摘要:

AbstractPlots of intermediate‐height cordgrass (Spartina alterniflora) were fertilized with nitrogen, misted with freshwater, given both misting and N, or left untreated. Bacterial responses on standing‐decaying leaf blades were measured as changes in epiphytic mass, rates of shedding of bacterial cells into seawater, and rates of net growth on blades. Epiphytic mass rose with time, and it did so 6‐fold more sharply for the combination of fertilization and misting than for control. Since the sediment surface would offer higher N and water availability, this may indicate that movement of leaf material to marsh sediments would strongly favor bacterial activity. Net growth on aerially incubated (15 h), wet blades as percentage of standing bacterial mass was unchanging with duration of decay period, but was affected by treatment (about 0 to +5% h−1for misted treatments, +15% h−1for unmisted treatments). Faster growth on newly wetted, unmisted blades may have been due to release of cells from growth limitation by desiccation. Plot treatment did not affect specific rate of bacterial shedding (about 8% of standing bacterial epiphytic mass during one h of submergence at 4 weeks, and 149% h−1at 12 weeks). It may be that during high spring tides, bacterial shedding from standing‐decaying blades could provide numbers of new cells in the water column near to or greater than those provided by division of bacteriopla

ISSN:1434-2944    

DOI:10.1002/iroh.19980830202

出版商:WILEY‐VCH Verlag    

年代:1998

数据来源: WILEY

摘要:

AbstractThe hydropsychids of two Mediterranean river basins in southern Spain (Guadaira and Guadalete) were investigated from January 1988 to January 1989. The distribution of hydropsychids along an environmental gradient related to altitude varied depending on species. Two distinct species assemblages were observed. one located in the lower altitude sites (the “downstream assemblage” comprisingHydropsyche pictetorum, Hydropsyche exocellataandCheumatopsyche lepida) and the other in the upper‐most areas (the “upstream assemblage” comprisingHydropsyche punica, Hydropsyche infernalis, Hydropsyche instabilis), which displayed a statistically significant preference for this type of habitat. Finally,H. pictetorum, selected the lowest sites. From a temporal point of view most species displayed a high variability in density dynamics between sites, suggesting a strong plasticity in life‐cycl

ISSN:1434-2944    

DOI:10.1002/iroh.19980830203

出版商:WILEY‐VCH Verlag    

年代:1998

数据来源: WILEY

摘要:

AbstractA method based on artificial substrata is proposed to study hyporheic biofilm development as well as the procedure to remove bacteria from these biofilms. The device is a perforated pipe in which glass slides are introduced vertically. Attached bacteria are removed by sonication for 180 seconds at power 2 (arbitrary unit); longer sonication time or higher power can cause cell destruction. A bacterial colonization experiment was performed in an upwelling zone of a riffle in the Rhǒne River. Total bacterial abundances reached a steady‐state after 5 days of colonization, and the percentage of ETS‐active bacteria was maximal after 3 days of incubation in the bed sediments. These results validate this device as usable to monitor biofilm development in natural systems, making this method as a promising tool to characterize the trophic status of a stream using integrative biological descrip

ISSN:1434-2944    

DOI:10.1002/iroh.19980830204

出版商:WILEY‐VCH Verlag    

年代:1998

数据来源: WILEY

ISSN:1434-2944    

DOI:10.1002/iroh.19980830205

出版商:WILEY‐VCH Verlag    

年代:1998

数据来源: WILEY

摘要:

AbstractThe composition and distribution of the macrobenthic polychaete fauna in the Evros Delta (North Aegean Sea) have been investigated by means of 4 replicate quantitative samples collected at 35 sites. 10 species were found and, in additional qualitative samples, the sedentary speciesFicopomatus enigmaticuswas collected. On the basis of the similarity in distribution among stations, 3 groups of species have been distinguished. One of these groups includes the speciesSpio decoratusandHediste diversicolorwhich were both dominant and present at almost all stations. The distribution of species in the study area seems to depend on factors such as salinity, granulometric composition and organic matter of the sediment and interspecific competition, but mainly on the degree of “confinement”, namely the degree of exchange with the open sea. At the most isolated stations, the lowest number of species and the highest values of abundance and biomass were recor

ISSN:1434-2944    

DOI:10.1002/iroh.19980830206

出版商:WILEY‐VCH Verlag    

年代:1998

数据来源: WILEY

摘要:

AbstractSeasonal changes in the species composition, abundance and biomass of planktonic ciliates were determined every 2–3 weeks at two sites of 30 m depth and one location of 105 m depth in the southwestern Gdańsk Basin between January 1987 and January 1988. A total of 40 ciliate taxa were observed during this period. AutotrophicMesodinium rubrumdominated ciliate abundance and biomass: maximal values of 50 · 10−1ind.1‐1and 65 μg C 1−1were recorded. The annual mean biomass ofM. rubrumcomprised 6 to 9% of the annual mean phytoplankton biomass. The highest abundances and biomasses of heterotrophic ciliates were noted at all stations in the spring and summer in the euphotic zone with maximum values of 28 · 103ind. 1−1and 23 μg C 1−1. Three ciliates assemblages were distinguished in the epipelagic layer: large and medium‐size non‐predatory ciliates, achieving peak abundance in spring and autumn; small‐size microphagous ciliates and epibiotic ciliates which were abundant in summer, and large‐size predacious ciliates dominating in spring. Below 60 m, a separate deep‐water ciliate community composed ofProrodon‐like ciliates andMetacystisspp. was found. The ciliate biomass in the 60–105 m layer was similar to the ciliate biomass in the euphotic zone. The heterotrophic ciliate community contributed 10 to 13% to the annual mean zooplankton biomass. The potential annual production ofM. rubrumcomprised 6 to 9% of the total primary production. Carbon demand of non‐predatory ciliates, calculated on the basis of their potential production, was estimated to be equivalent to 12–1

ISSN:1434-2944    

DOI:10.1002/iroh.19980830207

出版商:WILEY‐VCH Verlag    

年代:1998

数据来源: WILEY

ISSN:1434-2944    

DOI:10.1002/iroh.19980830201

出版商:WILEY‐VCH Verlag    

年代:1998

数据来源: WILEY