Protoperidinium (Dinophyceae) from Greece as seen by scanning electron microscopy

The marine dinoflagellates Protoperidinium ventricum (Abé) Balech, P. diaholus (Cleve) Balech, P. tristylum (Stein) Balech and P. divergens (Ehrenberg) Balech, collected from neritic plankton of the gulfs of Saronikos and Korinthiakos, Greece, have been examined by SEM. Morphological characteristics of their thecae are described and evaluated. Results are compared with patterns established by earlier SEM studies on related taxa.     

Freshwater algae from lakes in the lower Niger Delta system (Nigeria)

Samples from two flood plain lakes (Umuorodog-wum I and II) and one permanent natural lake (Oguta) of the lower Niger Delta system (Imo State, Nigeria), representing the outcome of a single sampling campaign in January 1993, are analysed taxonomically. Emphasis is given on the diatom flora but also on some other accompanying algae; a list of 172 algal taxa is currently presented for the area. The relative species abundance patterns and autecology data confirm the frequent occurrence of taxa capable of tolerating the wide environmental fluctuations determined by local conditions of climate and water chemistry. Comparisons are made between the studied lakes including one disturbed site. The results on the water chemistry and biology corroborate findings from similar ecosystems in West Africa. This revised version was published online in July 2006 with corrections to the Cover Date.     

The application of a micro-algal/bacterial biofilter for the detoxification of copper and cadmium metal wastes

In the present study the potential of a biofilter containing a mixture of dried micro-algal/bacterial biomass for removing heavy metals (Cu²⁺, Cd²⁺) from dilute electroplating waste was tested. The biomass was produced in an artificial stream using the effluent of a municipal waste water treatment plant as a nutrient source, with the additional benefit of reducing phosphorus and nitrogen loadings. Baseline batch experiments determined that optimum adsorption for both metals (80–100%) were achieved with the deionized-H₂O conditioned biomass at initial pH 4.0. Other biosorption variables (contact time, initial metal concentration) were also tested. Biosorption data were fitted successfully by the Langmuir model and results showed a high affinity of the used biomass for both metals (q_max 18–31 mg metal/g.d.w). Flow-through column experiments containing Ca-alginate/biomass beads showed that metal adsorption depends also on flow-rate and volume of treated waste. Desorption of both metals with weak acids was very successful (95–100%) but the regeneration of the columns was not achieved due to the destabilization of beads.     

Limnological survey of the warm monomictic lake Trichonis (central western Greece); II. Seasonal phytoplankton periodicity – a community approach

Phytoplankton assemblages of the warm monomictic lakeTrichoniswere studied during the period April 1985 to February 1986.Speciescomposition and biomass data are presented along withinformationon the seasonal periodicity of dominant taxa of microalgae.Multivariate methods were used to analyze community structureandannual succession. Population succession patterns correspondtochanges in environmental variables. According to thegeneralizedphytoplankton sequences Trichonis is classified as anoligotrophiclake.     

Probing the settlement signals of Amphibalanus amphitrite

To achieve their reproductive potential, barnacles combine tactile exploration of surface structural properties and integration of cellular signals originating from their antennular sensory setae within a developmentally defined, temporally narrow window of settlement opportunity. Behavioural assays with cyprids coupled with biometric analysis of scanning electron microscopy-acquired images in the presence of specific chemical compounds were used to investigate how settlement on a substratum is altered in response to the presence of these compounds. Impeding tactile exploration was shown which altered cellular signalling and/or induced malformation of anatomical features of the antennular sensory setae, which disrupted the settlement behaviour of the model barnacle species Amphibalanus amphitrite. It is concluded that surface exploration by the cyprids relies on mechanical and nociception-related and calcium-mediated signals while a protein kinase C signalling cascade controls the timely metamorphosis of the cyprids to sessile juveniles.     

Periphyton analysis for the evaluation of water quality in running waters of Greece

Based on a microfloristic analysis of periphyton, a selected ecological method of evaluating water quality, independent of saprobic systems is applied to a chosen section of running water in the springs of Levadia, Greece. The graphic representation of the results and an estimation of the degree of pollution is given. A simple method for the quantitative evaluation of the biocoenose of epilithic algae is additionally developed.     

Dynamics of potentially harmful microalgae in a confined Mediterranean Gulf—Assessing the risk of bloom formation

The population dynamics of potentially harmful microalgae was investigated in the semi-enclosed shallow Gulf of Kalloni, Greece (Aegean Sea, Eastern Mediterranean), during a 2-year period from August 2004 to March 2006. A total of 21 potentially harmful microalgae (bloom-forming and/or toxic) were identified including 3 diatoms and 18 dinoflagellates. The densities of each species were analyzed in time and space and in relation to environmental parameters. Some species such as Alexandrium insuetum, Heterocapsa circularisquama, Karlodinium veneficum, Scrippsiella trochoidea, and Ceratium spp. developed high cell concentrations, particularly during a Pseudo-nitzschia calliantha winter bloom. Other species such as Dinophysis caudata, Ostreopsis ovata, Prorocentrum minimum, and Protoperidinium crassipes were rare or appeared in small numbers. Densities of the most abundant species were closely associated with freshwater nutrient-rich inputs during winter, being negatively correlated with temperature and salinity and positively correlated with nitrogen. The spatial distribution of the abundant species exhibited a marked increase towards the inner part of the gulf, close to the main freshwater inputs, whereas some species were mainly concentrated in the dilute surface layer (1 m depth). Examination of the abundance–occupancy relationship revealed that the species more prone to bloom are those with wide spatial distribution and frequent presence throughout the year such as the diatom P. calliantha. Although blooms of cyst-forming species are rarer, an increased risk can be foreseen under favorable resource supply and environmental conditions during winter.     

Limnological survey of the warm monomictic lake Trichonis (central western Greece); I. The physical and chemical environment

The physical and chemical status of Trichonis – the largestanddeepest natural lake in Greece – is examined over two annualcycles (1985–86 and 1988–89). A correlation between lakenutrientpatterns and phytoplankton biomass is attempted. Limnologicalfeatures are compared with data from other warm and temperatelakes.With regard to its thermal regime, Trichonis is classified asawarm monomictic lake. The lake's stratification pattern andannualheat budget resemble those of other temperate lakes. Trichonisisa carbonate type, low conductivity lake (class II, lowsalinitywarm lake). Nitrogen and phosphorus concentrations were ratherlow.The inorganic nitrogen content fluctuated widely over the twoannual cycles examined. On the contrary, phosphorusconcentrationsshowed no significant changes. The limiting factor during1985–86was P, while N was limiting during stratification in 1988–89.Aweak correlation was found between the plankton communityfeatures(species abundance, biomass, chlorophyll-a) and lightpenetration. At present the eutrophication process fromoligotrophytowards mesotrophy has not been essentiallyaccelerated.