生态意识及其主要特点

一、生态意识产生的时代背景生态意识作为人类思想的先进观念,产生于20世纪后半叶。产业革命以来二百多年,人类依据先进科学技术武装的强大生产力,无限制地向自然进     

Ammonium photo-production by heterocytous cyanobacteria: potentials and constraints

Over the last decades, production of microalgae and cyanobacteria has been developed for several applications, including novel foods, cosmetic ingredients and more recently biofuel. The sustainability of these promising developments can be hindered by some constraints, such as water and nutrient footprints. This review surveys data on N₂-fixing cyanobacteria for biomass production and ways to induce and improve the excretion of ammonium within cultures under aerobic conditions. The nitrogenase complex is oxygen sensitive. Nevertheless, nitrogen fixation occurs under oxic conditions due to cyanobacteria-specific characteristics. For instance, in some cyanobacteria, the vegetative cell differentiation in heterocyts provides a well-adapted anaerobic microenvironment for nitrogenase protection. Therefore, cell cultures of oxygenic cyanobacteria have been grown in laboratory and pilot photobioreactors (Dasgupta et al., 2010; Fontes et al., 1987; Moreno et al., 2003; Nayak & Das, 2013). Biomass production under diazotrophic conditions has been shown to be controlled by environmental factors such as light intensity, temperature, aeration rate, and inorganic carbon concentration, also, more specifically, by the concentration of dissolved oxygen in the culture medium. Currently, there is little information regarding the production of extracellular ammonium by heterocytous cyanobacteria. This review compares the available data on maximum ammonium concentrations and analyses the specific rate production in cultures grown as free or immobilized filamentous cyanobacteria. Extracellular production of ammonium could be coupled, as suggested by recent research on non-diazotrophic cyanobacteria, to that of other high value metabolites. There is little information available regarding the possibility for using diazotrophic cyanobacteria as cellular factories may be in regard of the constraints due to nitrogen fixation.     

Response of grazing snails to phosphorus enrichment of modern stromatolitic microbial communities

1. The effects of added phosphorus (P) on the growth, P and RNA : DNA contents, and survivorship of snails grazing on laminated microbial mats (living ‘stromatolites’) were examined in the Rio Mesquites at Cuatro Ciénegas, Mexico (total P, c. 0.60 μmol L^?1) to test the hypothesis that strong P‐limitation of microautotroph growth produces a stoichiometric constraint on herbivores because of mineral P‐limitation. 2. In a 3‐week experiment performed in summer 2001, addition of phosphorus (+15 μmol L^?1) resulted in a strong decline in stromatolite biomass C : P ratio from very high levels (c. 2300 : 1 by atoms) to moderate levels (c. 550 : 1). The endemic hydrobiid snail Mexithauma quadripaludium responded to P‐enrichment with elevated body P content and higher RNA : DNA ratios, especially for small animals likely to be actively growing. This positive response is consistent with the existence of a stoichiometric constraint on snail growth. 3. In a longer experiment (8 weeks) involving a more moderate P enrichment (+5 μmol L^?1) in summer 2002, P enrichment reduced stromatolite C : P ratio from moderate values in control treatments (c. 750) to very low values (<100 : 1). Snails responded to stromatolite P‐enrichment with increased body P content but, in contrast to the first experiment, with lower RNA : DNA ratio, lower growth rates, and higher mortality. 4. These contrasting results suggest that both very high and very low biomass C : P ratios in stromatolites are detrimental to M. quadripaludium performance, leading us to hypothesise that these herbivores live on a ‘stoichiometric knife edge’.     

Studies of biosorption of Pb2+, Cd2+ and Cu2+ from aqueous solutions using Adansonia digitata root powders

The potentials of Adansonia digitata root powders (ADRP) for adsorption of Pb²⁺, Cd²⁺ and Cu²⁺ from aqueous solutions was investigated. Physico-chemical analysis of the adsorbent (ADRP) shows that hydroxyl, carbonyl and amino groups were predominant on the surface of the adsorbent. Scanning Electron Microscope (SEM) image revealed its high porosity and irregular pores in the adsorbent while the Energy Dispersive X-ray Spectrum showed the major element with 53.0% Nitrogen, 23.8% carbon, 9.1% calcium, 7.5% potassium and 6.6% magnesium present. The found optimal conditions were: initial concentration of the metal ions = 0.5 mg/L, pH = 5, contact time = 90 min, adsorbent dose = 0.4 g and particle size = 32 µm. Freundlich isotherm showed good fit for the adsorption of Pb²⁺, Cd²⁺ and Cu²⁺. Dubinin-Radushkevich isotherm revealed that the adsorption processes were physisorption Cd(II) and Cu(II) but chemisorption with respect to Pb(II) ions. The kinetics and thermodynamic studies showed that Pseudo-second order and chemisorptions provided the best fit to the experimental data of Pb (II) ions only. Batch desorption result show that desorption in the acidic media for the metal ions were more rapid and over 90% of the metal ions were recovered from the biomass.     

Principles for linking fish habitat to fisheries management and conservation

A set of eight simple ecological and social principles is proposed that could enhance the understanding of what constitutes fish 'habitat' and, if implemented, could contribute to improved management and conservation strategies. The habitat principles are a small, interrelated sub‐set that may be coupled with additional ones to formulate comprehensive guidelines for management and conservation strategies. It is proposed that: 1) habitat can be created by keystone species and interactions among species; 2) the productivity of aquatic and riparian habitat is interlinked by reciprocal exchanges of material; 3) the riparian zone is fish habitat; 4) fishless headwater streams are inseparable from fish‐bearing rivers downstream; 5) habitats can be coupled – in rivers, lakes, estuaries and oceans, and in time; 6) habitats change over hours to centuries; 7) fish production is dynamic due to biocomplexity, in species and in habitats; 8) management and conservation strategies must evolve in response to present conditions, but especially to the anticipated future. It is contended that the long‐term resilience of native fish communities in catchments shared by humans depends on incorporating these principles into management and conservation strategies. Further, traditional strategies poorly reflect the dynamic nature of habitat, the true extent of habitat, or the intrinsic complexity in societal perspectives. Forward‐thinking fish management and conservation plans view habitat as more than water. They are multilayered, ranging from pools to catchments to ecoregions, and from hours to seasons to centuries. They embrace, as a fundamental premise, that habitat evolves through both natural and anthropogenic processes, and that patterns of change may be as important as other habitat attributes.     

Patterns and sources of variation in Daphnia phosphorus content in nature

It has recently been shown that Daphnia can vary in the phosphorus (P)-content of their body tissues, but the relative importance of genetic versus environmental causes for this variation is unexplored. We measured variation in P-content (as % body mass) of Daphnia from eight lakes and conducted experiments to contrast three sources of variation: interspecific variation, clonal variation and phenotypic plasticity. Daphnia P-content decreased with increasing seston C:P ratio across lakes. This relationship reflected both inter- and intraspecific variation. Daphnia parvula and D. dubia exhibited high P-content and were found in shallow lakes with low C:P seston, whereas D. pulicaria had low P-content and was found in deep, stratified lakes having high C:P seston. Populations of D. dentifera spanned this lake gradient and exhibited P-content that was negatively related to seston C:P. Evidence for phenotypic plasticity came from experiments with D. pulicaria and D. dentifera collected from a lake with P-deficient seston and fed a P-sufficient diet in the laboratory. In addition, populations of D. dentifera differed in P-content even after 7 d of feeding on P-sufficient resources, suggesting within-species clonal variation. However, mesocosm experiments revealed broad and surprisingly continuous variation in the P-content of individual clones of D. pulex (range 1.54–1.05%) and D. mendotae (1.51–1.07%) over a gradient in dietary C:P. The broad range in P-content exhibited by individual clones, acclimated for generations, suggests that variation in Daphnia P-content from laboratory experiments needs to be interpreted with caution. These results also show that phenotypic variation in response to environment can be a larger source of variation in P-content than genetic differences within or among species.     

Environmental and genetic control of crassulacean acid metabolism in two crassulacean species and an F1 hybrid with differing biomass δ13C values

Abstract The growth, biomass δ¹³C values, and ability to accumulate titratable acidity at night were compared in eight environmental treatments for Cremnophila linguifolia, Sedum greggii, and their F₁ hybrid. In the phytotron, differences in treatment daylength, day/night temperature and water availability were all found to have effects on total plant dry weight, nocturnal accumulation of titratable acidity and biomass δ¹³C value of at least some of the genotypes. However, there were differences between the genotypes both in the magnitude and direction of response of the phenotypic properties to the treatment variables. The phytotron δ¹³C values ranged from -12.9 to -19.2‰ for C. linguifolia, from -22.2 to -33.4‰ for S. greggii, and from -19.2 to -24.9‰ for the hybrid. After with-holding water for 76 h both C. linguifolia and the hybrid had midday Ψ_leaf values of -0.23 MPa; however, S. greggii had a value of -1.05 MPa. In contrast to past observations of other species, the daily watered plants of C. linguifolia had less negative δ¹³C values than did the plants watered only weekly.     

Response of three lotic assemblages to riparian and catchment‐scale land use: implications for designing catchment monitoring programmes

1. Although many studies have focussed on the effects of catchment land use on lotic systems, the importance of broad (catchment) and fine (segment/reach) scale effects on stream assemblages remain poorly understood. 2. Nine biological metrics for macrophytes (498 sites), benthic macroinvertebrates (491) and fish (478) of lowland and mountain streams in four ecoregions of France and Germany were related to catchment and riparian buffer land use using partial Redundancy Analysis and Boosted Regression Trees (BRTs). 3. Lotic fauna was better correlated (mean max., r = 0.450) than flora (r = 0.277) to both scales of land use: the strongest correlations were noted for mountain streams. BRTs revealed strong non‐linear relationships between mountain assemblage metrics and land use. Correlations increased with increasing buffer lengths, suggesting the importance of near‐stream land use on biotic assemblages. 4. Several metrics changed markedly between 10–20% (mountain ecoregions) and 40–45% (lowland) of arable land use, irrespective of the buffer size. At mountain sites with >10% catchment arable land use, metric values differed between sites with <30% and sites with >30% forest in the near‐stream riparian area. 5. These findings support the role of riparian land use in catchment management; however, differences between mountain and lowland ecoregions support the need for ecoregion‐specific management.