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1.
The gastropods Lepetodrilus fucensis and Depressigyra globulus are abundant faunal components of animal communities at deep-sea hydrothermal vents along the Juan de Fuca Ridge in the NE
Pacific. The population structure and recruitment pattern of both species were studied using modal decomposition of length–frequency
distributions. Gastropod populations were collected from Axial Volcano and Endeavour Segment in 2002 and 2003. Polymodal size–frequency
distributions, particularly at Axial Volcano vent sites, suggest a discontinuous recruitment pattern for D. globulus. In contrast, there were no distinct peaks visible in the distributions of L. fucensis, suggesting a continuous recruitment pattern for this species. For both species, distributions were positively skewed towards
the smaller length–classes, implying post-settlement mortality is high. However, variations in growth, due to short- and long-term
variability in environmental conditions in the hydrothermal vent habitat, as well as biological interactions, may also be
influencing the distribution and abundance of subsequent life-history stages. Using maximum shell lengths from populations
of known ages, the growth rate of L. fucensis was estimated as 9.6 μm day−1, indicating adulthood would be reached in ∼1 year. Our results suggest that, despite occupying the same habitat, abundance
and population structure are regulated by different biotic and abiotic processes in L. fucensis and D. globulus. 相似文献
2.
Green sea urchins, Strongylocentrotus droebachiensis OF Müller, collected off the coast of New Hampshire, USA, in late February 1995, were brought into the laboratory and fed
an artificial diet ad libitum, and subjected to a photoperiod advanced by 4 months. During this study, temperatures and salinities
for experimental urchins mirrored those recorded at the collection site. We examined the effects of changes in feeding regime
and photoperiod on gametogenesis and compared the experimental urchins with those from the source population. During the 7-month
period, experimental urchins showed no detectable changes in mean test height or diameter. Experimental urchins had a significantly
higher gonad index (GI) in March, April and May (18 ± 6%) compared with field urchins in March (11 ± 3%). Subsequently, experimental
urchins had a mean monthly GI of 25 to 30%, while the mean GI for field urchins was 11 to 13%. Gonial cell mitosis and gametogenesis
occurred earlier in experimental male and female urchins compared with field urchins. Stereological and histological observations
and stage–frequency data showed that the ovaries of experimental urchins were large because of the accelerated development
of nutritive phagocytes, the volume fraction (V
v) of which was 89 to 90% of the gonad, while new vitellogenic primary oocytes occupied <1% V
v. In males, stereological and histological observations and stage–frequency data suggested a mobilization of materials from
the nutritive phagocytes beginning between June and August, i.e. earlier than in females, and, by September, new gametes occupied
a V
v of 49 ± 3% of the testes. Oocyte size–frequency distributions demonstrated that most primary oocytes were <80 μm in diameter
between March and September, suggesting that cold temperatures may be needed for completion of vitellogenesis. We describe
changes in the two principal cell types in the germinal epithelium of urchin gonads and indicate how knowledge of their population
dynamics may be useful in aquaculture applications.
Received: 21 February 1997 / Accepted: 3 June 1998 相似文献
3.
Katsumasa Yamada Kazutaka Takahashi Carole Vallet Satoru Taguchi Tatsuki Toda 《Marine Biology》2007,150(5):905-917
Spatial and seasonal distribution pattern, life history and production of three species of Neomysis (Mysidacea) which commonly occur in northwestern subarctic Pacific coastal waters, were investigated throughout the year
in the Akkeshi-ko estuary, northern Japan. The most abundant species Neomysis awatschensis (annual mean density: 179.8 inds. m−2, biomass: 108.8 mg DW m−2) occurred at the inner part of the estuary including low salinity areas with no clear preference for the seagrass bed. The
second most abundant Neomysis mirabilis (mean density: 95.8 inds. m−2, biomass: 90.1 mg DW m−2) occurred at relatively saline seagrass site throughout the year. Occurrence of Neomysis czerniawskii in the estuary was limited to the seagrass bed during summer when their population mainly consisted of juveniles, suggesting
that this species is a seasonal migrant between the estuary and the marine environment. Both N. awatschensis and N. mirabilis populations were composed of two generation types, a larger sized overwintering and smaller sized spring/summer generations;
however, each species had a different reproductive strategy. N. awatschensis was characterized by fast growth to maturity at a smaller size than N. mirabilis with a relatively high fecundity during warm season, suggesting that this species is an r-strategist which can utilize opportunistically
a wide variety of habitats. In contrast, the seagrass bed resident N. mirabilis was a K-strategist which matures at a larger size producing fewer but larger offspring. The annual production of N. awatschensis (0.57–0.70 g DW m−2, mean of the whole estuary) and N. mirabilis (0.58–0.68 g DW m−2, mean of the seagrass bed) at their respective habitats was comparable. Consequently, species-specific life history and distribution
pattern are concluded to allow Neomysis spp. to coexist in the estuary and the high carrying capacity of seagrass bed is suggested to contribute to maintain their
high biomass level. 相似文献
4.
Amongst a plethora of threats to seagrass ecosystems, contamination with heavy metals may well be one of the most significant.
We therefore set out to track contamination levels with Cu, Zn, Pb and Cd in the principal autotrophic compartments and sediments
of a meadow of Posidonia oceanica in the Gulf of Naples, Mediterranean Sea. With respect to metal levels, leaves and their associated epibiota are certainly
not a homogenous compartment, as might perhaps be inferred from the common use of the term “leaf–epiphyte complex” in the
literature. Save for Cu, all metal species analysed showed appreciable differences in concentration between seagrass leaves
and epibiota. These results give strength to our argument that in ecotoxicological work leaves and epibiota should not be
treated as a single unit. Although absolute differences in trace-metal levels among sampling periods varied somewhat with
the specific component analysed (i.e. macrophyte organs, epibiota, sediment), an overall trend of markedly higher heavy-metal
levels during the winter season is a striking one. Whilst annual cycles in growth dynamics of the seagrasses explain a significant
fraction of the temporal variance, seasonality in productivity is a doubtful explanation for similar patterns in non-living
sedimentary components; consideration of additional variables therefore seems sensible. As variables with consistent explanatory
powers we suggest: (1) seasonal cycles in storm frequency and amplitude which remobilise metals bound in the sediments of
the sea floor, and (2) increased precipitation during the cold season which may significantly increase marine metal levels
through elevated weathering of rocks and elevated fluvial inputs of anthropogenic contaminant loads. Whereas Cd and Pb concentrations
in seagrass leaves from the Gulf of Naples fall within the range for coastal areas subjected to low levels of heavy-metal
pollution, Cu and Zn reach levels typical of highly contaminated regions, such as the waters bordering major coastal cities.
Any direct comparisons of the pollution status of seagrass beds between different geographic areas are, however, likely to
be confounded by the indiscriminate application of the “leaf–epiphyte complex”: the magnitude of the confounding effect depends
on the ratio of epibiota/leave biomass, time of sampling, and metal species analysed.
Received: 15 May 1997 / Accepted: 2 February 1998 相似文献
5.
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
6.
The role of different types of detached macrophytes in the food and habitat choice of a surf-zone inhabiting amphipod 总被引:1,自引:0,他引:1
Allorchestes
compressa is the dominant macroinvertebrate species in wrack accumulations on surf zones of south-western Australia. These amphipods
were provided with a choice of macrophyte material representing brown and red algae and seagrass in a series of preference
experiments in the laboratory and field. Feeding experiments showed that A. compressa exhibited a strong preference for particular types of macrophytes (P < 0.01). Amphipods primarily consumed brown algae, with 69–98% of the biomass of Ecklonia radiata and 64% of the biomass of Sargassum sp. lost over the experiments. This study has shown that the amphipod A. compressa exhibits a clear preference for brown algae over red algae and seagrass as food. In terms of habitat preference, tank experiments
using a series of pair-wise comparisons showed that, in the absence of fish predators, A. compressa selected seagrass as its preferred habitat over the other types of wrack (P < 0.001). When satiated or starved, between 68 and 83 and 79 and 98% of amphipods were found in Amphibolis and Posidonia, respectively. In contrast, field-cage experiments revealed that A. compressa preferred either mixed wrack, brown algae or red algae over seagrass as a habitat (P < 0.01). The contrasts between results from the laboratory and field suggest that other factors such as the presence of predators,
water flow and light could influence habitat choice in the surf zone. This study shows that allochthonous material transported
to surf zones from other habitats therefore play different roles in driving secondary production in this shoreline habitat. 相似文献
7.
Marieke C. Verweij Ivan Nagelkerken Suzanne L. J. Wartenbergh Ido R. Pen Gerard van der Velde 《Marine Biology》2006,149(6):1291-1299
Caribbean seagrass beds are important feeding habitats for so-called nocturnally active zoobenthivorous fish, but the extent to which these fishes use mangroves and seagrass beds as feeding habitats during daytime remains unclear. We hypothesised three feeding strategies: (1) fishes feed opportunistically in mangroves or seagrass beds throughout the day and feed predominantly in seagrass beds during night-time; (2) fishes start feeding in mangroves or seagrass beds during daytime just prior to nocturnal feeding in seagrass beds; (3) after nocturnal feeding in seagrass beds, fishes complete feeding in mangroves or seagrass beds during the morning. We studied the effect of habitat type, fish size, social mode and time of day on resting and feeding behaviour of large juvenile (5–10 cm) and sub-adult (10–15 cm) Haemulon flavolineatum in mangroves and seagrass beds during daytime. Sub-adults occurred in mangroves only, spent most time on resting, and showed rare opportunistic feeding events (concordant with strategy 1), regardless of their social mode (solitary or schooling). In contrast, large juveniles were present in both habitat types and solitary fishes mainly foraged, while schooling fishes mainly rested. Exceptions were small juveniles (±5 cm) in seagrass beds which foraged intensively while schooling. Large juveniles showed more feeding activity in seagrass beds than in mangroves. In both habitat types, they showed benthic feeding, whereas pelagic feeding was observed almost exclusively in the seagrass beds. In both habitat types, their feeding activity was highest during 8:00–10:30 hours (concordant with strategy 3), and for seagrass fishes, it was also high during 17:30–18:30 hours (concordant with strategy 2). The study shows that both mangroves and seagrass beds provide daytime feeding habitats for some life-stages of H. flavolineatum, which is generally considered a nocturnal feeder. 相似文献
8.
The colonization dynamics and life histories of pioneer species determine early succession at nascent hydrothermal vents,
and their reproductive ecology may provide insight into their dispersal and population connectivity. Studies on the reproductive
traits of two pioneer gastropod species, Ctenopelta porifera and Lepetodrilus tevnianus, began within a year after an eruption on the East Pacific Rise (EPR) that eliminated vent communities near 9°50′N from late
2005/early 2006. Standard histology was used to examine gamete release, instantaneous female fecundity, and time to maturation.
Both species exhibited two-component oocyte size–frequency distributions indicating quasi-continuous reproduction with high
fecundity. In samples collected in December 2006, both C. porifera and L. tevnianus individuals were reproductively mature. The smallest reproducing C. porifera were 4.2 mm (males) and 5.4 mm (females) in shell length, whereas reproductive L. tevnianus were smaller (2.3 and 2.4 mm in males and females, respectively). Most C. porifera were large (>6.0 mm) compared to their size at metamorphosis and reproductively mature. In contrast, most L. tevnianus were small (<1.0 mm) and immature. Reproductive traits of the two species are consistent with opportunistic colonization,
but are also similar to those of other Lepetodrilus species and peltospirids at vents and do not fully explain why these particular species were the dominant pioneers. Their
larvae were probably in high supply immediately after the eruption, due to oceanographic transport processes from remote source
populations. 相似文献
9.
Environmental salinity is important in defining Brachionus plicatilis sibling species distributions. However, while salinity influences distributions, sibling species often co-exist. Three different mechanisms potentially account for the partial co-occurrence of sibling species: (1) siblings have differing salinity tolerances that partially overlap; (2) siblings physiological tolerances may be commonly broad, but relatively small differences in tolerances differentiate distributions via interactions e.g. competition; or (3) siblings distributions may be influenced by physical factors other than salinity. Here, we assess the extent of salinity tolerance in three B. plicatilis sibling species (B. plicatilis 6TUR, B. plicatilis IOM and B. rotundiformis 6TOS) by measuring population growth rate (μ, day−1) and egg development time in response to salinity (5–60‰) and salinity fluctuations (≤ Δ40‰). Sibling species were identified by analysis of the mitochondrial COI gene, and salinity responses were compared by regression analysis. Responses differed significantly between siblings, although the broad trends were similar. Positive growth occurred at all salinities, and highest growth rates ranged between 0.93 and 1.08 day−1 at 16–18‰. Rapid changes in salinity reduced growth rates, but net mortality occurred only in one treatment (100% mortality on transfer from 10 to 40‰). Egg development time was largely invariant with salinity except for B. plicatilis IOM and where rotifers were transferred from 30 to 60‰. We indicate that several siblings are similarly euryhaline and tolerate salinity fluctuations. Undoubtedly, wide tolerances in B. plicatilis are adaptations to ephemeral and seasonally variable habitats. Given common broad salinity tolerances, it is unlikely that the differential distributions of sibling species are a direct result of physiological constraints. Instead, we illustrate using a simple model that subtle differences in physiological tolerances may have important impacts on interactions between sibling species, which may in turn influence distributions. 相似文献
10.
Early development was examined, under various salinities, for two sympatric nereidid polychaetes, Hediste japonica and H. diadroma, which participated in a simultaneous reproductive swarming in an estuary of the Omuta-gawa River in Ariake Sea, Japan. The
eggs of both species were isotonic to the medium of 27.5–30 psu salinity. The egg diameter in the isotonic salinity was 180–205 μm
in H. japonica, and 130–160 μm in H. diadroma. Successful development of most embryos was observed in a salinity range of 22.5–30 psu in both species, while successful
fertilization occurred in wider ranges of salinity, i.e., 10–34 psu in H. japonica and 10 to 30 psu in H. diadroma. In both species, free-swimming larval life started from the indistinct hatching of trochophores out of a jelly layer capsule.
The lecithotrophic development appeared to run to the 4-setiger nectochaetes in H. japonica, while to 3-setiger nectochaetes in H. diadroma, resulting in a shorter pelagic larval life in H. japonica. In a comparison of larval morphology among Hediste species, we found a definite negative correlation between the prostomium width, which represents the larval size and depends
on egg size, and relative length of chaetae to the prostomium width: the relative length of chaetae was the longest in H. diadroma (with the smallest egg size and long pelagic life), intermediate in H. japonica (intermediate egg size, short pelagic life), and the shortest in H. atoka (largest egg size, no true pelagic life). We also examined the possibility of hybridization between H. japonica and H. diadroma through cross-insemination experiments. The gametes of the two species were reciprocally compatible, and viable hybrid offspring
were produced by the laboratory crosses. The hybrid larvae expressed intermediate phenotypes, but with a greater maternal
influence in characteristics such as the relative length of chaetae and the lecithotrophic larval duration. 相似文献
11.
Disease resistance: a benefit of sociality in the dampwood termite Zootermopsis angusticollis (Isoptera: Termopsidae) 总被引:1,自引:0,他引:1
Rebeca B. Rosengaus Amy B. Maxmen Laran E. Coates James F. A. Traniello 《Behavioral ecology and sociobiology》1998,44(2):125-134
The benefit of sociality in relation to disease susceptibility was studied in the dampwood termite Zootermopsis angusticollis. Although contact with high concentrations of fungal conidia is lethal, the survivorship of nymphs exposed to spore suspensions
ranging from 6 × 106 to 2 × 108 spores/ml of the fungus Metarhizium anisopliae increased with group size. The survivorship (measured as LT50) of isolated individuals ranged from 3.0 to 4.8 days, but infected nymphs living in groups of 10 and 25 individuals survived
significantly longer (5.6–8.3 and 5.6–9.1 days, respectively). In most cases, there were no significant differences in the
survival distributions of the 10- and 25-termite groups. When nymphs were infected with concentrations of 7 × 101–7 × 104 spores/ml and allowed to interact with healthy nestmates, fungal infections were not contracted by the unexposed termites.
Moreover, infected termites benefitted from social contact with unexposed nestmates: their survival rates were significantly
higher than those of infected termites living with similarly infected nestmates. Allogrooming, which increased in frequency
during and after exposure to conidia, appeared to remove potentially infectious spores from the cuticle, thus increasing termite
survivorship. These results suggest that allogrooming plays a crucial role in the control of disease and its death hazard
in termites. The infection-reducing advantage of group living may have been significant in the evolution of social behavior
in the Isoptera.
Received: 18 March 1998 / Accepted after revision: 31 May 1998 相似文献
12.
James Nelson Rachel Wilson Felicia Coleman Christopher Koenig Doug DeVries Chris Gardner Jeff Chanton 《Marine Biology》2012,159(2):365-372
Seagrass meadows are among the most productive ecosystems in the marine environment. It has been speculated that much of this
production is exported to adjacent ecosystems via the movements of organisms. Our study utilized stable isotopes to track
seagrass-derived production into offshore food webs in the northeastern Gulf of Mexico. We found that gag grouper (Myctereoperca microlepis) on reefs as far as 90 km from the seagrass beds incorporate a significant portion of seagrass-derived biomass. The muscle
tissue of gag grouper, a major fisheries species, was composed on average of 18.5–25% seagrass habitat-derived biomass. The
timing of this annual seagrass subsidy appears to be important in fueling gag grouper egg production. The δ34S values of gag grouper gonad tissues varied seasonally and were δ34S depleted during the spawning season indicating that gag utilize the seagrass-derived biomass to support reproduction. If
such large scale trophic subsidies are typical of temperate seagrass systems, then loss of seagrass production or habitat
would result in a direct loss of offshore fisheries productivity. 相似文献
13.
The effects of salinity, temperature, and pH variations on growth, survival, and photosynthetic rates of the seagrass Halophila johnsonii Eiseman were examined. Growth and survival responses to salinity were characterized by aquarium experiments in which plants were exposed to seven different salinity treatments (0, 10, 20, 30, 40, 50, and 60 psu) during 15 days. Photosynthetic behavior was assessed for short-term salinity exposures (1 or 20 h) by incubation experiments in biological oxygen demand (BOD) bottles and by measuring photosynthesis versus irradiance (PI) responses in an oxygen electrode chamber. In the bottle experiments the possible effects of interactions between salinity and temperature (15, 25, and 35°C) or pH (5, 6, 7, and 8.2) were also examined. Growth and survival of H. johnsonii were significantly affected by salinity, with maximum rates obtained at 30 psu. Salinity also altered the parameters of the PI curves. Light-saturated photosynthesis (P
max) and the photosynthetic efficiency at subsaturating light (α) increased significantly up to an optimum of 40 psu, decreasing again at the highest salinities. Dark respiration rates and compensating irradiance (I
c) showed minimum values at 40 and 50 psu, while light-saturation point (I
k) was maximum at 30–50 psu. An interaction between salinity and temperature was not found although an increase of temperature alone produced an increase in α, P
max, respiration rates, and I
k. An interaction between salinity and pH was only found in the P
max response: P
max increased with pH=5 at 30 psu. In addition, reducing the pH increased α significantly. In the BOD bottles experiment a significant reduction in the dark respiration with decreasing pH was observed, but the opposite trend was observed in the photosynthetic rate. These results suggest that the endemic seagrass H. johnsonii could be negatively affected by hypo- or hypersalinity conditions, although salinity changes did not seem to alter the tolerance of this species to other environmental factors, such as temperature or pH. 相似文献
14.
Effect of periphyton grazing by Hydrobia ulvae on the growth of Zostera noltii on a tidal flat in the Dutch Wadden Sea 总被引:3,自引:0,他引:3
C. J. M. Philippart 《Marine Biology》1995,122(3):431-437
The decrease of the intertidal seagrass Zostera noltii in the Dutch Wadden Sea may have been the result of enhanced periphyton load due to eutrophication. Decrease of this seagrass species coincided with an increase in the mudsnail Hydrobia ulvae. Feeding of this mudsnail on periphyton may have partly counteracted an increase of periphyton biomass. Exclosure experiments on seagrass stands in the Dutch Wadden Sea in 1987 showed that density of periphyton on leaves of Z. noltii decreased significantly with increasing density of grazers. An increased density of mudsnails significantly enhanced the density and biomass of seagrass, in particular of the below ground parts. Since this seagrass species survives winter in temperate climate zones mainly by means of rhizomes, grazing may also influence the seagrass dynamics in the long term. Results of the experiment were in agreement with field observations on coinciding low densities of mudsnails and high densities of fouling of seagrass stands on the tidal flats of western Wadden Sea in the late 1970s. 相似文献
15.
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
16.
Mangrove forests and seagrass beds frequently occur as adjacent habitats in the temperate waters of southeastern Australia.
At low tide when fish cannot occupy mangroves they might utilise adjacent habitats, including seagrass. We first sampled small
fish from seagrass beds close to and far from mangroves in the Pittwater estuary, NSW, Australia. Seagrass beds close to mangroves
had a greater density of fish species than beds far from mangroves (close: mean 16.0 species net−1, SE 1.0; far: 13.2, 1.3; P < 0.05). In particular, juvenile fish were in greater densities near to than far from mangroves (close: 5.3, 0.4; far: 3.1,
0.4; P < 0.05). We then sampled the mangrove forests during the high tide and seagrass beds during the low tide, in beds along a
continuum of distances from mangroves. Multivariate analysis showed that fish assemblages differed with distance from mangroves,
and the differences were attributed to the composition of the fish assemblage (i.e. presence/absence of fish species), not
the abundances of individual species. In particular, fish that utilise mangrove forests at high tide were found in greater
species densities and species richness in seagrass nearer to mangroves. A negative relationship was found between the density
of mangrove-utilising fish species and the distance of the bed from mangroves (R
2 = 0.37, P < 0.05). This confirms the important connectivity between mangroves and seagrass for fish in temperate Australian waters. 相似文献
17.
Dana M. Bethea Loraine Hale John K. Carlson Enric Cortés Charles A. Manire James Gelsleichter 《Marine Biology》2007,152(5):1009-1020
To examine variation in diet and daily ration of the bonnethead shark, Sphyrna tiburo (Linnaeus 1758), animals were collected from three areas in the eastern Gulf of Mexico: northwest Florida (∼29°40′N, 85°13′W),
Tampa Bay near Anclote Key (∼28°10′N, 82°42.5′W), and Florida Bay (∼24°50′N, 80°48′W) from March through September, 1998–2000.
In each area, diet was assessed by life stage (young-of-the year, juveniles, and adults) and quantified using five indices:
percent by number (%N), percent by weight (%W), frequency of occurrence (%O), index of relative importance expressed on a
percent basis (%IRI), and %IRI based on diet category (%IRIDC). Diet could not be assessed for young-of-the-year in Tampa Bay or Florida Bay owing to low sample size. Diet analysis showed
an ontogenetic shift in northwest Florida. Young-of-the-year stomachs from northwest Florida (n = 68, 1 empty) contained a mix of seagrass and crustaceans while juvenile stomachs (n = 82, 0 empty) contained a mix of crabs and seagrass and adult stomachs (n = 39, 1 empty) contained almost exclusively crabs. Crabs made up the majority of both juvenile and adult diet in Tampa Bay
(n = 79, 2 empty, and n = 88, 1 empty, respectively). Juvenile stomachs from Florida Bay (n = 72, 0 empty) contained seagrass and a mix of crustaceans while adult stomachs contained more shrimp and cephalopods (n = 82, 3 empty). Diets in northwest Florida and Tampa Bay were similar. The diet in Florida Bay was different from those in
the other two areas, consisting of fewer crabs and more cephalopods and lobsters. Plant material was found in large quantities
in all stomachs examined from all locations (>15 %IRIDC in 6 of the 7 life stage-area combinations, >30 %IRIDC in 4 of the 7 combinations, and 62 %IRIDC in young-of-the-year diet in northwest Florida). Using species- and area-specific inputs, a bioenergetic model was constructed
to estimate daily ration. Models were constructed under two scenarios: assuming plant material was and was not part of the
diet. Overall, daily ration was significantly different by sex, life stage, and region. The bioenergetic model predicted increasing
daily ration with decreasing latitude and decreasing daily ration with ontogeny regardless of the inclusion or exclusion of
plant material. These results provide evidence that bonnetheads continuously exposed to warmer temperatures have elevated
metabolism and require additional energy consumption to maintain growth and reproduction.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
18.
A. S. Grutter 《Marine Biology》1999,135(3):545-552
The dynamics of infestation by parasitic juveniles of gnathiid isopods were investigated at Lizard Island in the summer of
1997/1998 to determine when, and at what rate, they infest fishes. Variation in gnathiid abundance on wild-caught fish (Hemigymnus melapterus) between dawn and sunset was examined, and unparasitized H. melapterus in cages were exposed to gnathiids in the field for 4 h (8 h for fish sampled at 06:00 h) at five different times of the
day and night (10:00, 14:00, 18:00, 22:00, 06:00 hrs) on three reefs. To control for any potential effect of the cleaner-fish
Labroides dimidiatus, which consumes large numbers of gnathiids each day, sampling was carried out on reefs from which all cleaner-fish had been
removed. Gnathiid abundance decreased during the day. Standardized abundance per wild-caught fish was 1.9 times higher at
dawn than at sunset. Gnathiids successfully infested fish in cages. Sixty-one percent of the fish in cages were infested with
≥1 gnathiids, with 51% of the fish having between 1 and 4 gnathiids after 4 h exposure. Gnathiids infested fish both day and
night. The log10 (abundance +1) of gnathiids per caged fish varied significantly between time periods, with higher gnathiid numbers on fish
sampled at 18:00, 22:00, and 06:00 hrs than on fish sampled at 10:00 and 14:00 hrs. In contrast to gnathiid abundance on wild-caught
fish, the number of gnathiids on caged fish sampled at sunset was as high as that at dawn. The estimated mean (SE) cumulative
number of gnathiids per caged fish [mean size = 13.7 cm (±0.25)] per day was 7.8 (1.1); this is similar to the estimated mean
number of 7.3 gnathiids on similar-sized wild-caught fish at 6:00 hrs. The high infestation rate of gnathiids on caged fish
in the late afternoon contrasted with the low numbers on wild-caught fish at this time, suggesting that factors other than
infestation behaviour may be responsible for the low numbers of gnathiids on wild-caught fish in the afternoon.
Received: 19 August 1998 / Accepted: 1 June 1999 相似文献
19.
The current contribution deals with the reproductive biology of a genus endemic to Brazil –Mussismilia Ortmann, 1890 – including all three species of the genus: M. braziliensis (Verrill, 1868), M. hartti (Verrill, 1868), and M. hispida (Verrill, 1902), which occur sympatrically in the studied area, the Abrolhos Reef Complex, Brazil. Sexuality patterns, modes
of reproduction, synchrony and spawning periods are reported, and were determined by histological examination of material.
All three species started to develop female and male gametes over different periods in the same breeding season. The three
species are probably broadcast spawners, since no embryos or planulae were observed in any species at any given time of the
year. Each reproductive cycle lasted approximately 11 months. Oogenesis and spermatogenesis started in different periods,
with spermaries appearing in approximately the eighth month of ovary development and lasting about 3 months. Reproductive
cycles were annual. Spawning probably occurred in consecutive months in each species. In M. braziliensis, spawning presumably happened between March and the middle of May in 1996 and 1997. Evidence suggested that spawning events
of M. hispida took place between the end of April and mid-June. M. hartti may have spawned between September and November. The data presented here suggested that all studied species have at least
one exclusive spawning period, asynchronically with the others. A possible exception may be the simultaneous (or close) spawnings
of M. braziliensis and M. hispida in May. It is suggested that asynchrony in spawning periods among species may reduce the chance of hybridization, gamete
waste and the competition for settlement surfaces. The occurrence of extended spawning periods for each species may also reduce
the risks of reproductive failure, due to temporary adverse conditions.
Received: 8 December 1998 / Accepted: 15 July 1999 相似文献
20.
Epibiosis on cerith shells in a seagrass bed: correlation of shell occupant with epizoite distribution and abundance 总被引:1,自引:0,他引:1
J. C. Creed 《Marine Biology》2000,137(5-6):775-782
The cerith Cerithium atratum (Born 1778) is an abundant gastropod in the seagrass beds at Cabo Frio, Brazil. In order to estimate the ecological importance
of cerith shells as a rare hard substratum in the seagrass bed, the abundances of C. atratum and of cerith shells occupied by hermit crabs were quantified. The mean densities of C. atratum and hermit crabs were 1887 and 100 individuals m−2, respectively, and these provided 0.5 m2 shell area m−2 available for epizoite colonization. The tube-forming polychaete Hydroides plateni (Kinberg 1867) and oyster Ostrea puelchana Orbigny, 1841 were the dominant visible epizoites on inhabited cerith shells. These epizoite populations were compared in
order to investigate whether the temporal and spatial patterns in the epibiotic community were related to ecological and behavioral
aspects of the occupant species (cerith or hermit crab). Larger cerith shells had a greater abundance of epizoites. Each epizoite
showed a preference for a different occupant of the shells (the oyster for C. atratum and the polychaete for cerith shells occupied by hermit crabs). The oyster showed a seasonal pattern in abundance on C. atratum, being more common in fall (March–April). The distribution of the epizoites on the shells depended on the shell occupant
species and was probably related to their different foraging activity –C. atratum ploughs half buried through the sediment, while the hermit crab crawls on the sediment surface. In both cases, the activity
of the shell occupant was considered to be beneficial to the epizoites, as empty shells and shell fragments did not support
a macroepifauna.
Received: 1 May 2000 / Accepted: 8 August 2000 相似文献