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1.
Reproductive success among clonal taxa is often portrayed as a simple function of clone size, but reproduction in Pseudoplexaura porosa (Houtuyn), a common Caribbean gorgonian, reflects a more complex relationship between size and gamete production. Tagged
colonies were sampled at two reefs in the San Blas Islands, Panama during the 1995 spawning season to determine the colony
size at first reproduction, size-dependent polyp fecundities, and whole colony gonad production, and to follow the gametogenic
cycle. Additional data were obtained during non-spawning months in 1984 and 1985. Of 120 colonies ranging in height from 20
to 250 cm, only colonies taller than 50 cm were reproductive. An average of 4.33 oocytes polyp−1, 560 to 800 μm in diameter, were released during monthly synchronous spawning events from June to September. Oocytes released
each month developed from a group of intermediate size oocytes present at the end of the preceding month. Almost all oocytes
>560 μm were released during each spawning event. Spermatogenesis was a shorter process than oogenesis. During each spawning
month, mature spermaries developed from a group of <125 μm spermaries. Virtually all spermaries >190 μm were released each
month, and most of the spermary volume in mature male polyps was generated anew each month of spawning. Among reproductive
colonies, polyp fecundity increased with colony height from 50 to 200 cm. Per capita fecundity of >200 cm tall female colonies
was lower than for 150 to 200 cm colonies, but whole colony fecundity of large colonies was greater due to the exponential
increase in the number of polyps that occurs with increasing colony height. In male colonies, both polyp and colony reproductive
output increased with colony height. The large amounts of sperm produced by large male colonies probably contributes to the
high rates of in situ fertilization observed in P. porosa. Differences in fecundity as a function of colony size and sex suggest differences in some combination of the cost of reproduction
and/or allocation of resources to reproduction.
Received: 9 September 1998 / Accepted: 7 June 1999 相似文献
2.
Myong Hwan Sohn Kyung Won Seo Yong Seok Choi Sang Joon Lee Young Sil Kang Yang Soon Kang 《Marine Biology》2011,158(3):561-570
The marine dinoflagellate Cochlodinium polykrikoides is a harmful and highly motile algal species. To distinguish between the motility characteristics of solitary and chain-forming
cells, the swimming trajectories and speeds of solitary cells and 2- to 8-cell chains of C. polykrikoides were measured using a digital holographic particle tracking velocimetry (PTV) technique. C. polykrikoides cells exhibited helical swimming trajectories similar to other dinoflagellate species. The swimming speed increased as the
number of cells in the chain increased, from an average of 391 μm s−1 (solitary cells) to 856 μm s−1 (8-cell chain). The helix radius R and pitch P also increased as the number of cells in the chain increased. R increased from 9.24 μm (solitary cell) to 20.3 μm (8-cell chain) and P increased from 107 μm (solitary cell) to 164 μm (8-cell chain). The free thrust-generating motion of the transverse flagella
and large drag reduction in the chain-forming cells seemed to increase the swimming speed compared to solitary cells. The
measured swimming speeds agreed with those from field observations. The superior motility of chain-forming C. polykrikoides cells may be an important factor for its bloom, in addition to the factors reported previously. 相似文献
3.
Four species of gymnamoebae isolated from a sandy shore were subjected to physical disturbance within sand microcosms containing
either 250 or 125 μm sand. Firstly, the effect of two different strengths of physical disturbance on amoebae populations within
sand was investigated. Secondly, whether the size of sand grains occupied by amoebae populations changed their response to
disturbance events was assessed. Highest abundances of amoebae were recorded in control flasks containing 125 μm sand. Increasing
the strength of disturbance decreased the abundance of all four species. Abundances of the two smallest isolates (Platyamoeba sp. and a limax amoeba) were least affected by increasing disturbance. The greatest decrease in abundance was observed in
populations of two larger (>15 μm) Mayorella sp. and Vannella sp. The greatest impact of physical disturbance was seen on populations within 250 μm sand. This study shows that physical
disturbance may be an important community structuring force within natural marine gymnamoebae communities. 相似文献
4.
To determine how fertilisation varied with sperm concentration for two species of scallop, Chlamys (Equichlamys) bifrons (Lamarck) and C. asperrima (Lamarck), we performed a simple series of sperm dilution experiments, and measured egg size and sperm swimming speeds. C. bifrons eggs were much larger (average diam=116.5 μm), and sperm swimming speeds faster (209.8 μm s−1), than C. asperrima (71.2 μm, 166.0 μm s−1). In both species, maximum fertilisation occurred at an ambient sperm concentration of around 100 sperm μl−1; the maximum proportion of eggs fertilised was less than 0.70 in the C. bifrons experiments, but nearer 1.0 with C. asperrima. At high sperm concentrations (>100 sperm μl−1), fertilisation decreased (presumably due to polyspermy) with increasing sperm concentration, but decreased more rapidly
in C. bifrons than C. asperrima. A polyspermy-adjusted fertilisation kinetics model could be fitted to the experimental data, but unique parameter estimates
could not be determined.
Received: 7 October 1999 / Accepted: 8 July 2000 相似文献
5.
The oxygen microenvironment adjacent to the tissue of the scleractinian Dichocoenia stokesii and its effects on symbiont metabolism 总被引:1,自引:0,他引:1
The biology of symbiotic scleractinians is profoundly influenced by their intracellular zooxanthellae, and many studies have
focused on the mechanistic basis of this influence. This has usually been accomplished by examining the metabolism of zooxanthellae
under physical conditions measured in the open reef and assumed to be similar to conditions in hospite. Recent advances in the measurement of conditions near and within coral tissue suggests that this assumption may result in
substantial errors. To address this possibility, the role of water flow in determining oxygen saturation adjacent to the tissue
of Dichocoenia stokesii was investigated, and the effect of these measured oxygen saturations on the respiration and photosynthesis of zooxanthellae
isolated from the same species was quantified. Using a microelectrode (700 μm diam), we measured oxygen saturations above
(≤4 mm) the tissue in two flow speeds over 24 h periods in a flume receiving sunlight at in situ levels. The results were
used as a proxy for ecologically relevant intracellular oxygen saturations, which were applied to zooxanthellae in vitro to
assess their effect on symbiont metabolism. Microenvironment oxygen saturations (% air saturation) ranged from 74–159% in
slow flow (2.7 cm s−1) to 88–110% in faster flow (7.5 cm s−1) over day–night cycles. Therefore, the metabolic rates of zooxanthellae were measured at 50 to 54% (hypoxia), 98 to 102%
(normoxia) and 146 to 150% (hyperoxia) oxygen saturation. Oxygen saturation significantly affected the metabolism of zooxanthellae,
with gross photosynthesis increasing 1.2-fold and dark respiration increasing 2-fold under hyperoxia compared to hypoxia.
These results suggest that the metabolism of zooxanthellae in hospite is affected markedly by their microenvironment which, in turn, is influenced by flow-mediated mass transfer.
Received: 13 July 1998 / Accepted: 30 April 1999 相似文献
6.
Fungiacyathus marenzelleri (Vaughan, 1906) is a deep-water solitary coral, cosmopolitan in distribution that is found at depths of 300–6,328 m. This
study examined gametogenesis, inter-annual variability and reproductive periodicity of F. marenzelleri collected from Station M (34°50′N, 123°00′W) in the northeast Pacific at a depth of 4,100 m. Samples were collected (May,
June, October 1996; August 1998; February, June 2001; and June 2002) and histologically processed with spermatogenic stage,
oocyte size and fecundity measured. Four stages of spermatogenesis were identified and all males contained multiple stages
of sperm development in each seasonal sample. Three stages of oocyte development were identified; previtellogenic (<28–150 μm),
vitellogenic (150–300 μm) and late vitellogenic (300–400 μm). Comparison of mean oocyte diameters among sampling dates showed
there were no inter-annual variations or seasonal differences. Overall, fecundity was 1,290 (±407) oocytes polyp−1, and with no significant differences between sample months. Fecundity was not polyp-size dependent. This study shows a similar
quasi-continuous mode of reproduction to this species examined from the Northeast Atlantic Ocean, but the fecundity is reduced
by 50%. The reproductive output may fluctuate in relation to the input of organic material at this site, as shown by non-significant
trends in the oocyte size-frequency and fecundity data. A quasi-continuous output of gametes would promote successful fertilisation
and wide dispersal of the lecithotrophic larvae. 相似文献
7.
The Salí River Basin in north-west Argentina (7,000 km2) is composed of a sequence of Tertiary and Quaternary loess deposits, which have been substantially reworked by fluvial and
aeolian processes. As with other areas of the Chaco-Pampean Plain, groundwater in the basin suffers a range of chemical quality
problems, including arsenic (concentrations in the range of 12.2–1,660 μg L−1), fluoride (50–8,740 μg L−1), boron (34.0–9,550 μg L−1), vanadium (30.7–300 μg L−1) and uranium (0.03–125 μg L−1). Shallow groundwater (depths up to 15 m) has particularly high concentrations of these elements. Exceedances above WHO (2011) guideline values are 100% for As, 35% for B, 21% for U and 17% for F. Concentrations in deep (>200 m) and artesian groundwater
in the basin are also often high, though less extreme than at shallow depths. The waters are oxidizing, with often high bicarbonate
concentrations (50.0–1,260 mg L−1) and pH (6.28–9.24). The ultimate sources of these trace elements are the volcanic components of the loess deposits, although
sorption reactions involving secondary Al and Fe oxides also regulate the distribution and mobility of trace elements in the
aquifers. In addition, concentrations of chromium lie in range of 79.4–232 μg L−1 in shallow groundwater, 129–250 μg L−1 in deep groundwater and 110–218 μg L−1 in artesian groundwater. All exceed the WHO guideline value of 50 μg L−1. Their origin is likely to be predominantly geogenic, present as chromate in the ambient oxic and alkaline aquifer conditions. 相似文献
8.
A. Cornils S. B. Schnack-Schiel M. Böer M. Graeve U. Struck T. Al-Najjar C. Richter 《Marine Biology》2007,151(4):1261-1274
A total of 12 feeding experiments were conducted in the northern Gulf of Aqaba during spring (March/April) and autumn (September/October)
2002 at the Marine Science Station (MSS) in Aqaba. Females of three species of clausocalanids were selected: Clausocalanus
farrani, C. furcatus and Ctenocalanus vanus. Natural occurring particle (NOP) larger than 5 μm were investigated as food source. The ambient chlorophyll a concentration at sampling depth (∼70 m) ranged between 0.15 and 1.00 μg chl a l−1 and NOP concentrations ranged between 1.78 and 14.0 × 103 cells l−1 during the sampling periods. The division of particles into five size classes (5–10, 10–20, 20–50, 50–100 and >100 μm) revealed
that most of the particles were found in the size classes below 50 μm (81–98%), while most of the natural occurring carbon
(NOC) was concentrated in the size classes larger than 20 μm (70–95%). Ingestion rates were food density dependent rather
than size dependent ranging between 0.02 and 1.65 × 103 NOP ind−1 day−1 and 0.01 and 0.41 μg NOC ind−1 day−1, respectively, equivalent to a body carbon (BC) uptake between 0.4 and 51.8% BC day−1. The share of the size classes to the total ingestion resembled in most cases the size class composition of the natural particle
community. 相似文献
9.
Georgiy Kirillin Christof Engelhardt Sergey Golosov 《Environmental Fluid Mechanics》2008,8(4):349-366
A mesoscale vortex structure in the small stratified Lake Stechlin has been revealed by field experiments with satellite-tracked
quasi-lagrangian drifters. The vortex with a radius of about 200 m drifted at 300 m/day along the western bight of the lake
with nearly constant rotation speed of 3 cpd. Analysis of kinematical properties of the vortex motion demonstrates solid body
character of rotation. Extrapolation of the vortex drift trajectory over the period preceding the observations combined with
data on local winds and seiche dynamics has allowed tracing the vortex fate from its generation point. The normal modes analysis
of the internal seiching in the lake reveals the vortex generation mechanism to be the interaction of certain seiche modes
with local bottom topography and suggests generation of the mesoscale vortices to be the a regular feature of the lake circulation.
Analysis of vorticity suggests additional energy supply to rotational flow, possibly from inverse cascading of small-scale
turbulent motions—a feature typical for quasi-2D turbulence. The vortices can play an important role in the energy transport
from basin-scale motions to small-scale boundary mixing. They can also contribute significantly to the horizontal heterogeneity
of phyto- and zooplankton distribution as well as to the transport of dissolved matter such as nutrients between littoral
and profundal areas. The topographically generated traveling vortices represent an analog of the synoptic eddies in the Ocean
and in the Atmosphere, whereas their role in the lake hydrodynamics is practically unknown. 相似文献
10.
S. Conova 《Marine Biology》1999,133(3):419-428
Suspension feeders sometimes depend on adhesion between particle and collector to capture food. If food particles have different
adhesive properties than other particles, food could be passively selected by adhesive mechanisms. In this regard, the effect
of particle wettability on adhesion to artificial and natural collectors was studied. First, the adhesion of glass particles
to artificial collectors, both varying in wettability, was assessed to determine if wettability influenced adhesion in seawater.
The adhesive force between glass particles and artificial collectors was measured by increasing the force pulling particles
away from the collector until 50% of the particles fell off the collector. Adhesion increased as particle wettability decreased.
Next, glass particles were used to determine if the antennal collector of the suspension-feeding mole crab Emerita talpoida captured particles based on particle wettability. 0.5 to 10 and 15 to 25 μm particles were suspended in a recirculating flow
tank filled with seawater, and ablated antennae were exposed to this flow, after which the captured particles were counted.
Results for the 0.5 to 10 μm particles confirmed predictions based on results from artificial collectors; particle capture
increased as particle wettability decreased. The 15 to 25 μm particles may have been captured by sieving, and consequently
did not follow predictions based on adhesion. Passive selection of particles based upon wettability differences can occur.
Received: 17 April 1998 / Accepted: 14 September 1998 相似文献
11.
Many symbioses involve multiple partners in complex, multi-level associations, yet little is known concerning patterns of
nutrient transfer in multi-level marine mutualisms. We used the anemonefish symbiosis as a model system to create a balance
sheet for nitrogen production and transfer within a three-way symbiotic system. We quantified diel patterns in excretion of
ammonia by anemonefish and subsequent absorption by host sea anemones and zooxanthellae under laboratory conditions. Rates
of ammonia excretion by the anemonefish Amphiprion bicinctus varied from a high of 1.84 μmole g−1 h−1 at 2 h after feeding, to a basal rate of 0.50 μmole g−1 h−1 at 24–36 h since the last meal. Conversely, host sea anemones Entacmaea quadricolor absorbed ammonia at a rate of 0.10 μmole g−1 h−1 during the daytime in ammonia-enriched seawater, but during the night reduced their absorption rate to near zero, indicating
that ammonia uptake was driven by zooxanthella photosynthesis. When incubated together, net ammonia excretion was virturally
zero, indicating that host anemones absorbed most of the ammonia produced by resident fish. Adult anemonefish weighed about
11 g under laboratory conditions, but on the coral reef may reach up to 64 g, resulting in a maximal potential ammonia load
of >200 μmole h−1 produced by two adult fish during daylight hours. In contrast, host sea anemones weighed about 47 g in the laboratory, but
under field conditions, large individuals may reach 680 g, so their maximal ammonia clearance rates may reach about 70 μmole h−1 during the daytime. As such, the ammonia load produced by adult anemonefish far exceeds the clearance rate of host anemones
and zooxanthellae. Ammonia transfer likely occurs mainly during the daytime, when anemonefish consume zooplankton and excrete
rapidly, and in turn the zooxanthellae are photosynthetically active and drive rapid ammonia uptake. We conclude that zooplanktivorous
fishes that form mutualisms with coral reef cnidarians may serve as an important link between open water and benthic ecosystems,
through the transfer of large quantities of nutrients to zooxanthellate hosts, thus enhancing coral reef productivity. 相似文献
12.
D. Raby M. Mingelbier J. J. Dodson B. Klein Y. Lagadeuc L. Legendre 《Marine Biology》1997,127(4):665-672
Epifluorescence microscopy was used to analyze the stomach contents of bivalve larvae collected in the Baie des Chaleurs
(western Gulf of St. Lawrence, Canada) in order to document food-particle sizes, compare feeding among taxa, and compare the
diet with the in situ phytoplankton community. Stomach contents were mainly composed of small autotrophic flagellates (<5
μm) and cyanobacteria (<2 μm), reflecting the microbial food web which characterizes these waters. More than half (55%) of
all veligers examined contained algal cells of 5 to 15 μm, whereas only 3% had cells of 15 to 25 μm. Differences in the size
ranges of ingested algal cells among similar-sized larvae of different species suggests that veligers actively selected food
particles. Among the smallest veligers (185 to 260 μm), scallops (Placopecten magellicanus) and mussels (Mytilus edulis) ingested more <5 μm and 5 to 15 μm algae than clams (Mya arenaria). Among larger veligers (261 to 405 μm), clams contained significantly more <5 μm cells than mussels, whereas mussels contained
significantly more 5 to 15 μm algae than clams. Algal cells of 15 to 25 μm were preferentially ingested by mussel veligers.
Feeding also differed between different-sized veligers within taxa, i.e. the smallest clam veligers ingested fewer of 5 to
15 μm algae than the larger size classes. Mussel veligers ingested significantly more 15 to 25 μm and fewer <5 μm cells as
their size increased. The dominance of ultraplankton in the nearshore waters of Baie des Chaleurs and in the stomach contents
suggests that veliger larvae may be an important export path for carbon produced by small phytoplankton.
Received: 17 July 1996 / Accepted: 20 September 1996 相似文献
13.
Adsorptive separation of phosphate oxyanion from aqueous solution using an inorganic adsorbent 总被引:2,自引:0,他引:2
Phosphate removal from aqueous solution was explored using granular ferric hydroxide (GFH) as an inorganic adsorbent. Adsorption,
desorption and kinetic studies were conducted on laboratory scale to evaluate the performance of GFH as an adsorbent for low
concentrations of phosphate solution. The effect of pH on adsorption was investigated, and phosphate uptake was shown to decrease
with an increase in solution pH, with maximum removal seen to occur at pH 3. The experimental data best fit the Temkin isotherm
at both pH 3 and 4. Uptake of phosphate by GFH follows second-order kinetics, with the small particle range (76–200 μm) removing
phosphate from the solution more rapidly than the larger particle range (710–850 μm). The kinetic results suggest that intra-particle
diffusion is an important factor in phosphate adsorption onto GFH. Thermodynamic parameters (ΔG°, ΔH°, ΔS°) were evaluated, and the results indicated that the adsorption process was endothermic and spontaneous. This study demonstrates
that GFH has potential to be used as a cost-effective adsorbent for phosphate removal from aqueous solution. 相似文献
14.
From September to November 1991, UV-absorbing mycosporine-like amino acids (MAAs) were monitored in a natural population of
the sea urchin Sterechinusneumayeri from a coastal area of Anvers Island (Antarctic Peninsula). MAA concentrations were determined for specific tissues (gonad,
digestive tract and body wall) from adults collected at four depths (intertidal, 8, 15 and 24 m). Four MAAs were identified:
mycosporine-glycine, shinorine, porphyra-334 and paly-thine. Concentrations of MAAs among replicate individuals varied considerably.
Ovaries had high concentrations of MAAs (84 to 1389 μg g−1 dry wt), while testes had non-detectable levels. The relative abundance of specific MAAs in ovaries appeared to be related
to the spawning cycle. Digestive-tract samples had MAA concentrations as high as 3000 μg g−1 dry wt, but the mean MAA content in intertidal individuals decreased by 70% over 3 mo during spring. The body walls of sea
urchins had very low amounts of MAAs (≤ 0.08 μg g−1 dry wt). There were significant depth differences in the␣total MAA content of the ovary ( p <0.001), ( p <0.015), digestive tract ( p <0.001), and body wall with organisms from the intertidal and 8 m depth having the highest concentrations of MAAs. Biological
dosimetry indicated that UV-B (280 to 320 nm) wavelengths penetrated 3 to 7 m below the sea ice during the study period. The
total MAA content in ovaries decreased with depth on all sample dates; however, the MAA content of the digestive tract and
body wall did not exhibit a consistent pattern of change with depth. The MAA content of tissues did not change significantly
with the temporal gradient of light exposure that was established by both ozone depletion and increasing photoperiod, except
in the digestive tract sampled from intertidal specimens. Adult urchins are probably well-protected from UV exposure by the
water column and a calcareous test; however, the results of this study suggest that, even under ice cover, depth of habitation
is a determinant of MAA content in S. neumayeri. Large daily and seasonal fluctuations in the light regime, which are characteristic of Antarctic coastal environments, apparently
do not provide reliable cues to elicit a detectable, temporal, biochemical response.
Received: 19 February 1997 / Accepted: 26 March 1997 相似文献
15.
Incidental soil ingestion is a common contaminant exposure pathway for humans, notably children. It is widely accepted that
the inclusion of total soil metal concentrations greatly overestimates the risk through soil ingestion for people due to contaminant
bioavailability constraints. The assumption also assumes that the contaminant distribution and the bioaccessible fraction
is consistent across all particle sizes. In this study, we investigated the distribution of arsenic across five particle size
fractions as well as arsenic bioaccessibility in the <250-, <100-, <10- and 2.5-μm soil particle fractions in 50 contaminated
soils. The distribution of arsenic was generally uniform across the larger particle size fractions but increased markedly
in the <2.5-μm soil particle fraction. The marked increase in arsenic concentration in the <2.5-μm fraction was associated
with a marked increase in the iron content. Arsenic bioaccessibility, in contrast, increased with decreasing particle size.
The mean arsenic bioaccessibility increased from 25 ± 16% in the <250-μm soil particle fraction to 42 ± 23% in the <10-μm
soil particle fraction. These results indicate that the assumption of static arsenic bioaccessibility values across particle
size fractions should be reconsidered if the ingested material is enriched with small particle fractions such as those found
in household dust. 相似文献
16.
Females of the spionid polychaete Streblospio benedicti (Webster) produce either small eggs (60–70 μm diameter) and planktotrophic larvae, or large eggs (100–200 μm) and lecithotrophic larvae that reportedly do not feed. This intraspecific polymorphism, a form of poecilogony, is potentially useful in studies of larval ecology and evolution, but necessary data on larval form and function are lacking. This study describes the morphology and nutritional biology of larvae obtained from Atlantic (South Carolina) and Pacific (California and Washington) populations from 2003 to 2005. The two types of larvae produced by Atlantic S. benedicti differed greatly in length (229±22 μm SD for planktotrophs vs. 638±40 μm for lecithotrophs) and chaetiger number (2–5 vs. 10–11) at release from the female’s brood pouch. Planktotrophic larvae bore long provisional chaetae on their first chaetiger; provisional chaetae were absent in lecithotrophic larvae. Larvae from Pacific populations were all of the lecithotrophic form, and were similar to their Atlantic counterparts in all respects. High-speed video microscopy revealed that both types of larvae used opposed bands of cilia to capture suspended particles and transport them to the mouth, where they were often ingested. Lecithotrophic larvae reared with suspended phytoplankton (Rhodomonas sp., 104 cells ml−1) for 2 days grew significantly faster than sibling larvae reared without added food, indicating that these larvae can digest and assimilate ingested food. Larvae of S. benedicti that develop from large eggs are thus facultative planktotrophs instead of obligately non-feeding lecithotrophs, a result that affects the interpretation of comparative studies of the ecology and evolution of larvae in S. benedicti and certain other marine invertebrates. 相似文献
17.
A survey of the distribution and maximum depth of a continuous Fucus vesiculosus belt was carried out in the Gulf of Finland in 1991. F. vesiculosus is widely distributed throughout the Gulf of Finland, including the vicinity of Vyborg Bay, Russia in the east. The maximum
growth depth of F. vesiculosus in the Gulf of Finland reflects two different patterns according to the exposure to wave action. The most robust and continuous
F. vesiculosus belt is observed on exposed shores, where the maximum growth depth is 5 to 6 m, with the optimum at 2 to 3 m. On moderately
exposed shores the maximum growth depth is 3 m, with an optimum growth depth of <2 m. The maximum growth depth also varies
geographically, with a decreasing trend towards the east. Maximum growth depth of F. vesiculosus correlates with light intensity. The compensation point for F. vesiculosus photosynthesis is about 25 μmol m−2 s−1, and photosynthesis is saturated at a light intensity of 300 μmol m−2 s−1. Vertical irradiance attenuation measurements in situ in summer revealed that for F. vesiculosus photosynthesis the quantity of light is optimal (200 to 300 μmol m−2 s−1) at <3 m depth. At depths >5 m the quantity of light is near or below the photosynthesis compensation point and insufficient
for growth. These depth limits of light penetration coincide with measured growth depths of F. vesiculosus in the Gulf of Finland.
Received: 7 May 1999 / Accepted: 18 November 1999 相似文献
18.
Suspension-feeding molluscs are important members of coastal communities and a large body of literature focuses on their feeding
processes, including the efficiency of particle capture. Some molluscs, such as bivalves, capture individual picoplankton
cells (0.2–2.0 μm) with a retention efficiency of less than 50%, leading to the assumption that such particles are not an
important food resource. Picoplankton, however, are often concentrated in particle aggregates of much larger size. This study
investigates the ability of suspension feeders to ingest picoplankton-size particles (0.2–2.0 μm) bound in marine aggregates.
We fed clams (Mercenaria mercenaria), mussels (Mytilus edulis), oysters (Crassostrea virginica), scallops (Argopecten irradians) and slipper snails (Crepidula fornicata) 1.0- and 0.5-μm fluorescent particles (either polystyrene beads or bacteria) that were (1) dispersed in seawater, or (2)
embedded within laboratory-made aggregates. Dispersed 10-μm beads were also delivered so that feeding activity could be determined.
Ingested fluorescent particles were recovered in feces or isolated digestive glands and quantified. Results indicate that
aggregates significantly enhance the ingestion of 1.0- and 0.5-μm beads by all species of bivalves, and enhance the ingestion
of bacteria (greatest cell dimension ca. 0.6 μm) by all suspension feeders examined. Differences among species in their ability
to ingest aggregates and picoplankton-size particles, however, were evident. Compared to mussels and clams, scallops and oysters
ingested fewer aggregates with 1.0-μm beads or bacteria, and slipper snails ingested the most dispersed beads and bacteria.
These differences may be a consequence of variations in gill structure and mechanisms of particle processing. Our data demonstrate
that suspension feeders can ingest picoplankton-size particles that are embedded within aggregates, and suggest that such
constituent particles may be an important food resource. 相似文献
19.
Laboratory culture experiments were performed to study the changes in size-fractionated Fe concentrations during the growth
of the oceanic diatom Chaetoceros sp. Fe concentration was estimated for three size fractions: large labile particles (>0.2 μm), small colloidal particles
(0.2 μm to 200 kDa) and soluble species (<200 kDa). The size-fractionated Fe concentration in the nutrient-enriched filtered
seawater medium without diatom cells became stable within 4 d after the spike of FeCl3 solution. Light irradiation by white fluorescent tubes with a 14 h light:10 h dark cycle did not significantly alter concentrations
of the size-fractionated Fe. For the phytoplankton culture experiment, Fe-starved diatom cells were inoculated into the nutrient-enriched
media aged for 19 d after the addition of FeCl3. With the growth of diatom cells, total acid-labile Fe concentrations decreased from 0.60 to 0.46 nM during 7 d of incubation. However, only the concentration of the small colloidal particles showed a significant decrease;
the concentration of the other size fractions remained relatively constant. Although the media still contained sufficient
amounts Fe as large labile particles and soluble species, diatom cells appeared to be Fe-limited once Fe as small colloidal
particles had been used up. These results suggest that Fe in the small colloidal particle fraction was the most dynamic size
fraction during the growth of the diatom Chaetoceros sp. In addition, to better understand Fe dynamics in the ocean, we must consider the influence of phytoplankton growth on
small colloidal Fe [which is typically included in the dissolved Fe fraction (<0.2 μm)].
Received: 9 December 1999 / Accepted: 5 May 2000 相似文献
20.
Vertical movement and habitat of opah (Lampris guttatus) in the central North Pacific recorded with pop-up archival tags 总被引:1,自引:0,他引:1
Data from 11 pop-up archival transmitting tags attached to opah (Lampris guttatus, F. Lampridae) in the central North Pacific between November 2003 and March 2005 were used to describe their vertical movement
and habitat. In the subtropical gyre northwest of the Hawaiian Islands, opah generally inhabited a 50–400 m depth range and
8–22°C temperatures. They were frequently found in depths of 50–150 m at night and in greater depths (100–400 m) during the
day, but were constantly moving vertically within this broad range. At night, excursions below 200 m were not uncommon and
during the day they were very likely to spend some time at depths <175 m. Their vertical speeds were generally <25 cm s−1 but on one occasion an opah descended at a burst speed of 4 m s−1. Vertical habitat use by individual opah apparently varied with local oceanographic conditions, but over a 24-h period the
average temperature experienced was always in the narrow range of 14.7 to 16.5°C.
相似文献
Jeffrey J. PolovinaEmail: |