Identification and distribution of intact polar branched tetraether lipids in peat and soil

Branched glycerol dialkyl glycerol tetraether lipids (GDGTs) are membrane lipids of soil bacteria that occur ubiquitously in soil, but their occurrence as intact polar lipids (IPLs) has not been well studied. Here, we report the identification and distribution of IPL-branched GDGTs throughout a depth profile of a Swedish peat bog. In addition to two reported glycosidic IPL branched GDGTs, we identified IPL branched GDGTs with a hexose-glycuronic acid, phospho-hexose, or hexose-phosphoglycerol head group, based on mass spectrometry. A selected reaction monitoring (SRM) assay was developed to monitor changes in head group distribution with depth. The abundance of the IPL branched GDGTs increased below the water table, suggesting that they were primarily produced in this part of the peat. This was supported by the concentrations of core lipid and IPL-derived branched GDGTs, which also substantially increased below the water table. However, individual IPL trends differed, which may be due to changes in the microbial community composition with depth or to different degradation rates for the different IPL branched GDGTs. The SRM method was also applied to two different soil types, which showed that similar IPL branched GDGTs as those in peat were present, albeit with different distributions.     

Source-specific variability in post-depositional DNA preservation with potential implications for DNA based paleoecological records

Recent studies have shown that genotyping preserved plankton DNA in marine and lacustrine sediment records using ancient DNA methods is a promising approach for refining paleoenvironmental information. However, the extent to which the preservation of fossil plankton DNA differs between species is poorly understood. Using a continuous 2700 year sediment record from Watts Basin in Ellis Fjord (Antarctica), we compared the level of preservation of fossil DNA derived from important plankton members with varying cellular architecture. The amount of preserved small subunit ribosomal DNA (SSU rDNA; ca. 500 base pair fragments) of dinoflagellates (as extracellular DNA rather than as preserved cysts) that could be amplified by way of PCR declined up to five orders of magnitude with increasing sediment depth and age. In contrast, the amount of similar-sized, PCR-amplifiable, diatom SSU rDNA (predominantly from a cyst-forming Chaetoceros sp.) declined only up to tenfold over 2700 years of deposition. No obvious decline in copy numbers with increasing sediment age was observed for similar-sized SSU rDNA of past chemocline-associated photosynthetic green sulfur bacteria (GSB), which do not have a protective resting stage. In good agreement with the quantitative data, the extent of post-depositional natural degradation to fragments too small to serve as a template for the quantitative PCR assays was greatest for dinoflagellates and lowest for GSB. An increase in the ratio between GSB-derived DNA and intact carotenoids with sediment depth implies that short GSB DNA fragments were better preserved than intact carotenoids and provide a more accurate view into paleoproductivity and the sediment flux of GSB in Watts Basin. We discuss the possible causes behind the variation in the level of DNA preservation among the plankton groups investigated, as well as consequences for the use of using fossil DNA records in paleoecology studies.     

Differences in the neighborhood: Structural variations in the carapace of shore crabs Carcinus maenas (Decapoda: Portunidae)

The present study compared the carapace structure of Carcinus maenas in two nearby sites (2 km apart) within Minho estuary, submitted to different physicochemical and ecological conditions (water temperature, pH, crabs’ density and sex ratio). The carapace structure of the carapace and chelae of the crabs presented significant differences between sampling sites (t-test; p < 0.01). The SIMPER analysis revealed that the Weight/CW and Thickness/CW ratios explained all the dissimilarities found among sites. Overall, the male carapace was proportionally thicker at station 2 (t-test; p < 0.01), while the female carapace was proportionally thicker at station 1 (t-test; p < 0.001). A thicker carapace can be advantageous when competing for food or a sexual partner. We hypothetized that, since at station 2, the density of individuals was twice higher than at station 1, it is likely that agonistic encounters are more frequent, thus favouring a thicker carapace.     

Harmful algal blooms and eutrophication: ��strategies�� for nutrient uptake and growth outside the Redfield comfort zone

While many harmful algal blooms have been associated with increasing eutrophication, not all species respond similarly and the increasing challenge, especially for resource managers, is to determine which blooms are related to eutrophication and to understand why particular species proliferate under specific nutrient conditions. The overall goal of this brief review is to describe why nutrient loads are not changing in stoichiometric proportion to the "Redfield ratio", and why this has important consequences for algal growth. Many types of harmful algae appear to be able to thrive, and/or increase their production of toxins, when nutrient loads are not in proportion classically identified as Redfield ratios. Here we also describe some of the physiological mechanisms of different species to take up nutrients and to thrive under conditions of nutrient imbalance.     

Water relations and hydraulic architecture of two Patagonian steppe shrubs: Effect of slope orientation and microclimate

On a local scale, topography influences microclimate, vegetation structure and the morpho-physiological attributes of plants. We studied the effects of microclimatic differences between NE- and SW-facing slopes on the water relations and hydraulic properties of two dominant shrubs of the Patagonian steppe in Argentina (Retanilla patagonica and Colliguaja integerrima). The NE-facing slope had higher irradiance and air saturation deficits and lower soil water availability and wind speed than the SW-facing slope. Predawn and midday Ψ_L and osmotic potentials were significantly lower in shrubs on the NE-facing slope. Osmotic adjustment and more elastic cell walls helped the plants to cope with a more xeric environment on NE-facing slope. Higher water deficits on NE-facing slope were partially compensated by a higher leaf and stem water storage. While stem hydraulic efficiency did not vary between slopes, leaf hydraulic conductance was between 40% and 300% higher on the NE-facing slope. Changes observed in leaf size and in SLA were consistent with responses to mechanical forces of wind (smaller and scleromorphic leaves on SW-facing slope). Morpho-physiological adjustments observed at a short spatial scale allow maintenance of midday Ψ_L above the turgor loss point and demonstrate that leaves are more responsive to microclimatic selective pressures than stems.     

An amalgamated meter-thick sedimentary package enabled by the 2011 Tohoku tsunami in El Garrapatero,Galapagos Islands

Tsunamis and storms instigate sedimentological and geomorphological changes to the coastal system, both long-term and ephemeral. To accurately predict future coastal hazards, one must identify the records that are generated by the processes associated with these hazards and recognize what will be preserved. Using eyewitness accounts, photographs, and sedimentology, this study documents pre- and post-tsunami conditions and constrains the timing and process of depositional events during and following the 11 March 2011 Tohoku tsunami in the coastal system at El Garrapatero, Galapagos Islands. While the tsunami acted as both an erosional and depositional agent, the thick, fan-like sand sheet in El Garrapatero was primarily emplaced by overwash deposition during high tide from swell waves occurring between 19–25 March and 17–22 April 2011. The swell waves were only able to access the terrestrial coastal system via a channel carved by the 2011 Tohoku tsunami through the barrier sand dune. This combined deposit could result in an overestimation of the hazard if interpreted to be the result of only one event (either tsunami or wind-generated waves). An analogous sand layer, younger than 1390–1530 cal yr BP, may record a similar, prior event.     

Impacts of macroalgal spores on the dynamics of adult macroalgae in a eutrophic estuary: high versus low hydrodynamic seasons and long-term simulations for global warming scenarios

A model describing macroalgal early life stages and adult dynamics was used to quantify the effects of non-adult forms on the productivity of adult macroalgae in a eutrophic estuary. Predictions indicate that during years with mild winters and low rainfall, spring blooms will occur at the expense of the growth and reproduction of overwintering adults and without the contribution of the spore bank. In these circumstances, there is a positive correlation between the intensity of the blooms and the biomass of overwintering adults until a maximum threshold value. On the contrary, in years with high rainfall and low or inexistent biomass of overwintering adults, the onset of adult’s growth depends on the biomass of viable dormant spores, the growing season occurs later and adult productivity is very limited. Long-term predictions for climate change scenarios suggest that, in general, global warming will have adverse affects on Ulva intestinalis productivity, with the adults being more affected than the early life stages.     

SHRINKING HOUSEHOLD SIZE AND ITS EFFECT ON URBAN POPULATION DENSITY PATTERNS: A CASE STUDY OF PHOENIX,ARIZONA

Increased divorce, declining fertility and mortality, and changing lifestyles have resulted in a consistent decline in average household size in U.S. urban areas. The purpose of this paper is to show that decreases in household size between 1970 and 1975 were spatially variable in metropolitan Phoenix and that this affected the overall pattern of residential density. This is demonstrated by a series of maps depicting average household size in 1970, changes therein between 1970 and 1975, and the relationships between changes in population, numbers of dwelling units, and household size in the study area.     

Managing land-use effects on Northland dune lakes: lessons from the past

The Northland region of New Zealand includes numerous high-value, macrophyte-dominated dune lakes. Recent water policy reforms offer limited guidance on managing for aquatic macrophytes. In addition, dune lake histories are poorly known as regular monitoring dates to 2005 AD. Here, ca. 4000 years of lake functional behaviour is reconstructed from sedimentary archives in two Northland dune lakes (Humuhumu and Rotokawau). Results demonstrated that macrophyte dominance is sensitive to catchment erosion and hydrological drawdown. Degradation of macrophyte communities occurred in the nineteenth and twentieth centuries, earlier at Lake Humuhumu than Lake Rotokawau (post-1880 AD and post-1930 AD, respectively). In both lakes, increased erosional influx reduced macrophyte productivity, before later increases to wider trophic state (post-1970 AD). Lake-level decline is linked to increased nutrient loading at Lake Rotokawau but less so, Lake Humuhumu which is more strongly groundwater-fed. In Northland dune lakes, water-level reduction and erosional influx from land use have driven macrophyte degradation.     

Investigation of natural and anthropogenic hydrocarbon inputs in sediments using geochemical markers. I. Santos, SP--Brazil

A study on the inputs of organic matter to marine sediments of Santos Bay and Estuary, located in southeastern S?o Paulo State, Brazil, is presented here. The following geochemical markers were identified and quantified: aliphatic hydrocarbons (normal and isoprenoid alkanes), petroleum biomarkers, linear alkylbenzenes (LABs) and polycyclic aromatic hydrocarbons (PAHs). Sediment samples, collected at 15 sites in the bay and surrounding channels, were extracted and analyzed by gas chromatography with flame ionization and mass spectrometer detectors. Total concentrations varied from 0.17 to 107.80 microg g(-1) for aliphatics, from 47.2 to 2560.1 ng g(-1) for petroleum biomarkers, from 16.9 to 430.6 ng g(-1) for LABs and from 79.6 to 15389.1 ng g(-1) for PAHs. Anthropogenic contributions were apparent, indicating the influences of the Cubatao industrial complex, sewage outfalls along the area, the waste deposit of Santos city and storage facilities for petroleum and derivatives, based on the higher concentrations of geochemical markers detected.