seafloor exhibited the highest rate of bioturbation by the infauna. These findings confirm the model that islands develop distinct assemblages characterized by the enhancement of the benthic communities even in cold waters. Several abiotic factors were measured simultaneously at the seafloor and along the water column to investigate faunal distribution patterns. Significant correlations were found between the benthic assemblages and a combination of two environmental variables:"island effect" (measured as a categorical variable) and the redox state of sediments. Richer and more complex benthic assemblages were found in Peter I Island's sea bottom, whereas the more depauperate bottoms remained in the open sea.
Community characteristics of macrobenthos in the Huanghe (Yellow River) Estuary during water and sediment discharge regulation
REN Zhonghua, LI Fan, WEI Jiali, LI Shaowen, LV Zhenbo, GAO Yanjie, CONG Xuri
2016, 35(8): 74-81. doi: 10.1007/s13131-016-0881-2
Keywords: macrobenthos, Huanghe (Yellow River)Estuary, ecology, community structure, environment factors
The community characteristics of macrobenthos in the Huanghe (Yellow River) Estuary is influenced by a combination of natural and anthropogenic factors. Here, we investigated short-term changes (1-month) in macrobenthic community structure in response to water and sediment discharge regulation (WSDR) in 2011. Specifically, we sampled the macrobenthos at 18 sampling stations situated at four distances (5, 10, 20, and 40 km) from the mouth of the Huanghe Estuary before (mid-June), during (early-July), and after (mid-July) WSDR. The results showed that a total of 73, 72, and 85 species were collected before, during, and after WSDR, respectively. Then, 13, 1, and 16 dominant species were detected at this three periods. Four phyla were primarily detected at all three periods (Annelida, Mollusca, Arthropoda, and Echinodermata). However, while Mollusca and Annelida were the most important phyla in our study, Echinodermata and Annelida were the most important phyla in 1982, demonstrating major changes to community structure over a 3-decadal period. All stations were of high quality BOPA index before WSDR, whereas two and three stations were of reduced quality BOPA index during and after WSDR, respectively. The results of ABC curves showed that had incurred disturbed conditions after human activities WSDR. Most important of all, multivariate analyses and RDA analysis indicated that the structure of the macrobenthic community was closely linked to environment factors, including that organic content factor caused the distribution of macrobenthic community mostly during WSDR, while water depth after WSDR affected the macro benthos community structure seriously, and during WSDR, the environment factor influencing it was not single, including organic content, sulfide content, Hg and As. These differences may have been due to changes in water transparency negatively impacting the growth and development of macrobenthos, due to specific lifehistory requirements. Our results demonstrate that anthropogenic activity is having both long-term (3 decadal) and short term (1-month) impacts on the structure of the macrobenthic community of the Huanghe Estuary. In conclusion, human activities WSDR influence the habitat environment of macro benthos, including the water temperature, nutrients, bioturbation, and so on. Therefore, we suggest the necessity to strengthen regulations of land-derived organic pollutant input to maintain the ecological balance of the Huanghe Estuary.