Differential anaerobic decomposition of seagrass (Zostera noltii) and macroalgal (Monostroma obscurum) biomass from Arcachon Bay (France)

Arcachon Bay is characterized by extensive meadows of the seagrass Zostera noltii. Moreover, as a consequence of eutrophication, massive proliferations of the macroalga (Monostroma obscurum) have occurred since the beginning of 1990s.This paper describes the anaerobic decomposition of biomass of both species under experimental conditions by two methods. Firstly, the dynamics of decomposition were studied in situ using litter bags. The remaining biomass and the elemental composition of the decomposing macrophytes were monitored. Secondly, degradation was studied in experimental containers under anoxic conditions in which the release of inorganic nutrients and the development of fermentative and sulfate-reducing bacterial populations were followed.The decomposition rate of total biomass was faster for macroalgae than for the vascular plants, thus corroborating previous observations. However, both in situ and laboratory experiments showed that the anaerobic decomposition of the seagrass Z. noltii resulted in rapid release of inorganic N and P, and increasing C/N and C/P ratios of the residual biomass. As a result, the recycling of inorganic nitrogen and phosphorus compounds was slightly more efficient for Z. noltii than for M. obscurum. Recycling of inorganic nutrients appears to be of a great importance to the whole ecosystem, because of the extensive spreading of Z. noltii in the bay.     

Utilization of seaweed Ulva sp. in Paracas Bay (Peru): experimenting with compost

In Paracas Bay (Peru), large quantities of Ulva sp. interfere with various important activities of the zone. In this context, the present study was undertaken to evaluate the effect of adding Ulva sp. in compost piles and the quality of the resulting composts. Six compost piles were prepared using, straw, green material mixture, cow manure and Ulva in different quantities (9, 17 and 28% of volume) and forms. Several variables were monitored during the process and the chemical characteristics of the final composts were determined. Aerial biomass achieved by maize plants was also evaluated for each compost at different compost/sand proportions. Results show that the compost pile made with Ulva powder registered the highest temperature and the longest thermophilic phase. Piles prepared with 28% washed Ulvapresented anoxic conditions at the beginning and had higher electrical conductivity values. Carbon/Nitrogen ratio diminished appropriately in all piles and there was no negative effect observed on the pH of the piles. Compost prepared with Ulva had lower contents of Total Kjeldahl Nitrogen, and produced maize plants aerial biomass.     

Utilisation of Ulva rigida biomass in the Venice Lagoon (Italy): biotransformation in compost

In the Venice Lagoon (Italy), about 10⁶ t (wet weight) of Ulva rigida biomass are produced annually as one of the major results of eutrophication. Harvests have been initiated to reduce negative impacts of this biomass, however, due to the high costs of such effort, only 40 000 t yr^-1 are currently being collected. At the moment, biotransformation into compost seems to be the only feasible technology for utilising large quantities of Ulva biomass. We describe and discuss here a successful composting strategy together with the chemico-physical and microbiological characteristics of the resultant composts. Our composting experiments were conducted at a scale of 20 t. The composting technology utilises large proportions (70–90%) of Ulva biomass and results in a valuable, high-quality end product (compost and compost-based products). This process and the resulting products represents a relatively simple way of utilising the Ulva biomass produced annually in the Venice Lagoon.     

The effect of localised eutrophication on competition between Ulva lactuca (Ulvaceae,Chlorophyta) and a commercial resource of Gracilaria verrucosa (Gracilariaceae,Rhodophyta)

In spring (August) 1993 a bloom of Ulva lactuca appeared for the first time in Saldanha Bay, South Africa, and persisted through summer. Ulva wash-ups contaminated the beach and part of the commercial Gracilaria beach-cast had to be discarded. The biomass and distribution of Gracilaria and Ulva are described in relation to the seasonal water chemistry of the bay. Gracilaria survives in deeper water in summer by the pulsing of nutrients on an approximately 6-day cycle of movement of the thermocline that separates nutrient-rich bottom water from warm oligotrophic surface water. Ammonium-rich fish-factory discharge into this surface layer in a sector of the bay provided localised conditions for Ulva to out-compete Gracilaria at depths of 2–5m, demonstrating the powerful disruptive effect of eutrophication in this strongly stratified system.     

Gracilaria conferta and its epiphytes: (2) Interrelationship between the red seaweed and Ulva cf. lactuca

Ulva cf. lactuca has been a disturbing competitor of experimental Gracilaria conferta outdoor cultures in Israel. The effect of environmental conditions on the competitive ability of Ulva versus Gracilaria, and the main limiting factors for which these seaweeds compete, were studied here. Single and biculture experiments of both seaweeds showed that Ulva outgrew and damaged Gracilaria under all irradiance and temperature combinations. The higher competitive ability of Ulva cf. lactuca in bicultures was not a result of responses to shading or nitrogen shortage, but rather to a shortage of available inorganic carbon, an increase in pH and apparent excretions of Ulva which inhibited the growth of Gracilaria.     

Summer biomass of a population of Iridaea cordata (Gigartinaceae,Rhodophyta) from Antarctica

Results of a seasonal study on biomass in an infralittoral population of Iridaea cordata from Terra Nova Bay (Ross Sea, Antarctica) are reported. Thalli were collected during the IX Italian Antarctic Expedition (austral summer 1993–94). The population studied is that living at depths of 4 to 6 m, where the highest density of plants occurred. The highest value of biomass (wet weight 3440 g m^–2) was found at the beginning of summer. In that period 72.5% of biomass was from 128 specimens belonging to weight classes 8 (>16 to 32 g) to 10 (>64 g), corresponding to 13.4% of the population in numbers. Small (<1 g) and medium (1 to 8 g) specimens provided the remaining biomass of 5% and 22.5%, respectively. During the month of January, the number of heavy specimens decreased. At the end of that month biomass reached a minimum of 2225 g m^–2. In February the biomass increased to 3169 g m ^–2, 72% of which was from 120 specimens belonging to weight classes 7 (>8 to 16 g) to 9 (>32 to 64 g), which numerically represented 18.5% of the population. Data showed that biomass depended mainly on the presence of large heavy specimens, even though they were always few in number. Moreover, the occurrence of such large thalli at the beginning of summer suggests that Iridaea cordata continues to grow during the long antarctic winter.     

Biosorption of di(2-ethylhexyl)phthalate by seaweed biomass

Samples of various Sargassum species were collected in the Hong Kong marine environment and used for studies on biosorption of di(2-ethylhexyl)phthalate (DEHP). Batch adsorption experiments were carried out to determine the removal capacity and removal efficiency of the biosorbents. The DEHP removal ability was similar among beached seaweed and three freshly collected Sargassum species. Different physico-chemical factors were evaluated in order to enhance the performance of the biosorbents. Under optimized conditions (25 mg biomass, initial pH 4, 25 °C, 40 mg L^–1 DEHP), the mean removal capacity of beached seaweed and Sargassum siliquastrum was 5.68 and 6.54 mg g^–1, respectively. Examination of the Langmuir and Freundlich adsorption isotherms showed that the biosorption phenomenon by these biosorbents could well be described by these models. Desorption of DEHP was also assessed with methanol, which showed the most satisfactory desorbing ability. Further study in multiple adsorption–desorption of DEHP by the biosorbents demonstrated the reusability of both beached seaweed and S. siliquastrum for biosorption of DEHP.     

Effects of a macroalgal mat (Ulva lactuca) on estuarine sand flat copepods: an experimental study

The effects of a macroalgal mat (Ulva lactuca) on intertidal sand flat copepods were studied in Jamaica Bay, NY. In 1999, Ulva was removed from paired quadrats in the algal mat. Density and species richness were estimated from sediment cores over seven biweekly periods and compared with Ulva-removal quadrats and with an unvegetated reference site. In a separate analysis at the same site, species composition and density of all copepods within the algal mat were determined from replicated quadrat samples over seven dates. Emergence traps were deployed in all treatments in 1999 to quantify copepod movements from sediments into the water column during flooding tide. Dissolved oxygen (DO) was continuously monitored over several 96-h periods in and above the algal mat. In 2000, three biomass levels of Ulva (0, 100, 200 g DW per m²) were added to paired quadrats in the unvegetated zone. Density and species richness were estimated over eight time periods. Ulva removal resulted in significant increases in density and species richness, but levels remained lower than at the unvegetated site. Likewise, addition of Ulva biomass produced significant declines in copepod density. However, the differences between low- and high-Ulva-addition treatments were insignificant. Increases in phytal copepods after Ulva addition did not compensate for losses of epibenthic and infaunal species. The overall effect of the Ulva mat was a net loss of copepod density, including the loss of nearly all infaunal species. Anoxia in sediments and within the algal mat are correlated with declines in infaunal species and with escape by some infaunal species from the sediment into the water column.     

The relationship between stand biomass and frond density in the clonal alga Mazzaella cornucopiae (Rhodophyta,Gigartinaceae)

The negative relationship between stand biomass and plant density observed in terrestrial plants was tested among fronds of a clonal red alga, Mazzaella cornucopiae. Stand biomass and frond density were estimated bimonthly for 1 year on 7 permanent quadrats. A positive linear correlation was found between biomass and density for the whole data set, suggesting the lack of self-thinning among fronds of this intertidal alga at natural densities. Higher frond densities could favor increased water retention among fronds, thus minimizing desiccation during low tides. In this way, stands could maintain higher production of biomass. Fronds may also be cushioned better against wave action at higher frond densities, thus decreasing the detachment of larger fronds. The temporal variation of the relationship between biomass and density was plotted separately for these 7 quadrats. Four quadrats showed positive linear correlation between both variables (the other three quadrats showed non-significant positive linear correlation). Their four slopes are statistically similar to that found for the entire data set. It is possible, then, that there is only one positive slope for the biomass-density relationship in this population. If this is true, standing biomass could be estimated from the density of fronds.     

A revision of European taxa ofHyacinthoides sectionSomera (Hyacinthaceae) on the basis of multivariate analysis

Cluster analysis and principal components analysis were used to investigate patterns of morphological variation among specimens of European species of sect.Somera of the genusHyacinthoides (Hyacinthaceae). The results are clearly consistent with the existence of four species (H. italica, H. paivae, H. reverchonii andH. mauritanica). It is proposed that the latter be considered to comprise two subspecies,H. mauritanica subsp.mauritanica andH. mauritanica subsp.vincentina (comb. nov.). A key is presented, together with distribution maps for the five taxa.     

Contribution on the content and nature of the phycocolloid from Kallymenia reniformis (Cryptonemiales,Rhodophyta)

The red alga Kallymenia reniformis (Rhodophyta, Cryptonemiales), collected on the west coast of Brittany, contained 13% ash, 5.6% crude protein and 38.7% soluble carbohydrate (on percent dry wt). The phycocolloid extract (38 % dried wt) was investigated using chemical and spectroscopic (IR and ¹³C NMR) methods. Preliminary results show that this polysaccharide belongs to the lambda-carrageenan family.     

Metabolism and bioconversion of chromene derivatives inAgeratina adenophora (Asteraceae)

Seedlings ofAgeratina adenophora accumulate the chromenes demethoxyencecalin, encecalin and demethylencecalin. More than 80% of the total chromenes within the seedling are confined to the leaves where they are stored within the mesophyll. Metabolism of the chromenes during development of the seedlings was subjected to analysis by high-performance liquid chromatography. The accumulation kinetics obtained, as well as feeding experiments with non-radioactive chromenes, showed the bioconversion of these compounds to proceed from demethoxyencecalin via hydroxylation yielding demethylencecalin, followed by methylation yielding encecalin. Inhibitor studies with glyphosate indicate that the chromenes arise from precursors derived from the shikimic-acid pathway.Abbreviation HPLC high-performance liquid chromatography     

Annual growth rate of the calcareous red alga Lithothamnion corallioides (Corallinales,Rhodophyta) in the Bay of Brest,France

Lithothamnion corallioides Crouan et Crouan (Rhodophyta, Corallinales) is the main constituent of the maerl beds of the Bay of Brest (Atlantic coast of western Brittany). Its growth rate was measured monthly in situ during one year. Growth rates were obtained by an adaptation of the buoyant weight technique. The highest daily growth rate was observed in July and reached 0.26 % d^–1 (S.D. = 0.06), when expressed as the increase of calcium carbonate weight. The average daily growth rate was 0.12% d^–1 (S.D. = 0.04) for a period of 275 days (summer and autumn 1988, winter 1989). Using this preliminary data, the calcium carbonate accretion rate can be estimated provisionally: 876 g m^–2 year^–1, a rate much lower than that of tropical reef coralline algae, but higher than that of Lithophyllum incrustans, the well known temperate European reef-builder.     

Optimisation of RNA extraction from Gracilaria changii (Gracilariales, Rhodophyta)

RNA extraction from seaweed tissues is problematic due to the presence of polysaccharides and polyphenolic compounds upon cell disruption. Besides, a successful RNA isolation from seaweed tissues can sometimes be strain- and species-specific. Four different methods were used to extract RNA from Gracilaria changii (Gracilariales, Rhodophyta), collected from the mangrove area at Morib, Selangor, Malaysia. An optimised and modified total RNA extraction method was developed for this recalcitrant species. The use of sand in tissue grinding, and the incorporation of phenol extraction at the initial stage resulted in the highest RNA yield (0.65–1.14 g g^–1 fresh weight) with high quality (A_260:280 ratio 1.80–2.05). The RNA obtained is suitable for cDNA synthesis and future functional genomic studies.     

Lead,mercury, and certain nutrient elements in ulva lactuca (linnaeus) from Ras Beirut,Lebanon

Collections of Ulva lactuca (Linnaeus) at nine locations along the coast of Ras Beirut, Lebanon were analysed for lead, mercury, phosphate, calcium, magnesium, iron, copper, and zinc. Low lead concentrations, the same in all samples, could possibly indicate that U. lactuca has some means by which lead uptake and toxicity can be controlled. Phosphate levels may be a contributing factor to this process.Concentrations of all other elements seemed relatively uniform with few exceptions. This suggests that U. lactuca is subject to similar environmental conditions and element exposure at each of the collecting sites and might be capable of maintaining biochemical stability under high levels of stress.Further studies of toxic and nutrient elements as to their individual and combined effects in U. lactuca are needed.c/o Sturdy Memorial Hospital, Attleboro, Massachusetts U.S.A.     

Worldwide invasion of vector mosquitoes: present European distribution and challenges for Spain

An Asiatic mosquito species, Aedes albopictus, began to spread worldwide in the 1970s thanks to marine transport of tires and other goods, leading to colonization of many areas of the world. This species is a vector of major human diseases such as Dengue, Yellow Fever and the West Nile virus. In Europe, it was established in Albania and Italy and has been detected in other countries such as France; no records exist for Spain as yet. Colonization by Aedes albopictus is a major public health concern considering that the West Nile virus and several other viruses are known to circulate sporadically in the Mediterranean. Additionally, the parent species Aedes aegypti was the vector causing severe outbreaks of Dengue and Yellow Fever two centuries ago. Although Ae. aegypti was also introduced, it was eradicated from Spain. Both mosquitoes shared habitat types, diseases transmitted and many bionomic data. This article contains a review of the present Ae. albopictusdistribution range worldwide and discusses the likelihood of an establishment in Spain in view of climatological and geographical data. This revised version was published online in July 2006 with corrections to the Cover Date.     

Effect of grazing by isopods and amphipods on growth of Ulva spp. (Chlorophyta)

Eutrophication of shallow coastal waters often leads to blooms of macroalgae. Grazing by crustaceans, such as amphipods and isopods, can reduce macroalgal biomass accumulation. At the same time, growth of the macroalgae can be stimulated by epiphyte removal. The role of grazing by isopods and amphipods on Ulva spp. biomass development was investigated in the Veerse Meer, a brackish lagoon situated in the southwest Netherlands. Exclusion of grazing in the field did not stimulate Ulva spp. growth. In fact, growth rates were higher in exclosures that allowed grazers to enter. Edibility tests identified the amphipod Gammarus locusta, and the isopods Idotea chelipes and Sphaeroma hookeri as potential grazers on Ulva spp. However, when epiphytic diatoms were present on the Ulva spp. thalli, Gammarus and Sphaeroma grazed on ephiphytes and not on Ulva tissue. Only Idotea continued to graze on Ulva spp. A laboratory growth experiment revealed a positive effect of Gammarus presence on Ulva spp. growth, probably caused by preferential removal of epiphytic diatoms from the Ulva spp. thalli. The growth stimulation by epiphyte removing grazers such as Gammarus may explain the higher growth rates in the presence of grazers observed in the field. When determining the potential role of invertebrate grazers in controlling macroalgal biomass accumulation, it is important to include an assessment of the epiphyte abundance on the macroalgae, as preferential removal of epiphytes may stimulate growth and thus have the opposite effect.     

Influence of diet and photoperiod on development and reproduction of European populations of Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae)

The current study examines the effect of photoperiod (16:08 or 12:12 h L:D) and diet (eggs of Ephestia kuehniella Zeller (Lepidoptera: Phycitidae) or the pea aphid Acyrthosiphon pisum (Harris) (Hemiptera: Aphididae)) on the development and reproduction of the multicoloured Asian lady beetle Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae). A long-term laboratory population of H. axyridis (since 1998) and a melanic and non-melanic population originating from field collected individuals of H. axyridis in Belgium were used in this study. Long day conditions (16 h photoperiod) shortened development of the field populations with 2–3 days when compared with short day conditions (12 h photoperiod). Oviposition in the field populations was delayed by 1–3 months when reared at a 12 h photoperiod. Dissections indicated that the females were in reproductive diapause. As compared with live pea aphids, a diet consisting of E. kuehniella eggs yielded heavier adult body weights (up to 12%) and increased the number of egg laying days (by 45–169%) for both field populations at a 16 h photoperiod and lengthened adult life span (by 45–92%) under both light regimens. The morph types differed in their response to the foods offered in terms of developmental rate, pre-oviposition period and number of oviposition days. The laboratory and field strains responded differentially to regimens of food and photoperiod. The study indicated a greater nutritional plasticity of the non-melanic morphs which may offer them a competitive advantage that may in part explain the predominance of non-melanic morphs in newly colonized areas.