2,978 research outputs found
The role of coastal defence structures in channeling production in coastal ecosystems
No full textThis study assessed the interaction of coastal defence structures (CDSs), namely shore-parallel‘low crested breakwater structures’ (LCSs), design features and hydrodynamic regime on thequantity and timings of macroalgae deposition. The employed sampling strategy comprised aspatially and temporally stratitified approach of time-lapse photography of macroalgaedeposition, verified with field observations. Field surveys determined the associated ecologicalassemblages of the sediment infauna and rocky shore epifauna associated with the breakwaterscheme, as well as for two nearby beaches with groynes. Further analysis determined decayrates, decay processes, changes in C and N stable isotope values of dominant macroalgal speciesand the dependence of the faunal assemblages on the decaying macroalgae deposits. Temporalanalysis highlights the main factors driving macroalgal deposition were differences in springand neap tidal range, wave height and sea temperature. Greatest deposition occurred duringmonths of lower wave height and fewer storms, when filamentous red algae and ephemeralgreen algal species dominated. Results indicated to greater amounts of macroalgae depositsaround LCSs than around wooden or granite groynes. Beach elevation best explained the spatialvariation, both vertically and horizontally, in the benthic assemblages within the breakwaterscheme, with the abundance of detritivorous deposit feeders being significantly correlated withabundance of macroalgae deposits. Orientation of LCSs, relative to wave action, was animportant driver of epifaunal assemblages on the CDSs, with the eastward ends of thebreakwaters providing the optimum intermediate environment with regards to wave action,exhibiting the greatest abundances of epifauna. Stable isotope analysis showed that the carbonand nitrogen isotopic values of macroalgae changed during the decomposition and were bothspecies and time dependent. Isotope analysis illustrated that decaying macroalgae deposits wereof greater trophic importance to species within the LCS ecosystem where there was largemacroalgal deposition, than to species within the groyne ecosystem where macroalgaldeposition was lower. Key findings of the study illustrate the importance of decayingmacroalgae deposits for the local ecosystem via modification of food chain energy flows.Though the ecosystem benefits from this allochthonous resource, deposits may be a nuisancerequiring controlled human intervention
Intertidal Rocky Shore Communities of the Continental Portuguese Coast: Analysis of Distribution Patterns
No full textA general description of rocky shore distribution patterns (“zonation”) along the whole Portuguese coast is given to provide the context for comparisons of distribution patterns of mid-shore organisms. In order to test if there was any variation in species distribution and abundance in the upper and lower mid-shore zone (eulittoral) along the entire intertidal Portuguese coast, three main regions were studied (north, centre and south) and nine shores were visited in each region. At each one of the 27 locations, the shore was levelled and a general qualitative description was made, which also aided stratification of subsequent quantitative sampling. An upper zone (littoral fringe) characterised by the presence of encrusting lichens, small littorinid gastropods and cyanobacteria was found on most of the shores along the Portuguese coast. The mid-shore zone (eulittoral) is essentially dominated by barnacles and sometimes mussels. The distribution patterns observed on the lower shore (sub-littoral fringe) showed a distinction between northern shores, where large brown algae are present, and shores located in the central and southern regions, essentially dominated by red algal turf species. Multidimensional analysis and the ANOSIM test have revealed clear differences in the structure of the upper and lower mid-shore zone. Within each level, the northern region was considerably different from the south and central regions. SIMPER analysis revealed the species which contributed to the separation between shore levels and regions. It has also given important information on the geographical decline in abundance of species
GC-FID data of biocatalytic esterification reactions & NMR data of lignin characterization
No full textTabulated chromatographic data (GC-FID) from butyl butyrate esterification reactions. 13C and 31P NMR data from pine kraft lignin (BIOPIVA 100) and cationic pine kraft lignin. A list of sample code identifiers with their descriptions is available upon request from the author.<br
Complex interactions in a rapidly changing world: responses of rocky shore communities to recent climate change
No full textWarming of the planet has accelerated in recent years and is predicted to continue overthe next 50 to 100 yr. Evidence of responses to present warming in marine ecosystems include shiftsin the geographic range of species as well as in the composition of pelagic and demersal fish, benthicand intertidal assemblages. Here we provide a review of the changes in geographic distributions andpopulation abundance of species detected on rocky shores of the NE Atlantic over the last 60 yr. Thisperiod encompassed the warm 1950s, a colder period between 1963 and the late 1980s and the recentperiod of accelerating warming to levels above those of the 1950s. The likely consequences of theseresponses are then explored. To do this, a summary of the dynamic balance between grazers,macroalgae and barnacles in structuring mid-shore communities is given before outlining experimentalwork on interactions between key components of rocky shore communities. Modelling andquantitative forecasting were used to predict changes in community composition and dynamics in awarmer world and their consequences for ecosystem functioning discussed. We then identify areasthat need further work before making a case for the use of rocky shore species not just as inexpensiveindicators of change offshore, but as tractable models to explore the direct and indirect effects ofclimate change in marine and coastal ecosystems. We also provide a societal perspective emphasisingthe value of long-term studies in informing adaptation to climate change
The influence of canopy algae on vertical patterns of distribution of low-shore assemblages on rocky coasts in the northwest Mediterranean
No full textCanopy-forming algae have been shown to play a fundamental role in the maintenance of understorey assemblages on rocky shores. In the Mediterranean, low-shore habitats are often monopolised by canopy algae of the genus Cystoseira and, in particular, by the species Cystoseira amentacea var. stricta. Alternatively, low-shore habitats are dominated by turf-forming algae and/or mussels. Previous studies showed that loss of Cystoseira, by natural or anthropogenic disturbances, resulted in the increase of turfing algae. Here, we propose that turf-forming algae may act as colonisers from nearby habitats, specifically from lower portions of the shore. The following hypotheses were tested to investigate this proposition: (1) in presence of Cystoseira, the assemblage living under its canopy will be distinct, in terms of composition and structure, from that found lower on the shore, (2) if the canopy of Cystoseira was removed, the differences between the two assemblages would decrease or disappear, (3) the effects of the canopy would be more important than other causes of variability at the spatial scale investigated (hundreds to thousands of metres), and (4) that effects of removal of the canopy would be consistent through time. These hypotheses were tested by means of a canopy removal experiment, involving several spatial and temporal repetitions of the manipulation.The assemblage underneath the canopy of Cystoseira was distinct from that found immediately lower on the shore, but when the canopy was removed there were no differences between the two. The effects of the canopy were consistent at the spatial and temporal scales investigated. Several species living under the canopy disappeared and were replaced by turf-forming species, resulting in a homogenisation of the two habitats and in a drastic loss of habitat diversity. This study shows that Cystoseira can be considered a habitat-forming species, responsible for the maintenance of two distinct low-shore assemblages. In this light, its importance should be taken into account by policies aiming to preserve biodiversity on rocky shores
Meetresultaten Kunststof GC-elementen: Project C2: Oever- en Bodembescherming met GC
No full textAnome BV en het Innovatie Test Centrum van Rijkswaterstaat-DWW zijn samen met verschillende partners aan het onderzoeken in hoeverre Ground Consolidators (GC\u92s) interessant zouden kunnen zijn voor gebruik in Oever- en bodembescherming. De eerste fase van het onderzoek is afgerond en er is besloten om verdergaand onderzoek te doen. In verband met duurzaamheid van het materiaal, is ervoor gekozen om verder onderzoek te verrichten naar GC-elementen van kunststof. Dit onderzoek is gedaan door een drietal studenten van de TU Delft aan de faculteit Civiele Techniek. Voorliggend document bevat de meetresultaten van de kwali- en kwantitatieve experimenten die zijn uitgevoerd om de eigenschappen van kunststoffen GC\u92s en een pakket GC\u92s te bepalen
Meetresultaten Kunststof GC-elementen: Versie 4
No full textAnome BV en het Innovatie Test Centrum van Rijkswaterstaat-DWW zijn samen met verschillende partners aan het onderzoeken in hoeverre Ground Consilidators (GC\u92s) interessant zouden kunnen zijn voor gebruik in Oever- en bodembescherming. De eerste fase van het onderzoek is afgerond en er is besloten om verdergaand onderzoek te doen. In verband met duurzaamheid van het materiaal, is ervoor gekozen om verder onderzoek te verrichten naar GC-elementen van kunststof. Dit onderzoek is gedaan door een drietal studenten van de TU Delft aan de faculteit Civiele Techniek. Voorliggend document bevat de meetresultaten van de kwali- en kwantitatieve experimenten die zijn uitgevoerd om de eigenschappen van kunststoffen GC\u92s en een pakket GC\u92s te bepalen
Dynamics of near-shore vortices
No full textThis work addresses two problems: 1) the dispersion induced by a cloud of vortices near a straight coast-line when the bottom is flat and the coastal boundary is a vertical plane or when the bottom is a planar slope; 2) the dynamics of vortices moving over a planar sloping bottom. Vortices near a vertical boundary are studied by the well-known method of images. For a plane sloping bottom we describe and develop a model, first introduced by Peregrine (1996) that uses a sector of a vortex ring to model a vortex in a wedge of fluid, where the wedge is formed by the water surface and by the planar sloping bottom. Numerical simulations using these free-slip analytical models are used to investigate the dispersion of vorticity and of a passive tracer induced by clouds of vortices. The results of the two models are compared. The dispersion of vortices and particles is mainly affected by the formation of vortex dipoles. The shoreline sets a preferential direction for the dispersion process and the dispersion normal to the shoreline is generally smaller, or bounded when the vortices forming the dipole have different absolute circulation. The dispersion of particles is generally smaller than the dispersion of vortices. In the second part of this work the analytical model of Peregrine (1996) for vortices moving over a planar slope at an angle a with the horizontal is tested against a set of laboratory experiments. Experiments were made by studying the dynamics of a vortex dipole moving towards a planar sloping beach. We measured the minimum distance from the shoreline reached by the vortices and their along-shore speed. The parameter ranges examined were 3º≤α≤45º, and 1×103≤Re≤6×103 (where Re is the Reynold's number of the vortices). We find a good agreement between the predictions and the observations when Re >~ 1500
Variability and community organization in moderately exposed tropical rocky shore algal communities as influenced by different consumer groups
No full textTropical rocky shores have been described as diverse and having a complex variety of consumers. This wide array of consumers has been studied to shed light on the different roles of consumers, particularly grazers on rocky shores and how they affect the relative abundance and distribution of sessile algal prey. One of the aims of ecology is to clarify factors that regulate and structure the abundance, growth and relationship of predators and preys in each habitat. Grazing is known as one of the most important determinants of growth and distribution of rocky shore communities. In this study a comparison between the different effects of fishes, crabs and molluscan herbivores on the relative abundances of microalgae and macroalgae from micro (hundreds of microns) to medium (tens of meters to kilometers) scales of spatial variability was conducted. At the start of the experiment several hypotheses were forwarded: 1) that herbivores will reduce the density of microalgae and macroalgal cover causing a barren appearance and ultimately reducing algal diversity where grazing intensity is highest across treatments, sites and shores; 2) and where grazing pressure is low, algal cover and diversity will be high; 3) and that fishes and crabs contribute significantly to maintaining a high grazing pressure in the area and that fishes control the algal assemblage in benign environments. These were evaluated by exclusion experiments and quadrat counts to determine the effects of grazers on different functional groups of algae. Microalgal density was assessed indirectly by measuring chlorophyll a from rock chips taken from the treatment plots. Microspatial variability of different sites was assessed by scoring digital micrographs of rock chips also taken from treatment plots. Algal cover of treatment plots was assessed by using digital photos taken during forthnightly visits in all sites. The univariate and multivariate results show significant differences across treatments, sites and shores and even significant temporal differences. Microalgal abundance and erect algal cover in fenced plots were significantly different compared to the other treatments. Grazer removal effectively caused a completely different algal assemblage to develop through time in cage and fenced treatments while maintaining a mostly barren cover in most open and control set-ups. Species which are not typically present in shores have grown inside cage and fenced treatments during the period of manipulation. Molluscan herbivores are the most effective grazers in these shores and control the relative distribution of algae by restricting the recruitment success of algal sporelings particularly erect macroalgae. Herbivorous fishes and crabs do not directly influence algal sporelings since the early stages of algae are too small for them to handle. But both consumers complement the removal of turf forming algae. The observed over all grazing effects show that molluscs have greater impact than fishes and crabs combined; the effect of either fishes or crabs are equal. Hence, the impact of crabs and fishes on these shores are minimal, mainly affecting turf forming algae. Moreover, the observed spatial variability in algal assemblage from micro to medium scales is mainly driven by high grazing intensity. Thus, grazing acts as a highly effective top down control mechanism in these shores during the cool winter season.




Fate and transport of volatile organic compounds in glacial till and groundwater at an industrial site in Northern Ireland
No full textVolatile organic compound (VOC) contamination of subsurface geological material and groundwater was discovered on the Nortel Monkstown industrial site, Belfast, Northern Ireland. The objectives of this study were to (1) investigate the characteristics of the geological material and its influences on contaminated groundwater flow across the site using borehole logs and hydrological evaluations, and (2) identify the contaminants and examine their distribution in the subsurface geological material and groundwater using chemical analysis. This report focuses on the eastern car park (ECP) which was a former storage area associated with trichloroethene (TCE) degreasing operations. This is where the greatest amount of volatile organic compounds (VOCs), particularly TCE, were detected. The study site is on a complex deposit of clayey glacial till with discontinuous coarser grained lenses, mainly silts, sands and gravel, which occur at 0.45-7.82 m below ground level (bgl). The lenses overall form an elongated formation that acts as a small unconfined shallow aquifer. There is a continuous low permeable stiff clayey till layer beneath the lenses that performs as an aquitard to the groundwater. Highest concentrations of VOCs, mainly TCE, in the geological material and groundwater are in these coarser lenses at similar to 4.5-7 m bgl. Highest TCE measurements at 390,000 mu g L-1 for groundwater and at 39,000 mu g kg(-1) at 5.7 m for geological material were in borehole GA19 in the coarse lens zone. It is assumed that TCE gained entrance to the subsurface near this borehole where the clayey till was thin to absent above coarse lenses which provided little retardation to the vertical migration of this dense non-aqueous phase liquid (DNAPL) into the groundwater. However, TCE is present in low concentrations in the geological material overlying the coarse lens zone. Additionally, VOCs appear to be associated with poorly drained layers and in peat < 3.0 m bgl in the ECP. Some indication of natural attenuation as VOCs degradation products vinyl chloride (VC) and dichloromethane (DCM) also occur on the site
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