Gradients in biodiversity and macroalgal wrack decomposition rate across a macrotidal, ultradissipative sandy beach

The decomposition process of, and the meiobenthic and nematode colonization on, stranded macroalgae were studied along a macrotidal, ultradissipative sandy beach gradient at De Panne (Belgium). The horizontal patterns of macro- and meiofaunal densities and diversity in this beach have been well-documented. Defaunated Fucus detritus was buried in situ in litter bags, 10–15 cm under the sediment surface, at seven stations across the beach profile. Colonization by (meio)fauna and organic matter decomposition rates measured as carbon, nitrogen, phosphorus and dry weight loss, were studied after 10, 21 and 52 days of incubation. Algal detritus was colonized mainly by nematodes dominated by Rhabditidae, Sabatieria, Dorylaimoidea, Monhystera, Paracanthonchus and Daptonema. Organic matter weight loss was slowest at the higher and lower shore and fastest in the mid-shore, in line with the horizontal pattern of nematode diversity in the beach sediment. However, there was no consistent relationship between nematode diversity inside the litter bags and organic matter weight loss, prohibiting an unequivocal conclusion on whether the observed parallel between extant nematode diversity and organic matter decomposition rate indicates a causal relationship or follows from the fact that both are governed by the same set of physicochemical conditions. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

The development of a sustainable urban district in Hammarby Sjöstad,Stockholm, Sweden?

By 2012, Hammarby Sjöstad, a former large industrial harbor area in southern Stockholm, Sweden, will be a fully developed residential district containing approximately 11,000 apartments and accommodating 35,000 people. The transformation of the area began in 1996, and the development soon became renowned for its ambitious environmental program, inspired by Agenda 21 (United Nations in Rio declaration on environment and development. United Nations Department of Economic and Social Affairs (DESA), Rio de Janeiro, 1992) and the Sydney 2000 Olympics in Australia (Newman in Landsc Urban Plan 44:219–226, 1999). Using results based on literature reviews, in-depth interviews, discussions with focus groups, and quantitative data, this paper attempts to gain insight into how the environmental program influenced the planning and performance of the district with regard to sustainable urban development. In doing so, three important conclusions were maintained that could be valuable for similar projects concerning the planning and development of sustainable urban districts. First, the environmental program proved vital to the development process of Hammarby Sjöstad, specifically in its drive to create a sustainable urban district. When planning on improving the sustainability of future districts, such a program should be introduced and integrated earlier in the planning stage of the district. Second, the metabolic flows of Hammarby Sjöstad were reduced as a result of the integrated system—the Hammarby Model—of Hammarby Sjöstad. In order to reduce the metabolic flows in future urban districts even further, it is important to facilitate the integration of technical innovations into existing integrated systems. Third, this case study showed that there was a loss of valid and credible data related to the aims and goals of the environmental program of Hammarby Sjöstad. In future urban districts, it is of the utmost importance to include a clear structure of the assessment process in the environmental program, which would ensure the quality of gathered data and facilitate the development of even better sustainable urban districts in the future.     

Declining coastal piscivore populations in the Baltic Sea: Where and when do sticklebacks matter?

Intraguild predation interactions make fish communities prone to exhibit alternative stable states with either piscivore or prey fish dominance. In the Baltic Sea, local declines of coastal piscivores like perch (Perca fluviatilis) have been observed to coincide with high densities of sticklebacks (Gasterosteus aculeatus). Mechanisms behind this shift between piscivore and stickleback dominance were studied both experimentally and in field. Results showed that predation by sticklebacks has a strong negative effect on perch larvae survival, but this effect rapidly decreases with increasing perch size, likely due to gape limitations and digestion constraints in sticklebacks. Large spatial and temporal variations in patterns of stickleback migration into perch spawning sites were observed. Whether or not high density of sticklebacks will cause declines in coastal piscivore populations is suggested to depend on the availability of spawning sites in which sticklebacks do not migrate into or arrive late in the reproduction season of coastal piscivores.     

Governing Climate Adaptation in the Local Arena: Challenges of Risk Management and Planning in Sweden

Abstract

This paper directs attention to conditions for climate adaptation as an important part of governing climate change in the local arena. Empirical focus is put on attempts to manage flood risks by means of risk management and planning in two Swedish municipalities. Following the need to widen our understanding of how, when and under what conditions climate adaptation occurs, three challenges are particularly emphasized from the case studies: facing the safety vs. scenery conflict where political priorities and reducing societal vulnerabilities prove difficult; the process of deciding what to adapt to, in which the troublesome role of knowledge is striking; and finally, taking responsibility for measures of flood protection. At the end of the paper, analytical generalizations illustrate the need to give increased attention to institutional challenges and challenges emanating from the science–policy interface in order to come to terms with the implementation deficit in governing climate change in the local arena.     

Spatiotemporal analysis of population genetic structure in <Emphasis Type="Italic">Geomonhystera disjuncta</Emphasis> (Nematoda,Monhysteridae) reveals high levels of molecular diversity

Species identification in the phylum Nematoda is complicated due to the paucity of easily obtainable diagnostic morphological features. Furthermore, the cosmopolitan distribution of several species despite low dispersal abilities makes cryptic diversity potentially substantial within this phylum. We conducted a population genetic survey in the marine nematode Geomonhystera disjuncta in Belgium and The Netherlands in two seasons. The mitochondrial cytochrome oxidase c subunit 1 (COI) gene was screened with the single-strand conformation polymorphism method in 759 individuals. The 43 haplotypes were grouped into five lineages, with low divergences within (<3%) and high divergences between lineages (>14%). Analysis of the nuclear ITS region yielded concordant tree topologies, indicating the presence of five cryptic taxa within G. disjuncta. Analysis of Molecular Variance (AMOVA) illustrated a significant structuring in all lineages and temporal fluctuations in haplotype frequencies within and between locations. Metapopulation dynamics and/or priority effects best explained this structuring. Finally, our data indicate that the COI gene may be useful for DNA barcoding purposes.     

Salinity effects on the coexistence of cryptic species: a case study on marine nematodes

The coexistence of four cryptic species of Rhabditis (Pellioditis) marina (Nematoda: Rhabditidae) at small geographical scale challenges ecological competition theory and was therefore studied in the laboratory at two different salinities, where their performance in combined cultures was compared with that in monospecies cultures. We found that three of the four cryptic species were able to coexist, but that interspecific interactions (competition and facilitation) were common. Salinity had an effect on these interactions, with a shift from contest to scramble competition. This shift may result from an increased population development of two of the four species at the lower salinity in the monospecific cultures. This experiment demonstrates that abiotic conditions may play an important role in achieving coexistence between cryptic species and can alter the interspecific interactions between them.     

Food and habitat choice in floating seaweed clumps: the obligate opportunistic nature of the associated macrofauna

The species composition of macrofauna associated with floating seaweed rafts is highly variable and influenced by many factors like spatial and temporal variation, period since detachment and probably also the seaweed species. The presence of seaweed preferences was assessed by a combination of in situ seaweed samplings and multiple-choice aquarium experiments in a controlled environment, using the seaweed-associated grazing organisms Idotea baltica and Gammarus crinicornis. Results from the sampling data confirm that the seaweed composition influences macrofaunal species composition and abundance: samples dominated by Sargassum muticum displayed higher densities but lower diversities compared to samples dominated by Ascophyllum nodosum and Fucus vesiculosus. Seaweed preference was also apparent from the multiple-choice experiments, but did not exactly match the results of the community analysis: (1) I. baltica had high densities in seaweed samples (SWS) dominated by F. vesiculosus and A. nodosum, while in the experiments, this isopod was most frequently associated with Enteromorpha sp. and F. vesiculosus, and fed mostly on S. muticum, A. nodosum and Enteromorpha sp.; (2) G. crinicornis had high densities in SWS dominated by F. vesiculosus, while in the experiments, this amphipod was most frequently associated with S. muticum, but fed most on A. nodosum and F. vesiculosus. It is clear from the laboratory experiments that preference for habitat (shelter) and food can differ among seaweed species. However, food and habitat preferences are hard to assess because grazer preference may change if choices are increased or decreased, if different sizes of grazers are used, or if predators or other grazers are added to the experiments. The effects of seaweed composition may also be blurred due to the obligate opportunistic nature of a lot of the associated macrofaunal species.     

Habitat type determines herbivory controls over CO2 fluxes in a warmer Arctic

High-latitude ecosystems store large amounts of carbon (C); however, the C storage of these ecosystems is under threat from both climate warming and increased levels of herbivory. In this study we examined the combined role of herbivores and climate warming as drivers of CO2 fluxes in two typical high-latitude habitats (mesic heath and wet meadow). We hypothesized that both herbivory and climate warming would reduce the C sink strength of Arctic tundra through their combined effects on plant biomass and gross ecosystem photosynthesis and on decomposition rates and the abiotic environment. To test this hypothesis we employed experimental warming (via International Tundra Experiment [ITEX] chambers) and grazing (via captive Barnacle Geese) in a three-year factorial field experiment. Ecosystem CO2 fluxes (net ecosystem exchange of CO2, ecosystem respiration, and gross ecosystem photosynthesis) were measured in all treatments at varying intensity over the three growing seasons to capture the impact of the treatments on a range of temporal scales (diurnal, seasonal, and interannual). Grazing and warming treatments had markedly different effects on CO2 fluxes in the two tundra habitats. Grazing caused a strong reduction in CO2 assimilation in the wet meadow, while warming reduced CO2 efflux from the mesic heath. Treatment effects on net ecosystem exchange largely derived from the modification of gross ecosystem photosynthesis rather than ecosystem respiration. In this study we have demonstrated that on the habitat scale, grazing by geese is a strong driver of net ecosystem exchange of CO2, with the potential to reduce the CO2 sink strength of Arctic ecosystems. Our results highlight that the large reduction in plant biomass due to goose grazing in the Arctic noted in several studies can alter the C balance of wet tundra ecosystems. We conclude that herbivory will modulate direct climate warming responses of Arctic tundra with implications for the ecosystem C balance; however, the magnitude and direction of the response will be habitat-specific.     

Land cover changes as impacted by spatio-temporal rainfall variability along the Ethiopian Rift Valley escarpment

Magnitudes of land cover changes nowadays can be assessed properly, but their driving forces are subject to many discussions. Next to the accepted role of human influence, the impact of natural climate variability is often neglected. In this paper, the impact of rainfall variability on land cover changes (LCC) is investigated for the western escarpment of the Raya Graben along the northern Ethiopian Rift Valley. First, LCC between 2000 and 2014 were analysed at specific time steps using Landsat imagery. Based on the obtained LCC maps, the link was set with rainfall variability, obtained by means of the satellite-derived rainfall estimates (RFEs) from NOAA-CPC. After a correction by the incorporation of local meteorological station data, these estimates prove to be good estimators for the actual amount of precipitation (ρ _RFE1.0 = 0.85, p = 0.00, n = 126; ρ _RFE2.0 = 0.76, p = 0.00, n = 934). By performing several linear regression analyses, a significant positive relationship between the precipitation parameter DIFF 5Y (i.e. the at-RFE pixel scale difference in five-year average annual precipitation for the two periods preceding the land cover maps) and the changes in the woody vegetation cover was found (standardised regression coefficient β = 0.23, p = 0.02, n = 108). Despite the dominance of direct human impact, further greening of the study area can be expected for the future concomitantly to a wetter climate, if all other factors remain constant.