The growth of external AM fungal mycelium in sand dunes and in experimental systems

We estimated the biomass and growth of arbuscular mycorrhizal (AM) mycelium in sand dunes using signature fatty acids. Mesh bags and tubes, containing initially mycelium-free sand, were buried in the field near the roots of the dune grass Ammophila arenaria L. AM fungal mycelia were detected at a distance of about 8.5 cm from the roots after 68 days of growth by use of neutral lipid fatty acid (NLFA) 16:1ω5. The average rate of mycelium extension during September and October was estimated as 1.2 mm day⁻¹. The lipid and fatty acid compositions of AM fungal mycelia of isolates and from sand dunes were analysed and showed all to be of a similar composition. Phospholipid fatty acids (PLFAs) can be used as indicators of microbial biomass. The mycelium of G. intraradices growing in glass beads contained 8.3 nmol PLFAs per mg dry biomass, and about 15% of the PLFAs in G. intraradices, G. claroideum and AM fungal mycelium extracted from sand dunes, consisted of the signature PLFA 16:1ω5. We thus suggest a conversion factor of 1.2 nmol PLFA 16:1ω5 per mg dry biomass. Calculations using this conversion factor indicated up to 34 μg dry AM fungal biomass per g sand in the sand dunes, which was less than one tenth of that found in an experimental system with Glomus spp. growing with cucumber as plant associate in agricultural soil. The PLFA results from different systems indicated that the biomass of the AM fungi constitutes a considerable part of the total soil microbial biomass. Calculations based on ATP of AM fungi in an experimental growth system indicated that the biomass of the AM fungi constituted approximately 30% of the total microbial biomass. This revised version was published online in June 2006 with corrections to the Cover Date.     

Spatial Subtidal Macrobenthic Distribution in Relation to Abiotic Conditions in the Lima Estuary, NW of Portugal

During the summer of 2002, sampling was carried out in the Lima estuary in order to compare the pattern of the macrobenthic community’s distribution in relation to physical and chemical variables. A total of 54 macrobenthic taxa were identified. Abundance, biomass and specific diversity varied among the twenty stations. Abundance ranged from 212 to 9856 ind./m², with an average of 1581 ind./m². Abra alba presented the highest density corresponding to 39.1% of the total specimens gathered, followed by Hediste diversicolor with 31.5%. Biomass ranged from 0.12 to 264.62 g AFDW/m², with an average of 17.58 g AFDW/m². Cerastoderma edule and A. alba were the species with a clear predominance in the total biomass, contributing 75.3 and 13.8%, respectively. The multivariate techniques used revealed a macrobenthic community with five distinct groups, particularly related to the sedimentological characteristics and salinity. These results demonstrated significant differences in macrobenthic assemblage’s composition along an estuarine gradient. For the first time the presence of the nonindigenous invasive species Corbicula fluminea was described in this estuary.     

The structure of the plankton community of the Öregrundsgrepen (southwest Bothnian Sea)

Taxonomic composition and variations in density and biomass of the plankton community in the Öregrundsgrepen, a shallow coastal area, were investigated from June 1972 to November 1973. The phytoplankton biomass was large in spring but small during the rest of the year. The spring bloom was dominated by diatoms and dinoflagellates, especially byThalassiosira spp. which were also important during other seasons. Small forms, such asCryptomonas spp.,Rhodomonas spp. and monads, dominated during summer. Blue-green algae were never of any major importance. During the summer, the trophogenic layer exceeded 10 m in thickness. The metazoan fauna was of lower diversity than the plankton flora. The dominating species, the copepodsAcartia bifilosa andEurytemora affinis, constituted on the average 83% of the standing crop. The low salinities, 5–6 S, were regarded as the principal pertinent limiting factor. The metazoan fauna reached large biomass values from July to October. The protozoan fauna (in the case of ciliates), obtained biomass maxima during the spring bloom. It is suggested that the Öregrundsgrepen represents an area of elevated productivity within a region of low overall production, presumably due to local upwelling. From June 1972 to May 1973, the average biomasses were: phytoplankton 0.464 g C m^–2, ciliates 0.040 g C m^–2, copepod nauplii 0.010 g C m^–2, micro-rotifers 0.004 g C m^–2, and mesozooplankton (larger than 0.2 mm) 0.312 g C m^–2. It is estimated that about than 60% of the phytoplankton production is consumed by the microzooplankton (<0.2 mm).     

Macrobenthic Distribution within the Sediment along an Estuarine Salinity Gradient

The distribution of the macrobenthic infaunal community within the upper 25 cm of the sediment was studied at 16 stations in the lower Chesapeake Bay. Stations were located from the tidal freshwater to the polyhaline zone of major tributaries (James, York and Rappahannock Rivers) and in the polyhaline portion of the lower bay mainstem. Profiles for total number of individuals, total ash-free dry weight biomass and species encountered with depth were calculated. Except for the deep dwelling bivalve, Macoma balthica, tributary macrobenthic communities had a shallow depth distribution compared to the mainstem sites which were found in generally coarser sediments in the higher salinity region of the estuary.     

长江口潮下带春季大型底栖动物的群落结构

2005年4月对长江口全区域潮下带共10个采样站位的大型底栖动物进行了调查。调查采获大型底栖动物38种,分属5个生态类型,种类数较少,河口外缘站位种类数多于口内站位。各站位大型底栖动物的平均丰度为32.9个/m2、平均生物量为5.035g/m2(湿重);与20世纪七八十年代相比,平均生物量显著降低;口外缘站位的总丰度和总生物量均高于口内站位。环境因子相关分析表明,盐度是决定长江口大型底栖动物种类分布最重要的环境因子。群落聚类、标序分析显示,春季长江口潮下带大型底栖动物群落结构空间分异明显,完全符合目前长江口支、港、槽“三级分汊”的空间格局。其中,北支的大型底栖动物以混合高盐水种类为主,而南支则以淡水和半咸水种类为主。南支的南北槽分界处内外站位的群落差异也由盐度决定,因为靠近口内的群落均受长江冲淡水影响较大;而口外站位群落则受咸淡水影响。南支的南北港分界点内外的群落差异则主要受长江来水的影响,原因在于处在港分界点以内的群落所在区域,直接受长江来水的冲刷,底质环境极不稳定;而港、槽分界点之间的群落所在区域由于河口上段的诸多明暗沙体的阻挡,水势较为稳定,所以底质环境较稳定,从而使得港、槽分界点之间的群落出现了更多的沙蚕等底质环境类型种类。     

The Seasonal Dynamics and Composition of Photosynthetic Picoplankton Communities in Temperate Lakes in Ontario,Canada

The seasonal abundance and composition of photosynthetic picoplankton (0.2-2 μm) was compared among five oligotrophic to mesotrophic lakes in Ontario. Epilimnetic picocyanobacteria abundance followed a similar pattern in all lakes; maximum abundance (2-4 × 10⁵ cells · ml⁻¹) occurred in late summer following a period of rapid, often exponential increase after epilimnetic temperatures reached 20 °C. In half of the lakes picocyanobacteria abundance was significantly correlated with temperature, while in other lakes the presence of a small spring peak resulted in a poor correlation with temperature. In all lakes there was a significant correlation between epilimnetic abundance and day of the year. Correlations with water chemistry parameters (soluble reactive phosphorus, total phosphorus, particulate C: P and C: N) were generally weaker or insignificant. However, in the three lakes with the highest spring nitrate concentrations, a significant negative correlation with nitrate was observed. During summer stratification, picocyanobacteria abundance reached a maximum within the metalimnion and at or above the euphotic zone (1% of incident light) in all lakes. These peaks were not related to nutrient gradients. The average total phytoplankton biomass ranged from 0.5 g m⁻³ (wet weight) in the most oligotrophic lake to 1.4 g m⁻³ for the most mesotrophic with picoplankton biomass ranging from 0.01 g m⁻³ to 0.3 g m⁻³. Picocyanobacteria biomass comprised 1 to 9 % of total phytoplankton biomass in late summer, but in one year for one lake represented a maximum of 56%. Other photosynthetic picoplankton (unidentified eukaryotes, Chlorella spp. Nannochloris spp.), although less abundant (10³ cells · ml⁻¹) than picocyanobacteria, represented biomass equal or greater than that of the picocyanobacteria in spring and early summer. On average, half of the photosynthetic picoplankton biomass was eukaryotic in the more coloured lakes, while in the clear lakes less than 20% was eukaryotic. Among the lakes there was a significant positive correlation between the average light extinction coefficient and the proportion of eukaryotic biomass of the picoplankton. In mesotrophic Jack's Lake, the contribution of picoplankton to the maximum photosynthetic rate ranged from 10 to 47% with the highest values in the spring (47%) and late summer (33%), as a result of eukaryotic picoplankton and picocyanobacteria respectively. Picocyanobacteria cell specific growth rates were high during July (0.6-0.8 day⁻¹) and losses were close to 80% of the growth rate. Thus, despite low biomass, photosynthetic picoplankton populations appeared to turn over rapidly and potentially contributed significantly to planktonic food webs in early spring and late summer.     

Seasonal variation in the energy content of benthic macroinvertebrates of Lake Nainital,U.P., India

The paper discusses seasonal variation in the energy contents of four macrobenthic invertebrates of Lake Nainital during 1977–78. The energy values varied from 16971–19437 J/g dry weight in Tubifex tubifex, 16 511–20 231 J/g dry weight in Glossiphonia weberi, 19 019–25 289 J/g dry weight in Chironomus plumosus and 19 583–20 549 J/g dry weight in Viviparus bengalensis. The former two genera exhibited highest energy contents during summer, whereas the latter two revealed highest values during winter. On mean annual basis, the highest values were recorded for C. plumosus and lowest for T. tubifex. In V. bengalensis, variation occurred in ash fraction (%) and in energy values (Joule per gram dry weight) but not in energy values of organic fraction (Joule per gram ash-free dry weight), while the other three genera displayed variation in all three variables.     

Aquatic macroinvertebrate community structure of aNymphoides peltata-dominated and macrophyte-free site in an oxbow lake

The aquatic macroinvertebrates in two freshwater biotopes,viz. aNymphoides peltata-dominated site and a macrophyte-free site, were studied quantitatively in a shallow alkaline oxbow lake of the river Waal, the main branch of the river Rhine in The Netherlands. The research comprised the analysis of water, sediment and macrophyte samples.In the macrophyte-free site Oligochaeta and Nematocera, particularly of the collector gatherer functional feeding group, dominated the prevailing benthic community. The total macroinvertebrate biomass ranged here from 0.3 to 0.9 g ash-free dry weight per m² of biotope.Species richness, densities, and biomass of macroinvertebrates were considerably higher in the biotope dominated byNymphoides peltata. Many taxa were found associated with the aboveground macrophyte. The sediment compartment, however, contributed most to the total density and biomass of macroinvertebrates. Nematocera and Oligochaeta were the most abundant fauna groups, whereas the largest share in total biomass was provided by clams (Mollusca). The biomass of the total macroinvertebrate community in theNymphoides-dominated site ranged from 6.2 to 7.5 g ash-free dry weight per m² of biotope. The biomass of the aboveground phytophilous fauna ranged from 0.1 to 0.6 g ash-free dry weight per m² of biotope. In September, when theNymphoides peltata vegetation was in its senescent phase, the largest numbers and the highest biomass of phytophilous macroinvertebrates were observed. The contribution of the shredder functional feeding group was high in this period. This, and the overall high abundance of fauna with a detritivorous mode of life, indicates the importance of macrophyte detritus as input to food chains.     

Earthworm secondary production and N flux in agroecosystems: a comparison of two approaches

Production was estimated for Aporrectodea spp. and Lumbricus spp. populations in corn agroecosystems with a 5-year history of manure or inorganic fertilizer applications during 1994–1995 and 1995–1996. Earthworm biomass and production were greater in manure than inorganic fertilizer plots, although biomass and production declined by about 50% between 1994–1995 and 1995–1996 due to unfavorable climatic conditions. Production was highest during the spring and autumn when soil temperatures were between 4 and 22°C. Production was higher in Lumbricus spp. than Aporrectodea spp. populations due to greater Lumbricus spp. biomass. Aporrectodea spp. production was 3.47–16.14 g ash-free dry weight (AFDW) m^–2 year^–1, while Lumbricus spp. production was 6.09–18.11 g AFDW m^–2 year^–1, depending on the fertilizer treatment and the method used to estimate production. However, production estimates from the instantaneous growth rate method were within 27% of the values calculated using the size-frequency method. Nitrogen flux through earthworms was used to estimate efficiency quotients. Net production efficiency (P/A) ranged from 0.64 to 0.76, assimilation efficiency (A/C) ranged from 0.1 to 0.3, and gross production efficiency (P/C) ranged from 0.06 to 0.22. Annual N flux through earthworm populations was higher in manure than inorganic fertilizer plots, and ranged from 2.95 to 5.47 g N m^–2 year^–1 in 1994–1995 and 1.76 to 2.92 g N m^–2 year^–1 in 1995–1996. The N flux through earthworms represented an amount equivalent to 16–30% of crop N uptake during 1994–1995 and 11–18% of crop N uptake during 1995–1996. We concluded that the effects of earthworms on N cycling in corn agroecosystems were substantial, and that N flux through earthworms was influenced significantly by fertilizer amendments. Received: 20 September 1999 / Accepted: 24 March 2000     

Extraction of hydrocarbons from freshwater green microalgae (Botryococcus sp.) biomass after phycoremediation of domestic wastewater

This study was undertaken to analyze the efficiency of Botryococcus sp. in the phycoremediation of domestic wastewater and to determine the variety of hydrocarbons derived from microalgal oil after phycoremediation. The study showed a significant (p < 0.05) reduction of pollutant loads of up to 93.9% chemical oxygen demand, 69.1% biochemical oxygen demand, 59.9% total nitrogen, 54.5% total organic carbon, and 36.8% phosphate. The average dry weight biomass produce was 0.1 g/L of wastewater. In addition, the dry weight biomass of Botryococcus sp. was found to contain 72.5% of crude oil. The composition analysis using Gas Chromatogram - Mass Spectrometry (GC-MS) found that phthalic acid, 2-ethylhexyltridecyl ester (C₂₉H₄₈O₄), contributed the highest percentage (71.6%) of the total hydrocarbon compounds to the extracted algae oil. The result of the study suggests that Botryococcus sp. can be used for effective phycoremediation, as well as to provide a sustainable hydrocarbon source as a value-added chemical for the bio-based plastic industry.     

Production ecology of phyto- and zooplankton in a eutrophic pond dominated byChaoborus flavicans (Diptera: Chaobolidae)

Primary production of phytoplankton and secondary production of a daphnid and a chaoborid were studied in a small eutrophic pond. The gross primary production of phytoplankton was 290 gC m⁻² per 9 months during April–December. Regression analysis showed that the gross primary production was related to the incident solar radiation and the chlorophylla concentration and not to either total phosphorus or total inorganic nitrogen concentration. The mean chlorophylla concentration (14.2 mg m⁻³), however, was about half the expected value upon phosphorus loading of this pond. The mean zooplankton biomass was 1.60 g dry weight m⁻², of whichDaphnia rosea and cyclopoid copepods amounted to 0.69 g dry weight m⁻² and 0.61 g dry weight m⁻², respectively. The production ofD. rosea was high during May–July and October and the level for the whole 9 months was 22.6 g dry weight m⁻².Chaoborus flavicans produced 10 complete and one incomplete cohorts per year. Two consecutive cohorts overlapped during the growing season. The maximum density, the mean biomass, and the production were 19,100 m⁻², 0.81 g dry weight m⁻², and 11.7 g dry weight m⁻²yr⁻¹, respectively. As no fish was present in this pond, the emerging biomass amounted to 69% of larval production. The production ofC. flavicans larvae was high in comparison with zooplankton production during August–September, when the larvae possibly fed not only on zooplankton but also algae.     

The role of copepods in the planktonic ecosystems of mixed and stratified waters of the European shelf seas

The European shelf seas can be divided into regions which have tidally mixed waters and thermally stratified waters. The tidally mixed near shore environments support zooplankton communities dominated by smaller copepods and having large meroplankton contributions. These small copepods (Centropages spp., Temora spp., Acartia spp., Paral Pseudo/Microcalanus spp.) together with the microzooplankton component form a different and more complex food web than the larger copepod/diatom link associated with thermally stratified waters. The copepods Calanus finmarchicus and C. helgolandicus account for over 90% of the copepod dry weight biomass in stratified waters. Although occurring in lower numbers in mixed waters they can still make significant contributions to the biomass. A 31 year time series from the European shelf shows the inter- and intea-annual variability of these species. The basic biology and food web that these two systems support, and the transfer of energy, can result in marked differences in quantity and quality of particulates available as food for fish larvae. Calanus dominated systems allow the primary production to be directed straight through the trophic food chain (diatoms/Calanus/fish larvae) while the near shore communities of smaller copepods limit the amount of energy being transferred to the higher trophic levels. Eighty-two Longhurst Hardy Plankton Recorder hauls were used as the data base for this study. In all cases the zooplankton was dominated by copepods both in numbers and biomass accounting for > 80% of total zooplankton dry weight in the Irish Sea, Celtic Sea, shelf edge of the Celtic Sea and the northern and southern North Sea in Spring.     

不同植物配置下人工湿地大型底栖动物群落特征及其与环境因子的关系

大型底栖动物在人工湿地生态系统的物质循环和能量流动过程中发挥着重要作用,是保持湿地结构稳定、高效运行的重要因素。为了解大型底栖动物在人工湿地内的群落特征,于2013年8月—2014年5月对盐龙湖芦苇(Phragmites communis)、茭草(Zizania latifolia)、狭叶香蒲(Typha angustifolia)表流人工湿地的大型底栖动物群落进行调查。结合相对重要性指数(IRI)、多样性指数(Shannon-Wiener多样性指数,Pielou均匀度指数,Margalef丰富度指数)与相关性分析等手段,研究了不同植物配置下人工湿地大型底栖动物群落特征及其与环境因子的关系。调查共采集到大型底栖动物14种,主要优势物种为纹沼螺(Parafossarulus striatulus)、霍普水丝蚓(Limnodrilus hoffmeisteri)、长角涵螺(Alocinma longicornis)、摇蚊幼虫(Tendipes sp.),但不同植物配置下优势物种有所差别。芦苇、茭草及狭叶香蒲湿地的年均大型底栖动物密度分别为285、330、266个/m2,年均生物量分别为25.6、104.0、32.3 g/m2。茭草湿地的大型底栖动物群落在物种数量、均匀程度上要高于芦苇及狭叶香蒲湿地,而后两者多样性水平相当。茭草湿地底栖动物群落生物量与软体动物密度呈极显著(P0.01)正相关,总密度与水深呈显著(P0.05)负相关,环节动物的密度与全氮(STN)、有机质(SOM)之间分别呈极显著(P0.01)、显著(P0.05)正相关。研究为今后人工湿地生态系统的设计、管护以及长效运行提供新的思路。     

Long-term effects of PO4 fertilization on the distribution of bryophytes in an arctic river

1. Each year since 1983, H₃PO₄ has been added continuously during the ice-free season to a P-limited tundra river (Kuparuk River, North Slope, Alaska). Effects on epilithic metabolism, invertebrate community structure and fish production developed quickly. 2. In 1990, 7 years after fertilization began, we noted extensive coverage by bryophytes within the fertilized reach of the river, where very little had been noted before. Bryophyte biomass from a limited set of quadrats taken in 1990 and 1991 yielded 17 ± 9 (SE) g dry mass m^?2 in control reaches and 322 ± 96 g dry mass m^?2 in fertilized reaches. 3. An initial survey of macroalgal and bryophyte cover in 1991 suggested that the moss Schistidium (Grimmia) agassizii was distributed in both control and fertilized reaches of the river. No clear difference in coverage by this species was found in either reach. 4. In contrast, two species of Hygrohypnum (H. alpestre and H. ochraceum) were found almost exclusively in the fertilized reach. An extensive point transect survey done in 1992, above, within and below the fertilized reach, indicated that increased cover and biomass of Hygrohypnum spp. were confined to the fertilized reach of the river. Detrended correspondence analysis clearly separated the macrophyte and macroalgal communities in the fertilized reach from those in the control and downstream reaches. 5. A fourth bryophyte species (Fontinalis neomexicana) also occurred almost exclusively in the fertilized reach, but was much less abundant than the Hygrohypnum species. 6. Analysis of total N and P in the tissues of the Hygrohypnum spp., and estimates of average coverage (～15%) and biomass (～150g dry weight m^?2) over an 8km fertilized reach, suggest that these species alone may have removed two-thirds of the P added in the fertilizer experiment. The bryophyte community in this river is likely to be the dominant sink for P in the fertilized reach.     

Biomass and abundance of macrofauna in intertidal sediments of Königshafen in the northern Wadden Sea

Intertidal sediments of Königshafen (Island of Sylt, North Sea) were sieved for mesofauna (>0.25 mm) and macrofauna (>1 mm) in spring and autumn 1990. Although sediments are coarser than in other parts of the Wadden Sea, the macrobenthic fauna was very similar but with a tendency towards higher species density, abundance and biomass. Taking into account the areal size of sandy flats, seagrass beds, mud flats and mussel beds, the average biomass is calculated to be 65 g ash-free dry weight m^?2 The lugwormArenicola marina dominates the biomass (28%), followed by the bivalvesMytilus edulis (21%),Mya areanaria (16%),Cerastoderma edule (10%) and the mudsnailHydrobia ulvae (9%). While spring and autumn biomass are almost alike, abundance is highly variable and entirely dominated byH. ulvae. Mesofauna is mainly composed of oligochaetes, small and juvenile polychaetes. Abundance is similar to that of macrofauna, while biomass is only about 1 g m^?2. Macrophyte biomass amounted to 9% of that macrofauna. In the course of the centurym mussel beds expanded while muddy areas declined. The concomitant effects on biomass presumably compensated each other.     

Zooplankton Dynamics in the Hyper‐Eutrophic Nakdong River System (Korea) Regulated by an Estuary Dam and Side Channels

Zooplankton in the main channel of the Nakdong River and in three tributaries was sampled from June 1994 to September 1995. Planktonic rotifers (Brachionus spp., Keratella spp., and Polyarthra spp.), cyclopoid nauplii and small cladocerans (Bosmina longirostris) were numerically dominant. There was considerable longitudinal variation of zooplankton biomass in the main channel as well as spatial heterogeneity among the major tributaries. In the middle region of the main channel, between river kilometer (RK) 170 and 150 above the estuary dam, total zooplankton abundance sharply increased from less than 100 ind. L^—1 to more than 1,000 ind. L^—1. In a downstream direction toward the estuary dam, phytoplankton biomass increased while total zooplankton biomass decreased. However, as shown by the increasing transport of zooplankton biomass, zooplankton was diluted in the reach of the estuary dam. Advective effects from major tributaries appear to be the contributory factor for the higher zooplankton biomass in the middle region. Overall, rather the external factors (flushing, retention) than internal factors (e.g., phytoplankton) appear to be responsible for changes in zooplankton abundance toward the river mouth.     

Changes in biochemical composition and energy utilization during metamorphosis of leptocephalous larvae of the bonefish (Albula)

Synopsis Energy use and changes in whole-body content of lipid, protein, nitrogen, carbohydrate and ash were followed during metamorphosis of leptocephalous larvae of the bonefish (Albula). During metamorphosis, which requires about 8–12 days, larvae lost about 3–4 mg of lipid, or about 50% of the total lipid content. Lipid levels, calculated on a dry weight basis, showed no discernible trends, with values ranging from 138–185 mg (g dry wt)^–1. Protein content was 8.4 mg per larva and showed no significant change. However, protein levels increased from 147 to 329 mg (g dry wt)^–1. Nitrogen content decreased slightly from about 3.5 to 3.2 mg per larva. A comparison of protein and nitrogen values, expressed as % dry weight, showed that, in larvae which were just beginning to metamorphose, 70% of the total nitrogen was non-protein nitrogen (NPN). The NPN decreased to 58% of the total nitrogen towards the end of metamorphosis. Carbohydrate content fell from about 3.5 to 0.6 mg per larva, which represents an 83% loss. Carbohydrate levels also fell from about 81 to 32 mg (g dry wt)^–1. In addition, most of the carbohydrate appears to be bound to protein. Ash content decreased by 52%, from 4.6 to 2.2 mg per larva. Caloric content fell slightly from about 182 to 141 calories per larva whereas caloric density showed no discernible trends, with values ranging from 4.180 to 4.725 kcal (g dry wt)^–1. These results indicate that metamorphosing leptocephali, which apparently do not feed, probably derive most of their energy requirements from metabolizing endogenous lipid and carbohydrate stores formed during the premetamorphic interval.     

Biomass dynamics of grassland vegetation in Kenya

Seasonal changes in plant biomass in the herb layer were measured at Nairobi National Park and Masai Mara Game Reserve in Kenya from January 1980 to February 1981. Plant biomass fluctuated in response to seasonal rainfall, and live biomass was correlated with rainfall and soil moisture at both locations. Peak values for live biomass at Nairobi National Park occurred at the end of the long rains during the June 1980 sample and ranged from 138 to 197gm^-2. Minimum values for live biomass at Nairobi occurred during a dry season in February 1981 and ranged from 8 to 39 g m^-2. The standing dead and litter compartments were larger than the live compartment during every sample period at Nairobi National Park, and together often comprised more than 80% of the total above-ground biomass. Probably as a result of higher rainfall, peak values for live biomass at Masai Mara Game Reserve were higher than those at Nairobi. Again, peak biomass occurred during June following the long rains, and ranged from 218 to 294 gm^-2. Minimum values for live biomass occurred during February 1981, and ranged from 10 to 48 g m^-2. Standing dead and litter compartments were much smaller than at Nairobi National Park, reflecting more intense herbivore pressure and a greater frequency of fires at Masai Mara compared with that at Nairobi National Park.     

PRODUCTION AND NUTRIENT REMOVAL BY PERIPHYTON GROWN UNDER DIFFERENT LOADING RATES OF ANAEROBICALLY DIGESTED FLUSHED DAIRY MANURE1

Growing algae to scrub nutrients from manure presents an alternative to the current practice of land application and provides utilizable algal biomass as an end product. The objective of this study was to assess algal growth, nutrient removal, and nitrification using higher light intensities and manure loading rates than in the previous experiments. Algal turfs, with periphyton mainly composed of green algal species, were grown under two light regimes (270 and 390 μmol photons·m^?2· s^?1) and anaerobically digested flushed dairy manure wastewater (ADFDMW) loading rates ranging from 0.8 to 3.7 g total N and 0.12 to 0.58 g total P·m^?2·d^?1. Filamentous cyanobacteria (Oscillatoria spp.) and diatoms (Navicula, Nitzschia, and Cyclotella sp.) partially replaced the filamentous green algae at relatively high ADFDMW loading rates and more prominently under low incident light. Mean algal production increased with loading rate and irradiance from 7.6±2.71 to 19.1±2.73 g dry weight· m^?2·d^?1. The N and P content of algal biomass generally increased with loading rate and ranged from 2.9%–7.3% and 0.5%–1.3% (by weight), respectively. Carbon content remained relatively constant at all loading rates (42%–47%). The maximum removal rates of N and P per unit algal biomass were 70 and 13 mg·g^?1 dry weight·m^?2·d^?1, respectively. Recovery of nutrients in harvested algal biomass accounted for about 31%–52% for N and 30%–59% for P. Recovery of P appeared to be uncoupled with N at higher loading rates, suggesting that algal potential for accumulation of P may have already been saturated. It appears that higher irradiance level enhancing algal growth was the overriding factor in controlling nitrification in the algal turf scrubber units.     

Primary production in papyrus (<Emphasis Type="Italic">Cyperus papyrus</Emphasis> L.) of Rubondo Island,Lake Victoria,Tanzania

Above- and below-ground production and morphological characteristics of papyrus wetlands were measured at monthly intervals from July 2005 to June 2006 at Rubondo Island, Lake Victoria, Tanzania. The average value of live culm biomass (5,789 ± 435 g DW m⁻²) was higher than that of umbel biomass (2,902 ± 327 g DW m⁻²) by 50%. Root to rhizome means biomass value ratio was 1:1.8, rhizome biomass (4,144 ± 452 g DW m⁻²) being higher than roots biomass (2,254 ± 314 g DW m⁻²) by 45%. Direct proportion was observed between shoot density and culm–unit (culms and umbels) biomass. The average value of detritus/litter biomass (1,306 ± 315 g DW m⁻²) was less than total aerial biomass by 86%. The values of biomass are average of 12 sampling months from July 2005 to June 2006.