603 resultados para Isopoda.
Resumo:
Early summer in the Arctic with extensive ice melt and break-up represents a dramatic change for sympagic-pelagic fauna below seasonal sea ice. As part of the International Polar Year-Circumpolar Flaw Lead system study (IPY-CFL), this investigation quantified zooplankton in the meltwater layer below landfast ice and remaining ice fauna below melting ice during June (2008) in Franklin Bay and Darnley Bay, Amundsen Gulf, Canada. The ice was in a state of advanced melt, with fully developed melt ponds. Intense melting resulted in a 0.3- to 0.5-m-thick meltwater layer below the ice, with a strong halocline to the Arctic water below. Zooplankton under the ice, in and below the meltwater layer, was sampled by SCUBA divers. Dense concentrations (max. 1,400 ind./m**3) of Calanus glacialis were associated with the meltwater layer, with dominant copepodid stages CIV and CV and high abundance of nauplii. Less abundant species included Pseudocalanus spp., Oithona similis and C. hyperboreus. The copepods were likely feeding on phytoplankton (0.5-2.3 mg Chl-a/m**3) in the meltwater layer. Ice amphipods were present at low abundance (<10 ind./m**2) and wet biomass (<0.2 g/m**2). Onisimus glacialis and Apherusa glacialis made up 64 and 51% of the total ice faunal abundance in Darnley Bay and Franklin Bay, respectively. During early summer, the autochthonous ice fauna becomes gradually replaced by allochthonous zooplankton, with an abundance boom near the meltwater layer. The ice amphipod bust occurs during late stages of melting and break-up, when their sympagic habitat is diminished then lost.
Resumo:
Seamounts are of great interest to science, industry and conservation because of their potential role as 'stirring rods' of the oceans, their enhanced productivity, their high local biodiversity, and the growing exploitation of their natural resources. This is accompanied by rising concern about the threats to seamount ecosystems, e.g. through over-fishing and the impact of trawling. OASIS described the functioning characteristics of seamount ecosystems. OASIS' integrated hydrographic, biogeochemical and biological information. Based on two case studies. The scientific results, condensed in conceptual and mass balanced ecosystem models, were applied to outline a model management plan as well as site-specific management plans for the seamounts investigated. OASIS addressed five main objectives: Objective 1: To identify and describe the physical forcing mechanisms effecting seamount systems Objective 2: To assess the origin, quality and dynamics of particulate organic material within the water column and surface sediment at seamounts. Objective 3: To describe aspects of the biodiversity and the ecology of seamount biota, to assess their dynamics and the maintenance of their production. Objective 4: Modelling the trophic ecology of seamount ecosystems. Objective 5: Application of scientific knowledge to practical conservation.
Resumo:
Structure of assemblages associated with mussel aggregations of Bathymodiolus azoricus was investigated. Mussel beds were found on hydrothermal vent fields on the Mid-Atlantic Ridge (Menez Gwen, Lucky Strike, and Rainbow) at depths 850-2400 m. The community structure of the mussel bed assemblages varied between studied areas. Large number of species was unique to mussel beds of the Menez Gwen field; the most observed taxa were not specialized hydrothermal species. All other nonunique species were found within the Lucky Strike region. The lowest mussel assemblage structure evenness was observed in the shallowest Menez Gwen area (850 m depth). We assume that two types of mussel assemblages (nematode-dominated and copepod-dominated) exist within the Lucky Strike field. The assemblages of B. azoricus differ significantly from assemblages of B. thermophilus inhabiting Pacific hydrothermal vents.
