Candidate Species For Use Research Articles

Effects of different shading levels on the growth of Bornmuellera emarginata, a nickel hyperaccumulator for use in agromining

AbstractThe Greek endemic Bornmuellera emarginata, known for its Ni hyperaccumulation capacity, is a promising candidate species for use in agromining. At the same time, the installation of photovoltaic systems on agricultural land has recently been increasing. Field observations that populations of this species usually occupy shaded places under shrubs or trees led us to study the effect of different shading levels on the growth of B. emarginata, with a view to combine the cultivation of the species with photovoltaic panels in the same area. The experiment was conducted under greenhouse conditions and lasted 210 days after sowing (DAS). Seeds were sown directly into 2‐L pots filled with ultramafic soil collected from the field. Three plant samplings (81, 140, and 210 DAS) were conducted during the experiment to determine a set of morphological and physiological parameters of the species (fresh and dry plant biomass, plant height, number of lateral shoots, total number of leaves, proline and chlorophyll concentrations) alongside with its nickel yield at different levels of shading (0%, 20%, 35%, 60%, and 90%). Growth of B. emarginata was only significantly affected at the highest shading level. Nickel yield of the species increased over time and was maximized at the end of the experiment. The highest nickel yield per plant was observed at the intermediate shading level (35%). Bornmuellera emarginata can be considered as a candidate nickel hyperaccumulator for cultivation in ultramafic or nickel‐polluted areas under photovoltaic panels with corresponding shading, providing important environmental benefits.

Optimization of Industrial-Scale Cultivation Conditions to Enhance the Nutritional Composition of Nontoxic Cyanobacterium Leptolyngbya sp. KIOST-1

Leptolyngbya sp. KIOST-1 has been proposed as a candidate species for use as a protein supplement due to its high protein content and absence of cytotoxicity. The species has also garnered attention due to the photosynthetic pigments it possesses. However, limited information is available on its cultivation. Therefore, this study was conducted to identify the optimal culture medium and fundamental physiological properties of Leptolyngbya sp. KIOST-1 under various culture conditions. In this study, SOT (Society of Toxicology) medium was confirmed as the optimal culture medium for Leptolyngbya sp. KIOST-1 growth. The biomass production, protein content, and photosynthetic pigment content of Leptolyngbya sp. KIOST-1 were significantly higher in SOT medium. The use of this medium allowed for scaling up from laboratory (10 mL) to pilot (200 L) conditions and industrial-scale outdoor conditions (10,000 L), with the biomass containing over 66% protein. The phytochemical composition of Leptolyngbya sp. KIOST-1 cultured at laboratory and industrial-scales was discovered in this study. Furthermore, we observed that reducing the carbon and nitrogen sources to 1/5 of those supplied by the optimal medium did not significantly affect biomass production, and Leptolyngbya sp. KIOST-1 demonstrated favorable growth capabilities in a salinity range of 10–50 psu and at pH levels of 8.3 to 10.3. The results of this study demonstrate the suitability of Leptolyngbya sp. KIOST-1 for various industrial applications and its adaptability to large-scale cultivation.

Natural durability of 8 tropical species suitable for structural roundwood: laboratory screening tests for resistance to fungi and termites

Knowledge of the wood properties of tropical tree species is still relatively limited, so timber extraction focuses on a few abundant, large-diameter species. Very little is known about small-diameter trees, although they could be used directly as roundwood for construction. The aim of this study was to determine the natural durability of 8 candidate species for use as structural roundwood in French Guiana: Goupia glabra, Licania alba, Hymenopus heteromorphus, Lecythis persistens, Oxandra asbeckii, Pouteria bangii, Simarouba amara, Tachigali melinonii and Virola surinamensis. Samples of their wood were exposed to white rot (European and tropical), brown rot (European), and European subterranean termites (using non-choice and multi-choice tests) in laboratory conditions and subjected to screening tests adapted from European standards. Only two species were classified as durable against both fungi and termites: L. alba and P. bangii, which means they can be used without treatment as building material in tropical or temperate climates. The other species tested were classified (1) as durable but with notable differences observed in their resistance to fungi and termites respectively (G. glabra, L. persistens, O. asbeckii), (2) moderately durable (H. heteromorphus), (3) low durability to sensitive (T. melinonii, S. amara, V. surinamensis), meaning actual European standards would not let use these last species in outdoor structures without protection, despite their use by local population in traditional building. However, they could be used for building purposes with appropriate protection systems (including wood protection). The results we obtained for resistance to wood decay provide essential information to assess the potential of these eight tree species in French Guiana’s construction sector.

Barriers in European spiny lobster (Palinurus elephas) aquaculture: What we know so far?

AbstractPalinurids, also known as spiny lobsters, are high‐value seafood, which is economically important for many European and Asian seafood trades. However, the reduction of wild European spiny lobster populations produces a need for developing alternative renewable strategies to meet current and future demands. Aquaculture of spiny lobsters has the potential to become of major economic importance in the coming years with growing markets in Asia, Europe, and America, with Palinurus elephas being a promising candidate species for use in the commercial culture and stock enhancement of natural fisheries. This is due to its shorter larval periods and rapid growth to the critical puerulus stage compared with other spiny lobster species. While we have a basic understanding of the lifecycle and biology of P. elephas, much of this is based on work undertaken on similar species globally. There are many gaps in our knowledge that need to be addressed to make its aquaculture viable with appropriate feeds being an immediate issue as well as many other husbandry‐related factors. Previous studies act as a platform providing a baseline for further research and highlighting constraints. Developments in the use of P. elephas are promising due to realistically bridgeable knowledge gaps, the likelihood of producing sustainable food and the high commercial value of spiny lobsters. This review identifies our present state of knowledge and outlines the scope for further research and necessary technological developments to make it a viable contribution towards crustacean aquaculture in Europe.

Application of a trait‐based species screening framework for vegetation restoration in a tropical coral island of China

Abstract Selecting suitable species for vegetation restoration presents a notable challenge for land managers and scientists. Recently developed trait‐based approaches may be an effective means of overcoming this challenge. However, we lack a trait‐based species screening model that can be used to select potential species for restoration of degraded ecosystems. Here, we developed a species screening model based on quantitative trait‐based theory and a maximum entropy algorithm. The objective was to select more species that have comparable restoration abilities to the target species that have high survival rates for vegetation restoration based on species' functional traits. Thus, species diversity will be improved to facilitate restoration. We also developed a software platform that can be used to implement the model. We then applied our model and software platform to select species for restoration efforts in a tropical coral island which is part of Hainan Island, China. As a prerequisite, we started with three target species which have high potential for restoring the island. Likewise, 66 non‐native species were selected as the potential species pool. For each species, we identified and measured 28 traits that are strongly associated with harsh environments. Harsh environments are those with drought stress, high temperatures, intensive UV radiation, lack of real soil and nutrients, and high salinity and alkalinity. Then, our software platform was used to run the species selection model. Finally, 12 out of 66 species being identified as suitable species for restoration. We transplanted seedlings of all 66 species to the island to monitor seedlings survival. We found that the 12 species identified from our model had high survival rates, which ranged from 86% to 91%. In contrast, the mean survival rate for species not identified from our model was less than 40%. These results suggest that our species screening procedure was appropriate for selecting candidate species for use in vegetation restoration. We show that by using species natural history information, as well as functional trait data, candidate species for restoration efforts can be successfully identified in a timely manner. Importantly, our proposed method is faster and less costly than more commonly used ‘trial‐and‐error’ method. The most time‐consuming aspect of our approach is the need to measure the functional traits of target and potential species. Ultimately, we provide a protocol for using functional traits to quickly select a large number of suitable species for restoring degraded ecosystems. We expect that this work will be important for future vegetation restoration efforts in tropical islands, and perhaps other ecosystems as well. We also expect that our model will help prevent the invasive species and promote specific ecosystem functions. A free Plain Language Summary can be found within the Supporting Information of this article.

Relevance of the ecological traits of parasitoid wasps and nectariferous plants for conservation biological control: a hybrid meta-analysis.

Ecosystem services are key to human survival. In agriculture, they offer potential to intensify production while reducing reliance on hazardous inputs, including pesticides. Nectar plants can nourish natural enemies of pests and thereby promote the ecosystem service of biological control. To date, however, the selection of optimal plants has been reliant on laborious testing of multiple candidate species for use in each new agroecosystem. We report a hybrid meta-analysis of published literature, employing Bayesian network analysis. The hybrid meta-analysis identified the particular plant and parasitoid traits that were most predictive of promoted or suppressed parasitoid longevity. Integrating trait effects identified a combination of plant-parasitoid traits that had the highest impact on parasitoid longevity: compound umbel or raceme inflorescence form and shallow corolla, together with high potential fecundity of the parasitoid. Unlike earlier analyses focusing on taxonomic categories, we analyzed effect sizes in relation to the ecological traits of parasitoids and plants. This generated the first generalizable guidelines for selecting nectar plants as well as appropriate parasitoid targets for the enhancement of biological control. Within the guidelines, optimal outcomes resulted when plants with compound umbel or raceme inflorescences and shallow corollas were combined with fecund parasitoids. More widely, this type of ecological trait-based meta-analysis opens a new avenue for optimizing the delivery of other types of ecosystem services. © 2019 Society of Chemical Industry.

Metal accumulation capacity in indigenous Alaska vegetation growing on military training lands

Permafrost thawing could increase soil contaminant mobilization in the environment. Our objective was to quantify metal accumulation capacities for plant species and functional groups common to Alaskan military training ranges where elevated soil metal concentrations were likely to occur. Plant species across multiple military training range sites were collected. Metal content in shoots and roots was compared to soil metal concentrations to calculate bioconcentration and translocation factors. On average, grasses accumulated greater concentrations of Cr, Cu, Ni, Pb, Sb, and Zn relative to forbs or shrubs, and bioconcentrated greater concentrations of Ni and Pb. Shrubs bioconcentrated greater concentrations of Sb. Translocation to shoots was greatest among the forbs. Three native plants were identified as candidate species for use in metal phytostabilization applications. Elymus macrourus, a grass, bioconcentrated substantial concentrations of Cu, Pb, and Zn in roots with low translocation to shoots. Elaeagnus commutata, a shrub, bioconcentrated the greatest amounts of Sb, Ni, and Cr, with a low translocation factor. Solidago decumbens bioconcentrated the greatest amount of Sb among the forbs and translocated the least amount of metals. A combination of forb, shrub, and grass will likely enhance phytostabilization of heavy metals in interior Alaska soils through increased functional group diversity.

Nitrogen Metabolism in Acorus calamus L. Leaves Induced Changes in Response to Microcystin-LR at Environmentally Relevant Concentrations.

Acorus calamus L., a semiaquatic plant with a high capacity to remove nitrogen and phosphorus from polluted water, is a potential candidate plant for use in the restoration of eutrophic aquatic ecosystems. However, it is not clear how microcystins (MCs), commonly found in eutrophic water, influence plant growth since the effects of MCs are likely to be dose and species dependent. The present study aimed to investigate the regulation of nitrogen metabolism, a key metabolic process related to plant growth, in the leaves of A. calamus L. exposed to microcystin-leucine-arginine (MC-LR) (1.0-29.8µg/L). Nitrate (NO3-) uptake, assimilation and transformation was stimulated in the leaves of A. calamus L. when exposed to 1.0µg/L MC-LR through the elevation of nitrate reductase (NR), glutamine synthetase (GS), glutamate synthase (GOGAT), glutamic-pyruvic transaminase (GPT), and glutamic-oxaloacetic transaminase (GOT) activity. Conversely, MC-LR inhibited nitrogen metabolism by decreasing NO3- uptake and the activities of enzymes related to nitrogen metabolism following exposure to MC-LR (9.9-29.8µg/L) for 30 days, while, ammonium nitrogen (NH4+) content and glutamate dehydrogenase (GDH) activity increased significantly (p < 0.05, LSD test), when compared with the control group. Chronic exposure to MC-LR (9.9-29.8µg/L) negatively influenced nitrogen metabolism in A. calamus L. leaves, which suggested that it may not be a suitable candidate species for use in the restoration of eutrophic aquatic ecosystems containing MC-LR at concentrations ≥ 9.9µg/L.

Host-preference and parasitic capacity of new candidates of Trichogramma species (Hym.:Trichogrammatidae) against some stored product moths

The host-preference and parasitic capacity of some local Trichogramma spp. (T. bourarachae, T. cordubensis, T. euproctidis and T. cacociae) towards four species of stored product moth eggs were investigated in order to select new candidate species for use in mass rearing and biological control against moths in storages. The efficacy of the Trichogramma spp. was compared with T. evanescens, the common wasp used commercially for biological control. Experiments were carried out by offering a single parasitoid female to eggs of the Indianmeal moth Plodia interpunctella (Hubner), the Mediterranean flour moth Ephestia kuehniella Zeller, the warehouse moth E. elutella (Hubner), and the almond moth, Cadra cautella (Walker) in choice and no-choice assays. Two different choice experiments were used to certify the same conclusion in both methods. The bioassay for host-preference of Trichogramma was carried out by offering a single early female wasp the choice between equal numbers of host eggs on square cards “Petri dish tests “and/or strip cards “strip card tests”. In Petri dish tests, E.kuehniella was a highly acceptable host species for T. bourarachae, T. euproctidis, and T. cacociae wasps while E.elutella and C.cautella eggs were more acceptable for T. evanescens and T.cordubensis, respectively. In strip card tests, E.kuehniella eggs were highly acceptable for T.bourarachae, T.cacociae and T.evanescens. Eggs of E.elutella and C.cautella were more acceptable for T.euproctidis andT. cordubensis, respectively. Significant differences were found among the parasitic capacity of the tested Trichogramma spp.: T. borarachae showed a good parasitic potential against S.cerealella and E. kuehniella; T.evanescens and T. cacociae against S.cerealella; T. cordubensis against S.cerealella and P. interpunctella and T. euproctidis against P. interpunctella. All tested wasps had a propensity to superparasitize the host eggs. T. cordubensis, T. euproctidis and T. borarachae showed promise for further investigation into selecting new biological control agents against some stored product lepidopterous pests.

Hybrid Napier grass as a candidate species for bio-energy in plant-based water treatment systems: Interactive effects of nitrogen and water depth

Hybrid Napier grass (Pennisetum purpureum Schumach×P. americanum (L.) Leeke cv. Pakchong1) is a candidate species for use as a bio-energy crop in plant-based water treatment systems due to its high growth and biomass production rate, ease of propagation and harvesting, and the quality of the biomass. We conducted a 2×3 factorial mesocosm experiment with two levels of inorganic N (100μM and 1000μM) and 3 water levels (0, 10 and 20cm depth) and monitored the plant responses in terms of growth and biomass allocation, root morphology and leaf pigment concentrations to assess how hybrid Napier grass responds to a combination of flooding and high N concentrations. Under non-flooded but saturated soil conditions, hybrid Napier grass grew well at both N concentrations, but the tissue contents of minerals and nutrients were higher when plants grew at high N concentration. At 20cm water depth and at the low N concentration, hybrid Napier grass acclimated to the flooded conditions by producing 2.5 times longer adventitious roots from the stem nodes and containing 3 times more lysigeneous aerenchyma compared to the plants grown at non-flooded conditions. At the high N concentration, hybrid Napier grass was not able to acclimate to the flooded conditions and had chlorotic leaves and reduced growth. Hybrid Napier grass can grow both under water-saturated and flooded soil conditions (up to 20cm water depth) while maintaining high biomass production. If N concentrations are moderate (<1000μM), hybrid Napier grass is therefore suitable for use in integrated plant-based water treatment and bio-energy crop production systems.

Influence of hydraulic retention time and plant species on performance of mesocosm subsurface constructed wetlands during municipal wastewater treatment in super-arid areas

ABSTRACTA constructed wetland (CW) in arid areas requires special knowledge given the particular climatic conditions. Among other aspects, the Hydraulic Retention Time (HRT) and plant species may be two important design parameters in hyper- and super-arid areas. Therefore, the study aimed to evaluate the influence of both variables in the application of CW in super-arid areas. Two HRT, 3.5 d and 7 d, and plant species classified by their origin: (a) native, Festuca Orthopylla, Cortaderia atacamensis and Schoenoplectus americanus, and (b) foreign, Cyperus papyrus, were evaluated in four Mesocosm Constructed Wetlands (MCW) operated in a super-arid area. The results showed that the HRT significantly increased (α < 0.05) in more than 10% the removal efficiency of nitrogen and phosphorus forms (TN, NH4+-N, TP, PO4−3-P). These results were the same for the two groups of plants assessed. Moreover, Cyperus papyrus significantly increased (α < 0.05) above 30% the removal efficiency, but only for nitrogen and phosphorus forms. MCW with this plant species showed a water loss above 25% and significantly increased (α < 0.05) the Electrical Conductivity (EC) of effluents. MCW planted with Schoenoplectus americanus showed water losses of around 25% for the both HRT evaluated, and its influence was not significant (α > 0.05) on the EC of the effluents. These results suggest that Schoenoplectus americanus would be an ideal candidate species for use in CW with subsurface flow in super-arid areas, with HRT varying between 3.5 d and 7 d.

Effects of inorganic nitrogen form on growth, morphology, N uptake, and nutrient allocation in hybrid Napier grass (Pennisetum purpureum × Pennisetum americanum cv. Pakchong1)

Plant cultivars with high biomass production may have a high potential for being used in integrated water treatment and plant production system. The highly productive hybrid Napier grass cultivar, Pennisetum purpureum × Pennisetum americanum cv. Pakchong1, may be a candidate species for being used in such systems. We studied the effects of inorganic nitrogen form (NH4+, NH4NO3 or NO3−) on growth, morphology, N uptake, water content and mineral allocation in this species under hydroponic conditions at equimolar concentrations (500μmolNL−1). Generally, the N-form significantly affected growth, biomass allocation and tissue nutrient and mineral composition of the plants. The hybrid Napier grass grew better on NH4+ compared to NO3−, and the plants supplied with NH4+ contained three times more chlorophylls than plants supplied with NO3− alone or NO3− combined with NH4+. The morphology of the plants was, however, not affected by N source, except for the shoot to root ratio, which was lower in NH4+-fed plants. The relative water content of the leaves was lowest in the NH4+-fed plants, but the transpiration rate was not affected, indicating that NH4+ nutrition and the associated low tissue concentration of K had negative effects on the water use efficiency of the plants.The study suggests that this hybrid Napier grass cultivar may be a new candidate species for use in integrated water treatment and plant production systems.

Ammonium tolerance and toxicity of Actinoscirpus grossus – A candidate species for use in tropical constructed wetland systems

Actinoscirpus grossus, a native species in tropical wetlands of South-East Asia, North Australia and the Pacific islands, has been reported to perform well in experimental scale constructed wetland (CW) systems. However, little is known about how high NH4+ concentrations prevailing in wastewater affect growth and performance of this species. We examined growth, morphological and physiological responses of A. grossus to NH4+ concentrations of 0.5, 2.5, 5, 10 and 15mM under hydroponic growth conditions. The relative growth rates (RGR) of the plants were highest at 2.5mM NH4+ but significantly reduced at 10 and 15mM NH4+. The roots of the plants were stunted and produced subepidermal lignified-cell layers at exposure to 10 and 15mM NH4+. The photosynthetic rates did not differ between treatments (average An=21.3±0.4µmolCO2m−2s−1) but the photosynthetic nitrogen and carbon use efficiency (PNUE and PCUE) were significantly depressed at 10 and 15mM NH4+ treatments. The concentration of NH4+ in the roots, but not in the leaves, reflected the NH4+ concentration in the growth medium suggesting that the species is unable to regulate the NH4+ uptake. The high root respiration rates in concert with high tissue NH4+ and declined C/N ratio at 10 and 15mM NH4+ suggest that the NH4+ assimilation occurs primarily in the roots and the plant has inadequate C-skeletons for NH4+ assimilation and exudation at high NH4+ concentration in the external solution. The concentrations of mineral cations were generally reduced and the root membrane permeability increased at high external NH4+ concentrations. Our study shows that A. grossus tolerates NH4+ concentrations up to 5mM which is characteristic of most types of wastewater. Hence, A. grossus is a good native candidate species for use in CW systems in tropical and subtropical climates in South-East Asia, North Australia and the Pacific islands.

A note on the laboratory culture of the benthic foraminifer Cornuloculina balkwilli (MacFadyen)

BackgroundGenetic studies of the Foraminifera provide valuable insights into marine speciation and biogeography, yet the discovery of vitally needed new genetic markers for this important group is being severely limited by an extreme lack of genetic data. The establishment of a laboratory culture from a single, asexually reproducing foraminifer, will be essential to provide enough pooled genetic material from these unicellular organisms, to facilitate full genome sequencing and genetic marker discovery, using next-generation sequencing techniques.FindingsThe aim of this study was to develop a simple and inexpensive method of culturing benthic foraminifera, via asexual reproduction, in a controlled laboratory environment. Individual specimens of the benthic foraminfer Cornuloculina balkwilli (MacFadyen) were placed in 7 cm plastic beakers, containing 50 ml natural seawater, filtered to 0.2 μm, and kept at 23°C, with a 12-hour light/dark cycle, and fed weekly on a mixed algal diet of Dunaliella tertiolecta and Phaeodactylum tricornutum. Asexually derived cultures were successfully established from 4 specimens of Cornuloculina balkwilli, originally added to the culture vessels as immature specimens. Many thousands of individuals were present after 6 months.ConclusionsThe method presented here demonstrates that only basic laboratory equipment is required to establish and maintain a thriving culture of the benthic foraminfer, C. balkwilli, from a single asexually reproducing specimen, providing an excellent source of genetic material for use in next generation sequencing. The method is easily reproducible and will greatly aid in the discovery of critically needed new genetic markers in the Foraminifera. It also highlights C. balkwilli as a good candidate species for use in the field of environmental micropaleontology.

Effects of inorganic nitrogen forms on growth, morphology, nitrogen uptake capacity and nutrient allocation of four tropical aquatic macrophytes ( Salvinia cucullata, Ipomoea aquatica, Cyperus involucratus and Vetiveria zizanioides)

This study assesses the growth and morphological responses, nitrogen uptake and nutrient allocation in four aquatic macrophytes when supplied with different inorganic nitrogen treatments (1) NH 4 +, (2) NO 3 −, or (3) both NH 4 + and NO 3 −. Two free-floating species ( Salvinia cucullata Roxb. ex Bory and Ipomoea aquatica Forssk.) and two emergent species ( Cyperus involucratus Rottb. and Vetiveria zizanioides (L.) Nash ex Small) were grown with these N treatments at equimolar concentrations (500 μM). Overall, the plants responded well to NH 4 +. Growth as RGR was highest in S. cucullata (0.12 ± 0.003 d −1) followed by I. aquatica (0.035 ± 0.002 d −1), C. involucratus (0.03 ± 0.002 d −1) and V. zizanioides (0.02 ± 0.003 d −1). The NH 4 + uptake rate was significantly higher than the NO 3 − uptake rate. The free-floating species had higher nitrogen uptake rates than the emergent species. The N-uptake rate differed between plant species and seemed to be correlated to growth rate. All species had a high NO 3 − uptake rate when supplied with only NO 3 −. It seems that the NO 3 − transporters in the plasma membrane of the root cells and nitrate reductase activity were induced by external NO 3 −. Tissue mineral contents varied with species and tissue, but differences between treatments were generally small. We conclude, that the free-floating S. cucullata and I. aquatica are good candidate species for use in constructed wetland systems to remove N from polluted water. The rooted emergent plants can be used in subsurface flow constructed wetland systems as they grow well on any form of nitrogen and as they can develop a deep and dense root system.

Growth responses of the perennial legume Sesbania sesban to NH 4 and NO 3 nutrition and effects on root nodulation

Preference for NH 4 + or NO 3 − nutrition by the perennial legume Sesbania sesban (L.) Merr. was assessed by supplying plants with NH 4 + and NO 3 − alone or mixed at equal concentrations (0.5 mM) in hydroponic culture. In addition, growth responses of S. sesban to NH 4 + and NO 3 − nutrition and the effects on root nodulation and nutrient and mineral composition of the plant tissues were evaluated in a hydroponic setup at a range of external concentration of NH 4 + and NO 3 − (0, 0.1, 0.2, 0.5, 2 and 5 mM). Seedlings of S. sesban grew equally well when supplied with either NH 4 + or NO 3 − alone or mixed and had high relative growth rates (RGRs) ranging between 0.19 and 0.21 d −1. When larger plants of S. sesban were supplied with NH 4 + or NO 3 − alone, the RGRs and shoot elongation rates were not affected by the external concentration of inorganic N. At external N concentrations up to 0.5 mM nodulation occurred and contributed to the N nutrition through fixation of gaseous N 2 from the atmosphere. For both NH 4 + and NO 3 −-fed plants the N concentration in the plant tissues, particularly water-extractable NO 3 −, increased at high supply concentrations, and concentrations of mineral cations generally decreased. It is concluded that S. sesban can grow without an external inorganic N supply by fixing atmospheric N 2 gas via root nodules. Also, S. sesban grows well on both NH 4 + and NO 3 − as the external N source and the plant can tolerate relatively high concentrations of NH 4 +. This wide ecological amplitude concerning N nutrition makes S. sesban very useful as a N 2-fixing fallow crop in N deficient areas and also a candidate species for use in constructed wetland systems for the treatment of NH 4 + rich waters.

Selectivity of the rotifer Brachionus plicatilis fed mixtures of algal species with various cell volumes and cell densities

The ability for food selectivity of rotifer Brachionus plicatiliswas studied in the laboratory by feeding mixtures of microalgae with various cell volumes. Chlorella sp. (≈22 µm3) was the reference algal species, and Asteromonas gracilis, (Chlorophyta) (≈2150 µm3), Tetraselmis suesica (≈268 µm3), Dunaliella salina (≈52 µm3) and Chaetoceros sp. (≈150 µm3) the experimental species. Each was mixed with Chlorella and fed in three experiments. In the first experiment, filtration and ingestion rates of rotifers each fed with algae revealed that the highest values were measured with the mixture of Chlorella + Asteromonas, and the lowest for Chlorella + Chaetoceros. In the second and the third experiments, by using several combinations of algal densities with the mixture of Chlorella + Asteromonas, a selectivity ability of the rotifers for Asteromonas was found. A hypothesis is presented that accounts for the preference of rotifers for Asteromonas, which is suggested as a new candidate species for use in live food production of fish hatcheries.