Recolonization pattern of the polychaete Lanice conchilega on an intertidal sand flat following the severe winter of 1995/96

The recolonization process of Lanice conchilega was studied on an intertidal sand flat in the northern Wadden Sea after an intertidal population had been wiped out during the severe winter of 1995/96. After very low recruitment in the first two years, the population fully recovered in the third year after its destruction. By then, the distribution pattern closely resembled the pattern before the severe winter with >95% of all Lanice occurring below –0.5 m mean tidal level and dominance of the density categories 6–50 individuals (ind) m^–2 and 51–200 ind m^–2. Lanice larvae have been observed to attach preferentially on the tubes of adults. However, the high recruitment in the third year was also seen in areas devoid of adult Lanice, indicating that settlement facilitation by adults was of little importance for the recolonization process. Instead, we suggest that the observed recruitment pattern was a consequence of a large-scale decline in the metapopulation in the tidal basin and the onshore coastal subtidal which resulted in insufficient larval supply onto the tidal flats and low recruitment in the first two years following the severe winter. Received in revised form: 7 May 2001 Electronic Publication     

Impact of the nemertean Lineus viridis on its polychaete prey on an intertidal sandflat

Interactions of the predator Lineus viridis (O. F. Muller 1774) with infaunal polychaetes were investigated in the German Wadden Sea. L. viridis is the dominant heteronemertean in this intertidal area with a mean abundance of 14 individuals per square meter. Predator enclosure experiments in the field revealed that L. viridis preyed on predatory polychaetes. The preferred prey species was Nereis diversicolor; others were Anaitides maculata. Nephtys hombergii and Harmothoe sarsi. These results were supported by a series of feeding experiments in the laboratory. The rate of consumption was estimated by laboratory and field experiments. The feeding rate of Lineus viridis was estimated by laboratory enclosure experiments to 5.6 g ashfree dry weight (AFDW) per square meter annually.     

Conditional responses of organisms to habitat structure: an example from intertidal mudflats

Habitat structure is often assumed to be a predictor of habitat function. However, habitat structure may be insufficient to predict the functional significance of a habitat if the level of resources in the habitat is a consequence of the interaction between the habitat structure and physical or biological factors. In this study, we investigated whether depressions in tidal flat sediments generated by stout razor clams, Tagelus plebeius, affect the spatial patterns of pit digging by deposit-feeding burrowing crabs, Chasmagnathus granulata. The pits dug by crabs while feeding overlapped with clam siphon holes at a frequency higher than expected at random, and measurements of pit-digging by crabs integrated over several days indicated a higher frequency of feeding in the sediment of depressions. The daily frequency of pit-digging by crabs in depressions was positively related to the organic matter content of their sediments, but was significantly higher than the frequency of pit-digging away from clam siphon holes only after events of high bedload sediment transport, when the organic matter in the sediments of these depressions peaked. This example demonstrates the conditional nature of the relationship between habitat structure and function by illustrating how a physical process—bedload sediment transport—may introduce variation in the function that depressions play as feeding sites for burrowing crabs. Published information suggests that such conditional responses of organisms to habitat structure: (1) occur in a variety of habitats; (2) involve a variety of structures either of biotic or abiotic origin; and (3) are the consequence of either physical or biological controls that vary in importance according to the general mechanism through which habitat structure affect resources. This broad experimental evidence suggests that the accuracy of predictive models linking habitat structure and function can be improved by incorporating a mechanistic perspective that allows recognition of the potential for conditional responses of organisms to habitat structure.     

Seagrass beds and intertidal invertebrates: an experimental test of the role of habitat structure

The majority of field experiments have been carried out on relatively small spatial and short temporal scales, but some of the most interesting ecological processes operate at much larger scales. However, large-scale experiments appropriate to the landscape, often have to be carried out with minimal plot replication and hence reduced statistical power. Here, we report the results of such a large scale, un-replicated field experiment on the Mondego estuary, Portugal, which nevertheless provides compelling evidence of the importance of habitat structure for invertebrate community composition and dynamics. In this estuary, seagrass beds have suffered a dramatic decline over the last 20 years, associated with changes in invertebrate assemblages. In addition, the most abundant species in the system, Hydrobia ulvae, displays distinctly different population structures in those sites. The aim of the field experiment was to test the hypothesis that these differences are related to enhanced survival of snails due to protection from avian or fish predators so that they can grow to larger body sizes in the more complex habitat provided by seagrass. We tested this hypothesis through a large-scale experiment using artificial seagrass beds over a 12-month period. Adult snail densities were higher in the artificial bed plots compared to controls. However, these differences emerged only slowly, related to snail growth rate. This suggests that protection from epibenthic predators can have a significant effect on population structure and hence biomass and productivity of key species in this system. However, the invertebrate assemblage in artificial seagrass plots and the natural seagrass bed, remained statistically separate by the end of the experiment. Handling editor: K. Martens     

Distribution patterns of polychaete fauna in an Arctic fjord (Hornsund, Spitsbergen)

Polychaetes are one of the most important groups of benthic organisms in marine ecosystems. They dominate on the Arctic shelf and play an important role in ecosystem functioning. This study focuses on the polychaete biodiversity and their distribution patterns in Hornsund, an open glacial fjord, in western Spitsbergen and provides important baseline data for future studies of temporal fluctuations in benthic fauna. The main aim of this study was to assess how the polychaete abundance, biomass, diversity, community structure, and function vary along the Hornsund fjord’s axis, in relation to the environmental factors. Eighty-eight polychaete taxa were identified; an average density was 457 ind. m^?2 ± 237.5 SD. Three assemblages were distinguished (INNER, MIDDLE, and OUTER) along the fjord axis, reflecting the intensity of glacial disturbance. A clear division between the highly disturbed inner part of the fjord (Brepollen) and the less impacted middle and outer parts was observed. Continuous gradients in abundance, biomass, and diversity were found with all those values diminishing toward the inner region of the fjord. The polychaete assemblages' indices were significantly correlated with bottom temperature, sediment characteristics (grain size), and distance to the glacier (longitude). No significant correlations were found with depth or total organic carbon content. Carnivore and motile surface deposit feeding polychaete species dominated in the areas close to the glaciers, while the OUTER community was dominated by carnivores and surface sessile and discretely motile species, and had more complex trophic structure, with multiple species representing different functional groups including carnivores, sessile, discretely motile, and motile surface deposit feeders and motile burrowers.     

Ecology of bathyal polychaete fauna at an Arctic-Atlantic boundary (Faroe-Shetland Channel, North-east Atlantic)

By reference to a series of 15 sampling stations spanning the West Shetland Slope (150-1000 m; Faroe-Shetland Channel, North-east Atlantic) we examined the potential environmental controls on the standing stock, diversity and composition of the polychaete fauna. In contrast to the majority of studied bathyal environments, the Faroe-Shetland Channel has a highly complex and dynamic hydrographic regime, particularly notable for extreme thermal variability at mid-slope depths (i.e. 7°C range at ca. 500 m). Contrary to general expectation, polychaete biomass increased (rather than decreased) with depth. Species diversity exhibited a parabolic pattern with depth, maximum diversity occurring at depths of 350-550 m, rather shallower than observed in other bathyal studies, and possibly linked with a maximum in habitat temperature range. Multivariate analyses of faunal composition suggested a separation of the sampling stations into a shallower and a deeper group, with temperature exerting a major control on polychaete species distributions. The decline in diversity below 600 m (i.e. the descending limb of the parabolic relationship) may be a result of historically limited immigration/recolonization of the thermally isolated Arctic deep-water basins that feed the cold-water flow through the Faroe-Shetland Channel. The bathymetric distribution of polychaetes and other benthos in this region appears to be intimately linked with the thermal regime, having a long-term impact (geological timescales) on the deep-water species pool and leading to local enhancement of diversity where cold- and warm-water masses meet and mix.     

辽宁獐子岛马牙滩潮间带及近岸海区大型底栖动物群落特征

为摸清辽宁獐子岛潮间带及近岸海区的大型底栖动物的分布现状和群落受扰动情况,作者于2011年11月中旬在马牙滩潮间带和近岸海区采集大型底栖动物,采用优势度指数、Shannon-Wiener多样性指数、Margalef丰富度指数、Pielou均匀度指数,Bray-Curtis相似性聚类分析、MDS标序和ABC曲线等方法,分析该区域内大型底栖动物群落的生态学特点.结果表明,在潮间带共鉴定大型底栖动物39种,优势类群为多毛类、甲壳类和软体类;优势种均为多毛类,即小头虫(Capitella capitata)、多美沙蚕(Lycastopsis augenari)、仙居虫(Naineris laevigata)和短叶索沙蚕(Lumbrineris latreilli);平均生物量为25.76±41.08 g/m2,以软体动物占优势;平均栖息密度为315.11±160.73个/m2,以多毛类占优势;丰富度指数、均匀度指数与Shannon-Wiener多样性指数的平均值分别为1.17±0.89,0.74±0.17和1.80±1.09.近岸海区共鉴定大型底栖动物40种,优势类群为多毛类、甲壳动物、软体动物和棘皮动物.优势种包括4种棘皮动物和1种多毛类,即紫蛇尾(Ophiopholis mirabilis)、日本倍棘蛇尾(Amphioplus japonicus)、短叶索沙蚕、心形海胆(Echinocardium cordatum)和浅水萨氏真蛇尾(Ophiura sarsiivadicola).近岸海区的平均生物量和平均栖息密度分别为218.86±152.24g/m2和700.00±471.51个/m2,均以棘皮动物占优势.丰富度指数、均匀度指数与Shannon-Wiener多样性指数的平均值分别为1.40±0.60,0.64±0.19和2.04±0.78.聚类分析结果表明,潮间带不同潮区间和近岸海区不同断面间群落差异显著.ABC曲线分析显示,獐子岛潮间带底质环境受到中度扰动,大型底栖动物群落结构处于不稳定状态;近岸海区受到轻度干扰,群落结构未发生明显变化.     

Temporal variability of ecological niches: a study on intertidal macrobenthic fauna

The determination of temporal niche dynamics under field conditions is an important component of a species’ ecology. Recent developments in niche mapping, and the possibility to account for spatial autocorrelation in species distributions, hold promise for the statistical approach explored here. Using species counts from a landscape‐scale benthic monitoring programme in the western Dutch Wadden Sea during 1997–2005 in combination with sediment characteristics and tidal height as explanatory variables, we statistically derive realised niches for two bivalves, two crustaceans and three polychaetes, encompassing predators, suspension and bottom feeding functional groups. Unsurprisingly, realized niches varied considerably between species. Intraspecific temporal variation was assessed as overlap between the year‐specific niche and the overall mean niche, and this analysis revealed considerable variation between years. The main functional groups represented by these species showed idiosyncratic and wide variability through the study period. There were no strong associations between niche characteristics and mean abundance or body size. Our assessment of intraspecific niche variability has ramifications for species distribution models in general and offers advances from previous methods. 1) By assessing species’ realized niches in the multivariate environmental space, analyses are independent from the relative availability of particular environments. Predicted realized niches present differences between years, rather than annual differences in environmental conditions. 2) Using spatially explicit models to predict species habitat preferences provide more precise and unbiased estimates of species–environment relationships. 3) Current niche models assume constant niches, whereas we illustrate how much these can vary over only a few generations. This emphasizes the potentially limited scope of global change studies with forecasts based on single‐time species distribution snapshots.     

柘林湾-南澳岛潮间带冬夏两季大型底栖动物种类组成及优势种

依据柘林湾-南澳岛潮间带2011年8月、2012年2月、2013年2月和8月的大型底栖动物调查资料,对该海域潮间带的大型底栖动物种类组成和优势种进行研究。结果表明:4次调查共采集到大型底栖动物7门112种,主要由软体动物、节肢动物和环节动物3大类组成;总种类数夏季冬季;夏季2次调查的类群种类数组成存在显著性差异(P0.05),冬季2次调查不存在显著性差异(P0.05),冬夏两季不存在显著性差异(P0.05);冬季→夏季的种类更替率较高,该段时间内群落的变动相对较大,稳定性相对较低;4次调查出现优势种共有23种,优势种组成最多的为软体动物;柘林湾-南澳岛附近海域潮间带生物的种类和分布由底质类型决定,同时,人类活动对海域的生物生态也造成了一定的压力。     

Species persistence decreases with habitat fragmentation: an analysis in periodic stochastic environments

This paper presents a study of a nonlinear reaction–diffusion population model in fragmented environments. The model is set on , with periodic heterogeneous coefficients obtained using stochastic processes. Using a criterion of species persistence based on the notion of principal eigenvalue of an elliptic operator, we provided a precise numerical analysis of the interactions between habitat fragmentation and species persistence. The obtained results clearly indicated that species persistence strongly tends to decrease with habitat fragmentation. Moreover, comparing two stochastic models of landscape pattern generation, we observed that in addition to local fragmentation, a more global effect of the position of the habitat patches also influenced species persistence.      

Response of two species of amphibious stichaeoid fishes to temperature fluctuations in an intertidal habitat

The temperature regime of the intertidal microhabitat of two species of co-existing amphibious stichaeoid fishes, Anoplarchus purpurescens and Pholis ornata, were compared with experimentally determined tolerances to elevated temperatures. Studies of the critical thermal maxima of the two species revealed only slight differences in temperature tolerance but exposure to a cycled pattern of high temperatures sharply differentiated the resistance times of the two species with P. ornata capable of tolerating greater cumulative exposure to thermal stress when administered in a cycled program of temperature fluctuations with peak temperature at 27 °C. While the experimentally determined temperature tolerances exceeded those measured in the field, the greater tolerance of P. ornata may facilitate habitation of intertidal mudflats during summer months.     

Efforts to restore habitat connectivity for an upland tropical rainforest fauna: A trial of underpasses below roads

Summary Four large underpasses, specifically designed for movements by fauna, form part of a major road upgrade project on the Atherton Tablelands in northeast Queensland, Australia. We describe the design and rationale of a project to test their effectiveness in restoring habitat continuity for tropical rainforest fauna. The large blocks of upland rainforest divided by the road are recognized for their high faunal conservation significance, forming habitat for many rare or threatened species. Ecologists, road engineers and the Atherton Tablelands conservation community have united with a common conservation goal: to design the 'furniture' within the underpasses and accomplish rainforest revegetation to provide protective cover and attract fauna to underpass entrances. Prior to construction, small mammals were trapped weekly for several months in habitats close to the road upgrade. The small mammal community comprised grassland species in abandoned pasture and differed significantly from the rainforest specialists found in three closed canopy habitats: rainforest edge, rainforest interior and Lantana shrubland. Rainforest restoration works designed to restore connectivity for rainforest fauna across this abandoned pastureland (via the underpasses to major rainforest blocks to the north and south of the road) are currently in progress. Monitoring of the effectiveness of the underpasses in allowing faunal movements will involve the use of infra-red-triggered cameras within the underpasses and near underpass entrances, and a survey of road-killed fauna both prior to and postconstruction. Further examination of small mammal community structure and movements, with respect to both the new road and the underpasses, will be undertaken once rainforest plantings have become established. This evaluation should provide insights for further road-associated restoration projects in rainforest regions.     

The habitat function of mangroves for terrestrial and marine fauna: A review

Mangroves are defined by the presence of trees that mainly occur in the intertidal zone, between land and sea, in the (sub) tropics. The intertidal zone is characterised by highly variable environmental factors, such as temperature, sedimentation and tidal currents. The aerial roots of mangroves partly stabilise this environment and provide a substratum on which many species of plants and animals live. Above the water, the mangrove trees and canopy provide important habitat for a wide range of species. These include birds, insects, mammals and reptiles. Below the water, the mangrove roots are overgrown by epibionts such as tunicates, sponges, algae, and bivalves. The soft substratum in the mangroves forms habitat for various infaunal and epifaunal species, while the space between roots provides shelter and food for motile fauna such as prawns, crabs and fishes. Mangrove litter is transformed into detritus, which partly supports the mangrove food web. Plankton, epiphytic algae and microphytobenthos also form an important basis for the mangrove food web. Due to the high abundance of food and shelter, and low predation pressure, mangroves form an ideal habitat for a variety of animal species, during part or all of their life cycles. As such, mangroves may function as nursery habitats for (commercially important) crab, prawn and fish species, and support offshore fish populations and fisheries. Evidence for linkages between mangroves and offshore habitats by animal migrations is still scarce, but highly needed for management and conservation purposes. Here, we firstly reviewed the habitat function of mangroves by common taxa of terrestrial and marine animals. Secondly, we reviewed the literature with regard to the degree of interlinkage between mangroves and adjacent habitats, a research area which has received increasing attention in the last decade. Finally, we reviewed current insights into the degree to which mangrove litter fuels the mangrove food web, since this has been the subject of long-standing debate.     

Reproductive traits of a nonindigenous amphipod associated with alternative habitat structures in presence of an invasive ecosystem-engineering polychaete

Hydrobiologia - Understanding reproductive traits of invasive species and their modulation by different invaded habitats is crucial for monitoring invasive processes. The invasive ecosystem...     

The vertical distribution of the British intertidal Acari—the non halacarid fauna (Arachnida: Acari)

The vertical distribution of the non halacarid littoral Acari on rocky shores was examined. The habitat of these Acari was investigated and compared with that of the Halacaridae. Some physiological factors were investigated to explain this distribution. Three ecologically distinct life styles were recognized among these Acari.     

Influence of sponge morphology on the composition of the polychaete associated fauna from Rocas Atoll,northeast Brazil

The relationships between the morphology of sponges and variables describing their harbored polychaete fauna were analyzed along Rocas, the only known South Atlantic Atoll, together with the location on host and feeding habits. The identification and quantification of all the associated organisms highlighted the dominance of polychaetes. The adults of the symbiotic species Haplosyllis spongicola were the most dominant sponge endobionts. However, both juveniles and epitokes (reproductive individuals) of H. spongicola were also found, suggesting that this species completes its life cycle inside the host. Polychaete density was significantly greater in lobate sponges than in massive and encrusting forms. Conversely, the highly specific symbiotic mode of life of H. spongicola species seems to play a major role in structuring the composition of the polychaete fauna in relation to sponge morphotypes along Rocas Atoll.     

Recovery of intertidal mussel beds in the Waddensea: use of habitat maps in the management of the fishery

In the Waddensea, musselbed distribution and abundance has decreased. Management is aiming at increase of area of beds. Fisheries have been regulated. Mussel beds are slowly recovering, and localities where recovery occurs can be predicted reasonably well. Active restoration of beds has not been necessary, as long as newly formed beds are protected from fisheries. Potential suitable sites should be protected from bottom-disturbing activities which might influence the substrate for spatfall such as cockle beds and tube-building polycheates.     

Environmental factors structuring polychaete communities in shallow rocky habitats: role of physical stress versus habitat complexity

Polychaetes inhabiting 12 different hard bottom habitats were studied. A total of 157 species belonging to 32 families were identified. Differences among habitats in polychaete density, species richness, and diversity were analysed, as well as the relationships between these ecological indices and depth range, slope and in-bay/out-bay gradient. A high faunal homogeneity was found: all biotopes were dominated by a low number of eurytopic species. Intertidal habitats and subtidal ones with scarce algal cover were typified by vagile polychaetes (syllids, nereids), while sessile polychaetes (serpulids, sabellids) appeared typically among subtidal large macrophytes, habitats with a calcareous substrate and shaded habitats. Multivariate analyses showed that habitat complexity, determined by physical disturbance, is the main structuring factor for polychaete populations. Biotopes with the highest structural complexity displayed a high number of companion species increasing ecological indices and denoting a well-structured habitat. On the other hand, communities such as those in the upper intertidal, mainly controlled by physical environmental variables, showed a poorer polychaete fauna, dominated by ubiquitous species and a few well-adapted specialists.     

The use of habitat mosaics by terrestrial vertebrate fauna: implications for conservation and management

Many species of vertebrates require multiple habitats to obtain different resources at different stages of their life-cycles. Use of habitat mosaics takes place on a variety of spatial and temporal scales, from a daily requirement for adjacent habitats to seasonal use of geographically separated environments. Mosaics of habitats are also required in some species to allow ontogenetic habitat shifts, while in others each sex may have specific requirements that are met by different habitats. The extent and nature of animal movements are key (but generally poorly known) factors affecting the vulnerability of species to landscape change. The requirement by many species for multiple habitats suggests that their conservation will be most effective in a mosaic environment and that protection of certain high profile habitats alone, such as rainforest, will be insufficient to achieve conservation goals. Management regimes that result in homogenization of habitats should be avoided. Priority should be given to research that identifies the extent to which species can locate habitat mosaics, at different spatial scales and arrangements, in modified environments.