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1.
The benthic response to a plume front was studied in two areas of the northern Adriatic (Mediterranean Sea) differently influenced
by the Po River freshwater input. Sediment samples were collected in June 1996 and February 1997 from 12 stations. The adopted
sampling strategy was able to identify the front line in real time by satellite images and to locate sampling stations along
an inner–outer plume gradient in order to cover the benthic area beneath the river plume, where enhanced biological production
was expected, and open-sea sediments not directly influenced by freshwater inputs. Meiofaunal parameters were compared to
the physical conditions and to phytodetritus inputs, organic matter accumulation and bacterial secondary production. The sediments
of the Adriatic Sea were characterised by high concentrations of phytopigments (0.6 to 13.9 μg g−1 for chlorophyll a and 1.2 to 17.7 μg g−1 for phaeopigments) and biopolymeric organic carbon (0.15 to 3.02 mg g−1). The plume system extended for a large sector of the northern Adriatic. In the northern area, a large and highly dynamic
plume area was coupled with a sediment organic matter concentration significantly higher than in open-sea sediments. In the
southern sector, where the plume area and the front line did not change markedly during the year, plume–benthic coupling was
evident only in the sediments beneath the front, and corresponded to phaeopigment accumulation. Bacterial parameters and secondary
production were high and significantly higher in the frontal area than at open-sea stations. Meiofauna density (1342 to 8541
ind. 10 cm−2) did not change either by season or between areas and was significantly correlated with phaeopigments and bacterial secondary
production. Meiofauna displayed different responses to plume inputs in the two sampling areas. In the northern sector, meiofauna
density was coupled with organic matter distribution and displayed highest values beneath the plume. In the southern sector,
the densities of copepods, turbellarians and kinorhynchs displayed highest values under the front in summer, and the same
applied to total meiofauna density in winter. Juvenile decapods and copepod nauplii significantly increased their densities
in sediments beneath the front. Data presented in the present study suggest that plume inputs and frontal systems, enhancing
phytodetritus accumulation and benthic bacterial response, might influence density, composition and distribution of meiofaunal
assemblages. As river plumes are highly variable systems affecting the trophic characteristics of the sediments underneath,
their dynamics should be considered when analysing mesoscale spatial changes of meiofaunal assemblages.
Received: 30 November 1999 / Accepted: 24 May 2000 相似文献
2.
Mega-epibenthic communities in Arctic and Antarctic shelf areas 总被引:4,自引:0,他引:4
Mega-epibenthic shelf assemblages were investigated off Northeast Greenland and in the Weddell, Bellingshausen and Amundsen
Seas in the Antarctic using underwater video. In the Arctic a total of 94 taxa represented by more than 100 000 individuals
were identified. Echinoderms, particularly brittle stars, were the most important elements of the mega-epibenthic fauna on
the shelf off Northeast Greenland. Multivariate analyses of the species distribution revealed a conspicuous depth zonation
in which an assemblage on the shallow banks can be clearly distinguished from that in the troughs. Between these a transitional
zone with a heterogeneous benthic fauna was found. Physical disturbances are supposed to be responsible for the pronounced
dominance patterns observed on the shallow banks. The fauna in the troughs, which consists of more than 50% suspension feeders,
is diverse but low in numbers of individuals. In the Antarctic more than 115 000 individuals belonging to 169 taxa were analyzed.
Obvious faunal differences exist between the stations in the Weddell Sea and the Bellingshausen/Amundsen Seas. Assemblages
of suspension feeders dominated by sponges and bryozoans are prevalent on the shelf of the eastern Weddell Sea, but almost
absent in the Bellingshausen and Amundsen Seas. These assemblages seem to be restricted to areas where bottom currents provide
favourable feeding conditions. However, motile deposit feeders are more abundant in both regions where there is a soft bottom
substrate with presumably slow bottom currents and reduced horizontal transport of organic particles.
Received: 22 January 1999 / Accepted: 7 June 1999 相似文献
3.
The application of predicted habitat models to investigate the spatial ecology of demersal fish assemblages 总被引:1,自引:0,他引:1
Benthic habitats are known to influence the abundance and richness of demersal fish assemblages; however, little is known
about how habitat structure and composition influences these distributions at very fine scales. We examined how the benthic
environment structures marine fish assemblages using high-resolution bathymetry and accurate predicted benthic habitat maps.
Areas characterised by a mosaic of habitat patches supported the highest richness of demersal fishes. A total of 37.4% of
the variation in the distribution of the fish assemblage was attributed to 6 significant variables. Depth explained 23.0%
of the variation, with the boulders explaining 12.6% and relief 1.4%. The remaining measures (seawhips, light/exposure and
solid reef) provided a small (<1.0%) but significant contribution. Identifying components of the benthic environment important
in structuring fish assemblages and understanding how they influence the spatial distribution of marine fishes is imperative
for better management of demersal fish populations. 相似文献
4.
Kevin P. Robinson Michael J. Tetley E. Gay Mitchelson-Jacob 《Journal of Coastal Conservation》2009,13(1):39-48
The coastal waters of the Moray Firth in northeast Scotland (57o41’N 2o40’W) provide rich, inshore feeding grounds for minke
whales (Balaenoptera acutorostrata) during the summer and autumnal months. In order to better understand the habitat selection, movements and feeding ecology
of the animals utilising this North Sea region, distribution data from the southern coastline of the outer Moray Firth were
subsequently examined with respect to the marine physiography of the area, specifically the environmental variables water
depth, slope, aspect and sediment-type. A total of 305 minke whale encounters – collected from dedicated boat surveys conducted
between May and October 2001 to 2006 inclusive – were used in the construction of a Geographic Information System (GIS) for
the 860 square-km study site. The subsequent analysis revealed a strong spatial preference by whales in this location for
water depths between 20 and 50 metres (mean 46.9 m, SD = 30.9), steep slopes (mean 75.7 degrees, SD = 8.9), a northerly-facing
aspect and sandy-gravel sediment type. Kruskal-Wallis tests for variance confirmed that the distribution of B. acutorostrata was significantly different across each of these physiographic features examined (P < 0.05). In particular, water depth and sediment type were shown to be highly correlated with the frequency of whales observed
(Spearman’s Rank Correlation P < 0.05 for depth and sediment respectively). From these results, we conclude that sea bottom characteristics may be used to
predict the fine-scale distribution of minke whales on their feeding grounds; the physiographic features identified providing
valuable proxies for inferring prey distributions in the absence of fisheries data. However, an appreciation of both abiotic
and biotic factors (using a combination of GIS and remote sensing outputs) is clearly desirable for ecosystem-based management
approaches for the coastal conservation of these whales. The application of GIS capacities to ecological studies based largely
on field data of these marine mammals is highly recommended in the present study to cetologists, environmental modellers and
conservation managers alike. 相似文献
5.
The wedge sole Dicologlossa cuneata (Moreau, 1881) is a coastal species that lives along the inner shelf waters of the Gulf of Cadiz down to a depth of 115 m.
Its fishery, the size composition of the exploited population, and its reproduction have been studied on the basis of data
acquired from commercial statistics from 1984 to 1994 and from sampling carried out during 1993 and 1994. The relative abundance
of the species and its geographic and bathymetric distribution have been examined by analysis of four trawl surveys carried
out from 1992 to 1994. D. cuneata is captured mainly by the trawl fleet, and to a lesser extent by gillnet gears. Wedge sole fishery has a marked seasonality.
Size-frequency distributions from commercial samples and from bottom-trawl surveys are very similar, ranging from 12 to 26 cm
total body length (TL). D. cuneata is a “repeat-spawner”. Peak spawning is from January to May. Females attain sexual maturity at 18 cm TL, while sexually mature
males have been observed at 15 cm TL. The flexibility of the spawning strategy of D. cuneata throughout its distribution range is discussed. The scarcity of small specimens in the monthly samples and sequential spawning
throughout the year prevented the estimation of growth parameters by means of length-frequency analysis. D. cuneata is present in greatest abundances in the sandy–muddy bottoms of the Guadalquivir River mouth at 15 to 30 m depth. Its optimum
habitat coincides with the principal commercial fishing grounds. The possibility of reproductive vertical migration is discussed,
but more precise data are needed before a viable hypothesis can be made.
Received: 1 July 1997 / Accepted: 27 November 1997 相似文献
6.
The southern Great Barrier Reef (GBR), a region that rarely experiences cyclones, was impacted by tropical cyclone (TC) Hamish
in March 2009. We documented on-reef physical and habitat conditions before, during and after the cyclone at One Tree Reef
(OTR) using data from environmental sensor instrumentation and benthic surveys. Over 5 years of monitoring, ocean mooring
data revealed that OTR experienced large swells (4–8 m) of short duration (10–20 min) not associated with a cyclone in the
area. These swells may have contributed to the physical disturbance of benthic biota and decline in coral cover recorded prior
to and after TC Hamish. During the cyclone, OTR sustained southeasterly gale force winds (>61.2 km h−1) for 18.5 h and swells >6 m in height for 4 h. Benthic surveys of exposed sites documented a 20% drop in live coral cover,
30% increase in filamentous algae cover and the presence of dislodged corals and rubble after the storm. Leeward sites were
largely unaffected by the cyclone. Benthic cover did not change in the lagoon sites. Significant rubble movement and infill
of the lagoon occurred. Two years after the cyclone, algal cover remained high and laminar corals had not recovered. Total
coral cover at impacted sites had continued to decline. Environmental conditions and habitat surveys supported Puotinen’s
(Int J Geogr Inf Sci 21:97–120, 2007) model for cyclone conditions that cause reef destruction. While TC Hamish had a major impact on the reef, change in benthic
cover over several years was due to multiple stressors. This on-reef scale integration of physical and biological data provided
a rare opportunity to assess impacts of a major storm and other disturbances, showing the importance of considering multiple
stressors (short-lived and sustained) in assessing change to reef habitats. 相似文献
7.
8.
In recent years the pace of exotic species introduction and invasion has accelerated, particularly in estuaries and wetlands.
Species invasions may affect coastal ecosystems in many ways. Alteration of sedimentary environments, through structure formation
and burrowing, has particularly dramatic effects on coastal habitats. This study examines modification of channel bank and
marsh edge habitat by the burrowing Australasian isopod Sphaeroma quoyanum Milne Edwards, in created and natural salt marshes of San Diego Bay and San Francisco Bay. Abundance and distribution patterns
of this isopod species, its relationships with habitat characteristics, and its effects on sediment properties and bank erosion
were examined seasonally, and in several marsh microhabitats. Mean isopod densities were 1541 and 2936 individuals per 0.25 m2 in San Francisco Bay, and 361 and 1153 individuals per 0.25 m2 in San Diego Bay study sites during December and July 1998, respectively. This isopod forms dense, anastomosing burrow networks.
S. quoyanum densities did not differ as a function of location within creeks or location in natural versus created marshes. Burrows,
which are on average 6 mm wide and 2 cm long, were associated with firm sediments containing high detrital biomass. Although
erosion is a natural process along salt marsh banks, enclosure experiments demonstrated that isopod activities can enhance
sediment loss from banks. In areas infested with S. quoyanum, losses may exceed 100 cm of marsh edge per year. The effects of habitat alteration by this invading species are likely to
increase in severity in the coastal zone as these ecosystems become degraded.
Received: 30 March 2000 / Accepted: 21 September 2000 相似文献
9.
We investigated the effect of different densities of the burrowing deposit-feeding amphipod Monoporeia affinis on the potential for recruitment of zooplankton from benthic resting eggs. Hatching of resting eggs was induced in the laboratory
on sliced and resuspended 1-cm depth-sections of sediment cores, collected at six stations in an archipelago area of the Gulf
of Bothnia, Baltic Sea. The uppermost 5 cm of the sediment was studied. The most common species that hatched was Eurytemora affinis (Copepoda). Individuals from another copepod genus, Acartia, hatched in significant numbers only in the cores from two stations with low amphipod abundance. Cores from stations with
high amphipod densities showed a deeper distribution of emerging E. affinis nauplii compared with stations with few amphipods; the oxidised sediment layer was also deeper at high M. affinis densities than at low. Total (0 to 5 cm strata pooled) number of hatched E. affinis nauplii was independent of amphipod density. This indicates that the effect of M. affinis on E. affinis eggs involves deeper burial due to bioturbation, rather than predation. Decreased benthic recruitment of zooplankton at localities
with high M. affinis density is suggested, since more deeply positioned eggs are less likely to hatch. When hatching was induced in intact, non-sliced
cores from one station, the number of E. affinis nauplii that hatched was on average 43% of the number that hatched in the upper centimetre of the sliced cores from the same
station. This fraction (43%), if applied to the other stations, implied a potential for benthic recruitment of up to 80 000 ind
m−2 for E. affinis. Due to its high abundance, M. affinis is likely to greatly reduce benthic recruitment of zooplankton in this system.
Received: 17 September 1999 / Accepted: 23 February 2000 相似文献
10.
Alexis Ramfos Stamatina Isari Stylianos Somarakis Dimitris Georgopoulos Constantin Koutsikopoulos Nina Fragopoulu 《Marine Biology》2006,150(1):29-44
Depth-stratified samples, collected during a period where the water column was vertically mixed (March 2000) and a period of thermal stratification (September 2000), were analyzed in order to investigate the horizontal and vertical distribution patterns and composition of mesozooplankton, especially copepod species assemblages, in a pelagic (Ionian Sea) and a coastal area (Patraikos Gulf) of the eastern Mediterranean. Total mesozooplankton abundance and biomass were significantly lower in the highly oligotrophic offshore waters of the Ionian Sea when compared to the semi-enclosed Patraikos Gulf during both seasons. Small-sized copepods dominated the mesozooplankton community. An ‘offshore’ and a ‘coastal’ copepod assemblage were defined in the surface layer (0–50 m) only during March when differences in environmental conditions (i.e., temperature, salinity and fluorescence) were strong between the two areas. Copepod vertical community structure in offshore waters differed between sampling months. In March one assemblage (0–200 m) was mainly identified, while in September three distinct assemblages (0–50, 50–100 and 100–200 m) were observed, related to different vertical distribution patterns of the various copepod species. A pronounced seasonal change of the dominant copepods was evident in the surface layer, where strong differences in hydrological properties were observed from March to September. Below this layer, the copepod community was relatively stable showing decreasing seasonal differences with increasing depth. 相似文献
11.
M. Shah Nawaz Chowdhury M. Shahadat Hossain Nani Gopal Das Prabal Barua 《Journal of Coastal Conservation》2011,15(1):163-180
The Naaf River estuary is one of the large estuaries in the Bangladesh coastal region not to have been affected by extensive
human disturbance. This research provides information about the fisheries diversity status by Estuarine Set Bag Net (ESBN)
sampling relation to physicochemical variables in both spatio-temporal scales. About 25 km of the lower estuary was divided
into six zones for sample collection by considering the accessibility and availability of the ESBN operation, fish landing
centers and location of the fishing villages. In total 48 samples have been analyzed which were taken throughout March to
October 2006. To quantify the species diversity, all fisheries data were analyzed by using EstimateS and EcoSim software which
accounts the different diversity indices viz., species richness, Shannon–Wiener diversity Index, Dominance and Evenness index.
The research results demonstrate that the Naaf River estuary is a habitat of 161 (species richness, Sobs = 161, Choa 1 = 162 ± 2.34,
ACE = 161.73) different species which belong to 98 fin fishes, 23 shrimps and prawns, 13 crabs, 11 molluscs, 3 echinoderms,
4 other crustaceans; while 9 remain unidentified. Results on the aquatic environment, mainly salinity and turbidity were found
to have a major influence on their occurrence and distribution. All the findings indicated that the Naaf River estuary is
a highly productive system and provides a favourable environment for large variety of estuarine species assemblages. 相似文献
12.
The structure of megabenthic decapod crustacean assemblages on the Galician (north-west Spain) continental shelf (100 to
200 depth) and upper slope (200 to 500 m) was analyzed based on surveys carried out in autumn and spring, from 1980 to 1987.
Forty species belonging to 19 families were caught. The portunid crab Polybius henslowii, a species with pelagic phases, was the most abundant species, but displayed strong spatial and temporal fluctuations. Other
dominant species were the Norway lobster Nephrops norvegicus, the portunid Liocarcinus depurator, the galatheids Munida intermedia and M. sarsi, and the shrimps Solenocera membranacea, Plesionika heterocarpus, Pasiphaea sivado and Dichelopandalus bonnieri. Total abundance and biomass (average values excluding Polybius henslowii = 255 individuals and 2.06 kg/30 min tow) and species richness and diversity, H′ (6.85 species and H′ = 1.45 per tow) displayed a significant positive correlation with depth, and strong interannual fluctuations. The factors
determining community organization were depth and, to a lesser extent, spatial structure. There was clear evidence of bathymetric
zonation, differentiating between species characteristic of the slope (D. bonnieri and Pasiphaea sivado), shelf-slope edge (Macropipus tuberculatus, Pontophilus spinosus, Munida sarsi, S. membranacea, Processa spp.) and shelf (L. depurator, Macropodia tenuirostris, Paguridae and Chlorotocus crassicornis). The spatial zonation was related to changes in oceanography and sediment along the continental margin. Goneplax rhomboides, N. norvegicus, C. crassicornis and Alpheus glaber are benthic species which generally exhibit burrowing behaviour, and they were found mainly in the southern area where there
are fine sediments due to the outwelling from the Rías Baixas. Different benthopelagic shrimps (Pontophilus spinosus, Plesionika heterocarpus,Processa spp. and Pasiphaea sivado) were typical of the zone just north of Fisterra, characterized by a convergence of water masses bringing about an increase
in productivity due to upwelling. The benthic anomuran and brachyuran crabs Munida intermedia, M.␣sarsi, L.␣depurator and Macropipus tuberculatus were characteristic of the northwestern zone between Fisterra and Estaca, where the infauna reaches high biomass despite
coarser sediments with a lower concentration of organic material than in the southern area. Lastly, both the Paguridae and
Macropodia tenuirostris were species typically found in the waters in the northern shelf. Based on interannual changes in assemblage structure, two
periods could be distinguished: between 1980 and 1984, when Polybius henslowii, D. bonnieri and Pasiphaea sivado had abundance peaks; and another period from 1985 to 1987 when L. depurator, Munida intermedia, M.␣sarsi and Macropipus tuberculatus increased in abundance.
Received: 21 May 1996 / Accepted: 9 August 1996 相似文献
13.
Analysis of the structure of decapod crustacean assemblages off the Catalan coast (North-West Mediterranean) 总被引:4,自引:0,他引:4
We sampled the communities of decapod crustaceans inhabiting the depth zone between 3 and 871 m off the Catalan coast (North-West Mediterranean) from June 1981 to June 1983. The 185 samples comprised 90 species differing widely in their depth distributions. Multivariate analysis revealed four distinct faunistic assemblages, (1) littoral communities over sandy bottoms, (2) shelf communities over terrigenous muds, (3) upper-slope communitics, and (4) lower-slope or bathyal communities. The brachyuran crab Liocarcinus depurator is the most abundant species of the shelf assemblage, although L. vernalis dominates over the shallow sandy bottoms of the shelf. The dominant species of the upper-slope assemblage are nektobenthic species (Solenocera membranacea, Plesionika heterocarpus, Processa canaliculata), pelagic species (Pasiphaea sivado, Sergestes arcticus), and benthic species (Macropipus tuberculatus, Munida intermedia, Nephrops norvegicus). Aristeus antennatus comprise most of the biomass of the lower-slope community, which supports a greater diversity than the other assemblages. The main assemblages appear to be related to different hydrological characteristics, the extent of seasonal fluctuations, and to the changes in sediment structure associated with changes in the steepness of the bottom. 相似文献
14.
The distribution and abundance of Japanese common squid [Todarodes pacificus (Steenstrup, 1880)] paralarvae off southern Kyushu Island near the Kuroshio were examined in relation to water types in the
region. Surveys were conducted in 1996 and 1997 using paired, 70 cm diameter Bongo nets. Temperature–salinity plots from 0,
50 and 100 m depths were used to assign sampling stations to three water types: inshore, mixing and Kuroshio. In total, 4103
T. pacificus paralarvae were collected at 59 of 72 stations. Catch densities at positive stations ranged between 8 and 4282 ind./50 m2 sea surface area. Catches during both years were highest in mixing waters, followed by inshore and Kuroshio waters. Total
catches were highest just north of the oceanographic front at the inshore edge of the Kuroshio and declined with increasing
distance away from the front. Catches of paralarvae ≤1.0 mm mantle length also peaked near the front. In both years, ≥85%
of all paralarvae and ≥69% of those ≤1.0 mm mantle length occurred less than 25 km from the front. We conclude that most spawning
off southwest Kyushu occurs near the frontal zone, where Kuroshio and inshore waters meet.
Received: 18 November 1998 / Accepted: 11 May 1999 相似文献
15.
Biomass partitioning of benthic microbes in a Baltic inlet: relationships between bacteria, algae, heterotrophic flagellates and ciliates 总被引:6,自引:0,他引:6
The structure of a benthic microbial food web and its seasonal changes were studied in the shallow brackish waters of the
island of Hiddensee, northeastern Germany, at two sites in close proximity by monthly or bimonthly sampling from July 1995
to June 1996. Abundance and biomass of phototrophic and non-phototrophic bacteria, heterotrophic flagellates (HF) and ciliates
as well as the biomass of microphytobenthos were determined in the upper 0.3 cm sediment layer. Abundance of organisms showed
strong positive correlation with water temperature, with the exception of the bacteria. Non-phototrophic bacterial numbers
ranged from 7 × 108 to 6.7 × 109 cells cm−3 and phototrophic bacterial abundance from 4 × 107 to 2.7 × 108. Heterotrophic protist abundance ranged from 8 × 103 to 104 × 103 ind cm−3 for HF and from 39 to 747 ind cm−3 for ciliates. The biomass partitioning demonstrated the primary importance of non-phototrophic bacteria (min. 0.83, max.
84.87 μg C cm−3), followed by the microphytobenthos (min. 1.32, max. 50.93 μg C cm−3). The heterotrophic protists contributed roughly the same fraction to the total microbial biomass, with the biomass of the
HF being slightly higher (HF 0.23 to 1.76 μg C cm−3, ciliates 0.04 to 1.17 μg C cm−3). Taxonomic classification of the benthic HF revealed the euglenids to be the most important group in terms of abundance
and biomass, followed by thaumatomastigids and kinetoplastids. Other important groups were apusomonads, cercomonads, pedinellids
and cryptomonads. The structure of the HF assemblage showed strong seasonal changes with euglenids being the most abundant
taxa in summer, while apusomonads and thaumatomastigids were predominant in winter. Similar to the pelagic microbial food
web, benthic picophototrophic bacteria were occasionally abundant, and the feeding modes of heterotrophic protists exhibited
a great variety (predominantly omnivores, bacterivores, herbivores or predators). Filter-feeding HF were of little importance.
Contrary to the pelagic environment, a top-down control on total benthic bacterial numbers by HF seemed unlikely at the studied
stations which were characterised by muddy sand.
Received: 6 January 1999 / Accepted: 21 October 1999 相似文献
16.
The surface sediment characteristics related to benthic microalgae primary production were studied at the Dogger Bank, North
Sea, in order to evaluate the potential role of microphytobenthos as a food source for the macrobenthic fauna. Twenty-one
stations were sampled in July 2001 and May 2002, with water depth ranging from 16.3 to 68.5 m. High-performance liquid chromatography
pigment analyses revealed that concentrations of chlorophyll a, chlorophyll c and fucoxanthin are mainly associated with benthic diatom flora at most parts of the Dogger Bank. High percentage of phytopigments
(>50%) was firmly attached to sand grains at the stations shallower than 40 m water depth. The deeper stations were characterized
by a phytopigment composition originating from pelagic phytoplankton settled on the sea floor. Qualitative microscopy showed
that the benthic microflora on top of the Bank mainly consists of small diatoms (5–10 μm), such as e.g., Diploneis spp., living attached to the sand grains. The results are discussed concerning possible implications for ecology and biogeochemistry
of the Dogger Bank area. 相似文献
17.
Western sandpiper (Calidris mauri) predation was examined by concurrent experiments and direct observations of foraging behaviour on high intertidal mudflats
of the Fraser River estuary, British Columbia. Western sandpipers foraged by either “pecking” on the surface (64% of observational
time) or probing into sediment (29%). The first experiment (probe-mark method) consisted of collecting small-volume cores
(21.2 cm3) of probed (experimental) and non-probed (control) sediment on the tidal flat, following a 22.5-min feeding period. The second
experiment (exclosure method) involved deploying exclosures immediately prior to the feeding period and subsequent collection
of cores from inside (control) and outside (experimental) the exclosures. Sediment cores were analysed for both macrofaunal
and meiofaunal size fractions. Comparisons between macro- and meiofaunal invertebrate densities in experimental and control
sediments revealed significant differences, attributed to shorebird predation, for both experiments. The probe-mark experiment
detected the removal of large infaunal polychaetes (∼ 20 mm), while the exclosure experiment showed depletion of epifaunal
harpacticoid copepods (0.063–0.5 mm). Predation on macrofaunal cumaceans was detected in both experiments. Invertebrates selected
by western sandpipers neither fell within traditional infaunal size classifications (macro- vs. meiofauna; 500 μm delineation)
nor corresponded to the highest densities of taxa. Rather, inference from experimental results and observations is that western
sandpipers forage in two modes, by: (1) surface gleaning of epibenthic copepods and cumaceans in the macro- and meiofaunal
size ranges and (2) selective probing for larger infauna, such as polychaetes. These findings were facilitated by the combination
of methodologies employed.
Received: 29 December 1999 / Accepted: 11 September 2000 相似文献
18.
For much of the last century the developmental mode of marine invertebrates, particularly of prosobranch gastropods, has
been thought to reflect a latitudinal pattern known as Thorson's rule; the proportion of species with pelagic larvae decreases
with increase in latitude. Although the predictions of this rule have been criticized recently, its validity along latitudinal
transects in the world ocean still remains poorly tested. In the present work, we compare the frequency of occurrence of contrasting
prosobranch hatching modes (pelagic versus benthic development) along two latitudinal gradients of the subequatorial coastline
of South America: the southeast Pacific and the southwest Atlantic. The results are clearly contrasting. While the pattern
observed along the Pacific (Chilean) coast fits the predictions of Thorson's rule very well, benthic development predominates
all along the Atlantic coast, even at subtropical latitudes. This difference in observed patterns is attributable to the different
compositions of the gastropod assemblages on each side of the South American continent, which are determined, in turn, by
differences in the ecological conditions on the two sides of the continent. The scarcity of pelagic development among the
Atlantic prosobranch gastropods reflects the near-continuous soft-bottom habitat there, and the consequent prevalence of predaceous,
soft-bottom taxa that had acquired in their evolution more evolved, non-pelagic patterns of development. In contrast, the
Pacific coast is much more heterogeneous, with a diverse mixture of benthic habitats, including rocky substrates that, in
part, support grazing taxa. Our results indicate that two factors are important for Thorson's rule to be valid. First, the
habitat needs to include rocky substrates, as soft-bottom habitats appear to favour non-pelagic development. Second, a diverse
assemblage of taxa need to be compared to avoid the problem of phyletic constraints, which could limit the evolution of different
developmental modes.
Received: 23 May 2000 / Accepted: 13 October 2000 相似文献
19.
The distribution and enrichment of selected trace metals (Cd, Cr, Cu, Ni, Pb, Sn, Zn) in benthic sediments of the Southport
Broadwater, a semi-enclosed coastal body of water adjacent to the Gold Coast city, south-eastern Queensland, Australia, was
studied with the objective of assessing the extent and degree of sediment contamination. Sediment samples from the 0–10 cm
and 10–20 cm depth intervals of 32 sites within the Southport Broadwater and surrounding residential canals were analysed
for particle size distribution, pH, organic C and ‘near-total’ major (Al, Ca, Fe, Mn) and trace (Cd, Cr, Cu, Ni, Pb, Sn, Zn)
metal contents. Sediment contamination for each trace metal was assessed by (1) comparison with Australian sediment quality
guidelines, (2) calculation of the index of geoaccumulation based on regional background values, and (3) geochemical normalisation
against Al (i.e. the abundance of alumino-silicate clay minerals). Based on this approach, the results indicate that submerged
sediments in the study area are not presently enriched with Cd, Cr or Ni, with the spatial distribution of these metals being
very well explained by the abundance of alumino-silicate clay minerals. However, several sites were strongly enriched with
Cu, Pb, Sn and Zn, arising from sources related to either urban runoff or vessel maintenance activities. The study indicates
that several varying approaches are needed for a satisfactory assessment of contaminant enrichment in estuarine sediments. 相似文献
20.
Mudball-building cirratulid polychaetes have been described previously only from the southern California margin. During a
study of oxygen minimum-zone benthos in fall 1994, we observed dense aggregations of agglutinated mudballs at 840 to 875 m
on the Oman margin in the northwest Arabian Sea. These were inhabited, and probably constructed, by a cirratulid polychaete
species in the genus Monticellina. The mudballs were cigar-shaped, 4.5 to 25 mm long, and positioned vertically so as to protrude several millimeters above
the sediment–water interface. Total mudball densities were ∼16 000 m−2. Occupied mudballs occurred at densities of 2 112 m−2; 89% were in the uppermost 2 cm of sediment, and no occupied mudballs were found below 10 cm. Organisms other than the cirratulid
were present on 1.7% of the mudballs examined, and included epizoic polychaetes, agglutinated and calcareous Foraminifera.
Various polychaetes, a nemertean and nematodes were found inside tests. Mudball abundance exhibited positive associations
with densities of several paraonid polychaete species, and with densities of burrowing and subsurface-deposit-feeding polychaetes.
Negative associations were observed between mudballs and three tube-building taxa (two polychaetes and an amphipod). Mudball-inhabiting
cirratulids are abundant in at least two low-oxygen, margin settings. We expect further sampling of bathyal environments to
yield additional systems in which cirratulid mudballs are common. Such observations are valuable because mudballs appear to
represent a significant source of heterogeneity that can influence macrofaunal community structure in deep-sea sediments.
Received: 15 January 1997 / Accepted: 30 January 1997 相似文献