Remaining challenges in Tanzania's efforts to eliminate iodine deficiency

OBJECTIVE: To determine iodine levels in salt and iodine deficiency prevalence in school-aged children in 16 districts in Tanzania with previous severe iodine deficiency. DESIGN: A cross-sectional study in schoolchildren. Systematic probability sampling was used to select schools and subjects for goitre assessment and urinary iodine determination. SETTING: Sixteen districts randomly selected from the 27 categorised as severely iodine-deficient in Tanzania. SUBJECTS: The study population was primary-school children aged 6-18 years who were examined for goitre prevalence and urinary iodine concentration (UIC). Salt samples from schoolchildren's homes and from shops were tested for iodine content. RESULTS: The study revealed that 83.3% of households (n=21,160) in the surveyed districts used iodised salt. Also, 94% of sampled shops (n=397) sold iodised salt, with a median iodine level of 37.0 ppm (range 4.2-240 ppm). Median UIC in 2089 schoolchildren was 235.0 microg l(-1) and 9.3% had UIC values below 50 microg l(-1). The overall unweighted mean visible and total goitre prevalence was 6.7% and 24.3%, respectively (n=16,222). The age group 6-12 years had the lowest goitre prevalence (3.6% visible and 18.0% total goitre, n=7147). The total goitre prevalence had decreased significantly in all districts from an unweighted mean of 65.4% in the 1980s to 24.3% in 1999 (P<0.05). We believe this difference was also biologically significant.ConclusionThese findings indicate that iodine deficiency is largely eliminated in the 16 districts categorised as severely iodine-deficient in Tanzania, and that the iodine content of salt purchased from shops is highly variable.     

Activity of unrestrained horses during on-truck rest stops

The activity of unrestrained (slaughter) horses during 1-hour-long, on-truck rest stops was quantified to help determine whether horses get meaningful rest during on-truck rest stops. A single-deck semi-trailer divided into three compartments and fitted with 12 video cameras was used to record behavior of five shipments of horses during transport lasting 16 to 20 hours. Each shipment consisted of a high-, medium-, and low-density group averaging 397 ± 6.5 kg/m², 348 ± 5.2 kg/m², and 221 ± 7.6 kg/m², respectively. Horses were rested for 1 hour after 8 hours of transport and before unloading at the end of each transport. Two of the three groups in the trailer were provided water during each rest stop. Data were successfully collected for 13 groups of horses of varying ages, sexes, and breeds typical of slaughter horses. The high-density watered groups had increased activity during the first 10 minutes of the first and second rest stops, indicating the horses were interacting and maneuvering to get to the water. Activity in the medium- and low-density groups was much more variable, but when there was increased activity during the first 10 minutes of a rest stop, it was in groups that had access to water. No trends were evident for an increase in activity near the end of the rest stops. Activity during the first and second rest stops was similar, indicating that these horses were not fatigued to the point of reducing activity during rest stops after 16 to 20 hours of transport.     

Plankton dynamics: observed and modelled responses to physical conditions in Prince William Sound,Alaska

Plankton populations in Prince William Sound, Alaska, exhibited pronounced seasonal, annual and longer‐period variability in composition and standing stock in response to physically influenced differences in nutrient availability, and possibly currents that modify local biomass by exchanges with water from the bordering Gulf of Alaska. During springs in which early, strong physical stratification developed, intense, short‐lived phytoplankton blooms occurred. These blooms had relatively short residence times in the water column. In contrast, during springs in which slower, weaker stratification developed, phytoplankton blooms were prolonged and took longer to peak. These slower blooms prolonged the period of phytoplankton production, prolonged interaction with the springtime grazing community and led to the incorporation of more organic matter into pelagic food webs. A coupled biological‐physical simulation of plankton production was used to examine the implications of seasonally varying air and mixed‐layer temperatures, surface winds and incident light on the timing, duration, annual production and standing stock of plankton. Our modelling results reproduced the observed characteristics of the springtime production cycle, and the magnitude of zooplankton stocks for the period 1992–97 but not for 1981–91. These results suggest that for most of the 1990s, bottom‐up influences on nutrient supplies controlled levels of primary consumers, whereas for the 11 years before that, other unknown factors dominated this process. We present the results of a comprehensive, multiyear study of relationships between plankton and physical limitations, and a retrospective analysis of earlier conditions to explore the possible causes for these differences.     

Nursery and field establishment techniques to improve seedling growth of three Costa Rican hardwoods

Seedlings of three economically important and ecologicallydifferent native hardwoods, Cordia alliodora (Boraginaceae),Hyeronima alchorneoides (Euphorbiaceae), and Calophyllumbrasiliense (Clusiaceae), were grown in Rootrainers® (abook-type container), paper pots, and plastic bags filled witheither soil, soil with fertilizer, or compost substrates. Aftertransplanting in the field, treatments with and withoutfertilizer and herbicide were applied to all nursery stock types.In the nursery, species responded primarily to substrate type.Cordia grew better in bags of soil with NPK fertilizer andcompost than in unamended soil, probably responding to highernitrogen availability. Despite large treatment differences atplanting, there were no significant differences in plant sizeafter one year in the field between book containers and bags. Theexception were stump plants that were shorter and had highermortality. Hyeronima grew better in compost than in soil with orwithout fertilizer, probably responding to higher phosphorusavailability and lower bulk density of the compost. Plantsproduced in compost were also bigger after one year's fieldgrowth. Plants produced with soil or in paper pots had highermortality. Calophyllum grew less in compost compared to soil andgrew better when micronutrients were added to the compost andsoil. In the field, seedling produced in soil or withmicronutrients had higher survival or growth, respectively. Ingeneral, species grew better with herbicide and fertilizerapplication after transplanting. However, there were nointeractions with nursery treatments. Responses to fieldtreatments were independent and thus additive to the nurserytreatments. Differences in species response can be related tobiomass allocation patterns and ecology of the species.     

Seasonal floodplain‐tidal slough complex supports size variation for juvenile Chinook salmon (Oncorhynchus tshawytscha)

Population diversity is a mechanism for resilience and has been identified as a critical issue for fisheries management, but restoration ecologists lack evidence for specific habitat features or processes that promote phenotypic diversity. Since habitat complexity may affect population diversity, it is important to understand how population diversity is partitioned across landscapes and among populations. In this study, we examined life history diversity based on size distributions of juvenile Central Valley Chinook salmon (Oncorhynchus tshawytscha) within the Yolo Bypass, a remnant transitional habitat from floodplain to tidal sloughs in the upper San Francisco Estuary (SFE). We used a generalized least squares model with an autoregressive (AR1) correlation structure to describe the distribution of variation in fish size from 1998 to 2014, and tested the effect of two possible drivers of the observed variation: (i) environmental/seasonal drivers within the Yolo Bypass, and (ii) the juvenile Chinook source population within the Sacramento River and northern SFE. We found that the duration of floodplain inundation, water temperature variation, season, and sampling effort influenced the observed time‐specific size distribution of juvenile Chinook salmon in the Yolo Bypass. Given the lack of seasonally inundated habitat and low thermal heterogeneity in the adjacent Sacramento River, these drivers of juvenile size diversification are primarily available to salmon utilizing the Yolo Bypass. Therefore, enhancement of river floodplain‐tidal slough complexes and inundation regimes may support the resilience of imperiled Central Valley Chinook salmon.     

Large‐bodied fish migration and residency in a flood basin of the Sacramento River,California, USA

River–floodplain complexes represent some of the most variable and diverse habitats on earth, yet they are among our planet's most threatened ecosystems. Use of these habitats by large‐bodied fishes is especially poorly understood, particularly in temperate regions. To provide insight into the factors that affect floodplain assemblages and migration, we sampled large‐bodied fishes with a fyke trap for 7 years in the Yolo Bypass, the primary flood basin of the Sacramento River, California. We collected a total of 18,336 individual fish comprised of 27 species, only 41% of which were native. Year‐round resident species white catfish Ameiurus catus, channel catfish Ictalurus punctatus and common carp Cyprinus carpio (all alien species) were the most abundant and comprised 74% of the total catch. Splittail Pogonichthys macrolepidotus (3.8%), white sturgeon Acipenser transmontanus (2.3%) and Sacramento sucker Catostomus occidentalis (1.1%) were the primary native species. We found that seasonal variation in water temperature and flood stage were important factors affecting the fish assemblage structure and the presence of migratory species. American shad Alosa sapidissima, an alien species, showed highest abundance during the early summer upstream migration, when temperatures were warmer. For native species, the abundances of white sturgeon, splittail, Sacramento pikeminnow Ptychocheilus grandis and Sacramento sucker were all highest during flood pulses. While our results suggest that flow alone is not sufficient to control alien species, the strong linkage between native fish migration and flow pulses highlights the importance of river–floodplain connectivity for the conservation of native fishes.     

Enzyme activities in semiarid soils under conservation reserve program,native rangeland,and cropland

There is limited knowledge of biochemical processes in low carbon content soils of semiarid regions under different land use and management. This study investigated several enzyme activities of C, N, P, and S transformations in semiarid soils with different clay (10–21 %) and sand (59–85 %) contents that were under conservation reserve program (CRP), native rangeland (NR), and cropland (CL) under sunflowers (Eriophyllum ambiguum (Gray)), continuous cotton (Gossypium hirsutum L.), or in rotations with wheat (Triticum aestivum L.) or sorghum (Sorghum bicolor L.) in West Texas, USA. Soils under CRP and NR showed higher total C and N contents than cultivated soils under continuous cotton, but soil pH (6.7–8.4) was not affected by the management or land use studied. The activities of β‐glucosidase, β‐glucosaminidase, arylamidase, acid and alkaline phosphatase, phosphodiesterase, and arylsulfatase (mg product (kg soil)^–1 h^–1) were lower in CL under continuous cotton compared to cotton in rotation with other crops, CRP, and NR. The enzyme activities were also lower when compared to soils from other regions. Linear regression analyses indicated positive correlations between enzyme activities and total C (r values up to 0.96, P < 0.01). There was a positive relationship between enzyme activities and total N, but soil pH showed the opposite trend. Enzyme activities were significantly intercorrelated with r values up to 0.98 (P < 0.001). The specific enzyme activities (mg product (g organic C)^–1) were lower in continuous cotton in comparison to the uncultivated soils (i.e., NR and CRP) reflecting differences in organic matter quantity and quality due to cultivation. Among the enzymes studied, the specific activities of β‐glucosidase and arylamidase showed a more pronounced decrease with increasing soil depth. In general, soils under CRP or wheat‐cotton rotations revealed higher enzyme activities than soils under the common agricultural practice for these regions, i.e., continuous cotton under conventional tillage.     

Comparison of two methods to assess the carbon budget of forest biomes in the Former Soviet Union

The sink of CO₂ and the C budget of forest biomes of the Former Soviet Union (FSU) were assessed with two distinct methods: (1) ecosystem/ecoregional, and (2) forest statistical data. The ecosystem/ecoregional method was based on the integration of ecoregions (defined with a GIS analysis of several maps) with soil/vegetation C data bases. The forest statistical approach was based on data on growing stock, annual increment of timber, and FSU yield tables. Applying the ecosystem/ecoregional method, the area of forest biomes in the FSU was estimated at 1426.1 Mha (10⁶ ha); forest ecosystems comprised 799.9 Mha, non-forest ecosystems and arable land comprised 506.1 and 119.9 Mha, respectively. The FSU forested area was 28% of the global area of closed forests. Forest phytomass (i.e., live plant mass), mortmass (i.e., coarse woody debris), total forest plant mass, and net increment in vegetation (NIV) were estimated at 57.9 t C ha^?1, 15.5 t C ha^?1, 73.4 t C ha^?1, and 1.0 t C ha^?1 yr^?1, respectively. The 799.9 Mha area of forest ecosystems calculated in the ecosystem/ecoregional method was close to the 814.2 Mha reported in the FSU forest statistical data. Based on forest statistical data forest phytomass was estimated at 62.7 t C ha^?1, mortmass at 37.6 t C ha^?1; thus the total forest plant mass C pool was 100.3 t C ha^?1. The NIV was estimated at 1.1 t C ha^?1 yr^?1. These estimates compared well with the estimates for phytomass, total forest plant mass, and NIV obtained from the ecosystem/ecoregional method. Mortmass estimated from the forest statistical data method exceeded the estimate based on the ecosystem/ecoregional method by a factor of 2.4. The ecosystem/ecoregional method allowed the estimation of litter, soil organic matter, NPP (net primary productivity), foliage formation, total and stable soil organic matter accumulation, and peat accumulation (13.9 t C ha^?1, 125.0 t C ha^?1, 3.1 t C ha^?1 yr^?1, 1.4 t C ha^?1 yr^?1, 0.11, and 0.056 t C ha^?1 yr^?1, respectively). Based on an average value of NEP (net ecosystem productivity) from the two methods, and following a consideration of anthropogenic influences, FSU forests were estimated to be a net sink of approximately 0.5 Gt C yr^?1 of atmospheric C.     

Induced Ovulation of Southern Flounder Paralichthys lethostigma Using Gonadotropin Releasing Hormone Analogue Implants

Implanted pellets that provide a sustained release of [D-Ala⁶ Des-Gly¹⁰] LHRH-ethylamide (GnRHa) were used to induce maturation and ovulation of Southern flounder Paralichthys lethostigma . Of the 12 females whose ovaries contained follicles with a maximum diameter ≥500 μm, 11 ovulated for the first time within 90 h of hormone implantation. Only 1 fish with a maximum follicle diameter less than 500 μm ovulated within 2 wk after implantation. Ovulated eggs were manually stripped from the females and mixed with sperm from several males. Most females were spawned 1 to 3 times on consecutive days with variable fertility. One female was spawned 11 times producing 668,000 eggs. Fertility was evaluated by examining the incubated eggs for early stages of embryonic cleavage. The percentage of fertile eggs in subsamples of incubated eggs ranged from 7–95%. The results indicate that GnRHa implants can be used to induce repeated ovulation in this species. The variability in fertility is discussed in relation to egg quality.