三个种群可解模式的生态系统

由于生物科学的进一步发展以及相互渗透，一些数学家和生态学家对采用数学模式来描述生物种群的生态规律愈来愈感兴趣。[1]中讨论了三个种群可解模式的生态系统，即一个被捕食种群N1(即被捕食的成员数为N1，或被捕食的种群密度为N1，其它情况类似，不另作说明)和二个捕食种群N2、N3；二个被捕食种群N1、N2和一个捕食种群N3；三步捕食者一食饵系统的食物链N1、N2、N3。     

卤虫在单细胞藻类培养中作用的初步观察

在扁藻（Ｔｅｔｒａｓｅｌｍｉｓｓｐ．和Ｐｌａｔｙｍｏｎａｓｓｐ．）藻液中接种适量的卤虫（Ａｒｔｅｍｉａｓａｌｉｎａ）,通过卤虫对藻液中细菌及原生动物等敌害生物的捕食作用,可以有效地控制敌害生物对藻类的危害。通过卤虫对藻液中衰老及死亡的藻细胞的捕食,可以使藻种得以优化。而且,通过卤虫的代谢作用,藻类生长所必需的营养元素得以还原。     

细说极地海洋生物多样性调查

所谓生物多样性是指地球上所有的生物体及其所构成的综合体,它包括遗传多样性,物种多样性和生态系统多样性三个层次。换句话说,生物多样性是生物和它们组成的系统的总体多样性和变异性。生物多样性是地球生命数十亿年发展进化的结果,它是人类赖以生存和持续发展的物质基础。 但是，随着环境不断遭受破坏，森林砍伐、植被破坏、滥捕乱猎、污染频发，据估计，目前世界上的生物物种正在以每小时一种的速度消失。而自然物种一旦消失，就不会再生。更可怕的是，生物物种的消失，不仅仅是单一自然资源的损失，还会引起一系列连锁反应，从而影响其他物种的生存。     

长江口及邻近水域的生物多样性变化趋势分析

从长江口及邻近水域的生物多样性变化及导致生物多样性变化的相关环境因子来剖析长江口及邻近水域的生态环境变化趋势。长江口及邻近水域的生物多样性比较丰富。近20a来在人类活动影响下,长江河口区和冲淡水区浮游生物和底栖生物的物种大幅减少：优势浮游生物的生物量增加,部分种类异常增殖发生赤潮,底栖生物生物量明显减少;群落结构趋向简单,表现为单种优势,生物多样性下降。影响长江口及邻近水域生物多样性的原因包括自然因素和人为因素,近20a来生物多样性的降低主要归咎于人类的开发活动,不合理排污导致的富营养化对浮游生物的多样性丧失起重要作用,水利工程建设及滩涂围垦使海洋生物栖息地片段化,单调化,加速了生物多样性的降低。     

海南珊瑚礁生物多样性的保护现状与研究展望

珊瑚礁生物多样性保护是全球面临的重要问题之一,文章对海南珊瑚礁生物多样性保护现状进行了综述,分析了海南珊瑚礁生物多样性面临的主要威胁。在此基础上,提出了珊瑚礁生物多样性保护中亟须解决的问题。     

三个种群可解模式的生态系统

引言 由于生物科学的进一步发展以及相互渗透,一些数学家和生态学家对采用数学模式来描述生物种群的生态规律愈来愈感兴趣。[1]中讨论了三个种群可解模式的生态系统,即一个被捕食种群N_1(即被捕食的成员数为N_1,或被捕食的种群密度为N_1,其它情况类似,不另作说明)和二个捕食种群N_2、N_3;二个被捕食种群N_1、N_2和一个捕食种群N_3;三步捕食者—食饵系统的食物链N_1、N_2、N_3。略去了年龄差异,同时     

基于海岛管理的南麂列岛生物多样性保护实践与经验

随着海岛开发热潮的不断升温,海岛生态环境及生物多样性保护问题也越来越突出,如何维持海岛生态系统的良好状况,修复受损生态系统,促进海岛经济、社会和环境的可持续发展已经成为一个全球热点的问题。基于此,中国南部沿海生物多样性管理项目把南麂列岛作为4个示范区之一,围绕海岛综合管理建立生物多样性保护模式。通过本项目的有效实施,南麂列岛国家级海洋自然保护区的管理能力得到了进一步加强;城镇规划在经济发展和生物多样性保护协调中进行了修编并付诸实施;成功实施了铜藻生态修复为其他保护区提供了示范意义;形成的社区共管机制不仅解决了当地居民的可替代生计问题,保证当地村民的收益,还使生物多样性得到有效的保护。从而消除或减轻了南麂列岛海洋自然保护区的缓冲区和实验区及其外围威胁生物多样性的活动,成功地示范适当并可行的保护与可持续利用途径,实现了海洋生物多样性保护以及海洋生物资源的可持续利用,在全国和全世界范围内示范推广。     

1992—2012杭州湾海域生物多样性的变化趋势及原因分析

本文依据浙江省舟山海洋生态环境监测站(1992—2012年)20年的杭州湾生态环境质量监测数据,对杭州湾海洋生物多样性的现状及发展趋势进行了分析,并结合环境因子对生物多样性的变化原因进行了探讨。结果表明:杭州湾海域生物生存环境较为恶劣,生物多样性较低,生物群落结构简单,种类较少。20年间,杭州湾海域生物多样性的变化可大体分为2个阶段,第一阶段是20世纪90年代初至2000年,杭州湾生物群落的各项指标普遍呈现下降的趋势;第二阶段是2000年后至今,由于各项生态环境保护措施加强,杭州湾生物群落得到一定程度的恢复。相关性分析表明,DIN、DIP、COD和富营养化对杭州湾海域生物多样性产生了显著的影响。20年来杭州湾海域生物多样性的变化主要受人类活动的影响,污水排放导致的富营养化对生物多样性的丧失也有很大影响,滩涂围垦等沿海开发使海洋生物栖息地片段化,单调化,加速了生物多样性的降低。     

基于海岛管理的南麂列岛生物多样性保护实践与经验

随着海岛开发热潮的不断升温,海岛生态环境及生物多样性保护问题也越来越突出,如何维持海岛生态系统的良好状况,修复受损生态系统,促进海岛经济、社会和环境的可持续发展已经成为一个全球热点的问题.基于此,中国南部沿海生物多样性管理项目把南麂列岛作为4个示范区之一,围绕海岛综合管理建立生物多样性保护模式.通过本项目的有效实施,南麂列岛国家级海洋自然保护区的管理能力得到了进一步加强;城镇规划在经济发展和生物多样性保护协调中进行了修编并付诸实施;成功实施了铜藻生态修复为其他保护区提供了示范意义;形成的社区共管机制不仅解决了当地居民的可替代生计问题,保证当地村民的收益,还使生物多样性得到有效的保护.从而消除或减轻了南麂列岛海洋自然保护区的缓冲区和实验区及其外围威胁生物多样性的活动,成功地示范适当并可行的保护与可持续利用途径,实现了海洋生物多样性保护以及海洋生物资源的可持续利用,在全国和全世界范围内示范推广     

国际海洋浮游动物研究进展

综述了国际上有关海洋浮游动物种群、群落结构、多样性及浮游动物对全球气候变化响应等方面研究进展。海洋浮游动物种类繁多, 数量丰富, 分布广泛, 是海洋生态系统中最重要的生物类群。在海洋食物网中, 浮游动物通过摄食浮游植物控制初级生产力, 同时, 又被更高营养阶层的动物(鱼、虾、鲸、海鸟等)捕食, 充当次级生产者的角色, 其群落结构、种群动态和物种多样性影响鱼类和其他海洋动物资源量, 浮游动物是海洋食物网中关键环节。海洋生态系统动力学过程的关键环节是浮游生物的生物学和生态学过程, 多项国际研究计划以生物多样性和年际变化趋势为研究重点并联系全球变化及响应, 因此, 浮游动物的研究已成为海洋生态研究的核心内容之一。国际上对浮游动物的研究主要集中在以下6个方向:(1)浮游动物生境、种群的分布和扩散动力学研究;(2)浮游动物的群落结构和多样性;(3)浮游动物的实验生态和现场受控生态研究;(4)浮游动物对全球气候变化的响应;(5)深海、南北极、低氧区等极端生境的浮游动物生态学研究;(6)浮游动物研究新技术和方法。     

Predominance of parallel‐ and cross‐predation in anglerfish

Several studies in the last 20 years have revealed that morphological asymmetry in fish can be characterized as ‘antisymmetry’. Antisymmetry is a lateral dimorphism in which each population consists of individuals with well‐developed left sides (lefties) and well‐developed right sides (righties). This dimorphism influences predator–prey interactions. In some piscivorous fishes, it has been found that predators can catch more prey of the opposite morphological type to themselves (cross‐predation) than of the same morphological type (parallel‐predation). Our previous work clarified that the predominance of cross‐predation is caused by lateralized behaviors of predators and prey that correspond to their morphological antisymmetry. Moreover, based on the results of our behavioral observations, we hypothesized that parallel‐predation can predominate when predators encounter the potential prey frontally. To test this hypothesis, in the present study we investigated the relationship between lateral morphological types of anglerfish (Lophiomus setigerus) and those of the prey fishes found in their stomachs. Anglerfish attract potential prey using their first dorsal fin (illicium) as a lure, and their frontal encounters with potential prey fishes were photographed in situ and observed in an aquarium. The results of a stomach contents analysis indicated that parallel‐predation predominated in five benthopelagic prey fish species (perches and eels). By contrast, five benthic prey fishes (gobies and weevers) exhibited the predominance of cross‐predation. These results not only demonstrate the predominance of parallel‐predation in a natural fish community, but also suggest that the relationship between morphological types of predator and prey species can be reversed depending on the lifestyle of prey.     

Scales of predator detection behavior and escape in Fissurella limbata: A field and laboratory assessment

The consumptive effects of predators are widely acknowledged, but predation can also impact prey populations through non‐consumptive effects (NCEs) such as costly antipredator behavioral responses. The magnitude of antipredator behavioral responses by prey is determined by an assessment of risk using sensory cues, which in turn is modulated by the environmental context. We studied the detection behavior and escape response of the keyhole limpet Fissurella limbata from the predatory sea star Heliaster helianthus. Through laboratory and field experimental trials, we quantified the distance and time of predator detection behavior by the prey, and measured their active escape responses when elicited. We found that predator detection by the limpet was chiefly mediated by distance, with experimental individuals capable of detecting predator presence effectively up to distances of at least 50 cm in the field and 70 cm under laboratory conditions. Our results indicate that this prey species is able to evaluate the proximity of its predator and use it as an indication of predation risk; therefore, predator–prey distance appears to be a primary predictor of the magnitude of the antipredator response. Given the tight relationship between predator distance and prey movement and the important role herbivores can play, particularly in this ecosystem, we expect that NCEs will cascade to the patterns of abundance and composition of rocky shore communities through changes in prey foraging behavior under risk.     

Predatory Promesostoma species (Plathelminthes, Rhabdocoela) in the Wadden Sea

Laboratory experiments were performed on the food ecology of four congeneric species of free-living plathelminths, Promesostoma caligulatum, P. marmoratum, P. rostratum, and P. meixneri, all inhabiting an intertidal sandflat near the island of Sylt (North Sea). Their prey spectrum is within the microcrustaceans: P. caligulatum preferred ostracods, while the other three species favoured copepods, with species-specific differences for copepod species and size classes. Daily consumption of prey species varied with the size of both the predator and the prey. On average, P. marmoratum consumed 0.76 Harpacticus flexus per day while this rate decreased to 0.06 in P. meixneri, the smallest predator. When these Promesostoma species were fed with Tachidius discipes, a smaller prey species, their predation rates were about 25% higher. While the larger predators preferred the larger harpacticoids as prey, the small P. meixneri preferred small cyclopoids over larger harpacticoids. In terms of biomass, P. marmoratum's mean consumption of T. discipes per day was about half the predator's own weight. This average varied with prey density and temperature. A comparison of these consumption rates with the field densities of the predators and their prey shows that the plathelminth predators may consume as much as 10% per day of their copepod prey populations, thus strongly influencing these prey populations on these sandflats. The predation pressure of P. caligulatum on ostracods was about 1% per day of the prey population. Since ostracods usually have fewer generations per year, the total effect on the population dynamics may be similar to that on copepods. Therefore, nocturnal swimming of copepods in the water column may be interpreted as an attempt to escape plathelminth predators.     

Changes in survivorship,behavior, and morphology in native soft‐shell clams induced by invasive green crab predators

Many studies on invasive species show reduced native densities, but few studies measure trait‐mediated effects as mechanisms for changes in native growth rates and population dynamics. Where native prey face invasive predators, mechanisms for phenotypic change include selective predation, or induced behavioral or morphological plasticity. Invasive green crabs, Carcinus maenas, have contributed to declines in native soft‐shell clams, Mya arenaria, in coastal New England, USA. We tested the hypothesis that clam ability to detect chemical cues from predators or damaged conspecifics would induce greater burrowing depth as a refuge from invasive crabs, and greater burrowing would require increased siphon growth. To determine how crab predation affected clam survivorship and phenotypic traits in the field, clams in exclosure, open, and crab enclosure plots were compared. Crab predation reduced clam density, and surviving clams were deeper and larger, with longer siphons. To determine whether the mechanism for these results was selective predation or induced plasticity, phenotypes were compared between clams exposed to chemical cues from crab predation and clams exposed to seawater in laboratory and field experiments. In response to crab predation cues, clams burrowed deeper, with longer siphons and greater siphon mass. Overall, crab predation removed clams with shorter siphons at shallow depths, and crab predation cues induced greater burrowing depths and longer siphons. Longer siphons and greater siphon mass of deeper clams suggests clams may allocate energy to siphon growth in response to crabs. By determining native behavior and morphological changes in response to an invasive predator, this study adds to our understanding of mechanisms for invasive impacts and illustrates the utility of measuring trait‐mediated effects to investigate predator–prey dynamics.     

Wasp-waist populations and marine ecosystem dynamics: Navigating the “predator pit” topographies

Many marine ecosystems exhibit a characteristic “wasp-waist” structure, where a single species, or at most several species, of small planktivorous fishes entirely dominate their trophic level. These species have complex life histories that result in radical variability that may propagate to both higher and lower trophic levels of the ecosystem. In addition, these populations have two key attributes: (1) they represent the lowest trophic level that is mobile, so they are capable of relocating their area of operation according to their own internal dynamics; (2) they may prey upon the early life stages of their predators, forming an unstable feedback loop in the trophic system that may, for example, precipitate abrupt regime shifts. Experience with the typical “boom-bust” dynamics of this type of population, and with populations that interact trophically with them, suggests a “predator pit” type of dynamics. This features a refuge from predation when abundance is very low, very destructive predation between an abundance level sufficient to attract interest from predators and an abundance level sufficient to satiate available predators, and, as abundance increases beyond this satiation point, decreasing specific predation mortality and population breakout. A simple formalism is developed to describe these dynamics. Examples of its application include (a) a hypothetical mechanism for progressive geographical habitat expansion at high biomass, (b) an explanation for the out-of-phase alternations of abundances of anchovies and sardines in many regional systems that appear to occur without substantial adverse interactions between the two species groups, and (c) an account of an interaction of environmental processes and fishery exploitation that caused a regime shift. The last is the example of the Baltic Sea, where the cod resource collapsed in concert with establishment of dominance of that ecosystem by the cod’s ‘wasp-waist” prey, herring and sprat.     

Food web and fish stock changes in central Chile: comparing the roles of jumbo squid (Dosidicus gigas) predation,the environment,and fisheries

We analyzed recent food web and fish stock changes in the central Chile marine ecosystem, comparing the roles of jumbo squid (Dosidicus gigas) as predator, the environment, and fishing. To accomplish this we used food web modeling and the Ecopath with Ecosim software (EwE). The principal fish stocks have experienced wide decadal fluctuations in the past 30 years, including stock collapses of horse mackerel (Trachurus murphyi) and hake (Merluccius gayi), and there was a large influx of jumbo squid during the mid-2000s. We used two EwE models representing the food web off central Chile to test the hypothesis that predation by jumbo squid has been significant in explaining the dynamics of the main fishing resources and other species in the study area. Results indicate that predation by jumbo squid on fish stocks is lower than that of other predators (e.g. hake) and the fishery. Long-term fluctuations (1978–2004) in the biomass of the main fish stocks (as well as other components of the food web) seem to be related to fishing and to variation in primary production, rather than to predation by jumbo squid alone. Jumbo squid seems to play a role as predator rather than prey in the system, but its impacts are low when compared with the impacts of other predators and fishing. Therefore, we conclude that jumbo squid predation on its prey was not the primary force behind the collapse of important fish stocks off central Chile. Future efforts should be directed to better understanding factors that trigger sudden increases in jumbo squid abundance off central Chile, as well as modeling its trophic impacts.     

Feeding ecology of whelks on an intertidal sand flat in north‐eastern New Zealand

The dispersion patterns and feeding behaviour of intertidal whelks were investigated in north‐eastern New Zealand. Aggregations of whelks feeding on clams occurred regularly, with an average of 15–20 individuals per aggregation. Death of clams was attributable to predation in up to 50% of the aggregations, although scavenging of dead and moribund animals was the main activity of whelks. Laboratory and field studies showed that Lepsiella scobina (generally not considered a soft shore species) was the main whelk predator at Lews Bay, Whangateau Harbour, drilling a small neat hole through the clam shell. The distinction between Cominella spp. as predators or scavengers is not so clear. Reseeding of intertidal clams, Austrovenus stutchburyi, has been proposed as a technique for reestablishing populations in some degraded New Zealand estuaries. The impact of whelk predation has many implications for A. stutchburyi reseeding. Both L. scobina and Cominella adspersa may potentially prey on newly reseeded clams as they preferentially attacked small clams in the laboratory. On‐growing to a larger size before reseeding may be advantageous although large size was not found to protect prey from predation. Additionally, no seasonal trend in whelk activity was found.     

Effects of habitat complexity on cannibalism rates in European green crabs (Carcinus maenas Linnaeus, 1758)

The habitat in which predator–prey interactions take place may have a profound influence on the outcome of those interactions. Cannibalism is an intriguing form of predation whereby foraging by predators may contribute to the regulation of their own populations.This is particularly interesting in the case of invasive species, like the widely distributed European green crab (Carcinus maenas). This study explores how habitat complexity influences cannibalism rates in green crab populations of Prince Edward Island, Atlantic Canada. Both laboratory and field experiments were conducted to measure feeding rates by individual adult green crabs on a standard number of smaller conspecifics. In the laboratory, experimental treatments mimicked unstructured to increasingly structured habitats: water, sandy bottom, oyster shells, mussel shells, oyster shells with sandy bottom and mussel shells with sandy bottom. In those trials, adult green crabs consumed several times more juveniles on unstructured habitats than on the most structured ones, with a gradual decrease in predation rates across increasingly complex habitats. Field inclusion experiments used the same approach and were conducted in sandy bottoms, sandy bottoms with a layer of oyster shells and sandy bottoms with a layer of mussel shells. These trials showed similar patterns of decreasing feeding rates across increasingly complex habitats, but differences among treatments were not significant. These results support the idea that complex habitats have the potential to mediate predator–prey interactions, including adult–juvenile cannibalism in green crabs.     

Clam community composition and prey shell size impacts moon snail (Gastropod: Naticidae) drilling frequencies in South Carolina,USA

Moon snail predation on clams is a common model system of predator–prey interactions. In this system, the predator bores through the shell of its prey, leaving a distinct and identifiable hole. Some paleoecological and behavioral research on moon snails suggests a trend in predation preference directed toward clams with small shells. Rarely, however, have studies tested relative drilling frequencies across species and size ranges in natural assemblages of clam communities. We examined the clam community composition at two beaches in South Carolina, USA, and we then tested moon snail predator preferences for (a) clam prey species and (b) whether their selection is related to prey shell size. We collected a total of 1,879 clam shells, identified each shell to species and recorded their anteroposterior length. The species composition of clams differed significantly between the two beaches; Anadara ovalis was dominant at both sites, but three of ten total species were only collected at one beach. Folly Beach had nearly a 60% higher the overall drilling frequency (34.6%) versus Edisto Beach (21.8%), and this may be linked to the differences in clam community compositions at the sites. For A. ovalis and Mulinia lateralis, shells with larger lengths have lower probabilities of being bored by a moon snail. Anadara brasiliana, which generally is a thinner‐shelled clam species, had the highest total drilling frequency (77.2%), and Noetia ponderosa, a thicker‐shelled clam, had a considerably lower drilling frequency (12.0%). We conclude that both community level factors (species composition) and population characteristics (shell size distributions) may influence the local drilling frequency by moon snails.     

Field experiments on the role of epibenthic predators in determining prey densities in an estuarine mudflat

A series of caging experiments was performed on an estuarine mudflat at three seasons of the year, in which Carcinus maenas L. and Pomatoschistus microps (Kroyer) were either excluded from, or allowed to prey upon, the benthos in order to determine to what extent infaunal abundance and mortality was a result of predation by epibenthic predators.The difficulties of conducting and interpreting the results of such experiments are recognized. The benthic macrofauna of this mudflat is dominated numerically by small annelids and there is evidence that adult C. maenas can cause significant increases in the oligochaete component of this assemblage, probably as a result of disturbance caused by its burrowing activity. Juvenile C. maenas on the other hand significantly reduced the abundance of small annelids, particularly the dominant polychaete Manayunkia aestuarina (Bourne) and could be responsible for year-to-year variations in abundance of this species. The role of fish predators (in this case P. microps) is more problematical but it is suggested that in the densities at which they occur naturally on the mudflat they have little direct effect on the abundance of prey species. There is no evidence that seasonal mortality of small annelids is reduced in the absence of predation and this is taken to indicate that not all mortality is due to epibenthic predation. Certain changes in relative abundance of the component species of the harpacticoid copepod community were discerned but it is suggested that the plasticity of their reproductive potential is such that the effect of predation on the group as a whole is usually masked.