ALBERT

Description: Die Untersuchungen der Grundwasserbeschaffenheit und der hydrogeologischen Zusammenhänge erstrecken sich auf das nördliche Stadtgebiet von Berlin (West), das ein Teil des Einzugsgebietes der oberen Havel ist. Das betrachtete Grundwassersystem erfaßt die im Hangenden des mittel oligozänen Septarientons in normaler stratigraphischer Abfolge ausgebildeten Ablagerungen des Oberoligozäns, Miozäns und Pleistozäns Die Mächtigkeiten der auftretenden Schichtfolgen sind abhängig von einer durch Salzbewegungen verursachten Aufwölbung im NE und einer im W gelegenen Salz-Emigrationszone. Folglich treten die größten Mächtigkeiten (ca. 380 m) im W des Untersuchungsgebietes auf. Die pleistozänen Ablagerungen erreichen ihre größten Mächtigkeiten im Bereich einer Erosionsrinne, die im mittleren Teil des Untersuchungsgebietes bis in den Septarienton eingeschnitten ist. Die Betrachtung der Druck- und Fließverhältnisse zeigt sowohl für das tiefere, gespannte Grundwasser der tertiären Schichtfolgen als auch für den oberen Grundwasserleiter einen hauptsächlich nach SW gerichteten Grundwasserabstrom. Für die Potentialdifferenzen zwischen dem oberen und dem gespannten Grundwasser kann in den Bereichen großer Grundwasserentnahmen ein relatives Ansteigen der Druckfläche des tieferen Grundwassers erkannt werden. Die höhere Druckfläche des tieferen Grundwassers weist, in Abhängigkeit von der Durchlässigkeit der stauenden Schichten, auf ein Aufsteigen tieferer Grundwässer hin. Dies wird bekräftigt durch die Ergebnisse der geothermischen Untersuchungen, die für die entsprechenden Bereiche eine großflächige positive geothermische Anomalie erkennen lassen. Der Chemismus der untersuchten Grundwässer läßt im allgemeinen mit zunehmender Tiefe eine Abnahme der Gesamtmineralisation erkennen. Die durchschnittliche Gesamtmineralisation der tieferen Grundwässer liegt mit 15.07 mval/1 unter der des Grundwassers der pleistozänen Schichten (17.38 mval/1). Die räumliehe Betrachtung der Mineralisationsverteilung läßt für die tieferen Grundwässer im NE- und SE-Teil des Untersuchungsgebietes eine erhöhte Mineralisation erkennen, die hauptsächlich auf höhere Kalziumsulfatgehalte zurückzuführen ist. In westlicher Richtung kommt es, durch Reduktionsvorgänge, zu einer Abnahme der Mineralisation. Im tieferen Bereich der Rinne und in den oberoligozänen Schichtfolgen läßt sich das Auftreten von alkalihydrogenkarbonathaltigen Wässern erkennen, deren Entstehung auf Ionenaustauschvorgänge zurückzuführen ist. Die Spurenmetallgehalte zeigen im Grundwasser der tertiären Schichtfolgen, bedingt durch die auftretenden Gesteine, für die Elemente Aluminium, Kupfer und Zink deutlich höhere mittlere Gehalte. Die gegenüber dem Grundwasser der oberoligozänen Schichtfolgen höheren mittleren Bor-, Kupfer- und Nickelgehalte im Grundwasser der miozänen Schichten stehen in Verbindung mit der primären Anreicherung dieser Elemente in den organischen Ablagerungen des Miozäns. Für das Auftreten der Elemente Chrom (III), Strontium und Eisen lassen sich keine Unterschiede zwischen dem tiefen und dem oberflächennahen Grundwasserleiter erkennen.

Description: The quality of groundwater and hydrogeological relationships of the northern part of the town of Berlin (West), a catchment area of the upper part of the river Havel, were investigated. The observed groundwater System belongs to the stratas above the middle oligocene "Septarienton", in the normal sequence of upper oligocene, miocene and pleistocene. The thicknesses of the occuring layers are influenced by a salt dorne in the NE and a rim syncline in the W, caused by salt tectonics. Consequently the greatest thickness (~380m) is found in the Western part of the investigated area. The pleistocene deposits obtain their greatest thickness in the area of an erosion channel which is in the middle of the investigated area, incised into the middle oligocene Septarienton. The investigations of the relations between artesian head and groundwater flow of the deeper confi ned groundwater in the tertiary strata and of the upper aquifer proved a groundwater flow mainly in southwestern direction. The potential differences between the upper and the confined groundwater shows in the areas of ground-water lowering a relative rising of the hydrostatic pressure of the deeper groundwater. The higher artesian head of the deeper groundwater points to a rise of deeper groundwater, dependent on the permeability of the less permeable layers. This is confi rmed by the results of the geothermical investigations, which show a great positiv geothermal anomal y for these areas. The Chemical composition of the investigated groundwater shows a decreasing total mineral isation with increasing depth. The average total -mineral isation of the deeper groundwater of 15.07 mval/1 lies beneath the level of the groundwater of pleistocene layers (17.38 mval/1). Spacial observations of the mineral isation-distribution show a higher mineral isation for the deeper groundwater in the NE- and SE-part of the investigated area, which is mainly based on a higher calcium-sulfat-content. In the W a decrease of mineral isation, caused by reduction processes, can be observed. In the deeper part of the channel and in the upper oligocene layers an occurrence of alkali-hydrogencarbonat-water, caused by ion-exchange reactions, is recognizable. Trace-metalls contents in the groundwater of the tertiary layers have a definite higher average content of the elements Al, Cu and Zn, caused by the occuring Sediments. The concentration of B, Cu and Ni is higher in the groundwater of the miocene layers than in the groundwater of the upper oligocene layers, this is caused by the primary enrichment of these elements in the organic deposits of the miocene. There are no differences recognicable between the upper and the lower aquifers concerning the occurrence of the elements Co(III), Sr and Fe.

Description: Les recherches concernant la composition de l'eau souterraine et les relations hydro-geologiques Interessent la partie nord de la ville de Berlin (Ouest), qui fait partie de l'aire d'al imentation de la Havel superieure. Le Systeme de l'eau souterraine considere englobe les Sediments de l'oligocene superieur, du miocene et du pleistocene, surmontant strati graphiquement les couches de l'oligocene moyen (Septarienton). Les puissances des differentes series strati graphiques sont influencees par un bombement au Nord-Est, du ä une tectonique salifere, et par une zone d'emigration salifere situee a' l’ouest. En consfequence les puissances maximales (environ 380m) apparaissent dans la partie ouest du terrain analyse. Les formations du pleistocene atteignent leur plus grande epaisseur au niveau d'une gouttiere d'erosion pentue, encaissee dans la partie moyenne du terrain analyse jusqu'au Septarienton. L'observation des conditions de pression et d'ecoulement montre, tant pour l'eau souterraine profonde et captive des suites de couches tertiaires, tant pour les aquiferes superieurs, un ecoulement principalement vers le Sud-Ouest. Pour les differences de pression entre les eaux souterraines superieures et captives on note dans les terrains, desquels on preleve beaucoup d'eau, un soulevement relatif de la surface de pression de l'eau souterraine profonde. Le plus haut plan de pression de celle-ci indique donc que les eaux souterraines profondes montent en fonction de la permeabilite des couches accumulees. Ceci est renforce par les resultats des analyses geothermiques, qui montrent une anomal ie geothermique positive sur une grande surface des terrains en question. Les caracteri stiques hydrogeochimiques des eaux souterraines analysees font apparaTtre en general une diminution de la mineral isation totale en fonction de 1 ’augmentation de la profondeur. La mineral isation totale moyenne des eaux profondes souterraines est avec 15.07 mval/1 inferieure ä celle des eaux profondes des couches pleistocenes(17. 38 mval/1). La repartition horizontale de la mineral isation laisse apparaTtre pour les eaux profondes de la partie Nord-Est et Sud-Est du terrain analyse une mineral isation surelevee, qui est due principalement a une haute teneur en Sulfate de calcium. Vers 1 'ouest, la mineral isation diminue par l'effet de processus de rfeduction. Dans les terrains du fond de la gouttiere et dans les series de couches de l'oligocene superieur on remarque l'apparition d'eaux contenant du NaHCOp provenant du processus de changements des ions. Les teneurs de metaux traces dans les eaux souterraines des series tertiaires montrent nettement-conditionne par les roches y apparaissant- des valeurs moyennes elevees pour l’aluminium, le cuivre et le zinc. Les teneurs moyennes en bore, cuivre et nickel des eaux souterraines des couches du miocene, surelevees par rapport aux eaux souterraines des couches de l'oligocene superieur, sont en relation avec l'enrichissement primaire de ces elements dans les gisements organiques du miocene. En ce qui concerne la repartition des eie ments chrome( III), Strontium et fer aucune difference est notable entre les aquiferes profonds et ceux pres de la surface.

Description: thesis

Description: DFG, SUB Göttingen

Description: Phytoplankton (〉100 µm) abundance was studied in the open waters of the Gulf of Aqaba during the summer stratification period of 1996. A succession took place among the major phytoplankton groups, with diatom numbers decreasing throughout the summer. The diazotrophic cyanobacteria Trichodesmium spp. became more prominent as the stratification period progressed; 5 Trichodesmium species were identified: T. thiebautii, T. erythraeum with tuft-shaped colonies and Trichodesmium sp. with puff-shaped colonies were common at ~102 colonies m-3 throughout the stratification period, whereas T. tenue and T. hildebrandtii were more rare. A bloom of T. thiebautii and T. erythraeum with 〉106 tuft colonies m-3 was observed in coastal waters of the Gulf during fall 1997. Tuft-shaped colonies were dominant near the surface, while puff-shaped colonies of Trichodesmium sp. were mainly found in the bottom half of the photic zone. These depth distributions were maintained for more than 2 mo, suggesting that the 2 colony types occupied distinct niches. Puff-shaped colonies were found to have higher chlorophyll a contents than tufts, but their photosynthetic activities were not significantly different. Fatty acid analysis of dominant plankton species yielded new trophic relationships for Trichodesmium spp. The Trichodesmium spp.-specific fatty acid C22:2 ω6 was found in Macrosetella gracilis (the sole copepod to graze on Trichodesmium spp.) and in chaetognaths, suggesting that these carnivorous zooplankton fed on M. gracilis. Furthermore, this fatty acid was observed in the filter-feeding Salpa maxima, which was abundantly present in the Gulf of Aqaba during June 1997.

Description: The combined and interactive effects of climatic and ecological factors are rarely considered in marine communities. We designed a factorial field experiment to analyze (1) the interactive effects of ambient UV radiation and consumers; and (2) the effects of photosynthetically active radiation (PAR 400 to 700 nm), UVA (320 to 400 nm) and UVB (280 to 320 nm) radiation on a marine hard-bottom community in Nova Scotia, NW Atlantic. Species recruitment and succession on ceramic tiles were followed for 5 mo. We found strong negative UV effects on biomass and cover of the early colonizing macroalga Pilayella littoralis, whereas UVB was more harmful than UVA radiation. Consumers, mainly gammarid amphipods, increased P. littoralis biomass when UV was excluded, probably through fertilization. These initially strong and interacting UV and consumer effects on total biomass and cover diminished as species succession progressed. Species diversity was not affected by experimental treatments, but significant shifts in species composition occurred, especially at the recruitment stage. Red algae were most inhibited by UV, whereas sedentary invertebrates and some brown algae tended to increase under UV exposure. Consumers suppressed green and filamentous brown algae, but favored the other groups. Again, these effects diminished during the later stages of succession. We conclude that UV radiation can be a significant structuring force in early successional benthic communities, and that consumers can mediate its effects.

Description: The effect of methane released from decomposing surficial gas hydrates (SGH) on standing stocks and activities of the small-sized benthic biota (SSBB; i.e. bacteria, fungi, protozoa, and meiobenthic organisms) was studied at about 790 m water depth, at the Hydrate Ridge, Cascadia subduction zone. Presence of SGH and elevated sulfide concentrations in the sediment were indicated by extensive bacterial mats of Beggiatoa sp. and clam fields of the bivalve mollusc Calyptogena sp. Vertical and horizontal distribution patterns of the SSBB biomass were derived from DNA and total adenylate (TA) sediment assays. Potential bacterial exoenzymatic hydrolytic activity was measured using fluorescein-di-acetate (FDA) as substrate. Estimates of chemoautotrophic production of particulate organic carbon (POC.) were determined by 14CO2 uptake incubations. Inventories of chl a and pheopigments were determined as parameters of surface water primary produced POC input. Average SSBB biomass in clam field sediments integrated over the upper 10 cm (765.2 gC m-2, SD 190.1) was 3.6 times higher than in the adjacent control sites (213 gC m-2, SD 125). Average SSBB biomass in bacterial mat sediments, which were almost devoid of eukaryotic organisms 〉 31 µm, was 209 gC m-2 (SD 65). Significant correlations between FDA, DNA and plant pigments imply that productivity of the SSBB at SGH sites is only partially uncoupled from the primary production of the surface water. Areal estimates of autotrophic Corg production at control sites, bacterial mat sites and in clam field sites were 5.7, 59.7 and 190.0 mgC m-2 d-1, respectively. Based on different models predicting vertical POC fluxes from surface water primary production and water depth, these autotrophic POC productions account for 5 to 17% (controls), 35 to 68% (bacterial mats), and 63 to 87% (clam fields) of the bulk POC (sum of allochthonous POC input through the water column and sedimentary autochthonous autotrophic POC production) provided at the various sites. At SGH sites inventories of chl a and pheopigments, integrated over the upper 10 cm of the sediment, were half of that found at the control sites. This might be due to enhanced degradation of phytodetritally associated organic matter. The resulting low molecular weight organic carbon compounds might stimulate and fuel sulfate reduction, which is conducted in a microbial consortium with anaerobic methane consuming archaea. This syntrophic consortium might represent a prominent interface between gas hydrate derived carbon and allochthonous Corg flow. We infer that degradation kinetics of SGH is affected by, e.g., seasonally varying input of allochthonous organic matter.

Description: The sediment beneath and at various distances from the fish farm cages in Cephalonia bay (Eastern Mediterranean) was investigated seasonally through sediment profiling imagery (SPI) as well as through monitoring of geochemical variables and macrofaunal assemblages. The SPI images (SPI) repeatedly showed the same qualitative pattern along the benthic enrichment gradient with readily identifiable attributes such as depth of dark sediment, signs of outgassing and bioturbation marks. Quantitative comparisons showed that a large number of SPI attributes showed significant positive or negative correlation with geochemical and biological attributes describing the effect of fish farming on the seabed. All multivariate patterns obtained through the analysis of SPI attributes were highly correlated to those obtained from standard multivariate analysis of macrofauna during the respective seasons. It is argued that SPI provides an integrated assessment of the sedimentary conditions and therefore may be used as a complement of or even a substitute for standard sampling methods when mapping the effects of aquaculture on silty substrates

Description: Sediment incubation microcosms, multitrap apparatus and water column variables have been employed to describe the dynamic changes in benthic-pelagic coupling between nutrient pools in the Pontevedra ria, NW Spain, during spring and summer 1998. A comparison of the chemical characteristics of suspended and bed sediment together with sediment nutrient effluxes revealed that particulate organic nitrogen and carbon were progressively depleted upon transit through the nutrient pools. The main fate of particulate organic nitrogen reaching the bed sediment is denitrification, although resuspension is also important. An estimate of net denitrification (Dnet) was made at 2 muddy sites in the ria with a mass balance at the benthic boundary layer. First-order approximations calculate Dnet to be 178 and 182 µmolN m-2 h-1 at the 2 stations, and agree well with previous modelling estimates. Denitrification is highest when upwelling relaxes and the flux of organic matter to the sediment increases. Regular inputs of offshore water ensure water renewal and re-oxygenation of bottom waters, thus preventing anoxia, particularly in the summer. With upwelling, large quantities of ammonium are effluxed to the water column (250 µmolNH4+ m-2 h-1), probably as a result of the bed sediment resuspension engendered by upwelling and stirring of phytodetrital fluff held in suspension as neutrally buoyant material above the sediment surface. We hypothesise that hydrodynamical processes play an important role in determining the quantity of nutrients remineralised in the Pontevedra ria and, in the case of nitrogen, the rate of denitrification at the benthic boundary layer.

Description: Gas hydrates occur at the sediment surface on the southern summit of Hydrate Ridge, Cascadia convergent margin. The hydrates are found in mounds several meters in diameter and up to 2 m high, and are covered by sediment and mats of the filamentous sulfur-oxidizing bacteria Beggiatoa. The mounds are surrounded by vesicomyid clams (Calyptogena pacifica, C. kilmeri), which in turn are encircled by solemyid bivalves (Acharax sp.). The zonation pattern of 3 species (Calyptogena spp. and Acharax sp., which harbor chemoautotrophic bacteria in their gills, and the chemoautotrophic Beggiatoa), is also reflected in a change in the entire community structure. Beggiatoa, Calyptogena spp. and Acharax sp. are shown to be characteristic species for the different communities. The Beggiatoa community directly overlaying the gas hydrates consists of seep endemic species in high densities: gastropods (Provanna laevis, P. lomana, Pyropelta corymba, Hyalogyrina sp. nov.), bivalves (Nuculana sp. nov.) and polychaetes (Ampharetidae, Polynoidae, Dorvilleidae). Based on pooled samples, the rarefaction curves show a decrease in species diversity in the Beggiatoa and Calyptogena communities. The hydrogen sulfide gradients in the porewater of sediments below the different communities dominated by either Beggiatoa, Calyptogena spp. or Acharax sp. vary by 3 orders of magnitude. The diffusive sulfide flux based on the measured sulfide concentration gradients is highest in Beggiatoa sp. communities (23 ± 13 mol m-2 yr-1), slightly less in Calyptogena communities (6.6 ± 2.4 mol m-2 yr-1), and low in Acharax communities (0.05 ± 0.05 mol m-2 yr-1). The difference in the sulfide environment is a factor influencing the distribution patterns of the chemoautotrophy-dependant and heterotrophic species at the deep-sea sediments containing gas hydrate.

Description: A colony of Humboldt penguins Spheniscus humboldti in central Chile was monitored from August 1995 to July 2000 to determine patterns of breeding and colony attendance and how these were affected by climatic (rainfall) and oceanographic (El Niño) factors. Nests were periodically checked for contents and roosting birds were counted from vantage points. Two main breeding events were observed: between August and January (spring event) and between April and June (autumn event). Whereas the spring event regularly produced offspring, the autumn event was systematically affected by rains, causing considerable nest desertion. Adults were present in the colony from August to May, abandoning the colony during winter after the nests were flooded. Juveniles occurred only between November and March. Adults moulted mainly in February, while juveniles moulted in January. During the 1997/98 El Niño episode, the number of breeding pairs was 55 to 85% lower than the mean, the onset of nesting was delayed, and abnormally heavy rainfall flooded nests. While the number of breeding pairs was significantly related to sea surface temperature anomalies (SSTA), breeding success was not. The attendance of adults and juveniles at the colony during El Niño was 25 and 73% lower, respectively, than the mean attendance. This 2-peak breeding strategy of Humboldt penguins appears to have evolved in response to the more favourable oceanographic and climatic conditions of Perú, where breeding is continuous and not interrupted by rains. Although less productive, the species probably maintains its autumnal breeding in central Chile because this provides additional offspring to supplement those regularly produced during the spring event.

Description: Zooplankton grazing on bacterio- and phytoplankton was studied in the Gulf of Aqaba and the Northern Red Sea during Meteor Cruise Me 44-2 in February-March 1999. Protozoan grazing on bacterioplankton and autotrophic ultraplankton was studied by the Landry dilution method. Microzooplankton grazing on phytoplankton 〉6 µm was studied by incubation experiments in the presence and absence of microzooplankton. Mesozooplankton grazing was studied by measuring per capita clearance rates of individual zooplankton with radioactively labelled food organisms and estimating in situ rates from abundance values. Protozoan grazing rates on heterotrophic bacteria and on algae 〈6 µm were high (bacteria: 0.7 to 1.1 d-1, ultraphytoplankton: 0.7 to 1.3 d-1), while grazing rates on Synechococcus spp. were surprisingly low and undetectable in some experiments. Mesozooplankton grazing was weak, cumulative grazing rates being ca. 2 orders of magnitude smaller than the grazing rates by protozoans. Among mesozooplankton, appendicularians specialised on smaller food items and calanoid copepods on larger ones.

Description: Two new isomalabaricane triterpenes, stellettin H (1) and stellettin I (2), have been isolated from the marine sponge Rhabdastrella globostellata, collected from the Philippines. Stellettins A−D (3−6), (−)-stellettin E (7), and rhabdastrellic acid-A (8) were also isolated and characterized. Stellettin B (4) and (−)-stellettin E (7) showed selective cytotoxicity toward p21WAF1/Cip1-deficient human colon tumor (HCT-116) cells with IC50 values of 0.043 and 0.039 μM, respectively.

Description: Raf/MEK-1/MAPK cascade inhibitor activity-directed fractionation of the sponge Stylissa massa afforded eight known alkaloids:  aldisine (1), 2-bromoaldisine (2), 10Z-debromohymenialdisine (3), 10E-hymenialdisine (4), 10Z-hymenialdisine (5), hymenin (6), oroidin (7), and 4,5-dibromopyrrole-2-carbonamide (8). Both 4 and 5 showed significant enzyme inhibitory activity (IC50 3 and 6 nM, respectively). Secondary assays identified these compounds as potent MEK-1 inhibitors. Compounds 4 and 5 also inhibited the growth of human tumor LoVo cells.

Description: The increasing environmental pressures on estuarine and coastal waters call for improved monitoring techniques of chemical constituents to aid management decisions. Automated stripping voltammetry is a suitable technique for continuous, near real-time monitoring of trace metals in marine systems. This contribution describes the application of voltammetric monitoring techniques in estuarine and coastal waters of the UK and Spain. The high spatial and temporal resolution of the data obtained, allows a thorough interpretation of the trace metal sources and behaviour. Future trends in this field research include submersible sensors which can be remotely deployed for a period of several weeks.

Description: Factors responsible for aggregations of jumbo flying squid Dosidicus gigas, an important component of the marine food web and target of commercial fisheries off the Costa Rica Dome in the Eastern Tropical Pacific Ocean (ETP), were examined during 2 years of different extreme oceanographic conditions: fall 1997 El Niño and fall 1999 La Niña. A high abundance of squid occurred in association with the well-developed countercurrent ridge (upwelling) off the Costa Rica Dome during fall 1997, but not during fall 1999, when the countercurrent ridge was less developed. Two features of the well-developed countercurrent ridge were considered important for the occurrence of high jumbo flying squid concentrations. Firstly, subsurface chlorophyll a (chl a) maxima were formed along the countercurrent ridge, resulting in integrated chl a concentrations in the upper 100 m being relatively high considering the generally low productivity of the ETP during an El Niño event. Secondly, a strong salinity front formed along the North Equatorial Countercurrent, which is possibly responsible for retention of jumbo flying squid in the ridge. Large yellowfin tuna Thunnus albacares, which mainly feed on micronekton (small fishes, cephalopods and swimming crabs), as do jumbo flying squid, were also more highly concentrated along the countercurrent ridge during 1997 than during 1999. It was noted that skipjack tuna Katsuwonus pelamis and small yellowfin tuna, which mainly feed on zooplankton, were associated with the equatorial ridge in the ETP, indicating that prey faunal components may also play an important part in the close association of jumbo flying squid with the countercurrent ridge.

Description: We examined how seabirds might be used to study marine environmental variables, which necessitates knowing location and the value of the variable to be studied. Five systems can potentially be used for determination of location: VHF (Very High Frequency) telemetry, PTT (Platform Terminal Transmitters) telemetry, GLS (Global Location Service) geolocation methods, dead reckoning and GPS (Global Positioning System), each with its own advantages with respect to accuracy, potential number of fixes and size. Temperature and light were used to illustrate potential difficulties in recording environmental variables. Systems currently used on seabirds for measurement of temperature respond slowly to environmental changes; thus, they may not measure sea surface temperature adequately when contact periods with water bodies are too short. Light can be easily measured for light extinction studies, but sensor orientation plays a large role in determining recorded values. Both problems can be corrected. The foraging behaviour of seabirds was also examined in order to identify those features which would be useful for determination of marine environmental variables at a variety of spatial and temporal scales. Area coverage by birds is highly dependent on breeding phase and tends to be concentrated in areas where prey acquisition is particularly enhanced. The identification of these sites may be of particular interest to marine biologists. 'Plungers' and 'divers' are potentially most useful for assessment of variables deeper within the water column, with some divers spending up to 90% of their time sub-surface. Few seabirds exploit the water column deeper than 20 m, although some divers regularly exceed 50 m (primarily penguins and auks), while 2 species dive in excess of 300 m. The wide-ranging behaviour of seabirds coupled, in many instances, with their substantial body size makes them potentially excellent carriers of sophisticated environmental measuring technology; however, the ethical question of how much the well-being of birds can, and should, be compromised by such an approach needs to be carefully considered.

Description: We report how different zooplankton groups (doliolids, cladocerans and copepods) are able to influence the coastal pelagic food web, including the microbial food web, in waters of the NW Mediterranean. We studied the effect of grazing and of grazing-induced nutrient recycling mediated by different types of zooplankton grazing on a natural phytoplankton community. Experiments were conducted in semicontinuous 2-stage chemostats. The 1st stage vessels contained seawater from Blanes Bay, Spain (NW Mediterranean) including its natural phytoplankton community; the 2nd stage vessels contained the same seawater and copepods, cladocerans or doliolids. At daily intervals we transferred part of the medium from the 2nd to the 1st stage flasks, which contained ungrazed algae and excreted nutrients. In this way, the zooplankton could influence phytoplankton dynamics both by selective grazing and by differential excretion of limiting nutrients. In the 2nd stage flasks grazing changed the algal community composition. Doliolids and cladocerans promoted the growth of large algae and copepods shifted the size spectrum towards small sizes. This effect was transferred to the 1st stage flasks. Doliolids, cladocerans and copepods also affected the microbial food web in different ways. Size-selective grazing led to differences in the nanoplankton concentrations. These in turn affected bacterial concentrations in a trophic cascade. The potential to modify a given algal population increased with increasing selectivity of the grazer.

Description: Both surface texture and littorinid grazing are known to influence the establishment of many shallow-water benthic hard-bottom communities. However, the effects of these factors and their interactions have not yet been investigated in a quantifiable manner. This investigation aims to assess the interactive effect of both factors in a strictly standardized manner. Natural recruitment by diatoms, the barnacle Balanus improvisus and the tube-building polychaete Polydora sp. was monitored under a 2-factorial treatment: grazing by the periwinkle Littorina littorea (Factor 1; 2 levels: I or no snails per plate) on artificial recruitment plates of different initial surface rugosities (Factor 2; 5 levels: smooth, 0.1, 0.5, 1 and 5 mm rugosity elements), In the absence of grazers, barnacle recruitment decreased with increasing initial rugosity, polychaete recruitment peaked at intermediate rugosities, and diatoms exhibited contrasting recruitment patterns in an in vitro and an in situ experiment. When preferred recruitment sites coincided for Polydora and B. improvisus, a competition for space could be inferred from a negative correlation between the 2 species. However, when the overlap of requirements weakened on the 5 rugosities, the relationship was positive, but was not statistically significant. Grazing efficiency by L. littorea depended on initial rugosity, generally showing minimum values on intermediate rugosities which is attributable to a mismatch between radula dimensions and surface structures in these rugosity classes. Additionally, grazing effects tended to increase with higher prey densities. As all factors-initial rugosity, grazing, colonizer species-interact with each other, the outcome of recruitment under combined factors is difficult to predict from single factor effects.