Distribution patterns of Batrachium communities in Mediterranean hard waters

The greatest number of Batrachium plant-communities is reached in base-poor waters of SW Europe where most Batrachium species develop laminar leaves. In contrast, base-rich waters of the Western Mediterranean are characterized by few Batrachium communities and by the only one Batrachium species present in the area with only dissected leaves. This work focused initially on studying the water ecology of Iberian Batrachium communities' developing in hard waters in order to seek to what extend the water physical–chemical gradient determines the occurrence of heterophyllous or homophyllous-dissected species. Floristic data and water physical–chemical data were analyzed using multivariate and comparative methods. We found two main types of Batrachium communities: community of Ranunculus trichophyllus – homophyllous and dissected species–, and community of Ranunculus penicillatus – heterophyllous species–. Alkalinity degree is the main factor separating both communities. Our results of a tentative survey on Batrachium composition in hard waters in the Eastern Mediterranean showed a wider range of physical–chemical water features as well as a greater number of Batrachium species with only dissected leaves in comparison to Western Mediterranean. We conclude that high alkalinity is related to the occurrence of Batrachium communities characterized by species with only dissected leaves in both the western and eastern parts of Mediterranean Europe.     

Phytosociological,bioclimatic and biogeographical classification of woody climax communities of western North America

Abstract. In this study, combining the Braun-Blanquet phytosociological approach with numerical methods (cluster analysis and principal coordinate ordination), woody climax associations of western North America are described, ranging from NW Baja California (Mexico) to Alaska (USA), and including some interior zones of Idaho and Montana (USA), Alberta, British Columbia and the Yukon Territory (Canada). 95 floristic associations are identified, and each is characterized by floristic combination, biogeographical range, and bioclimatic conditions.     

Unimodal patterns of microbial communities with eutrophication in Mediterranean shallow lakes

The role of the microbial communities in the classical planktonic food web and its response to eutrophication in shallow lakes is still contradictory. Mediterranean shallow lakes with different eutrophication levels were sampled to study the influence of eutrophication on the microbial food web (MFW) and their contribution to the planktonic food web. Percentage of ciliate biomass in the metazooplankton (MZP) showed a U-shaped trend with eutrophication, with maximum at both ends of the chlorophyll-a (Chla) gradient. The MZP to phytoplankton ratio demonstrated a unimodal pattern with minimum values at the two ends of the Chla gradient and maximum values in the Chla range 5-10 μg l^?1. In contrast, the MFW to phytoplankton ratio reached its minimum in the central part of the Chla gradient and maximum values at the extremes of the gradient. These patterns support the hypothesis that the relative importance of bacteria and ciliates is lowest in mesotrophic shallow lakes, and highest in oligotrophic and hypereutrophic systems. These results stress the importance of protozoan in the trophic web, and indicate it is essential to include this group, especially ciliates, when quantifying zooplankton in warm shallow lakes.     

Fish communities and food web interactions in some shallow Mediterranean lakes

Hydrobiologia - Fish communities of five shallow Spanish Mediterranean lakes were studied and stomach content analysed to determine the foraging pattern of each species and the influence on the...     

Sulfate-reducing prokaryotic communities in two deep hypersaline anoxic basins in the Eastern Mediterranean deep sea

In the Eastern Mediterranean Sea, deep hypersaline anoxic basins (DHABs) and deep-sea sediment contain anoxic environments where sulfate reduction is an important microbial metabolic process. The objective of this study was to characterize the sulfate-reducing community in the brine and interface of the DHABs L'Atalante and Urania based on a phylogenetic analysis of the dissimilatory sulfite reductase gene (dsrA). Results demonstrated that the sulfate-reducing community was diverse, except for the sulfidogenic brine of the Urania basin. The similarity of the dsrA sequences between different environments was very low demonstrating that each environment had a unique sulfate-reducing community. Sequences had 67.6-93.3% similarity to dsrA sequences from GenBank database and were mostly related to the delta-proteobacteria. Each environment was dominated by a different family within the delta-proteobacteria except for the Urania interface, which was dominated by sequences related to the Gram-positive Peptococcaceae. We conclude that sulfate-reducing communities inhabiting the L'Atalante and Urania basins are highly diverse with low similarities to each other and contain a sulfate-reducing species composition that is very different from sulfate-reducing species compositions in previously studied ecosystems.     

Feeding diversity in macroinvertebrate communities: A contribution to estimate the ecological status in shallow waters

The feeding diversity of subtidal samples of macroinvertebrates from Ria Formosa was estimated with Shannon–Wiener information index and complementary evenness. The results were compared with other commonly used methodologies under the European Water Framework Directive, such as diversity indices, AMBI and ITI.Assuming that in a healthy environment all feeding groups are present, and that no group clearly dominates, the feeding diversity is expected to be maximal and the evenness feeding diversity will be close to 1. In degraded environments some feeding groups might be absent or having low relative abundance, and generally with one or two groups dominating the community. In this way the evenness feeding diversity index would measure deviations from expected values due to a degradation of the environment. Although confirmation of this approach needs to be tested in other shallow waters, the results obtained show interesting features.To each of the 297 species belonging to the Ria Formosa data matrix a feeding group was assigned, among six groups: surface deposit feeders, subsurface deposit feeders, herbivores, suspension feeders and suspension/deposit feeders (species which have the two feeding modes depending on food availability). The carnivorous, parasites, omnivorous and scavengers were all grouped together, forming the sixth group. Most of the stations of Ria Formosa showed high feeding diversity, which could correspond to a good or high ecological status (ES) except at one location, that occasionally showed low feeding diversity. This poor condition was essentially due to low water renewal and extreme environmental variation of some parameters, such as salinity. At some locations an intermediate feeding diversity was observed mainly due to natural accumulation of organic matter. Other commonly used indices also point out to the same tendencies.We propose the evenness feeding diversity estimate approach as a practical and apparently robust method to estimate the ES of shallow waters, which can be used together with other common indicators. This approach has also the advantage of showing low sensibility to small samples and to low taxonomic identification effort.     

Plant traits as predictors of woody species dominance in climax forest communities

Abstract. The dominance of a given tree or shrub species in a particular forest community may be determined by many ecological traits of the target species, as well as those of the surrounding species as its potential competitors. The present study was conducted to evaluate the possibility of predicting community status (species composition and dominance) on the basis of traits of local flora using statistical methods, and to visualize the mathematical function which determines species dominance. A general linear model and logistic regression were used for the statistical analysis. Dependent variables were designated as dominance and presence/absence of species in climax forest, with independent variables as vegetative and reproductive traits. Subalpine, cool‐temperate, warm‐temperate and subtropical climax rain forests in East Asia were studied. Quantitative prediction of climax community status could readily be made based on easily measured traits of local flora. Species composition and 74.6% of the total variance of species dominance were predicted based on two traits; maximum height and shade tolerance. Through application of this method, the capacity of an alien species to invade a climax forest community could possibly be predicted prior to introduction of the alien species.     

Vertical distribution of the prokaryotic cell size in the Mediterranean Sea

Distributions of prokaryotic cell size and morphology were studied in different areas of the Mediterranean Sea by using image analysis on samples collected from surface down to bathypelagic layers (max depth 4,900?m) in the Southern Tyrrhenian, Southern Adriatic and Eastern Mediterranean Seas. Distribution of cell size of prokaryotes in marine ecosystem is very often not considered, which makes our study first in the context of prokaryotic ecology. In the deep Mediterranean layers, an usually-not-considered form of carbon sequestration through prokaryotic cells has been highlighted, which is consistent with an increase in cell size with the depth of the water column. A wide range in prokaryotic cell volumes was observed (between 0.045 and 0.566?μm³). Increase in cell size with depth was opposed to cell abundance distribution. Our results from microscopic observations were confirmed by the increasing HNA/LNA ratio (HNA, cells with high nucleic acid content; LNA, cells with low nucleic acid content) along the water column. Implications of our results on the increasing cell size with depth are in the fact that the quantitative estimation of prokaryotic biomass changes along the water column and the amount of carbon sequestered in the deep biota is enhanced.     

Diversity of aquatic prokaryotic communities in the Cuatro Cienegas basin

The Cuatro Cienegas basin (Coahuila, México) is a composite of different water systems in the middle of the desert with unusually high levels of endemism and diversity in different taxa. Although the diversity of macrobiota has been well described, little is known about the diversity and distribution of microorganisms in the oligotrophic ponds. Here we describe the extent and distribution of diversity found in aquatic prokaryotic communities by analysis of terminal restriction fragment length polymorphisms (T-RFLP) of 16S rRNA genes and phylogenetic analysis of cloned genes. Twelve locations within the basin were sampled. Among all the samples, we found a total of 117 operational taxonomic units (OTUs) using T-RFLPs, which ranged in any single sample from four to 49. OTU richness and Shannon diversity indices for different sites varied, but none were particularly high. 16S rRNA gene sequence data showed 68 different phylotypes among 198 clones. The most abundant phylotypes were Gamma- and Betaproteobacteria, and extreme halophiles. The differences among sites were significant; 45 TRFs were found only once, and 37% of the total diversity was represented by differences between sites, suggesting high beta-diversity. Further studies are needed to test whether this is a direct consequence of environmental heterogeneity in the basin.     

Changes in the ecological balance of invertebrate communities in kelp holdfast habitats of some polluted North Sea waters

Summary 1. This paper presents a thirty-one month study of a neotenous invertebrate community which developed inLaminaria hyperborea holdfasts in some polluted waters of the North Sea (northeast England und southwest Scotland).2. Sixty miles of open coastal waters and approximately thirty miles of the Forth Estuary are affected by pollutants.3. Reduction in the species diversity leaves only one possible detritus food chain in the habitat.4. This simple community is not in balance.5. The ecology of the polluted water community is considered and the possible long-term effects of pollution in the kelp forest are discussed.

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Veränderungen des ökologischen Gleichgewichts von Invertebraten-Lebensgemeinschaften in Habitaten der Haftorgane von Tangen einiger verunreinigter Nordseegewässer

Kurzfassung Die durch Wasserverunreinigungen bedingten räumlichen und zeitlichen Veränderungen der Lebensgemeinschaften von Invertebraten, die auf dem Haftorgan der BraunalgeLaminaria hyperborea Gunn. Fosle siedeln, wurden untersucht. Alle Beobachtungen beziehen sich auf die nordöstliche Küste Englands und die südwestliche Küste Schottlands. Die Arbeit schließt sich an eine frühere Veröffentlichung (Jones 1971) an, in der die chemischen, physikalischen und biologischen Faktoren behandelt wurden, welche die verschmutzten Küstengebiete charakterisieren. Dabei wurde unterschieden zwischen der jährlichen Zuwachsrate des Haftorgan-Habitats (gemessen in mm³ ecospace) und der Besiedlungsrate (ecoperiod). Die Ergebnisse zeigen, daß die Entwicklung der Epifauna aufLaminaria hyperborea in einem Radius von ungefähr 50 km um den Firth of Forth und in einem Bereich von 100 km in offenen, verschmutzten Küstengewässern verlangsamt ist. In verunreinigten Küstengewässern entsteht eine wenig stabile Nahrungskette, die sich auf Detritus aufbaut. Der periodische Verlust einiger nur kurzfristig siedelnder Arten scheint zu bewirken, daß sich die Biozönose nicht unabhängig von benachbarten, in unverschmutzten Gebieten vorkommenden marinen Gemeinschaften entwickeln kann. Die möglichen Dauerfolgen der Verschmutzung auf derartige neotene Lebensgemeinschaften werden diskutiert.

     

Biomass-size spectra in aquatic communities in shallow fluctuating Mediterranean salt marshes (Emporda wetlands, NE Spain)

The distribution of biomass among phytoplankton and free-livinginvertebrates was analysed in a shallow Mediterranean salt marshsubmitted to fluctuating water level. Among phytoplankton, biomassaccumulated in sizes dominated by mixotrophic species, indicatinga competitive advantage for these species, which also prey onother smaller primary producers. Among invertebrates, biomassaccumulated in the larger sizes, corresponding to species whichpartially exploit other nearby systems, such as the aerial environment(insects), or to those able to exploit particulated organicmatter in marsh-bed sediment (amphipods). Biomass distributionmodels developed for pelagic systems are discussed in relationto fluctuating temporary waters. The integrated spectrum approximated(r² = 0.96) a Pareto distribution with a slope of c = 1.38.Intense disturbances caused a decrease in r² and an increasein c. Under stable conditions, two different tendencies wereobserved, depending on the degree of eutrophy of the basins:higher values of c were measured in the more eutrophic basins,and lower values in the less eutrophic ones. We hypothesizethat highly irregular nutrient input could explain these differences.     

Climax epiphytic communities in Mediterranean Spain

The Antitrichetalia curtipendulae epiphytic climax communities of Šmarda & Hadàč from the Spanish Mediterranean area have been classified by numerical and traditional floristic methods. Ninety-eight phytosociological relevés have been recorded from a number of Iberian forests. Our results indicate two clusters that can be easily related to two different alliances: Lobarion pulmonariae (Nephrometum resupinati) and Pterogonio gracile-Antitrichion californicae (Antitrichielum californicae). A phytogeographical and syntaxonomical discussion is followed by a suggested Red List of threatened lichens and bryophytes occurring in these communities in the Spanish Mediterranean area with the aim of advancing conservation of endangered and vulnerable species.     

Temporal dynamics of prokaryotic communities in the marine sponge Sarcotragus spinosulus

In spite of their putative relevance to host functioning, in‐depth knowledge of sponge microbiome stability over time is scarce. This study tackles the temporal maintenance of bacterial and archaeal assemblages in the model host Sarcotragus spinosulus along three successive years. Prokaryotic communities were profiled by polymerase chain reaction‐denaturing gradient gel electrophoresis (PCR‐DGGE) and 454‐pyrosequencing of S. spinosulus‐derived 16S rRNA gene amplicons. Prevailing bacterial phyla were Actinobacteria, Acidobacteria, Proteobacteria, Poribacteria, PAUC34f, Chloroflexi and Bacteroidetes, with Bacteroidetes, Chloroflexi and Poribacteria showing different abundances over the years. At the approximate species level (operational taxonomic units, OTUs, defined at 97% sequence similarity), no major changes in bacterial richness and composition were found through time. Nearly 50% of all detected bacterial symbionts (96 in 205 OTUs) were recovered from all sampling years, whereas a taxonomically equivalent community of less dominant bacteria characterized the transient sponge microbiota. Despite the evidence for temporal symbiont maintenance, an intriguing cumulative degree of variation between individuals was unravelled, with all the surveyed sponge specimens sharing only 27 bacterial OTUs. Archaeal communities were dominated by one single symbiont of the candidate genus Nitrosopumilus (Thaumarchaeota), known for its ability to aerobically oxidize ammonia to nitrite. Only few bacterial ammonia oxidizers consistently occurred in S. spinosulus across the years as documented by PCR‐DGGE fingerprinting. In conclusion, prokaryotic symbionts of S. spinosulus display a state of dynamic stability shaped by the interplay between the maintenance of dominant players and turnover of less prevalent community members, in time and across host individuals, with no apparent consequences to holobiont functioning.     

Areas of shallow water in the North Atlantic

We report here estimates of the areas of water that are between 1 and 100 m and between 1 and 200 m deep in the North Atlantic, including the Caribbean Sea, the Gulf of Mexico, Hudson Bay and the North Sea, but excluding estuaries. The total areas within these depths, from the equator to 70° N, are 3.91 × 10⁶ km² and 5.66 × 10⁶ km², respectively. We also report the respective areas by selected geographic regions.     

Competitive dominance in the organisation of Mediterranean ant communities

1. Competition by dominant species is thought to be key to structuring ant communities. However, recent findings suggest that the effect of dominant species on communities is less pronounced than previously assumed. 2. The aim of the present study was to identify the role of dominant ants in the organisation of Mediterranean communities, particularly the role of competition in invaded and uninvaded communities. The effects on ant assemblages of two dominant ants, the invasive Argentine ant and the native ant, Tapinoma nigerrimum Nylander, were assessed. 3. The abundances of both dominant ants were significantly correlated with a decrease in native ant richness at traps. However, only the invasive ant was associated with a reduction in diversity and abundance of other ant species at site scale. In the presence of T. nigerrimum, species co‐occurrence patterns were segregated or random. Community structure in both the dominant‐free and the Argentine ant sites showed random patterns of species co‐occurrence. 4. The present findings indicate that dominant ants regulate small‐scale diversity by competition. However, at the broader scale of the assemblage, T. nigerrimum may only affect species distribution, having no apparent effect on community composition. Moreover, we find no evidence that inter‐specific competition shapes species distribution in coastal Mediterranean communities free of dominant ants. 5. These results show that dominant species may affect ant assemblages but that the nature and the intensity of such effects are species and scale dependent. This confirms the hypothesis that competitive dominance may be only one of a range of factors that structure ant communities.     

The transport of fine-grained sediments in shallow waters

Modelling

The transport of fine-grained sediments in shallow waters