摘要:

Abstract.MediterraneanLeptomysisspecies are bentho‐nectonic shrimps living close to seagrass bed bottoms, forming swarms during the day and feeding on detritus and sedimentary organic matter during the night. As this matter is derived from different plant sources (phytoplankton, seagrasses, macro‐ and microalgae), assimilated carbon entering mysid tissues can hardly be identified on the basis of digestive tract analyses. Stable carbon isotope ratio measurements help to delineate food sources of the different studiedLeptomysisspecies because plants are distinct isotopically. These 6°C measurements reinforce the view of the minor role of seagrass carbon in benthic food webs and of the importance of algae in the dynamics of these ecosystems.SummaryFourLeptomysisspecies inhabit three relatively closely adjoining biotopes in the Gulf of Calvi:L. lingvuranear the surface, forming shoals within rock blocks,L. posidoniaeinPosidoniaseagrass beds, and the coupleL. heterophila +L. gracilisat the lower border of the infralittoral zone. These three biotopes are characterized by different main plant food sources (namely macroalgae, seagrasses, and phy‐toplankton), which are C isotopically well separated. δ13C measurements of the differentLeptomysispopulations show that these shrimps do not feed preferentially on the carbon source prevailing in their own biotope, but rather have an isotope ratio (‐16.5 to ‐20%0) close to the algal ratio. These observations can either be explained by feeding selectivity or by a differential assimilation rate of ingested material; in any case, they corroborate the role of algae in the trophodynamics of Mediterranean seagrass

ISSN:0173-9565    

DOI:10.1111/j.1439-0485.1995.tb00397.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

Abstract.Quantitative information on the vertical distribution of meiofaunal abundances and biomass were obtained from samples collected at 3 bathyal stations in the Eastern Mediterranean Sea located at the same depth but characterized by different food supply. Vertical distribution patterns of nieiofauna were investigated in relation to the biochemical composition of the sediment organic matter (proteins, carbohydrates, and lipids) and compared to benthic bacterial standing stocks. No significant relationship between bacteria and meiofauna was found, whereas a significant relationship between protein and lipid concentrations and total meiofauna density was observed. These data suggest that labile organic matter. considered as material readily aVdihbk to benthic consumers, may be an important factor regulating meiofaunal abundance and vertical distribution in deep‐sea sediment

ISSN:0173-9565    

DOI:10.1111/j.1439-0485.1995.tb00398.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

Abstract.Microplankton (silicoflagellates, dinoflagellates, tintinnids, pteropods, crustaceans, and fecal pellets) was analysed in 71 0–95 m samples from the Greenland Sea collected from May to June 1989. Abundances were clearly associated with the ice edge, highest concentrations occurring in ice‐free waters. The 15 to 30 m stratum was generally richer in microplankton than deeper waters, with the exception of microcrustaceans, which often peaked below 30 m. Six tintinnid species were identified. The mean size of the tintinnidParafavella denticulatafrom the Greenland Sea was consistently greater than that of Barents Sea specimens. It is suggested that colder waters and scarcer food are responsible for these morphometric differen

ISSN:0173-9565    

DOI:10.1111/j.1439-0485.1995.tb00399.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

Abstract.Seasonal variation of temperature effects on photosynthesis and respiration ofCymodorea nodosa(Ucria) Ascherson was investigated in a 1 m depth meadow in the Mar Menor lagoon (SE Spain). Light‐saturated net photosynthesis (Pmax)and dark respiration (R) rates were linearly correlated with water temperature between 10 and 30°C. and 10 and 35°C, respectively, during the year. Water temperature had a similar effect on R rates in August, November, and February, but increased Pmaxrates in August vs. those in February, thus promoting a shift of the maximum Pmax/R ratio values from 15°C in February to 30°C in August. P‐I curves had higher Pmaxvalues in May and August than in November or February, while Ic values remained relatively constant throughout the year. Whole‐plant carbon balances suggested thatC. nodosamight not be able to survive in the central basin of the lagoon and that the spatial distribution of this seagrass in the Mar Menor might be controlled by light ava

ISSN:0173-9565    

DOI:10.1111/j.1439-0485.1995.tb00400.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

Abstract.Submerged roots of red mangroves (Rhizophora mangle) in the Florida Keys were photographed at 1– or 2‐month intervals for 38 months to measure population dynamics of the epifaunal invertebrate species. Photographs were analysed for species composition and abundance and information on life spans, persistence, mortality, and seasonality. Larval recruitment to artificial surfaces was used to assess reproductive seasonality. As a measure of stability, populations were tested for narrow stochastic boundedness.In contrast to reports for a tropical mangrove root community, the Florida Keys root community showed enormous variability despite being dominated by long‐lived species with low, largely non‐seasonal recruitment. Species composition on individual roots changed dramatically on short time scales. Populations of the major species were not narrowly bounded on most roots and there was little evidence for a closely regulated community.Variability of this community related to the frequency and intensity of stochastic perturbations. Physical disturbance due to strong tidal Rows appeared to be the most important structuring process. Species‐specific predation and fragmentation of sponges were also important. These features contribute to the instability of the community by producing dramatic fluctuations in species abundances and preventing competitive processes from producing a more stable, equilibrium community. Temporal measurement scale was an additional important consideration in this habitat. Structuring processes occurred on very short time scales (1–2 months) and analysis on longer time scales gave inaccurate impressions of communi

ISSN:0173-9565    

DOI:10.1111/j.1439-0485.1995.tb00401.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

Abstract.Sponges on subtidal red‐mangrove prop roots may become exposed to air many times per year during very low tides. Full exposure is stressful and potentially fatal, particularly if occurring in full sun. Large root sponges show distinct species zonation between mean low water and ‐0.5 m.Haliclona implexiformisandLissodendoryx isodictyalis arenear the top whileScopalina ruetzleriare near the lower end of the range. Temporary experimental desiccation resulted in 100% recovery of all three species after they had been exposed to either sun or shade for up to 2 h.Scopalinais the least resistant and lost over 90% tissue within 3 days after the 4‐h and 6‐h experiments; the remaining cell mass succumbed to infestation by microbes.HaliclonaandLissodendoryxrecovered from as much as 6 h in full sun but lost 85% and 80% of the original tissue volume, respectively. InLissodendoryx, clusters of larvae developed in the regenerating fragments. Water loss tolerated by the three species is estimated as 66% of wet weight inHaliclona, 54% inLissodendoryxand 38% inScopalina. Salinity of interstitial seawater (pore water) extracted from exposed sponges rose from ambient 3.5% to 4.348% after 1 h, to 5.1–5.9% after 6 h. Most endobionts died or left their host during this last phase. Natural vertical zonation in these sponges reflects their resistance to tidal

ISSN:0173-9565    

DOI:10.1111/j.1439-0485.1995.tb00402.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

ISSN:0173-9565    

DOI:10.1111/j.1439-0485.1995.tb00403.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY