Long-term abundance patterns of macroalgae in relation to environmental variables in the Tagus Estuary (Portugal)     

Abel Sousa-Dias  Ricardo A. Melo 《Estuarine, Coastal and Shelf Science》2008

Seasonal and inter-annual patterns of macroalgal abundance in a Tagus Estuary oyster reef are described. Macroalgal abundance was estimated as canopy percent cover by three permanent point intercept transects over a 7-year period. Four categories were defined, corresponding to bare substrate and three different macroalgal functional-form groups: (1) ULVA, foliose group, included Ulva spp.; (2) GRACIL, terete corticated macrophyte group, included only Gracilaria gracilis; and (3) FILAM, small (<10 cm) filamentous group, including eight species. A canonical correspondence analysis (CCA) showed that: (1) ULVA were associated with long and hot days, being usually dominant during spring and especially summer; (2) FILAM were associated with mild temperatures and relatively long days, abundant in spring but showed frequent peaks in summer; and (3) GRACIL were also favoured by spring season, although associated to lower temperature and less daylight hours than FILAM. GRACIL and FILAM were present throughout the year. On the contrary, ULVA were absent or with low cover during colder periods. A negative correlation between GRACIL and FILAM seems to indicate competition between the two categories. The applied models explained 23.3% of the temporal variance in category abundance. Rainfall negatively affected macroalgal cover, as indicated by the positive correlation between rainfall and bare substrate. Our conclusions are in agreement with previous studies that consider algae as excellent environmental integrators, even on a small scale, due to a strong link between the macroalgal communities and relevant environmental variables. It is also relevant that this study used open-access databases of environmental variables, which open up new possibilities for mining existing data resources in new ways. Due to large inter-annual variability, long-term studies are essential to understand population dynamics in estuarine phytobenthic communities.  相似文献   

The onset of fish colonization in a coastal defence structure (Chioggia,Northern Adriatic Sea)     

M. Pizzolon  E. Cenci  C. Mazzoldi 《Estuarine, Coastal and Shelf Science》2008

Coastal defence structures constitute the most extensive hard substrates of the Northwestern Adriatic Sea and are known to sustain rich benthic and nektonic communities. To appreciate the pattern of colonization, we studied the fish assemblage of a recently deployed breakwater. We compared observations from two years, the different sides (landward and seaward) of the barrier, and the two fringes, characterized by timing of work completion. The results indicate that colonization, still in process, follows different patterns among species. Benthic and necto-benthic species presented a striking increase in abundance and richness in the second year of colonization, while more mobile species did not evince any variation between years. Differences in mobility among species suggest that the latter group may have reached the breakwater from nearby artificial substrates, whereas the former colonized the new structure as recruits. In addition, fish assemblages differed between the two sides, likely due to variation in the environmental characteristics, and according to depth, reflecting species preferences.  相似文献   

Floating and fixed artificial habitats: Spatial and temporal patterns of benthic communities in a coral reef environment     

S. Perkol-Finkel  G. Zilman  I. Sella  T. Miloh  Y. Benayahu 《Estuarine, Coastal and Shelf Science》2008

While natural marine habitats with motion capabilities, e.g., kelps and seaweeds, have been studied alongside their associated fouling communities, little is known of the effect of motion on the communities of floating artificial habitats such as buoys, rafts, and pontoons, particularly in tropical systems. Hydrodynamic features greatly differ between floating and fixed artificial substrata, which in turn affect the structure of their associated communities. This study tested the hypothesis that floating and fixed artificial installations in a tropical reef system (Eilat, Red Sea) would support different benthic communities throughout space and time. Specifically, we examined differences in communities recruited onto settlement plates between floating and fixed installations deployed at three different sites, along a two-year monitoring period. The three sites exhibited distinct differences in species assemblages between the monitoring dates (6, 12, 18 and 24 months post deployment), mainly between the first and the last two dates. The average level of dissimilarity between floating and fixed installations increased over time at all sites. Over 50% of the dissimilarity between the floating and fixed installations resulted from five taxonomic groups i.e., bryozoans, bivalves, barnacles, sponges, including the amount of bare space on the settlement plates. The contribution of these groups to the dissimilarity changed both temporally within each site, and spatially among sites. The observed differences were related to the hydrodynamic characteristics of floating and fixed habitats, interacting with biotic features such as predation, successional processes and seasonality; and abiotic features including small-scale spatial changes, light, and position in the water column.  相似文献   

Climate change and coral reef bleaching: An ecological assessment of long-term impacts,recovery trends and future outlook   总被引：2，自引：0，他引：2  

Andrew C. Baker  Peter W. Glynn  Bernhard Riegl 《Estuarine, Coastal and Shelf Science》2008

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   

Skeletal linear extension rates of the foliose scleractinian coral Merulina ampliata (Ellis & Solander, 1786) in a turbid environment     

Angela Dikou 《Marine Ecology》2009,30(4):405-415

Skeletal linear extension rates of a foliaceous, IndoPacific, skiophilous, heterotrophic, scleractinian Merulina ampliata (Ellis & Solander 1786) were obtained along a sediment/nutrient load gradient at the southern islands of Singapore. Measurements were made during November 1999– November 2000 using the alizarin red‐S staining technique. Suspended particulate matter concentration (r²_adj = 0.76), turbidity (r²_adj = 0.59), the organic content of suspended sediments (r² = 0.50), and nitrite‐nitrate concentration (r²_adj = 0.50) were significant predictors of the skeletal linear extension rate of M. ampliata. Maximum linear extension growth rates of M. ampliata (mean ± SD: 1.43 ± 0.67–3.26 ± 0.59 cm·year^?1) were comparable to 15‐year‐old accounts at the same research sites, indicating adaptation to low‐light, high‐sediment waters.  相似文献   

基于底质类型变化监测的2005—2018年西沙永乐群岛珊瑚礁白化分析     

逄今朝  任广波  施祺  朱海天  胡亚斌  董娟  马毅 《海洋科学》2021,45(6):92-106

在海洋环境变化和人类活动的双重影响下,我国珊瑚礁白化现象日趋严重,珊瑚礁健康状况、珊瑚种群数量和丰富度呈逐年下降的趋势。本文基于2005-2007年QuickBird卫星影像、2011-2012年QuickBird/WorldView-2卫星影像和2016-2018年GF-1/2卫星影像等3期高分辨率遥感数据,以西沙永乐群岛羚羊礁、中建岛等14个岛礁为研究区（以下统称永乐群岛）,利用支持向量机（support vector machine,SVM）分类方法结合人机交互信息提取方法完成了3期永乐群岛的珊瑚礁底质类型分类,并通过珊瑚礁底质类型变化分析了永乐群岛珊瑚礁白化特征。主要结论包括：（1）提出了一种珊瑚礁白化程度分级的方法,将永乐群岛白化状况分为轻度、中度、重度和严重白化4个等级,通过分析发现在监测时段内14个岛礁中有13个发生了不同程度的白化,其中10个发生了重度白化（白化率20%以上）,1个严重白化（羚羊礁,白化率为33.36%）;（2）根据监测数据统计,上述珊瑚岛礁的白化主要是由珊瑚丛生区白化引起的,2005-2018年永乐群岛珊瑚丛生区白化面积占总的发生白化区域面积的70.55%;（3）14个岛礁中只有甘泉岛的活珊瑚覆盖在逐渐增加,活珊瑚覆盖面积由2006年5月10日的87.13 hm²增加到2018年3月7日的107.80 hm²。  相似文献   

绿色海堤的沉积地貌与生态系统动力学原理: 研究综述*     

高抒  贾建军  于谦 《热带海洋学报》2022,41(4):1-19

绿色海堤是传统结构工程与海岸生态系统共同组合而成的新型海堤, 用以应对未来海面上升、风暴加剧给低地海岸防护带来的挑战。需解决的问题主要有海岸生态系统消浪过程及生态系统在海堤体系中的配置方式。理论分析、现场观测、物模数模所获结果表明, 海岸生态系统确有显著的消浪功能: 1) 陆架泥区消浪, 其机制以再悬浮和浮泥运动为主, 底部摩擦为次; 2) 潮滩下部的粉砂细砂滩底部摩擦和推移质运动共同造成波能耗散, 而上部的泥滩则以再悬浮和悬沙输运为主; 3) 在盐沼、红树林、海草床等由植被构成的生态系统, 植物通过形态阻力、茎秆运动来阻滞水流、耗散波能, 其效能高于沉积物床面对波能的耗散; 4) 生物礁主要有珊瑚礁和牡蛎礁, 其消能作用主要通过床面摩擦和波浪破碎, 效能较高, 尤其是在风暴期间。生态系统如何成为海堤的有机组成部分, 尤其是侵蚀型海岸的生态位修复和绿色海堤整体设计, 还需进一步研究相关的科学问题: 与硬质工程结合的盐沼-牡蛎礁的适应性生物学; 未来环境变化条件下生态系统的稳定性; 绿色海堤生态系统空间配置及其与风暴事件的时间尺度匹配; 基于均衡剖面理论的海堤形态优化。  相似文献   

Biotic consequences of a shift in invertebrate ecosystem engineers: Invasion of New Zealand rocky shores by a zone‐forming ascidian          下载免费PDF全文

Andrew R. Davis  Katherine Walls  Andrew Jeffs 《Marine Ecology》2018,39(3)

The pervasive effects of invasive ecosystem engineers, that is those species that modify their environment, are well documented, but rarely have the broader impacts of one foundation invertebrate species being replaced by another been examined. In New Zealand, green‐lipped mussels, Perna canaliculus, commonly dominate wave‐exposed rocky shores. The recent appearance of an invasive ecosystem engineer, the ascidian Pyura doppelgangera, at the very northern tip of New Zealand now threatens to exclude these bivalves from this habitat. Here, we report major shifts in assemblages associated with the invader and chronicle its continued spread. We examined epibiota associated with clumps of mussels and clumps of Pyura from two rocky shore habitats—pools and emergent substrata at two locations. We detected some differences in species richness in biota associated with the two foundation species, but faunal abundance only differed between the locations. These minor changes were dwarfed by the shift in species composition within clumps of each foundation species. Molluscs, particularly gastropods, and crustaceans dominated the assemblage within mussels. In contrast, tubicolous polychaetes dominated the fauna associated with the ascidian. Sessile epifauna, notably barnacles and calcareous tube‐dwelling polychaetes, were common on mussels, but never encountered on the ascidian. Multivariate analysis revealed marked dissimilarity (>80%) between the characteristic mussel and ascidian faunas with virtually no overlap. This biotic shift overshadowed any differences between habitats and locations. The broader implications of these faunal shifts for local and regional patterns of biodiversity, as well as ecosystem function, remain unclear, but deserve further attention.  相似文献   

The effects of trophic interactions and spatial competition on algal community composition on Hawaiian coral reefs     

Mark J. A. Vermeij  Meghan L. Dailer  Sheila M. Walsh  Mary K. Donovan  Celia M. Smith 《Marine Ecology》2010,31(2):291-299

Much of coral reef ecology has focused on how human impacts change coral reefs to macroalgal reefs. However, macroalgae may not always be a good indicator of reef decline, especially on reefs with significant sea urchin populations, as found in Kenya and Hawaii. This study tests the effects of trophic interactions (i.e. herbivory by fishes and sea urchins) and spatial competition (between algae and coral) on algal community structure of reefs surrounding two Hawaiian Islands that vary in their level of human impacts. Reef‐building organisms (corals and crustose coralline algae) were less abundant and turf algae were more abundant on Maui as compared to Lanai, where human impacts are lower. In contrast to previous studies, we found no evidence that macroalgae increased with human impacts. Instead, low turf and macroalgal abundance were best explained by the interactive effects of coral cover and sea urchin abundance. Fishing sea urchin predators appeared to have cascading effects on the benthic community. The absence of sea urchin predators and high sea urchin densities correspond to a disproportionately high abundance of turf and crustose coralline algae. We propose that high turf algal abundance is a better indicator of reef decline in Hawaii than high macroalgal abundance because turf abundance was highest on reefs with low coral cover and few fish. The results of this study emphasize that understanding changes in community composition are context‐dependent and that not all degraded reefs look the same.  相似文献   

Biological structures as a source of habitat heterogeneity and biodiversity on the deep ocean margins   总被引：1，自引：0，他引：1  

Lene Buhl-Mortensen  Ann Vanreusel  rew J. Gooday  Lisa A. Levin  Imants G. Priede  Pål Buhl-Mortensen  Hendrik Gheerardyn  Nicola J. King  & Maarten Raes 《Marine Ecology》2010,31(1):21-50

Biological structures exert a major influence on species diversity at both local and regional scales on deep continental margins. Some organisms use other species as substrates for attachment, shelter, feeding or parasitism, but there may also be mutual benefits from the association. Here, we highlight the structural attributes and biotic effects of the habitats that corals, sea pens, sponges and xenophyophores offer other organisms. The environmental setting of the biological structures influences their species composition. The importance of benthic species as substrates seems to increase with depth as the complexity of the surrounding geological substrate and food supply decline. There are marked differences in the degree of mutualistic relationships between habitat-forming taxa. This is especially evident for scleractinian corals, which have high numbers of facultative associates (commensals) and few obligate associates (mutualists), and gorgonians, with their few commensals and many obligate associates. Size, flexibility and architectural complexity of the habitat-forming organism are positively related to species diversity for both sessile and mobile species. This is mainly evident for commensal species sharing a facultative relationship with their host. Habitat complexity is enhanced by the architecture of biological structures, as well as by biological interactions. Colony morphology has a great influence on feeding efficiency for suspension feeders. Suspension feeding, habitat-forming organisms modify the environment to optimize their food uptake. This environmental advantage is also passed on to associated filter-feeding species. These effects are poorly understood but represent key points for understanding ecosystems and biodiversity on continental margins. In this paper we explore the contributions of organisms and the biotic structures they create (rather than physical modifications) to habitat heterogeneity and diversity on the deep continental margins.  相似文献