Relationship between biochemical biomarkers and pre-copulatory behaviour and mortality in Gammarus pulex following pulse-exposure to lambda-cyhalothrin

The impact of the pyrethroid lambda-cyhalothrin was studied in an in-stream mesocosm placed in a natural riffle of a Danish stream. Twice during summer 2002, the natural macroinvertebrate community was exposed in situ to a 30-min pulse of lambda-cyhalothrin. During exposure, nets caught macroinvertebrates in drift. Exposed and unexposed individuals of the amphipod Gammarus pulex (L) were transferred to aquaria in the laboratory and monitored for biochemical changes (ie biomarkers), pre-copulatory behaviour and mortality. Biochemical biomarkers were identified by screening extracts of exposed and unexposed G pulex using high-performance planar chromatography (HPPC). Biochemical biomarkers were detected 3 h after pulse-exposure, and one biomarker was persistent up to 7 days after exposure. Pre-copulatory behaviour (ie pair formation) was significantly impaired up to 5 days after exposure, and had not fully recovered at the end of the observation period. EC10(0.5 h) and EC50(0.5 h) values for pre-copulatory behaviour were 0.04 and 0.20 microg litre(-1), respectively. Mortality was significant at 0.35 microg litre(-1) with an LC50(0.5 h) of 5.69 microg litre(-1). There was a significant relationship between two biomarkers and mortality. The study demonstrated that pulse-exposure at expected environmental concentrations can reduce local populations of G pulex, resulting in severe impact on populations with limited possibilities of re-colonisation.     

Unraveling the chemical composition of caramel

Caramel is one of mankind's best known dietary materials obtained from carbohydrates by heating. Much effort has been expended toward the chemical characterization of the components of caramel but impeded by a lack of suitable analytical techniques sufficiently powerful for providing insight into an extraordinarily complex material. This paper reports the characterization of caramel formed by heating from glucose, fructose, and saccharose using a conceptually novel combination of mass spectrometrical techniques. The analytical strategy employed uses high-resolution mass spectrometry (MS) followed by targeted liquid chromatography-tandem MS experiments. Caramel is composed from several thousand compounds formed by a small number of unselective and chemoselective reactions. Caramelization products include oligomers with up to six carbohydrate units formed through unselective glycosidic bond formation, dehydration products of oligomers losing up to a maximum of eight water molecules, hydration products of sugar oligomers, disproportionation products, and colored aromatic products.     

Recreational sector is the dominant source of fishing mortality for oceanic fishes in the Southeast United States Atlantic Ocean

Recreational fishing is increasingly recognised as an important source of mortality for marine fish populations. In the United States, estimates of marine recreational catch and effort were recently revised for the time period 1981 and beyond, and for many species, the revised estimates were substantially higher than the original values. Here, the proportion of total landings that came from the recreational sector in the Southeast US Atlantic was quantified. The proportions for 22 oceanic species and for all species combined were computed, using a full time series of landings (1981–2016) and a more recent time series (1999–2016). For the full and recent time series, landings of most species (15/22 and 17/22, respectively) were dominated by the recreational sector. For all species combined, 71% of landings in the full time series were from the recreational sector, and 76% in the recent time series. Trend analysis indicated that most species had a stable or increasing proportion of landings from the recreational sector. In addition, stock assessments were conducted on four species, and the catch revisions increased the estimated scale of abundance and, in some cases, affected stock or fishery status. This work underscores the importance of recreational fishing for marine resource management.     

Microbial reefs in the Black Sea fueled by anaerobic oxidation of methane

Massive microbial mats covering up to 4-meter-high carbonate buildups prosper at methane seeps in anoxic waters of the northwestern Black Sea shelf. Strong 13C depletions indicate an incorporation of methane carbon into carbonates, bulk biomass, and specific lipids. The mats mainly consist of densely aggregated archaea (phylogenetic ANME-1 cluster) and sulfate-reducing bacteria (Desulfosarcina/Desulfococcus group). If incubated in vitro, these mats perform anaerobic oxidation of methane coupled to sulfate reduction. Obviously, anaerobic microbial consortia can generate both carbonate precipitation and substantial biomass accumulation, which has implications for our understanding of carbon cycling during earlier periods of Earth's history.     

Using airborne LiDAR to assess spatial heterogeneity in forest structure on Mount Kilimanjaro

Context

Field inventory plots which usually have small sizes of around 0.25–1 ha can only represent a sample of the much larger surrounding forest landscape. Based on airborne laser scanning (LiDAR) it has been shown for tropical forests that the bias in the selection of small field plots may hamper the extrapolation of structural forest attributes to larger spatial scales.

Objectives

We conducted a LiDAR study on tropical montane forest and evaluated the representativeness of chosen inventory plots with respect to key structural attributes.

Methods

We used six forest inventory and their surrounding landscape plots on Mount Kilimanjaro in Tanzania and analyzed the similarities for mean top-of-canopy height (TCH), aboveground biomass (AGB), gap fraction, and leaf-area index (LAI). We also analyzed the similarity in gap-size frequencies for the landscape plots.

Results

Mean biases between inventory and landscape plots were large reaching as much as 77% for gap fraction, 22% for LAI or 15% for AGB. Despite spatial heterogeneity of the landscape, gap-size frequency distributions were remarkably similar between the landscape plots.

Conclusions

The study indicates that biases in field studies of forest structure may be strong. Even when mean values were similar between inventory and landscape plots, the mostly non-normally distributed probability densities of the forest variable indicated a considerable sampling error of the small field plot to approximate the forest variable in the surrounding landscape. This poses difficulties for the spatial extrapolation of forest structural attributes and for assessing biomass or carbon fluxes at larger regional scales.

     

Effect of Grazing-Mediated Dimethyl Sulfide (DMS) Production on the Swimming Behavior of the Copepod Calanus helgolandicus

Chemical interactions play a fundamental role in the ecology of marine foodwebs. Dimethyl sulfide (DMS) is a ubiquitous marine trace gas that acts as a bioactive compound by eliciting foraging behavior in a range of marine taxa including the copepod Temora longicornis. Production of DMS can rapidly increase following microzooplankton grazing on phytoplankton. Here, we investigated whether grazing-induced DMS elicits an increase in foraging behavior in the copepod Calanus helgolandicus. We developed a semi-automated method to quantify the effect of grazing-mediated DMS on the proportion of the time budget tethered females allocate towards slow swimming, typically associated with feeding. The pooled data showed no differences in the proportion of the 25 min time budget allocated towards slow swimming between high (23.6 ± 9.74%) and low (29.1 ± 18.33%) DMS treatments. However, there was a high degree of variability between behavioral responses of individual copepods. We discuss the need for more detailed species-specific studies of individual level responses of copepods to chemical signals at different spatial scales to improve our understanding of chemical interactions between copepods and their prey.     

Characterization by LC-MS(n) of four new classes of p-coumaric acid-containing diacyl chlorogenic acids in green coffee beans

LC-MS4 has been used to detect and characterize in green coffee beans 15 quantitatively minor p-coumaric acid-containing chlorogenic acids not previously reported in nature. These comprise 3,4-di-p-coumaroylquinic acid, 3,5-di-p-coumaroylquinic acid, and 4,5-di-p-coumaroylquinic acid (Mr 484); 3-p-coumaroyl-4-caffeoylquinic acid, 3-p-coumaroyl-5-caffeoylquinic acid, 4-p-coumaroyl-5-caffeoylquinic acid, 3-caffeoyl-4-p-coumaroyl-quinic acid, 3-caffeoyl-5-p-coumaroyl-quinic acid; and 4-caffeoyl-5-p-coumaroyl-quinic acid (Mr 500); 3-p-coumaroyl-4-feruloylquinic acid, 3-p-coumaroyl-5-feruloylquinic acid and 4-p-coumaroyl-5-feruloylquinic acid (Mr 514); and 4-dimethoxycinnamoyl-5-p-coumaroylquinic acid and two isomers (Mr 528) for which identities could not be assigned unequivocally. Structures have been assigned on the basis of LC-MS4 patterns of fragmentation. Forty-five chlorogenic acids have now been characterized in green Robusta coffee beans.     

Forest fires and vegetation during the Holocene in central Yakutia, eastern Siberia

In order to investigate the relationship between vegetation change and fire history in the Siberian boreal forest, fossil pollen and charcoal from two lakes in central Yakutia, eastern Siberia, were analyzed. The vegetation change inferred from the pollen analysis was similar to that found in previous research in the region. Open larch forest covered this region during the late Glacial and early Holocene periods. Later, during the mid-Holocene, Scots pine expanded its range. The low levels of charcoal in the lake deposits represent surface forest fires, suggesting that the present-day surface fire regime has been taking place since at least 6,500 calibrated years before the present (cal yr BP) and that stand-replacing fire has not occurred during the Holocene. Larch and Scots pine forests, which are characterized by surface fire regimes, have been predominant since the early Holocene.