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1.
Combined effects of temperature and salinity on embryos and larvae of the northern bay scallop Argopecten irradians irradians 总被引:1,自引:0,他引:1
The combined effects of temperature and salinity on embryonic development and on larval survival and growth to setting size of the northerm bay scallop Argopecten irradians irradians (Lamarck) were studied in the laboratory. A 6x6 complete factorial design was used; temperatures ranged from 10° to 35°C, at 5C° intervals, and salinities ranged from 10 to 35S, at 5S intervals. Response-surface contour diagrams were generated to provide estimates of conditions for optimal responses. Normal development of embryos occurred over a very narrow range of temperature and salinity. Survival of larvae occurred over a wider range of temperature and salinity than did embryonic development or growth of larvae. Satisfactory growth (>70% of the maximum observed value) occurred only at high temperature-high salinity conditions; optimal conditions for survival occurred at similar salinities, but at slightly lower temperatures. Temperatures of 35°C or greater and/or salinities of 10S or less were lethal for all life stages studied. Both salinity and temperature exerted significant effects on development and survival, but temperature was clearly the dominant factor influencing growth. It is suggested that northern bay scallop embryos and larvae be reared at their respective optimal temperature-salinity levels so as to increase efficiency of aquaculture operations.This paper is adapted from a thesis submitted to the College of Fisheries, University of Washington, in partial fulfillment of the requirements for the MS degree. This study was conducted at the NMFS Laboratory in Milford, Connecticut, USA 相似文献
2.
Specimes of bay scallops, Argopecten irradians, collected from shallow-water eel-grass beds near Beaufort, North Carolina (USA) in September 1979, were exposed to 0.7 ppm cadmium in flowing seawater for 5 d. This exposure resulted in a massive extrusion of the calcified concretions of most of the kidney epithelial cells, although marked morphological damage consisting of cytoplasmc degeneration was apparent in only a few focal areas of the kidney. In addition, unique cytoplasmic membrane-bound bodies were observed in epithelial cells of cadmium-treated but not control scallop kidneys. In some cells, these bodies appeared to fuse with the main concretion vacuole. Kidneys of cadmium-treated scallops accumulated cadmium to 200 ppm on a wet wt basis; of this 60% was associated with concretions (2 000 ppm dry wt) and 38% with the membranous pellet obtained after ultracentrifugation at 105 000 g for 1 h. Approximately 2% of total kidney cadmium was associated with the cytosolic fractions but, unlike zinc or manganese, which were bound to either high or low molecular weight species, a large component of the cadmium in this fraction was bound to a protein peak of approximately 21 000 daltons. Results of this study indicate that kidney concretions of A. irradians play a major role in the control of renal cadmium accumulation and excretion and hence the toxicity of cadmium to this organism. 相似文献
3.
The relationships among multiple-locus heterozygosity, age, reproduction and growth were examined over the ca. 2-yr lifespan of a cohort of northern bay scallops, Argopecten irradians irradians (Lamarck), from the Niantic River estuary, Connecticut, USA. Electrophoretic analyses revealed a relatively low proportion of polymorphic loci (=0.35) and low level of heterozygote deficiency ( D. across 6 loci=-0.05) in this population. Allele frequency distributions showed a high degree of temporal stability within and among cohorts. No significant correlation was found between multiple-locus heterozygosity and either somatic or reproductive growth. Our results lend support to the postulated linkage between low heterozygote deficit and lack of a heterozygosity/growth association in marine bivalves, and in the pectinid group in particular. Partial reproductive senility occurs in these scallops in their second year of life. Somatic tissue weight increased exponentially with increasing shell height, whereas pre-spawning gonad mass attained asymptotic values in 2-yr-old scallops. Thus, weight-specific reproductive effort was significantly lower in second- than first-year scallops (24 and 33% respectively). This pattern could be generated if high individual reproductive effort in the first year were correlated with accelerated (early) post-reproductive senescence. This kind of resource allocation, in which somatic growth is given precedence over reproductive growth in older individuals, has been previously reported in only one other bivalve, a pectinid (Chlamys islandica), in which the decline in reproductive effort occurs only after the scallops reach an age of ca. 20 yr. 相似文献
4.
R. E. Palmer 《Marine Biology》1980,58(1):15-23
Shell morphology and ultrastructure were examined in the bay scallop Argopecten irradians, cultured in recirculating seawater systems under various conditions of feeding, lighting, and handling. On a unialgal diet of Thalassiosira pseudonana, scallop growth ranged from 120 to 183 m d-1 at 20°C in the laboratory, about two-thirds of the growth rate found in the field. However, shell deposited in the laboratory differed from that in the field in several ways. In the field, scallops formed costae as an unpigmented, corrugated marginal shell layer; shell deposited in the laboratory lacked this layer and was therefore darker. Also, microstructure of the exterior shell surface of field scallops was coarsely granular, while that of cultured scallops was relatively smooth. Excessive handling of scallops in the laboratory resulted in marginal thickening of valves, a deformity which was completely arrested by a change from daily to weekly handling. Scallops cultured in the same tank with oysters developed shell-thickening on the interior of the valves. It is postulated that shell abnormalities in bivalves result from disruption of complex behavioral processes associated with shell deposition and may be elicited by a variety of natural and experimental irritants. Under natural lighting regimes and optimal conditions for growth, scallops deposited exactly one shell increment per day, but under continuous lighting, deposition of growth increments often became aphasic. In one 28-d experiment, there was a strong correlation between number of growth increments formed and increase in shell height, suggesting that shell ridge formation occurred intermittently, rather than daily, when shell growth rates fell below approximately 150 m d-1. 相似文献
5.
The edge effect is usually considered to be the proximate cause of area sensitivity in forest birds. We tested if birds nesting in large patches are less vulnerable to the edge effect using a simple model that assumes an increase in patch size reduces the probability of a matrix predator moving to the core areas of forest and that larger perimeter/area ratios result in a higher number of matrix predators per unit of area. The probability of a nest being successful decreased asymptotically with an increase in either the patch penetration distance of predators or predator density, but those effects were reduced when patch size was increased. Large patches have a lower probability of being affected by an Allee effect and they can function as sink habitats only if penetration distance and predator density are largely increased. However, the transition from an Allee effect to a sink condition occurs with a small increase in penetration distance and predator density. Since birds nesting in large patches are less vulnerable to an increase in matrix predator populations, persistence of bird populations may be possible by increasing the size of habitat patches that can act as source populations. 相似文献
6.
Seagrasses are threatened by multiple anthropogenic stressors, such as accumulating drift algae and increasing temperatures
(associated with eutrophication and global warming, respectively). However, few seagrass experiments have examined whether
exposure to multiple stressors causes antagonistic, additive, or synergistic effects, and this has limited our ability to
predict the future health status of seagrass beds. We conducted a laboratory experiment to test whether abundance of Gracilaria comosa (3 levels; 0, 1.2, and 3.4 kg WW m−2), an algae that is resistant to wide environmental fluctuations (e.g. light, temperature, salinity, and oxygen levels), has
negative effects on the small ephemeral seagrass, Halophila ovalis and whether the effects are exacerbated by high temperature (3 levels; 20, 25, and 30°C). We found an additive negative effect
of the two stressors when tested simultaneously on 14 seagrass performance measures, with most data variability explained
by the drift algae. For the individual plant performance measures (above- and below-ground growth and mortality, leaf area,
internode distance, and root length and root volume), we found 5 additive effects, 4 synergistic effects, and 5 effects that
were significant only for drift algae. We also documented a significant additive effect of drift algae and temperature on
dissolved porewater sulphide (DS). A follow-up correlation analysis between DS and the 14 plant performance measures revealed
significant or near-significant linear correlations on 9 of these responses (above- and below-ground growth, leaf area and
weight, leaf mortality, and internode distance). In summary, we showed (a) that a stress-resistant drift algae can have strong
negative effects on a small ephemeral seagrass, (b) this negative effect can increase both additively and synergistically
with increasing temperature depending on performance measure, and (c) the negative effects may be mediated by a build-up of
porewater DS. An implication of our findings is that resource managers aiming to preserve healthy seagrass beds in an almost
certain future warmer world should increase efforts to keep drift algae populations low. 相似文献
7.
Collections of fishes from seagrass meadows along the coast of the Republic of Panamá and the Canal Zone during 1974–1975 revealed that juveniles of reefassociated predators are common in this habitat. There are also important diurnal changes in species composition: members of the families Pomadasyidae, Lutjanidae, Sciaenidae, Apogonidae and Muraenidae were noticeably more abundant in the seagrass meadows at night. Although there were significant differences in species composition and abundance among sampling sites, seasonal differences within sites appeared to be insignificant. The ichthyofauna of the Panamanian seagrass beds is significantly richer than that of similar habitats which have been studied in the Gulf of Mexico. This difference in species richness appears to be due in part to the influence of nearby coral reefs, which add an additional structural dimension to the habitat. 相似文献
8.
Weight specific rates of oxygen consumption carbon dioxide production, and ammonia-N excretion, measured for a Florida population of the bay scallop Argopecten irradians concentricus between May and September, 1982 and October and November, 1983 were significantly correlated (P<0.0005) to environmental factors that co-varied seasonally with metabolic shifts related to reproduction. Mean O/N and CO2/O2 (RQ) molar ratios indicates that scallop energy metabolism varied over the course of the reproductive cycle. Resting stage individuals (May-early June) had RQ values close to 0.7, indicative of a predominantly lipid-based metabolism. During the initial stages of gametogenesis (late June-early July) scallops catabolized primarily carbohydrate, as evidenced by maximum O/N (>22) values and RQ values close to 1.0 RQ values >1.0 indicated a possible carbohydrate to lipid conversion during the period of cytoplasmic growth (late July-early September). As gametes matured and spawning commenced (late September-November), metabolism became primarily protein based, as indicated by O/N and RQ values around 9.0 and 0.8, respectively. This pattern of substrate catabolism supports existing data on the storage and utilization of specific energy reserves with respect to reproduction in this species. 相似文献
9.
Previous studies have shown that large numbers of ciliated and nonciliated epithelial cells (diam.: 6 to 15 μm) are released
by adult sea scallops, Placopecten magellanicus (Gmelin), during summer months in Newfoundland when water temperatures are at a maximum and gonads are well developed. Such
exfoliation of cells could be a response to stresses associated with elevated water temperatures and/or spawning activity.
In the present study an electronic particle counter/sizer was used to further investigate the factors that influence exfoliation
of epithelial cells by juvenile and adult scallops throughout the year. We observed release of epithelial cells from juveniles,
and from adults collected in months when gametogenic activity was minimal, indicating that exfoliation does not occur as a
result of reproductive activity alone. SEM analysis revealed little difference in surface characteristics of the gills, mantle
and gonad between scallops that had released cells and those that had not, suggesting that exfoliation of small numbers of
cells may be a consequence of cellular turnover and normal physiological function. Adult scallops were monitored in a second
experiment to determine the effects of raising water temperatures from 8.5 to 14.7 and to 21.0 °C on the frequency (proportion)
and rate of cellular exfoliation. Only at the highest experimental temperature (21.0 °C) were exfoliation rates significantly
higher than rates recorded at 8.5 or 14.7 °C. SEM analyses revealed some damage to gill, mantle and gonad tissues when scallops
were exposed to 14.7 and then to 21.0 °C for a total of 8 d.
Received: 21 August 1996 / Accepted: 13 September 1996 相似文献
10.
Synergistic interactions between edge and area effects in a heavily fragmented landscape 总被引:5,自引:0,他引:5
Both area and edge effects have a strong influence on ecological processes in fragmented landscapes, but there is little understanding of how these two factors might interact to exacerbate local species declines. To test for synergistic interactions between area and edge effects, we sampled a diverse beetle community in a heavily fragmented landscape in New Zealand. More than 35,000 beetles of approximately 900 species were sampled over large gradients in habitat area (10(-2) 10(6) ha) and distance from patch edge (2(0)-2(10) m from the forest edge into both the forest and adjacent matrix). Using a new approach to partition variance following an ordination analysis, we found that a synergistic interaction between habitat area and distance to edge was a more important determinant of patterns in beetle community composition than direct edge or area effects alone. The strength of edge effects in beetle-species composition increased nonlinearly with increasing fragment area. One important consequence of the synergy is that the slopes of species area (SA) curves constructed from habitat islands depend sensitively on the distance from edge at which sampling is conducted. Surprisingly, we found negative SA curves for communities sampled at intermediate distances from habitat edges, caused by differential edge responses of matrix- vs. forest-specialist species in fragments of increasing area. Our data indicate that distance to habitat edge has a consistently greater impact on beetle community composition than habitat area and that variation in the strength of edge effects may underlie many patterns that are superficially related to habitat area. 相似文献
11.
12.
R. Michael Erwin David F. Brinker Bryan D. Watts Gary R. Costanzo David D. Morton 《Journal of Coastal Conservation》2011,15(1):51-60
Like many resources in the Chesapeake Bay region of the U.S., many waterbird nesting populations have suffered over the past three to four decades. In this study, historic information for the entire Bay and recent results from the Tangier Sound region were evaluated to illustrate patterns of island erosion and habitat loss for 19 breeding species of waterbirds. Aerial imagery and field data collected in the nesting season were the primary sources of data. From 1993/1994 to 2007/2008, a group of 15 islands in Tangier Sound, Virginia were reduced by 21% in area, as most of their small dunes and associated vegetation and forest cover were lost to increased washovers. Concurrently, nesting American black ducks (Anas rubripes) declined by 66% , wading birds (herons-egrets) by 51%, gulls by 72%, common terns (Sterna hirundo) by 96% and black skimmers (Rynchops niger) by about 70% in this complex. The declines noted at the larger Bay-wide scale suggest that this study area maybe symptomatic of a systemic limitation of nesting habitat for these species. The island losses noted in the Chesapeake have also been noted in other Atlantic U.S. coastal states. Stabilization and/or restoration of at least some of the rapidly eroding islands at key coastal areas are critical to help sustain waterbird communities. 相似文献
13.
The blue mussel, Mytilus edulis, is the most conspicuous animal species in the northern Baltic rocky sublittoral. In the studied area the species lives at the margin of its salinity tolerance. Although dwarfed by the low-salinity conditions, blue mussels in the northern Baltic are very abundant and have a decisive role in the benthic and pelagic ecosystems. We studied abundance, size distribution, biomass and growth rate of blue mussels along a 270 km salinity gradient in the northern Baltic Sea. Samples (n=317, 1998-1999) from moderately exposed and exposed rocky shores at seven study areas were collected in the southern Archipelago Sea in the west and into the central Gulf of Finland in the east, where the species is becoming increasingly rare. The results show a marked decline in mean mussel size and biomass from the saline west to the less saline east. The growth rate also decreased with lower ambient salinity. However, abundance of small mussels was considerably higher in the central and eastern parts of the study area. Vertically, the highest biomass was recorded at intermediate depths (5 and 8 m), being lower at both shallower (3 m) and deeper bottoms (12 m). It is concluded that salinity is the foremost factor determining size structure and growth rate among populations within the area. The results suggest that predation further influences the population structure of blue mussels living at the edge of their range in the central Gulf of Finland ultimately set by their salinity tolerance. 相似文献
14.
Heterozygosity and growth rate have been correlated in many molluscs, although the phenomenon is not universal. Enhanced growth of heterozygous molluscs has been attributed to lower energetic requirements for basal metabolism. We have investigated heterozygote deficiency, and the correlation between single-locus and multiple-locus heterozygosity and phenotype in juveniles of the scallop Placopecten magellanicus (Gmelin). Six samples were collected between 22 November 1984 and 11 December 1985 at Passamaquoddy Bay, New Brunswick, Canada. On average, heterozygote deficiency was small, although somewhat higher at the octopine dehydrogenase (Odh) locus, and decreased with age. No correlation was observed between genotype and growth rate. This result and published records indicate that allozyme heterozygosity of pectinids does not influence growth to the same degree as in other bivalves. However, we have observed in P. magellanicus a correlation between allozyme heterozygosity and octopine accumulation, a trait that relates to functional anaerobiosis, and may be related to the scallop's scope for movement. We combine these results and results from the literature into a model that relates the hypothesis of associative overdominance (at the population genetics level) with the hypothesis of energetic efficiency (at the physiological level). The model assumes that energy savings attributed to heterozygosity are used to maximize fitness. In freely moving molluscs this results in enhanced activity (such as searching for prey or swimming away from a predator), and in sessile molluscs either in enhanced somatic growth in juveniles or gonadal growth in adults. 相似文献
15.
By means of multivariate techniques, we studied: (1) the differences in the structure of bentho-demersal, non-cryptic, fish
assemblages associated with unvegetated sandy substrates, vegetated meadows constituted by the seagrass Cymodocea nodosa and the bottoms under the influence of sea-cage fish farms; as well as (2) the persistence of these patterns with regard
to different scales of spatial variability, across three islands of the Canarian Archipelago (Central East Atlantic). Our
sampling strategy (involving three islands, with five locations per island, and two sites within each location) detected significant
changes in the composition and structure of the fish assemblages between the three habitats. Fish assemblages associated with
the unvegetated and vegetated bottoms were similar among the surveyed islands. In contrast, we observed a significant inter-island
variability in the fish populations associated with the sea-cage fish farms. The presence of the sea-cage fish farms increased
the overall fish abundance (184.8±49.8 ind 100 m−2) as compared to both the vegetated (38.8±9.7 ind 100 m−2) and unvegetated habitats (1.1±0.4 ind 100 m−2). Differences within and between the habitats were found to be associated with the relative abundance of a few fish species.
The most abundant species were Xyrichthys novacula in the unvegetated bottoms and Diplodus annularis, Spondyliosoma cantharus and Mullus surmuletus on the seagrass meadows. Finally, we recorded an increase in the abundance of Heteroconger longissimus, Trachinus draco and Pagellus acarne in the bottoms beneath the sea-cage fish farms. These species, in addition to a group of large benthic chondrichthyes, were
responsible for the differences between islands in the composition and structure of the demersal ichthyofauna beneath the
sea-cage fish farms. 相似文献
16.
E. Balestri 《Marine Biology》2004,145(1):61-68
Sexual reproduction in Posidonia oceanica (L.) Delile is likely to be highly variable both in space and time. However, there has been little effort to identify at what spatial scale variability exists in the distribution and abundance of reproductive shoots or the magnitude of these variations. Such information is important for elucidating several aspects of the reproductive strategy of this species. Here, by using a reconstructing technique, I estimated the rate at which flowering events occurred over the last decades in three P. oceanica meadows along the coastline of the north-western Mediterranean (Italy). Then, variation in inflorescence frequency (i.e. the percentage of shoots that flowered in a particular year of the total number of shoots present in the sample in that year) was examined on a hierarchy of spatial scales, ranging from a few metres to meadows separated by tens of kilometres over a 3-year period. Separate analyses were also conducted to examine the patterns of spatial variability of several plant characteristics (i.e. shoot age and density of vegetative shoots) that may influence the timing of flowering. In total, ten reconstructed flowering events were recorded during the period 1983–1999. Despite the similar climatic conditions experienced in the three meadows surveyed, no inflorescence scars were found in one meadow. In the other two meadows, the flowering rate fluctuated considerably from year to year (0–26%), and simultaneous flowerings were detected only in 3 years (1993, 1994 and 1995). The pattern of spatial variability in the inflorescence frequency varied among years. An investigation of the flowering events recorded along the north-western Mediterranean coast reveals that in the studied period flowering also occurred across a broad range of meadows. Therefore, flowering could be a far more widespread phenomenon in this sector of the Mediterranean basin than previously thought. Analysis of variance showed significant variation in 1993 at the mean inflorescence frequency on very small scales (metres to tens of metres), whereas variation was not found at any of the scales investigated in 1994 and 1995. Overall, variation in the inflorescence frequency within individual meadows (65–93%) was at least an order of magnitude greater than that among separate meadows (0.5–19%). Patterns of spatial variation in the plant characteristics examined did not reflect those of flowering. It may be hypothesised that internal rhythms of populations, in conjunction with changes in environmental conditions, which are consistent over relatively large spatial (kilometres), are involved in the control of flowering induction. Environmental heterogeneity (in terms of nutrient availability) on a very local scale (metres to tens of metres) and intrinsic factors might affect the distribution of reproductive shoots within P. oceanica meadows.Communicated by R. Cattaneo-Vietti, Genova 相似文献
17.
The sublethal effects of a detergent on the reproduction,development, and settlement in the polychaetous annelid Capitella capitata 总被引:1,自引:0,他引:1
The effect of polyethylene-glycol fatty acid was studied on the various stages throughout the life cycle of Capitella capitata. All concentrations tested reduced the number of trochophores, metatrochophores, and young benthic worms and increased the time required to reach the next stage in an inverse relationship to concentration. Only the higher concentrations of detergent influenced the survival rate and the number of eggs produced and laid. A 90% decrease in the number of benthic worms produced occurred between the control and the highest concentration employed (100 mg/l). The effect of the detergent was similar in field and laboratory-collected larvae. 相似文献
18.
J. Gilmour 《Marine Biology》1999,135(3):451-462
Laboratory and field experiments were used to determine whether high (≃100 mg l−1), low (≃50 mg l−1) and control (≃0 mg l−1) levels of suspended sediment affected fertilisation, larval survival, and larval settlement in the scleractinian coral Acropora digitifera (Dana, 1846). Both high- and low-sediment treatments significantly decreased fertilisation, but post-fertilisation embryonic
development was not inhibited by suspended sediments. Larval survival and larval settlement were significantly reduced in
high- and low-sediment treatments. No difference was found between high- and low-sediment treatments in any of the three post-spawning
processes investigated, suggesting that they are susceptible to sediment concentrations which are not exceptionally high even
under natural conditions (>50 mg l−1). The introduction of an additional stress in the form of high levels of suspended sediments coupled with naturally high
variability in recruitment may have a considerable effect on the successful supply and settlement of coral larvae to a reef.
Given that many coral communities are open reproductive systems, the consequences of disturbance events are not likely to
be restricted to the impact area. Recruitment to a population may be reduced significantly in the presence of high levels
of suspended sediments because of effects on larval survival and settlement. Recruitment of larvae to adjacent populations
may also be affected due to a decreased fertilisation success and potential increases in mortality of larvae passing through
the affected site.
Received: 13 August 1998 / Accepted: 22 July 1999 相似文献
19.
Bacterial abundance, production, and extracellular enzyme activity were determined in the shallow water column, in the epiphytic
community of Thalassia
testudinum, and at the sediment surface along with total carbon, nitrogen, and phosphorus in Florida Bay, a subtropical seagrass estuary.
Data were statistically reduced by principle components analysis (PCA) and multidimensional scaling and related to T. testudinum leaf total phosphorus content and phytoplankton biomass. Each zone (i.e., pelagic, epiphytic, and surface sediment community)
was significantly dissimilar to each other (Global R = 0.65). Pelagic aminopeptidase and sum of carbon hydrolytic enzyme (esterase, peptidase, and α- and β-glucosidase) activities
ranged from 8 to 284 mg N m−2 day−1 and 113–1,671 mg C m−2 day−1, respectively, and were 1–3 orders of magnitude higher than epiphytic and sediment surface activities. Due to the phosphorus-limited
nature of Florida Bay, alkaline phosphatase activity was similar between pelagic (51–710 mg P m−2 day−1) and sediment (77–224 mg P m−2 day−1) zones but lower in the epiphytes (1.1–5.2 mg P m−2 day−1). Total (and/or organic) C (111–311 g C m−2), N (9.4–27.2 g N m−2), and P (212–1,623 mg P m−2) content were the highest in the sediment surface and typically the lowest in the seagrass epiphytes, ranging from 0.6 to
8.7 g C m−2, 0.02–0.99 g N m−2, and 0.5–43.5 mg P m−2. Unlike nutrient content and enzyme activities, bacterial production was highest in the epiphytes (8.0–235.1 mg C m−2 day−1) and sediment surface (11.5–233.2 mg C m−2 day−1) and low in the water column (1.6–85.6 mg C m−2 day−1). At an assumed 50% bacterial growth efficiency, for example, extracellular enzyme hydrolysis could supply 1.8 and 69% of
epiphytic and sediment bacteria carbon demand, respectively, while pelagic bacteria could fulfill their carbon demand completely
by enzyme-hydrolyzable organic matter. Similarly, previously measured T. testudinum extracellular photosynthetic carbon exudation rates could not satisfy epiphytic and sediment surface bacterial carbon demand,
suggesting that epiphytic algae and microphytobenthos might provide usable substrates to support high benthic bacterial production
rates. PCA revealed that T. testudinum nutrient content was related positively to epiphytic nutrient content and carbon hydrolase activity in the sediment, but
unrelated to pelagic variables. Phytoplankton biomass correlated positively with all pelagic components and sediment aminopeptidase
activity but negatively with epiphytic alkaline phosphatase activity. In conclusion, seagrass production and nutrient content
was unrelated to pelagic bacteria activity, but did influence extracellular enzyme hydrolysis at the sediment surface and
in the epiphytes. This study suggests that seagrass-derived organic matter is of secondary importance in Florida Bay and that
bacteria rely primarily on algal/cyanobacteria production. Pelagic bacteria seem coupled to phytoplankton, while the benthic
community appears supported by epiphytic and/or microphytobenthos production. 相似文献
20.
The regeneration rate of arms of the infaunal brittlestar Ophiophragmus filograneus was determined in natural and planted beds of the seagrass (Halodule wrighttii) in Tampa Bay, Florida, USA in 1990. Annually, brittlestar densities did not differ on average between the two beds, but they did show marked differences on individual dates. Rates of arm loss could not be determined for the two sites separately, but were estimated for the entire area. Between 52 and 94% of the brittlestars collected showed evidence of arm regeneration. Approximately one-third of those collected were regenerating one arm, with smaller proportions regenerating two or more arms. Regeneration rate was greater overall for individuals that had lost more tissue; however, the rate of soft-tissue regeneration per arm regenerated was significantly greater for those that had lost one arm compared to those that had lost three arms. The rate of soft-tissue regeneration did not differe between individuals from the two seagrass beds, and regeneration rate was lower than reported for other infaunal brittlestars. Skeletal regeneration per arm was similar in both arm-removal treatments. This result supports the hypothesis that echinoderm skeleton is energetically inexpensive and may help to lengthen arms during early regeneration. The rate of skeletal production was three-fold greater in individuals from the planted seagrass than in those from the natural. bed. As increased skeletal regeneration requires some additional energy, this indicates a greater energy expenditure and differential allocation by brittlestars regenerating in the planted seagrass areas. 相似文献