Euhydrophyte communities of the River Nile and its impoundments in Egyptian Nubia

The River Nile and its two impoundments, the Aswan Reservoir and Lake Nasser, are important habitats for submerged and floating-leaved freshwater macrophytes (euhydrophytes) in the desert region of Egyptian Nubia. Ordination and classification analysis of survey data collected during the period 1980–1986 suggested that the Aswan High Dam forms a man-made vegetational boundary, delineating two basic macrophyte community types. In Lake Nasser a community dominated by Najas spp. is present. In the Aswan Reservoir and the R. Nile downstream of the old Aswan Dam the euhydrophyte community is dominated by a Potamogeton crispus — Ceratophyllum demersum association. Differences between the two community types appear to be related to differences in physical factors (e.g. water level fluctuation and flow regime), and water chemistry, to phenological factors, and to the differing successional ages of the macrophyte communities of the Nile system upstream and downstream of the Aswan High Dam. There is some evidence for depth zonation of the submerged macrophyte community in both lake and river habitats. Strategy analysis of the euhydrophyte communities present upstream and downstream of the High Dam, over the period 1963–89, indicated that successful established-phase strategy types were similar on both sides of the dam. In the long term there seems little to prevent euhydrophyte species at present confined to below the High Dam from crossing this boundary to colonise Lake Nasser.     

2D finite element ecological model for the Curonian lagoon

The results of application of 2D finite element model SHYFEM to the Curonian lagoon (Baltic Sea) are considered. SHYFEM consist of a physical processes module and an eutrophication module EUTRO adapted for the SHYFEM code from well known modelling system WASP. The SHYFEM/EUTRO model calibration results were compared with the performance of various biogeochemical models analysed in other studies (153 studies published from 1990 to 2002). The performance of all corresponding state variables—dissolved oxygen, NO₃, NH₄, PO₄, phyto- and zooplankton—was slightly lower than median model performance which could be considered satisfactory given the initial state of model formulation and calibration. Model underestimates phytoplankton autumn blooms, especially for the southern part of the lagoon, where fine sediments dominate and water residence time is high. It can be concluded that, in order to increase model performance, the eutrophication module should be improved to account for the dominance of different phytoplankton groups as well as for the exchanges between the sediments and the water column. The amount and quality of the data available for the model setup and calibration are unsatisfactory and should be improved for the development of the next enhanced model version. Guest editors: A. Razinkovas, Z. R. Gasiūnaitė, J. M. Zaldivar & P. Viaroli European Lagoons and their Watersheds: Function and Biodiversity     

Taking stock: inventory of alien species in the Mediterranean sea

573 alien marine metazoan species have been recorded in the Mediterranean Sea. The present checklist is the first to present the species’ native range, presumed mode of introduction, spatial extent, and the date of the first record in each country. The majority of aliens are thermophilic species originating from the Indo-Pacific or Indian Oceans, which have entered the Mediterranean through the Suez Canal. However, the means of introduction differ greatly among the phyla, and the basins of the Mediterranean. The temporal records of the alien species reflect political crises, economic development and scientific interest in studying the phenomenon—in the past two decades on average about 10 alien species new to the Mediterranean are recorded annually. Many have established durable populations and extended their range: 125 alien species have been recorded from four or more countries. The possible impacts of regulatory instruments and environmental management options are examined. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Environmental science and management of coastal lagoons in the Southern Mediterranean Region: key issues revealed by the MELMARINA Project

Lagoons in the heavily populated, semi-arid coastal zone of the Southern Mediterranean Region exemplify the conflict between human utilisation of water and related resources and aquatic ecosystems. Having recognised the requirement to improve understanding of the functioning of the region’s coastal wetlands, the MELMARINA Project undertook integrated hydro-ecological monitoring and modelling within lagoons in Morocco, Tunisia and Egypt. This article highlights some key issues regarding environmental science and management of the region’s coastal lagoons revealed during the course of the project. It stresses the importance of hydrology as a key control upon lagoon functioning and ecosystem dynamics. Hydrological modifications due to water resource management schemes are the cause of many recent changes experienced within lagoons. Linkages between water quality, water availability, human activities and biological characteristics of coastal lagoons are discussed with particular reference to the controls upon vegetation within the MELMARINA lagoons. A series of methodological advances are reviewed which have potential for wider application within coastal lagoons. It is suggested that the use of lagoon sediment for environmental reconstruction can be invaluable, especially when monitoring data are lacking. Recent advances in instrumentation technologies make long-term continuous monitoring more feasible although these approaches can be combined with more traditional site surveys to provide wider spatial coverage at the expense of temporal resolution. Wider spatial coverage can also be achieved through the use of space-borne or aerial remote sensing imagery whilst longer-term trends in site characteristics can be assessed through historical map analyses. Geographical Information Systems, which facilitate the storage and interrogation of large and varied datasets, have enormous potential. Similarly, coupled hydro-ecological models can inform understanding of lagoon functioning and can assess scenarios associated with environmental change or alternative management approaches. The application of integrated, basin-wide approaches to the management of water resources and aquatic ecosystems in the Southern Mediterranean Region is advocated. This includes the application of principles from the EU’s Water Framework Directive. Finally, the need to place management in the context of climate change and associated sea level rise is stressed. Emphasis should be placed on the development of adaptation strategies designed to minimise the effects of these changes. Guest editors: J. R. Thompson & R. J. Flower Hydro-ecological Monitoring and Modelling of North African Coastal Lagoons     

Trace element levels in mollusks from clean and polluted coastal marine sites in the Mediterranean, Red and North Seas

The trace element contamination levels in mollusks were evaluated for different marine coastal sites in the Mediterranean (Israeli coast), Red (Israeli coast) and North (German coast) Seas. Three bivalve species (Mactra corallina, Donax sp, and Mytilus edulis) and two gastropod species (Patella sp.and Cellana rota) were sampled at polluted and relatively clean sites, and their soft tissue analyzed for Hg, Cd, Zn, Cu, Mn and Fe concentrations. Representative samples were screened for organic contaminants [(DDE), polychlorinated biphenyls PCBs and polycyclic aromatic hydrocarbons (PAHs)] which exhibited very low concentrations at all sites. In the Red Sea, the gastropod C. rota showed low levels of Hg (below detection limit) and similar Cd concentrations at all the examined sites, while other trace elements (Cu, Zn, Mn, Fe) were slightly enriched at the northern beach stations. Along the Mediterranean coast of Israel, Hg and Zn were enriched in two bivalves (M. corallina and Donax sp.) from Haifa Bay, both species undergoing a long-term decrease in Hg based on previous studies. Significant Cd and Zn enrichment was detected in Patella sp. from the Kishon River estuary at the southern part of Haifa Bay. In general, Patella sp. and Donax sp. specimens from Haifa Bay exhibited higher levels of Cd compared to other sites along the Israeli Mediterranean coast, attributed to the enrichment of Cd in suspended particulate matter. Along the German coast (North Sea) M. edulis exhibited higher concentrations of Hg and Cd at the Elbe and Eider estuaries, but with levels below those found in polluted sites elsewhere. Received: 25 February 1999 / Received in revised form: 22 April 1999 / Accepted: 30 April 1999     

The influence of climate and sea-level change on the Holocene evolution of a Mediterranean coastal lagoon: Evidence from ostracod palaeoecology and geochemistry

Coastal lagoons provide an excellent basis for the study of processes controlling the evolution of a coastal zone. We examine the relative importance of these processes during the middle to late Holocene through a study of an 8.5 meter-long sediment record from the Albufera de Valencia (Spain). We combine sedimentological analyses with investigations into the palaeoecology, taphonomy and geochemistry (Mg/Ca, Sr/Ca, δ¹⁸O and δ¹³C) of ostracod valves in order to assess the effects of sea-level changes, storm events and effective moisture on the evolution of a Western Mediterranean coastal wetland. The late Pleistocene sediments represent a subaerial environment, which was followed by a hiatus in deposition. The first Holocene unit (～8700–7500 calendar yr. BP) is composed of typical lagoon-barrier and backshore sediments, deposited when seawater intruded into the lake and the climate was arid. The upper part of the sequence (between 7500 and 3400 yr.) is characterized by two sedimentary units, which correspond to Holocene progradation phases and humid climate associated with an increased freshwater influx to the lake accompanied by several high-energy events (palaeostorms). Overall, the record shows that an arid climate prevailed in the western Mediterranean area between 8400 and 7600 yr. The main marine transgression and accompanying progradational phases occurred between 7000 and 3400 yr., which is confirmed by other studies of coastal evolution along the Mediterranean coast. The multiproxy reconstructions demonstrate that controls on sedimentation and palaeoecology in this Mediterranean coastal lagoon were complex.     

Genetic differentiation of Elysia timida (Risso, 1818) populations in the Southwest Mediterranean and Mar Menor coastal lagoon

Genetic variation at 10 enzyme loci was analysed in Elysia timida sacoglossan mollusc samples, originating from both coastal lagoon and marine sites. The observed heterozygosity ranged from 0.390 (Los Urrutias) to 0.277 (Tabarca). Marine and coastal lagoon populations were characterised by exclusive alleles.     

The chemical character and burial of phosphorus in shallow coastal sediments in the northeastern Baltic Sea

The chemical composition and vertical distribution of sediment phosphorus (P) in shallow coastal sediments of the northeastern Baltic Sea (BS) were characterized by sequential extraction. Different P forms were related to chemical and physical properties of the sediments and the chemistry of pore water and near-bottom water. Sediment P composition varied among the sampling sites located in the Archipelago Sea (AS) and along the northern coast of the Gulf of Finland (GoF): the organic rich sites were high in organic P (OP), while apatite-P dominated in the area affected by sediment transportation. Although the near-bottom water was oxic, the sediments released P. Release of P was most pronounced at the site with high sediment OP and reduced conditions in the sediment-water interface, indicating that P had its origins in organic sources as well as in reducible iron (Fe) oxyhydroxides. The results suggest that even though these coastal areas are shallow enough to lack salinity stratification typical for the brackish BS, they are vulnerable to seasonal oxygen (O₂) depletion and P release because of their patchy bottom topography, which restricts mixing of water. Furthermore, coastal basins accumulate organic matter (OM) and OP, degradation of which further diminishes O₂ and creates the potential for P release from the sediment. In these conditions, an abundance of labile OP may cause marked efflux of P from sediment reserves in the long-term.     

The future of terrestrial mammals in the Mediterranean basin under climate change

The Mediterranean basin is considered a hotspot of biological diversity with a long history of modification of natural ecosystems by human activities, and is one of the regions that will face extensive changes in climate. For 181 terrestrial mammals (68% of all Mediterranean mammals), we used an ensemble forecasting approach to model the future (approx. 2100) potential distribution under climate change considering five climate change model outputs for two climate scenarios. Overall, a substantial number of Mediterranean mammals will be severely threatened by future climate change, particularly endemic species. Moreover, we found important changes in potential species richness owing to climate change, with some areas (e.g. montane region in central Italy) gaining species, while most of the region will be losing species (mainly Spain and North Africa). Existing protected areas (PAs) will probably be strongly influenced by climate change, with most PAs in Africa, the Middle East and Spain losing a substantial number of species, and those PAs gaining species (e.g. central Italy and southern France) will experience a substantial shift in species composition.     

The role of alien plants in the natural coastal vegetation in central-northern Spain

Alien plants in coastal habitats and their influence on natural vegetation are studied. After 5 years working on this subject in the Basque Country and surrounding areas, a number of results from the coastal ecosystems are presented. These ecosystems are one of the most threatened and affected by the invasion of alien plants, especially shore dunes, saltmarshes and cliffs. These kinds of habitats, especially the dunes, experience significant pressure from human activities which favours the expansion of some of these species: Arctotheca calendula, Sporobolus indicus and Oenothera spp. The presence and abundance of these invasive plants and others such as Baccharis halimifolia, Cortaderia selloana, Spartina patens and Carpobrotus edulis in the plant communities in an area between the French border and the western part of the region of Cantabria have been studied. The degree of invasion of each plant in each syntaxonomic unit has been analysed.     

The first record of entomopathogenic nematodes (Rhabiditiae: Steinernematidae and Heterorhabditidae) in natural ecosystems in Lebanon: A biogeographic approach in the Mediterranean region

A survey of entomopathogenic nematodes in Lebanon was conducted for the first time during 2008-2009. Samples were collected on the coastal strip and in nine vegetation types extending from the coastal line to 3088 m above sea level. Wooded and herbaceous ecosystems were considered for sampling purposes. A total of 570 samples were taken, out of which 1% were positive for entomopathogenic nematodes. Approximately, 15.8% out of the 19 sites sampled revealed entomopathogenic nematodes presence (representing three samples). Two entomopathogenic nematodes species Heterorhabditis bacteriophora and Steinernema feltiae were recovered, and identification of their symbiotic bacteria revealed the presence of a Xenorhabdus bovienii, Photorhabdus temperata subsp. thracensis, Photorhabdus luminescens subsp. kayaii and Photorhabdus luminescens subsp. Laumondii.     

Growth and survival of the invasive alga, <Emphasis Type="Italic">Caulerpa taxifolia</Emphasis>, in different salinities and temperatures: implications for coastal lake management

The alga Caulerpa taxifolia is an invasive pest species in many parts of the world and has recently become established in several estuaries in south eastern Australia. A major infestation has occurred in Lake Conjola, an intermittently open and closed coastal lagoon in southern NSW. Short term (1 week) laboratory experiments were carried out to investigate growth and survival of fragments of C. taxifolia collected from this outbreak, under a range of salinities (15–30 ppt) and water temperatures (15–30°C). Fronds, stolons and thalli of the alga all displayed similar responses. Many of the algal fragments doubled in size over the week and a maximum growth rate of 174 mm/week was recorded. Fragments showed good growth (> 20 mm/week) at salinities > 20 ppt and temperatures > 20°C. Almost total mortality occurred at salinities lower than 20 ppt and temperatures less than 20°C. Historical records of water quality demonstrate that prior to entrance manipulation in 2001, salinities in Lake Conjola had often dropped to below 17 ppt for extended periods (up to 2 years). This suggests that management of the alga may be improved if the lake was allowed to undergo its normal cycles of opening and closing to the ocean, and that entrance manipulation may be one factor that has influenced the success of this invasive species.     

Changes in the flora and vegetation of the coastal dunes of Voorne (The Netherlands) in relation to environmental changes

Ecologically the former isle of Voorne is very varied. This is reflected by an exceptionally high number of plant species and vegetation types. Many data regarding flora and vegetation have been collected during more than 25 years. A comparison of the early and the later data show that in this period many changes have taken place in flora and vegetation. The changes are partly the result of a natural development of the vegetation, but to a considerable extent they are due to human activities in the coastal area itself and in its surroundings. Examples of changes produced by natural developments and by human activities are given. The effects on flora and vegetation of the area are illustrated by comparing flora inventories, vegetation maps and permanent plot studies. In addition, the future development in the region which will strongly affect its natural value, is discussed.I would like to thank Michiel Boeken, Joke van der Linden and Elly van Oosterhoud who carried out the second flora inventory and Jeanette van Beuzekom and Inge Boelens who mapped parts of the Voorne dune area. I am particularly indebted to Wiecher Smant who offered assistance in many ways.     

A model for photosynthesis and photorespiration in C3 plants based on the biochemistry and stoichiometry of the pathways

Abstract. A model is developed for photosynthesis and photorespiration in C₃ plants, using an equation for the multisubslrate ordered reaction of ribulose 1,5-bisphosphalc carboxylase-oxygenase (Farazdaghi & Edwards, 1988). The model examines net CO₂ fixation with O₂ inhibition, and mutual inhibition when equilibrium exists between carboxylation and oxygenation (at the CO₂ compensation point). It is based on the stoichiometry of energy requirements and O₂, and CO₂ exchange in the cycles, the quantum efficiency for RuBP generation, the maximum capacity for RuBP generation, the carboxylation efficiency with respect to [CO₂], and the oxygenation efficiency with respect to [O₂]. With increasing concentrations of CO₂ above the CO₂ compensation point, decreasing quantum flux density, or decreasing O₂, simulations show that the rate of photorespiration progressively decreases. The two components of O₂ inhibition of photosynthesis change disproportionately with increasing CO₂ concentration. According to the model, the energy utilized during photosynthesis at the CO₂ compensation point is about half that under atmospheric conditions.     

Effect of eutrophication on air–sea CO2 fluxes in the coastal Southern North Sea: a model study of the past 50 years

The RIVERSTRAHLER model, an idealized biogeochemical model of the river system, has been coupled to MIRO‐CO₂, a complex biogeochemical model describing diatom and Phaeocystis blooms and carbon and nutrient cycles in the marine domain, to assess the dual role of changing nutrient loads and increasing atmospheric CO₂ as drivers of air–sea CO₂ exchanges in the Southern North Sea with a focus on the Belgian coastal zone (BCZ). The whole area, submitted to the influence of two main rivers (Seine and Scheldt), is characterized by variable diatom and Phaeocystis colonies blooms which impact on the trophic status and air–sea CO₂ fluxes of the coastal ecosystem. For this application, the MIRO‐CO₂ model is implemented in a 0D multibox frame covering the eutrophied Eastern English Channel and Southern North Sea and receiving loads from the rivers Seine and Scheldt. Model simulations are performed for the period between 1951 and 1998 using real forcing fields for sea surface temperature, wind speed and atmospheric CO₂ and RIVERSTRAHLER simulations for river carbon and nutrient loads. Model results suggest that the BCZ shifted from a source of CO₂ before 1970 (low eutrophication) towards a sink during the 1970–1990 period when anthropogenic DIN and P loads increased, stimulating C fixation by autotrophs. In agreement, a shift from net annual heterotrophy towards autotrophy in BCZ is simulated from 1980. The period after 1990 is characterized by a progressive decrease of P loads concomitant with a decrease of primary production and of the CO₂ sink in the BCZ. At the end of the simulation period, the BCZ ecosystem is again net heterotroph and acts as a source of CO₂ to the atmosphere. R‐MIRO‐CO₂ scenarios testing the relative impact of temperature, wind speed, atmospheric CO₂ and river loads variability on the simulated air–sea CO₂ fluxes suggest that the trend in air–sea CO₂ fluxes simulated between 1951 and 1998 in the BCZ was mainly controlled by the magnitude and the ratio of inorganic nutrient river loads. Quantitative nutrient changes control the level of primary production while qualitative changes modulate the relative contribution of diatoms and Phaeocystis to this flux and hence the sequestration of atmospheric CO₂.