Late Cambrian hard substrate communities from Montana/Wyoming: the oldest known hardground encrusters

Hardground surfaces from the Late Cambrian Snowy Range Formation in Montana/Wyoming are the oldest known non-reefal hard substrates exhibiting encrusting fossils. These surfaces range in age from Early Franconian to early Trempealeauan. Hardgrounds were developed on slightly hummocky to planar, truncated surfaces of glauconite-rich, carbonate, flat pebble conglomerates, which were deposited during episodes of storm scouring in shallow subtidal environments of the Montana/Wyoming shelf. Snowy Range hardgrounds are encrusted by a low diversity assemblage of fossils dominated by simple discoidal holdfasts of pelmatozoans, probably crinoids, and including small conical spongiomorph algae? and probable stromatolites. Macroborings (e.g. Trypanites) are notably absent from all hardground surfaces, although sharp-walled, vertical, cylindrical holes (borings?) occur in micrite clasts imbedded in certain flat pebble conglomerates. No evidence of faunal succession or microecologic partitioning of irregular surfaces was observed on these Cambrian hardgrounds.     

The invasive green alga Avrainvillea sp. transforms native epifauna and algal communities on a tropical hard substrate reef

Some introduced species compete directly with native species for resources and their spread can alter communities, while others do not proliferate and remain benign. This study compares community structure and diversity in adjacent areas dominated by the introduced alga Avrainvillea sp. or native algal species on a hard substrate reef. The biomass and species composition of 15 paired plots (30 in total, plot type based on dominance of Avrainvillea sp. or native species) were quantified. Plots dominated by Avrainvillea sp. had a significantly different assemblage of species characterized by lower algal diversity, mostly Dictyota spp. and Laurencia sp., and a higher abundance and diversity of invertebrates, such as small arthropods, polychaetes, and brittlestars. These results suggest that as Avrainvillea sp. becomes more abundant on hard substrate reefs, it will engineer a different community composed of algal epiphytes and an invertebrate assemblage more typically associated with algae in soft sediments.     

Sublittoral soft bottom communities and diversity of Mejillones Bay in northern Chile (Humboldt Current upwelling system)

The macrozoobenthos of Mejillones Bay (23°S; Humboldt Current) was quantitatively investigated over a 7-year period from austral summer 1995/1996 to winter 2002. About 78 van Veen grab samples taken at six stations (5, 10, 20 m depth) provided the basis for the analysis of the distribution of 60 species and 28 families of benthic invertebrates, as well as of their abundance and biomass. Mean abundance (2,119 individuals m^?2) was in the same order compared to a previous investigation; mean biomass (966 g formalin wet mass m^?2), however, exceeded prior estimations mainly due to the dominance of the bivalve Aulacomya ater. About 43% of the taxa inhabited the complete depth range. Mean taxonomic Shannon diversity (H′, Log e) was 1.54 ± 0.58 with a maximum at 20 m (1.95 ± 0.33); evenness increased with depth. The fauna was numerically dominated by carnivorous gastropods, polychaetes and crustaceans (48%). About 15% of the species were suspensivorous, 13% sedimentivorous, 11% detritivorous, 7% omnivorous and 6% herbivorous. Cluster analyses showed a significant difference between the shallow and the deeper stations. Gammarid amphipods and the polychaete family Nephtyidae characterized the 5-m-zone, the molluscs Aulacomya ater, Mitrella unifasciata and gammarids the intermediate zone, while the gastropod Nassarius gayi and the polychaete family Nereidae were most prominent at the deeper stations. The communities of the three depth zones did not appear to be limited by hypoxia during non-El Niño conditions. Therefore, no typical change in community structure occurred during El Niño 1997–1998, in contrast to what was observed for deeper faunal assemblages and hypoxic bays elsewhere in the coastal Humboldt Current system.     

Meeresalgen von Helgoland

This report represents a photographic documentation of the more conspicuous species of the marine algal vegetation of the island Helgoland (North Sea), based on collections and observations made since 1959. The catalogue is largely restricted to macroscopic forms, as adequate knowledge of most of the microscopic ones is not yet available. Remarks on some rare species are added in a special chapter; the list includes some 150 species. With a few exceptions, the figures have been obtained from living algae; they illustrate aspects of reproduction and development and, occasionally, demonstrate different seasonal habits. The simplified key may be useful for providing a guide both for naturalists and students of marine phycology. In addition, this algal flora enhances our knowledge of the distribution of benthic species along the European coasts, as the rocky island of Helgoland intervenes between southern Norway and the shores of the English Channel.     

飞云江口附近海域浮游动物群落特征

根据2010—2011年在飞云江附近海域(27°46'N—27°75'N,120°66'E—121°01'E)秋、冬、春3个季节的调查资料,分析了浮游动物的种类组成及多样性分布、总丰度的平面分布和季节变化及其与水团变化的关系。结果表明:飞云江口附近水域秋、冬、春三季共鉴定出浮游动物60种,分属于11大类;秋季检出浮游动物9大类42种,冬季检出5大类20种,春季检出8大类34种;调查水域浮游动物丰度在秋、冬之间和冬、春之间有较大变化,秋、冬、春三季浮游动物平均丰度分别为221.69、19.52和137.50 ind·m-3;秋、冬、春季种类数近岸较少,外海较多;三季中,秋季浮游动物Shannon多样性指数最高,高值区位于调查水域的东南部,其次为春季,最高值出现在飞云江口外海域,冬季为三季最低,最高值出现在调查水域北侧岛群之间;中华哲水蚤(Calanus sinicus)是冬、春季影响总丰度变化最主要的种类,秋季总丰度变化主要受针刺拟哲水蚤(Paracalanus aculeatus)和百陶箭虫(Sagitta bedoti)影响;各水团随季节变化此消彼长共同作用于研究水域,对该水域浮游动物数量分布和群落组成产生相应的影响。     

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.     

Changes in the sublittoral hard substrate communities in the Oosterschelde estuary (SW Netherlands), caused by changes in the environmental parameters

In order to assess the effects of the execution of the Delta Project, the sessile sublittoral communities on hard substrates in the Oosterschelde estuary and the environmental parameters were quantitatively investigated from 1985 till 1990. During the construction period of the barrier, three communities were sampled in the photic zone and four in the aphotic zone. The distribution of the communities in the photic zone seemed to be determined by the exposition to water movement and depth, while the communities in the aphotic zone were restricted to geographic areas, with differences in tidal current velocities: the mouth of the estuary, the Hammen, the central part and the Zijpe. Two years after the completion of the enclosure works, the community structure changed rapidly, caused by decreases of tidal current velocities, increases of the amounts of sedimentation, especially of fine sediments, and an increase of the transparency of the water. Changes within the associated vagile animals showed the same tendency as the sessile communities: under less exposed conditions the number of organisms remained the same or increased, while at some locations this increase was nullified by increasing amounts of sedimentation.     

DieUlothrix-Arten von Helgoland. I

Zusammenfassung 1. Zur Kennzeichnung derUlothrix-Arten von Helgoland dienen entwicklungsge-schichtliche Befunde, weil morphologische Merkmale nicht zu ihrer Unterscheidung ausreichen.2. Die Fäden vonUlothrix acrorhiza nov. spec. vermehren sich nur durch Zoosporen. Die übrigen in dieser Mitteilung behandelten Arten haben einen Generationswechsel mit einzelligem Sporophyten.3.Ulothrix speciosa (Carm.) nov. comb. (=Ulothrix flacca) ist diözisch, die ihr morphologisch nahestehendeUlothrix flexuosa nov. spec. ist monözisch. Die Fäden beider Arten erzeugen nur Gameten. In den Sporophyten vonU. speciosa entstehen bewegliche Schwärmer, während die Aplanosporen vonU. flexuosa zu einem sternförmigen Fadenknäuel auskeimen.4. Die monözischen Fäden vonUlothrix subflaccida Wille, die morphologischU. acrorhiza entsprechen, bilden Gameten und Zoosporen aus. Die Sporophyten entlassen bewegliche Schwärmer. Unter optimalen Bedingungen schließt sich der Entwicklungskreis in etwa 25 Tagen.

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TheUlothrix-species of helgoland. I

This is the first taxonomic account onUlothrix-species from Helgoland based on culture and rearing experiments. Morphological properties alone have proved insufficient for a proper species characterization. Any diagnosis should take into consideration functional aspects as well. Of special importance are developmental features and life cycle stages. Two new species are being described: one of them is structurally quite similar toUlothrix speciosa (syn.:U. flacca according toWille's conception); the other differs fromU. subflaccida in reproducing only asexually.

     

Beta diversity of cold-water coral reef communities off western Scotland

Spatial heterogeneity in coral reef communities is well documented. This “species turnover” (beta diversity) on shallow warm-water reefs strongly conforms to spatial gradients in the environment as well as spatially autocorrelated biotic processes such as dispersal and competition. But the extent to which the environment and spatial autocorrelation create beta diversity on deep cold-water coral reefs such as those formed by Lophelia pertusa (Scleractinia) is unknown. The effects of remotely sensed and ground-truthed data were tested on the community composition of sessile suspension-feeding communities from the Mingulay Reef Complex, a landscape of inshore Lophelia reefs off the Scottish west coast. Canonical correspondence analysis determined that a statistically significant proportion (68%) of the variance in community composition could be explained by remotely sensed environmental variables (northerly and easterly aspect, seabed rugosity, depth), ground-truthed environmental variables (species richness and reef macrohabitat) and geospatial location. This variation was further partitioned into fractions explained by pure effects of the environment (51%), spatially structured environmental variables (12%) and spatial autocorrelation (5%). Beta diversity in these communities reflected the effects of both measured and unmeasured and spatially dependent environmental variables that vary across the reef complex, i.e., hydrography. Future work will quantify the significance and relative contributions of these variables in creating beta diversity in these rich communities.     

Zur Kenntnis derPorphyra-Arten von Helgoland

Zusammenfassende Schlußbetrachtung Von den fünf bei Helgoland vorkommendenPorphyra-Arten können drei eine weitgehende Ähnlichkeit ihrer äußeren Form zeigen. Es ist jedoch nach eingehenden Vergleichen und Beobachtungen ohne weiteres möglich, diese Arten auseinanderzuhalten. Entfällt dagegen an einem Küstenabschnitt eine solche Vergleichsmöglichkeit, so kann die Variabilität des Habitus leicht dazu führen, die verschiedenen Erscheinungsformen einer einzigen Art mehreren der beschriebenen Taxa zuzuordnen. Im Gegensatz zu der relativen Bestimmung nach den variablen äußeren Merkmalen desPorphyra-Stadiums bietet das gut gekennzeichneteConchocelis-Stadium die Grundlage für eine absolute Bestimmung der Arten. Durch planmäßige Untersuchung der Porphyren anderer Meeresgebiete mit der in dieser Arbeit angewandten Methode können die Artdiagnosen ergänzt und die Echtheit der beschriebenen Arten geprüft werden.(Mit 12 Abbildungen im Text)     

Deep-sea meiobenthic communities underneath the marginal ice zone off Eastern Greenland

Marginal ice zones (MIZ) are known to be the most highly productive systems in the Arctic Ocean with large amounts of primary production reaching the deep seafloor. This study characterizes the effect of the ice-edge related primary production and subsequent phytodetritus sedimentation on deep-sea meiobenthic communities, particularly nematodes, along the Eastern Greenland continental margin in July 2000. Results were based on data from six stations along a depth transect crossing the MIZ with the shallowest stations under the ice-cover (656 and 1,198 m), intermediate stations at the ice-edge (1,560 and 2,129 m), and deepest stations in ice-free areas (2,735 and 3,033 m). The presence of the ice-cover significantly affected the availability of organic matter on the deep seafloor. The present results confirm a close bentho-pelagic coupling in the area of investigation. Enhanced flux of phytodetritus from primary production to the benthic system appears at stations underneath or close to the ice-edge and at the sampling sites in ice-free areas. The availability of phytodetritus at these stations enhanced bacterial activities, meiofauna abundances, and the number of nematodes species. Electronic supplementary material Supplementary material is available in the online version of this article at and is accessible for authorized users.     

Recurrent disturbances and the degradation of hard coral communities in taiwan

Recurrent disturbances can have a critical effect on the structure and function of coral reef communities. In this study, long-term changes were examined in the hard coral community at Wanlitung, in southern Taiwan, between 1985 and 2010. In this 26 year interval, the reef has experienced repeated disturbances that include six typhoons and two coral-bleaching events. The frequency of disturbance has meant that species susceptible to disturbance, such as those in the genus Acropora and Montipora have almost disappeared from the reef. Indeed, almost all hard coral species have declined in abundance, with the result that total hard coral cover in 2010 (17.7%) was less than half what it was in 1985 (47.5%). In addition, macro-algal cover has increased from 11.3% in 2003 to 28.5% in 2010. The frequency of disturbance combined with possible chronic influence of a growing human population mean that a diverse reef assemblage is unlikely to persist on this reef into the future.     

The pattern of recovery of disturbed microbial communities inhabiting hard substrates

The recovery of microbial communities removed from hard substrates was studied in the laboratory and on microepiphyton in the White Sea, in St. Petersburg, and in Karelija. The removal of these communities from hard substrates destroyed their spatial structure. Recovery was allowed to proceed from the suspension on a horizontal substrate in stagnant water at low temperature. The sequence of colonization in the laboratory was the same as that in the field. Laboratory recovery was complete in 12–24 h and did not depend on the age of the natural community. From the comparison between laboratory and field data on such mechanical disturbance, a pattern of recovery, termed ‘self-assembly’, is proposed. This revised version was published online in September 2006 with corrections to the Cover Date.     

Hypolithic microbial communities: between a rock and a hard place

Drylands are the largest terrestrial biome on Earth and a ubiquitous feature is desert pavement terrain, comprising rocks embedded in the mineral soil surface. Quartz and other translucent rocks are common and microbial communities termed hypoliths develop as biofilms on their ventral surfaces. In extreme deserts these represent major concentrations of biomass, and are emerging as key to geobiological processes and soil stabilization. These highly specialized communities are dominated by cyanobacteria that support diverse heterotrophic assemblages. Here we identify global-scale trends in the ecology of hypoliths that are strongly related to climate, particularly with regard to shifts in cyanobacterial assemblages. A synthesis of available data revealed a linear trend for colonization with regard to climate, and we suggest potential application for hypoliths as 'biomarkers' of aridity on a landscape scale. The potential to exploit the soil-stabilizing properties of hypolithic colonization in environmental engineering on dryland soils is also discussed.     

Sublittoral abundance and food consumption of Baltic gobies

Two small demersal fishes, the sand goby Pomatoschistus minutus and the common goby Pomatoschistus microps , were quantified on soft bottoms at 20–40 m depth in the Baltic Sea, using a camera placed above the bottom. The largest numbers of gobies were seen following the settlement of young in late summer and autumn. Most recorded fishes were sand gobies. An annual average of 4·7 individuals m⁻²(0·24 g dry mass m⁻²) was recorded in 1983–1985 and 2·5 individuals m⁻²(0·13 g m⁻²) in 1997–1998. Using these densities, the annual goby food consumption was estimated to 100 kJ m⁻² in 1983–1985 and 50 kJ m⁻² in 1997–1998, corresponding to most of the annual macrobenthos production available to the gobies. The resulting goby production, assumed equal to 25% of the food consumed, must have been an important food source for the larger fishes occasionally recorded in the photographs.