Seasonal Variations In Biomass Research Articles

Seasonal dynamics of energy and nutrients of Pinus koraiensis seedlings in different successional stages of broadleaved Korean pine forest in Changbai Mountain, China.

We examined the seasonal variations of growth and nutrient accumulation of two-year-old Korean pine (Pinus koraiensis) seedlings in the primary broadleaved Korean pine forest (primary forest) and poplar birch forest (secondary forest) in Changbai Mountain. The seasonal changes of photosynthetically active radiation (PAR), seedling biomass, nonstructural carbohydrate (NSC), total nitrogen (N), and total phosphorus (P) were measured in both forests. The effects of understory light and its seasonal variations in both forests on the growth and nutrient accumulation of understory Korean pine seedlings were also explored. The results showed that the seasonal variations of monthly cumulative PAR under both forests showed a double-peak pattern. In summer, light conditions under the two forests were poor because of the closed canopy. In spring and autumn, light conditions were better due to the deciduous characteristics of canopy broadleaved trees, with light conditions under the secondary forest being obviously better than that of the primary forest. The seasonal variations of biomass, NSC, total N and total P concentrations of Korean pine seedlings in the primary and secondary forests were basically consistent with that of understory light. All those variables increased significantly in spring and autumn, and decreased in summer. In spring, starch concentration increased. In summer, starch and soluble sugar concentrations decreased gradually, and touched bottom in August. In autumn, soluble sugar concentration increased significantly. The biomass and NSC concentration of seedlings under secondary forest were significantly higher than those under primary forest in spring and autumn, but without difference in summer. Therefore, the diffe-rence of understory light conditions in spring and autumn between the two forests might be the key factor driving nutrient accumulation, growth and regeneration of Korean pine seedlings.

Seasonal Variation in Biomass and Production of the Macrophytobenthos in two Lagoons in the Southern Baltic Sea

Baltic coastal lagoons are severely threatened by eutrophication. To evaluate the impact of eutrophication on macrophytobenthos, we compared the seasonal development in macrophytobenthic composition, biomass and production, water column parameters (light, nutrients), phytoplankton biomass and production in one mesotrophic and one eutrophic German coastal lagoon. We hypothesized that light availability is the main driver for primary production, and that net primary production is lower at a higher eutrophication level. In the mesotrophic lagoon, macrophytobenthic biomass was much higher with distinct seasonal succession in species composition. Filamentous algae dominated in spring and late summer and probably caused reduced macrophytobenthic biomass and growth during early summer, thus decreasing vegetation stability. Light attenuation was far higher in the eutrophic lagoon, due to high phytoplankton densities, explaining the low macrophytobenthic biomass and species diversity in every season. Areal net primary production was far lower in the eutrophic lagoon. The “paradox of enrichment” hypothesis predicts lower production at higher trophic levels with increased nutrient concentrations. Our results prove for the first time that this hypothesis may be valid already at the primary producer level in coastal lagoons.

A dynamic biomass model of emergent aquatic vegetation under different water levels and salinity

Emergent aquatic vegetation (EAV) is an important part of wetland ecosystems that provide multiple ecological services. However, human activities and natural changes often influence wetland hydrological regimes such as water levels, salinity, and other factors, which greatly influence the survival and growth of wetland plants. Based on field measurements and control experiments, we developed an EAV model to simulate biomass dynamics under changing conditions of water levels and salinity. This model successfully reproduced the seasonal biomass variation of three typical emergent plants, Phragmites australis, Typha angustifolia and Scirpus mariqueter, and simulated the response of EVA biomass under multiple scenarios of water levels and salinity in the Chongming Dongtan Nature Reserve (CDNR), Shanghai, China. Results suggest that there is a negative correlation between salinity and biomass. An optimal range of water levels are suitable for EAV, and biomass will decrease when the water levels are below or above their optimal range. Applying this dynamic EAV model is a cost-effective approach to find a sustainable and nature-based solution to managing and predicting wetland vegetation changes. The model and approach used in this study may provide a sustainable and nature-based solution for management and protection of wetland ecosystems, and may be transferrable to other wetland systems as well.

Understanding the influence of meteorological parameters on biomass of the forest floor of a small pocket of Forest in Central India

Seasonal variations in biomass of the forest floor were studied in a small pocket of dry deciduous forest in Central India. Pronounced influence of meteorological parameters was observed on the litter fall in the study area. Total litter collected ranged from 26.6 g/m2 in June to 211.3 g/m2 in February. The peak in the litter fall in the present study was found in the winter and spring seasons (Nov to Mar) coinciding with the drought period in dry deciduous forest types. The ratio of the percentage of the different components of litter- leaf litter, wood litter and herbaceous biomass was also found to be influenced by meteorological parameters.

Temporal changes in the composition and biomass of beached pelagic Sargassum species in the Mexican Caribbean

Since 2011, unusually large quantities of pelagic Sargassum fluitans and S. natans (sargasso) have been washing ashore along the coasts of some African countries and the Greater Caribbean, impacting ecosystems and economies. We estimated biomass and composition of sargasso arriving to a Mexican Caribbean coast from September 2016 until May 2020. In 2016, the beached masses comprised S. natans VIII and S. fluitans III. S. fluitans III was the predominant form throughout the study period, comprising on average >60 % of total wet biomass. The relative abundance of S. natans VIII decreased in time from 2016 to 2019 (41 to 3 %), although it became prevalent again in the first months of 2020. The third morphological form, S. natans I, was not registered until February 2018, and its relative abundance increased from 23 % in 2018 to 31 % in 2019. The initial composition of Sargassum species and morphotypes of the beached sargasso in Mexico differed from that commonly reported in the Sargasso Sea. The total biomass of beached sargasso varied considerably among years and seasons, with peaks during the summer months of 2018 and 2019. Seasonal variations in biomass were explained by 1) presence of sargasso in the Yucatan Current and 2) prevailing trade winds. This study is the first report on biomass and species composition of beached sargasso in the Western Caribbean and may help to understand patterns of the massive influxes; which will aid in the management of this new phenomenon.

Dynamics of fungal and bacterial groups and their carbon sources during the growing season of maize in a long-term experiment

The relative contribution of different microbial groups to soil organic matter (SOM) turnover and utilisation of rhizodeposits during a cropping season has remained largely unknown. We used a long-term field experiment (started in 1956), in which C3 crops were replaced with C4 silage maize in 2000, to investigate dynamics of fungi and bacterial groups and their utilisation of ‘young-C4’ and ‘old-C3’ SOM-derived resource every second week during the cropping season (June–Oct). Treatments include bare fallow, unfertilised, fertilised with mineral N and fertilised with farmyard manure (FYM) addition. Extracted soil phospholipid fatty acids (PLFAs) were pooled into Gram-positive, Gram-negative bacteria and fungi (18:2ω6,9) groups and their δ13C values determined. Total PLFAs amount correlated to the SOM contents (highest in FYM) and increased over the cropping season in N-fertilised and FYM treatments. As a result of a peak in plant growth during a period with frequent rain events in August, δ13C of total PLFAs significantly increased from − 23.8 to − 21.6‰ and − 26.1 to − 24.7‰, in N-fertilised and FYM addition, respectively. This clearly indicated a shift in microbial utilisation from old to young SOM sources, which was linked to increased soil moisture contents and fungal biomass. The abundance of Gram-positive increased and that of Gram-negative bacteria decreased until August and vice versa thereafter. The mean δ13C values of individual microbial groups were highest in fungi (corresponding to their seasonal biomass variation) followed by Gram-positive and Gram-negative bacteria. The results clearly demonstrated that irrespective of fertilisation type, fungi were the main players in seasonal SOM dynamics and were strongly influenced by soil moisture and phenological stage of the maize (i.e. rhizodeposition). Disentangling these microbial controls on C resources utilisation will be crucial for understanding C cycling during a cropping season or on an ecosystem scale.

Community structured production of zooplankton in the eastern boundary upwelling system off central/southern Chile (2003–2012)

AbstractEastern boundary upwelling systems (EBUS) are highly productive and climatically sensitive ecosystems of the ocean. A critical component sustaining EBUS is the zooplankton secondary production (ZSP) which links primary production (PP) and the higher trophic levels. However, estimating ZSP is a complex task and many questions remain regarding its controlling factors. Here, we used automated analysis to assess taxonomic-structured biomass of zooplankton from a time series (2003–2012) at a fixed station off central-southern Chile. Zooplankton biomasses combined with empirically estimated growth rates, as a function of temperature, Chorophyll-a concentration, and body size, were used to estimate seasonal and interannual changes in ZSP. The annual integrated ZSP yielded a mean of 8.0 g C m−2 y−1, with a minimum in 2009 of 5.7 g C m−2 y−1 and a maximum in 2011 of 13 g C m−2 y−1, and an average annual P/B ratio of 35. The transfer efficiency from PP to ZSP was only 0.8%, indicating a surplus of PP to the system and/or the importance of intermediate microzooplankton levels. Seasonal variation in biomass, ZSP and the P/B ratio were explained mostly by changes in taxonomic structure while interannual variation reflected large-scale climatic changes, such as the Pacific decadal oscillation.

Seasonal Dynamics of Microbial Biomass in Soddy-Podzolic Soil

The seasonal dynamics of the structure of microbial biomass in a soddy-podzolic soil under fallow was assessed using luminescent microscopy. Samples from three soil horizons (P, 5‒15 cm, BEL, 30‒40 cm, and BT2, 50‒60 cm) were sampled monthly from March, 2017 to February, 2018, in the territory of Eldigino experimental station (Moscow oblast). In addition to microbial biomass measurement, soil temperature and moisture were recorded. The microbial biomass at all sampling times was dominated by fungi (up to 93%). Minimal microbial population and biomass were observed in the period from November to March. The biomass of prokaryotes increased twofold in May, the maximal values were observed in August and September. The length of actinomycete mycelium was maximal in July and August, when the soil water content was the lowest. Maximal fungal biomass was observed in July and September. Seasonal changes of microbial biomass were most pronounced in the upper soil horizon P, while they were more even in the BEL and BT horizons. Using regression analysis, we revealed a significant effect of temperature and sampling depth on the fungal and prokaryotic biomass. The results indicate substantial seasonal variations in biomass of soil microbiota, which should be taken into account when comparing soils sampled at different seasons.

Circulation patterns in a shallow tropical reservoir: Observations and modeling

The diurnal circulation pattern is deduced in Kranji Reservoir, a shallow, elongated tropical reservoir in Singapore via field observations and results from the 3-D Estuary, Lake, and Coastal Ocean Model (ELCOM) model for the month of July 2012 which is during Singapore’s Southwest Monsoon season. Detailed comparisons of the modeled temperature and velocity fields with field measurements during a dry period of July 21–26 2012 without rainfall or inflow events are presented in terms of point comparisons, longitudinal profiles and cross-reservoir transverse velocity profile, thus providing a good representation of the flow field. Both observation and modeling show that the diurnal circulation pattern is driven by wind and by temperature gradients due to upwelling which depend on the time of the day. There is a daytime circulation pattern characterized by one large loop along the main channel, and a nighttime circulation characterized by two loops: one large loop between the reservoir dam and a location K1 (2500 m upstream from the dam where inflow tributary flows merge), and one small loop between K1 and the tributaries. These circulation patterns are consistent with the observed horizontal distribution of chlorophyll a during the Southwest Monsoon months over years 2008–2012. High chlorophyll a concentration occurs near the dam as expected due to downwelling within the large circulation loop and also close to the tributaries due to the nutrient from the catchments being trapped within the smaller loop. These results demonstrate the contributing effect of hydrodynamic flow on the biomass distribution that can occur in shallow tropical systems and which affects the diurnal and seasonal variation of biomass for such systems.

Mesopelagic Sound Scattering Layers of the High Arctic: Seasonal Variations in Biomass, Species Assemblage, and Trophic Relationships

Mesopelagic sound scattering layers (SSL) are ubiquitous in all oceans. Pelagic organisms within the SSL play important roles as prey for higher trophic levels and in climate regulation through the biological carbon pump. Yet, the biomass and species composition of SSL in the Arctic Ocean remain poorly documented, particularly in winter. A multifrequency echosounder detected a SSL north of Svalbard, from 79.8°N to 81.4°N, in January 2016, August 2016, and January 2017. Midwater trawl sampling confirmed that the SSL comprised zooplankton and pelagic fish of boreal and Arctic origins. Juvenile beaked redfish dominated the fish assemblage in January and Arctic cod in August. The macrozooplankton community mainly comprised the medusa Cyanea capillata, the amphipod Themisto libellula, and the euphausiids Meganyctiphanes norvegica in August and Thysanoessa inermis in January. The SSL was located in the Atlantic Water mass, between 200-700 m in August and between 50-500 m in January. In January, the SSL was shallower and weaker above the deeper basin, where less Atlantic Water penetrated. The energy content available in the form of lipids within the SSL was significantly higher in summer than winter. The biomass within the SSL was >12-fold higher in summer, and the diversity of fish was slightly higher than in winter (12 vs. 9 species). We suggest that these differences are mainly related to life history and ontogenetic changes resulting in a descent towards the seafloor, outside the mesopelagic layer, in winter. In addition, some fish species of boreal origin, such as the spotted barracudina, did not seem to survive the polar night when advected from the Atlantic into the Arctic. Others, mainly juvenile beaked redfish, were abundant in both summer and winter, implying that the species can survive the polar night and possibly extend its range into the high Arctic. Fatty-acid trophic markers revealed that Arctic cod mainly fed on calanoid copepods while juvenile beaked redfish targeted krill (Thysanoessa spp.). The relatively high biomass of Arctic cod in August and of redfish in January thus suggests a shift within the SSL, from a Calanus-based food web in summer to a krill-based food web during winter.

北部湾近岸海域浮游动物群落结构特征及季节变化

PDF HTML阅读 XML下载 导出引用 引用提醒 北部湾近岸海域浮游动物群落结构特征及季节变化 DOI: 10.5846/stxb201807191553 作者: 作者单位: 广西壮族自治区海洋环境监测中心站,广西壮族自治区海洋环境监测中心站,广西壮族自治区海洋环境监测中心站,广西壮族自治区海洋环境监测中心站 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金项目（41466001）；广西科技计划项目（桂科AA17129001，桂科AD17129041，桂科AB16380340） Community structure and seasonal variation of zooplankton in coastal Beibu Gulf Author: Affiliation: Marine Environmental of Monitoring Center of Guangxi,Marine Environmental of Monitoring Center of Guangxi,Marine Environmental of Monitoring Center of Guangxi,Marine Environmental of Monitoring Center of Guangxi Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:2017年3月（枯水期）、7月（丰水期）和10月（平水期）分别对北部湾近岸海域44个站位的浮游动物进行了调查。结果共检出浮游动物251种和浮游幼体24类，其中枯水期138种（类），丰水期134种（类），平水期191种（类），分属河口低盐、近岸暖温、近岸暖水和外海暖水4个生态类群。优势种9种，其中枯水期以原生动物占绝对优势，丰水期以枝角类、桡足类和浮游幼体类占优势，平水期以十足类和浮游幼体类占优势。浮游动物丰度年均值为789.95个/m3，呈现出枯水期（1540.19个/m3）明显高于平水期（457.58个/m3）和丰水期（372.08个/m3）的季节变化特征；浮游动物生物量年均值为252.40 mg/m3，生物量的季节变化与丰度变化不一致，平水期生物量（385.01 mg/m3）明显高于枯水期（221.41 mg/m3）和丰水期（150.78 mg/m3）。多样性指数平水期最高（3.16），丰水期（2.35）次之，枯水期（2.22）最低。枯水期和丰水期北部湾近岸海域浮游动物生物量和丰度水平分布特征基本呈现自河口近岸海域向外海递增的趋势，平水期浮游动物生物量与丰度的空间分布较为均匀。浮游动物的种类组成结构以及优势种的演替对浮游动物的生物量和丰度季节变化有着重要的决定作用。径流导致的悬浮物、营养盐等的变化可能是决定北部湾近岸海域浮游动物生物量和丰度空间分布的主要因素。研究还表明与其他海湾相比，北部湾近岸海域浮游动物群落结构趋于小型化，需加大关注。 Abstract:A comprehensive investigation on the population of zooplankton was conducted at 44 stations in the Beibu Gulf coastal area in the dry,wet and normal seasons in 2017. In total,251 zooplankton species including 24 larvae were identified during the investigation,among which 138,134,and 191 species occurred in the dry,wet and normal seasons,respectively. All zooplankton could be grouped into four ecotypes:estuary,offshore warm-water, offshore warm-temperature and eurytopic. There were 9 dominant species during the sampling period,with protozoa dominating the community in dry season,Cladocera,Copepoda and pelagic larvae dominating in the wet season, Decapoda and pelagic larvae in the normal season.The annual average abundance of zooplankton was 789.95 ind./m3. Dry season had the largest abundance (1540.19 ind./m3), followed by normal (457.58 ind./m3) and wet (372.08 ind./m3) seasons. The annual average biomass of zooplankton was 252.40 mg/m3, with the highest biomass during normal season (385.01 mg/m3),followed by dry (221.41 mg/m3) and wet (150.78 mg/m3) seasons.The highest diversity index (3.16) was found in normal season, followed by wet season (2.35), while the least diversity (2.22) presented in the dry season. Both the horizontal distribution of biomass and abundance of zooplankton increased gradually moving offshore in dry and wet seasons, while remaining relatively evenly distributed in normal season. Seasonal variation of biomass and abundance was determined by composition and dominant species. Correlation analysis shows that the distribution of biomass and abundance of zooplankton in the coastal waters of Beibu gulf are influenced by suspended matter and nutrients. Compared with the other bays, the population structure of zooplankton in the coast of the Beibu Gulf exhibited a clear tendency toward miniaturization that require additional attention. 参考文献 相似文献 引证文献

Assessment of spatial and seasonal biomass variation of intertidal seaweed species with commercial potential use as basis for future tailored standing stocks management

Assessment of spatial and seasonal biomass variation of intertidal seaweed species with commercial potential use as basis for future tailored standing stocks management

Seasonality in coastal macrobenthic biomass and its implications for estimating secondary production using empirical models

AbstractMacrobenthic secondary production is widely used to assess the trophic capacity, health, and functioning of marine and freshwater ecosystems. Annual production estimates are often calculated using empirical models and based on data collected during a single period of the year. Yet, many ecosystems show seasonal variations. Although ignoring seasonality may lead to biased and inaccurate estimates of annual secondary production, it has never been tested at the community level. Using time series of macrobenthic data collected seasonally at three temperate marine coastal soft‐bottom sites, we assessed seasonal variations in biomass of macrobenthic invertebrates at both population and community levels. We then investigated how these seasonal variations affect the accuracy of annual benthic production when assessed using an empirical model and data from a single sampling event. Significant and consistent seasonal variations in biomass at the three study sites were highlighted. Macrobenthic biomass was significantly lower in late winter and higher in summer/early fall for 18 of the 30 populations analyzed and for all three communities studied. Seasonality led to inaccurate and often biased estimates of annual secondary production at the community level when based on data from a single sampling event. Bias varied by site and sampling period, but reached ∼ 50% if biomass was sampled at its annual minimum or maximum. Since monthly sampling is rarely possible, we suggest that ecologists account for uncertainty in annual production estimates caused by seasonality.

Changes in plant biomass induced by soil moisture variability drive interannual variation in the net ecosystem CO2 exchange over a reclaimed coastal wetland

Changes in the timing and magnitude of precipitation is a threat to agricultural productivity and farmland carbon stocks. However, the relationship between inter-annual variations in precipitation and net ecosystem CO2 exchange (NEE) remains to be clarified, particularly when combined with water-salt transport in reclaimed coastal wetland. Here, based on the eddy-covariance technique, we investigated the interannual variation in carbon dioxide exchange and its control mechanism over a reclaimed coastal wetland of the Yellow River Delta from 2010 to 2014. The coastal wetland functioned as a strong sink for atmospheric CO2, with the annual NEE of −229, −175, −142, −92 and −80 g C m−2 in the 5 years from 2010 to 2014, respectively. Surprisingly, we find that large annual variation in net ecosystem exchange (NEE) can be predicted accurately using plant biomass. Plant biomass was driven by soil water content (SWC), with about 48%–80% seasonal variation of biomass attributed to SWC. During the early growing stage, high SWC accompanied with low salinity promoted plant biomass and NEE. While high SWC accompanied with increased waterlogged stress inhibited plant biomass and NEE during the middle growing stage. The same results were also observed in a field manipulation experiment over a nearby natural coastal wetland. Our study indicated that extreme climate accompanied with extreme drought and flooding may decrease carbon sequestration capacity of the reclaimed coastal wetland due to the increase in salinity.

Estimating areal carbon fixation of intertidal macroalgal community based on composition dynamics and laboratory measurements

The community dynamics and potential carbon fixation of intertidal macroalgae were investigated monthly from April 2014 to April 2015 in the northwest coast of Yellow Sea. Seasonal variations in biomass and carbon fixation were presented and showed close relationship with community structure. The carbon fixation rate ranged from 0.48±0.13 mg C/(gFW·d) to 4.35±0.12 mg C/(gFW·d). Sargassum thunbergii, Chondrus ocellatus and Ulva intestinalis were three most influential species which contributed 27%, 21.9% and 18.5% variation of carbon fixation rate, respectively. Standing carbon stocks ranged from 7.52 gC/m2 to 41.31 gC/m2, and estimated carbon stocks varied from 11.77 gC/m2 to 96.49 gC/m2. The larger difference between estimated and standing carbon stocks implied that more fixed carbon was exported from the community in summer and autumn than in winter. This study suggested that intertidal macroalgal community could provide a potential function in carbon fixation of coastal ecosystem.

Satellite remote sensing reveals a positive impact of living oyster reefs on microalgal biofilm development

Abstract. Satellite remote sensing (RS) is routinely used for the large-scale monitoring of microphytobenthos (MPB) biomass in intertidal mudflats and has greatly improved our knowledge of MPB spatio-temporal variability and its potential drivers. Processes operating on smaller scales however, such as the impact of benthic macrofauna on MPB development, to date remain underinvestigated. In this study, we analysed the influence of wild Crassostrea gigas oyster reefs on MPB biofilm development using multispectral RS. A 30-year time series (1985–2015) combining high-resolution (30 m) Landsat and SPOT data was built in order to explore the relationship between C. gigas reefs and MPB spatial distribution and seasonal dynamics, using the normalized difference vegetation index (NDVI). Emphasis was placed on the analysis of a before–after control-impact (BACI) experiment designed to assess the effect of oyster killing on the surrounding MPB biofilms. Our RS data reveal that the presence of oyster reefs positively affects MPB biofilm development. Analysis of the historical time series first showed the presence of persistent, highly concentrated MPB patches around oyster reefs. This observation was supported by the BACI experiment which showed that killing the oysters (while leaving the physical reef structure, i.e. oyster shells, intact) negatively affected both MPB biofilm biomass and spatial stability around the reef. As such, our results are consistent with the hypothesis of nutrient input as an explanation for the MPB growth-promoting effect of oysters, whereby organic and inorganic matter released through oyster excretion and biodeposition stimulates MPB biomass accumulation. MPB also showed marked seasonal variations in biomass and patch shape, size and degree of aggregation around the oyster reefs. Seasonal variations in biomass, with higher NDVI during spring and autumn, were consistent with those observed on broader scales in other European mudflats. Our study provides the first multi-sensor RS satellite evidence of the promoting and structuring effect of oyster reefs on MPB biofilms.

Spatial and temporal variability in the potential of river water biofilms to degrade p-nitrophenol

In order to predict the fate of chemicals in the environment, a range of regulatory tests are performed with microbial inocula collected from environmental compartments to investigate the potential for biodegradation. The abundance and distribution of microbes in the environment is affected by a range of variables, hence diversity and biomass of inocula used in biodegradation tests can be highly variable in space and time. The use of artificial or natural biofilms in regulatory tests could enable more consistent microbial communities be used as inocula, in order to increase test consistency. We investigated spatial and temporal variation in composition, biomass and chemical biodegradation potential of bacterial biofilms formed in river water. Sampling time and sampling location impacted the capacity of biofilms to degrade p-nitrophenol (PNP). Biofilm bacterial community structure varied across sampling times, but was not affected by sampling location. Degradation of PNP was associated with increased relative abundance of Pseudomonas syringae. Partitioning of the bacterial metacommunity into core and satellite taxa revealed that the P. syringae could be either a satellite or core member of the community across sampling times, but this had no impact on PNP degradation. Quantitative PCR analysis of the pnpA gene showed that it was present in all samples irrespective of their ability to degrade PNP. River biofilms showed seasonal variation in biomass, microbial community composition and PNP biodegradation potential, which resulted in inconsistent biodegradation test results. We discuss the results in the context of the mechanisms underlying variation in regulatory chemical degradation tests.

Tecnologia GNSS de baixo custo na monitorização de ovinos em pastoreio

Extensive livestock production is supported by natural and biodiverse pastures, characterized by marked seasonal variation of biomass, plant species and growth stage. The use of the food resources and the occupation of grazing space can be very heterogeneous in such conditions due to ruminants grazing behaviour. Successful grazing and pasture management requires an understanding of the adjustment mechanism behind the grazing behaviour that enables adaptation to grazing conditions. Use of GNSS technology allows grazing data collection but although available, is expensive, limiting its application for research purposes. This paper reviews the principles for the application of this technology and was designed to study the use of inexpensive commercial GNSS receptors (commercial of the shelf - COTS: CatTrackTM). Six receivers were used for six period’s collection data over two months of continuous grazing on a natural pasture. The accuracy of the receivers is 14m and 40m in static and dynamic tests, respectively. The precision was 3m and the reliability 80%. The tested equipment differentiates between animal activities (grazing, resting and transit). It also determines sheep locations, allowing the characterization of patterns, pathways and preferred areas. It is concluded that the COTS equipment has a high quality / price ratio, so it can become an important tool to support the decisions that are essential to a more precise pasture management.

Diversidad y biomasa de macroinvertebrados asociados a cuatro tipos de sustratos en la laguna La Virginia, páramo Sumapaz

For macroinvertebrates inhabiting lentic systems, quantity and availability of various substrates are important for the establishment and development of different assemblages, also, the biome reflects macroinvertebrates system production. In this study, the diversity was estimated from the biomass present in the four substrates: macrophyte ( Myriophyllum aquaticum ), rock, sediments and organic matter, it was analyzed the seasonal variation of biomass and abundance considering three hydrological periods. It was collected 2.957 individuals grouped in 17 genera and 11 orders. Helobdella was the dominant taxon, it contributes to 90% of the total biomass of the community; Hyalella , Tanytarsus and Centrocorisa were important too. Electric conductivity, sulfates and the water temperature were determined for the biomass. The dominance of macroinvertebrates was higher in macrophyta (0,99). In the rest of the substrates, diversity was larger (iŸƒ = 1,5 nats.ind-1) and the evenness minor (iŸƒ = 0,24). There are significant differences in the registers of biomass among the substrates but not among the campaigns. In conclusion, macrophyte was the substrate and the habitat most used by macroinvertebrates and it contains more individuals; however, the macrophyte was not the most diversity substrates because, when it was compared with other three substrates the diversity is higher.

The community structure and seasonal dynamics of plankton in Bange Lake, northern Tibet, China

The seasonal variations in biomass, abundance, and species composition of plankton in relation to hydrography were studied in the saline Bange Lake, northern Tibet, China. Sampling was carried out between one to three times per month from May 2001 to July 2002. Salinity ranged from 14 to 146. The air and water temperature exhibited a clear seasonal pattern, and mean annual temperatures were approximately 4.8°C and 7.3°C, respectively. The lowest water temperature occurred in winter from December to March at -2°C and the highest in June and July at 17.7°C. Forty-one phytoplankton taxa, 21 zooplankton, and 5 benthic or facultative zooplankton were identified. The predominant phytoplankton species were Gloeothece linearis, Oscillatoria tenuis, Gloeocapsa punctata, Ctenocladus circinnatus, Dunaliella salina, and Spirulina major. The predominant zooplankton species included Holophrya actra, Brachionus plicatilis, Daphniopsis tibetana, Cletocamptus dertersi, and Arctodiaptomus salinus. The mean annual total phytoplankton density and biomass for the entire lake were 4.52×107 cells/L and 1.60 mg/L, respectively. The annual mean zooplankton abundance was 52, 162, 322, and 57, 144 ind./L, in the three sublakes. The annual mean total zooplankton biomass in Lakes 1–3 was 1.23, 9.98, and 2.13 mg/L, respectively. The annual mean tychoplankton abundances in Bg1, 2, and 3 were 47, 67, and 654 ind./L. The annual mean tychoplankton biomass was 2.36, 0.16, and 2.03 mg/L, respectively. The zooplankton biomass (including tychoplankton) in the lake was 9.11 mg/L. The total number of plankton species in the salt lake was significantly negatively correlated with salinity.