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1.
Seasonal sampling was carried out based on day/night, vertically stratified tows (100 or 125 m strata) in the upper 900 m
of the water column over the mid-slope commercial fishing grounds south of Tasmania. A large midwater trawl (105 m2 mouth area) was used with an opening/closing cod-end. Subtropical convergence and subtropical species dominated the fauna,
but many less abundant, more widely-distributed species were also present. Fishes, which contributed 89% of micronekton biomass
and 135 of 178 species, were dominated by the Myctophidae (48% biomass and 48 species). Twenty micronekton species made up
80% of the total biomass. Overall, the micronekton fish biomass in this region was 2.2 g m−2 wet weight. A pronounced day/night shift in the distribution of biomass was attributable to diel migratory species. During
the day, <0.2% of the total micronekton biomass was found in 0 to 300 m; most biomass was below 400 m, with peaks at 400 to
525 m and 775 to 900 m. At night, 53% of the biomass was found in 0 to 300 m, with progressively less in each deeper stratum.
The vertical ranges of individual species typically exceeded 400 to 500 m during the day and night and were non-coincident,
although nyctoepipelagic migrators were concentrated in the surface 200 m at night. Distinct epipelagic, lower and upper mesopelagic
assemblages were identified, and patterns of epipelagic migration, limited migration and non-migration were categorised for
species from each of the lower and upper mesopelagic assemblages. The vertical distribution of these assemblages was coincident
with the primary water masses: subantarctic mode water (∼250 to 600 m) and antarctic intermediate water (below ∼700 m). The
flux of migrating micronekton, estimated at 0.94 to 3.36 g C m−2 yr−1 to the lower mesopelagic and 1.14 to 4.06 g C m−2 yr−1 to the upper mesopelagic, appeared to be considerably outweighed by the consumption needs of aggregated mid-slope benthopelagic
predators. We suggest that advection of mesopelagic prey in antarctic intermediate water may sustain aggregated populations
of orange roughy (Hoplostethus atlanticus) and other predators on the micronekton in mid-slope depths at this site.
Received: 2 April 1997 / Accepted: 21 August 1997 相似文献
2.
Using the number of segments of pleopod rami as a marker of instar number, the population structure (instar composition)
of the mesopelagic gammarid amphipod Cyphocaris challengeri was investigated by monthly samplings from May 1997 to April 1999 at a station off southwest Hokkaido, Japan. Laboratory-rearing
experiments were also conducted to establish the relationship between the number of segments of pleopod rami and instar number,
and to estimate the growth pattern of this gammarid based on the intermolt period and molt-increment data. Stratified sampling
in the field (0 to 200 and 200 to 400 m depth strata) showed this species occurred mainly at 200 to 400 m depth during the
day. Instar analysis indicated that C. challengeri has 12 instars in females and 11 instars in males. Based on observations of secondary sexual characters, Instars 1 to 6 were
designated juveniles (Instars 1 to 3 occurred in the marsupia of gravid females); in males, 7 to 9 were immature and 10 and
11 were mature, while in females 7 and 8 were immature and 9 to 12 were mature. Off southwest Hokkaido, Instar 4 (just released
from a female's marsupium) was found throughout the year, with a peak abundance occurring in April to July of each year. A
sequential development of Instar 4 to 9 (youngest adult instar) through the year was observed. Generation length (i.e. the
time required to grow from Instar 4 to 10) was estimated from a laboratory-obtained growth curve to be 216 to 584 d at the
in situ temperature range (2 to 5 °C), which is consistent with observations on field populations. Specimens older than Instar
9 were rare in the field and could not be used in laboratory-rearing experiments, so longevity could not be estimated. Eggs
were oval and measured 0.6 mm (large diameter). Brood size ranged from 20 to 65. Comparing the present results with those
of epipelagic hyperiid amphipods, the nearly identical growth rates together with the production of fewer but larger eggs
seen in C. challengeri appear to reflect to the typical life mode of deep-living pelagic crustaceans.
Received: 14 February 2000 / Accepted: 6 July 2000 相似文献
3.
Mycosporine-like amino acids (MAAs), which occur in diverse taxonomic groups, exhibit in vivo absorption maxima between 310 nm
and 360 nm and may play a photoprotective role against ultraviolet (UV) exposure. Using cultures of colonial Phaeocystis antarctica, we examined the relationship between MAA concentration, in vivo UV absorption, photoprotective (carotenoid) and photosynthetic
pigments, and photosynthetically available radiation (PAR, 350–700 nm). UV absorption was high; chlorophyll-specific absorption,
a
*
ph, at 330 nm ranged from 0.06 to 0.41 m2/mg chlorophyll a. Values of a
*
ph (330) were 4–13 times greater than a
*
ph (676). Mycosporine-glycine, shinorine, and mycosporine-glycine valine are responsible for the strong in vivo UV absorption.
The sum of all MAAs increased with irradiance when normalized to chlorophyll a or carbon concentrations, whereas individual MAAs varied independently from each other. Mycosporine-glycine concentrations
showed no statistically significant change over the range of light intensities, whereas mycosporine-glycine and shinorine
concentrations increased at higher irradiances. The relative fluorescence yield for chlorophyll a was low in the UV region compared to the visible region, implying that absorbed UV radiation (<375 nm) is transferred inefficiently
to chlorophyll a in the reaction center. Quantitative estimates of UV screening by MAAs are attributed to elevated MAA concentrations and
increased diameter at high light.
Received: 31 March 1999 / Accepted: 13 July 2000 相似文献
4.
Vertical distribution, life cycle, and developmental characteristics of the mesopelagic copepod Gaidius variabilis Brodsky in the Oyashio region were investigated by combining analyses of field copepodite populations with laboratory-rearing
data of egg hatching and naupliar development. Field samplings from five discrete depths between the surface and ≤2000 m were
made approximately every month for 1 year. Most populations of G. variabilis occurred between 600 and 1000 m depth. A modest degree of reversed diel vertical migration behavior and some stage-specific
depth-distribution patterns were noted. All copepodite stages were observed throughout the year, suggesting a year-round spawning
of G. variabilis. From a prominent abundance peak of Copepodite Stage 1 (C1) seen in June to August, together with development times of eggs
and nauplii obtained in laboratory-rearing experiments, the major spawning season was extrapolated to be April to June, the
phytoplankton bloom season. Tracing the peak abundance of each copepodite stage (distinguishing males and females for C4 to
C6), the generation times of males and females were deduced as 2 and 1 year, respectively. All between-stage increments in
terms of wet-, dry-, and ash-free dry weights were greatest in C3/C4, and least in C5/C6 for both males and females. The increments
in C3/C4 and C4/C5 were greater for males than for females, reflecting a longer stage duration of the males. These weights
did not increase in C5/C6 males, possibly because feeding ceased in C6 males. These results for G. variabilis are compared with those for some mesopelagic copepods previously reported from other regions.
Received: 25 October 1999 / Accepted: 20 March 2000 相似文献
5.
Bioluminescence spectra of shallow and deep-sea gelatinous zooplankton: ctenophores, medusae and siphonophores 总被引:3,自引:0,他引:3
We have examined the variability and potential adaptive significance of the wavelengths of light produced by gelatinous zooplankton.
Bioluminescence spectra were measured from 100 species of planktonic cnidarians and ctenophores collected between 1 and 3500 m
depth. Species averages of maximal wavelengths for all groups ranged from 440 to 506 nm. Ctenophores (41 species) had characteristically
longer wavelengths than medusae (34 species), and the wavelengths from siphonophores (25 species) had a bimodal distribution
across species. Four species each produced two different wavelengths of light, and in the siphonophore Abylopsistetragona these differences were associated with specific body regions. Light from deep-dwelling species had significantly shorter
wavelengths than light from shallow species in both ctenophores (p = 0.010) and medusae (p = 0.009). Although light production in these organisms was limited to the blue-green wavelengths, it appears that within
this range, colors are well-adapted to the particular environment which the species inhabit.
Received: 27 April 1998 / Accepted: 27 October 1998 相似文献
6.
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
7.
Light regime in an Arctic fjord: a study related to stratospheric ozone depletion as a basis for determination of UV effects on algal growth 总被引:9,自引:0,他引:9
D. Hanelt H. Tüg K. Bischof C. Groß H. Lippert T. Sawall C. Wiencke 《Marine Biology》2001,138(3):649-658
Solar radiation as a primary abiotic factor affecting productivity of seaweeds was monitored in the Arctic Kongsfjord on
Spitsbergen from 1996 to 1998. The radiation was measured in air and underwater, with special emphasis on the UV-B (ultraviolet
B, 280–320 nm) radiation, which may increase under conditions of stratospheric ozone depletion. The recorded irradiances were
related to ozone concentrations measured concurrently in the atmosphere above the Kongsfjord with a balloon-carried ozone
probe and by TOMS satellite. For comparison, an ozone index (a spectroradiometrically determined irradiance of a wavelength
dependent on ozone concentration, standardized to a non-affected wavelength) was used to indicate the total ozone concentration
present in the atmosphere. Weather conditions and, hence, solar irradiance measured at ground level were seldom stable throughout
the study. UV-B irradiation was clearly dependent on the actual ozone concentration in the atmosphere with a maximal fluence
rate of downward irradiance of 0.27 W m−2 on the ground and a maximal daily fluence (radiation exposure) of 23.3 kJ m−2. To characterize the water body, the light transmittance, temperature and salinity were monitored at two different locations:
(1) at a sheltered shallow-water bay and (2) at a wave-exposed, deep-water location within the Kongsfjord. During the clearest
water conditions in spring, the vertical attenuation coefficient (K
d) for photosynthetically active radiation (PAR) was 0.12 m−1 and for UV-B 0.34 m−1. In spring, coinciding with low temperatures and clear water conditions, the harmful UV radiation penetrated deeply into
the water column and the threshold irradiance negatively affecting primary plant productivity was still found at about 5–6 m
depth. The water body in spring was characterized as a Jerlov coastal water type 1. With increasing temperature in summer,
snow layers and glacier ice melted, resulting in a high discharge of turbid fresh water into the fjord. This caused a stratification
in the optical features, the salinity and temperature of the water body. During melt-water input, a turbid freshwater layer
was formed above the more dense sea water. Under these conditions, light attenuation was stronger than defined for a Jerlov
coastal water type 9. Solar radiation was strongly attenuated in the first few metres of the water column. Consequently, organisms
in deeper water are protected against harmful UV-B radiation. In the surface water, turbidity decreased when rising tide caused
an advection of clearer oceanic water. In the course of the summer season, salinity continuously decreased and water temperature
increased particularly in shallow water regions. The impact of global climate change on the radiation conditions under water
and its effects on primary production of seaweeds are discussed, since organisms in the eulittoral and upper sublittoral zones
are affected by UV radiation throughout the polar day. In clearer water conditions during spring, this may also apply to organisms
inhabiting greater depths.
Received: 20 June 2000 / Accepted: 17 October 2000 相似文献
8.
A. I. Arkhipkin 《Marine Biology》1997,129(1):103-111
Statolith microstructure was studied in 56 Ancistrocheirus lesueurii (25 to 423 mm of mantle length, ML) caught in the central-east Atlantic. Statolith growth increments were grouped into three
main growth zones, distinguished mainly by increment width. The second transition in the statolith microstructure (from Zone
2 to Zone 3) coincides with the life history shift from epipelagic and upper mesopelagic to a bathyal habitat. Second-order
bands (mean 27.65 growth increments) and sub-bands (mean 13.6 growth increments) within statolith microstructure appeared
to be related to the lunar cycle. Striking sexual dimorphism is reflected in the age and growth rates: males live ca. 1 yr,
while females only start maturing at this age and obviously live >1.5 yr. A. lesueurii is a slow growing squid, attaining 25 to 30 mm ML at the age of 100 d. After ontogenetic migrations into bathypelagic waters
at ML > 30 to 35 mm, growth rates gradually decrease to the minimum known values for squids. Based on back-calculated hatching
dates, A. lesueurii hatches throughout the year with a peak between November and March.
Received: 28 August 1996 / Accepted: 31 January 1997 相似文献
9.
R. Böttger-Schnack 《Marine Biology》1990,106(3):473-485
The species abundance, vertical distribution and diurnal vertical migration of cyclopoid copepods was analyzed in the central Red Sea in October–November 1980. Samples were taken to a depth of 450 m with a multiple opening — closing plankton net with 0.1-mm mesh-size. Selected important species were allocated to five different groups according to their depth distributions during daytime. The greatest number of species (9) was found in the lower epipelagic zone (40 to 100 m), below the strong seasonal thermocline. The lowest number of species (1) occurred in the upper part of the upper mesopelagic zone (100 to 250 m), which is characterized by a strong dissolved oxygen gradient. Five species had a bimodal vertical distribution, with dual peak abundances in the epipelagic and upper mesopelagic zones. Distinct differences in distribution patterns were noted between sexes and/or developmental stages. The vertical range of diurnally migrating species was small, usually less than 50 to 100 m. Characteristic diurnal changes in the vertical succession of dominant species occur within the epipelagic zone (0 to 100 m). Species-specific vertical distribution patterns are compared with published data from other areas. A conspicuous difference in the proportion of carcasses was noted between species: small species (<0.5 mm in length) had a much higher proportion of carcasses, usually between 20 and 40% of the total standing stock, than larger ones (<5%). The potential causes of this phenomenon, which may be due to (1) methodological bias, (2) a lower sinking velocity of small carcasses, or (3) a higher mortality rate of small species, are discussed. 相似文献
10.
Acoustic telemetry was used to examine patterns of activity and space utilisation of coelacanths, nocturnal predators which
spend the day in submarine caves. Nine coelacanths (Latimeria chalumnae) were tracked, each for a period of 1 to 16 nights at Grande Comore, West Indian Ocean. Activities lasted on average 9 h,
usually starting shortly after sunset and ending before sunrise. Vertically, coelacanths moved up and down at and below cave
level by following the bottom contour, mainly between 180 and 400 m depth. The deepest record was 698 m, the shallowest 133 m.
Most time was spent between 200 and 300 m depth. Large individuals performed deep excursions to depths below 400 m, usually
once per night. The fish spent most time in water temperatures of 15 to 19 °C; they rarely ventured into waters warmer than
22 °C measured at depths shallower than 160 m depth. Horizontally, coelacanths stayed in narrow areas ranging from <1 to 10 km
of coastline. Coelacanths are extremely slow drift-hunters with an estimated average swimming speed of 3.2 m min−1, often travelling not more than 3 km per night. They probably take advantage of local upwelling and downwelling and slow
currents occurring parallel to the steep slopes. This study shows that coelacanths are inhabitants of the subphotic zone,
where they are active mainly below the depth of their daytime refuges.
Received: 7 July 1999 / Accepted: 11 February 2000 相似文献
11.
J. H. M. Kouwenberg H. I. Browman J. J. Cullen R. F. Davis J.-F. St-Pierre J. A. Runge 《Marine Biology》1999,134(2):269-284
In the Gulf of St. Lawrence, Canada, productivity-determining biophysical interactions occur in the upper 0 to 30 m of the
water column. The eggs and larvae of several commercially important marine invertebrates and fishes (e.g. Gadus morhua L.) are found in this layer. Measurements of the diffuse attenuation coefficients for ultraviolet-B radiation (280 to 320 nm,
UV-B) at various locations in this geographic region indicated maximum 10% depths (the depth to which 10% of the surface energy
penetrates at a given wavelength) of 3 to 4 m at a wavelength of 310 nm. This represents a significant percentage of the summer
mixed-layer water column: organisms residing in this layer are exposed to UV-B radiation. Laboratory experiments using a Xenon-arc-lamp
based solar simulator revealed that cod embryos exposed to UV-B exhibited high wavelength-dependent mortality. The strongest
effects occurred under exposures to wavelengths below 312 nm. This susceptibility was also dependent upon developmental stage;
mortality was particularly high during gastrulation. At the shorter wavelengths (<305 nm) UV-B-induced mortality was strongly
dose-dependent, and not significantly influenced by dose-rate. The biological weighting function (BWF) derived for UV-B-induced
mortality in cod eggs is similar to that reported for naked DNA – suggesting that the mortality is a direct result of DNA
damage. There was no evidence of a detrimental effect of ultraviolet-A radiation (320 to 400 nm). Calculations based upon
the BWF indicate that, under current noon surface irradiance, 50% of cod eggs located at or very near (within 10 cm) the ocean
surface will be dead after 42 h of exposure. Under solar spectral irradiance simulating a 20% decrease in ozone layer thickness,
this time drops to 32 h. These are first-order estimates based upon surface irradiance taken at a time of day during which
the values would be maximal. Nonetheless, they illustrate the relative changes in UV-B impacts that will result from ozone
layer depletions expected over the coming decades. It is also important to point out that variability in cloud cover, water
quality, and vertical distribution and displacement of cod eggs and larvae within the mixed layer, can all have a greater
effect on the flux of UV-B radiation to which fish eggs are exposed than will ozone layer depletion at these latitudes.
Received: 2 March 1998 / Accepted: 18 December 1998 相似文献
12.
Life history of Gonatus onyx (Cephalopoda: Teuthoidea): deep-sea spawning and post-spawning egg care
A reproductive strategy consisting of deep- water spawning and egg-care was inferred for the midwater squid Gonatus onyx Young, 1972. Brooding females and associated eggs and hatchlings, captured between 1250 and 1750 m depth off southern California,
are described. Brooding females appear to be senescent and lack tentacles. Large eggs of this species (3 mm) at cold temperatures
(3 °C at capture depth) may require as long as 9 mo to develop. The high lipid content of the digestive gland in adult females
of this species may provide fuel to support such an extended “brooding” period.
Received: 22 February 1999 / Accepted: 25 May 2000 相似文献
13.
Mesozooplankton (<5 mm) collected by stratified oblique tows with a 1-m2 MOCNESS was examined at four stations in the Arabian Sea, with special reference to the bathypelagic zone. The profiles commenced
about 20 m above bottom, at 4430 m as a maximum depth. The highest mesozooplankton biomass concentrations (wet weight per
cubic meter) were obtained from the surface layer during night. A secondary maximum was situated between 150 and 450 m, with
maximum concentrations at daytime. This layer coincided with the daytime residence depth of the deep scattering layer. The
standing crop of the mesozooplankton in the upper 1000 m was highest at station WAST at 16°N; 60°E (ca. 47 000 mg m−2); station CAST at 14°N; 65°E ranked second (ca. 22 500 mg m−2), followed by station SAST at 10°N; 65°E (11 420 mg m−2). The differences can be related to different productivity regimes at the sea surface generated by the Findlater Jet during
the SW monsoon. The differences in surface production were also reflected below 1000 m depth, in the bathypelagic zone, with
mesozooplankton wet weights of 5330 mg m−2 at WAST, 3210 mg m−2 at CAST, 3390 mg m−2 at EAST (15°N; 65°E) and 2690 mg m−2 at SAST. The decrease of mesozooplankton concentration with depth in the oxygen minimum zone (OMZ) was stronger than in comparable
depths of open-ocean areas where an OMZ is absent. Among the discriminated four size classes of mesozooplankton, the largest
fraction (2 to 5 mm) indicated a biomass peak at 1200 m depth, which coincided with the lower boundary layer of the OMZ. The
rate of decrease of mesozooplankton biomass with depth in the bathypelagic zone was statistically similar between the sites,
even though the absolute zooplankton biomass at the sites was different. There is no evidence that the presumed lower carbon
degradation rates in the OMZ of the Arabian Sea caused a larger standing crop and less of a decrease in biomass with depth
in the bathypelagic zone in comparison to other seas.
Received: 16 May 1997 / Accepted: 5 June 1997 相似文献
14.
The sea urchin Lytechinus variegatus is capable of surviving chronic exposure to sodium phosphate (inorganic phosphate) concentrations as high as 3.2 mg l−1, and triethyl phosphate (organic phosphate) concentrations of 1,000 mg l−1. However, chronic exposure to low (0.8 mg l−1 inorganic and 10 mg l−1 organic phosphate), medium (1.6 mg l−1 inorganic and 100 mg l−1 organic phosphate) or high (3.2 mg l−1 inorganic and 1,000 mg l−1 organic phosphate) sublethal concentrations of these phosphates inhibits feeding, fecal production, nutrient absorption and
allocation, growth and righting behavior. Food consumption and fecal production declined significantly in individuals exposed
to medium and high concentrations of inorganic phosphates and all levels of organic phosphates. Feeding absorption efficiencies
for total organics and carbohydrates decreased significantly in individuals held in the highest concentration of organic phosphate.
Feeding absorption efficiencies for lipids were significantly reduced in the highest inorganic phosphate concentration only,
while they decreased significantly for protein with increasing phosphate exposure. Carbohydrate and lipid levels in gonad
and gut tissues decreased significantly with exposure to increasing phosphate concentrations, potentially impairing both gametogenesis
and nutrient storage in the gut. Moreover, gonad indices significantly decreased in individuals exposed to the highest concentrations
of either phosphate. Growth rates decreased significantly under the influence of all phosphate concentrations, while increasing
in seawater alone. Individuals exposed to increasing phosphate concentrations showed reduced righting responses (a measure
of stress) and no acclimation in righting times during chronic exposure to phosphates over a 4 week period. These findings
indicate that shallow-water populations of L. variegatus subjected to inorganic and organic phosphate pollutants will exhibit stress and be inhibited in their growth and performance
due to reductions in feeding, nutrient absorption and allocation of nutrients to key somatic and reproductive tissues.
Received: 10 April 2000 / Accepted: 2 October 2000 相似文献
15.
In the Red Sea, the zooxanthellate sponge Cliona vastifica (Hancock) is mainly present at >15 m depth or in shaded areas. To test whether its scarcity in unshaded areas of shallower
waters is linked to the functional inefficiency of its photosymbionts at high irradiances, sponges were transferred from 30 m
to a six times higher light regime at 12 m depth, and then returned to their original location. During this time, photosynthetic
responses to irradiance were measured as rapid light curves (RLCs) in situ by pulse amplitude modulated (PAM) fluorometry
using a portable underwater device, and samples were taken for microscopic determinations of zooxanthellar abundance. The
zooxanthellae harboured by this sponge adapted to the higher irradiance at 12 m by increasing both their light saturation
points and relative photosynthetic electron transport rates (ETRs). The ETRs at light saturation increased almost fourfold
within 15–20 days of transfer to the shallower water, and decreased back to almost their original values after the sponges
were returned to 30 m depth. This, as well as the fact that the photosynthetic light responses within an individual sponge
were in accordance with the irradiance incident to specific surfaces, shows that these photosymbionts are highly adaptable
to various irradiances. There was no significant change in the number of zooxanthellae per sponge area throughout these experiments,
and the different photosynthetic responses were likely due to adaptations of the photosynthetic apparatus within each zooxanthella.
In conclusion, it seems that parameters other than the hypothesised inability of the photosymbionts to adapt adequately to
high light conditions are the cause of C. vastifica's rareness in unshaded shallow areas of the Red Sea.
Received: 25 April 2000 / Accepted: 13 October 2000 相似文献
16.
Relationship between depth, sediment, latitude, and the structure of benthic infaunal assemblages on the mainland shelf of southern California 总被引:2,自引:0,他引:2
Mary Bergen Stephen B. Weisberg Robert W. Smith Donald B. Cadien Ann Dalkey David E. Montagne Janet K. Stull Ronald G. Velarde J. Ananda Ranasinghe 《Marine Biology》2001,138(3):637-647
A regional benthic survey was conducted in 1994, and the data were used to assess the relationship among three habitat factors
(depth, sediment grain size, and latitude) and the distribution of benthic infaunal assemblages on the southern California
coastal shelf. Benthic samples were collected with a 0.1 m2 Van Veen grab from 251 sites on the continental shelf (10–200 m deep) from Point Conception, California, to the United States–Mexico
international border. The relationship between habitat and assemblages was investigated by conducting a Q-mode cluster analysis
to define groups of stations with similar species composition and then examining whether differences were present in physical
habitat attributes among those groups of stations. Analysis of data from 175 uncontaminated sites yielded four habitat-related
benthic infaunal assemblages along the southern California coastal shelf: a shallow-water assemblage from 10–32 m, a mid-depth
assemblage between 32 and 115 m, and two deep-water (115–200 m) assemblages, one in fine and one in coarse sediments. These
empirically defined points in the depth and sediment grain size gradients can be used to define reference habitats for the
development of biocriteria. Benthic abundance and diversity were greatest in the mid-depth assemblage, conforming to predictions
for benthic assemblages in regions of upwelling. Within the 500 km of coastline examined, latitude was not an important factor
in defining assemblages.
Received: 3 December 1999 / Accepted: 9 October 2000 相似文献
17.
The European fanworm Sabella spallanzanii (Gmelin, 1791) was recently introduced to Port Phillip Bay and is now a conspicuous component of most benthic communities.
Reproduction of the worm was investigated in a population at Queenscliff over a 2 yr period (October 1995 to October 1997)
using gonadal histology. The worms are dioecious (sex ratio 1:1, n=250), and attained sexual maturity at ∼50 mm body length. Reproductive periodicity followed a distinct annual cycle, and
spawning proceeded through an extended autumn/winter period. Spawning was broadly synchronous between sexes, and coincided
with falling seawater temperatures and shorter day-lengths. The females were highly fecund, and >50 000 eggs were probably
shed from large females (>300 mm body length) during the annual spawning period. Breeding cycles of S. spallanzanii in Port Phillip Bay are ∼6 mo out of phase with endemic populations located at similar latitudes in the northern hemisphere.
The spread of S. spallanzanii within Port Phillip Bay has been monitored by divers on an annual basis since 1994. The most recent dive survey (1998) indicates
that S. spallanzanii has extended its range through out the entire 2000 km2 embayment, and has invaded most subtidal habitats. Quantitative estimates of S. spallanzanii abundances were highest on pier pylons (12.5 individuals m−2, 0.5 to 7 m depths). On sediments, estimates were highest at shallow sites (0.3 m−2, 7 m depth), but numbers declined significantly with depth (0.1 m−2, 17 to 22 m depth). Mean worm lengths and biomass were, by contrast, significantly higher at intermediate depths (12 to 17 m)
than in shallower (7 m) or deeper (22 m) locations. S. spallanzanii demonstrates a clear preference for growth in sheltered, nutrient-enriched waters, so it may not spread from Port Phillip
Bay into the adjacent oceanic waters of Bass Strait; however, in view of S. spallanzanii's current high abundance, fecundity and extended spawning periodicity, there is a high risk of future range expansions, mediated
by shipping, into other temperate-water ports.
Received: 17 November 1998 / Accepted: 6 January 2000 相似文献
18.
Experiments were performed to determine how ultraviolet radiation (UVR) in the environmentally relevant range affects development
of the sea urchin Strongylocentrotus droebachiensis (Müller) and whether mycosporine-like amino acids (MAAs), present in the early life stages, reduce UV-induced damage. Eggs,
embryos, and larvae contained five MAAs having absorption maxima ranging from 320 to 334 nm. Eggs contained principally shinorine
and porphyra-334, which absorb maximally at 334 nm and half-maximally at 312 and 348 nm, spanning much of the environmental
range of biologically effective UVR. Concentrations of MAAs remained constant in unirradiated embryos through the gastrula
stage, but decreased significantly in two-armed pluteus larvae. Daily exposure to combined photosynthetically active radiation
(PAR, 400–700 nm) and UVR did not affect the concentration of MAAs in these embryos up to the two-armed pluteus stage. Prism
larvae of sea urchins and the sand dollar Echinarachnius parma (Lamarck) did not accumulate shinorine from the surrounding seawater. Daily exposure of embryos to UVA (320–400 nm) and UVB
(295–320 nm) radiation in the presence of PAR induced delays and abnormalities during development, and removing UVB eliminated
this effect. Abnormalities in embryos included thickening of the blastoderm wall, filling of the blastocoel by abnormal cells,
exogastrulation, and formation of abnormal spicules. The percentage of embryos that developed normally was lower in batches
of embryos exposed to PAR + UVA + UVB, except in embryos from urchins maintained on MAA-rich diets. In all cases, the percentage
of PAR + UVA + UVB-exposed embryos that developed normally was positively related to the concentration of MAAs in eggs from
which the embryos developed. Thus, the MAAs found in S. droebachiensis embryos protect them against UVB-induced abnormalities during their development to at least the four-armed pluteus larval
stage.
Received: 8 May 2000 / Accepted: 29 September 2000 相似文献
19.
Growth parameters of deep-water decapod crustaceans in the Northwestern Mediterranean Sea: a comparative approach 总被引:1,自引:1,他引:0
Relative and absolute growth were studied in 17 species of deep-water decapod crustaceans, spanning nine families of six
different infra-orders, in the Northwestern Mediterranean Sea. The overall maximum abundance of these species lay between
200 m and 750 m (i.e. upper- and mid-slope species). Relative and absolute growth rates were compared by contrasting the slopes
of the size–weight relationships for the different species and calculating the von Bertalanffy growth-equation parameters
asymptotic length (L
∞
) and growth rate (k). The size–weight relationships differed significantly as function of the species' life habits. The results revealed a significant
decrease in weight relative to size in mesopelagic species (which carry out diel vertical migrations), an almost isometric
relationship between size and weight in the less mobile nektobenthic species, and a significant increase in weight relative
to size in strictly benthic species. The mean allometric coefficient for each group increased significantly from mesopelagic
to benthic species. However, no general trend was observed in the growth-performance index, Φ (an index used to compare absolute
growth rates between species, as a function of habit and depth of maximum abundance for all species combined), suggesting
that the deep-water decapod crustaceans studied have similar absolute growth rates. Nevertheless, comparison of growth-parameter
and growth-performance index values within families did reveal differences. Mesopelagic species of the families Sergestoidae
and Pasiphaeidae showed slightly increased growth rates with increasing depth of distribution. Nektobenthic species of the
genus Plesionika followed a trend opposite to that shown by mesopelagic species, with a higher growth rate for the shallowest-dwelling species
(P. heterocarpus) than the deepest-dwelling species (P. acanthonotus). Taking growth as one of the major components of an organism's energy budget, the growth rates for the decapod crustacean
species in this study were significantly lower than those reported in the literature for shallow-water penaeid crustacean
species (which are distributed in higher-temperature habitats than deep-water Mediterranean crustaceans) and higher than those
reported for mesopelagic myctophid fish species. Hence, the well-defined growth trends shown by deep-water decapod crustacean
species in the Northwestern Mediterranean Sea, compared to the less well-defined trends in the other taxa, is discussed in
the framework of the overall dynamics of their ecosystem.
Received: 25 May 1998 / Accepted: 27 September 1999 相似文献
20.
Depth and muscle temperature of Pacific bluefin tuna examined with acoustic and pop-up satellite archival tags 总被引:1,自引:0,他引:1
David J. Marcinek Susanna B. Blackwell Heidi Dewar Ellen V. Freund Charles Farwell Daniel Dau Andrew C. Seitz Barbara A. Block 《Marine Biology》2001,138(4):869-885
Six Pacific bluefin tuna were tracked with ultrasonic telemetry and two with pop-up satellite archival tags (PSATs) in the
eastern Pacific Ocean in 1997, 1998, and 1999. Both pressure and temperature ultrasonic transmitters were used to examine
the behavior of the 2- to 4-year-old bluefin tuna. The bluefin spent over 80% of their time in the top 40 m of the water column
and made occasional dives into deeper, cooler water. The mean slow-oxidative muscle temperatures of three fish instrumented
with pressure and temperature transmitters were 22.0–26.1 °C in water temperatures that averaged 15.7–17.5 °C. The thermal
excesses in slow-oxidative muscle averaged 6.2–8.6 °C. Variation in the temperature of the slow-oxidative muscle in the bluefin
was not correlated with water temperature or swimming speeds. For comparison with the acoustic tracking data we examined the
depth and ambient temperature of two Pacific bluefin tagged with pop-up satellite archival tags for 24 and 52 days. The PSAT
data sets show depth and temperature distributions of the bluefin tuna similar to the acoustic data set. Swimming speeds calculated
from horizontal distances with the acoustic data indicate the fish mean speeds were 1.1–1.4 fork lengths/s (FL s−1). These Pacific bluefin spent the majority of their time in the top parts of the water column in the eastern Pacific Ocean
in a pattern similar to that observed for yellowfin tuna.
Received: 4 April 2000 / Accepted: 25 October 2000 相似文献