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1.
Strontium (Sr) and calcium (Ca) contents in the otoliths of yellow and silver European eels [Anguilla anguilla (L.)] collected from coastal waters of the Baltic Sea and a freshwater lake in Sweden were examined by wavelength dispersive
X-ray spectrometry with an electron microprobe. The mean Sr/Ca ratios from elver check to otolith edge were significantly
higher for the eels from coastal waters (5.39 ± 1.09‰) than for those from the lake (0.71 ± 0.89‰). The evidence indicates
that European eels in the Baltic Sea do not necessarily migrate into freshwater streams during the growth phase.
Received: 30 September 1999 / Accepted: 6 April 2000 相似文献
2.
Juanita S. Bité Stuart J. Campbell Len. J. McKenzie Robert G. Coles 《Marine Biology》2007,152(2):405-414
In coastal waters and estuaries, seagrass meadows are often subject to light deprivation over short time scales (days to weeks)
in response to increased turbidity from anthropogenic disturbances. Seagrasses may exhibit negative physiological responses
to light deprivation and suffer stress, or tolerate such stresses through photo-adaptation of physiological processes allowing
more efficient use of low light. Pulse Amplitude Modulated (PAM) fluorometery has been used to rapidly assess changes in photosynthetic
responses along in situ gradients in light. In this study, however, light is experimentally manipulated in the field to examine
the photosynthesis of Halophila ovalis and Zostera capricorni. We aimed to evaluate the tolerance of these seagrasses to short-term light reductions. The seagrasses were subject to four
light treatments, 0, 5, 60, and 90% shading, for a period of 14 days. In both species, as shading increased the photosynthetic
variables significantly (P < 0.05) decreased by up to 40% for maximum electron transport rates (ETRmax) and 70% for saturating irradiances (Ek). Photosynthetic efficiencies (α) and effective quantum yields (ΔF/Fm′) increased significantly (P < 0.05), in both species, for 90% shaded plants compared with 0% shaded plants. H. ovalis was more sensitive to 90% shading than Z. capricorni, showing greater reductions in ETRmax, indicative of a reduced photosynthetic capacity. An increase in Ek, Fm′ and ΔF/Fm′ for H. ovalis and Z. capricorni under 90% shading suggested an increase in photochemical efficiency and a more efficient use of low-photon flux, consistent
with photo-acclimation to shading. Similar responses were found along a depth gradient from 0 to10 m, where depth related
changes in ETRmax and Ek in H. ovalis implied a strong difference of irradiance history between depths of 0 and 5–10 m. The results suggest that H. ovalis is more vulnerable to light deprivation than Z. capricorni and that H. ovalis, at depths of 5–10 m, would be more vulnerable to light deprivation than intertidal populations. Both species showed a strong
degree of photo-adaptation to light manipulation that may enable them to tolerate and adapt to short-term reductions in light.
These consistent responses to changes in light suggest that photosynthetic variables can be used to rapidly assess the status
of seagrasses when subjected to sudden and prolonged periods of reduced light. 相似文献
3.
Cell growth of a coastal marine diatom, Chaetoceros sociale, in the presence of different premixed organic-Fe(III) complexes [EDTA-Fe(III) (100:1 and 2:1), citric-Fe(III) (100:1) and
fulvic-Fe(III) (0.1, 0.2 and 1 ppm C)] and solid amorphous hydrous ferric oxide [am-Fe(III) or Fe(III) hydroxide] were experimentally
measured in culture experiments at 10 °C under 3000 lux fluorescent light. Fulvic-Fe(III) (0.1 and 0.2 ppm C) and citric-Fe(III)
(100:1) induced maximal cell yields of C. sociale. The order of cell yields was: fulvic-Fe(III) (0.1 and 0.2 ppm C) ≥ citric-Fe(III) (100:1) > EDTA-Fe(III) (2:1) ≫ solid am-Fe(III) > EDTA-Fe(III)
(100:1) ≫ fulvic-Fe(III) (1 ppm C). The short-term iron uptake rates by C. sociale in fulvic-Fe(III) (0.1 and 0.2 ppm C) and citric-Fe(III) (100:1) media were about five to six times faster than those in
EDTA-Fe(III) (100:1) and solid am-Fe(III) media. The dissociative precipitation rates of premixed organic-Fe(III) complexes
in seawater at 10 °C were determined by simple filtration (0.025 μm) involving γ-activity measurements of 59Fe. The order of estimated initial Fe(III) dissociative precipitation rates of these organic-Fe(III) complexes in seawater
were nearly consistent with those of cell yields in the culture experiments and short-term iron uptake rates by C. sociale [except for fulvic-Fe(III) (1 ppm C) medium]. In fulvic-Fe(III) (0.1 and 0.2 ppm C), citric-Fe(III) (100:1) and EDTA-Fe(III)
(2:1) media, the concentrations of dissolved organic-Fe(III) complexes in initial culture experiments are prone to supersaturate
under the culture conditions. The supersaturated dissolved organic-Fe(III) complex in seawater supplies biologically available
inorganic Fe(III) species in culture media through its dissociation at high pH and high levels of seawater cations. Therefore,
the natural dissolved organic-Fe(III) complexes supplied by riverine input may play an important role in supplying bioavailable
iron in estuarine mixing system and coastal waters.
Received: 6 September 1998 / Accepted: 8 April 1999 相似文献
4.
Chemically mediated alarm reactions of the common periwinkle, Littorina littorea (L.), were studied in laboratory experiments during two consecutive summers, and one intermediate autumn season. Responses
to chemical stimuli were detected as crawl-out responses, i.e. movements of snails out of the water. Snails were exposed to
extracts of injured conspecifics, extracts of the mussel Modiolus modiolus (L.), and water conditioned by the predatory crab Carcinus maenas (L.), which had been maintained on different diets. In experiments carried out during the summer, a significantly larger
number of snails moved out of the water when exposed to chemical stimuli from injured conspecifics, compared to chemical stimuli
from injured mussels or filtered seawater. These results suggest that chemical alarm substances are present in L. littorea. Water conditioned by crabs that had been fed L. littorea released significantly more crawl-out responses compared to water conditioned by crabs that had been kept on a fish diet.
When tested in autumn, no significant differences were found in responses to the above-mentioned water samples. Crawl-out
responses under different light regimes were also investigated. All series of experiments carried out in the dark evoked a
higher number of responses compared to series that took place in light. These findings may indicate an adaptation of snails
to night-active predators. In total, the current results suggest that a L. littorea diet may chemically “label” the predator crab with snail alarm substances, and that predator-induced responses of L. littorea are actually responses to conspecific alarm substances released from crabs that have been maintained on a L. littorea diet. The response to the alarm signal, however, appears to be dependent on season and light conditions; some ecological
implications of these findings are also discussed.
Received: 8 January 1999 / Accepted: 29 March 1999 相似文献
5.
Summary. Antennae of six sympatric bark and ambrosia beetles (Scolytidae), Dendroctonus valens LeConte, Gnathotrichus retusus (LeConte), Hylastes tenuis Eichhoff, Ips mexicanus (Hopkins), Ips plastographus maritimus Lanier, and Pseudohylesinus sericeus (Mannerheim), and two scolytid predators, Enoclerus sphegeus (F.) (Cleridae) and Lascontonus tuberculatus Kraus (Colydiidae), were analyzed by gas chromatographic-electroantennographic detection (GC-EAD) for their responses to
synthetic Ips spp. pheromone components, and host and nonhost volatiles.
The beetles emerged from cut logs of pitch canker-infected Monterey pine trees, Pinus radiata D. Don. There were significant disparities in EAD response patterns to the hemiterpene and monoterpene alcohol pheromone
components that are typically produced by Ips spp. Antennae of I. p. maritimus responded strongly to ( ± )-ipsdienol, ( ± )-ipsenol, amitinol, and lanierone; antennae of I. mexicanus responded strongly to (1S,2S)-(–)-cis-verbenol, with weaker responses to ( ± )-ipsdienol, ( ± )-ipsenol, and amitinol; antennae of H. tenuis responded to (1S, 2R)-(–)-trans-ver-benol, with less pronounced responses to (–)-cis-verbenol and 2-methyl-3-buten-2-ol; and antennae of D. valens, G. retusus, and P. sericeus generally responded to all Ips spp. pheromone components except 2-methyl-3-buten-2-ol (D. valens and G. retusus) and E-myrcenol (G. retusus and P. sericeus). Ips mexicanus
responded only to the (–)-enantiomers of ipsenol and ipsdienol, whereas I. p. maritimus responded to (–)-ipsenol, but to both the (+)- and (–)-enantiomers of ipsdienol. The antennae of the two predaceous insects
(E. sphegeus and L. tuberculatus) responded to a range of the Ips spp. pheromone components. Host monoterpenes elicited no antennal responses from E. sphegeus, G. retusus, H. tenuis, and I. mexicanus, but several monoterpenes elicited various levels of responses from D. valens and I. p. maritimus antennae. Interestingly, antennae of female D. valens responded to (–), but not (+)-limonene. α- and β-Pinene elicited weak responses from L. tuberculatus antennae. EAD responses to selected nonhost volatiles were almost identical among the six scolytid species, with trans-conophthorin eliciting the strongest response in most cases, followed by three C6- alcohols and two C8-alcohols. The antennal responses by most of these species to linalool or geranylacetone were very weak; (E)-2-hexenal, (Z)-3-hexenyl acetate, and benzyl alcohol elicited almost no response. The response pattern of P. sericeus to nonhost volatiles differed slightly from the rest of the scolytids: a strong response to linalool, weaker response to
the C8-alcohols. The two predaceous Coleoptera generally had weak, but detectable, responses to nonhost volatiles, except for a
relatively strong response to trans-conophthorin by L. tuberculatus. No notable differences in EAD responses were observed between males and females of the two Ips spp. Our results provide an electrophysiological baseline for future efforts to identify attractive and repellent semiochemicals
(aggregation pheromones, host kairomones, or nonhost interruptants) for this guild of scolytids and their key predators that
are associated with moribund and pitch canker- infected P. radiata. 相似文献
6.
Christopher E. Hill S. Elizabeth Campbell J. Cully Nordby John M. Burt Michael D. Beecher 《Behavioral ecology and sociobiology》1999,46(5):341-349
Sharing song types with immediate neighbors is widespread in birds with song repertoires, and sharing songs may confer a
selective advantage in some cases. Levels of song sharing vary between different geographical populations of several bird
species, and ecological differences often correlate with differences in singing behavior; in particular, males in migratory
subspecies often share fewer songs than males in resident subspecies. The song sparrow (Melospiza melodia) appears to fit this pattern: resident song sparrows in western North America generally share 20–40% of their repertoire
(of about eight songs) with each neighbor, while migratory subspecies from eastern North America often share 10% or less.
We compared song sharing in two populations within a single subspecies of song sparrow (M. m. morphna) in Washington State. These populations, separated by only 120 km, nonetheless differ in migratory tendencies and several
other ecological and life history variables. We recorded complete song repertoires from 11 male song sparrows in a high-elevation,
migrating population at Gold Creek in west-central Washington, and compared them to two samples (n = 15 and n = 36) from a coastal, resident population at Discovery Park, Seattle, Washington. Despite major differences in habitat, population
density, and migratory tendencies, song sharing among Gold Creek males was as high as that among Discovery Park males. In
both populations, sharing was highest between immediate neighbors, and declined with distance. We conclude that at the within-subspecies
level, neither migration nor population density affect song sharing in song sparrows, a song repertoire species.
Received: 26 November 1998 / Received in revised form: 1 May 1999 / Accepted: 29 May 1999 相似文献
7.
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
8.
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
9.
The biochemical composition of vegetative cells and resting spores of Chaetoceros pseudocurvisetus Mangin was compared in cultures under various nutrient and light conditions. The cellular content of major nucleotides such
as AMP, ADP, ATP and UTP decreased in the order: vegetative cells, nutrient-starved (vegetative) cells and resting spores,
indicating that the general metabolism of resting spores is relatively inactive. ADP-glucose was only abundant in nutrient-starved
vegetative cells, suggesting metabolic imbalance in these cells. The chl a–specific fluorescence yield of vegetative cells grown under all culture conditions was low, but very high in resting spores.
The ratios of the cellular contents of diadinoxanthin to chl a and of diatoxanthin to chl a were higher in resting spores and nutrient-starved vegetative cells than in nutrient-replete vegetative cells. The diadinoxanthin–diatoxanthin
xanthophyll cycle was active in resting spores; the xanthophyll cycle was synchronized with a 14 h light:10 h dark photoperiod.
Also, the ratios of cellular content of diadinoxanthin and diatoxanthin to cellular content of chl a in resting spores were relatively high in high irradiance, and decreased gradually in conditions of darkness over long culture
periods. Under conditions of strong light and high temperature, most resting spores survived more than 40 d while nutrient-starved
vegetative cells died within 33 d. These results suggest that resting spore formation is a strategy for enhancing protection
and lowering metabolic rate for survival. These physiological changes accompanying spore formation enable resting spores not
only to overwinter but also to “oversummer” in the coastal euphotic layer.
Received: 23 March 1999 / Accepted: 11 August 1999 相似文献
10.
Juveniles of Leiognathus nuchalis were raised from fertilized eggs for up to 60 d and examined for luminescence activity. Almost all juveniles raised separately
from adults failed to produce detectable light. In contrast, a significant percentage (33 to 100%) of the juveniles became
luminescent in less than 48 h when they were either kept with adults or inoculated with a homogenate of the adult light organs.
The luminescence tended to increase with time after the treatments. These findings suggest that: (1) most of L. nuchalis offspring typically hatch and develop apo-symbiotically and (2) at least 45 d after hatching, juveniles can be infected with
symbiotic luminous bacteria from the light organ of adult fish, and thereby gain the ability to produce light.
Received: 16 February 1999 / Accepted: 21 September 1999 相似文献
11.
DNA sequence diversity of octopods was investigated using the mitochondrial cytochrome oxidase III gene (mtCOIII). DNA was
obtained from ethanol- or formalin-fixed tissue of 15 specimens belonging to Octopus mimus Gould, 1852, Octopus vulgaris Cuvier, 1797 and Scaeurgus unicirrhus d'Orbigny, 1840, from coastal waters of the Mediterranean (France), the southwestern Atlantic (Brazil), the Caribbean (Costa
Rica) and the southeastern/tropical Pacific (north Chile/Costa Rica). A 612 bp fragment of the mtCOIII gene was sequenced
and aligned to the orthologous sequences available from northeastern Pacific Octopus species. Possible phylogenetic relationships were reconstructed. The mtCOIII gene tree revealed two main clusters, one comprised
O. rubescens, O. dofleini and O. californicus, while the other included all O. vulgaris specimens, O. bimaculatus, O. bimaculoides and O. mimus. With one exception all South American haplotypes including O. bimaculatus and O. bimaculoides appeared as the sister group of the Mediterranean haplotype of O. vulgaris, indicating that most of the South American O. vulgaris specimens investigated would not belong to the recently redescribed species O. vulgaris restricted to the Mediterranean and eastern Atlantic. The treatment of O. mimus as a species distinct from Mediterranean O. vulgaris is supported by a high nucleotide divergence of 12.7%. Based on the mtCOIII gene tree the existence of cryptic species among
O. vulgaris-like octopods is suggested.
Received: 15 January 1999 / Accepted: 15 October 1999 相似文献
12.
We examined the genetic identities of 49 individuals of four species of eels in the genus Anguilla Shaw, A. anguilla, A. japonica, A. reinhardti and A. rostrata, using the random(ly) amplified polymorphic DNA (RAPD)-PCR technique. We used 15 random decamer primers. Out of the 22 148
amplification products detected, 454 markers were evaluated using Nei's distance coefficient, two numerical methods (neighbor-joining,
UPGMA), and phylogenetic analysis using parsimony (PAUP). Both numerical and parsimony methods were congruent and confirmed
the specific status of all four examined Anguilla species. In all dendrograms, all individuals of each of the species clustered together within four closed groups with highly
significant bootstrap values (between 97 and 100%). Additionally 1 to 18 species-specific monomorphic diagnostic fragments
were detected in three of the species; none were detected in A. anguilla. Mean interspecific genetic distances ranged from 0.384 to 0.559, with the minimum between A. anguilla and A. rostrata and the maximum between A. anguilla and A. reinhardti. Individuals collected at one locality and belonging to a single species did not cluster together, and neither were any diagnostic
monomorphic fragments found for individuals of single localities. This probably reflects a random dispersal of larvae in ocean
currents before they reach coastal waters. Among all possible species pairs, only the two Atlantic species were consistently
clustered in all dendrograms, with highly significant bootstrap values (100%). Additionally, we detected ten diagnostic markers
for this pair of eel species. From RAPD data, we suggest a phylogram which was routed by the descending analysis method: A. reinhardti appears to have been the first species to diverge from a putative common ancestor of the four eel species. Later, A. japonica separated from the hypothetical ancestor of the Atlantic species, which then split recently into A. anguilla and A. rostrata. The close relationship of A. anguilla and A. rostrata is indicated by their low genetic distance (GD = 0.384) and a high degree of shared RAPD fragments (SF = 71.2%); this compares with the following means for all other species pairs: ( = 0.531, = 44.2%). The prerequisites for using RAPD data for the reconstruction of phylogenies are discussed.
Received: 2 September 1999 / Accepted: 8 May 2000 相似文献
13.
Molecular phylogeny of mud crabs (Brachyura: Panopeidae) from the northwestern Atlantic and the role of morphological stasis and convergence 总被引:4,自引:0,他引:4
Mud crabs of the family Panopeidae are common organisms in coastal soft-bottom, vegetated, rubble, and oyster-bed communities
along the temperate and tropical coastlines of the American continent. Similar morphology among many species renders their
distinction and classification difficult. Here, we present phylogenies of western Atlantic Panopeidae based on DNA sequences
of the mitochondrial large subunit rRNA (16S; 529 basepairs) and cytochrome oxidase I (COI; 640 basepairs) genes. Results
suggest that the speciose genera Panopeus and Eurypanopeus are not monophyletic and that their taxonomy does not accurately reflect evolutionary partitions. In two cases (P. herbstii complex and E. depressus and allies), the molecular findings strongly support sister-species relationships that differ from previous morphology-based
assumptions. We suggest that convergence or morphological stasis are responsible for the phenotypic similarities between divergent
evolutionary lineages.
Received: 23 July 1999 / Accepted: 5 April 2000 相似文献
14.
The euryhaline mysid Neomysis integer (Peracarida: Mysidacea) is a common member of the hyperbenthos of the upper reaches of European estuaries. In the East Looe
River Estuary (Cornwall, England), this species experiences extensive tidal and seasonal changes in temperature (3 to 15 °C)
and salinity (1 to 34‰). In this investigation, the effects of temperature (5, 10 and 15 °C) and salinity (1, 10, 20 and 30‰)
on the oxygen consumption of male and female N. integer are reported, and are related to field measurements to identify the adaptive responses of the respiratory physiology to such
a variable environment. The general responses were similar for each sex; however, at any given temperature/salinity combination,
male N. integer consumed more oxygen than females. The general trends were increased oxygen consumption with increasing temperature (Q10 values ranged from ∼1.7 to 2.5) and decreased oxygen consumption with increasing salinity. Temperature and salinity interacted
at high water antagonistically to minimise changes in mysid oxygen-consumption. When related to tidal fluctuations in temperature
and salinity experienced by N. integer inhabiting the East Looe River Estuary, the results reveal how the respiratory physiology of this species is adapted to its
variable environment.
Received: 16 June 1998 / Accepted: 15 December 1998 相似文献
15.
Predators can have significant nonlethal effects on prey by modifying prey behaviour through chemically mediated interactions.
We examined behavioural responses of wood frog (Ranasylvatica) and American toad (Bufoamericanus) tadpoles to both direct and indirect chemical signals associated with a predatory odonate (Anaxjunius). In laboratory trials, tadpoles of both species responded strongly to water conditioned with Anax nymphs by decreasing foraging rates, becoming immobile, and moving away from the stimulus. The responses to water conditioned
with starved Anax versus Anax that fed on conspecific tadpoles did not differ significantly; these results suggest that tadpoles rely primarily on direct
signals to detect odonates. Rana did not respond to water conditioned with conspecific tissue extracts, while Bufo responded with behaviours that were indistinguishable from those of tadpoles exposed to Anax chemicals. In a field experiment, the responses of R. sylvatica tadpoles to Anax chemicals were similar to those of tadpoles observed in the laboratory. Collectively, our data indicate that tadpoles of
both species use chemical cues to assess predation risk from other community members. Tadpoles can selectively distinguish
members who pose a threat, and only evacuate food patches or reduce foraging rates when in danger. These behaviours appear
to be adaptive and are consistent with the predictions of optimality theory.
Received: 1 August 1997 / Accepted after revision: 22 November 1997 相似文献
16.
We describe the brood duration and marsupial development of three temperate coastal mysid species, Anisomysis mixta australis (Zimmer), Tenagomysis tasmaniae Fenton and Paramesopodopsis rufa Fenton, found commonly in Tasmanian waters. Larvae cultured in vitro had brood durations at 13 °C (17 °C) of 22 (15), 23 (15),
and 28 (20) d, respectively. Development through seven larval stages, and brood durations for these three species are similar
to those reported for coastal mysids from other temperate areas throughout the world.
Received: 10 June 1997 / Accepted: 1 July 1997 相似文献
17.
Hydrodynamic and chemical conditions during onset of a red-tide assemblage in an estuarine upwelling ecosystem 总被引:1,自引:0,他引:1
The hydrodynamics and nitrogen/silicon biogeochemistry accompanying the development of a red-tide assemblage were examined
in the Ría de Vigo (northwest Spain), a coastal embayment affected by upwelling, during an in situ diel experiment in September
1991. Despite a low N:Si molar ratio (0.5) of nutrients entering the surface layer, which was favourable for diatom growth,
the diatom population began to decline. Limited N-nutrient input, arising from moderate coastal upwelling in a stratified
water column, restricted net community production (NCP = 630 mg C m−2 d−1). In addition, light-limitation of gross primary production (GPP = 1525 mg C m−2 d−1) was observed. The relatively high f-ratio (= NCP:GPP) recorded (0.41, characteristic of intense upwelling conditions) would have been as low as 0.15 had not GPP
been limited by light intensity. Temporal separation of carbohydrate synthesis during the photoperiod from protein synthesis
in the dark could be inferred from the time-course of the C:N ratio of particulate organic matter. Severe light-limitation
would lead to diatom collapse were the diatoms not able to meet all their energy requirements during the hours of darkness.
Under the hydrodynamic, nutrient and light conditions of the experiment, an assemblage of red-tide-forming species began to
develop, aided by their ability to migrate vertically and to synthesize carbohydrates during the light in surface waters and
protein during the dark at the 4 m-deep pycnocline. Thermal stratification, reduced turbulence, intense nutrient mineralization,
and the limited nitrogen input through moderate upwelling were all favourable to the onset of a red-tide assemblage.
Received: 15 February 1997 / Accepted: 26 September 1997 相似文献
18.
F. Maltagliati A. P. Peru M. Casu F. Rossi C. Lardicci M. Curini-Galletti A. Castelli 《Marine Biology》2000,136(5):871-879
The genetic relationships between morphologically indistinguishable marine and brackish populations of Syllis gracilis Grube, 1840 (Polychaeta: Syllidae) were studied by means of allozyme electrophoresis. Samples of S. gracilis from marine coastal and brackish-water habitats were examined for variation at 13 presumptive loci. In addition, a sample
of the closely related species S. prolifera (Krohn, 1852) was analysed. Five loci were multiallelic in at least one population of S. gracilis and eight loci in S. prolifera. Low to moderate levels of within-population genetic variability were found, with average expected heterozygosity values
ranging from H = 0.068 (±0.043 SE) to 0.187 (±0.069 SE) in the populations of S. gracilis; higher values were found in S. prolifera (H = 0.325 ± 0.076). The presence of various private alleles indicated a marked genetic divergence among populations of S. gracilis, with Nei's genetic distances ranging from D = 0.000 to 0.833 and a highly significant F
ST value. Furthermore, evidence for strong genetic heterogeneity between two sympatric marine populations was found. UPGMA cluster
analysis and multidimensional scaling pointed out a clear genetic divergence between brackish and marine populations. At least
two genetically divergent entities occurred in marine and brackish habitats. This could be due to local adaptation of individuals
coming from marine populations to brackish habitats, but more presumably to the occurrence of a species complex within S. gracilis.
Received: 6 June 1999 / Accepted: 7 February 2000 相似文献
19.
Andrea Gori Sergio Rossi Cristina Linares Elisa Berganzo Covadonga Orejas Mark RT Dale Josep-Maria Gili 《Marine Biology》2011,158(8):1721-1732
In the Western Mediterranean Sea, the gorgonian Eunicella singularis (Esper, 1794) is found at high densities on sublittoral bottoms at depths from 10 to 70 m. Shallow colonies have symbiotic
zooxanthellae that deeper colonies lack. While knowledge of the ecology of the shallow populations has increased during the
last decades, there is almost no information on the ecology of the deep sublittoral populations. In October and November 2004
at Cap de Creus (42°19′12″ N; 03°19′34″ E), an analysis of video transects made by a remotely operated vehicle showed that
shallow populations (10–25 m depth) were dominated by small, non-reproductive colonies, while deep sublittoral populations
(50–67 m depth) were dominated by medium-sized colonies. Average and maximum colony heights were greater in the deeper populations,
with these deeper populations also forming larger patch sizes and more extensive regions of continuous substrate coverage.
These results suggest that shallow habitats are suitable for E. singularis, as shown by the high recruitment rate, but perturbations may limit or delay the development of these populations into a
mature stage. This contrasts with the deep sublittoral habitats where higher environmental stability may allow the development
of mature populations dominated by larger, sexually mature colonies. 相似文献
20.
Growth as an integrative parameter of all physiological processes was measured in young sporophytes of temperate Laminaria digitata, Laminaria saccharina and Laminaria hyperborea exposed in the laboratory to irradiance consisting of either only photosynthetically active radiation (PAR) or to a spectrum
including ultraviolet radiation (UVR) (PAR+UVA+UVB) by use of cut-off glass filters. Size increment was measured every 10 min
over a period of 18–21 days using growth chambers with on-line video measuring technique. In the chamber, plants were grown
at 10±2°C and 16:8 h light–dark cycles with 6 h additional UVR exposure in the middle of the light period. Tissue morphology
and absorption spectra were measured in untreated young sporophytes while chlorophyll a content and DNA damage were measured
in treated thalli at the end of the experiment. Sensitivity of growth under UVR was found to be related to the observed upper
depth distribution limit of the upper sublittoral L. digitata, upper to mid sublittoral L. saccharina and lower sublittoral L. hyperborea. Tissue DNA damage is, however, dependent on thallus thickness which minimizes UVR effect where outer cell layers shade inner
cells and provide longer pathlength for UVR. Exposure to UVR causes cellular, enzymatic and molecular damage. Presence of
UV-absorbing compounds further reduces effective UVR from reaching physiological targets. The cost of producing higher amount
of UV-absorbing compounds and effective DNA repair mechanism can, however, divert photosynthate at the expense of growth.
Tissue chlorophyll a content was not significantly different between treatments suggesting a capacity for acclimation to moderate
UVR fluence. Growth acclimation to repeated UVR exposure was observed within a period of 12 days while growth inhibition was
observed after a longer UVR exposure period of 21 days. The results give further insight into the effects of UVR on the cellular
level and show how ecological parameters such as the upper depth distribution limit are dependent on cellular processes. 相似文献