首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 109 毫秒
1.
Three quarters of the global human population will live in coastal areas in the coming decades and will continue to develop these areas as population density increases. Anthropogenic stressors from this coastal development may lead to fragmented habitats, altered food webs, changes in sediment characteristics, and loss of near-shore vegetated habitats. Seagrass systems are important vegetated estuarine habitats that are vulnerable to anthropogenic stressors, but provide valuable ecosystem functions. Key to maintaining these habitats that filter water, stabilize sediments, and provide refuge to juvenile animals is an understanding of the impacts of local coastal development. To assess development impacts in seagrass communities, we surveyed 20 seagrass beds in lower Chesapeake Bay, VA. We sampled primary producers, consumers, water quality, and sediment characteristics in seagrass beds, and characterized development along the adjacent shoreline using land cover data. Overall, we could not detect effects of local coastal development on these seagrass communities. Seagrass biomass varied only between sites, and was positively correlated with sediment organic matter. Epiphytic algal biomass and epibiont (epifauna and epiphyte) community composition varied between western and eastern regions of the bay. But, neither eelgrass (Zostera marina) leaf nitrogen (a proxy for integrated nitrogen loading), crustacean grazer biomass, epifaunal predator abundance, nor fish and crab abundance differed significantly among sites or regions. Overall, factors operating on different scales appear to drive primary producers, seagrass-associated faunal communities, and sediment properties in these important submerged vegetated habitats in lower Chesapeake Bay.  相似文献   

2.
Structural and functional characteristics of the Swartvlei estuary fish community are described. The detritivore group of fishes comprised 49% of the total catch biomass, zoobenthivores 25%, herbivores 18%, piscivores 6%, and epifauna/zooplanktivores 2%. The diets of 18 fish species, based on the analysis of 1,648 stomach contents, are presented. Selection by Swartvlei estuary fishes for zoobenthic invertebrates and aquatic macrophytes in different habitats was calculated using the linear index of selection. Results indicated a strong positive selection for epifaunal invertebrates and poor utilization of infauna and plants. Plant consumption by herbivorous fishes in the estuary centered around filamentous algae and diatoms growing onZostera capensis, rather than seagrass leaf material. The detrital base for both eelgrass- and sand-dominated areas in the Swartvlei estuary is emphasized, and most of the fish biomass was supported directly or indirectly by detritus. Large catches (mass per unit effort) in the macrophyte-free upper reaches site were attributed to the tidal input ofZostera leaves and associated algae to the area and its subsequent utilization by fishes through the detrital food chain.  相似文献   

3.
The complexity of habitat structure created by aquatic vegetation is an important factor determining the diversity and composition of soft-sediment coastal communities. The introduction of estuarine organisms, such as oysters or other forms of aquaculture, that compete with existing forms of habitat structure, such as seagrass, may affect the availability of important habitat refugia and foraging resources for mobile estuarine fish and decapods. Fish and invertebrate communities were compared between adjacent patches of native seagrass (Zostera marina), nonnative cultured oyster (Crassostrea gigas), and unvegetated mudflat within a northeastern Pacific estuary. The composition of epibenthic meiofauna and small macrofaunal organisms, including known prey of fish and decapods, was significantly related to habitat type. Densities of these epifauna were significantly higher in structured habitat compared to unstructured mudflat. Benthic invertebrate densities were highest in seagrass. Since oyster aquaculture may provide a structural substitute for seagrass being associated with increased density and altered composition of fish and decapod prey resources relative to mudflat, it was hypothesized that this habitat might also alter habitat preferences of foraging fish and decapods. The species composition of fish and decapods was more strongly related to location within the estuary than to habitat, and fish and decapod species composition responded on a larger landscape scale than invertebrate assemblages. Fish and decapod species richness and the size of ecologically and commercially important species, such as Dungeness crab (Cancer magister), English sole (Parophrys vetulus), or lingcod (Ophiodon elongatus), were not significantly related to habitat type.  相似文献   

4.
When compared with nearby unvergetated areas, seagrass meadows contain a dense and strikingly rich assemblage of vertebrates and invertebrates. Most recent literature has focused on evaluating the role of predation in structuring seagrass faunal communities; however, habitat complexity, abundance of food and sediment stability may also be important. This paper summarizes studies relating predator-prey relationships to different features of the seagrass system. This review suggests that the abundance of many species, both epifauna and infauna, is positively correlated with two distinct aspects of plant morphology: 1) the root-rhizome mat, and 2) the plant canopy. A scheme was developed that defines the conditions under which any particular species will be abundant or rare in a seagrass assemblage. This scheme is based on prey and predator characteristics (e.g., epifaunal vs. infaunal, tube-dweller vs. nontube dweller, burrowers vs. nonburrowers, and large vs. small as adult) and on characteristics of the seagrasses (e.g., leaf morphology, shoot density, shoot biomass, structural complexity of the meadow, and root-rhizome density and standing crop).  相似文献   

5.
Estuarine assemblages are exposed to multiple disturbances that overlap in time and space. Along the Atlantic Intracoastal Waterway (east coast, United States), two disturbances that frequently co-occur are the production of wake by boats and the disposal of sediment dredged from boat channels. Boat wake generally coarsens sediments by eroding finer particles while deposition of dredge spoil decreases mean grain size. If previously demonstrated effects of boat wake on infauna are due to coarsening of grain size, deposition of dredge spoil on wake affected sites may, through compensatory effects, prevent an effect of wake from being detected. Epifaunal assemblages associated with seagrass blades that are more likely to be structured by hydrodynamic forces than granulometry may instead be affected by boat wake irrespective of the previous deposition of fine materials. To test these hypotheses, in fauna and epifauna were sampled in patchy seagrass habitat at sites with and without boat wake that were affected by historic deposition of dredge spoil and at sites without wake that had not received dredge spoil. Sediment granulometry and infaunal assemblages differed between sites with and without dredge spoit but not between spoil affected sites differing in exposure to wake. Epifaunal assemblages differed between sites with and without wake irrespective of sediment granulometry. The effect of wake on epifauna was primarily due to lesser abundances of the gastropodBittiolum varium and the slipper limpet,Crepidula fornicata, at wake exposed sites. These results suggest that because of their opposing effects on sediment granulometry, boat-wake and sediment disposal may have compensatory effects on infaunal assemblages. The detection of an effect of wake on epifauna despite the absence of a sedimentological effect of the disturbance shows that ecological impacts do not necessarily mirror physical effects and should be considered separately when adopting strategies of management.  相似文献   

6.
We examined the effect of nutrients and grazers on Thalassia testudinum in Jobos Bay, Puerto Rico by fertilizing sediment and manipulating grazer abundances. Bottom-up effects were variable: Added nutrients did not increase seagrass aboveground biomass, but decreased belowground biomass—perhaps as a result of less biomass being allocated to belowground structures in response to greater nutrient supply in porewater. Experimental fencing of 1.5 × 1.5 m plots provided shelter that attracted large aggregations of fish, including seagrass herbivores. Seagrass biomass and shoot density decreased with increasing abundance of herbivorous fish, indicating a significant top-down effect. There were interactions between nutrient supply, provision of shelter, and grazing pressure. Fertilization enhanced seagrass %N; however, %N also increased in unfertilized plots that were fenced, most likely due to uptake of N excreted from the large numbers of fish associated with the fences. Only plots where shelter was provided and fertilizer was applied to sediments exhibited evidence of heavy grazing, reducing both seagrass cover and aboveground biomass. In the unfertilized fenced plots, signs of grazing were fewer despite large abundances of fish and enhanced nutritional quality of seagrass leaves. This suggests the possibility that high nutrient availability in sediments lowered concentrations of chemical defense compounds in the seagrass and that cues other than %N may have been involved in stimulating grazing. This study highlights the complexity of bottom-up and top-down interactions in seagrass systems and the important role of refuge availability in shaping the relative strengths of these controls.  相似文献   

7.
We examined the rhizosphere structure of 14 seagrass meadows (seven mixed, three Enhalus acoroides, two Zostera japonica, one Thalassia hemprichii, and one Halophila ovalis) in the Philippines and Vietnam and tested their effect on sediment redox potential by comparing the redox potential in vegetated vs unvegetated sediments. The effect of seagrass photosynthesis on sediment redox potential was tested in an E. acoroides meadow during a short-term (2-day) clipping experiment. In all the meadows, the centroidal depth (i.e., depth comprising 50%) of seagrass belowground biomass was within the top 15 cm sediment layer. Redox potentials in vegetated sediments tended to be higher than those in adjacent unvegetated ones; sediment redox potential anomaly ranged from −61 to 133 mV across the meadows. The centroidal depths of positive redox potential anomaly and seagrass root biomass were significantly correlated across the meadows investigated (type II regression analysis, slope = 0.90, lower confidence limit [CL] = 0.42 upper CL = 1.82, R 2 = 0.59, p < 0.01). Experimental removal of E. acoroides leaves resulted in a decrease in rhizosphere redox potential by 20 mV, further confirming the positive effect of seagrass roots and rhizomes on sediment redox potential and, thus, the general conditions for microbial processes in the coastal zone.  相似文献   

8.
Coastal lagoons are ubiquitous along coastlines worldwide. Here, we compare the abundance of epifauna, seagrass-associated macroinvertebrates, and small fish across a gradient of seagrass cover in shallow coastal lagoons of the northern Gulf of Mexico. Two of the lagoons had little or no seagrass cover (0–18.8 %), and four had high cover (83.8–97.5 %). All of the lagoons were partially covered with fringing marsh. We hypothesized that, due to habitat redundancy between seagrass beds and fringing marshes, seagrass-associated fish and macroinvertebrates would not be largely reduced despite the large differences in seagrass cover among the lagoons. Our results support this hypothesis. For most sampling dates, we did not find significant differences in fish and macroinvertebrate abundance among the lagoons and, when we did, several highly vegetated lagoons did not have larger abundances than sparsely vegetated lagoons. The extreme shallowness of the lagoons studied (<1 m) may also provide further protection from large predatory fishes in the absence of seagrasses. Our results also suggest that marsh detritus, by providing habitat for epifauna and helping maintain prey availability, may further temper reductions in seagrass-associated fishes and macroinvertebrates following seagrass decline. The results highlight the importance of marsh-bordered, shallow lagoons as habitat for small fish and macroinvertebrates regardless of seagrass cover. This study contributes to the characterization of habitat redundancy in coastal ecosystems and pinpoints the importance of considering all habitats in concert for the proper understanding and management of coastal ecosystems.  相似文献   

9.
An investigation of seagrass-epiphyte controlling factors was conducted within aThalassia testudinum meadow in Florida Bay from March 2000 to April 2001. Univariate and multivariate analyses were performed using water column nutrient concentrations, temperature, salinity, and turbidity, and gastropod grazer abundances, seagrass leaf area index, and leaf turnover rate data to explain the variation in total epiphyte standing stock, epiphyte chlorophylla, and epiphyte autotrophic index. Turbidity was positively correlated with total epiphyte standing stock and accounted for the most variation. Observations of adhered sediment onT. testudinum leaves and the combination, of increased total epiphyte standing stocks and low autotrophic indices observed in February and April 2001 suggest that the settling of resuspended sediments following turbidity events is one of the temporal mechanisms for increased epiphyte accumulation. Total epiphyte standing stock was also negatively correlated with the abundance of a robust gastropod grazer community dominated byTurbo castanea, Tegula fasciata, andModulus modulus. Distinct temporal size cohorts ofT. castanea andT. fasciata throughout the study period suggest recruitment in spring and an annual lifespan. Nutrient concentrations can also account for some of the temporal variation in total epiphyte standing stock, epiphyte chlorophylla, and autotrophic index. The low variation ofT. testudinum leaf turnover rates was unable to account for any of the variation in the epiphyte parameters.  相似文献   

10.
The capacity of seagrass canopies to directly retain sestonic particles was tested by quantifying the rate at which suspended fluorescent tracer particles were retained within a tropical Philippine seagrass meadow and by examining whether the test particles lost from the water column were later bound to seagrass leaves or inside epibionts. The particle loss rates in the presence of seagrass canopies were up to 4 times higher than those in unvegetated and plankton controls. The seagrass canopies trapped particles with a maximum rate of 0.73 (±0.24) h?1. As much as 5% of the particles trapped by the seagrass leaves were physically adhered to the leaf surfaces following rinsing. Particles were also observed to be ingested by protozoa (ciliates and amoeba-like organisms), residing on the surface of the leaves, and may be the dominant particle trapping mechanism by seagrass leaves. These processes should provide an efficient mechanism for the transfer of planktonic production to the benthos, adding to the high organic carbon input maintained by the high production of the seagrass themselves.  相似文献   

11.
The epifaunal and infaunal assemblages associated with Caulerpa taxifolia in the Port River/Barker Inlet estuary of Adelaide, South Australia were compared to those associated with the co-occurring seagrass Zostera muelleri. Both taxa contained an abundant and diverse fauna, but with substantial differences between them. In particular, ophiuroids (brittle stars) were abundant in Caulerpa, but almost absent from Zostera. Crustaceans, mostly amphipods, and annelids, mostly polychaetes, were abundant in both Caulerpa and Zostera, but the families present differed substantially. Taxa that dominated in Caulerpa include the amphipods: Amphithoidae, Corophiidae, and Talitridae; and the polychaetes: Cirratulidae, Nephtyidae, and Nereididae. Zostera was dominated by the polychaetes: Capitellidae; amphipods: Caprellidae; isopods: Sphaeromatidae; and Neballidae. Some taxa (arthropods, nemerteans, and echinoderms) had their peak abundance during summer, when Caulerpa biomass was highest, while others did not seem to respond to changes in Caulerpa biomass. Overall, epifauna were 4–9 times more abundant in Caulerpa than Zostera, while infauna were slightly more abundant in Zostera, indicating that at least in South Australia, Caulerpa provides a functional habitat for a diverse array of taxa.  相似文献   

12.
This study investigated macroinvertebrate community composition in seagrass beds at a range of spatial scales, with an emphasis on the transition between vegetated and unvegetated sediment. At four intertidal sites in three New Zealand estuaries (Whangamata, Wharekawa, and Whangapoua Harbours), a large continuous bed of seagrass (Zostera capricorni) was selected with adjacent unvegetated sediment. Macroinvertebrate community composition and biomass, as well as sediment characteristics, were determined at sampling locations 1 and 50 m inside seagrass beds, and 1, 10, and 50 m outside seagrass beds. Analysis of univariate measures of community composition (total abundance, number of species, and diversity) and total biomass indicated significant differences among sites and sampling locations, but contrary to many previous studies these measures were not higher inside than outside the seagrass beds. Multivariate analysis indicated that sites with high seagrass biomass supported a similar community composition. The remaining sampling locations were clustered by site, but there were also significant differences in community composition among sampling locations within a site. There were distinctive communities at the edge of seagrass beds at sites with high seagrass biomass, and evidence that the effects of seagrass beds may extend into the unvegetated sediment. At the low seagrass biomass site there was no evidence of any edge effects, although community composition differed inside and outside the bed. Differences in community composition were driven primarily by small changes in the relative abundance of the dominant taxa. At high seagrass biomass sites the absence of deep-burrowing polychaetes and low numbers of bivalves suggests that one possible mechanism underlying the observed variation in community composition was inhibition by the dense root-rhizome mat. The results of this study emphasize the need to consider the linkages between habitats in heterogeneous estuarine landscapes and how those linkages vary among sites, if the structure and functioning of macroinvertebrate communities in seagrass habitats are to be understood.  相似文献   

13.
Complex links between the top-down and bottom-up forces that structure communities can be disrupted by anthropogenic alterations of natural habitats. We used relative abundance and stable isotopes to examine changes in epifaunal food webs in seagrass (Thalassia testudinum) beds following 6 months of experimental nutrient addition at two sites in Florida Bay (USA) with different ambient fertility. At a eutrophic site, nutrient addition did not strongly affect food web structure, but at a nutrient-poor site, enrichment increased the abundances of crustacean epiphyte grazers, and the diets of these grazers became more varied. Benthic grazers did not change in abundance but shifted their diet away from green macroalgae + associated epiphytes and towards an opportunistic seagrass (Halodule wrightii) that occurred only in nutrient addition treatments. Benthic predators did not change in abundance, but their diets were more varied in enriched plots. Food chain length was short and unaffected by site or nutrient treatment, but increased food web complexity in enriched plots was suggested by increasingly mixed diets. Strong bottom-up modifications of food web structure in the nutrient-limited site and the limited top-down influences of grazers on seagrass epiphyte biomass suggest that, in this system, the bottom-up role of nutrient enrichment can have substantial impacts on community structure, trophic relationships, and, ultimately, the productivity values of the ecosystem.  相似文献   

14.
Our modeling objective was to better define the relationship between subtropical seagrass and potential water column and sediment stressors (light, organic and particle sedimentation, sediment nutrients, and the porewater sulfide system). The model was developed and optimized for sediments inThalassia testudinum seagrass beds of Lower Laguna Madre, Texas, U.S., and is composed of a plant submodel and a sediment diagenetic submodel. Simulations were developed for a natural stressor (harmful algal bloom,Aureoumbra lagunensis) and an anthropogenic, stressor (dredging event). The observed harmful algal bloom (HAB) was of limited duration and the simulations of that bloom showed no effect of the algal bloom on biomass trends but did suggest that sediment sulfides could inhibit growth if the bloom duration and intensity were greater. To examine this hypothesis we ran a simulation using data collected during a sustained 4-yr bloom in Upper Laguna Madre. Simulations suggested that light attenuation by the HAB could cause a small reduction inT. testudinum biomass, while input of organic matter from the bloom could promote development of a sediment geochemical environment toxic toT. testudinum leading to a major reduction in biomass. A 3-wk dredging event resulted in sedimentation of a layer of rich organic material and reduction of canopy light for a period of months. The simulations suggested that the seagrass could have recovered from the effects of temporary light reduction but residual effects of high sulfides in the sediments would make the region inhospitable for seagrasses for up to 2.5 yr. These modeling exercises illustrate that both natural and anthropogenic stressors can result in seagrass losses by radically altering the sedimentary geochemical environment.  相似文献   

15.
The Florida Bay ecosystem has changed substantially in the past decade, and alterations in the seagrass communities have been particularly conspicuous. In 1987 large areas ofThalassia testudinum (turtlegrass) began dying rapidly in western Florida Bay. Although the rate has slowed considerably, die-off continues in many parts of the bay. Since 1991, seagrasses in Florida Bay have been subjected to decreased light availability due to widespread, persistent microalgal blooms and resuspended sediments. In light of these recent impacts, we determined the current status of Florida Bay seagrass communities. During the summer of 1994, seagrass species composition, shoot density, shoot morphometrics, and standing crop were measured at 107 stations. Seagrasses had been quantified at these same stations 10 yr earlier by Zieman et al. (1989).T. testudinum was the most widespread and abundant seagrass species in Florida Bay in both 1984 and 1994, and turtlegrass distribution changed little over the decade. On a baywide basis,T. testudinum density and biomass declined significantly between surveys; mean short-shoot density ofT. testudinum dropped by 22% and standing crop by 28% over the decade.T. testudinum decline was not homogeneous throughout Florida Bay; largest reductions in shoot density and biomass were located principally in the central and western bay. Percent loss ofT. testudinum standing crop in western Florida Bay in 1994 was considerably greater at the stations with the highest levels of standing crop in 1984 (126–215 g dry wt m−2) than at the stations with lower levels of biomass. While turtlegrass distribution remained consistent over time, both the distribution and abundance of two other seagrasses,Halodule wrightii andSyringodium filiforme, declined substantially between 1984 and 1994. Baywide,H. wrightii shoot density and standing crop declined by 92%, andS. filiforme density and standing crop declined by 93% and 88%, respectively, between surveys. Patterns of seagrass loss in Florida Bay between 1984 and 1994 suggest die-off and chronic light reductions were the most likely causes for decline. If die-off and persistent water-column turbidity continue in Florida Bay, the long-term future of seagrasses in the bay is uncertain.  相似文献   

16.
We compared nekton use of prominent habitat types within a lagoonal system of the northeastern Gulf of Mexico (GoM). These habitat types were defined by combinations of structure (cover type) and location (distance from shore) as: Spartina edge (≤1 m from shore), Spartina (3 m from shore); Juncus edge (≤1 m from shore); seagrass located 3, 5, and 20 m from shore; and shallow non-vegetated bottom at various distances from shore. Although seagrass and Spartina edge sites differed little in environmental characteristics, the density and biomass of most abundant taxa, including pink shrimp (Farfantepenaeus duorarum), were higher in seagrass. Most species within seagrass and Spartina did not differ in abundance or biomass with distance from shore. Our study revealed a shift in peak habitat use in the northeastern GoM to seagrass beds from the pattern observed to the west where nekton is concentrated within shoreline emergent vegetation.  相似文献   

17.
Species of the macroalgae Caulerpa sp. are increasingly being observed in meadows of the endemic Mediterranean seagrass Posidonia oceanica, and in particular Caulerpa taxifolia, has been considered as an invasive species leading to seagrass decline. Studies have so far failed to reveal the underlying mechanisms of the success of the macroalgae, and here, we examine how biogeochemical changes of the environment associated to indigenous (Caulerpa prolifera) and non-indigenous (Caulerpa racemosa and C. taxifolia) species affect the habitat of P. oceanica. Two of the species (C. prolifera and C. racemosa) affect the sediment biogeochemical conditions by increasing organic matter pools, microbial activity, and sulfide pools of the sediments, and limited effects were found for C. taxifolia. Biomass of the macroalgae contributed to the extent of impacts, and high sulfide invasion into the seagrasses and regression of the meadow were pronounced at the location with the highest Caulerpa biomass. This suggests that Caulerpa invasion contributes to seagrass decline probably because Caulerpa thrives better than the seagrasses in the modified environment.  相似文献   

18.
A year-long analysis of the characteristics of the seagrassSyringodium filiforme and the associated dynamics of the nutrient pool in the sediment pore water was done to assess co-variation. Changes in seagrass growth rate and standing stock throughout the year were accompanied by seasonal changes in the nutrient pools. The link between plant production and morphometrics and the sediment nutrient pool was found to be predominantly physiological, with the plant balancing the ability to photosynthesize with the nutrients needed for maintaining production. Measurements of whole plant growth for this seagrass, rather than the more typical leaf growth measurements, show that the production of new shoots and rhizome elongation for these plants represents as substantial amount of growth that usually goes unmeasured. Further, these whole plant growth measures demonstrate the rapid lateral rhizome spread of this species, exceeding one meter per plant per year. The primary cause of seasonal variation in the yearly seagrass cycle was investigated. Correlation analysis supported the hypothesis that the major factor controlling seasonal variation in this seagrass was light. During the peak growing season, however, growth was not regulated by light but by nitrogen. Depletion of the sediment ammonium pool and reduction in pore water ammonium relative to adsorbed ammonium, as well as changes in N content of seagrass leaves, support our hypothesis of peak growing season nitrogen limitation. Our results forSyringodium filiforme in terrigenous sediments are in contrast to our recent findings of phosphorus limitation in this same species occurring in carbonate sediments.  相似文献   

19.

Four meadows of turtle grass (Thalassia testudinum Banks ex Konig) in Sarasota Bay, Florida were sampled on a bimonthly basis from June 1992 to July 1993 to determine spatial and temporal variation in short shoot density, biomass, productivity, and epiphyte loads. Concurrent with the seagrass sampling, quarterly water-quality monitoring was undertaken at ≥3 sites in the vicinity of each studied seagrass meadow. Three months after termination of the seagrass sampling effort, a biweekly water-quality monitoring program was instituted at two of the seagrass sampling sites. In addition, a nitrogen loading model was calibrated for the various watersheds influencing the seagrass meadows. Substantial spatial and temporal differences in turtle grass parameters but smaller spatial variation in water quality parameters are indicated by data from both the concurrent quarterly monitoring program and the biweekly monitoring program instituted after termination of the seagrass study. Turtle grass biomass and productivity were negatively correlated with watershed nitrogen loads, while water quality parameters did not clearly reflect differences in watershed nutrient inputs. We suggest that traditional water-quality monitoring programs can fail to detect the onset or continuance of nutrient-induced declines in seagrass health. Consequently, seagrass meadows should be monitored directly as a part of any effort to determine status and/or trends in the health of estuarine environments. *** DIRECT SUPPORT *** A01BY074 00029

  相似文献   

20.
Subsidence and erosion of intertidal salt marsh at Galveston Island State Park, Texas, created new areas of subtidal habitat that were colonized by seagrasses begining in 1999. We quantified and compared habitat characteristics and nekton densities in monospecific beds of stargrassHalophila engelmanni and shoalgrassHalodule wrightii as well as adjacent nonvegetated substrates. We collected 10 replicates per habitat type during April, July, October, and December 2001. Most habitat characteristics varied with season. Water temperature, salinity, and dissolved oxygen were similar among habitat types. Turbidity and depth were greatest inH. engelmanni beds and least inH. wrightii beds.H. engelmanni exhibited shorter leaves and higher shoot density and biomass core−1 thanH. wrightii. Densities of almost all dominant species of nekton (fishes and decapods) were seasonally variable, all were higher in seagrass habitats than in nonvegetated habitats, and most were higher in one seagrass species than the other. Naked gobyGobiosoma bosc, code gobyGobiosoma robustum, bigclaw snapping shrimpAlpheus heterochaelis, and blue crabCallinectes sapidus, were most abundant inH. engelmanni. Brown shrimpFarfantepenaeus aztecus, brackish grass shrimpPalaemonetes intermedius, and daggerblade grass shrimpPalaemonetes pugio were most abundant inH. wrightii. PinfishLagodon rhomboides and pink shrimFarfantepenaeus duorarum were equally abundant in either seagrass. Most dominant nekton varied in size by month, but only two (L. rhomboides andC. sapidus) exhibited habitat-related differences in size. Nekton densities in these new seagrass habitats equaled or exceeded densities associated with historical and current intertidal smooth cordgrassSpartina alterniflora marsh. Continued seagrass expansion and persistence should ensure ecosystem productivity in spite of habitat change.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号