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1.
Canopy-forming algae occur across of range of energy environments (i.e., wave sheltered to exposed coasts) where disturbances are frequent (i.e., gap formation) and benthic patterns largely reflect variation in post-disturbance processes. Disturbances vary in extent (area affected) and intensity (degree of damage), and this may affect recolonisation at local scales. On an open oceanic coast, we tested whether habitat structure (patches of canopy algae) differed between heavy and relatively lighter wave exposure (sheltered vs. exposed sides of islands), and whether wave exposure affected the response of prominent habitat-formers to varying disturbance regimes (different sizes of partial and complete canopy removal). Observations of naturally occurring patterns showed sheltered coasts to be characterised by small patches of fucoids, whereas exposed coasts were characterised by large patches of kelp. Canopy-gaps were larger at exposed than sheltered coasts, and mixed canopies constituted > 24% of the subtidal rocky habitat independently of wave exposure. Experimental disturbances showed the local density of kelps to affect recovery through greater recruitment to partial clearings (80% canopy removal). Fucalean algae, on the other hand, mainly recruited into complete clearings (100% removal), but when their recruits were abundant, they also recruited into partial clearings. The covers of filamentous, turf-forming algae increased in all clearings, and more so at exposed than sheltered sites. Extent of disturbance had no detectable effect on recolonisation by canopy-forming algae across the scales examined (i.e., 1.5 m, 3 m diameter loss of canopy). Recolonisation varied among islands kilometres apart, and correlations (r > 0.85) between cover of canopies and cover of their recruits in clearings at the scale of sites, suggested that differences in propagule supply could account for variation in patterns of recolonisation at scales of kilometres. There was no evidence to suggest that the effect of disturbance depended on wave exposure within the range of exposures tested in this study (i.e. open coasts). We recognise that wave exposure can be fundamental to habitat structure of subtidal rocky coasts, but we suggest that its influence may be mediated by the biological setting (e.g., canopy composition). 相似文献
2.
Echinogammarus marinus constitutes the most abundant amphipod species in Fucus spp. assemblages from many North Atlantic estuaries. However, there are some doubts about the real use of fucoids by the amphipod. Whilst some studies report the ingestion of Fucus vesiculosus by E. marinus, others suggest that the amphipod preference for fucoids is mostly related to sheltering rather than feeding, due to the high phlorotannin content of brown algae. The purpose of the present work was to disentangle this issue by checking the consumption rate and feeding preference of E. marinus on F. vesiculosus, its preferential habitat, and on Ulva intestinalis, a green algae abundant in the Mondego estuary (Western Coast of Portugal) and usually considered as highly palatable for herbivores.In a 2-stage laboratorial setup, fresh disks of the two types of algae were offered to E. marinus for three days. Consumption rates were estimated from differences between algal and animal initial and final fresh weights using a control correction factor, while preference was tested by differences in algal consumption rates when no choice was offered (stage 1) and when the two algae were offered simultaneously (stage 2).Results showed that E. marinus effectively consumed fresh F. vesiculosus in much higher amounts than U. intestinalis and significantly preferred to consume F. vesiculosus over U. intestinalis. Therefore, feeding habits must be one of the factors related to the close association of the amphipod with F. vesiculosus, although other factors may also be involved (e.g. sheltering). 相似文献
3.
Fitness‐related consequences shed light on the mechanisms of covering and sheltering behaviors in the sea urchin Glyptocidaris crenularis 
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下载免费PDF全文 We know of no comparative assessment on the benefits and costs of long‐term covering and sheltering behaviors in sea urchins. The present study investigated the long‐term effects of conditions suitable for sheltering and covering behaviors on fitness‐related traits of sea urchins Glyptocidaris crenularis. In general, conditions suitable for covering and sheltering behaviors significantly affected the fitness‐related traits of G. crenularis in a long‐term laboratory study of 31 months. Glyptocidaris crenularis kept in conditions suitable for sheltering behavior (bricks with openings) showed significantly lower test size, body weight, organ (test, lantern, gonad and gut) weights, gonad index and slower gonad development than those kept in conditions suitable for covering behavior (presence of shells) and the control conditions (without conditions for covering and sheltering). However, the index of maximum pressure resistance of the test was significantly higher in G. crenularis kept in the sheltering conditions than those in the covering and control conditions. The present study provides new insight into the mechanisms of covering and sheltering behaviors and has implications for the conservation and aquaculture of sea urchins. 相似文献
4.
Altered Benthic Prey-Availability Due to Episodic Oxygen Deficiency Caused by Drifting Algal Mats 总被引：8，自引：0，他引：8
Abstract. Large quantities of drifting algal mats have become a common phenomenon on shallow sandy bottoms in the northern Baltic Sea. A decomposing algal mat rapidly induces hypoxic or anoxic conditions in the underlying sediment and interferes with the normal living-mode of the benthos, i.e., mobility, feeding, and predator-prey relationships. Field surveys have shown that bivalves, such as Macoma balthica , avoid the unfavourable anoxic conditions by emerging at the sediment surface. Due to low reburrowing rates these bivalves are exposed to epibenthic predators once the drift algae disperse. A series of aquarium experiments were conducted to test for differences in the survival of M. balthica when exposed to continuous predation without prior stress and short-term predation after hypoxic stress induced by algae (= 20% 02-saturation). Sublethally stressed adult M. balthica , that normally are outside the size-range of the isopod predator Saduria entomon , became significantly more susceptible to predation when lying exposed at the sediment surface. The same effects were found with two other predators, the brown-shrimp Crangon crungon and the flounder Platichthysflesus . Drift algal mats induced an escape-reaction in the infauna more rapidly than mere hypoxia. This response is affected by temperature. which further underlines the importance of drift algae influencing prey availability. This paper discusses the role of the drift algae as a regulating factor for the infauna and demonstrates the importance of external structuring factors, such as hypoxic stress and algal mats, on predator-prey interactions. 相似文献
5.
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
6.
The Nature Conservancy Council has carried out appraisals for the Department of Energy of environmental implications of siting full-scale floating or seabed-mounted wave energy converters off the west coast of the Outer Hebrides and full-scale floating devices off the Moray Firth.Converters would have a variety of effects on the hydraulic environment, most noticeably by modifying the local wave climate. A decrease in incident wave energy would influence shores and shallow subtidal areas and result in changes in the density and species of organisms they support. Extensive shell-sand beaches occur along the west coast of the Uists but although wave activity and wave steepness would be reduced, accretion on these beaches might be limited by the availability of sediment. Fixed converters off the Hebrides would have more pronounced environmental impacts than offshore floating devices, mainly through their greater sheltering effect, the possibly stronger tidal flows generated between devices and shores, and the need to site fixed converters in the kelp zone.Devices would represent a new habitat for colonisation by attached algae and invertebrates and would probably attract fish, seabirds and seals. Seabed-mounted devices, once no longer operational, would become artificial reefs if left in place.Device noise might affect communication and navigation systems of fish and marine mammals. The navigational hazard to shipping posed by converters would be likely to increase the risk of severe oil pollution incidents in areas that are populated by internationally important numbers of seabirds.Other impacts would arise from the construction and maintenance of devices, an increased demand for building aggregate, the likelihood of intertidal flats being reclaimed, and conversion and transmission of energy, and the general associated developments and industrialisation that would ensue.It is concluded that although wave energy conversion harnesses a renewable source of energy it is not necessarily environmentally benign. Nevertheless, no environmental questions have been raised which would necessarily rule out further consideration of this energy source. 相似文献
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有毒赤潮藻及其毒素的危害与检测 总被引：6，自引：0，他引：6
海洋中可引发赤潮的藻类约有300种,其中有毒赤潮藻为80种左右。现已知道的赤潮藻主要毒素有麻痹性贝毒、腹泻性贝毒、记忆缺失性贝毒、神经性贝毒、西加鱼度和溶血性毒素,前5种毒素的结构已经基本得到证实。有毒赤潮藻的毒素可以在海洋生物体内积累,人类误食含有藻毒素的食品时可能中毒,严重者还可能死亡。海洋有毒赤潮藻及其毒素的检测已经成为当今全球赤潮研究和监测的重要内容之一,可以通过形态学分类方法、分子生物学技术(遗传探针)和免疫学检测技术对有毒赤潮藻进行检测;可以通过生物学、物理化学检测方法和神经受体结合、免疫学检测技术对赤潮藻毒素进行检测。 相似文献
9.
On rocky shores, the relative importance of abiotic and biotic processes that regulate community structure are thought to vary with levels of shore exposure. This can lead to characteristic features found on sheltered and exposed shores. This study identified differences in the population structure of mussels on exposed and sheltered rocky shores on Atlantic coasts of south-west Ireland. Direct interactions between epibiotic algae and their host mussels were also examined to test if potential effects varied with shore exposure. Mussel beds on sheltered shores were less dense and comprised larger mussels with greater rates of individual survival and growth than those on exposed shores. The results of a field experiment showed that algal epibionts had a negative effect on mussel survival on sheltered shores but not on exposed shores. Surprisingly, the presence of algal epibionts had no effect on mussel growth on either shore type. These findings contrast with those of previous studies. The effects of shore exposure and algal epibionts on mussels may be species-specific and may interact with other factors across different regions. This study shows that predictions of effects of exposure on mussel populations and their epibionts should only be based on specific experimental evidence and cannot be generalised across regions. 相似文献
10.
褐藻多糖硫酸酯是一种含有硫酸基的水溶性杂聚糖,其化学组成对抗氧化活性有较大的影响。本文对三种褐藻来源的褐藻多糖硫酸酯及其降解产物化学组成和抗氧化活性进行了研究,阐明了不同来源褐藻多糖硫酸酯体外抗氧化活性的构效关系。实验结果表明:1)分子量对抗氧化活性有较大影响,但是对不同褐藻来源的褐藻多糖硫酸酯的影响趋势并不一致。2)岩藻糖、硫酸基和糖醛酸含量对清除超氧阴离子自由基的影响与分子量有一定的关系。对于低分子量样品,岩藻糖和硫酸基含量与抗氧化活性成正相关。3)岩藻糖和硫酸根的比值对羟基自由基的清除能力有一定影响,比值越大,羟基自由基的清除能力越强。分子量、岩藻糖、硫酸基和糖醛酸的含量对褐藻多糖硫酸酯的抗氧化活性的影响依次减小。本研究为褐藻多糖硫酸酯在抗氧化剂保健品和功能食品中的应用提供了基础数据,也为裙带菜、羊栖菜和铜藻的高值化利用提供了理论依据。 相似文献
11.
Habitat complexity strongly influences reef fish community composition. An understanding of the underlying reasons for this relationship is important for evaluating the suitability of artificial reef (AR) habitats as a marine resource management tool. We studied the influence of AR habitat structure on fish assemblage composition off the southern coast of Brazil. We found that reef blocks with greater area and number of holes possessed the greatest fish species richness and abundance. Reef blocks with greater complexity had higher abundance of almost 30% of fish species present. Natural reef (NR) and AR were different in their fish species composition, trophic structure and categories of water column occupancy by fish (spatial categories). Although NR was more diverse and harboured more trophic levels, AR presented the higher abundances and the presence of distinct fish species that underlined their importance at a regional scale. The greater availability of sheltering habitat where hard substrate is scarce, together with their frequent use by economically important species, make AR a useful tool for coastal management when certain ecological conditions are met. 相似文献
12.
苏北浅滩养殖筏架附生绿藻入海过程在黄海绿潮形成中的作用 总被引：3，自引：0，他引：3
本研究采用现场定量观测为主的研究方法,在2017年5月期间对苏北浅滩竹根沙收紫菜养殖筏架作业过程进行跟踪调查;对养殖筏架绠绳附生绿藻自然脱落和收筏架作业过程人为刮落附生绿藻,以及收筏架作业前后入海的漂浮绿藻生物量进行定量观测。结果表明:筏架绳附生绿藻自然脱落率低,为3.58%±0.78%;收筏架作业过程中绠绳上刮落绿藻生物量为(12±3)kg湿重/根,由此估算2017年整个苏北浅滩刮落的生物量估算可达到万吨湿重;收筏架作业后海域漂浮绿藻生物量是作业前的7.6倍。研究结果进一步明确了收筏架作业过程中人为刮落绿藻是目前筏架附生绿藻最主要的入海方式。刮落绿藻是海水中漂浮绿藻的主要来源,其生物量对南黄海绿潮的规模大小有重要的影响。研究结果为绿潮防控措施的制定和实施提供科学依据。 相似文献
13.
《中国海洋工程》2021,(4)
The multi-body system has been a popular form for offshore operations in terms of high efficiency. The wind effects are crucial which directly affect the relative positions of floating bodies and operating security. In this study, the aerodynamic characteristics for two coupled semi-submersibles were analyzed in a wind tunnel to fill the gaps in literature related to the wind sheltering on offshore platforms. The influences of separation distance were also investigated. According to the results, substantial shielding effects were observed and wind forces on the shielded vessel decreased dramatically: a reduction in the transverse force could be up to 74%. Moreover, the longitudinal wind load was amplified by the platform abreast in a side-by-side configuration. As expected, the interference level became more pronounced with a decreasing separation distance. For cases in which wind interaction decayed rapidly with distance, logarithmic functions were preferable for describing the relationship between them. Whereas linear fitting was reasonable for the transverse wind force when there was still evident sheltering at a quite large distance.The length of shielding area was another important factor that there was approximately a linear relationship between it and the shielding level for two platforms in close proximity at various wind attack angles. Based on the two parameters, a preliminary wind loads estimation method considering shielding effects was proposed. This approach can aid the industry to have a qualitative assessment of wind sheltering especially at early stages. 相似文献
14.
Effects of point-source nutrient addition and mussel removal on epibiotic assemblages in Perumytilus purpuratus beds 总被引：2，自引：0，他引：2
The objective of this study was to evaluate the effects of point-source nutrient addition and mussel removal on species diversity of the epibenthic assemblage of the purple mussel Perumytilus purpuratus. It was hypothesised that mussels cushion the effects of disturbance on the associated organisms and thereby favour species diversity in patches with added nutrients. In order to test this hypothesis, a two-factorial field experiment was conducted at an exposed rocky shore of northern-central Chile in which nutrient addition and mussel removal were manipulated with two levels. Experimental units consisted of 100-cm2 mussel plots that were sampled after two months of experimental manipulations. Local nutrient addition was done with coated slow-release fertilisers. Mussel removal treatments consisted in three destructive events applied throughout the experimental phase, and each event consisted in the removal of 20% of the mussel biomass from each plot. While point-source nutrient addition had only minor effects on diversity, mussel removal had significant and negative effects on faunal species richness and the abundance of suspension-feeders and sessile organisms. The abundance of predators/scavengers significantly decreased with mussel removal in the presence of nutrient addition. Grazers and mobile organisms were very abundant in the mussel assemblage but their abundance remained unaffected by treatments. Finally, species richness and total abundance of algae were also not affected by the treatments. Although the duration of our experiment was relatively short, we suggest that the effects of local nutrient addition are of minor importance at the study site in comparison to the effects of mussel removal. Based on our results and previous studies conducted in soft-bottom systems, we suggest that physical and biological stress acting on exposed hard-bottom communities overshadows the potential effects of local nutrient addition. 相似文献
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16.
《Journal of Sea Research》2007,57(4):271-283
The objective of this study was to evaluate the effects of point-source nutrient addition and mussel removal on species diversity of the epibenthic assemblage of the purple mussel Perumytilus purpuratus. It was hypothesised that mussels cushion the effects of disturbance on the associated organisms and thereby favour species diversity in patches with added nutrients. In order to test this hypothesis, a two-factorial field experiment was conducted at an exposed rocky shore of northern-central Chile in which nutrient addition and mussel removal were manipulated with two levels. Experimental units consisted of 100-cm2 mussel plots that were sampled after two months of experimental manipulations. Local nutrient addition was done with coated slow-release fertilisers. Mussel removal treatments consisted in three destructive events applied throughout the experimental phase, and each event consisted in the removal of 20% of the mussel biomass from each plot. While point-source nutrient addition had only minor effects on diversity, mussel removal had significant and negative effects on faunal species richness and the abundance of suspension-feeders and sessile organisms. The abundance of predators/scavengers significantly decreased with mussel removal in the presence of nutrient addition. Grazers and mobile organisms were very abundant in the mussel assemblage but their abundance remained unaffected by treatments. Finally, species richness and total abundance of algae were also not affected by the treatments. Although the duration of our experiment was relatively short, we suggest that the effects of local nutrient addition are of minor importance at the study site in comparison to the effects of mussel removal. Based on our results and previous studies conducted in soft-bottom systems, we suggest that physical and biological stress acting on exposed hard-bottom communities overshadows the potential effects of local nutrient addition. 相似文献
17.
用海藻磨碎液进行海湾扇贝促熟的研究 总被引：4，自引：0，他引：4
本文阐述了在海湾扇贝人工育苗中,用海藻磨碎液代替单胞藻类进行海湾扇贝促熟的研究。两年的生产实践已证明海藻磨碎液完全可替代单胞藻促使亲贝提早成熟,这将为扇贝育苗中饵料的开发利用开创了一条新途径,从而大大降低了生产成本。 相似文献
18.
Richard D. Kalke Thomas A. Duke R. Warren Flint 《Estuarine, Coastal and Shelf Science》1982,15(1):75-84
The impact of weathered IXTOC I oil on experimental benthic communities colonized in the laboratory and in situ was observed. Test systems containing clean sand and receiving seawater from Aransas Pass Inlet were placed in the laboratory while similar systems were placed on the seafloor. All of these test systems were allowed to colonize for 8 weeks by settlement of planktonic larvae. Weathered IXTOC I oil was added to randomly selected laboratory and in situ replicate compartments within the test systems and these were then exposed to flowing seawater in the laboratory for an additional 4 weeks. Observations of the structure and biomass of the communities at the end of the 12-week period indicated no significant effects on the laboratory colonized communities. However, total density was significantly affected in the in situ colonized systems as was species composition. Although not significant, total biomass was substantially reduced by oiling. Eh measurements of sediments showed that the oil reduced the depth of the oxygenated layer approximately half. This reduction may reduce subsurface benthic production and alter processes such as nutrient regeneration. 相似文献
19.
冰脊间遮掩作用对冰?水拖曳力影响的实验研究 总被引：1，自引：1，他引：0
为定量研究多冰脊之间的尾流遮掩作用对海冰漂移运动的影响,物理模型试验（试验有限水深为0.45 m）测量了多冰脊拖曳力的衰减变化。冰脊模型选用底角为45°的等腰直角三角形,选取了4种入水深度、9种冰脊间距进行测量。试验得到了前后冰脊拖曳力及其比值在尾流遮掩情况下的变化规律。前冰脊拖曳力与单冰脊情况一致,与冰脊速度的平方保持线性关系;而后冰脊在间距较小时出现了反向拖曳力,随冰脊间距的增大,后冰脊拖曳系数先减小再增大至不变。前后冰脊拖曳力比值的变化规律可以用指数遮掩函数来描述,该遮掩函数与冰脊间距和入水深度有关而与流速无关。通过与现有海冰模式中的遮掩函数对比,研究结论增强了该指数公式的适用性,加强了对海冰动力学模式中遮掩函数的理解。 相似文献
20.
人工藻礁是进行藻场建设的重要手段,但由于海胆等食藻类生物的摄食,将会影响藻类的生长,从而影响人工藻场的建设效果.为解决人工藻场建设中海胆的食害问题,从礁体自身设计出发,实验设计了8种不同形状的藻礁,选用光棘球海胆和中间球海胆为实验对象,观察比较了不同形状藻礁对海胆攀爬的阻碍效果,实验发现:侧周面为锯齿形或侧周面缠挂多孔柔性材料的礁型可有效阻止海胆攀爬,起到防止海胆摄食礁顶藻类的目的.研究结果为人工藻礁的设计提供了参考依据. 相似文献