Maintaining Biodiversity in Freshwater Ecosystems on Oceanic Islands of the Tropical Pacific

Duringthepastfiveyears,aresearchgroupfromtheHawai'iDivisionofAquaticRe-sourcesandtheLouisianaStaeUniversityMuseumofNaturalSciencehascollaboratedonaseriesofstudiesconcerningthebiologyandconservaionofstreamanimalsintheHawaiianIs-lands.Fromtheviewpointsofbothgeologyandbiology,theseislandsrepresentthenorth-ernmostextensonofPolynesia.StreamanimalsinHawai'ihaverelativesattheleveloffami-ly,genus,andoccasionallyevenspeciesnotonlyinPolynesiabutthroughoutMelanesiaandMicronesiaaswell.Forthisreason…     

Restoration Ecology: Repairing the Earth's Ecosystems in the New Millennium

The extent of human‐induced change and damage to Earth's ecosystems renders ecosystem repair an essential part of our future survival strategy, and this demands that restoration ecology provide effective conceptual and practical tools for this task. We argue that restoration ecology has to be an integral component of land management in today's world, and to be broadly applicable, has to have a clearly articulated conceptual basis. This needs to recognize that most ecosystems are dynamic and hence restoration goals cannot be based on static attributes. Setting clear and achievable goals is essential, and these should focus on the desired characteristics for the system in the future, rather than in relation to what these were in the past. Goal setting requires that there is a clear understanding of the restoration options available (and the relative costs of different options). The concept of restoration thresholds suggests that options are determined by the current state of the system in relation to biotic and abiotic thresholds. A further important task is the development of effective and easily measured success criteria. Many parameters could be considered for inclusion in restoration success criteria, but these are often ambiguous or hard to measure. Success criteria need to relate clearly back to specific restoration goals. If restoration ecology is to be successfully practiced as part of humanity's response to continued ecosystem change and degradation, restoration ecologists need to rise to the challenges of meshing science, practice and policy. Restoration ecology is likely to be one of the most important fields of the coming century.     

Positive Feedbacks in Seagrass Ecosystems: Implications for Success in Conservation and Restoration

Abstract Seagrasses are threatened by human activity in many locations around the world. Their decline is often characterized by sudden ecosystem collapse from a vegetated to a bare state. In the 1930s, such a dramatic event happened in the Dutch Wadden Sea. Before the shift, large seagrass beds (Zostera marina) were present in this area. After the construction of a large dam and an incidence of the “wasting disease” in the early 1930s, these meadows became virtually extinct and never recovered despite restoration attempts. We investigated whether this shift could be explained as a critical transition between alternative stable states, and whether the lack of recovery could be due to the high resilience of the new turbid state. We analyzed the depth distribution of the historical meadows, a long-term dataset of key factors determining turbidity and a minimal model based on these data. Results demonstrate that recovery was impossible because turbidity related to suspended sediment was too high, probably because turbidity was no longer reduced by seagrass itself. Model simulations on the positive feedback suggest indeed the robust occurrence of alternative stable states and a high resilience of the current turbid state. As positive feedbacks are common in seagrasses, our findings may explain both the worldwide observed collapses and the low success rate of restoration attempts of seagrass habitats. Therefore, appreciation of ecosystem resilience may be crucial in seagrass ecosystem management.     

Ecological Risk Assessment of China's Freshwater Ecosystems Applying the Relative Risk Model: Toward an Ecosystem-Based Water Management in China

The relative risk model (RRM) was applied to evaluate the ecological risk characterization of the freshwater ecosystems in China, from both overall and region-specific levels. Ten large-scale river basins (further broken into 15 risk regions) in China were chosen as the study objects; 10 sources, two habitats, and seven endpoints were identified as risk components. The results reveal the status of ecosystem conditions, key ecological risk issues, and the spatial heterogeneity of the freshwater ecosystems in China. The policy implications for the ecosystem-based water management contained in the results are discussed. The results obtained in this article provide a deeper understanding of the ecological risk characterization of the freshwater ecosystems in China, and aid in promoting the applications of the RRM as the tool for ecosystem-based water management.     

Looking down the microscope at the big picture – Interview with Michelle Casanova

Michelle Casanova is a widely published researcher specialising in the taxonomy of Australia's freshwater algae – as well as a rural landholder who understands the need for farmers to utilise the landscape. Michelle combines her work as a researcher with increasing involvement in management and policy through her region's Catchment Management Board and Victoria's Scientific Advisory Committee.     

Restoration and management of riparian ecosystems: a catchment perspective

1. We propose that strategies for the management of riparian ecosystems should incorporate concepts of landscape ecology and contemporary principles of restoration and conservation. A detailed understanding of the temporal and spatial dynamics of the catchment landscape (e.g. changes in the connectivity and functions of channel, riparian and terrestrial components) is critical. 2. This perspective is based upon previous definitions of riparian ecosystems, consideration of functional attributes at different spatial scales and retrospective analyses of anthropogenic influences on river catchments. 3. Restoration strategies must derive from a concise definition of the processes to be restored and conserved, recognition of social values and commitments, quantification of ecological circumstances and the quality of background information and determination of alternatives. 4. The basic components of an effective restoration project include: clear objectives (ecological and physical), baseline data and historical information (e.g. the hydrogeomorphic setting and the disturbance regime), a project design that recognizes functional attributes of biotic refugia, a comparison of plans and outcomes with reference ecosystems; a commitment to long-term planning, implementation and monitoring and, finally, a willingness to learn from both successes and failures. 5. Particularly important is a thorough understanding of past natural disturbances and human-induced changes on riparian functions and attributes, obtained by a historical reconstruction of the catchment.     

Colonisation of Introduced Timber by Algae and Invertebrates, and its Potential Role in Aquatic Ecosystem Restoration

As part of a habitat restoration experiment wood substrates (red gum) were introduced to two lowland streams of SE Australia in which habitat has been severely degraded by deposition of sand eroded from higher in the catchment. We monitored net primary production (NPP) and community respiration (CR), nutrient concentrations and the succession of algae and invertebrates (abundance and species richness), sampling at 2, 4, 8, 12, 16 and 20 weeks. Colonisation by algae was rapid, and there were distinct changes in the assemblages over the first 4 weeks. Thereafter, changes were much less marked. There were also differences in nutrient concentrations and some measures of algal abundance between the two creeks. As with the algae, invertebrates colonised these substrates extremely rapidly, peaking in abundance and richness in week 8. Invertebrate abundances closely tracked changes in the abundance of algae. By the end of the study both algal and invertebrate communities were in apparent decline, with sharp decreases in invertebrate and algal abundance and invertebrate species richness. Rates of GPP also declined toward the end of the experiment, and this coincided with the detachment of large mats of filamentous algae and the recession of flows over the summer months. However, in both streams the added timber quickly created habitat with high levels of primary production in an otherwise strongly heterotrophic stream system. These hotspots of autotrophic production were quickly colonised by high numbers of macroinvertebrates indicating timber addition may provide an effective means of augmenting habitat for algae and invertebrates in sanded streams.     

热带岩溶植物生理生态适应性对于南方石漠化土地生态重建的启示

岩溶地质在我国分布广泛,特别是西南地区连片分布着世界上面积最大的岩溶地貌.由于长期人为活动的影响,目前我国南方地区岩溶石漠化土地面积已达1.2×105 km2,导致当地生态条件恶化,经济、社会发展面临严重困难.南方岩溶山地土层薄,养分贫瘠,保水性能差.对热带岩溶森林开展了一系列生理生态研究,研究结果对南方岩溶石漠化山地生态重建有启发意义.研究结果暗示,岩溶生境常绿、落叶木本植物和木质藤本植物共存对于维持生态系统水分平衡有重要意义.常绿植物枝条木质部耐气穴化能力强,叶片耐失水性能强.落叶植物采取避旱策略,通过落叶减少旱季蒸腾和水分消耗.岩溶山地大部分植物具有很深的根系,藤本植物根系更深,旱季能利用地下深层岩石下和缝隙水.有些植物如木棉、董棕利用树干储存水保持旱季必要的生理代谢.岩溶山地木本植物叶片和枝条木质部结构和生理功能的密切关联对于适应水分胁迫起重要作用.热带岩溶植物可能普遍缺乏锌、钾元素,这方面问题需引起重视和研究.藤蔓植物可以利用石漠化岩溶山地局部水土资源和丰富的生长空间和光照资源,并且大多数藤蔓植物气孔调节能力强,对强光的适应和利用能力强,是石漠化山地生态重建的理想植物材料.目前中国科学院西双版纳植物园正在推广的一种珍贵的油料植物—星油藤,可以作为南方热区石漠化山地生态重建的理想植物材料.石漠化土地的重建要合理利用不同功能类群植物,特别是岩溶生境的乡土植物,最好构建多层复合群落.     

Implications of a Hierarchical Relationship Among Channel Form,Instream Habitat,and Stream Communities for Restoration of Channelized Streams

Hierarchy theory provides a conceptual framework for understanding the influence of differently scaled processes on the structure of stream communities. Channel form, instream habitat, and stream communities appear to be hierarchically related, but the strength of the relationships among all components of this hypothesized hierarchy have not been examined. We sampled channel form, instream habitat, fishes, and macroinvertebrates in a channelized stream in Mississippi and Alabama to examine the hypothesis that a hierarchical relationship exists among channel form, instream habitat, and stream communities. Instream habitat, fishes, and macroinvertebrates were sampled in May, July, and September 2000. Measurements of channel form were obtained in July 2000. Mantel tests, multiple regressions, and correlation analyses were used to assess strength of the relationships among channel form, instream habitat, and stream communities. Positive correlations were observed between channel form and instream habitat, and correlations observed between these factors were the greatest observed in our study. Overall, fish and macroinvertebrate communities exhibited stronger relationships with instream habitat than with channel form. Species richness, evenness, and abundance tended to exhibit greater correlations with instream habitat, while species composition had greater correlations with channel form. We concluded that channel form, instream habitat, and stream communities were hierarchically related.     

Ecological restoration of aquatic and semi-aquatic ecosystems in the Netherlands: an introduction*

Hydrobiologia - In 1989, a symposium was held under the title `Netherlands-Wetlands', aiming at the presentation of the state of the art of the existing knowledge of structure and functioning...     

Germination Requirement of Vallisneria natans Seeds: Implications for Restoration in Chinese Lakes

Due to eutrophication submerged macrophytes have disappeared from many Chinese lakes. This is unfortunate as submerged macrophytes are important to improve water quality, and its re-establishment is therefore desirable. For this purpose a potential method to use is re-seeding, this being particularly attractive due to the high seed productivity of V. natans. We conducted laboratory studies to investigate the effects of five environmental variables (temperature, substratum, oxygen, light availability, and burial depth) on the seed germination of V. natans. Our results showed that a wide temperature range (25–35 °C) was favorable for germination; that seeds germinated well under both gravel and silt; that anaerobic condition proved to accelerate seed germination although the final germination percentage did not rise; and that light and burial acted as limiting factors. These results suggest that V. natans is a potential candidate for successful restoration of vegetation in lakes recovering from eutrophication.     

Anthropogenic Habitats Facilitate Dispersal of an Early Successional Obligate: Implications for Restoration of an Endangered Ecosystem

Landscape modification and habitat fragmentation disrupt the connectivity of natural landscapes, with major consequences for biodiversity. Species that require patchily distributed habitats, such as those that specialize on early successional ecosystems, must disperse through a landscape matrix with unsuitable habitat types. We evaluated landscape effects on dispersal of an early successional obligate, the New England cottontail (Sylvilagus transitionalis). Using a landscape genetics approach, we identified barriers and facilitators of gene flow and connectivity corridors for a population of cottontails in the northeastern United States. We modeled dispersal in relation to landscape structure and composition and tested hypotheses about the influence of habitat fragmentation on gene flow. Anthropogenic and natural shrubland habitats facilitated gene flow, while the remainder of the matrix, particularly development and forest, impeded gene flow. The relative influence of matrix habitats differed between study areas in relation to a fragmentation gradient. Barrier features had higher explanatory power in the more fragmented site, while facilitating features were important in the less fragmented site. Landscape models that included a simultaneous barrier and facilitating effect of roads had higher explanatory power than models that considered either effect separately, supporting the hypothesis that roads act as both barriers and facilitators at all spatial scales. The inclusion of LiDAR-identified shrubland habitat improved the fit of our facilitator models. Corridor analyses using circuit and least cost path approaches revealed the importance of anthropogenic, linear features for restoring connectivity between the study areas. In fragmented landscapes, human-modified habitats may enhance functional connectivity by providing suitable dispersal conduits for early successional specialists.     

Implications of flexible foraging for interspecific interactions: lessons from simple models

1.  Some types of flexible foraging behaviours were incorporated into ecological thought in the 1960s, but the population dynamical consequences of such behaviours are still poorly understood.
2.  Flexible foraging-related traits can be classified as shifts in general and specific foraging effort, and shifts in general and specific defense.
3.  Many flexible foraging behaviours suggested by theory have received very little empirical attention, and empirical techniques used to compare the magnitudes of behavioural and non-behavioural responses to predation are likely to have overestimated the behavioural components.
4.  Adaptively flexible foraging in theory causes significant changes in the forms of consumer functional responses and generates a variety of indirect interactions. These can alter fundamental ecological processes, such as co-existence of competitors, and top-down or bottom-up effects in food webs.
5.  Many aspects of flexible foraging are still largely unknown, including the issues of how to represent the dynamics of such phenotypically plastic traits, how flexible traits in multiple species interact, what types of adaptive movements occur in metacommunities, and how adaptive behaviours influence evolutionary change.
6.  Population dynamics in large food webs may be less dependent on behavioural flexibility than in small webs because species replacement may preempt some potential types of behavioural change within species.     

Some Suggested Guidelines for Geomorphic Aspects of Anadromous Salmonid Habitat Restoration Proposals

Proposals to improve fish habitat for anadromous salmonids by modifying channel form or substrate must be justified based on geomorphology as well as biology, because geomorphic factors often cause such projects to fail. Proposals should address the geomorphic setting at the watershed scale, by specifying changes in flow regime or sediment yield through tools such as a sediment budget. Proposals should also address geomorphic setting and process at the reach scale, indicating the basis for design channel form and dimensions, calculating the frequency of bed mobilization, and assessing existing gravel quality for spawning habitat enhancement projects. Proposals should include explicit provisions for post‐project performance evaluation, including adequate baseline data to permit project‐induced changes to be quantified. Restoration projects also require clear objectives and adequate funding for long‐term monitoring, and generally would benefit from an adaptive management approach to implementation and evaluation.     

Spirodesmos milanai n. isp.: A Shallow-Water Spiral Trace Fossil from the Cambrian of the Eastern Cordillera,Northwest Argentina

Abstract

A new ichnofossiliferous locality in Salta Province (northwest Argentina) contains an association with numerous irregular spiral traces assigned to Spirodesmos milanai n. isp., in mature sandstones and quartzites with rippled bedding surfaces, rare wavy lamination and cross-bedded stratification. This record of early spiral behavior is interpreted as a primitive grazing method formed on muddy laminae above sand layers, and is related to a feeding strategy of an annelid-type of organism. Associated traces are Cruziana cf. semiplicata, Diplocraterion isp., Monocraterion isp., Rusophycus isp., Skolithos linearis Haldeman and Skolithos magnus Howell. The ichnoassemblage is similar to a shallow-water ichnoassociation from the Permian Ecca Group of South Africa (Mason et al., 1983 Mason, T. R., Stanistreet, I. G. and Tavener-Smith, R. 1983. Spiral trace fossils from the Permian Ecca Group of Zululand. Lethaia, 16: 241–247. [Crossref], [Web of Science ®] , [Google Scholar]).     

Ecological restoration in coastal areas in the Netherlands: concepts,dilemmas and some examples

This chapter gives an overview of attempts in the Netherlands to restore coastal ecosystems and habitats, and explains how scientific and non-scientific information has been used to meet the goals. Indications for successes and failures of management measures taken so far, as well as dilemmas to cope with, are given. Up to now only small scale restoration projects have been executed, while large scale projects generally are not further then the thinking or planning phase. A special type of `restoration projects' are the large civil engineering works, particularly in the south-west of the Netherlands. Although these works were not planned and executed as restoration projects, but designed for safety against flooding from the sea, they have led to significant changes in the boundary conditions of the systems concerned. For restoration projects yet to be executed one can learn very much from these developments, particularly regarding the sensitivity of coastal systems for changes in boundary conditions and about the (im)possibilities to `steer' ecological developments. Physical, chemical and biological processes form the basis of restoration measures of coastal habitats, and this means that a thorough knowledge of these processes is essential. Coastal ecosystems are the result of complex interactions of large-scale and small-scale processes, implying a holistic approach in scientific investigations. Consequently, restoration of these systems primarily has to be realised by influencing the basic processes. This is the only way to preserve or regain in a sustainable way ecological values, such as species composition. Focusing only at one particular species (e.g. breeding terns) or a specific habitat (e.g. a salt marsh) may easily ignore the underlying processes. In general, coastal restoration should focus on the redirection of processes towards a desired status by stimulating certain process parameters. Monitoring of the results and, if necessary, gradual readjustment of the governing factors, is an essential part of this approach.     

Ectoenzyme kinetics in Florida Bay: Implications for bacterial carbon source and nutrient status

Ectoenzyme kinetics [alkaline phosphatase, aminopeptidase (AM), lipase, α-glucosidase, and β-glucosidase] were determined over a seasonal cycle at four stations, Little Madeira Bay (northeast), Duck Key (east), Bob Allen Key (south-central), and Whipray Basin (north-central), which represent distinct regions of Florida Bay. Spatial and temporal variations in ectoenzyme kinetics were related to biotic and abiotic drivers in order to discern potential ectoenzyme substrate sources. Generally, ectoenzyme activities were higher in the central bay and lowest in the eastern bay. One pronounced exception was AM activity, which was highest at the mangrove fringe along the northeastern bay and reflected increased contribution of organic nitrogen inputs from upstream Everglades wetlands. When ectoenzymes were normalized to bacterial abundances, these trends dissipated and highest cell-specific activities were observed consistently in the south-central region. Relationships between ectoenzyme kinetics and environmental and biological parameters were complex, but three main spatially determined differences were discernable. Ectoenzyme kinetics were controlled by phosphorus availability in the eastern bay, by organic matter availability in the south-central bay, by microbial community composition and organic matter availability in northeastern bay (wetlands transition area), and by microbial community composition in the north-central bay. These differences in enzyme kinetics further support the hypothesis of distinct microbial communities in different regions of Florida Bay and provide insight into biogeochemical cycles and the microbial food web within Florida Bay.     

Measuring the Short‐term Success of Grassland Restoration: The Use of Habitat Affinity Indices in Ecological Restoration

Agricultural intensification threatens grasslands worldwide and the restoration of grasslands from arable lands can at least partially counter this threat. We studied grassland restoration by following early successional changes of arthropod assemblages (spiders, Araneae; true bugs, Heteroptera; orthopterans, Orthoptera; and ground beetles, Carabidae) on 1‐ and 2‐year‐old restorations using arable lands and native grasslands as two ends of the succession timescale. To examine the changes in species composition among the habitat types, we used habitat affinity indices based on fidelity and/or specificity of the species. We found that the number of species did not differ between habitat types, while species composition changed markedly with time. Species richness was thus not adequate to detect favorable changes after grassland restoration. Habitat affinity indices, on the other hand, were useful to detect compositional changes caused by the increasing numbers of species characteristic of target grasslands as early as the second year after restoration. Habitat affinity indices are easy‐to‐use, easy‐to‐interpret measures of restoration success; therefore, we recommend their use as measures complementary to species richness and simple similarity. Our results show that sowing low‐diversity seed mixture followed by mowing and grazing can be particularly successful in grassland restoration in time periods as short as 2 years.     

Evidence of a planktonic food web response to changes in nutrient input dynamics in the Mar Menor coastal lagoon,Spain

Nutrient input dynamics in the Mar Menor coastal lagoon has recently changed as a consequence of changes in agricultural practises. An interannual comparison of the environmental variables and the planktonic biomass size-spectra was performed between 1988 and 1997. While nitrate concentration was low in 1988, the values in 1997 increased considerably. Since 1995, two alloctonous jellyfish species (Rhyzostoma pulmo and Cotylorhiza tuberculata) occurred in large numbers in summer time and reached peak abundance in summer of 1997. The size-spectra analysis comparison revealed that, in spite of changes in nutrient input that stimulated the growth of larger phytoplankton cells, there were no significant differences in the spectra slope which followed a similar seasonal trend in both years. However, the plankton biovolume considered under the size range compared (between 2 and 1000 m diameter) was, paradoxically, always lower in 1997. Given that there were higher nutrient levels in 1997, this finding suggest a strong top-down control mechanism of size structure. Gut contents of jellyfishes showed their preference for large diatoms, tintinnids, veliger larvae and copepods, corroborating that size structure in these assemblages can be subject to top-down control. The implication of these results is that the feeding activities of large gelatinous zooplankton (jellyfishes) may play an important role controlling the consequences of eutrophication within the Mar Menor coastal lagoon.