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1.
威海近岸人工鱼礁布设对生物资源恢复效果   总被引：4，自引：0，他引：4  
为了解人工鱼礁投放对区域内海洋生物资源恢复效果,于2013年3月至2014年1月在北黄海近岸人工鱼礁投放区进行调查。结果显示,该海区发现浮游动物53种,其中优势种为浮游桡足类。夏秋季底栖生物幼体成为季节性优势种。游泳动物共发现14种,主要为常见的礁区鱼类。底栖动物共12种,其中棘皮动物海燕为绝对优势种,为近岸养殖生物的主要敌害生物,主要的底栖资源优势种为虾蟹类与软体动物。投礁区的浮游动物与游泳动物物种数明显多于未投礁区,表明人工投礁有助于生物群落的恢复,提高生物多样性,改善区域生态系统。但该海域大型底栖藻类较少,还应进一步对大型底栖藻类增殖以提高海域初级生产。  相似文献   

2.
Coral reef fish are an important source of food security and income for human coastal populations. They also underpin ecosystem processes vital for the future ability of coral reefs to generate ecological goods and services. Identifying socio-economic drivers behind the exploitation of fish that uphold these key ecosystem processes and the scales at which they operate is therefore critical for successful management. This study addresses this issue by examining the reef-associated fish value chain in Zanzibar, and how it links to functional groups of fish and maturity stage of fish within these groups. Semi-structured interviews with 188 respondents (fishers, traders and hotel staff) involved in the fisheries and trade with reef-associated fish in Zanzibar and participatory observations were used. The trade with reef fish in Zanzibar is a complex structure involving many different agents and this study shows that these different agents exhibit differential “preferences” regarding fish functional groups and/or maturity stages within these groups. Consequently, both high and low trophic species, as well as small and large fishes are fished and sold, which leaves no refuge for the fish assemblage to escape fishing. When other market agents than fishers have so much influence and there are few alternative income generating activities, it is not possible to put all burden on fishers. Management measures that extend down the value chain to include all market agents as well as their links to ecosystem processes are thus likely to be needed to reach the target of sustainable fisheries.  相似文献   

3.
Effective conservation requires knowledge of the effects of habitat on distribution and abundance of organisms. Although the structure of coral reef fish assemblages is strongly correlated with attributes of reef structure, data relating reef types to fish assemblages are scarce. In this study we describe the influence of gross habitat characteristics and seasonality on coral reef fish assemblages of fringing and patch reefs in Kenya. Results showed that total fish abundance was not significantly different between the reefs; however, the fringing reef had higher species diversity during both the northeast (42 spp.) and southeast (36 spp.) monsoon seasons when compared to the patch reef. The more fished species (e.g. Siganus sutor and Lethrinus mahsena) were more abundant on the patch reef in both seasons. Statistical analysis indicated common species between the reefs were more abundant on the fringing reef. Seasons affected abundance of the more vagile species (S. sutor), whereas the reef‐attached sky emperor, L. mahsena was affected more by reef type than by seasons. No significant interaction effects of habitat and seasons were found, indicating independence of habitat and environmental variability in affecting fish assemblages on the reefs. Smaller sized fish dominated the fringing reef more than the patch reef, whereas the skewness index (Sk) indicated a normal‐sized frequency distribution on the patch reef. Trophic structure of the fishes varied more within than between reefs, whereas fish assemblage structure was affected more by seasons on the fringing reef. These results suggest that conservation measures such as marine protected area (MPA) design and setting should consider effects of reef morphology and environmental variability on coral‐reef fish assemblage structure.  相似文献   

4.
In consideration of the rapid degradation of coral reef ecosystems, the establishment of models is helpful to comprehend the degradation mechanism of coral reef ecosystems and predict the development process of coral reef communities. According to the characteristics of complex ecosystem of tropical coral reefs in China, the coral reef functional group is the core level variable; combined with the multiple feedback effects of coral reef functional groups and environmental changes, the study presents a coral reef ecosystem dynamics model with hermatypic corals as the core. Based on the simulation of the assumed initial value and the internal feedback of the system, the results show that in the basic simulation(relative health conditions), the coverage area of live corals and coral reefs generally decreased first and then increased, and increased by 4.67% and 6.38% between2010 and 2050, respectively. Based on the calibration model and the current situation of the studied area, the multi-factor disturbance effects of coral reef communities were simulated and explored by setting up three scenarios involving fishing policy, terrestrial deposition, and inorganic nitrogen emissions. Among them, in the single factor disturbance, the fishing policy exerts the most direct impact on the community decline; and the succession phenomenon is obvious; the terrestrial sedimentation has a faster and more integrated effect on the community decline; the effect of inorganic nitrogen emission on the community decline is relatively slow. In the double/multi-factor disturbance, the superimposed disturbance will aggravate the multi-source feedback effect of the coral reef communities development, accelerate the community decay rate, and make its development trajectory more complicated and diverse. This method provides a scientific and feasible method for simulating the damage of long-term coral reef community and exploring the development law and adaptive management of coral reef ecosystems. In the future, it can be further studied in the ecological restoration process and decisionmaking direction of coral reefs.  相似文献   

5.
There is currently a critical knowledge gap in how eutrophication and climate variables separately and interactively impact the dynamics of marine ecosystems. Based on long-term monitoring data we quantified the separate and combined impacts of nutrient loading, temperature, salinity, and wind conditions on zooplankton, zoobenthos and fish inhabiting a brackish water ecosystem in the Gulf of Riga. Changes in zoobenthos communities and herring stock were largely explained by climate variables. Zooplankton species were related to both eutrophication and climate variables, and models combining all environmental variables explained additional variation in zooplankton data compared to the separate models of climate and eutrophication. This suggests that zoobenthos communities and herring stock are largely driven by weather conditions, whereas the combined effect of weather and nutrient loads are likely the cause for dynamic zooplankton communities in the Gulf of Riga.  相似文献   

6.
于2018年8月对海南东、南海域展开断面调查研究,共获取了18个浮游动物样品,分析了浮游动物的种群分布和群落结构变化,旨在了解不同区域珊瑚礁生态系统的结构与功能。结果表明:海南东、南沿岸共鉴定浮游动物43属62种,浮游幼体23类,分为河口类群、暖水沿岸类群和暖水广布类群共三个生态类群,浮游动物种群组成以桡足类占优势,优势种以亚强次真哲水蚤(Subeucalanus subcrassus)、肥胖箭虫(Sagittaenflata)、异体住囊虫(Oikopleuradioica)、长尾类幼体(Macruralarva)、鱼卵(Fisheggs)、双生水母(Diphyeschamissonis)等种类组成。浮游动物个体丰度、物种丰富度和多样性指数等参数均存在区域性差异,整体呈现为三亚琼海文昌,湿重生物量则为琼海三亚文昌。总体而言,三亚珊瑚礁生态系统的健康状况整体优于文昌和琼海地区,浮游动物种类丰富度与多样性整体呈较高水平。  相似文献   

7.
Studies on the early life history of fish in New Zealand started during the 1950s off the Northland coast. Since then taxonomy, seasonality in abundance, and vertical and horizontal distribution patterns have been described as well as aspects at the level of individuals, such as age, growth, and condition. I discuss the findings and issues that have developed from these studies and illustrate three undescribed presettlement reef fish. Results indicate that different taxonomic groups typically have different vertical and horizontal distribution patterns as well as different temporal patterns of abundance. This implies that general models of how “larval fish” behave are unrealistic. As a result, the importance of physical and biological processes that may influence the distribution and survival of ichthyoplankton will vary among categories of fish (such as pelagic and reef fish) and taxonomic groups within these. Based on knowledge of the distribution pattern of some species, there is considerable scope for focusing future research on specific groups offish in terms of ontogenetic changes in morphology, sensory abilities, growth, diet, condition, interrelationships with other plankters, and, in the case of reef fish, onshore transport.  相似文献   

8.
The Huizache–Caimanero coastal lagoon complex on the Pacific coast of Mexico supports an important shrimp fishery and is one of the most productive systems in catch per unit area of this resource. Four other less important fish groups are also exploited. In this study, we integrated the available information of the system into a mass-balance trophic model to describe the ecosystem structure and flows of energy using the E approach. The model includes 26 functional groups consisting of 15 fish groups, seven invertebrate groups, macrophytes, phytoplankton, and a detritus group. The resulting model was consistent as indicated by the output parameters. According to the overall pedigree index (0.75), which measures the quality of the input data on a scale from 0 to 1, it is a high quality model. Results indicate that zooplankton, microcrustaceans, and polychaetes are the principal link between trophic level (TL) one (primary producers and detritus) and consumers of higher TLs. Most production from macrophytes flows to detritus, and phytoplankton production is incorporated into the food web by zooplankton. Half of the flow from TL one to the next level come from detritus, which is an important energy source not only for several groups in the ecosystem but also for fisheries, as shown by mixed trophic impacts. The Huizache–Caimanero complex has the typical structure of tropical coastal lagoons and estuaries. The TL of consumers ranges from 2.0 to 3.6 because most groups are composed of juveniles, which use the lagoons as a nursery or protection area. Most energy flows were found in the lower part of the trophic web.  相似文献   

9.
Benthic structure of coral reefs determines the availability of refuges and food sources. Therefore, structural changes caused by natural and anthropogenic disturbances can have negative impacts on reef‐associated communities. During the 1990s, coral reefs from Bahía Culebra were considered among the most diverse ecosystems along the Pacific coast of Costa Rica; however, recently they have undergone severe deterioration as consequence of chronic stressors such as El Niño‐Southern Oscillation and harmful algal blooms. Reef fish populations in this area have also been intensely exploited. This study compared reef fish assemblages during two periods (1995–1996 and 2014–2016), to determine whether they have experienced changes as a result of natural and anthropogenic disturbances. For both periods, benthic composition and reef fish abundance were recorded using underwater visual censuses. Live coral cover (LCC) decreased from 43.09 ± 18.65% in 1995–1996 to 1.25 ± 2.42% in 2014–2016 (U = 36, p < 0.05). Macroalgal cover (%) in 2014–2016 was sixfold higher than mean values reported for the Eastern Tropical Pacific region. Mean (±SD) fish species richness in 1995–1996 (36.67 ± 14.20) was higher than in 2014–2016 (23.00 ± 9.14; U = 20, p < 0.05). Over 40% of reef fish orders observed in 1995–1996 were not detected in the 2014–2016 surveys, including large‐bodied predators. Reduction in abundance of fish predators such as sharks, grunts, and snappers is likely attributed to changes in habitat structure. Herbivorous such as parrotfishes and pufferfishes increased their abundance at sites with low LCC, probably in response to predators decline and increased algal cover. These findings revealed significant degradation and drastic loss of structural complexity in coral reefs from Bahía Culebra, which now are dominated by macroalgae. The large reduction in structural complexity of coral reefs has resulted in the loss of diversity and key ecological roles (e.g., predation and herbivory), thus potentially reducing the resilience of the entire ecosystem.  相似文献   

10.
基于Ecopath模型的七连屿礁栖性生物的生态承载力分析   总被引：1，自引：0，他引：1  
生态承载力评估是开展生物资源增殖放流, 维持珊瑚礁生态系统健康的基础和前提。本文基于2019年渔业资源和生态环境的综合调查数据, 构建了七连屿珊瑚礁海域生态系统的生态通道(Ecopath)模型, 分析和探讨了相关功能组增殖放流的生态承载力。结果显示, 七连屿珊瑚礁海域生态系统各功能群营养级范围为1.00~3.81; 生态系统的总能量转化效率为13.45%; 生态系统以牧食食物链占据主导地位, 直接来源于初级生产者的能流占比为57%。系统总初级生产量/总呼吸量为2.54; 总初级生产量/总生物量为19.07; 系统连接指数和系统杂食性指数分别为0.36和0.22, 表明当前七连屿珊瑚礁海域生态系统的成熟度和稳定性偏低, 系统对于外界的干扰抵抗能力较弱。在未改变七连屿珊瑚礁生态系统结构和功能的前提下, 各功能组中珊瑚、双壳类和植食性鱼类的生态承载力分别为25.09~53.77t•km-2、2.55~39.95t•km-2和4.89~17.94t•km-2, 因此仍具有较大的增殖空间。珊瑚礁鱼类群落的最大生态承载力同珊瑚礁无脊椎动物群落的增殖密切相关, 在未来的珊瑚礁渔业管理中应从生态系统整体结构的角度综合考虑增殖放流的方法设计。  相似文献   

11.
The present work analyses the spatial and temporal fluctuations of fish communities on Réunion coral reef flats on three different reefs, each comprising three geomorphological zones, over eight seasons within a 6-year period. These three reefs are subjected to different environmental conditions and displayed various percentages of live coral cover. Our objectives were not only to describe the spatio-temporal patterns, but also to organize the factors involved in variation hierarchically, and to quantify the degree of community structuring that could be monitored over various spatial and temporal scales. We also focus on fish guilds to link the spatio-temporal patterns not only to species but also to the roles fish are playing (mainly involving trophic activity). We found that spatial attributes strongly determined fish distribution, with intra-reefal zones (back-reef, inner reef flat and outer reef flat) playing a much more important role than the different reefs. This suggests that the percentage of live coral cover of a given reef was less significant than its morpho-structural organization to explain fish distribution. Seasons had only a weak role in fish distribution, although fish communities were significantly more homogeneous in winter than in summer, possibly due to the arrival of numerous juveniles belonging to various species during summer settlement events. We also identified a marked temporal persistence of the spatial patterns found over the course of the study. This is discussed in relation to the current trend of increased surface seawater temperatures involved in the possible future increase in number/intensity of ENSO events. We consider the average squared Euclidian distance as a candidate for monitoring tools to quantify future changes in fish community structuring.  相似文献   

12.
Conflict surrounding commercial fisheries is a common phenomenon when diverse stakeholders are involved. Harvesting reef fish for the global ornamental fish trade has provoked conflict since the late 1970s in the State of Hawaii. Two decades later the state of Hawaii established a network of marine protected areas (MPAs) on the west coast of the island of Hawaii (“West Hawaii”) to protect and enhance the fish resources and alleviate conflict between stakeholders, principally between commercial dive tour operators and aquarium fishers. The perceptions held by these stakeholders on West Hawaii and Maui were evaluated to understand how MPAs influenced conflict dimensions, as the former location had a well-established MPA network designed to alleviate conflict, while the latter did not. This was accomplished by analyzing the following questions: (1) perceptions about the effectiveness of MPAs to alleviate conflict and enhance reef fish; (2) perceived group encounters and threats to coral reefs; (3) willingness to encourage fishing; and (4) value orientations toward the aquarium fish trade. The results indicate the MPAs in West Hawaii were moderately effective for alleviating conflict, encounters between stakeholders occurred on both islands, dive operators strongly opposed commercial fishing and perceived aquarium fishing as a serious threat to the coral reef ecosystem, and polarized value orientations toward the aquarium fish trade confirms pervasive social values conflict. The conflict between these groups was also asymmetrical. MPAs are inadequate for resolving long term conflict between groups who hold highly dissimilar value orientations toward the use of marine resources. Future marine spatial planning and MPA setting processes should include stakeholder value and conflict assessments to avoid and manage tensions between competing user groups.  相似文献   

13.
莱州湾游泳动物群落结构研究   总被引：1，自引：0，他引：1  
本文根据2010和2011年春季（5月）、夏季（8月）、秋季（10月）和冬季（12月）进行的8航次调查数据，研究了莱州湾游泳动物群落格局及其与环境因子关系。结果显示，调查共捕获游泳动物85种，2011年生物量略高于2010年；生物量季节间差别较大，各季节生物量排序为夏季、秋季、冬季和春季；不同年间相同季节生物量差异多不显著（秋季除外）；除2010年春季外，其余季节均为鱼类生物量最高，甲壳类次之，头足类最低；从全年调查平均值来看，莱州湾西侧游泳动物生物量（60.2 kg/h）明显高于东侧（33.4 kg/h）。根据8航次31个主要种类生物量聚类分析，莱州湾20调查站位可划分为4组：组I由位于调查海域东南的3个站位组成，组II由位于调查海域东部及中部的8个站位组成，组III由调查海域西北部（黄河口南侧）的3个站位组成，组IV由西部6个站位组成。组I浮游植物丰度、浮游动物生物量、游泳动物生物量和游泳动物多样性指数在各组中均最低，而底栖动物生物量最高；组III和组IV的浮游植物丰度、浮游动物生物量以及游泳动物生物量高于组I和组II。ANOSIM分析表明，各聚类组间群落结构虽有不同，但差异并不显著。DCCA分析表明，温度、盐度、底栖动物生物量以及浮游植物丰度是影响游泳动物群落的重要因子。研究表明，目前莱州湾游泳动物群落总生物量处于较低水平，特别是春季生物量下降尤为严重；生物量的季节分布发生了较大的改变，春季生物量极低，夏季生物量相对较高；底层鱼类比例下降的趋势有所逆转，头足类比例明显增加。莱州湾游泳动物群落格局异质性较低，可能与莱州湾生境异质性低以及人类剧烈干扰密切相关。  相似文献   

14.
Since the early 1980s, episodes of coral reef bleaching and mortality, due primarily to climate-induced ocean warming, have occurred almost annually in one or more of the world's tropical or subtropical seas. Bleaching is episodic, with the most severe events typically accompanying coupled ocean–atmosphere phenomena, such as the El Niño-Southern Oscillation (ENSO), which result in sustained regional elevations of ocean temperature. Using this extended dataset (25+ years), we review the short- and long-term ecological impacts of coral bleaching on reef ecosystems, and quantitatively synthesize recovery data worldwide. Bleaching episodes have resulted in catastrophic loss of coral cover in some locations, and have changed coral community structure in many others, with a potentially critical influence on the maintenance of biodiversity in the marine tropics. Bleaching has also set the stage for other declines in reef health, such as increases in coral diseases, the breakdown of reef framework by bioeroders, and the loss of critical habitat for associated reef fishes and other biota. Secondary ecological effects, such as the concentration of predators on remnant surviving coral populations, have also accelerated the pace of decline in some areas. Although bleaching severity and recovery have been variable across all spatial scales, some reefs have experienced relatively rapid recovery from severe bleaching impacts. There has been a significant overall recovery of coral cover in the Indian Ocean, where many reefs were devastated by a single large bleaching event in 1998. In contrast, coral cover on western Atlantic reefs has generally continued to decline in response to multiple smaller bleaching events and a diverse set of chronic secondary stressors. No clear trends are apparent in the eastern Pacific, the central-southern-western Pacific or the Arabian Gulf, where some reefs are recovering and others are not. The majority of survivors and new recruits on regenerating and recovering coral reefs have originated from broadcast spawning taxa with a potential for asexual growth, relatively long distance dispersal, successful settlement, rapid growth and a capacity for framework construction. Whether or not affected reefs can continue to function as before will depend on: (1) how much coral cover is lost, and which species are locally extirpated; (2) the ability of remnant and recovering coral communities to adapt or acclimatize to higher temperatures and other climatic factors such as reductions in aragonite saturation state; (3) the changing balance between reef accumulation and bioerosion; and (4) our ability to maintain ecosystem resilience by restoring healthy levels of herbivory, macroalgal cover, and coral recruitment. Bleaching disturbances are likely to become a chronic stress in many reef areas in the coming decades, and coral communities, if they cannot recover quickly enough, are likely to be reduced to their most hardy or adaptable constituents. Some degraded reefs may already be approaching this ecological asymptote, although to date there have not been any global extinctions of individual coral species as a result of bleaching events. Since human populations inhabiting tropical coastal areas derive great value from coral reefs, the degradation of these ecosystems as a result of coral bleaching and its associated impacts is of considerable societal, as well as biological concern. Coral reef conservation strategies now recognize climate change as a principal threat, and are engaged in efforts to allocate conservation activity according to geographic-, taxonomic-, and habitat-specific priorities to maximize coral reef survival. Efforts to forecast and monitor bleaching, involving both remote sensed observations and coupled ocean–atmosphere climate models, are also underway. In addition to these efforts, attempts to minimize and mitigate bleaching impacts on reefs are immediately required. If significant reductions in greenhouse gas emissions can be achieved within the next two to three decades, maximizing coral survivorship during this time may be critical to ensuring healthy reefs can recover in the long term.  相似文献   

15.
塔形马蹄螺(Tectuspyramis)是一种暖水性较强的海洋贝类,也是一种重要的礁栖生物,研究其自然环境中的食物组成对于认识其生态功能具有重要意义,但由于缺少直接的食物组成信息,对其食性和生态功能定位尚不明确。本研究于2017年春季在南沙珊瑚礁区采集了塔形马蹄螺样品,以18S rDNA可变区(V4)序列为靶标,用高通量测序技术分析了其现场食物组成。共测得41个OTU,分属11个门类,包括节肢动物门(Arthropoda)、子囊菌门(Ascomycota)、担子菌门(Basidiomycota)、丝足虫门(Cercozoa)、刺胞动物门(Cnidaria)、Stramenopiles(不等鞭毛类)、网粘菌门(Labyrinthulomycota)、软体动物门(Mollusca)、多孔动物门(Porifera)、甲藻门(Pyrrophyta)、捕虫霉亚门(Zoopagomycota)。与以往研究不同的是,本研究发现塔形马蹄螺消化道中存在大量沉积物碎屑,其中有孔虫、真菌、后生动物是最重要的类群,占食物序列组成的99.76%,它们主要存在于海洋沉积物、有机碎屑和礁石表生藻类基质(Epilithic algal matrix, EAM)中。研究结果揭示了塔形马蹄螺的食物主要来源于EAM中的小型生物和碎屑以及珊瑚礁石上的有害生物,推测塔形马蹄螺属于沉积物碎屑食性生物,可能在清除珊瑚表面藻类基质、促进珊瑚幼体附着过程中发挥一定的作用,对于维护珊瑚生态系统的健康和稳定具有积极意义。  相似文献   

16.
Benthic communities colonizing two different typologies of artificial structures, Tecnoreef® pyramids (PY), and plinth modules (PL), differing for material and shape, were investigated for three years after their deployment on a soft bottom offshore Pedaso (Western Adriatic Sea). The aims were to describe the colonization patterns of benthic assemblages on the two artificial modules, to highlight possible differences between them and to detect the effectiveness of the artificial reef on the ecosystem functioning.The composition of the benthic communities settled on the two types of artificial substrates was different especially just after the reef deployment. Abundance and species richness were higher on PL in the first two years, while an explosion of individuals characterized PY in the third year. This suggested a delay of about one year in the colonization processes on PY likely due to the material and shape. The community settled of the artificial structures was dominated by hard-substrate species which are commonly absent in the natural environment. The occurrence of these organisms enriched the local soft-bottom communities and contributed to habitat diversification. This, together with the importance of these species in the diet of a few reef-dwelling fish, confirms the trophic role and the ecological importance of artificial reefs in areas characterized by soft seabed.  相似文献   

17.
Understanding the connectivity of fish among different typical habitats is important for conducting ecosystembased management, particularly when designing marine protected areas(MPA) or setting MPA networks. To clarify of connectivity among mangrove, seagrass beds, and coral reef habitats in Wenchang, Hainan Province,China, the fish community structure was studied in wet and dry seasons of 2018. Gill nets were placed across the three habitat types, and the number of species, individuals, and body size of individual fish were recorded. In total, 3 815 individuals belonging to 154 species of 57 families were collected. The highest number of individuals and species was documented in mangroves(117 species, 2 623 individuals), followed by coral reefs(61 species,438 individuals) and seagrass beds(46 species, 754 individuals). The similarity tests revealed highly significant differences among the three habitats. Approximately 23.4% species used two habitats and 11.0% species used three habitats. A significant difference(p0.05) in habitat use among eight species(Mugil cephalus, Gerres oblongus, Siganus fuscescens, Terapon jarbua, Sillago maculata, Upeneus tragula, Lutjanus russellii, and Monacanthus chinensis) was detected, with a clear ontogenetic shift in habitat use from mangrove or seagrass beds to coral reefs. The similarity indices suggested that fish assemblages can be divided into three large groups namely coral, seagrass, and mangrove habitat types. This study demonstrated that connectivity exists between mangrove–seagrass–coral reef continuum in Wenchang area; therefore, we recommend that fish connectivity should be considered when designing MPAs or MPA network where possible.  相似文献   

18.
为查明朱旺港人工礁区游泳动物的群落结构特征及其季节变化,于2010年5～11月和2011年3月对该海域人工礁区和自然对照区进行逐月调查.结果表明,人工礁区游泳动物种类比对照区丰富(1.42倍);并且人工礁区的Margalef种类丰富度指数、Shannon-Wiener多样性指数、Pielou均匀度指数均高于对照区.人工礁区的CPUE也明显高于对照区,人工礁区的Al区(建于2008年)和A2区(建于2009年)分别是自然对照区CA区的1.43和1.55倍,其中经济种类日本蟳的CPUE分别达到2.69和2.97倍.初步体现人工鱼礁投放后的集鱼效果,且礁区游泳动物的群落结构有明显改善.  相似文献   

19.
Multibeam imagery of siliceous sponge reefs (Hexactinellida, Hexactinosida) reveals the setting, form, and organization of five reef complexes on the western Canadian continental shelf. The reefs are built by framework skeleton sponges which trap clay-rich sediments resulting in a distinctive pattern of low intensity backscatter from the reefs that colonize more reflective glacial sediments of higher backscatter intensity. Bathymetry and backscatter maps show the distribution and form of reefs in two large complexes in the Queen Charlotte Basin (QCB) covering hundreds of km2, and three smaller reef complexes in the Georgia Basin (GB). Ridges up to 7 km long and 21 m in height, together with diversely shaped, coalescing bioherms and biostromes form the principal reef shape in the QCB whereas chains of wave-form, streamlined mounds up to 14 m in height have developed in the GB. Reef initiation is dependent on the distribution of high backscatter-intensity relict glacial surfaces, and the variation in reef complex morphology is probably the result of tidally driven, near seabed currents.  相似文献   

20.
By the consumption of algae, parrotfishes open space for young coral settlement and growth, thus playing a central role on the maintenance of coral reefs. However, juvenile parrotfish ecology is often overlooked due to the difficulty discerning species during this phase. Herein, we present the first attempt to investigate changes in habitat use and diet that happen to juveniles of the Redeye parrotfish Sparisoma axillare, focusing on four zones within an algal‐dominated reef: the macroalgal beds, back reef, reef flat, and fore reef. Smaller S. axillare juveniles (<5 cm) preferred to inhabit the macroalgal beds and the reef flat, whereas juveniles larger than 5 cm were more abundant in the back and fore reefs due to distinct post‐settlement habitat conditions. Aggressive interactions with the territorial damselfish Stegastes fuscus were the primary driving factor of juvenile distribution and feeding rates. Attack rates increased with juvenile size and the lowest bite rates were observed in zones with higher densities of territorial damselfish. In previous studies, the persistence of parrotfish recruits in habitats dominated by damselfish was reduced, but newly settled parrotfish occurred more densely within the damselfish domain by behaving as a cryptic reef fish. As these juveniles grew, their bite rates increased, a change associated with a shift from cryptic to roving behavior. Feeding preferences were determined by substrate cover, where juveniles fed on available food sources in each habitat. Juveniles relied on jointed calcareous algae in habitats dominated by these algae, a pattern not observed for thick leathery algae. Filamentous algae were the preferred food for smaller fish; for individuals greater than 10 cm, a higher ingestion of sand was observed. Most studies evaluating the functional role of parrotfish do not consider species feeding preferences. However, the potential for a species to turn an impacted reef back to a coral‐dominated phase is influenced by their food selection, which is dependent on the algal species composition.  相似文献   

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