Effects of seawater pCO2 and temperature on shell growth, shell stability, condition and cellular stress of Western Baltic Sea Mytilus edulis (L.) and Arctica islandica (L.)

Acidification of the World’s oceans may directly impact reproduction, performance and shell formation of marine calcifying organisms. In addition, since shell production is costly and stress in general draws on an organism’s energy budget, shell growth and stability of bivalves should indirectly be affected by environmental stress. The aim of this study was to investigate whether a combination of warming and acidification leads to increased physiological stress (lipofuscin accumulation and mortality) and affects the performance [shell growth, shell breaking force, condition index (C_i)] of young Mytilus edulis and Arctica islandica from the Baltic Sea. We cultured the bivalves in a fully-crossed 2-factorial experimental setup (seawater (sw) pCO₂ levels “low”, “medium” and “high” for both species, temperature levels 7.5, 10, 16, 20 and 25 °C for M. edulis and 7.5, 10 and 16 °C for A. islandica) for 13 weeks in summer. Mytilus edulis and A. islandica appeared to tolerate wide ranges of sw temperature and pCO₂. Lipofuscin accumulation of M. edulis increased with temperature while the C_i decreased, but shell growth of the mussels only sharply decreased while its mortality increased between 20 and 25 °C. In A. islandica, lipofuscin accumulation increased with temperature, whereas the C_i, shell growth and shell breaking force decreased. The pCO₂ treatment had only marginal effects on the measured parameters of both bivalve species. Shell growth of both bivalve species was not impaired by under-saturation of the sea water with respect to aragonite and calcite. Furthermore, independently of water temperatures shell breaking force of both species and shell growth of A. islandica remained unaffected by the applied elevated sw pCO₂ for several months. Only at the highest temperature (25 °C), growth arrest of M. edulis was recorded at the high sw pCO₂ treatment and the C_i of M. edulis was slightly higher at the medium sw pCO₂ treatment than at the low and high sw pCO₂ treatments. The only effect of elevated sw pCO₂ on A. islandica was an increase in lipofuscin accumulation at the high sw pCO₂ treatment compared to the medium sw pCO₂ treatment. Our results show that, despite this robustness, growth of both M. edulis and A. islandica can be reduced if sw temperatures remain high for several weeks in summer. As large body size constitutes an escape from crab and sea star predation, this can make bivalves presumably more vulnerable to predation—with possible negative consequences on population growth. In M. edulis, but not in A. islandica, this effect is amplified by elevated sw pCO₂. We follow that combined effects of elevated sw pCO₂ and ocean warming might cause shifts in future Western Baltic Sea community structures and ecosystem services; however, only if predators or other interacting species do not suffer as strong from these stressors.     

有机和常规生产系统中甜瓜氮素吸收差异分析

在甜瓜有机生产系统中,设置3个有机肥料水平处理,即空白(OZ)、半量施肥(OH)和标准施肥(OS),在常规生产系统中设置两个化肥水平处理.即空白(CZ)和正常施肥(CS),以研究有机和常规两种土壤中速效氮的变化及甜瓜对氮素的吸收规律.结果表明,在甜瓜的生长发育过程中,有机肥料向土壤中提供了与常规处理相同水平的速效氮.两种生产系统中甜瓜的生物量和产量差异不显著,且不受施肥水平的影响.甜瓜植株的氮素含量在生育过程中逐渐降低,氮素吸收量逐渐增加,常规处理显著高于有机处理,生产系统内部不同的施肥水平之间差异不显著.常规处理中甜瓜的氮素吸收速率显著高于有机处理,同时植株体内积累了较多的硝态氮从而降低了氮素利用效率.图4表4参22     

Aggregations and offshore movements as indicators of spawning activity of bonefish (Albula vulpes) in The Bahamas

To identify the timing and location of spawning activity for bonefish (Albula spp.) in the Bahamian archipelago, we used an acoustic telemetry array spanning 44?km² of shallow tidal creeks, flats, and adjacent deeper coastal waters near Cape Eleuthera. In two successive years, we surgically implanted transmitters in male and female bonefish (n?=?60) and examined their movement patterns within the array. Eight bonefish surgically implanted with transmitters as part of an earlier study were also tracked. In 2009, the telemetry information was complemented with snorkeling observations, underwater video, and manual tracking of the same acoustically tagged fish, as well as fish (n?=?3) gastrically implanted with continuous transmitters. During a period of 4?C7?days spanning the full and new moons, primarily between October and May, bonefish moved from their typical shallow flats and aggregated at sites in close proximity to the deep water drop-off of the Exuma Sound. Localized movements of the large schools of bonefish (often?>1,000 fish) at these presumptive pre-spawning aggregation sites included brief trips (<8?h) just after sunset until just prior to sunrise to the abyssal wall at the edge of the Exuma Sound (i.e.,?>1,000?m depth). Tagged bonefish detected at these aggregation sites were subsequently detected back in the tidal creeks and coastal flats shortly after new and full moons and remained at these more typical shallow sites (i.e.,?<2?m depth). Although we did not directly observe spawning events, we did observe ventral nudging and porpoising behaviors, which are potentially associated with courtship. Timing of the observed movements and possible courtship behaviors was coincident with periods when gametes were well developed. Collectively, our study provides the first objective evidence suggesting that the aggregation and seasonal migration of bonefish to deep shelf environments during certain moon phases is for spawning.     

Effects of male sexual harassment on female time budgets,feeding behavior,and metabolic rates in a tropical livebearing fish (<Emphasis Type="Italic">Poecilia mexicana</Emphasis>)

Sexual harassment by males has the potential to affect almost any aspect of female behavior and life history. Using Atlantic mollies (Poecilia mexicana) as a model—a species in which males do not court but almost constantly try to forcefully mate with females—we asked whether and how male harassment influences (a) females’ time budgets and (b) feeding rates (e.g., through frequent flight from male approaches), and (c) whether metabolic rates are increased as a response to stress. Field observations in a natural P. mexicana population revealed that males (average feeding rate 15%) spent far less time feeding than females (60%), and clearly traded off frequent pursuit of females with foraging. Most importantly, females’ feeding times were dramatically reduced when being pursued by a harassing male. Also in standardized lab experiments, females spent significantly less time feeding when accompanied by a male as compared to being in the presence of another female. This effect was also observed when partner fish (male or female) were presented only visually, but could not interact physically with the focal female. It seems, therefore, that females increase vigilance when a harassing male is around, which keeps them from feeding even before males actually approach them. Based on the latter result, we asked whether a stress-induced increase in metabolic rates would be discernible. We measured oxygen consumption and gill ventilation frequencies (opercular rates) of females in different social contexts (alone, with another female, or a male). The predicted, strong body mass dependency of both physiological parameters was uncovered, but no evidence for an effect of social context was detected. We argue that male harassment represents such a constant (but non-lethal) stressor for poeciliid females that their metabolic stress responses have adapted to this through habituation.     

Transnational multistakeholder partnerships for sustainable development: Conditions for success

This perspective discusses nine conditions for enhancing the performance of multistakeholder partnerships for sustainable development. Such partnerships have become mainstream implementation mechanisms for attaining international sustainable development goals and are also frequently used in other adjacent policy domains such as climate change, health and biodiversity. While multistakeholder arrangements are widely perceived as a positive contribution to addressing global change, few studies have systematically evaluated the existing evidence for their positive performance. This poses an urgent and important challenge for researchers and practitioners to understand and improve the effectiveness of partnerships, in particular since their popularity increases despite their past track record. The recommendations presented are based on own research, a literature survey and discussions with a large number or international Civil Society Organizations at two occasions during 2014. This article proceeds as follows: first, we define multistakeholder partnerships, outline their rational and summarize available assessments on partnership success; second, we provide a set of concrete recommendations based on lessons-learned from over 10 years of scholarship; and third, we conclude with some reflections on the future of multistakeholder governance for sustainability.     

Challenges and opportunities of power systems from smart homes to super-grids

The world’s power systems are facing a structural change including liberalization of markets and integration of renewable energy sources. This paper describes the challenges that lie ahead in this process and points out avenues for overcoming different problems at different scopes, ranging from individual homes to international super-grids. We apply energy system models at those different scopes and find a trade-off between technical and social complexity. Small-scale systems would require technological breakthroughs, especially for storage, but individual agents can and do already start to build and operate such systems. In contrast, large-scale systems could potentially be more efficient from a techno-economic point of view. However, new political frameworks are required that enable long-term cooperation among sovereign entities through mutual trust. Which scope first achieves its breakthrough is not clear yet.     

What do we really know about the impacts of one of the 100 worst invaders in Europe? A reality check

Invasive species are one of the greatest threats to biodiversity worldwide, and to successfully manage their introductions is a major challenge for society. Knowledge on the impacts of an invasive species is essential for motivating decision makers and optimally allocating management resources. We use a prominent invasive fish species, the round goby (Neogobius melanostomus) to objectively quantify the state of scientific knowledge on its impacts. Focusing on how native fish species are affected by round goby invasions, we analyzed 113 peer-reviewed papers and found that impacts are highly ecosystem and time scale dependent. We discovered round goby impacts to be profound, but surprisingly complex. Even if identical native species were affected, the impacts remained less comparable across ecosystems than expected. Acknowledging the breadth but also limitations in scientific knowledge on round goby impacts would greatly improve scientists’ ability to conduct further research and inform management measures.

Electronic supplementary material

The online version of this article (doi:10.1007/s13280-015-0718-9) contains supplementary material, which is available to authorized users.