Fatty acid composition of the triacylglycerols of the cypris larva of the barnacle Balanus balanoides during metamorphosis

In the free-swimming cypris larva of Balanus balanoides, the mean level of triacylglycerols (triglycerides) was 8% of the ash-free dry weight. During metamorphosis into the juvenile barnacle, the triacylglycerol level in the newly settled non-feeding cypris larva fell to a mean of 2% of the ash-free dry weight. The ratio of fatty acids in the triacylglycerols remained constant throughout metamorphosis, indicating that all species of fatty acids were used as energy sources. There was no evidence for the selective utilisation of particular fatty acids.     

Fine structure of spermatids and sperm of Dolioletta gegenbauri and Doliolum nationalis (Tunicata: Thaliacea): implications for tunicate phylogeny

In Dolioletta gegenbauri and Doliolum nationalis, collected in 1987 in the bay of Villefranche-sur-mer (French Mediterranean Sea), spermiogenesis is essentially the same. Early spermatids have a round head, a flagellum arising from a single centriole with short microtubules at 45° to its base, several mitochondria, and an acrosome 50 nm thick and 250 nm long with its long axis parallel to the plasma membrane. The acrosomal contents are dense, with a central denser plate. The nuclear envelope next to the acrosome is thickened and concave. In elongating nuclei, strands of chromatin become oriented parallel to the length of the nucleus and then twist helically. Although the mitochondria surround the nucleus, they remain relatively short and do not fuse into a single mitochondrion as in sperm of other tunicates. In very late doliolid spermatids, the acrosome undergoes exocytosis, and exposes fibrous material that stays associated with the tip of the sperm; no acrosomal tubule forms. Exocytosis at this stage may be triggered by fixation. If so, exocytosis probably occurs naturally at some time before fusion of sperm and egg. Sperm have elongate heads (1 m×10 m), with the anterior two-thirds of the nucleus surrounded by mitochondria. Spermiogenesis in doliolids, compared to that in other tunicates, is most like that in solitary members of the class Ascidiacea, except that in the latter the sperm mitochondria fuse and the acrosome appears incapable of exocytosis. In contrast, previous work has shown that salps (class Thaliacea) and colonial didemnid ascidians have an acrosomeless sperm with a spiral mitochondrion, while the class Appendicularia has a sperm with a midpiece, a compact head and an acrosome capable of exocytosis and acrosomal tubule formation. By outgroup comparison with echinoderms and acraniates, appendicularian sperm are plesiomorphic within the Tunicata. Thus, gamete morphology indicates that (1) solitary ascidians and doliolids had a common ancestor, (2) the popular idea that doliolids gave rise to appendicularians is incorrect, and (3) the Thaliacea are polyphyletic, doliolids having arisen very early from the ascidian lineage and salps having arisen later.     

A Numerical Study of the Dynamics of the Riverine Thermal Bar in a Deep Lake

A numerical model based on a Finite Volume formulation of the Navier–Stokes equations is used to simulate a range of scenarios leading to a thermal bar formed by a river inflow to an idealised deep lake. The results presented here show that small riverine salinity increases have a profound effect on the dynamics of the thermal bar, suppressing horizontal propagation of the plume and raising the possibility of a thermal bar which is capable of sinking to great depths. This finding is particularly relevant to Lake Baikal in Siberia, where the vigorous deep-water renewal is still not fully understood. An analysis of the buoyancy forces governing the depth of penetration of the thermal bar plume shows that realistic salinity gradients are an important factor in determining the circulation of Baikal waters. Observations of the saline curtailment of the thermal bar's horizontal propagation also reveal a potential for reduced productivity in the ecosystem of any temperate river delta during the Spring renewal period.     

Biochemical composition and energy reserves in the larvae and adults of the four british periwinkles Littorina littorea,L. littoralis,L. saxatilis and L. neritoides

The biochemical composition of the adult body tissue is similar in Littorina littorea, L. littoralis, L. saxatilis and L. neritoides. In the newly crawling metamorphosed young of L. littoralis and L. saxatilis, the biochemical composition is similar to that of the mature adults. The newly released planktonic veliger larvae of L. littorea and L. neritoides, which represent and earlier stage of development than the newly crawling young, have a neutral lipid level (mean, 16.5% of ash-free dry flesh weight) approximately three times the level (5.4%) in the newly crawling young of L. littoralis and L. saxatilis. Otherwise the biochemical composition of free-swimming larvae is similar to that of newly crawling young and adults. Neutral lipid is apparently utilised by L. littoralis and L. saxatilis larvae during larval development and metamorphosis. It is suggested that neutral lipid is the major energy reserve of Littorina veliger larvae whereas in the adults, as exemplified by L. littorea, both lipid and carbohydrate are important as energy reserves.     

Spermatogenesis inPyrosoma atlanticum (Tunicata: Thaliacea: Pyrosomatida): Implications for tunicate phylogeny

Colonies ofPyrosoma atlanticum were collected by submersible in October 1988 in the Caribbean Sea, and testes were studied by electron microscopy. Spermatogonia, spermatocytes and early spermatids have two centrioles. The proximal centriole subsequently disappears, its remains apparently persisting in the spermatozoon as dense material adjacent to the distal centriole, which gives rise to the axoneme. At the tip of early spermatids are several 50 nm proacrosomal vesicles, which disappear leaving no trace in early elongating spermatids. The spermatozoon lacks an acrosome and has a head 35µm long. The head is differentiated into a bulbous posterior portion 5µm long × 1µm wide, a thinner anterior portion 25µm long tapering from a width of 0.7µm to a width of 0.4µm, and a very thin anterior extension 5µm long × 0.5µm wide. At the start of elongation, the anterior extension begins to form just lateral to the proacrosomal vesicles as a spiral projection comprising part of the nucleus, covered by a thin sheath of cytoplasm. This sheath of cytoplasm undergoes a complex differentiation. Ultimately, the nucleus in the anterior extension is overlain by two membrane-bound sheaths of cytoplasm connected by a spiral flange of cytoplasm. Between these two sheaths is a spiral space, open to the exterior through a subterminal pore near the sperm tip. In early spermatids the mitochondria fuse into a single mitochondrion, which remains lateral to the nucleus. The cristae become modified late in spermatogenesis. Throughout elongation of the spermatid there are patches of dense material between the nucleus and mitochondrion. A manchette of microtubules transiently encircles the thin anterior portion of the nucleus during the last phase of elongation. A manchette is not present during most of elongation. In the spermatozoon the mitochondrion, which has reticulate cristae, spirals a few times about the nucleus and extends from the junction between the bulbous portion and the thinner anterior portion of the nucleus to the junction between the thinner anterior portion and the nuclear extension. Spermatogenesis inP. atlanticum, compared to that in other tunicates, most closely resembles that in colonial ascidians, and supports the majority view that pyrosomes arose from aplousobranch ascidians that lost their attachment to the substratum. Pyrosome sperm are more highly derived than doliolid sperm, which have an acrosome that is probably capable of exocytosis. When salp and pyrosome sperm are compared, both are highly derived, but neither shares any apomorphies with the other that it does not share with at least one other tunicate order. Thus, sperm morphology does not support the majority view that pyrosomes gave rise to doliolids and neither confirms nor denies the idea that pyrosomes are intermediate between aplousobranch ascidians and salps. Therefore, it is likely that the class Thaliacea is polyphyletic, with doliolids arising very early from the ascidian lineage and with salps and pyrosomes arising somewhat later.     

Market design in cap and trade programs: Permit validity and compliance timing

Cap and trade programs have considerable heterogeneity in permit validity and compliance timing. For example, permits have different validities across time (e.g., banking, borrowing, and seasons) and space (e.g., zonal restrictions), and compliance timing can be annual, in overlapping cycles, or in multi-year periods. We discuss nine prominent cap and trade programs along these dimensions and construct a general model of permit validity and compliance timing. We derive sufficient conditions under which abatement is invariant to compliance timing, i.e., compliance timing cannot smooth abatement cost shocks. Under these conditions, (i) expected compliance costs are invariant, (ii) the variance of compliance costs increases with the delayed compliance, (iii) equilibrium prices may not be unique, and (iv) the delayed compliance equilibrium may rely on “degenerate” prices not determined by marginal abatement costs. We demonstrate the model's broad applicability by illustrating different types of temporal permit validity.     

Sustainable soil remediation by refrigerated condensation at sites with “high‐concentration” recalcitrant compounds and NAPL: Two case studies

Remediation of recalcitrant compounds at sites with high concentrations of volatile organic compounds (VOCs) or nonaqueous‐phase liquids (NAPLs) can present significant technical and financial (long‐term) risk for stakeholders. Until recently, however, sustainability has not been included as a significant factor to be considered in the feasibility and risk evaluation for remediation technologies. The authors present a framework for which sustainability can be incorporated into the remediation selection criteria focusing specifically on off‐gas treatment selection for soil vapor extraction (SVE) remediation technology. SVE is generally considered an old and standard approach to in situ remediation of soils at a contaminated site. The focus on off‐gas treatment technology selection in this article allows for more in‐depth analysis of the feasibility evaluation process and how sustainable practices might influence the process. SVE is more commonly employed for recovery of VOCs from soils than other technologies and generally employs granular activated carbon (GAC), catalytic, or thermal oxidation, or an emerging alternative technology known as cryogenic‐compression and condensation combined with regenerative adsorption (C3–Technology). Of particular challenge to the off‐gas treatment selection process is the potential variety of chemical constituents and concentrations changing over time. Guidance is available regarding selection of off‐gas treatment technology (Air Force Center for Environmental Excellence, 1996; U.S. Environmental Protection Agency, 2006). However, there are common shortcomings of off‐gas treatment technology guidance and applications; practitioners have rarely considered sustainability and environmental impact of off‐gas treatment technology selection. This evaluation includes consideration of environmental sustainability in the selection of off‐gas treatment technologies and a region‐specific (Los Angeles, California) cost per pound and time of remediation comparisons between GAC, thermal oxidation, and C3–Technology. © 2008 Wiley Periodicals, Inc.     

Hydrological variability and agricultural drainage ditch inorganic nitrogen reduction capacity

The application of inorganic nitrogen fertilizers on agricultural landscapes has the potential to generate concerns of environmental degradation at fine to coarse scales across the catchment and landscape. Inorganic nitrogen species (NO3*, NO2*, and NH3) are typically associated with subsurface flow processes; however, surface runoff from rainfall events in no-till agriculture with inorganic surface fertilizers might contribute to downstream eutrophication. Inorganic nitrogen reduction capacity of agricultural drainage ditches under no-till cotton was determined under natural, variable rainfall conditions in northern Mississippi. Monthly grab baseflow samples and storm-generated flow samples were variably sampled temporally within two experimental farm ditches over 2 yr. Inorganic nitrogen concentrations, in conjunction with Manning's equation and Natural Resources Conservation Service dimensionless hydrographs, provided individual water volumes per storm event and thus maximum effluent and outflow nitrogen loads. Base and stormflow regression results indicate drainage ditches reducing NO3* and NH3 over the length of the ditch for growing and dormant seasons. Overall, maximum storm loads of dissolved inorganic nitrogen (DIN) from the farm over the 2-yr sampling period accounted for 2.2% of the initial fertilizer application, of which 1.1% left the ditch (0.84 kg ha(-1) yr(-1)) (a 57% ditch reduction of DIN load over 2 yr). Long-term sampling incorporating data on application and loss of fertilizers and farm management will provide critical information for farmers and scientists on the potential of economic gains and downstream ecosystem eutrophication, respectively.     

Off‐gas treatment carbon footprint calculator: Form and function

The quantification of greenhouse gas (GHG) emissions can be a powerful sustainability measurement indicator for assessing environmental impacts of various operations, which can include remediation of chemically impacted media or construction projects. A carbon footprint calculator was developed and is presented in this article as one tool for applying sustainable practices to environmental remediation—specifically to assess the GHG footprint for remediation projects. The calculator is constructed from a compilation of published metrics and “standards.” © 2008 Wiley Periodicals, Inc.     

Multinomial mixture model with heterogeneous classification probabilities

Royle and Link (Ecology 86(9):2505?C2512, 2005) proposed an analytical method that allowed estimation of multinomial distribution parameters and classification probabilities from categorical data measured with error. While useful, we demonstrate algebraically and by simulations that this method yields biased multinomial parameter estimates when the probabilities of correct category classifications vary among sampling units. We address this shortcoming by treating these probabilities as logit-normal random variables within a Bayesian framework. We use Markov chain Monte Carlo to compute Bayes estimates from a simulated sample from the posterior distribution. Based on simulations, this elaborated Royle-Link model yields nearly unbiased estimates of multinomial and correct classification probability estimates when classification probabilities are allowed to vary according to the normal distribution on the logit scale or according to the Beta distribution. The method is illustrated using categorical submersed aquatic vegetation data.