Search

Studies the aggregation of sublittoral macrobenthos in Moreton Bay, Queensland. Examination of the of time changes in the benthos; Indications showing a close power curve relationship between variances for most species in the area; Accuracy of benthic sampling in elucidating seasonal and annual changes of the biotic communities and their environment.

Relates the results of a quantitative survey of sublittoral organisms in polluted and unpolluted waters near Marseilles, France. Low biomass of the Mediterranean sea grass in the polluted Gulf of Marseilles compared with unpolluted bays near Marseilles; Low number of crops in shallow water; Absence of sea grass along the most polluted coastline near the main sewer outlet at Cortiou.

A study was made of the sub-littoral benthic environment of Ellis Fjord, a 10 km-long fjord located near Davis Station, in the Vestfold Hills, Antarctica, over a 15 mo period (November 1984 to February 1986). Data were collected by SCUBA diving and underwater photography and were inhitially analysed by ordination techniques (non-metric multidimensional scaling). Ordinations showed substratum type to be the factor most strongly associated with changes in the distribution and abundance of macrobenthic species within the fjord. Other factors shown to be associated with changes in macrobenthic species assemblages were depth, distance from the fjord mouth, bottom slope, shoreline characteristics, current speed, and the presence of low-salinity water at shallow depths during the summer melt. The four major substratum types in Ellis Fjord were sand, rock, Serpula narconensis colonies and Phyllophora antarctica thalli. S. narconensis colonies supported the most species and sand substrate supported the least. P. antarctica is the only macrophyte species which occurred in the fjord. S. narconensis colonies in Ellis Fjord from one of the largest known tubeworm reefs in the world. The assemblages of benthic species in Ellis Fjord were different from those seen at other sub-littoral benthic sites off the Vestfold Hills, and at other Antarctic sites. There was a far greater proportion of filter-feeding species in the fjord than at other sub-littoral benthic sites off the Vestfold Hills. Factors which are thought to have caused these differences are the high level of organic but low level of inorganic input into the benthic system of the fjord, and the absence of anchor ice from the fjord. [ABSTRACT FROM AUTHOR]

Reports on lithification caused by inorganic precipitation of high-magnesium calcite from several localities in the Mediterranean. Micritic calcite cement; Lithification of internal sediments and formation of open-space fillings within a sublittoral algal framework; Gradual obliteration of the biogenic structures.

The article focuses on a survey of sublittoral seaweeds found in the coastal areas from Dunbar, Scotland to Fast Castle, Scotland. It mentions that the inshore waters of the coast remain well aerated due to the exposure of the coast to the North Sea. It states that small sandy bays occur along the coast in which considerable quantities of sublittoral seaweed are cast during certain seasons. It informs that seaweed found upto a depth of 7 fathoms mostly includes a pure growth of L.cloustoni and seaweed in measurable quantity was not found below 7 fathoms.

The article offers information on a research on the intertidal ecology of rocky shores in South Pembrokeshire in Wales. It states that approximately 15 miles of coastline were included in the survey, extending from Manorbier Bay on the west to Telpyn Point on the east. It also forwards that the region may be considered under four various categories. These are the Old Red Sandstone of Manorbier and Old Castle Head, the Carboniferous Limestone of Lydstep, Tenby Peninsula, Giltar Cliffs, and St. Catherine's Island, and an area of small bays eroded in the Millstone Grits. Moreover, it mentions that the sea has cut deeply into the Coal Measures to form Waterwynch Bay, leaving the harder sandstones of Monkstone and Telpyn Point as headlands.

The article presents a study on the effects of water current in the ecology of Lough Ine Rapids in Ireland. Lough Ine, a marine lake about 1 kilometer long and 50 meters deep, opens southwards by Rapids, narrow channel, into Barloge Creek towards Atlantic. Preliminary studied is on Hydrography of Rapids, It shows resistance of water flow modified the tidal rhythm in Lough. It is revealed that Rapids act as control section during outflow so outflow rate is independent of sea water level. The measure of current speed with watts meter, fastest current is always in the down stream side and highest reading gotten was 3 meters per second about 6 knots. There is a distribution of laminarian algae that formed canopy. Several diagrams are presented.

The article discusses a study which investigates the sublittoral seaweeds in Scapa Flow and Bay of Firth in Orkney, Scotland. The researcher has divided the study into three parts, which include the development of the view box, survey of the Scapa Flow and the survey of the Bay of Firth. Moreover, the researcher aims to determine the sublittoral seaweeds condition and develop preservations plan using the view box. Accordingly, using the view box method in the survey, the result indicates that it is possible to survey sublittoral zone with an increasing accuracy through small motor-boat. Moreover, the result shows that Laminaria species, which are common in Scottish coast, grow below 17 meters from sea level.

We examined nitrogen cycling over a 1-yr period in shallow, sandy sediments at two contrasting sites near a barrier island in the northeastern Gulf of Mexico, and we provide here the direct determination of dinitrogen gas (N2) production at ambient nitrate concentrations in permeable marine sediments. Nitrogen-stable isotope tracer techniques were used to quantify N2-production rates and pathways in sediment cores and slurries. To simulate pore-water advection, the dominant transport process in the upper layer of the permeable sand beds, intact sediment cores were perfused with aerated seawater. This perfusion increased denitrification rates up to 2-fold in Apalachicola Bay sands and up to 17-fold in Gulf of Mexico sublittoral sands, respectively, relative to static cores. Seasonal N2-production rates were highest in spring and fall. Denitrified nitrate originated almost entirely from benthic nitrification at the exposed Gulf site, whereas water-column nitrate dominated sedimentary denitrification at the sheltered Bay site. Sediment incubations in stirred chambers were used to determine net fluxes of oxygen (O2), N2, nitrate, and ammonium across the sediment-water interface during varied degrees of continuous pore-water exchange. Rates of N2 efflux correlated with rates of pore-water flow increasing from 0.12 mmol N m-2 d-1 under diffusion-limited transport conditions up to 0.87 mmol N m-2 d-1 with pore-water advection. Mineralized nitrogen was completely converted to N2 gas in Gulf of Mexico sediments. Our results demonstrate that advective pore-water circulation will accelerate benthic N2 production by coupled nitrification-denitrification and that substantial nitrogen loss occurs from coastal permeable sediments. [ABSTRACT FROM AUTHOR]

We identified microbial taxa that catalyze phytodetritus degradation and denitrification in permeable coastal sediments of the northeast Gulf of Mexico. Stable isotope probing experiments were used to track the assimilation of isotopically labeled substrate into bacterial deoxyribonucleic acid (DNA) and directly link the taxonomic identification of benthic microorganisms with particulate organic matter degradation and denitrification activity. Phytodetritus deposition events were simulated in the laboratory by the addition of 13C-enriched, heat-killed Spirulina cells to intact sediment core incubations. Immediate increases in O2 consumption (3-fold), N2 efflux (16-fold), and dissolved inorganic nitrogen efflux were observed after phytodetritus addition relative to unamended treatments, suggesting that the benthic microbial community was poised to immediately begin oxidizing deposited organic matter. Analyses of 16S ribosomal ribonucleic acid gene sequences amplified from 13C-enriched DNA fractions demonstrated that members of the Gammaproteobacteria (Vibrionales and Alteromonadales), Deltaproteobacteria, Actinobacteria, Verrucomicrobia, and Planctomycetes metabolized the phytodetritus amendment. Terminal restriction length polymorphism analyses showed increases in the relative abundance of Gammaproteobacteria, Planctomycetes, and Bacteroidetes with phytodetritus addition. Alphaproteobacteria were identified as metabolically active denitrifiers by phylogenetic analysis of nitrous oxide reductase gene sequences from 13C-enriched DNA fractions. This study provides the first identification of microorganisms responsible for organic matter degradation in marine sediments by DNA sequence analysis. Microbial assemblages recognized for high-molecular-weight organic matter oxidation in the marine water column were important in catalyzing these processes in permeable sediments. [ABSTRACT FROM AUTHOR]

Opportunistically, the limpet Patella vulgata will switch from microphagous grazing to feeding on attached macroalgae or, a novel finding, on accumulations of stranded seaweeds. Macroalgal food is ingested primarily at night during emersion, when the thalli come to lie on the rock surface and are sufficiently damp. Monocultures of Ascophyllum nodosum are not immune to the destructive effects of limpets as previously thought. Patella vulgata can graze them down to complete disappearance, thus pushing Ascophyllum back to refuges where P. vulgata is absent or rare. Such refuges were found along a wide range from very sheltered to strongly wave-exposed rocky shores in Brittany, France. By a combination of its macrophagous and microphagous feeding habits, P. vulgata can control mid-tidal macroalgal assemblages in a similar fashion to the action of sea urchins upon kelp communities inhabiting the lower intertidal and shallow sublittoral zones of rocky shores. [ABSTRACT FROM AUTHOR]

The enclosed Baltic Sea, one of the world’s largest brackish water basins, resembles a large estuary with steep horizontal and vertical environmental gradients. Thus, salinities range from 25 to 30 ppt in the Danish Sound area in the south to 1–3 ppt in the inner reaches of the Gulfs of Bothnia and Finland, and a persistent pycnocline in the Baltic basin causes stagnation of bottom waters for long periods, with periodic hypoxia/anoxia as a consequence, over an area covering up to 100 000 km[sup 2]. Further, climatic variation from boreal to subarctic causes additional stress on the ecosystem. In recent decades, eutrophication and pollution have also significantly affected the biota of the Baltic Sea. The soft bottom infauna is poor in terms of species composition, and functional complexity is considered to be low. This paper examines the estuarine soft bottom infauna of the Baltic Sea along some principal environmental gradients using a functional-group perspective. We have used the functional-group concept (primarily feeding type, mobility and microhabitat), designed for polychaetes by Fauchald and Jumars (1979), to analyze and illustrate if and how the environmental gradients are reflected in the zoobenthos. A total of 25 functional groups were identified, forming clines from complex functional communities in the south and west, towards functionally poor assemblages in the north and east. The shift in functional groups indicates a loss of carnivores, tentaculate sessile organisms, and burrowers from areas beyond the Baltic and its marine approaches towards the inner bays. On the other hand, suspension feeders and surface deposit feeders increase in importance. In the northernmost areas of the Baltic only 1–3 functional groups are found, compared to 8–20 in the south. [ABSTRACT FROM AUTHOR]