摘要:

Abstract.Postlarvae and competent larvae of five species of echinoids (Genoadaris metadata, Arbticia lixula, Puracentrolus lividus, Echinocyamus pusillus, andEdiinocardiurn cordulum) were found in vertical hauls taken in the upper layer of the water column (30‐0 m). Competence of larvae was associated with both the extrusion of the adult rudiment and the retraction of the epidermis of the arms. Postlarvae ofA. lixidawere found offshore in areas where the sea floor is at a depth of more than 2(K)C.m. The occurrence of postlarvae far from their settlement grounds questions the necessity of a suitable benthic substrate to induce metamorphosis. Hypotheses dealing with the possibility of undergoing metamorphosis in midwater are discussed.RésuméDes larves compétentes et des post‐larves de trois échinides réguliers:Arbacia lixula, Genocidaris maculata, Paracentrotus lividuset du clypéastréideEchinocyamus pusillusont été trouvées dans des pêches verticales effectueés dans des couchesd'eaux superficielles (30‐0 m). Les larves compétentes montrent les caractéristiques consideréés comme des phénomènes irréversibles de la métamorphose: évagination du rediment et rétraction de 'épiderme des bras larvaires. Des post‐larves de 'oursinA. lixulaont été récoltées dans des pêches pratiquées loin de la côte au‐dessus de fonds de plus de 2000m. La présence de ces post‐larves loin des sites de recrutement des juvéniles pose le problème de la necessité du choix d'un substrat benthique pour que les évènements qui caractérisent la métamorphose puissent être induits. Ce problème et les hypothèses sur la p

ISSN:0173-9565    

DOI:10.1111/j.1439-0485.1988.tb00201.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Abstract.An intertidal mud sediment in the Kerguelen Archipelago was sampled weekly from January 1982 to March 1983. Measurements were taken for organic matter (carbon and nitrogen) and biological (bacteria, microphytobenthos, and mciofauna) parameters. The sediment is rich in organic matter, with a mean organic carbon content of 130gC‐ m‐2. Benthic living components yield low mean biomasscs in relation to the total organic pool. Besides some marine inputs, the main allochthonous source was identified as terrestrial inputs. Benthic activities seemed strongly governed by food availability and not by temperature. Obvious seasonal changes in bacterial abundances (direct counts), primary production, and mciofauna distributions were observed. Photosynthctic production reached high values (up to 2275 mg C‐m‐2‐d‐1), reflecting the presence of a dense microphytobenthos. Preliminary energy budgets for two seasons (spring and winter) have been constructed. In both periods, the measured primary production can support the high mciofauna

ISSN:0173-9565    

DOI:10.1111/j.1439-0485.1988.tb00202.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Abstract.Shoot density was lower, while leaf area index and above‐ to below‐ground biomass ratios were higher forThalassia testudinumcollected from the deep edge when compared to the shallow edge of a meadow off Anclotc Key, Florida. These three characters followed patterns predicted from previous studies. The characters were reversed in order for plants from shallow and deep edges of a meadow off Egmont Key, about 50 km south of Anclote Key. Causes other than light were not evident to explain this reversal in the Egmont Key meadow. This study suggests that although light limitation may be the usual limiting factor for depth distribution in seagrass meadows, other factors cannot be ignored in many meadows along the west coast of Flor

ISSN:0173-9565    

DOI:10.1111/j.1439-0485.1988.tb00203.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Abstract.Four sites were sampled in kelp(Macrocysiis pyrifera)forests occupying rocky bottom habitats along a wave exposure gradient in central California. Consistent betwecn‐site differences were found in the three major structural elements ‐ the surface canopy, the undcrstory assemblage, and the ground cover/turf assemblage ‐ of kelp forest communities.Macrocysiis pyriferawas found at all four sites.Nereucyslis tuelkeanaonly at the most exposed site. The understory kelpsLaminaria setchelliiandPterygopltora californicawere also characteristic of exposed sites. Articulated coralline algae were more abundant at exposed sites than protected, while fleshy red algae showed the opposite pattern. All four study sites were located along 8.5 km of coastline, and thus were assumed to have available to them the same species pool for colonization. The substrate composition was the same and the amount of unconsolidated substrate was similar at all four sites. We suggest that exposure to wave‐generated water motion, through its influence on the surface canopy and therefore on the amount of light reaching the bottom, is responsible for these between‐site di

ISSN:0173-9565    

DOI:10.1111/j.1439-0485.1988.tb00204.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Abstract.In order to simulate SPOT‐typc satellite imagery, remote sensing of the Bay of San Cyprianu (Corsica) was carried out using a radiation sensor mounted in an aircraft. The resulting simulated image was calibrated using a chart of the benthos produced by SCUBA diving. We show that remote sensing by satellite should be able to resolve certain bottom types and benthic communities in water down to a depth of 12

ISSN:0173-9565    

DOI:10.1111/j.1439-0485.1988.tb00205.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Abstract.Seasonal changes in nitrogen, free amino acids, and carbon were investigated in the three Mediterranean seagrassesPosidonia oceanica, Cymodocea nodosa, andZostera noltii.Leaves, rhizomes, roots, as well as dead plant material were analysed separately. Highest N‐concentrations were obtained in the winter months, regardless of species or plant part. In contrast to the other two species, the N‐content inPosidoniawas higher in the rhizomes than in the leaves.In the investigated species, marked differences in the free amino acid (FAA) composition were detected between species: Proline, lacking inPosidonia, was the main component inCymodocea.InPosidonia, FAA decreased from 320umol g‐1(dry wt) in leaf sheaths to 1.5 umol g‐1(dry wt) in the leaf tips. The function of proline as a possible storage and/or stress metabolite is discussed.High C/N values in deadP. oceanicaandC. nodosarhizomes as well as inP. oceanicawrack seem to be related to considerable resistance to decomposition. Low C/N ratios did not increase in detachedC. nodosaandZ. noltiileaves, which began to decompose shortly after detachment from the

ISSN:0173-9565    

DOI:10.1111/j.1439-0485.1988.tb00206.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

ISSN:0173-9565    

DOI:10.1111/j.1439-0485.1988.tb00207.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY