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NE Atlantic (ne + atlantic)
Selected AbstractsEarly juvenile development of deep-sea asteroids of the NE Atlantic Ocean, with notes on juvenile bathymetric distributionsACTA ZOOLOGICA, Issue 1 2001Paulo Y. G. Sumida Abstract The postmetamorphic ontogenesis of 11 deep-sea asteroid species is described. Juvenile bathymetric distributions are compared to adults. The deep-sea juvenile asteroids of the NE Atlantic could be distinguished to species level from a very early stage of development. In all species, except Porcellanaster ceruleus and Plinthaster dentatus, the arms grow faster than the body. In Porcellanaster ceruleus and Plinthaster dentatus, early growth is nearly isometric. In the appearance of the epiproctal cone, the change in form of the furrow and apical spines, the early development of the cribriform organ adjacent to the madreporite and the appearance of sediment in the stomach indicate that Porcellanaster ceruleus is likely to undergo a shift in habitat and diet during the juvenile phase. Porcellanaster ceruleus is probably a predator on meiofauna and small macrofauna during the early stages of life, changing to a burrowing lifestyle ingesting sediment particles. Juvenile sea stars showed wider bathymetric distributions than their adult counterparts, suggesting that events occurring during the early stages of life are important for the maintenance of the local population structure and diversity in the deep NE Atlantic. [source] Bacteria in the cold deep-sea benthic boundary layer and sediment,water interface of the NE AtlanticFEMS MICROBIOLOGY ECOLOGY, Issue 2 2000Carol Turley Abstract This is a short review of the current understanding of the role of microorganisms in the biogeochemistry in the deep-sea benthic boundary layer (BBL) and sediment,water interface (SWI) of the NE Atlantic, the gaps in our knowledge and some suggestions of future directions. The BBL is the layer of water, often tens of meters thick, adjacent to the sea bed and with homogenous properties of temperature and salinity, which sometimes contains resuspended detrital particles. The SWI is the bioreactive interface between the water column and the upper 1 cm of sediment and can include a large layer of detrital material composed of aggregates that have sedimented from the upper mixed layer of the ocean. This material is biologically transformed, over a wide range of time scales, eventually forming the sedimentary record. To understand the microbial ecology of deep-sea bacteria, we need to appreciate the food supply in the upper ocean, its packaging, passage and transformation during the delivery to the sea bed, the seasonality of variability of the supply and the environmental conditions under which the deep-sea bacteria grow. We also need to put into a microbial context recent geochemical findings of vast reservoirs of intrinsically labile organic material sorped onto sediments. These may well become desorped, and once again available to microorganisms, during resuspension events caused by deep ocean currents. As biotechnologists apply their tools in the deep oceans in search of unique bacteria, an increasing knowledge and understanding of the natural processes undertaken and environmental conditions experienced by deep-sea bacteria will facilitate this exploitation. [source] The influence of environment and spawning distribution on the survival of anchovy (Engraulis encrasicolus) larvae in the Bay of Biscay (NE Atlantic) investigated by biophysical simulationsFISHERIES OCEANOGRAPHY, Issue 6 2007GWENHAEL ALLAIN Abstract A growth and survival model of the early life stages was run along virtual drift trajectories tracked in a hydrodynamic model to simulate the annual recruitment process of anchovy (Engraulis encrasicolus) in the Bay of Biscay (NE Atlantic). These biophysical simulations concerning three different years were analysed in order to investigate the influence of environment and spawning dynamics on the survival of larvae and juveniles. The location of space,time survival windows suggested major environmental mechanisms involved in simulated recruitment variability at the different scales , retention of larvae and juveniles in favourable habitats over the shelf margins and turbulence effects. These small-scale and meso-scale mechanisms were related to the variations in wind direction and intensity during spring and summer. Survival was also variable according to the origin of the drift trajectories, that is spawning distribution in space and time. The observed spawning distribution (according to field surveys) was compared with the spawning distribution that would maximize survival (according to the biophysical model) on a seasonal scale, which revealed factors not considered in the biophysical model (e.g. spawning behaviour of the different age classes). The variation of simulated survival according to spawning distribution was examined on a multi-annual scale and showed a coherent pattern with past and present stock structures. The interaction processes between the population (influence on spawning) and its environment (influence on survival) and its implications on recruitment and stock dynamics are discussed. [source] Detrimental effects of recent ocean surface warming on growth condition of Atlantic salmonGLOBAL CHANGE BIOLOGY, Issue 5 2008CHRISTOPHER D. TODD Abstract Ocean climate impacts on survivorship and growth of Atlantic salmon are complex, but still poorly understood. Stock abundances have declined over the past three decades and 1992,2006 has seen widespread sea surface temperature (SST) warming of the NE Atlantic, including the foraging areas exploited by salmon of southern European origin. Salmon cease feeding on return migration, and here we express the final growth condition of year-classes of one-sea winter adults at, or just before, freshwater re-entry as the predicted weight at standard length. Two independent 14-year time series for a single river stock and for mixed, multiple stocks revealed almost identical temporal patterns in growth condition variation, and an overall trend decrease of 11,14% over the past decade. Growth condition has fallen as SST anomaly has risen, and for each year-class the midwinter (January) SST anomalies they experienced at sea correlated negatively with their final condition on migratory return during the subsequent summer months. Stored lipids are crucial for survival and for the prespawning provisioning of eggs in freshwater, and we show that under-weight individuals have disproportionately low reserves. The poorest condition fish (,30% under-weight) returned with lipid stores reduced by ,80%. This study concurs with previous analyses of other North Atlantic top consumers (e.g. somatic condition of tuna, reproductive failure of seabirds) showing evidence of major, recent climate-driven changes in the eastern North Atlantic pelagic ecosystem, and the likely importance of bottom-up control processes. Because salmon abundances presently remain at historical lows, fecundity of recent year-classes will have been increasingly compromised. Measures of year-class growth condition should therefore be incorporated in the analysis and setting of numerical spawning escapements for threatened stocks, and conservation limits should be revised upwards conservatively during periods of excessive ocean climate warming. [source] Modelling past and present geographical distribution of the marine gastropod Patella rustica as a tool for exploring responses to environmental changeGLOBAL CHANGE BIOLOGY, Issue 10 2007FERNANDO P. LIMA Abstract A climate envelope approach was used to model the distributions of the intertidal gastropod Patella rustica, to test the robustness of forecast responses to climate change. The model incorporated variables that were likely to determine the abundance and the northern range limit of this species in the NE Atlantic. The model was built using classification and regression tree analysis (CART) trained with historical distribution data from the mid 1950s and a set of corresponding climatic and oceanographic variables. Results indicated air and sea temperature, in particular during the reproductive and settlement periods, as the main determinants of the Atlantic distribution of P. rustica. The model was subsequently fed with contemporary climatic data and its output was compared with the current distribution and abundance of P. rustica, assessed during a 2002,2003 survey. The model correctly hindcasted the recent collapse of a distributional gap in northern Portugal, as well as an increase in abundance at locations within its range. The predicted northward expansion of the northern range limit did not occur because the absence of the species was confirmed in a survey encompassing the whole Atlantic French coast up to Brest. Stretches of unsuitable habitat too long to be overcome by dispersal are the likely mechanism controlling the northern limit of the distribution of this intertidal species. [source] Simulating spatially and physiologically structured populationsJOURNAL OF ANIMAL ECOLOGY, Issue 6 2001William S. C. Gurney Summary 1,Population dynamics are frequently the product of a subtle interplay between development and dispersal in an inhomogeneous environment. Simulations of spatially inhomogeneous populations with physiologically distinguishable individuals are a known source of numerical difficulty. 2,This paper reports a new and highly efficient algorithm for this problem, whose accuracy we demonstrate by comparison with conventional numerical solutions of one-dimensional problems. 3,As an illustration, we construct a two (space)-dimensional model of a copepod (Calanus finmarchicus) in the NE Atlantic, and demonstrate that its predictions correspond closely with those of an equivalent Lagrangian ensemble. [source] Maerl growth, carbonate production rates and accumulation rates in the ne atlanticAQUATIC CONSERVATION: MARINE AND FRESHWATER ECOSYSTEMS, Issue S1 2003Dan Bosence Abstract 1.Accumulations of maerl occur widely in ocean facing coastal waters (<20,30 m depth) of the northeast Atlantic, that are sheltered from the direct SW approach of storm waves and have little terrigenous sediment supply. 2.The different methods that have been used to assess the rate of formation of cool temperate, coralline algal gravels (maerl) are outlined. 3.Formation rates of maerl may be expressed as short-term, branch growth rates (mm yr,1), as calcium carbonate production rates (g CaCO3 m,2 yr,1), or as longer-term accumulation rates (m kyr,1=m 1000 yr,1). 4.Branch growth rates of the free living, branching coralline algae that form maerl in northwest Spain and western Ireland vary from 0.1 to 1.0 mm yr,1. Rates from Norway are either 0.05,0.15 or up to 1.0 mm yr,1. 5.Production rates vary from 30,250 g CaCO3 m,2 yr,1 in western Ireland, 876 g CaCO3 m,2 yr,1 in northwest France and 90,143 or 895,1423 g CaCO3 m,2 yr,1 in Norway. 6.Accumulation rates vary from 0.08 m ky,1 in Orkney to 0.5 m ky,1 in Cornwall, to 0.8,1.4 m kyr,1 in Norway. 7.These production and accumulation rates are similar to the lower end of such rates from tropical coral reef environments. This is achieved by high standing crops that compensate for the lower growth rates of the temperate algae. Although rapid on a geological time-scale these accumulation rates are far too low for the maerl to be regarded as a sustainable resource for extraction for agricultural and industrial use. Copyright © 2003 John Wiley & Sons, Ltd. [source] | ||||||||||