Seagrass ecophysiology meets ecological genomics: are we ready?

In March 2011, the Ecophysiology and Genetics Working Groups of the European Science Foundation COST Action ES 0906, entitled Seagrass Productivity: From Genes to Ecosystem Management, organized an exploratory workshop entitled “Linking Ecophysiology and Ecogenomics in Seagrass Systems”. The goal of the workshop was to discuss how to integrate comparative gene expression studies with physiological processes such as photosynthetic performance, carbon and nitrogen utilization and environmental adaptation. The main questions discussed for integrative research related to mechanisms of carbon utilization, light requirements, temperature effects and natural variation in pH and ocean acidification. It was concluded that the seagrass research community is still in the nascent stages of linking ecophysiology with genomic responses, as carbon and nitrogen metabolism of seagrasses have not been sufficiently well studied. Likewise, genomic approaches have only been able to assign meaningful interpretations to a handful of differentially expressed genes. Nevertheless, the way forward has been established.     

Using subsurface metazoan fauna to indicate groundwater–surface water interactions in the Nakdong River floodplain, South Korea

Hydrological interactions between surface water and groundwater (GW) can be described using hydrochemical and biological methods. Surface water–groundwater interactions and their effects on groundwater invertebrate communities were studied in the Nakdong River floodplain in South Korea. Furthermore, the GW-Fauna-Index, a promising new index for assessing the strength of surface-water influence on groundwater, was tested. The influence of surface water on groundwater decreased with increasing depth and distance from the river. While hydrochemistry prevailingly reflected the origin of the waters in the study area (i.e. whether alluvial or from adjacent rock), faunal communities seemed to display an affinity to surface-water intrusion. Fauna reacted quickly to changes in hydrology, and temporal changes in faunal community structure were significantly linked to the hydrological situation in the floodplain. The metazoan faunal community and the GW-Fauna-Index allow a distinction between surface and subsurface waters with varying degrees of exchange. The results indicate that hydrological conditions are reflected by faunal assemblages on a high spatiotemporal resolution, and that surface-water intrusion can be estimated using the GW-Fauna-Index.     

Current trends of space occupation by encrusting excavating sponges on Colombian coral reefs

Some sponges of the genus Cliona (Porifera, Hadromerida, Clionidae) simultaneously excavate and encrust calcareous substratum, competing aggressively for illuminated space with corals and other organisms. To interpret current trends of reef space occupation, the patterns of distribution and size of three Caribbean species were examined at San Andrés Island and Islas del Rosario in Colombia. While Cliona aprica was ubiquitous, C. caribbaea (= C. langae) preferred deep and protected reef zones, and C. tenuis shallow and wave‐exposed settings. In contrast to the effect on other excavating sponges, chronic exposure to raw sewage did not significantly increase the abundance of the studied sponges. Substratum occupation/availability ratios showed a positive tendency of the sponges toward certain coral skeletons, and a negative or neutral tendency toward calcareous rock, indicating that establishment may be easier on clean, recently dead coral than on older, heavily incrusted substratum. High relief generally limits sponge size to that of the illuminated portions of the substratum. A generally lower proportion of small individuals than of larger ones indicates currently low recruitment rates and low subsequent mortality. Successful events of higher recruitment seem to have occurred for C. tenuis. These are related to the massive acroporid coral die‐off in the early 1980s and to asexual dispersion during storms, resulting in a current 10% substratum cover. Reefs with high coral mortality were and/or are thus more susceptible to colonization and subsequent space occupation by these sponges, although relief may prevent space monopolization.     

Treatment of time derivative and calculation of flow when solving groundwater flow problems by Galerkin finite element methods

Two techniques connected with the use of the finite element Galerkin method for solving the linear parabolic differential equation describing unsteady groundwater flow in an anisotropic non-homogeneous aquifer are introduced. The first is a mode superposition technique for dealing with the time derivative which involves computing the smallest eigenvalues and associated eigenvectors of the matrices arising from the Galerkin method. It is shown how such a technique allows us to interpret the response of the groundwater level to input in terms of parallel linear reservoirs. It is further argued that if properly implemented, the technique will have computational advantages over standard finite difference methods, e.g. in the case when the input function is constant over relatively large time subintervals. The second is a technique based on so-called generalized flow formulae for calculating flow values across external or internal boundaries, posterior to obtaining the groundwater level values. The implementation of the technique in the case of linear triangular elements on an irregular grid is discussed. It is finally argued from simplified cases that, apart from guaranteeing a match with prescribed input, the technique may often be expected to give more accurate flow values than those obtained directly from the groundwater gradients.     

Molecular identification of ascaridoid nematodes from the deep-sea onion-eye grenadier (Macrourus berglax) from the East Greenland Sea

Macrourus berglax from the East Greenland Sea was studied for the presence of ascaridoid nematodes in 2001, 2002 and 2003. The fishes were collected between 278 and 413 m water depth using a benthopelagic net. Based on the amplification of the internal transcribed spacer ITS-1, 5.8S, ITS-2 and flanking sequences (=ITS+), three ascaridoid nematode species were identified. The prevalence of infestation during the 3 years ranged from 42.9% to 62.9% and 22.9% to 40.0% for the anisakids Anisakis simplex (s.s.) and Pseudoterranova decipiens (s.s.), respectively, and from 28.6% to 60.0% for the raphidascarid Hysterothylacium aduncum. A total of 18 specimens, two of each species and examination year, revealed no sibling species, suggesting a limited distribution of other ascaridoid siblings into the deep sea. The ITS-1, 5.8S and ITS-2 sequences of A. simplex (s.s.) from the East Greenland Sea did not differ from previously published sequence data (GenBank) from other regions in the Atlantic and Pacific oceans. The sequences of P. decipiens (s.s.) corresponded most closely to those of specimens from Richardson Bay, western Pacific, and differed in four positions (0.5%). They corresponded least to those of specimens from Japan (1.5%). The sequence data for H. aduncum differed in two positions in the ITS-1 (0.2%) and three positions in the ITS-2 (0.3%) from sequences from Japan. A high genetic similarity between the regions can be explained by (a) extensive final host migration in the case of A. simplex (s.s.), (b) an overlapping distribution of final host populations along the continental shelves for P. decipiens (s.s.) and (c) a low host specificity and large population size in the intermediate and final hosts for H. aduncum. The occurrence of the identified species in the macrourid fish underlines the potential of cosmopolitan ascaridoid nematodes to distribute not only horizontally but also vertically in the deep sea.     

Olivine phenocrysts of Hawaiian olivine tholeiite and oceanite

Olivine phenocrysts of Hawaiian tholeiites display a variety of textures and a variation in composition which is due to supercooled crystallization. The highest forsterite content measured is 91%, and the highest magnesia content estimated for a tholeiitic liquid is 17%, using the olivine geothermometer. The liquid of this composition may be either a primary magma or a primitive magma. It is not yet possible to specify any particular composition range for the primary Hawaiian tholeiites.     

Meio-epifaunal wood colonization in the vicinity of methane seeps

In deep-sea environments, plant remains of several origins are found, including branches, twigs, leaves, and wood pieces, among others. As most of the deep-sea bottoms are oligotrophic and nutrient-limited, plant remains provide an oasis of localized organic enrichment and a substrate for colonization. Sunken wood was suggested to play an important evolutionary role in the diversification of chemosynthetic ecosystems, possibly representing stepping stones for the colonization between vent and seep ecosystems. In order to understand colonization processes of the Pacific Costa Rican meio-epifaunal assemblages associated with sunken wood, a field experiment was conducted on Mound 12 (8°55.778′N, 84°18.730′W) at ~1,000 m water depth. Woodblocks were placed in four different habitats (Mussel beds, tube worms, near mussel beds, rubble bottoms), and different local environmental conditions (seepage-active and seepage-inactive sites). Seven experimental Douglas fir woodblocks (each 1,047 cm² in surface area) were deployed from the R/V Atlantis using the manned submersible Alvin in February 2009 and recovered after 10.5 months in January 2010. Sample processing and analyses led to a data set of abundance (total 9,951 individuals) and spatial distribution of nine meio-epifaunal higher taxa/groups. Meio-epifaunal densities on individual woodblocks ranged from 3 to 26 ind.10 cm². Copepods accounted for the highest abundances (75.1%), followed by nauplii larvae (11.7%) and nematodes (9.8%). The maximum number of individuals (26.3 ind.10 cm⁻²) was found in blocks placed in seepage-inactive areas (near active mussel beds) in contrast to 2.9 ind.10 cm⁻² in active areas (within a mussel bed). A hierarchical cluster analysis grouped blocks according to seepage activity and not to habitat, but tests of similarity showed no significant differences in higher taxon composition and abundances, probably owing either to substrate homogeneity or low sample size. Copepods were the most abundant representatives, suggesting that this group is one of the most successful in colonizing in the early stage of succession, in this case while hardwood substrates are not yet decomposed or bored by bivalves.     

LONG TERM EFFECTS OF REHABILITATION MEASURES ON BED LOAD TRANSPORT AT THE SALZACH RIVER

1 BASIC PROBLEMFlood protecton, sPreaing of settlements and occuPatin Of river valleys were maor reasons to damand lindt rivers throughout Europe in the ndd 19th century. Engineers of those days often knew very wellabout the effects of their plannings: shortening the river length would accelerat the now and thusencourage the erosion into the river's sedAnents. Two vital advanages could be obtalned from that kindof constrUction, landuse of the fOrmer flood plains on the one and increasin…