共查询到20条相似文献，搜索用时 31 毫秒
1.
海草床是海岸带最富生产力的生态系统之一,支撑着各种各样的伴生生物。热带的印度和太平洋地区被认为拥有海草植物种类多样性最高,且分布面积最广,然而,这个区域的海草床大型底栖生物我们知之甚少。为了填补认知的空白,我们在该区域开展了一项生态调查,旨在描述该区热带海草床大型底栖生物的丰度和多样性,以及确定大型底栖生物丰度、物种丰富度和群落结构是否明显存在断面内的站间变化和样地间变化。2014年5月和2015年10月我们分别在北苏拉威西省东海岸和西海岸开展野外工作,使用柱状取样器采集海草床大型底栖生物样品。所得样品共计鉴定14大类149种底栖生物,种类最为丰富的类别为多毛类（56种,占26%的总个体数）,十足类（20种,占9%的总个体数）和端足类（18种,占35%的总个体数）。东、西海岸海草床大型底栖生物表现出不同的空间分布模式。在东海岸,同一断面的大型底栖生物和端足类的丰度存在显著的站间差异;而在西海岸,大型底栖生物和多毛类的种类丰富度和丰度都表现出明显的站间变化,这可能归结于同一断面底质不均所造成。单因素ANOSIM以及MDS排序表明了北苏拉威西省东海岸和西海岸海草床大型底栖生物群落结构存在显著不同,正好对应于将海草床分成两大类型的栖息地,即西海岸的红树林-海草床-珊瑚连续体和东海岸的海草床-珊瑚连续体。与在热带海区开展的其他研究相比,本研究的大型底栖生物丰度和多样性处于中等水平。东、西海岸海草床大型底栖生物群落存在显著区别,其原因可能源于多方面,包括了沉积物模式,海草床结构和时间变化。 相似文献
2.
A field experiment was carried out in Hong Kong to study the patterns of recolonization and succession of subtidal macrobenthos in defaunated sediment contaminated with petroleum hydrocarbons and to determine the time required for benthic recovery from petroleum contamination. A total of 31 species was found and 83 animals/tray and 14 species/tray on an average were recorded after one month. Initial colonization was dominated by polychaetes in both abundance and species number (accounting for 69.1% and 64.5%, respectively). Abundance of macrobenthos came to a small crest (308 animals/tray) after three months, reached a sharp peak (1257 animals/tray) after six months, and then declined to a steady level. Abundance, species number and diversity in the petroleum-contaminated sediment were significantly lower than those in the control sediment in the early successional stages, indicating deleterious effects of petroleum hydrocarbons on recolonization and succession of macrobenthos. Petroleum hydrocarbons in sediment significantly altered species composition of macrobenthos in recolonization and succession. No significant differences in community parameters and species composition between the petroleum-contaminated and the control communities were found after 11 months, indicating that macrobenthic community had recovered from petroleum contamination. 相似文献
3.
Sediment organic and metal chemistry, benthic infauna and tissue contaminants surveys have been conducted over 19 years before and following tailings deposition from a metal (Mo, Pb, Zn) mine in Alice Arm, a British Columbia fjord. We found changes in benthic fauna and habitat after tailings disposal to be predictable in terms of sediment chemistry and faunal recolonization. What was not predictable was the timing and extent of slope failure or resuspension following abandonment. These events can have essentially the same or greater effect than the initial tailings disposal and produce long-term unpredictability particular to cases of submarine disposal on slopes. The present study focused on the submarine deposition of 4 x 10(6) tonnes of tailings during an 18-months period ending October 1982. When the mine closed, gross defaunation had occurred at three stations in the tailings path, and two others showed recent defaunation and recolonization. A year later, a large tailings slump near the outfall transported tailings to the deep basin; fauna were impoverished both in the slump region and through most of the deep basin. Declining metal concentrations in surface sediments was accompanied by considerable recovery of fauna 3 years after the mine closed. Nevertheless, fauna at the three stations defaunated at the time of mine closure could still be statistically distinguished from all other stations due to high abundances of small opportunistic polychaetes and bivalves. A resuspension in tailings between 1988 and 1990 coincided with a moderate decline in abundance of all macrofauna taxa. From 1989 to 1995 recovery toward natural sediment conditions was evident as increasing organic content together with the highest faunal biomass values found during the study. Small polychaetes were the first recolonizers in defaunated areas, whereas small bivalves were more tolerant of moderate tailings deposition. By 1989 and 1995 small colonizers had declined and amphipods and larger echinoderms had increased. Dominant species patterns and exceptionally high biomass values in 1995 show that the largest fauna did not recover until much later than smaller taxa. One genus of bivalve (Yoldia spp.) accumulated metals in a pattern similar to the sediment chemistry, indicating that the metals from the most recent mine had entered the benthic food chain. It is not possible to tell from this study whether biota were affected by toxicity from metals. However, many of the observed biotic effects could be caused by physical disruption from tailings. 相似文献
4.
广西钦州湾大型底栖动物生态特征及其与沉积物环境的相关性研究 总被引：1，自引：0，他引：1
为研究钦州湾大型底栖动物的生态特征,探讨影响大型底栖动物分布的主要因素,于2011年5月在钦州湾进行大型底栖动物调查,并同步采集沉积物样品,进行理化性质分析。使用Surfer软件绘制各群落特征指数的平面分布图,用SPSS软件分析群落特征指数与沉积物环境因子之间的关联性。共采集到大型底栖动物种类55种。平均生物量为105.48 g/m2,平均密度为50ind/m2。香农-维纳指数(H')、种类均匀度指数(J')和丰富度指数(D)的平均值分别为1.44,0.63和0.64。群落特征指数与沉积物环境因子之间的相关性分析结果显示,密度与Cu,Pb,Zn,Cd,Cr,Hg以及有机碳呈显著负相关;种类数与所分析的10项沉积物环境因子之间均呈显著负相关;均匀度指数与Hg和有机碳呈显著负相关;丰富度指数与硫化物呈显著负相关;生物量和香农-威纳指数与沉积物各环境因子之间均没有显著的相关性。 相似文献
5.
This study tested the hypothesis that the small-scale topography caused by ripples in sediment would affect benthic macrofaunal assemblages. Ripple marks were measured and macrofauna and sediments were sampled near to and far from subtidal rocky reefs at two sites. Ripples were significantly wider and taller close to than far from reefs. Sediment grain-size was significantly different between crests and troughs. Microtopography clearly influenced the structure of the benthic macrofaunal assemblages in three of the four locations (and 8 of the 12 sites) examined. Numbers of taxa of the benthic macrofaunal assemblages and almost all individual taxa analysed showed significant greater abundances in troughs than in crests. The results strongly support the model that benthic macrofauna are affected by locally varying hydrodynamic environments produced by ripple-beds. These, in turn, were influenced by their proximity to a reef. Models about passive transport of the macrofauna by water-movement and active movements of the fauna are discussed. Furthermore, it appeared that there was a relationship between spatial variability of the macrofaunal assemblages and size of ripples. It is suggested that microtopography should be considered in experimental designs when patterns of distribution of benthic organisms are being evaluated. 相似文献
6.
This study demonstrated the spatiotemporal patterns of the environmental conditions and benthic macrofauna in Tokyo Bay, Japan, and investigated the factors causing disturbances in the assemblage structure. In the north-central areas, the density and species diversity of the macrobenthos was low. Although hypoxia appeared in July, defaunation occurred in August. The delayed defaunation and recolonization soon after the abatement of hypoxia were attributed to several polychaete and bivalve species that were tolerant to the hypoxic environment. In the southeastern areas, however, the density and species diversity of the macrobenthos was high throughout the year, and no defaunation was recorded. Multivariate analyses showed that the disturbance in the macrofauna correlated with organic enrichment in the sediment and bottom-water hypoxia. There is a concern about further impairment of the macrofauna in the bay due to the expansion of sediment with high levels of organic matter towards the southern regions that could cause hypoxia and subsequent defaunation. 相似文献
7.
Rocas, the only atoll in the South Atlantic, is located 266 km off the northeast Brazilian coast. Spatial patterns in community structure of meiofauna, particularly nematodes, and macrofauna were examined along a transect through the sediment path from windward to leeward of the Rocas Atoll sand flat. Differences in benthic community structure between four zones of the sand flat were found to be significant and related to the major local processes of carbonate-grain transport and sedimentation. Both meiobenthic and macrobenthic assemblages were significantly more diverse and abundant within the sediment inflow zone (the initial part of the detrital path of Rocas sand flat) than in the other zones, where a clear impoverishment of benthic invertebrates occurred. This first study of the benthos of an intertidal sand flat over a reef island in the Atlantic showed that the meiofauna is numerically dominated by the nematodes Metoncholainussp. 1 (Oncholaimidae) and Epsilonema sp. 1 (Epsilonematidade), whilst the macrofauna is largely dominated by oligochaetes and large Oncholaimidae nematodes. Analysis of the species composition, trophic structure and abundance of both the meiobenthos and the macrobenthos revealed an impoverished community subjected to an intense water-movement disturbance. 相似文献
8.
Francesca Pasotti Elena Manini Donato Giovannelli Anne‐Cathrin Wölfl Donata Monien Elie Verleyen Ulrike Braeckman Doris Abele Ann Vanreusel 《Marine Ecology》2015,36(3):716-733
The West Antarctic Peninsula is one of the fastest warming regions on Earth. Faster glacier retreat and related calving events lead to more frequent iceberg scouring, fresh water input and higher sediment loads, which in turn affect shallow water benthic marine assemblages in coastal regions. In addition, ice retreat creates new benthic substrates for colonization. We investigated three size classes of benthic biota (microbenthos, meiofauna and macrofauna) at three sites in Potter Cove (King George Island, West Antarctic Peninsula) situated at similar water depths but experiencing different disturbance regimes related to glacier retreat. Our results revealed the presence of a patchy distribution of highly divergent benthic assemblages within a relatively small area (about 1 km2). In areas with frequent ice scouring and higher sediment accumulation rates, an assemblage mainly dominated by macrobenthic scavengers (such as the polychaete Barrukia cristata), vagile organisms and younger individuals of sessile species (such as the bivalve Yoldia eightsi) was found. Macrofauna were low in abundance and very patchily distributed in recently ice‐free areas close to the glacier, whereas the pioneer nematode genus Microlaimus reached a higher relative abundance in these newly exposed sites. The most diverse and abundant macrofaunal assemblage was found in areas most remote from recent glacier influence. By contrast, the meiofauna showed relatively low densities in these areas. The three benthic size classes appeared to respond in different ways to disturbances likely related to ice retreat, suggesting that the capacity to adapt and colonize habitats is dependent on both body size and specific life traits. We predict that, under continued deglaciation, more diverse, but less patchy, benthic assemblages will become established in areas out of reach of glacier‐related disturbance. 相似文献
9.
西北冰洋表层沉积物中的底栖有孔虫组合及其古环境意义 总被引：1，自引：1，他引：0
通过对中国第1~4次北极考察在西北冰洋采集的表层沉积物中底栖有孔虫丰度及其优势种分布特征与环境因素关系的综合研究发现,楚科奇海区低的底栖有孔虫丰度主要受较高的陆源物质输入的稀释作用影响;楚科奇海台和阿尔法脊较高的底栖有孔虫丰度主要受到暖而咸的大西洋中层水的影响;受碳酸钙溶解作用影响的门捷列夫深海平原和加拿大海盆底栖有孔虫丰度较低,并且水深3 597 m的站位出现了似瓷质壳的Pyrgo williamsoni和Quinqueloculina orientalis,说明该区的CCD深度大于3 600 m。根据底栖有孔虫7个优势属种的百分含量分布特征可以划分出5个区域组合:南楚科奇海陆架-白令海峡组合以优势种Elphidium excavatum和Buccella frigida为特征,可能反映受白令海陆架水影响的浅水环境;阿拉斯加沿岸-波弗特海组合以优势种Florilus scaphus和Elphidium albiumbilicatum为特征,可能反映受季节性海冰融化,低盐的阿拉斯加沿岸流以及河流淡水输入的低盐环境;大西洋中层水组合以优势种Cassidulina laevigata为特征,可能反映高温高盐的大西洋中层水影响的环境;北极深层水组合以优势种Cibicides wuellerstorfi为特征,可能反映水深大于1 500 m低温高盐的北极深层水环境;门捷列夫深海平原组合以优势种Oridorsalis umbonatus为特征,可能反映低营养的底层水环境。 相似文献
10.
Short-Term Benthic Recolonization after Dredging in the Harbour of Ceuta, North Africa 总被引：2，自引：0，他引：2
Abstract. The benthic recovery after dredging (area: 2625 m2) was studied in a polluted and enclosed area of the harbour of Ceuta, in which the recolonization through the water column (larvae and adult bedload transport) could be limited by the lack of renewal. The benthos was sampled at two sites (control and dredged) using a van Veen grab and adopting a BACI (Before, After, Control, Impacted) approach. Five samplings were conducted after dredging (3, 15, 30, 90, 180 days). The proportion of gravel in the sediment of the dredged site increased after dredging, while the organic matter decreased. The impact on the community was estimated at species level, using both univariate and multivariate analyses. The maximum negative effect on benthic macrofauna was a reduction by 65% for species richness (15 days after dredging) and by 75% for abundance (3 days after dredging). Between 15 and 30 days after dredging, the abundance of some species such as the molluscs Parvicardium exiguum and Retusa obtusa and the polychaete Pseudomalacoceros tridentata increased considerably in the dredged site, while typical ‘opportunistic’ species such as Capitella capitata were disfavoured by the disturbance. For this small‐scale dredging, about 6 months are required for the disturbed area to re‐establish a sediment structure and a macrobenthic community similar to the undisturbed area. Small‐patch dredging operations are proposed in harbour management whenever possible, since they allow a quick re‐adjustment of the initial sediment structure and benthic communities. 相似文献
11.
12.
Betina J. Lomovasky Fausto N. Firstater Alex Gamarra Salazar Jaime Mendo Oscar O. Iribarne 《Journal of Sea Research》2011,65(2):205-212
Macrobenthic soft bottom community assemblages were studied from December 2006 to December 2007 at Paracas Bay (Atenas Beach, 13°45' S, 76°17' W, Peru), including the period of the tsunami of 15 August 2007, providing a unique opportunity to assess the effects of this type of natural disturbance in soft bottom marine ecosystems. The results show that the tsunami affected the soft bottom community assemblage by changing the sediment granulometry, the biomass and abundance of epifaunal species, and by increasing the silt proportion. The event affected all functional groups, resulting in an increased numbers and biomass of filter feeder and grazers that were followed soon after by predators during the post-tsunami period. A similar pattern was observed for biomass and the abundance of infaunal species without changing the functional groups. The slow recovery observed after four months was likely related to the loss of sediment stability. In summary, there were differences in the structure and composition of soft bottom macrofaunal assemblages before and after the earthquake and posterior tsunami disturbance, forcing benthic communities to initiate re-colonisation processes. 相似文献
13.
The cockle Cerastoderma edule L. occurs at commercially exploited densities within both species-poor and species-rich assemblages, dominating the faunal biomass and potentially acting as a key contributor to a number of ecological functions. The questions considered were: Is the delivery of ecological functions affected by the removal of C. edule ? Does the biodiversity of the affected assemblage affect the extent to which it is altered? To explore these questions, adult cockles were removed from experimental plots at two shores in the North-West of England: a species-poor shore at Warton Sands, Morecambe Bay, and a more diverse shore at Thurstaston, Dee estuary. Impacts on the functioning of the systems were determined during a 4-month study in summer 2007 by direct measurements of benthic primary production, organic matter content and sediment granulometry, and by indirect analyses using Biological Traits Analysis. Removal of adult cockles led to significant changes in faunal assemblage composition and in the distribution of biological traits, with increased biodiversity and an increased prevalence of traits relating to opportunistic taxa observed following the removal of C. edule . These changes occurred at both study sites and hence were independent of the initial biodiversity of the assemblages. Sediment granulometry was significantly affected; however, surface chlorophyll and organic matter were not affected. This implies a minimal impact on these functions and a high degree of functional redundancy within the macrofauna. The implications of these findings and future areas of research are discussed. 相似文献
14.
渤海大型底栖动物种类组成与群落结构研究 总被引：1，自引：1，他引：0
本文利用2008年8月在渤海23个站位采集的样品对大型底栖动物的丰度、生物量、群落结构及其与环境因子的关系进行了研究。共鉴定出大型底栖动物300种,主要类群包括环节动物多毛类、节肢动物甲壳类、软体动物、棘皮动物等。研究海域大型底栖动物的平均丰度为1 094.7ind/m2,平均生物量为11.78g/m2,其中丰度最高区位于辽东湾,最低区位于渤海湾;生物量最高区位于渤海中部,最低区出现在渤海海峡湾口处。依据丰度和生物量进行了CLUSTER聚类和MDS标序图分析,结果可将研究站位划分为6个站组,均与沉积物底质类型密切相关。所研究海域底质类型包括黏土质粉砂、砂、砂质粉砂、粉砂质砂、砂-粉砂-黏土5种。通过BIOENV分析,发现影响大型底栖动物群落结构和分布的主要环境因子有水深、黏土粉砂含量、脱镁叶绿酸含量、叶绿素含量等。与20世纪90年代历史数据的对比发现,本次研究大型底栖动物的物种数目明显减少,平均丰度也减少,特别是优势物种表现出了小型化趋势,传统的大型种类,如心形海胆、双壳类等,被小个体的多毛类和甲壳类所取代。本研究表明渤海近年来受人类活动影响,出现了不同程度的污染,导致大型底栖动物群落结构发生了变化。 相似文献
15.
Anna R. Armitage Vanessa L. Gonzalez Peggy Fong 《Estuarine, Coastal and Shelf Science》2009,84(3):375-380
Strong interactions between top-down (consumptive) and bottom-up (resource supply) trophic factors occur in many aquatic communities, but these forces can act independently in some microphytobenthic communities. Within benthic estuarine diatom assemblages, the dynamics of these interactions and how they vary with abiotic environmental conditions are not well understood. We conducted a field experiment at two sites with varying habitat characteristics to investigate the interactive effects of grazers and nutrients on benthic estuarine diatoms. We crossed snail (Cerithidea californica) and nutrient (nitrogen and phosphorus) addition treatments in enclosures on a restored tidal sandflat and a reference tidal mudflat in Mugu Lagoon, southern California. We repeated the study in summer 2000 and spring 2001 to assess temporal variation in the interactions. Snails caused a large decrease in diatom relative abundance and biomass (estimated as surface area); nutrients increased diatom abundance but did not alter diatom biomass. Snails and nutrients both reduced average diatom length, although the nutrient effect was weaker and temporally variable, occurring in the reference mudflat in the spring. There were few interactions between snail and nutrient addition treatments, suggesting that links between top-down and bottom-up forces on the diatom community were weak. There were no consistent differences in diatom assemblage characteristics between the two study sites, despite marked differences in sediment grain size and other abiotic characteristics between the sites. The strong diatom response to herbivores and weaker responses to enrichment differed from the previous studies where cyanobacteria increased in response to nutrient enrichment, further dissolving the “black box” perception of microphytobenthic communities. 相似文献
16.
Sediment segregation by biodiffusing bivalves 总被引：1，自引：0，他引：1
F. Montserrat C. Van Colen P. Provoost M. Milla M. Ponti K. Van den Meersche T. Ysebaert P.M.J. Herman 《Estuarine, Coastal and Shelf Science》2009,83(4):379-391
The selective processing of sediment fractions (sand and mud; >63 μm and ≤63 μm median grain size) by macrofauna was assessed using two size classes of inert, UV-fluorescent sediment fraction tracers (luminophores). The luminophores were applied to the sediment surface in 16 m2 replicated plots, defaunated and control, and left to be reworked by infauna for 32 days. As the macrofaunal assemblage in the ambient sediment and the control plots was dominated by the common cockle Cerastoderma edule, this species was used in an additional mesocosm experiment. The diversity, abundance and biomass of the defaunated macrobenthic assemblage did not return to control values within the experimental period. Both erosion threshold and bed elevation increased in the defaunated plots as a response to the absence of macrofauna and an increase in microphytobenthos growth. In the absence of macrobenthos, we observed an accretion of 7 mm sediment, containing ca. 60% mud. Image analysis of the vertical distribution of the different luminophore size classes showed that the cockles preferentially mobilised fine material from the sediment, thereby rendering it less muddy and effectively increasing the sand:mud ratio. Luminophore profiles and budgets of the mesocosm experiment under “no waves–no current” conditions support the field data very well. 相似文献
17.
Nafsika Papageorgiou Christos Arvanitidis Anastasios Eleftheriou 《Estuarine, Coastal and Shelf Science》2006,70(4):643
The aim of this paper is to study the macrofaunal community dynamics and the biological–environmental interactions in the mid- and sublittoral ecosystems of the microtidal Mediterranean sandy shores. Four sandy beaches, three on the island of Crete and one on the northwest coast of Italy were selected to investigate the spatial and temporal changes in the community structure and the associated environmental variables. The littoral zone, which has not been adequately studied in the Eastern Mediterranean, presents special interest not only from the scientific point of view but also for practical reasons of ecological management. The multivariate techniques revealed that the community pattern of the sandy beach macrofauna is mainly spatial rather than temporal. There are pronounced differences in species composition and abundance of the macrofaunal assemblages of the mid- and sublittoral zone. The multicausal environmental severity hypothesis appears to be valid for the sandy beach macrofaunal communities of the Mediterranean. The abundance and composition of the macrofaunal assemblages are highly variable and are affected by the synergistic effects of many environmental variables. The polychaete taxonomic assemblage structure closely follows the macrofaunal community pattern. Differences between the two patterns may arise from the different responses that polychaetes may show to the environmental stress. 相似文献
18.
Claudia Gutterres Vilela 《Geo-Marine Letters》1995,15(3-4):199-203
The distribution of benthic foraminiferal microfauna recovered from two offshore transects on the Amazon shelf was studied. Eight box-core samples were collected along the inner, middle, and outer parts of the continental shelf. Each box-core sample was divided into 10 subsamples, of 1- to 5-cm intervals, in order to investigate the foraminiferal microhabitat preferences. The variations of salinity, oxygen, lithology, and sediment accumulation rates were used to evaluate ecological patterns. Four benthic foraminiferal assemblages identified in the study area characterize a record of oceanographic changes from early Holocene to the present. An abundant assemblage, with opportunistic species, was found near the river mouth. Two assemblages were identified northwest of the river mouth, with dominant epifaunal and infaunal species, respectively. A relict assemblage was encountered northwest of the river mouth. 相似文献
19.
《Oceanologica Acta》2003,26(1):67-75
The macrobenthic community structure of the Valli di Comacchio (northern Italy) was described in order to assess the ecological conditions of the main basins through 2001. In addition, the biotic data set gathered in 1997–1998 was compared to achieve an estimation of the eventual recovery of the lagoonal benthic assemblages. Four permanent sites (P1, M4, M5 and M6), located along a gradient of sediment texture and confinement, and representing four different areas of the lagoon, were sampled quarterly in 2001 for macrofauna and sedimentary variables (organic content, phytobenthic chlorophyll-a, depth of the redox potential discontinuity layer), and fortnightly for water variables (temperature, salinity, dissolved oxygen and planktonic chlorophyll-a). Water and sedimentary variables were typical of eutrophic areas. A total of 52 macrobenthic taxa were identified and, on the basis of the species collected, differences in faunal distribution among the four areas were recognized, although less marked than in previous studies. Sediment trophic status and its seasonal dynamics in the Valli were crucial in determining species distribution among the different areas. The comparison between 1997–1998 and 2001 biotic data indicated that conditions in the lagoon had improved, especially in the formerly most impaired, central area. In the Valli di Comacchio, the recovery of benthic communities after severe disturbance will probably take longer, even if sewage discharges have been removed 11 years ago. Secondary disturbance due to scarce water circulation, sharp temperature and salinity fluctuations, release of toxic substances from sediments influenced animal assemblages along spatial and temporal scales. The interplay of these variables probably caused deviations from the expected improvement in benthic conditions. Nevertheless, clear signs of amelioration, particularly at the previously most impaired area, were detectable. 相似文献
20.
Silvia Hess Frans J. Jorissen 《Deep Sea Research Part I: Oceanographic Research Papers》2009,56(9):1555-1578
Analysis of living (Rose Bengal-stained) benthic foraminifera in 13 multicorer samples taken along the Cap Breton canyon (Bay of Biscay) revealed that the combination of organic-rich material and sediment instability provides very specific benthic ecosystem conditions. The active canyon hosts different foraminiferal assemblages that appear to be determined by different types and frequencies of environmental disturbance at the sites. Most of them are strongly dominated by shallow-infaunal living taxa that combine a tolerance for low-quality organic matter with a high reproductive potential. Foraminiferal assemblages characterized by high densities, very superficially living taxa and strong dominance of bolivinids and buliminids, follow a poor pioneer fauna dominated by Technitella melo. These assemblages are observed in the narrow canyon axis, where frequent sediment resuspension occurs and affects habitat stability. Assemblages studied from sites outside the canyon axis are still dominated by shallow-infaunal species but show lower foraminiferal densities and higher diversities. Deep-infaunal taxa are only present in some inner meanders and more distal stations. These assemblages are typical for ecological niches that are relatively stable and unaffected by re-sedimentation processes. They have attained a more advanced stage of ecosystem stability. They are influenced by neither lateral sediment nor enriched organic matter input. 相似文献