Lipids as indicators of eutrophication in marine coastal sediments.

Total organic carbon (TOC) and sedimentary lipid contents were investigated in the Bunnefjord, the most inner part of the Oslofjord (Norway). The Bunnefjord is an intermittent anoxic basin and has undergone major eutrophication since the early 1800s. A core from this fjord was collected at 100 m depths under anoxic remnant waters. The first 15 cm corresponding to deposits from 1500 to present were considered for analysis. Lipid classes were quantified by TLC-FID and the molecular composition of selected lipid classes was investigated by GC and GC-MS. Lipids were dominated by two main classes, phospholipids and hydrocarbons. The hydrocarbons represented up to 7.4% of total lipids in the sediment layers covering the period when the most extensive cultural eutrophication took place (1900 to 1970). The higher fluxes of organic carbon produced during this period may have controlled hydrocarbon inputs into the sediments, due to the hydrophobic character of these pollutants. The hydrocarbon concentration reversed toward pre-industrial levels in the more recent layers, which suggests an improvement of the water quality, possibly in response to improved treatment of the sewage in the cities around Bunnefjord.The second most abundant pool of lipids consists in phospholipids, mostly contributed by bacteria. Even though the concentration decreased with depth, their relative proportions to total lipids remained high, mainly in the deepest layers (>80% of total lipids). A rapid decrease of the polyunsaturated fatty acid methyl esters (FAME) from the phospholipid fraction in the upper 4 cm suggests a rapid biodegradation of planktonic inputs and meiofauna. Odd branched fatty acids were more probably contributed by bacteria linked to the high sedimentary hydrocarbon content. The down core distribution of 16:1omega7, 18:1omega7, 18:1omega5 esterified to phospholipids suggests a vertical zonation of the microbial community in relation to redox conditions and available organic matter. In addition to bacterial sulphur biomass, the presence of hopanoic acids in the phospholipids fraction suggests the contribution of bacteria growing on methane. According to the sterol composition, dominated by 4alpha(H)-methylsterols, dinoflagellates represent the major contributors to the organic matter produced in the water column, particularly during the period of extensive eutrophication. Long-chain diols (1,13-C(26), 1,15-C(30) and 1,15-C(32)) and long-chain keto-ols (1,15-C(30) and 1,15-C(32)) are reported for the first time at high latitudes. Their relative distributions (diol and keto-ol indexes of Versteegh et al. [Org. Geochem. 27 (1997)]) have allowed depicting a particular event during the eutrophication period, a freshwater intrusion with inputs of land-derived organic matter. This is in accordance with the downcore distribution of freshwater/terrestrial markers as sitosterol, dehydroabietic acid and iso- and anteiso-pimaric acids. The diol and keto-ol indexes have also underlined the general transition trend from marine to more brackish waters in the Bunnefjord. These last observations provide confidence into the use of these compounds in paleoenvironmental reconstruction.     

Phytoplankton biomass and species composition in a Mediterranean coastal lagoon

Phytoplankton populations were investigated weekly at a central station in the Fusaro lagoon (Mediterranean Sea) from 27 November 1989 to 18 June 1990 to assess species composition, temporal succession and standing stock of the different species. Chlorophyll concentrations varied from 1.2 to 73.2 µg 1^–1 in surface waters, and from 1.3 to 53.5 µg 1^–1 at the 4.5 m depth. Phytoplankton communities were dominated by Prorocentrum micans Ehrenberg in December and January, and by small-sized diatoms in the rest of the sampling period. In surface waters, a maximum biomass of 9.5 mg C 1^–1 was measured in January, in correspondence with high concentrations (8.1 × 10⁶ cells 1^–1) of P. micans, whereas an abundance peak of 159.9 × 10⁶ cells 1^–1 was registered on the last sampling date due to a massive bloom of a very small diatom, Minutocellus polymorphus (Hargraves & Guillard) Hasle, von Stosch & Syvertsen. On the whole, phytoplankton populations of the Fusaro lagoon showed distinct characters as compared to those of southern Tyrrhenian coastal waters and of other lagoons.     

Phytoplankton species composition and abundance in the Indian sector of the Antarctic Ocean

Summary Water samples collected in the southwestern Indian Ocean between Africa and Antarctica in March 1980 were analyzed quantitatively for phytoplankton. Diatoms dominate the phytoplankton in this region and their numbers generally increase southward with peaks of abundance in both the northern Antarctic Zone and south of the Antarctic Divergence. Average cell numbers (i.e., 6.1×10⁵ diatoms l^-1 in the Antarctic Zone) are comparable to maximum numbers previously reported for the Southern Ocean. Dinoflagellates, flagellates and monads occur in highest concentrations north of the Polar Front. Their numbers are somewhat reduced south of the Antarctic Divergence, and are lowest in the Antarctic Zone. Various diatom assemblages are characteristic of different latitudinal zones. Waters north of and in the vicinity of the Polar Front are rich in the Nitzschia, Pseudonitzschia group of species. In the Antarctic Zone, Nitzschia nana and Dactyliosolen tenuijunctus dominate. Nitzschia species of the Fragilariopsis group are most numerous at stations south of the Antarctic Divergence. Striking differences are noted between the species compositions of quantitative and net-haul samples. A few nanoplanktonic diatoms (e.g. Nitzschia nana and single cells of Chaetoceros spp.) and the weakly silicified Dactyliosolen tenuijunctus, which are dominant in the quantitative samples, are either entirely absent or present only as solitary cells in the net collections.     

大型海藻的营养盐代谢及其与近岸海域富营养化的关系

大型海藻是近岸海域重要的初级生产者,近年来人们愈来愈认识到大型海藻在近岸海域富营养化生物修复中的重要性,同时,富营养化也可能招致某些机会主义大型海藻种类的爆发生长,因此,进一步理解大型海藻与营养盐供应变化的关系就显得非常重要。本文从大型海藻营养盐代谢与海水中营养盐供应变化(主要是富营养化)的生理生态关系角度对相关问题进行评述,主要包括影响大型海藻营养盐吸收特性的重要因素、海水中营养盐的供应及大型海藻对营养盐的细胞贮存、大型海藻对营养盐的生态需求、大型海藻对近岸海域富营养化的生态响应等问题。文章还对今后的研究提出了展望。     

Assessment of the eutrophication status of transitional,coastal and marine waters within OSPAR

Eutrophication (nutrient enrichment and subsequent processes) and its adverse ecosystem effects have been discussed as main issues over the last 20 years in international conferences and conventions for the protection of the marine environment such as the North Sea Conferences and the 1992 OSPAR Convention (OSPAR; which combined and updated the 1972 Oslo Convention on dumping waste at the sea and the 1974 Paris Convention on land-based sources of marine pollution). OSPAR committed itself to reduce phosphorus and nitrogen inputs (in the order of 50% compared with 1985) into the marine areas and ‘to combat eutrophication to achieve, by the year 2010, a healthy marine environment where eutrophication does not occur’. Within OSPAR, the Comprehensive Procedure (COMPP) has been developed and used to assess the eutrophication status of the OSPAR maritime area in an harmonised way. This is based on classification in terms of the following types of areas Non-Problem Areas (no effects), Potential Problem Areas (not enough data to assess effects) and Problem Areas (effects due to elevated nutrients and/or due to transboundary transport from adjacent areas). The COMPP consists of a set of harmonised assessment criteria with their area-specific assessment levels and an integrated area classification approach. The criteria cover all aspects of nutrient enrichment (nutrient inputs, concentrations and ratios) as well as possible direct effects (e.g. increased levels of nuisance and/or toxic phytoplankton species, shifts and/or losses of submerged aquatic vegetation) and indirect effects (e.g. oxygen deficiency, changes and/or death of benthos, death of fish, algal toxins). The COMPP also includes supporting environmental factors. It takes account of synergies and harmonisation with the EC Water Framework Directive, and has formed a major basis for the EC eutrophication guidance. Recently, additional components, such as total nitrogen, total phosphorus and transboundary transports have been included in the assessment of, e.g. the German Bight. The second application of the COMPP resulting in an update of the eutrophication status of the OSPAR maritime area will be finalised in 2008, and will include the agreed integrated set of Ecological Quality Objectives (EcoQOs) with respect to eutrophication. Guest editors: J. H. Andersen & D. J. Conley Eutrophication in Coastal Ecosystems: Selected papers from the Second International Symposium on Research and Management of Eutrophication in Coastal Ecosystems, 20–23 June 2006, Nyborg, Denmark     

The use of species abundance estimates in marine benthic studies

The application of species abundance estimates, commonly used in terrestrial plant ecology, to marine benthic dredge data is advocated. Two possible scales were tested for their ability to measure adequately the structure of an assemblage by computing measures of evenness diversity McNaughton's dominance index, and Morisita's index of dispersion using both real counts obtained from grab samples and these counts transformed into the two respective abundance estimates. It is concluded that species abundance estimators, when applied to grab or dredge data result in significant savings in sample processing time with only a minimal loss of information about assemblage structure.     

Spatial differentiation of marine eutrophication damage indicators based on species density

Marine eutrophication refers to an ecosystem response to the loading of nutrients, typically nitrogen (N), to coastal waters where several impacts may occur. The increase of planktonic growth due to N-enrichment fuels the organic carbon cycles and may lead to excessive oxygen depletion in benthic waters. Such hypoxic conditions may cause severe effects on exposed ecological communities. The biologic processes that determine production, sink, and aerobic respiration of organic material, as a function of available N, are coupled with the sensitivity of demersal species to hypoxia to derive an indicator of the Ecosystem Response (ER) to N-uptake. The loss of species richness expressed by the ER is further modelled to a marine eutrophication Ecosystem Damage (meED) indicator, as an absolute metric of time integrated number of species disappeared (species yr), by applying a newly-proposed and spatially-explicit factor based on species density (SD). The meED indicator is calculated for 66 Large Marine Ecosystems and ranges from 1.6 × 10⁻¹² species kgN⁻¹ in the Central Arctic Ocean, to 4.8 × 10⁻⁸ species kgN⁻¹ in the Northeast U.S. Continental Shelf. The spatially explicit SDs contribute to the environmental relevance of meED scores and to the harmonisation of marine eutrophication impacts with other ecosystem-damage Life Cycle Impact Assessment (LCIA) indicators. The novel features improve current methodologies and support the adoption of the meED indicator in LCIA for the characterization of anthropogenic-N emissions and thus contributing to the sustainability assessment of human activities.     

Oligochaetes and eutrophication; an experiment over four years in outdoor mesocosms

Eight experimental ditch mesocosms were used to study the effect of eutrophication over four years. The experimental ditches had a sand or clay bottom. The ditches were treated with additions of phosphorus, phosphorus and nitrogen, or without additions (controls). Oligochaetes were sampled by deploying trays with substratum for colonization over twenty weeks. Both the important variables phosphorus, nitrogen and oxygen as well as the oligochaete species and numbers are presented. The effects of nutrient additions on phosphorus, nitrogen and oxygen concentrations were described together with changes in oligochaete species composition and numbers. The results were further analyzed by redundancy analysis (RDA). In the clay-lined ditches nutrient addition coincided with fluctuation in oxygen concentration. The higher the nutrient addition levels the longer the period of oxygen depletion became. During oxygen depletion the number of oligochaetes was strongly reduced or even became zero. The low nutrient status of the sandy bed in the sand-lined ditches slowed down the rate of colonization. Only a few tubificids were collected. Eutrophication effects were only observed at the highest nutrient addition level. Considerable variation is attributed to stochastic factors in the sand-lined ditches. Whether oligochaete species were present was related to the length of the colonization period. The substratum composition and food together with oxygen regime decided whether they become more or less abundant in ditches. Large-scale mesocosm experiments require time to develop. Only after the first colonization period variables of species presences and abundances can be employed to detect changes associated with eutrophication. Oligochaetes can be used to measure colonization as well as eutrophication processes.     

Bacterioplankton response to eutrophication in Lake Ladoga

Myriophyllum sibiricum Komarov, an aquatic dicotyledonous macrophyte with a north temperate distribution, was assessed for use in a new bioassay to determine the effect of pesticides, agricultural runoff and municipal waste upon non-target aquatic macrophytes. An axenic culturing system was developed for which an optimal growth medium is required before a bioassay will be reliable. Five media (Murashige and Skoog, Hoagland's, Gaudet's, modified Andrew's, and Hard Water media), commonly used for aquatic plant culturing, were compared to determine the effect on M. sibiricum growth and development. Morphological endpoints for the assay included shoot length, total root length and number, fresh weight and plant area. Membrane integrity, chlorophyll a, chlorophyll b and carotenoid content were the physiological endpoints examined. Based upon these criteria, the modified Andrew's medium at a pH of 5.8, without the addition of a buffer was chosen as a medium which supported rapid and consistent development of M. sibiricum during the two week assay period.     

Phytoplankton community dynamics of two adjacent Dutch lakes in response to seasons and eutrophication control unravelled by non-supervised artificial neural networks

Long-term time-series of the eutrophic Dutch lakes Veluwemeer and Wolderwijd were subject to ordination and clustering by means of non-supervised artificial neural networks (ANN). A combination of bottom-up and top-down eutrophication control measures has been implemented in both lakes since 1979. Dividing time-series data from 1976 to 1993 into three distinctive management periods has facilitated a comparative analysis of the two lakes regarding both the seasonal and long-term dynamics in response to eutrophication control. Results of the study have demonstrated that non-supervised ANN are an alternative technique: (1) to elucidate causal relationships of complex ecological processes, and (2) to reveal long-term behaviours of ecosystems in response to different management approaches. It has been shown that external nutrient control combined with food web manipulation have turned both lakes from nitrogen to phosphorus limitation, and from blue-green algae to diatom and green algae dominance.     

Phytoplankton species abundance in Lake Kasumigaura (Japan) monitored monthly or biweekly since 1978

This data paper reports the abundance of phytoplankton species in monthly or biweekly samples collected from May 1978 through March 2010 at two stations on Lake Kasumigaura, a shallow lake that is the second-largest lake in Japan. The data set of quantitatively over several decades is unique among the available published data papers concerning lakes or plankton and continues to be freely available. The monitoring has been performed as a component of the Lake Kasumigaura Long-term Environmental Monitoring program, conducted by the National Institute for Environmental Studies since 1977. The data set details 173 phytoplankton species (or taxa), which can be identified by using an optical microscope and records their abundance. The abundance of each species is expressed in units of volume (??m³) per milliliter of lake water. This approach allows quantitative comparisons among taxa because the cell size of phytoplankton varies by several orders of magnitude among taxa. The phytoplankton data include 39 species (taxa) of Cyanophyta, 67 Chlorophyceae (Chlorophyta), 3 Prasinophyceae (Chlorophyta), 1 Raphidophyceae (Heterokontophyta), 6 Euglenophyceae (Euglenozoa), 4 Dinophyceae (Dinophyta), 38 Bacillariophyceae (Heterokontophyta), 6 Chrysophyceae (Heterokontophyta), 7 Xanthophyceae (Heterokontophyta), 1 Cryptophyceae (Cryptophyta) and 1 Prymnesiophyceae (Haptophyta). The data have been used for ecological and environmental studies and for studies on lake management.     

南太湖浮游植物特征及其富营养化评价

2008年8-9月对南太湖的浮游植物进行了调查,并对9个采样点水样进行了分析.结果表明:共有浮游植物47种,隶属于7门28属,其中蓝藻门 6属9种,绿藻门10属13种,硅藻门7属18种,裸藻门2属3种,隐藻门 1属2种,金藻门1种,甲藻门1种;南太湖浮游植物的密度为3.56×10~6～7.99×10~6 cells·L~(-1);浮游植物的Shannon-Weaver多样性指数为0.29～2.27,均匀度指数在多数位点<0.5,卡尔森营养状态指数(TSIM)均大于64;根据浮游植物的优势种组成、密度、多样性指数及富营养状态指数的评价结果说明南太湖处于富营养化阶段.

Abstract：

In August-September 2008, an investigation was made on the phytoplankton in south-ern Taihu Lake, and the water quality at nine sampling sites was analyzed. A total of 47 phyto-plankton species belonging to 28 genera and 7 phylums were collected, with 9 species of Cyano-phyta, 13 species of Chlorophyta, 18 species of Diatoms, 3 species of Euglenophyta, 2 species of Cryptophyta, 1 specie of Chrysophyta, and 1 specie of Dinophyta. The phytoplankton density was 3.56×10~6-7.99×10~6 cells·L~(-1), Shannon-Weaver index was 0. 29-2. 77, evenness was low-er than 0. 5, and trophic state index (TSIM) was higher than 64. Based on the evaluation of the dominant species composition, density, and Shannon-Weaver index of phytoplankton, and of the TSIM, the southern Taihu Lake was considered at the stage of eutrophication.     

Phytoplankton biomass response to nitrogen inputs: a method for WFD boundary setting applied to Danish coastal waters

Reference conditions and boundary values between Water Framework Directive status classes were estimated for phytoplankton biomass from empirical relationships relating: (1) nitrogen inputs from land to total nitrogen (TN) concentrations and (2) TN concentrations to chlorophyll a (chl a) concentrations. Different periods during the last >100 years were used to characterise hypothesised ecological status, and a hind-casted time series was used to define boundary values for nitrogen inputs. Nitrogen levels in 35 coastal water bodies around Denmark were significantly related to inputs from land to various degrees (factor of 50) reflecting gradients from open coastal to freshwater-influenced estuaries. Significant differences in the relationship between chl a and TN across sites were found, suggesting that previous response models have been too simple and uncertain. Reference and boundary values for chl a, estimated with a relative uncertainty of 5–20%, varied substantially between sites, and the boundary value between good and moderate status was 6–81% higher than the reference condition with an average of 28%. Differences in bioavailability of nutrient sources and grazing pressure are important factors controlling site-specific phytoplankton biomass, and models for predicting phytoplankton responses to nutrient reductions must account for these. The boundary setting must be adaptive to incorporate improved quantitative knowledge and effects of shifting baselines.     

Seasonal changes in the abundance and composition of marine heterotrophic bacterial communities in an Antarctic coastal area

During a 1-year period, systematic observations of the Antarctic coastal marine bacterioplankton were recorded. Three field stations were sampled weekly in 1989 in Terre Adélie area. The survey included physicochemical (temperature and particulate organic matter) and bacteriological (total and heterotrophic counts, estimation of bacterial production) measurements. The bacterial community structure was investigated by carrying out 27 morphological and biochemical tests on 254 strains isolated during each season. Gram-negative non-fermentative rods were always dominant. However, an obvious difference exists between the communities inhabiting ice-free and ice-covered seawater. The potential metabolic abilities which were relatively significant in the summer community were severely reduced in the winter community. A general increase in bacterial biomass and production was observed in surface water after sea ice formation. The results suggest a close coupling between heterotrophic bacterioplankton and the input of allochthonous organic carbon, for example from the overlying sea-ice communities or from nearby penguin rookeries.     

Phytoplankton response to a changing climate

Phytoplankton are at the base of aquatic food webs and of global importance for ecosystem functioning and services. The dynamics of these photosynthetic cells are linked to annual fluctuations of temperature, water column mixing, resource availability, and consumption. Climate can modify these environmental factors and alter phytoplankton structure, seasonal dynamics, and taxonomic composition. Here, we review mechanistic links between climate alterations and factors limiting primary production, and highlight studies where climate change has had a clear impact on phytoplankton processes. Climate affects phytoplankton both directly through physiology and indirectly by changing water column stratification and resource availability, mainly nutrients and light, or intensified grazing by heterotrophs. These modifications affect various phytoplankton processes, and a widespread advance in phytoplankton spring bloom timing and changing bloom magnitudes have both been observed. Climate warming also affects phytoplankton species composition and size structure, and favors species traits best adapted to changing conditions associated with climate change. Shifts in phytoplankton can have far-reaching consequences for ecosystem structure and functioning. An improved understanding of the mechanistic links between climate and phytoplankton dynamics is important for predicting climate change impacts on aquatic ecosystems.     

广东省典型水库浮游植物群落特征与富营养化研究

研究了广东省19座主要水库2000年丰水期和枯水期浮游植物状况,并根据浮游植物群落结构和多样性指数对水库进行营养状况评价。结果表明,东江流域的新丰江和白盘珠水库水质良好,属于贫营养型水库;大部分水库为中营养型,而鹤地、契爷石和石岩这3座位于沿海经济发达地区水库属于富营养型。流域上游水库水质明显优于下游水库,山区水库水质优于沿海水库,东江流域水库水质普遍较好。北江流域次之,而粤西沿海和珠江三角洲地区各水库均受到不同程度的污染。     

Real-time quantitative PCR for assessment of abundance of Pseudoalteromonas species in marine samples

A real-time quantitative PCR (RTQ-PCR) method for measuring the abundance of Pseudoalteromonas species in marine samples is presented. PCR primers targeting a Pseudoalteromonas-specific region of the 16S rRNA gene were tested at three different levels using database searches (in silico), a selection of pure cultures (in vitro), and a combined denaturing gradient gel electrophoresis and cloning approach on environmental DNA (in situ). The RTQ-PCR method allowed for the detection of SYBR Green fluorescence from double-stranded DNA over a linear range spanning six orders of magnitude. The detection limit was determined as 1.4 fg of target DNA (1,000 gene copies) measured in the presence of 20 ng of nontarget DNA from salmon testes. In this study, we discuss the importance of robust post-PCR analyses to overcome pitfalls in RTQ-PCR when samples from different complex marine habitats are analyzed and compared on a nonroutine basis. Representatives of the genus Pseudoalteromonas were detected in samples from all investigated habitats, suggesting a widespread distribution of this genus across many marine habitats (e.g., seawater, rocks, macroalgae, and marine animals). Three sample types were analyzed by RTQ-PCR to determine the relative abundance of Pseudoalteromonas ribosomal DNA (rDNA) compared to the total abundance of eubacterial rDNA. The rDNA fractions of Pseudoalteromonas compared to all Eubacteria were 1.55% on the green alga Ulva lactuca, 0.10% on the tunicate Ciona intestinalis, and 0.06% on the green alga Ulvaria fusca.     

Linking grazing response of species abundance to functional traits in the Tibetan alpine meadow

Whether grazing response of species abundance can be predicted by plant functional trait remains a challenge untested in a specific ecosystem. We measured species abundance and relevant functional traits for 30 common component species in a moderately grazed and a control community over 3 years (2005, 2006 and 2007) in a Kobresia capillifolia dominated alpine meadow on the Tibetan Plateau. Our objective was to examine species response to grazing and to test the relationship between the response of species abundance and functional traits in grazed and control habitats. Our results showed: i) in terms of species relative abundance and saturated height (the maximum height of an adult individual), most component species significantly decrease in response to moderate grazing and the effect differed among species and between functional groups. ii) The response of species abundance was significantly negatively correlated with saturated height, but not correlated with specific leaf area or seed size. We concluded that the response direction of species abundance to grazing can be predicted by functional traits, whereas it is a weak predictor of the extent of grazing response in species abundance.     

Seasonal variation in abundance and species composition of choanoflagellates (Acanthoecideae) at Antarctic coastal sites

Summary The abundance of loricate choanoflagellates at three shallow inshore sites (< 30 m) near Davis, Antarctica from March 1982 to February 1983 showed marked variation which followed the seasonal cycle of chlorophyll a concentration. In summer the concentration of choanoflagellates ranged from 10⁴–10⁶ cells 1^–1 while in winter they were in the order of 10² cells 1^–1. Species seasonal succession was observed with Bicosta spinifera, Crinolina aperta and Parvicorbicula socialis, organisms which dominated the summer population, being absent in winter whereas Cosmoeca ventricosa and Saepicula leadbeateri were found only in winter. Acanthocorbis unguiculata, Calliacantha simplex and Diaphanoeca grandis were present throughout the year.     

Effect of ploughing on plant species abundance and diversity in the northwestern coastal desert of Egypt

This study focuses on the effect of ploughing on plant abundance,vegetation cover, species richness, and taxonomic diversity during the growingseasons (winter and spring) of 1992 and 2000 in the habitat of inland plateau(natural habitat), 21 km south of Mersa-Matrouh (Egypt).Ninety-five species belonging to 27 families were recorded. High percentages oflife-forms and a large number of species were recorded in ploughed andunploughed stripes in the winter and spring of 2000. Higher averages of importancevalues (IVs) and absolute frequencies were recorded for most perennial andannual species in the unploughed stripes compared to the ploughed ones. This may beattributed to crop failure and consequently unfavourable soil conditions. On theother hand, some shrubby species (e.g. Noaea mucronata andHaloxylon scoparium) and perennial herbs (e.g.Gynandriris sisyrinchium) attained higher IVs in theploughed stripes compared to unploughed ones. This may be attributed to thecultivation of Prosopis juliflora trees in the elevatedpart of the ploughed stripes, which have an ecological role in protecting andenriching the soil with organic matter, thus favouring the growth of theseshrubs and perennial herbs. Higher species richness and diversity wereassociated with low concentration of dominance and low taxonomic diversity inthe spring of 2000 in ploughed and unploughed stripes compared to the winter of1992, for both perennials and annuals. The lowest taxonomic diversities wereexhibited in the spring of 2000 for ploughed and unploughed stripes where thevegetation had the largest number of congeneric species and confamilial genera.Higher species richness and diversity characterized the vegetation of theunploughed stripes, especially in winter and spring 2000, as compared to those ofploughed ones. The present study also reveals low species richness and diversityof therophytes in winter for both ploughed and unploughed stripes.