Microzooplankton Grazing in Green Water—Results from Two Contrasting Estuaries

We measured seasonal variations in microzooplankton grazing in Long Island Sound (LIS) and San Francisco Bay (SFB). There was consistent evidence of nutrient limitation in LIS, but not SFB. We found higher chlorophyll a concentrations in LIS compared with SFB. In spite of differences in phytoplankton, there were no differences in microzooplankton abundance (summer: LIS, 12.4 ± 1.8 × 10³ indiv. L⁻¹; SFB, 14.1 ± 3.0 × 10³ indiv. L⁻¹), biomass (summer: LIS, 30.4 ± 5.0 μg C L⁻¹; SFB, 26.3 ± 5.9 μg C L⁻¹), or grazing rates (summer: LIS, 0.66 ± 0.19 day⁻¹; SFB, 0.65 ± 0.18 day⁻¹) between the two estuaries. In common with many other investigators, we found many instances of saturated as well as insignificant grazing. We suggest that saturation in some cases may result from high particle loads in turbid estuarine systems and that insignificant grazing may result from extreme saturation of the grazing response due to the need to process non-food particles.     

The construction of human–animal relations: National Jumps Day 2013 at Te Rapa,Hamilton, New Zealand

New Zealand is an important place for thoroughbred breeding and racing. Most races are on the flat, but jumps racing is conducted in the cooler months. The 2013 National Jumps Day at Te Rapa, Hamilton, was a significant space for the construction of human–animal relations. Drawing on three bodies of accounts, we ask whether social media contributes to the realignment of perspectives or reinforces existing human–animal relations. We explore competing narratives and demonstrate how animals, people, activities and places are constructed, including making animal deaths unrecognisable to perpetuate activities that are questioned by contemporary animal geographies.     

The quartile-deviation/median-diameter relationships of glacial deposits

Quartile-deviation (QDa) and median-diameter (Md) values have been calculated from the grain-size distributions of a variety of Pleistocene and modern glacial and para-glacial sediments. The QDa—Md pairs are plotted on double-log graph paper to determine whether their graphic distributions are distinctive, and to examine their sedimentological implications. Three distributions emerge. The first has a shallow gradient and represents coarse bi-modal tills consisting largely of rock fragments — distribution (a). The second, with an intermediate gradient, represents fine uni- or non-modal tills consisting mainly of monomineralic grains — distribution (b). The third (c) has a steep gradient and consists of bi-modal tills with a dominant proportion of monomineralic grains. Each of these distributions is explained by using the grain-size characteristics of physically weathered rock debris as a starting point for discussion. By a process dominated by the continual addition of weathered-grain populations (population addition), tills with (a) characteristics are formed. By a process dominated by comminution and the selective removal of grains by ablation (population subtraction), tills with (b) characteristics are formed. Any of these tills, when subjected to flowing water, rapidly lose their glacial characteristics and assume QDa—Md characteristics of fluvial deposits (although they are fluvioglacial).     

Authigenic uranium: Relationship to oxygen penetration depth and organic carbon rain

We have measured U in benthic incubation chambers, sediment pore waters, and in sediments along the California continental margin. Sedimentary U uptake rates, based on a combination of sediment pore water profiles and benthic incubation chambers, generally agree with those predicted from sediment accumulation rate data. This agreement supports the view that most of the continental margin sedimentary U is delivered by diffusion across the seawater-sediment boundary. The average rate of authigenic U accumulation for all the sites examined here is ∼−0.2 nmol cm^-2 y^-1, which is consistent with published global estimates of sedimentary U uptake. In addition, the accumulation rate of U in sediments exhibits a nonlinear relationship with the oxygen penetration depth and a linear relationship with the organic carbon rain rate. These relationships highlight the potential utility for the U accumulation rate as a proxy for these processes.     

The role of wind in generating turbidity maxima in the Tay Estuary

Variations of wind direction and strength in the Tay Estuary control wave generation and the resultant patterns of suspended sediment concentration in the waters over the extensive tidal flats. Bodies of water with high water concentration peaks advect to occupy sites at which turbidity maxima are normally present at low water. Other low water peaks are generated by ebb tidal current resuspension.     

Using a maximum simplicity paleoclimate model to simulate millennial variability during the last four glacial periods

Many studies have documented the existence of millennial-scale variability in the Earth system during the last glacial period. An increasing number of studies document the occurrence of similar millennial variability during glacial periods previous to the last one. Here we use the simplest possible thermal-bipolar seesaw model to consider this variability for the last four glacial periods. We invert this model and use the high-pass filtered Vostok stable isotope records to make a first, tentative, attempt to estimate high-latitude N. Hemisphere temperature variability over the last four glacial periods, beyond the reach of Greenland ice-core records. The model result is compared against the Vostok methane record, which shows rapid variations in parallel to Greenland temperature records during the last glacial period. A further comparison is carried out against the planktonic oxygen isotope of north Atlantic core ODP 980. There is agreement between the records on the existence of similar millennial-scale variability during the last three glacial periods with very similar characteristics to the variability during the last glacial cycle.     

Geological Applications of Laser‐Induced Breakdown Spectroscopy

Laser‐induced breakdown spectroscopy (LIBS) records light emitted from the decay of electrons to lower‐energy orbitals during cooling of laser‐induced ablation plasmas; the resultant spectra can be used in a variety of geoanalytical applications. Four aspects of LIBS analysis distinguish LIBS from traditional laboratory‐based analytical techniques: (i) the lack of necessary sample preparation, allowing rapid analysis of many samples, (ii) the ability to analyse both 20 to 100 μm‐diameter spots and whole rocks, (iii) the detailed chemical signature contained in a LIBS spectrum and (iv) the ability to take LIBS into the field in backpack portable instrumentation. Three case studies illustrate potential applications of LIBS in the geosciences. First, analysis of the Carrizozo basalt flow in New Mexico, USA, illustrated that LIBS spectra could discriminate between samples of similar composition within uncertainties typical of whole‐rock analysis by X‐ray fluorescence spectrometry. Second, spectra from four sets of rubies from Madagascar and Tanzania illustrate the use of LIBS and multivariate analysis to determine provenance with success rates of > 95%. This technique can also be applied to correlation of units. Finally, a chemical map of a copper ore from Butte, MT, USA, illustrates the use of spatially defined LIBS spectra to understand chemical variations within textural context.