首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 31 毫秒
1.
A comparison of sediments and associated macrobenthos at sites sampled within 20 fish farm leases distributed across southeastern Tasmania indicated major natural changes along a regional cline. Introduced taxa were strongly represented in the fauna, comprising 45% of total macrofaunal biomass. Large differences were evident between sites affected by different levels of organic farm waste. Sites located adjacent (< 10 m) to farm cages possessed significantly depressed sediment redox levels, a dominance of capitellid and dorvilleid polychaetes, and low macrofaunal species richness. Subtle impacts extended across farm lease areas in the form of depressed redox potential at 40 mm depth and changes to the macrobenthic community, including a prevalence of the dogwhelk Nassarius nigellus and a paucity of the heart urchin Brissus sp. and the maldanid polychaetes Asychis sp. and Rhodine sp. Minor farm effects were also evident at sites sampled 35 m outside farm lease boundaries, most notably as elevated population numbers of the polychaete Terrebellides sp., bivalve Mysella donaciformis and heart urchin Echinocardium cordatum. Amongst the univariate metrics examined, redox potential at 40 mm depth and the ratio of bivalves to total molluscs provided the most sensitive indicators of farm impacts, with the latter metric relatively insensitive to spatial variation between locations within the region studied.  相似文献   

2.
Diversity and distribution of polychaetes on the southeastern Brazilian Shelf (SBS) adjacent to the city of Santos were studied. The study area is situated in the vicinity of Santos Bay with its estuarine complex and other small rivers along the coast. A total of 16,274 specimens belonging to 214 polychaete species were found at 21 sampling stations during two different periods. Two communities occur along the shelf and were related firstly to sediment characteristics. Prionospio dayi (Spionidae) was dominant in the inner shelf community that was characterized by well-sorted, very fine sand. The outer shelf community was found in muddy sediments with high organic matter content and was dominated by subsurface deposit feeders, like Petersenaspis capillata (Sternaspidae) and Leitoscoloplos kerguelensis (Orbiniidae), and by large carnivores such as Aglaophamus sp. (Nephtyidae) and Sigambra sp. (Pilargidae). A transition zone of mixed sediments presenting high diversity and richness was found between these communities. The characteristics of bottom water and food quality in the sediment were important to divide the inner shelf into two sub-areas. Nearshore sampling stations (A group) were more influenced by freshwater input, mainly during summer. This influence is not conspicuous at stations close to 30?m depth (B group). However the effect of South Atlantic Central Water mass (SACW) intrusion on the benthic system was observed on the inner shelf – B group during the summer. The summer intrusion of SACW onto the inner shelf may explain the higher quality of organic matter that resulted in an increase in polychaete abundance and richness.  相似文献   

3.
Six sandy beach stations along the Jordan Gulf of Aqaba were selected for macrofaunal examination during November 1980. Fifteen core samples (0.01 m2 to a depth of 10–15 cm) were taken at each station; five at the high tide line, five at the low tide line, and five midway. Twenty-two taxa were encountered from all stations. Polychaetes were the most diverse group with seven taxa, followed by molluscs and crustaceans with six and five taxa respectively. Animal diversity, using the Shannon-Wiener Index, was generally low. Based on the biological index value of McCLOSKEY (1970), seven taxa were considered the community dominants. These are: the polychaetes, Glycera tesselata, Pisione remota, Saccocirrus sp., and Perinereis nuntia; the isopod Eurydice arabica; a nemertean and an oligochaete.  相似文献   

4.
The continental margin off the northeastern United States (NEUS) contains numerous, topographically complex features that increase habitat heterogeneity across the region. However, the majority of these rugged features have never been surveyed, particularly using direct observations. During summer 2013, 31 Remotely-Operated Vehicle (ROV) dives were conducted from 494 to 3271 m depth across a variety of seafloor features to document communities and to infer geological processes that produced such features. The ROV surveyed six broad-scale habitat features, consisting of shelf-breaching canyons, slope-sourced canyons, inter-canyon areas, open-slope/landslide-scar areas, hydrocarbon seeps, and Mytilus Seamount. Four previously unknown chemosynthetic communities dominated by Bathymodiolus mussels were documented. Seafloor methane hydrate was observed at two seep sites. Multivariate analyses indicated that depth and broad-scale habitat significantly influenced megafaunal coral (58 taxa), demersal fish (69 taxa), and decapod crustacean (34 taxa) assemblages. Species richness of fishes and crustaceans significantly declined with depth, while there was no relationship between coral richness and depth. Turnover in assemblage structure occurred on the middle to lower slope at the approximate boundaries of water masses found previously in the region. Coral species richness was also an important variable explaining variation in fish and crustacean assemblages. Coral diversity may serve as an indicator of habitat suitability and variation in available niche diversity for these taxonomic groups. Our surveys added 24 putative coral species and three fishes to the known regional fauna, including the black coral Telopathes magna, the octocoral Metallogorgia melanotrichos and the fishes Gaidropsarus argentatus, Guttigadus latifrons, and Lepidion guentheri. Marine litter was observed on 81% of the dives, with at least 12 coral colonies entangled in debris. While initial exploration revealed the NEUS region to be both geologically dynamic and biologically diverse, further research into the abiotic conditions and the biotic interactions that influence species abundance and distribution is needed.  相似文献   

5.
深圳河口福田泥滩海洋线虫的种类组成及季节变化   总被引:8,自引:0,他引:8  
1997年4个季度在深圳河口福田泥滩3个取样站采到海洋线虫28种,隶属于3目13科22属。优势种是微口线虫(Terschellingia spl.)、蚕咽线虫(Daptonema sp1.)、Metalinhomoeus sp.和拟齿线虫(Paradontophora sp.)4种。春季海洋线虫密度最高,冬季次之,夏季第三,秋季最低。深圳河口福田泥滩的海洋线虫群落与大型底栖动物群落具有相似的特点,  相似文献   

6.

Background

In contrast to the well-studied continental shelf region of the Gulf of Maine, fundamental questions regarding the diversity, distribution, and abundance of species living in deep-sea habitats along the adjacent continental margin remain unanswered. Lack of such knowledge precludes a greater understanding of the Gulf of Maine ecosystem and limits development of alternatives for conservation and management.

Methodology/Principal Findings

We use data from the published literature, unpublished studies, museum records and online sources, to: (1) assess the current state of knowledge of species diversity in the deep-sea habitats adjacent to the Gulf of Maine (39–43°N, 63–71°W, 150–3000 m depth); (2) compare patterns of taxonomic diversity and distribution of megafaunal and macrofaunal species among six distinct sub-regions and to the continental shelf; and (3) estimate the amount of unknown diversity in the region. Known diversity for the deep-sea region is 1,671 species; most are narrowly distributed and known to occur within only one sub-region. The number of species varies by sub-region and is directly related to sampling effort occurring within each. Fishes, corals, decapod crustaceans, molluscs, and echinoderms are relatively well known, while most other taxonomic groups are poorly known. Taxonomic diversity decreases with increasing distance from the continental shelf and with changes in benthic topography. Low similarity in faunal composition suggests the deep-sea region harbours faunal communities distinct from those of the continental shelf. Non-parametric estimators of species richness suggest a minimum of 50% of the deep-sea species inventory remains to be discovered.

Conclusions/Significance

The current state of knowledge of biodiversity in this deep-sea region is rudimentary. Our ability to answer questions is hampered by a lack of sufficient data for many taxonomic groups, which is constrained by sampling biases, life-history characteristics of target species, and the lack of trained taxonomists.  相似文献   

7.
Depth-related patterns of macrobenthic community structure and composition have been studied from box-core samples from the Scottish continental slope where deep-sea trawling and oil exploration are becoming increasingly important. There is a strong pattern of declining biomass and faunal abundance with increasing depth, but results also indicate reduced biomass and numbers of macrobenthos in the shallowest samples from just below the shelf edge where there are coarse sediments and a regime of strong bottom currents. There is also reduced species diversity at the shallowest stations, probably caused by hydrodynamic disturbance, but no clear mid-slope peak in species diversity as described from the northwest Atlantic. Taxonomic composition of the macrobenthic community shows most change between about 1000 and 1200 m, expressed as a major dichotomy in multivariate analysis by cluster analysis and ordination. It also shows up as a step-like increase in the rate of accumulation of new macrofaunal species. This corresponds to a change in hydrodynamic regime, from a seabed rich in suspension- and interface-feeding epifauna, to one where biogenic traces from large, burrowing deposit feeders are well developed, and visible epifauna rare in seabed photographs. It also corresponds to the depth zone where earlier study of megafaunal echinoderms in trawl and epibenthic sled samples also shows a clear peak in across-slope rate of change in faunal composition.  相似文献   

8.
9.
The main purpose of this study was to evaluate the efficiency of the alternative quantitative sampling approach and if it was possible, by using this method, to elucidate temporal variations concerning the composition, vertical distribution, and abundance of the motile epifaunal community. The study was performed on a vertical rocky bottom in Gullmarsfjorden on the Swedish west coast. Quantitative sampling was performed at four depths (2, 6, 10 and 15 m) on three occasions (19 June, 23-24 July and 23 September 1996) by means of a water jet powered suction sampler (venturi principle). In total, 53 macrofaunal taxa were found, of which 29 taxa occurred on all sampling dates. Significant vertical zonation patterns were recorded in July and September, but not in June, with amphipods, polychaetes, and echinoderms (mainly Asterias rubens) as the most important contributors to these patterns. A temporal variation in the faunal assemblage also occurred. Species abundance was significantly different between the sampling dates at 2, 6 and 10 m, but not at 15 m. The abundance was higher in July and September than in June. Species with the highest observed differences in abundance were juvenile Asterias rubens, abundant in July, while juvenile shrimp, especially Thoralus cranchii, and some amphipods, especially Microdeutopus spp., increased in abundance in September. This sampling approach was highly effective, and the high abundance and diversity of the motile epifauna indicate that these species play an important role in hard-bottom communities.  相似文献   

10.
During the expedition ARK XI-2 with RV Polarstern in September/October 1995, a transect of samples was taken off East Greenland from the shelf down to about 1800 m depth by means of an epibenthic sledge and a giant box corer, in order to obtain information on epibenthic and endobenthic macrofauna. Within the epibenthic sledge catches, the Cumacea were the most numerous taxon with 32,123 (always calculated for 1000 m) specimens, followed by the Isopoda with 26,914 specimens, and Amphipoda with 20,900; Mysidacea and Tanaidacea were less important. Amphipoda were the most numerous taxon on the shelf, while with increasing depth Isopoda and especially Cumacea became increasingly important. Macrofauna analysed from the box-corer samples decreased in abundance with depth. The highest macrofaunal abundance was found on the shelf, with 8128 ind. m−2 (200 m); below this depth, density decreased from ≈2000 ind. m−2 (at 800 m) to ≈800 ind. m−2 (2000 m). Peracarid crustaceans and polychaetes were, next to bivalves, the most frequent. Polychaetes clearly dominated the shelf communities; their relative percentage decreased with increasing water depth while the relative percentage of Peracarida increased simultaneously. Interestingly, the highest number of peracarids in the epibenthic-sledge samples was reported from deep sea, while box-corer samples showed decreasing macrofaunal abundance with depth. The relative percentage of peracarids in the box-corer samples increased with depth, while in absolute numbers, peracarids from these samples were also highest on the shelf at about 200 m depth. Accepted: 14 February 1999  相似文献   

11.
Habitat complexity is one of the most important factors modulating species diversity. This feature comprises several interrelated attributes, such as number, size, and spatial arrangement of complexity‐forming elements. However, the separate and joint effects of these attributes on diversity and community structure are still not well understood. Here, we assess the relationships between several structural‐complexity attributes of the subantarctic kelp Lessonia flavicans and species richness, total abundance, and structure of kelp‐associated macrobenthic communities. We predicted that longer thalli and larger holdfasts favor greater species richness and total abundance of invertebrate organisms. To test the prediction, an observational sampling program was established in two sites of the Strait of Magellan. Uni‐ and multivariate analyses revealed both positive and negative effects of kelp structural‐complexity attributes on diversity. Holdfast diameter and maximum frond length, followed by thallus wet weight, had the strongest positive fits to species richness and total abundance; the number of stipes, on the other hand, was negatively associated with both response variables. Longer fronds were associated with greater abundances of spirorbid polychaetes. Larger holdfasts supported larger abundances of Nereididae and Terebelidae polychaetes and the limpet Nacella mytilina. Contrarily, kelps with longer fronds and more stipes supported fewer amphipods. In this way, we demonstrate that different dimensions of habitat complexity can have contrasting effects on diversity and community structure, highlighting the fundamental role of multiple dimensions of kelp habitat complexity for local biodiversity.  相似文献   

12.
Hydrodynamically unbiased colonization trays were deployed for 6 months (Oct. 2000 to April 2001) on the northern California margin (Eel R. region; 525 m) to examine macrofaunal colonization rates at methane seeps. The influence of sulfide on recruitment and survival was examined by deploying sediments with and without sulfide added; effect of seep proximity was evaluated by placing trays inside and outside seeps. The trays contained a two-layer system mimicking vesicomyid clam bed habitat geochemistry, with 8-9 mM sulfide in a lower agar layer at the start of the experiment. After 6 month on the seabed, the lower agar layer contained 2-4 mM H2S. We observed rapid macrofaunal colonization equivalent to 50% of initial non-seep ambient densities. There was no difference in total colonizer densities, number of species, or rarefaction diversity among 3 treatments: (1) controls (no sulfide added) placed outside seeps, (2) trays with sulfide added placed outside seeps and (3) trays with sulfide added placed inside seep patches. Colonization trays with sulfide placed at seeps had different species composition from trays without sulfide place outside seeps; there were more amphipods (non-ampeliscid) and cumaceans in the seep/sulfide treatment and more nemerteans, Nephtys cornuta and tanaids in the non-seep/no-sulfide treatment. Outside seeps, annelids comprised < 15% of tray colonists; within seep patches, annelids comprised 5 of the top 10 dominant colonizing taxa (24% of the total). The polychaetes Mediomastus sp., Aphelochaeta sp., Paraonidae sp., and Nerillidae sp. exhibited significantly higher densities in sulfide additions. Tanaids, echinoderms, and N. cornuta exhibited sulfide avoidance. At least 6 dorvilleid polychaete species colonized the experiments. Of these, 4 species occurred exclusively in trays with sulfide added and 80% of all dorvilleid individuals were found in trays with sulfide placed inside seep sediments. Counts of large sulfur bacterial filaments were positively correlated with maximum sulfide concentration in each tray, and with proximity of sulfide to the sediment surface. However, total macrofaunal densities were not correlated with tray sulfide concentrations. As a group, tray assemblages achieved some but not all characteristics of ambient seep assemblages after 6-month exposure on the sea floor. Distinctive colonization patterns at methane seeps contribute to the dynamic mosaic of habitat patches that characterize the eastern Pacific continental margin.Overall, proximity of seep habitats had at least as great an influence on macrofaunal colonization as tray sulfide concentrations. Taxa characteristic of seep sediments were more likely to settle into trays placed inside rather than outside seep patches. Whether this is due to limited dispersal ability or local geochemical cues remains to be determined.  相似文献   

13.
Epifauna living on sublittoral seaweeds around Cyprus   总被引:3,自引:2,他引:1  
Russo  Anthony R. 《Hydrobiologia》1997,344(1-3):169-179
Macroepifauna living on sublittoral seaweeds were counted,identified and compared among six locations in Cyprus. Mollusks,amphipods, and polychaetes were the major taxa represented. Thedominant alga was Cystoseira barbata which was present at 4of 6 stations and ranged in wet weight from 1–2 kg m-2 ofbottom. Percent cover of C. barbata ranged from 25 to 90%.Other dominant algae were Laurencia obtusa, Padinapavonica, and Jania rubens. The distribution of epifaunaabundance, species composition, and species richness varied amonglocations. Total epifauna abundance ranged from 1000 to 2250animals m-2. The abundance of epifauna per gram of plant wassignificantly lower on C. barbata than on the other algalspecies. The total epifauna species richness was more related tolocal algal plant diversity than to plant biomass.  相似文献   

14.
Summer phytoplankton blooms on the West Antarctic Peninsula (WAP) shelf result in episodic deposition of labile food material for benthic detritivores. This summer deposition is thought to enhance benthic recruitment of macro- and megafauna. To explore seasonality in benthic recruitment, juvenile invertebrates (>100 μm) were collected in a seasonal time series at three stations on the WAP continental shelf. 4,098 juveniles were collected (average densities 2,000–7,000 m−2), with polychaetes dominant (2,581 individuals). The majority of polychaetes showed evidence of enhanced recruitment prior to the summer bloom, although patterns varied across stations. Additional taxa showed recruitment peaks in summer, but again, patterns varied among stations. Based on observed patterns, polychaete taxa are classified as “seasonal”, “marginally seasonal”, and “non-seasonal” recruiters, with the latter two patterns predominating. The year-round presence of small juveniles in most taxa suggests that recruitment occurs continuously, with periodic enhancement. Year-round recruitment is consistent with the presence of a persistent “food bank” of labile organic material in WAP shelf sediments, allowing recruitment to be largely decoupled from seasonal bloom dynamics.  相似文献   

15.
The benthic assemblages in two Central Chile nearby embayments were studied from quantitative samples collected from 15 sites at depths of 8–65 m. The macrobenthic infauna (<0.5 mm) of both bays was greatly dominated by polychaetes. Some 93 taxa were identified, of which 51 were polychaetes. The average macrofaunal abundance for all stations (15,021 ind. m−2) is very close to the values reported for the neighboring areas. Numerical classification and ordination (DCA) of sites resulted in three site-groups mostly reflecting differences in the bottom sediments: the muddy-bottom stations of Concepción Bay and the shelf-associated stations, the sandy-bottom stations of San Vicente Bay and an heavily polluted station at San Vicente port. Classification of species showed that the muddy-bottom stations and the sandy-bottom sites had characteristic species assemblages. The macrofaunal assemblages presented high dominance values, which were due to the high numerical abundances of a few species in the collections.  相似文献   

16.
Macrozoobenthic soft-sediment communities of central Arctic Kongsfjorden inhabiting six depth zones between 5 and 30 m were sampled using SCUBA-diving during June–August 2003 and analysed comparatively. About 63 taxa were found, nine of which had not been reported for Kongsfjorden and four for Svalbard. Suspension feeding or surface and sub-surface detritivorous polychaetes and deposit-feeding amphipods were dominant. Only 11 of the 63 taxa (45 species and additional 18 families not further identified) inhabited the complete depth range. Biomass ranged from 3.5 to 25.0 g ash free dry mass m−2 and mean Shannon diversity (Log e) was 2.06. Similarity clustering from abundance and biomass data showed a significant difference between the shallow station (5 m) and the rest. The latter formed two sub-groups (10–20 and 25–30 m). Depth is irrevocably correlated with ice-scouring. Thus the differences in diversity together with the predicted iceberg scour intensity support the ‘intermediate disturbance hypothesis’ indicating that habitats impacted by moderate iceberg scouring enable higher diversity. In contrast, biotopes frequently affected only host pioneer communities, while mature, less diverse assemblages dominate depths of low impact.  相似文献   

17.
UW-video guided multibox corer sampling in- and outside iceberg scours provided quantitative macrozoobenthos samples for analyses of effects of grounding icebergs on infaunal benthic communities. These studies were performed on the southeastern Weddell Sea shelf off Kapp Norvegia and Austasen. Based on the UW-video sequences, stations were grouped a priori into two different "disturbance categories" and into undisturbed areas.Average biomass of major taxa in the cores of undisturbed areas was significantly higher (14,716.5 g wet weight m-2) than in old (405.3 g w. wt. m-2) or in young scour marks (9.2 g w. wt. m-2). The habitat taxon richness, too, was highest in undisturbed areas (on average, 11.8 taxonomic units occurred per core), decreased in old scour marks (9.0) and was lowest in young scours (6.8). In undisturbed areas, a higher developed community structure was reflected by a greater variety of taxonomic groups, some of which were principally absent in scours.In young scours, the number of taxa was significantly reduced. Motile forms such as echinoderms and crustaceans, mainly amphipods, and juvenile polychaetes, in particular pioneering species of the family Spionidae, started the recolonization of the devastated areas. Burrowing organisms occurred in older scours where the initially overcompacted sediment had softened. In the course of the re-establishment of macrofaunal communities (after some years/decades), the faunal composition is expected to change towards a "normal" dominance of suspension-feeding organisms, mainly sponges and bryozoans, being typical for wide areas on the southeastern Weddell Sea shelf.A more detailed taxonomical approach, using 167 polychaete species as representatives of the macrozoobenthos, also revealed significant differences between undisturbed and affected areas. The mean abundances (784, 389, and 242 ind. m-2, respectively), as well as habitat species richness (11.6, 5.5, and 3.1, respectively), decreased from undisturbed areas to old to young iceberg scours. Similarly, a large variety of motile and sessile forms was encountered among the polychaetes at undisturbed sites, whereas in scours, the polychaete fauna was impoverished in terms of species richness, abundance and variety of feeding types and lifestyles.  相似文献   

18.
The site specific impact on the benthic fauna was assessed within a 4.64 km2 area of intensive aquaculture situated on the eastern side of Hios island (Aegean Sea, Greece) at 11 stations seasonally between November 2000 and October 2001. The benthic fauna showed marked changes in species numbers, diversity and faunal abundance between farm and control sites. The polychaetes Nereis diversicolor, Scolelepis fuliginosa and Capitella capitata were the most dominant species at the farm sites (35% of the total abundance), whilst the most dominant species at the control sites were the polychaete Hyalinoecia brementi and the sipunculid Aspidosiphon muelleri (23% of the total abundance). Species richness, diversity and evenness were higher at the control sites whereas numerical abundance was higher at the farm sites. K-dominance curves suggest a minor impact on the benthic community at the farm sites and temporal changes on macrobenthic assemblages.  相似文献   

19.
深圳湾潮间带1995-2010年大型底栖动物群落的时空变化   总被引:5,自引:0,他引:5  
本文根据1995-2010年在深圳湾潮间带5条断面采集的大型底栖动物数据,分析了群落的物种数、栖息密度、多样性指数(H)、丰度指数(d)和多变量海洋底栖生物指数(M-AMBI)的时空变化.结果表明,物种数、多样性指数、丰度指数和多变量海洋底栖生物指数存在明显的空间差异,即距离深圳河口越近,大型底栖动物物种数越少,多样性指数、丰度指数和多变量海洋底栖生物指数越低.空间差异还体现在越靠近深圳河口的取样断面,大个体物种,如羽须鳃沙蚕(Dendronereis pinnaticirris)和腺带刺沙蚕(Neanthes glandicincta)的栖息密度越低,而小个体、生命周期短的小头虫(Capitella capitata)和寡毛类动物栖息密度所占的比例越高,丰度生物量比较(abundance biomass comparison,简称ABC)法证实了深圳湾潮间带大型底栖动物群落的空间差异.造成这种差异的原因推测是由于深圳市人口的增加和工、农业的发展,排入深圳河的污水量增加,导致距离深圳河越近,有机质含量越高.大型底栖动物群落的物种数、栖息密度、多样性指数、丰度指数、多变量海洋底栖生物指数的年和季节变化各不相同,没有明显的变化趋势.  相似文献   

20.
A survey was conducted during 2002, 2003 and 2004 to determine the leafhopper species composition, abundance, richness, diversity, evenness, occurrence and flight activity among three coffee production zones of Costa Rica. Yellow sticky traps were used to qualify and quantify the number of aerial leafhoppers during the sampling period. A total of 82,500 individuals, belonging to 139 species within nine leafhopper subfamilies, were trapped. San Isidro de León Cortés site presented the highest diversity from the three surveyed sites. Twenty five species were frequently trapped at least in one of the studied zones, and only Coelidiana sp.1, Osbornellus sp.1, Scaphytopius sp.1 and Empoasca sp. were trapped throughout the sampling period. The flight activity of the taxa that contain the main vectors of Xylella fastidiosa Wells et al. showed differences among the sampling zones.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号