Feasible mechanisms for algal digestion in the king angelfish

To determine the ability of the king angelfish Holacanthus passer to digest algae, three algal species were immersed in acidic conditions similar to that found in the stomach of fish. Only one of them was not susceptible to acidic lysis; two were affected after 40 and 60 min at pH 2·0. King angelfish have an expanded region of the intestine called here the hindgut chamber (HC) containing populations of micro-organisms. Some of these micro-organisms have the capacity to grow in cellulose, agar, and alginic acid; the main components of algal cell walls. Micro-organisms grew in carboxymethylcellulose cultures under aerobic and micro-aerobic conditions. The HC is highly vascularized, which could increase absorptive efficiency of material digested in it.     

Population dynamics ofGlaux maritima (L.) along a distributional cline

Population fluctuations ofGlaux maritima, along a transect on a Baltle sea shore meadow, were recorded between 1979 and 1983. A bimodal distribution in numbers along the transect reflects the variation in factors regulating numbers: The two maintenance systems of the species, vegetative propagation and sexual reproduction play different roles. Vegetative propagation is fast and responds quickly to variations in the environment. The seeds germinate in strongly fluctuating temperatures which are triggered by disturbances such as flooding, damaging the vegetation.     

Adaptations for feeding on rock surfaces and sandy sediment by the fiddler crabs (Brachyura: Ocypodidae) Uca tetragonon(Herbst, 1790) and Uca vocans(Linnaeus, 1758)

Two species of fiddler crab, Uca tetragonon(Herbst, 1790) and Uca vocans(Linnaeus, 1758), which belong to the subgenus Gelasimus, dwell on rocky shores and muddy–sandy tidal flats, respectively, in Phuket Is., Thailand. We investigated their feeding ecology in relation to the morphology of their feeding organs: minor food-handling chelipeds and maxillipeds. U. tetragononfed chiefly on rocks covered by filamentous green algae. U. vocansfed on the emerged sand and in shallow water along the shoreline and in pools. While feeding, both crabs made sand pellets beneath their mouthparts and discarded them, indicating that they divided the matter scooped up with their minor chelipeds into edible and inedible fractions by using the maxillipeds in the water passing through their buccal cavity. The morphology of maxillipeds hardly differed between the two species, which means that both species are flotation-feeders. The morphology of their minor chelipeds, however, differed: the tips of the dactyl and pollex were flat in U. tetragononand pointed in U. vocans.When the minor cheliped was closed, U. tetragononhad a hemispherical space in the distal one-fourth of the gape, which was closed by the framing keratin layers and a few setae of the dactyl and pollex. On the other hand, U. vocanshad an ellipsoidal space in the distal half of the gape. We consider these morphological characters to be adaptations to the different feeding substrates for retaining more food-laden sediment. We discuss the role of the setae on the minor chelipeds on the basis of the morphological differences between populations of U. tetragononin Phuket Is. and East Africa where the crab inhabits muddy–sandy tidal flats.     

Amphibious behaviour and feeding ecology of the four-eyed blenny (Dialommus fuscus, Labrisomidae) in the intertidal zone of the island of Santa Cruz (Galapagos, Ecuador)

The labrisomid Dialommus fuscus , endemic to the Galapagos archipelago, is a predator of crustaceans, which moves up and down the intertidal zone with the tides. Its divided eye and elongated body permit it to forage in the wet sections of the intertidal habitat during low tide, both on the rocks and below the water line and in tide pools. Compared with other intertidal fishes (e.g. Bathygobius sp.), it was present on the rock flat in significantly smaller tide pools nearer to the water line during low tide.     

Diet composition influences the fitness of the herbivorous crab Grapsus albolineatus

The tropical rocky shore crab Grapsus albolineatus feeds primarily on filamentous algae but eats animal matter whenever it is available. During the summer the crab's diet switches to encrusting algae due to a die-off of filamentous algae. As a result of the switch the nutrients in the diet of the crab vary seasonally and may influence the fitness of the crab. Maintenance, growth, reproductive performance and nutrient storage of crabs were examined under four dietary regimes of increasing nutritional value ranging from low organic to high protein content. The nutritional quality of these diets significantly affected crab survival and moulting. Crabs fed on the nutritionally superior diet of algae and meat exhibited enhanced growth, higher levels of energy in the reproductive organs and stored more energy in the hepatopancreas than did individuals on the shore and crabs fed only on algal diets in the laboratory. Filamentous algae were a better food source than other algae, resulting in fewer deaths and superior levels of maintenance and growth. Growth and maintenance can occur on a pure algal diet, but reproductive performance and nutrient storage require some degree of added nutrients in the form of animal matter in the diet. Crabs fed coralline or foliose algae had higher mortality and fewer successful moults than crabs fed the other two diets. The fitness of G. albolineatus appears to be limited by the amount of extra nutrients obtained from animal matter. The opportunistic consumption of animal material in the form of carrion, or of animals associated with dietary algae, could be a key factor in the reproductive success of this crab.     

The efficiency and effectiveness of different sea urchin removal methods for kelp forest restoration

Sea urchin overgrazing has caused widespread phase shifts from kelp forests to “urchin barrens” on many temperate reefs, reducing habitat complexity, productivity, and biodiversity. Sea urchin removal is increasingly used for kelp restoration; however, few studies have quantified the efficiency and effectiveness of different removal methods, resulting in limited understanding of their practicality. In this study, the efficiency (removal rate) and effectiveness (proportion removed) of four removal methods were evaluated in northeastern New Zealand. We compared culling or collecting sea urchins by either SCUBA or freediving in 128 small-scale plots (25 m²). We also evaluated the efficiency and effectiveness of culling in four large (1.6–2 ha) barren areas, scales relevant for restoration. On average, culling sea urchins was 1.9–4.4 times faster than collecting, and SCUBA was 1.5–3.3 times faster than freediving. Removal rates increased with sea urchin density, especially for culling on SCUBA, while freediving removal rates increased with experience. Effectiveness was lower in large-scale removals (86–93% of sea urchins ≥40 mm removed) compared to small-scale removals (98–99%), but sufficient for restoration objectives. Estimated time per area (using SCUBA culling) was similar across large-scale removals (49–57 hours/ha), despite an almost 2-fold variation in initial sea urchin densities (approximately 4–8 urchins/m²), suggesting area may better predict total removal time than simply number of sea urchins across low-density ranges. While sea urchin removal provides a rapid, feasible, and effective approach to restoring kelp in urchin barrens, restoration plans need to also address the causes of sea urchin overpopulation to ensure long-term benefits.     

中国西南岩溶山地石漠化演变趋势

为揭示20世纪50年代末至今中国西南地区岩溶山地石漠化转型演变的时空分布及其特征,运用文献计量分析方法,对石漠化演变相关文献的总量和主题词进行了分析,并提取文献中石漠化演变的时间、类型、程度、驱动因素等信息,从县(市)域尺度对中国西南岩溶山地石漠化演变趋势及其空间分布进行综合分析,并进行了典型案例研究。研究表明,从20世纪50年代末至今,西南岩溶山地石漠化演变经历了由自然基础及人为破坏相互激发的严重石漠化向多种人为干扰、综合治理下的演变转型,即由高等级石漠化转向低等级石漠化的过程。在此基础上,研究认为石漠化存在由扩张向收缩转型演变的现象,同时对其转型演变的驱动机制和启示意义进行了探讨,以期为乡村振兴时代岩溶山地生态建设提供参考。     

强度石漠化区不同植被修复模式下土壤螨类群落差异

石漠化治理区不同植被修复模式下的土壤螨类群落差异反映了生态系统的恢复状况,可籍以反映石漠化治理的生态效果。2014年1月、4月、8月和10月,对贵州花江喀斯特峡谷区顶坛小流域强度石漠化区域的"花椒"、"金银花"、"花椒+金银花"3种植被修复生境的土壤螨类进行了调查,共捕获土壤螨类1372头,隶属3目55科89属。采用类群(属)数、个体数量、个体密度、多样性指数(H')、丰富度指数(SR)、均匀性指数(J)、相似性指数(CN)、捕食性螨类成熟度指数(MI)和甲螨MGP类群等参数对土壤螨类群落差异进行了表征。结果显示,花椒林拥有较丰富的螨类属,金银花林拥有较高的的个体数量和个体密度。不同模式下的科、属类群组成呈现差异;属数、个体数量存在一定的季节差异,花椒林的螨类属数、金银花林的螨类个体数量和个体密度呈现一定的表聚性;群落多样性大多存在季节差异;捕食性革螨以r选择型为主,甲螨主要为O型和M型。研究表明,强度石漠化在不同植被修复模式下,土壤螨类生物生态类群存在差异,土壤生态系统仍处于修复之中,其中螨类优势属、具有典型生物学与生态学特性差异的螨类类群对石漠化治理的生态效果具有重要的指示作用。     

中国西南喀斯特地区植被变化时空特征及其成因

2000年以来,国家在中国西南喀斯特地区开展一系列生态治理工程,该地区退化生态系统得到一定程度的恢复,而2008年开展石漠化综合治理工程以来该地区的植被覆盖和生产力如何变化尚不清楚。本研究利用遥感增强型植被指数(EVI)和总初级生产力(GPP)数据,研究2000—2015年西南喀斯特地区植被EVI年均值和GPP年总量的时空变化特征,重点探讨2008年以来石漠化综合治理工程、气候变化等因素对植被覆盖及生长的影响,进而评估石漠化综合治理工程的成效。结果表明,2000—2015年西南喀斯特地区植被EVI总体显著增加,其中2008—2015年植被EVI均值和变化率分别比2000—2007年高6.9%和85.7%,EVI显著增加的区域占西南喀斯特地区的13.4%;该区域GPP年总量亦呈显著增加趋势(20.58 g C m-2a-1)。2008—2015年气温和降水对植被EVI变化趋势的贡献仅占28.3%,退耕还林还草等生态恢复措施、大气CO2浓度、大气氮沉降的增加可能是该区域植被覆盖显著增加的主要贡献因子。在100个首批石漠化综合治理试点县中,大部分试点县植被EVI的变化趋势受非气候因子的影响,其中治理面积大的县受非气候因子的影响显著高于治理面积小的县,表明石漠化综合治理工程的实施有效地促进了试点县植被覆盖的增加。