Polychlorinated dibenzo-p-dioxins and the human immune system: 4 studies on two Spanish families with increased body burdens of highly chlorinated PCDDs

The consequences of exposure of people to highly chlorinated polychlorodibenzo-p-dioxins (PCDDs) are much less known than those of TCDD. We report on levels of PCDDs (and PCDFs) in 13 members of two families poisoned by contaminated cooking oil. Originally, all persons displayed chloracne as an early symptom. Persisting hexa- and higher chlorinated PCDDs could be analysed many years after exposure. Highest values found in blood lipids were: OCDD 660,000 pg/g; HpCDD 58,000 pg/g; HxCDDs: 3500 pg/g. None of the participants exhibited increased TCDD levels at the time of study. During a period of 6 years, HpCDD and OCDD disappeared from the blood lipids much faster in persons exposed as children or young adults, than from lipids of their parents. Surface receptors on blood lymphocytes of the members of the two families and the proliferative capacity of these blood cells in the presence of typical stimulants were analysed. Even in family members with the highest body burdens of hexa- to octachlorinated PCDDs we could not detect pronounced changes from a reference population with respect to the immunological markers. Minor deviations of levels of some receptors in a few, but not all, highly exposed persons suggested a similar trend to those reported in previous studies of persons with body burdens of > or =3000 pg TCDD/g blood lipids. An increase in the number of total blood lymphocytes in some subjects exposed as children may have similarity with highly TCDD-exposed children in Seveso.     

Sheepfolds as “hotspots” of nitric oxide (NO) emission in an Inner Mongolian steppe

We investigated nitric oxide (NO) fluxes at a summer and a winter sheepfold in the Baiyinxile livestock farm, near Xilinhot, Inner Mongolia, which are a typical feature of the regional husbandry. Using a manual static opaque chamber/chemiluminescence measuring system, we intermittently observed fluxes in the summer sheepfold between May 28th and September 26th 2005 and in both winter and summer sheepfolds between March 8th and October 18th 2006. During these periods, mean NO emissions (±S.E., in terms of mass of nitrogen) were 124.0 ± 28.7, 134.6 ± 23.3 (summer sheepfold) and 214.4 ± 79.6 μg NO–N m⁻² h⁻¹ (winter sheepfold), respectively, and thus, three magnitudes higher than observed steppe NO emissions in the same region. The NO fluxes were not significantly different between the 2 years, but in summer they were much higher than in spring (p < 0.05). Temperature and moisture of the faeces layer significantly regulated the NO fluxes (p < 0.01). The direct NO emission factor (EF) for faeces and urine excreted in the sheepfolds was 0.7 g NO–N_emitted kg⁻¹ N_excreted, which was almost 37 times lower than a recently reported N₂O EF. We estimated the total NO emission from the sheepfolds of the Baiyinxile livestock farm to be 1.82 ± 0.43 tons NO–N year⁻¹, which accounts to approximately 12.3% of the total NO emission from this steppe region. With the rapid increase of livestock numbers, sheepfold NO emissions may further increase and contribute to high N deposition in confined areas around sheepfolds.     

Unique animal prenyltransferase with monoterpene synthase activity

Monoterpenes are structurally diverse natural compounds that play an essential role in the chemical ecology of a wide array of organisms. A key enzyme in monoterpene biosynthesis is geranyl diphosphate synthase (GPPS). GPPS is an isoprenyl diphosphate synthase that catalyzes a single electrophilic condensation reaction between dimethylallyl diphosphate (C₅) and isopentenyl diphosphate (C₅) to produce geranyl diphosphate (GDP; C₁₀). GDP is the universal precursor to all monoterpenes. Subsequently, monoterpene synthases are responsible for the transformation of GDP to a variety of acyclic, monocyclic, and bicyclic monoterpene products. In pheromone-producing male Ips pini bark beetles (Coleoptera: Scolytidae), the acyclic monoterpene myrcene is required for the production of the major aggregation pheromone component, ipsdienol. Here, we report monoterpene synthase activity associated with GPPS of I. pini. Enzyme assays were performed on recombinant GPPS to determine the presence of monoterpene synthase activity, and the reaction products were analyzed by coupled gas chromatography–mass spectrometry. The functionally expressed recombinant enzyme produced both GDP and myrcene, making GPPS of I. pini a bifunctional enzyme. This unique insect isoprenyl diphosphate synthase possesses the functional plasticity that is characteristic of terpene biosynthetic enzymes of plants, contributing toward the current understanding of product specificity of the isoprenoid pathway.     

Lethal effects of Northwest Atlantic Ocean isolates of the dinoflagellate, Scrippsiella trochoidea, on Eastern oyster (Crassostrea virginica) and Northern quahog (Mercenaria mercenaria) larvae

The thecate dinoflagellate Scrippsiella trochoidea is a cosmopolitan, bloom-forming alga that has been generally considered non-toxic. Here, we report that environmentally relevant cell densities (10⁴ cells mL⁻¹) of Scrippsiella trochoidea strains isolated from the Northwest Atlantic Ocean caused 100% mortality in Eastern oyster (Crassostrea virginica) larvae during 3-day exposures while parallel control larvae exhibited 100% survival. S. trochoidea also exhibited lethal effects on Northern quahog (Mercenaria mercenaria) larvae (70% mortality during 3-day exposure) but were non-toxic to juvenile fish (Cyprinodon variegates). The cultures of S. trochoidea were more lethal to Northern quahog larvae than ten other species of harmful algae, including the highly toxic species Cochlodinium polykrikoides. Scrippsiella trochoidea cultures within later stages of growth were more toxic than exponential growth stages to bivalve larvae, and the toxicity was dose dependent. Furthermore, toxicity was maintained in the cultures that were sonicated, boiled, and frozen as well as in resuspended residues of the culture but was significantly lower in cell-free culture media. Collectively, these results suggest that S. trochoidea causes mortality in bivalve larvae through a physicochemical rather than strictly chemical mechanism, such as clogging of larval feeding apparatuses by materials produced by S. trochoidea (e.g., lipids, extracellular polysaccharides, and/or cell debris) which accumulate as cells in culture or blooms age. This is the first report of the lethal effects of Scrippsiella trochoidea on shellfish larvae.     

Chick-a-dee call variation in the context of “flying” avian predator stimuli: a field study of Carolina chickadees (<Emphasis Type="Italic">Poecile carolinensis</Emphasis>)

Chick-a-dee calls function in social organization in Poecile (chickadee) species. Recent field and aviary studies have found that variation in chick-a-dee calls relates to the type or proximity of avian predator, or level of threat. Earlier studies on calls in the context of predator stimuli have typically used stationary and perched predator models. For chickadees and other small songbirds, more frequently detected and more dangerous avian predatory stimuli are flying predators. In the present study, we tested whether simulated flying avian predator and control models influenced chick-a-dee calling behavior of wild Carolina chickadees, Poecile carolinensis. At 20 independent field sites, chickadee subjects were presented with wooden models that were painted to resemble either a predatory sharp-shinned hawk (Accipiter striatus) or a blue jay (Cyanocitta cristata) and that were made to “fly” down a zip line near a feeding station chickadees were using. The note composition of chick-a-dee calls was affected by both the flight of stimuli and type of model. Call variation in this flying predator context suggests interesting similarities and differences with experimental findings with congeners. Finally, increased production of certain notes to the flying of both model types provides support for a “Better Safe than Sorry” strategy. When costs of alarm calling are low but costs of discriminating potentially serious threats may be extremely high, individuals should err on the side of caution, and alarm call to any potentially threatening stimulus.     

Role of temperature on lipid/fatty acid composition in Pacific cod (Gadus macrocephalus) eggs and unfed larvae

During early development, oviparous fish species must use finite lipid and fatty acid (FA) reserves for both catabolism and structural components. In cold environments, developing fish have the additional constraint of maintaining membrane fluidity for metabolic efficiency (homeoviscous adaptation), resulting in further demand on lower melting point FAs like n-3 polyunsaturated fatty acids (PUFAs). To examine whether marine fish embryos physiologically adapt to changing temperature environments, we incubated Pacific cod (Gadus macrocephalus) eggs at 5 temperatures (0, 2, 4, 6, and 8 °C) in the laboratory and sampled them repeatedly during development to measure changes in lipid/FA composition. Pacific cod embryos increased n-3 PUFA content during the egg stage in all temperature treatments, with the possible exception of 0 °C, where poor survival and hatch success limited our ability for continued sampling. At the beginning of the hatch cycle, free-swimming embryos shifted from lipogenesis to lipid catabolism. The rates of lipogenesis and catabolism were temperature dependent, and the distinct increase in unsaturated fatty acids at temperatures <8 °C was consistent with homeoviscous adaptation theory. However, with the possible exception of embryos at 0 °C, the relative amounts of essential fatty acids (e.g., EPA, DHA, AA) were conserved in a similar manner across incubation temperatures. Collectively, these data suggest Pacific cod are capable of homeoviscous adaptation but cannot tolerate temperatures approaching 0 °C despite their possible ability to biosynthesize PUFAs from other energetic sources.     

First-instar monarch larval growth and survival on milkweeds in southern California: effects of latex, leaf hairs and cardenolides

Growth rate and survival of first-instar larvae of Danaus plexippus, a milkweed specialist, depended on milkweed species, and was related to the amount of latex produced from wounds, leaf cardenolide concentrations and the presence of leaf hairs. Larval growth was more rapid and survival was higher on leaves of Asclepias californica with experimentally reduced latex, and this species has characteristically high latex, low- to mid-range cardenolide concentrations, and very hirsute leaves. Similarly, growth was higher on reduced latex leaves of both A. eriocarpa (a high latex/high cardenolide, hirsute species) and A. erosa (glabrous fleshy leaves, high latex/high cardenolides). There were no differences in either survival or growth rate between larvae on reduced latex or control leaves of the low latex/low cardenolide A. fascicularis with soft glabrous leaves and both survival and growth rate were higher on this species than the other species tested. Larval growth rates on leaves with reduced latex were similar among ten milkweed species tested to date but differed from growth rates on intact leaves suggesting that latex and possibly included cardenolides are both important in first-instar monarch larval growth, development and survival. We show for a range of ecologically important milkweeds that experiments on cut plant material (no latex outflow) lead to higher growth rates compared to intact plants. Such laboratory assays based on detached leaves will be misleading if the objective is to determine the impact of treatments such as Bt-maize pollen on monarchs on field plants.     

How long can fisheries management delay action in response to ecosystem and climate change?

Sustainable management of fisheries is often compromised by management delaying implementation of regulations that reduce harvest, in order to maintain higher catches in the short-term. Decreases or increases in fish population growth rate driven by environmental change, including ecosystem and climate change, affect the harvest that can be taken sustainably. If not acted on rapidly, environmental change could result in unsustainable fishing or missed opportunity for higher catches. Using simulation models of harvested fish populations influenced by environmental change, we explore how long fisheries managers can afford to wait before changing harvest regulations in response to changes in population growth. If environmental change causes population declines, delays greater than five years increase the probability of population collapse. Species with fast and highly variable population growth rates are more susceptible to collapse under delays and should be a priority for revised management where delays occur. Generally, the long-term cost of delay, in terms of lost fishing opportunity, exceeds the short-term benefits of overfishing. Lowering harvest limits and monitoring for environmental change can alleviate the impact of delays; however, these measures may be more costly than reducing delays. We recommend that management systems that allow rapid responses to population growth changes be enacted for fisheries management to adapt to ecosystem and climate change.     

Collaborative assessment of California spiny lobster population and fishery responses to a marine reserve network

Assessments of the conservation and fisheries effects of marine reserves typically focus on single reserves where sampling occurs over narrow spatiotemporal scales. A strategy for broadening the collection and interpretation of data is collaborative fisheries research (CFR). Here we report results of a CFR program formed in part to test whether reserves at the Santa Barbara Channel Islands, USA, influenced lobster size and trap yield, and whether abundance changes in reserves led to spillover that influenced trap yield and effort distribution near reserve borders. Industry training of scientists allowed us to sample reserves with fishery relevant metrics that we compared with pre-reserve fishing records, a concurrent port sampling program, fishery effort patterns, the local ecological knowledge (LEK) of fishermen, and fishery-independent visual surveys of lobster abundance. After six years of reserve protection, there was a four- to eightfold increase in trap yield, a 5-10% increase in the mean size (carapace length) of legal sized lobsters, and larger size structure of lobsters trapped inside vs. outside of three replicate reserves. Patterns in trap data were corroborated by visual scuba surveys that indicated a four- to sixfold increase in lobster density inside reserves. Population increases within reserves did not lead to increased trap yields or effort concentrations (fishing the line) immediately outside reserve borders. The absence of these catch and effort trends, which are indicative of spillover, may be due to moderate total mortality (Z = 0.59 for legal sized lobsters outside reserves), which was estimated from analysis of growth and length frequency data collected as part of our CFR program. Spillover at the Channel Islands reserves may be occurring but at levels that are insufficient to influence the fishery dynamics that we measured. Future increases in fishing effort (outside reserves) and lobster biomass (inside reserves) are likely and may lead to increased spillover, and CFR provides an ideal platform for continued assessment of fishery-reserve interactions.     

Trends over time in tree and seedling phylogenetic diversity indicate regional differences in forest biodiversity change

Changing climate conditions may impact the short-term ability of forest tree species to regenerate in many locations. In the longer term, tree species may be unable to persist in some locations while they become established in new places. Over both time frames, forest tree biodiversity may change in unexpected ways. Using repeated inventory measurements five years apart from more than 7000 forested plots in the eastern United States, we tested three hypotheses: phylogenetic diversity is substantially different from species richness as a measure of biodiversity; forest communities have undergone recent changes in phylogenetic diversity that differ by size class, region, and seed dispersal strategy; and these patterns are consistent with expected early effects of climate change. Specifically, the magnitude of diversity change across broad regions should be greater among seedlings than in trees, should be associated with latitude and elevation, and should be greater among species with high dispersal capacity. Our analyses demonstrated that phylogenetic diversity and species richness are decoupled at small and medium scales and are imperfectly associated at large scales. This suggests that it is appropriate to apply indicators of biodiversity change based on phylogenetic diversity, which account for evolutionary relationships among species and may better represent community functional diversity. Our results also detected broadscale patterns of forest biodiversity change that are consistent with expected early effects of climate change. First, the statistically significant increase over time in seedling diversity in the South suggests that conditions there have become more favorable for the reproduction and dispersal of a wider variety of species, whereas the significant decrease in northern seedling diversity indicates that northern conditions have become less favorable. Second, we found weak correlations between seedling diversity change and latitude in both zones, with stronger relationships apparent in some ecoregions. Finally, we detected broadscale seedling diversity increases among species with longer-distance dispersal capacity, even in the northern zone, where overall seedling diversity declined. The statistical power and geographic extent of such analyses will increase as data become available over larger areas and as plot measurements are repeated at regular intervals over a longer period of time.