A chemical and toxicological profile of Dutch North Sea surface sediments

Chemical and toxicological profiles were assessed in surface sediments (fraction <63 μm) from the southern North Sea. In extracts of freeze-dried samples, polybrominated biphenyl (PBB), Irgarol 1051 and phthalate concentrations were below the respective detection limits (except di(2-ethylhexyl)phthalate, which was between 170 and 3300 μg kg⁻¹ dry weight (dw)). Hexabromocyclododecane (HBCD) concentrations were between 0.8 and 6.9 μg kg⁻¹ dw, with highest concentrations at river mouths. Polybrominated diphenylethers (PBDE) concentrations were 0.4–0.6 μg kg⁻¹ dw, decabromodiphenylether (BDE209) 1–32 μg kg⁻¹ dw. The ratio BDE209/PCB153 was used as a tracer for recent emissions, and pointed towards a BDE209 source in the Western Scheldt’s upper estuary. PCBs and PAHs were between 0.19–4.7 and 2.6–200 μg kg⁻¹ dw respectively and generally had highest concentrations at near-shore locations and river mouths.

Responses in the Microtox broad-spectrum and the Mutatox genotoxicity assays were generally low, with near-shore locations giving higher responses. The umu-C genotoxicity and the ER-CALUX assay for estrogenicity showed no response, with the exception of one near-shore location (IJmuiden outer harbour, ER-CALUX).

Highest dioxin-like toxicity (DR-CALUX) was found at near-shore locations, in the outflow of the Rhine/Meuse estuary including a dumping site of harbour sludge. At the Oyster Grounds, DR-CALUX responses appeared to be linked to the occurrence of larger PAHs (4–6 rings). A new, non-destructive clean up procedure resulted in significantly higher DR-CALUX responses than the current protocol. The Dutch legislation on disposal of harbour sludge at sea, dictates the use of the conventional clean up procedure. Our results therefore indicate that probably more dioxin-like toxicity associated with harbour sludge is disposed off at sea than assumed.     

Mitigation of a radon-rich Belgian dwelling using active subslab depressurization

In a radon prone area in Belgium, a dwelling with high indoor radon concentrations was identified through a passive measurement. Next, a continuous, active radon monitoring device was installed for one month. A 20-a retrospective radon assessment was also performed. The house was subsequently mitigated through active subslab depressurization with a radial fan. Afterwards the dwelling was actively monitored for several more months to observe the effects of the mitigation and to study the effect of reducing the fan power. Dose evaluations were made to evaluate the health benefit of the mitigation. It was seen that the results of the three measuring techniques before mitigation all yielded between 1700 and 2000 Bq/m3. Clear diurnal radon variations showed up only after mitigation. After mitigation, the average radon concentration fell to less than 200 Bq/m3. The yearly average dose was reduced from potentially 45 mSv/y to less than 4.5 mSv/y through mitigation. Reducing fan power to 50% did not clearly influence the amount of radon entering into the dwelling.     

Pre-dispersal seed predation: the role of fruit abortion and selective oviposition

Oviposition sites of phytophagous insects should correlate with plant traits that maximize survival of the progeny. Plants, on the other hand, should benefit from traits and developmental patterns that complicate oviposition decisions. In the antagonistic interaction between plant and pre-dispersal seed predator the time lag between egg laying and seed development may allow for abortion of fruits in plants, potentially reducing fitness loss through predation. We studied the perennial herb Lathvrus vernus and the beetle pre-dispersal seed predator Bruchus atomarius in Sweden to determine the fitness consequences of nonrandom fruit abortion in the plant and oviposition patterns of the beetle. The beetle had a sophisticated ability to locate fruits with high probability of retention, partly by fruit position and phenology but also by some additional unidentified cue. Mortality of eggs was density dependent, but still the egg-laying pattern was clumped. We found no defensive strategy in the plant; instead the predictable fruit abortion pattern was associated with decreased plant fitness. We discuss how interactions may pose simultaneous selection pressures on plant and insect traits and how life history traits and other selective forces may shape the adaptive outcome of the interaction in plant and insect, respectively.     

Change in spring arrival of migratory birds under an era of climate change,Swedish data from the last 140 years

Many migratory bird species have advanced their spring arrival during the latest decades, most probably due to climate change. However, studies on migratory phenology in the period before recent global warming are scarce. We have analyzed a historical dataset (1873–1917) of spring arrival to southern and central Sweden of 14 migratory bird species. In addition, we have used relative differences between historical and present-day observations (1984–2013) to evaluate the effect of latitude and migratory strategy on day of arrival over time. There was a larger change in spring phenology in short-distance migrants than in long-distance migrants. Interestingly, the results further suggest that climate change has affected the phenology of short-distance migrants more in southern than in central Sweden. The results suggest that the much earlier calculated arrival to southern Sweden among short-distance migrants mirrors a change in location of wintering areas, hence, connecting migration phenology and wintering range shifts.     

Scaling-up spatially-explicit ecological models using graphics processors

How the properties of ecosystems relate to spatial scale is a prominent topic in current ecosystem research. Despite this, spatially explicit models typically include only a limited range of spatial scales, mostly because of computing limitations. Here, we describe the use of graphics processors to efficiently solve spatially explicit ecological models at large spatial scale using the CUDA language extension. We explain this technique by implementing three classical models of spatial self-organization in ecology: a spiral-wave forming predator-prey model, a model of pattern formation in arid vegetation, and a model of disturbance in mussel beds on rocky shores. Using these models, we show that the solutions of models on large spatial grids can be obtained on graphics processors with up to two orders of magnitude reduction in simulation time relative to normal pc processors. This allows for efficient simulation of very large spatial grids, which is crucial for, for instance, the study of the effect of spatial heterogeneity on the formation of self-organized spatial patterns, thereby facilitating the comparison between theoretical results and empirical data. Finally, we show that large-scale spatial simulations are preferable over repetitions at smaller spatial scales in identifying the presence of scaling relations in spatially self-organized ecosystems. Hence, the study of scaling laws in ecology may benefit significantly from implementation of ecological models on graphics processors.     

Factors affecting male yearly mating success in the common frog,Rana temporaria

Summary The mating behavior of the European common frog, Rana temporaria, was studied experimentally. Female body length was correlated with body mass as well as with fecundity. However, males showed no mating preference with regard to either female body length, body mass, or fecundity. In successive multiple matings, male readiness to re-mate as well as fertilization success did not vary among the first four matings. Further, fertilization success was not correlated with either the number of days since the previous fertilization, water volume in the experimental container, testes mass, female/male body length ratio, or female fecundity. However, there was a positive correlation between fertilization success and male fat reserve status. Sexual competition and mating patterns were studied in tanks in which operational sex ratio (OSR) and male density were manipulated, and time for sexual competition was allowed to vary. Successful take-overs and nonrandom mating (large male advantage) were observed only at a combination of a four-fold male bias in OSR and an unnaturally high male density (30–50/m²). I argue that in natural populations of Rana temporaria: (1) There is considerable intraspecific variation in the opportunity for sexual competition, (2) OSR influences mating pattern more than male density and time (duration of the prespawning period), and (3) nonrandom mating should be rare.