The role of phytoplankton in determining the underwater light climate in Lake Constance

At all seasons, the underwater light field of meso-eutrophic large (480 km²) deep (mean: 100 m) Lake Constance was studied in conjunction with the assessments of vertical distributions of phytoplankton chlorophyll concentrations. Vertical profiles of scalar, downwelling and upwelling fluxes of photosynthetically available radiation, as well as fluxes of spectral irradiance between 400 and 700 nm wavelength were measured.The overall transparency of the water for PAR is highly dependent on chlorophyll concentration. However, the spectral composition of underwater light is narrowing with water depth regardless of phytoplankton biomass.Green light is transmitted best, even at extremely low chlorophyll concentrations. This is explained by the selective absorption of blue light by dissolved organic substances and red light by the water molecules. Nevertheless, significant correlations were found between vertical attenuation coefficients of downwelling spectral irradiance and chlorophyll concentrations at all wavelengths. The slopes of the regression lines were used as estimates of chlorophyll-specific spectral vertical light attenuation coefficients (K _c()).The proportions of total upwelling relative to total downwelling irradiance (reflectance) increased with water depth, even when phytoplankton were homogeneously distributed over the water column. Under such conditions, reflectance of monochromatic light remained constant. Lower reflectance of PAR in shallow water is explained by smaller bandwidths of upwelling relative to downwelling light near the water surface. In deeper water, by contrast, the spectra of both upwelling and downwelling irradiance are narrowed to the most penetrating components in the green spectral range. Reflectance of PAR was significantly correlated with chlorophyll concentration and varied from 1% and 1-% at low and high phytoplankton biomass, respectively. Over the spectrum, reflectance exhibited a maximum in the green range. Moreover, in deeper layers, a red maximum was observed which is attributed to natural fluorescence by phytoplankton chlorophyll.     

Coupling of strontium and calcium cycles in Lake Constance

The contents of Sr and Ca were measured weekly in Lake Constance in 1986. Epilimnetic concentrations of Ca changed between 1.30 × 10^-3 mol l^-1 (during homothermy) and 0.9 × 10 -3 mol l^-1 (during thermal stratification). The seasonal fluctuations of Ca were correlated with those of Sr (between 4.61 and 5.36 mol l^-1). The epilimnion was permanently oversaturated with respect to calcite but not with respect to SrCO₃. Analysis of the settling process by use of sedimentation traps revealed two short episodes of very high authigenic settling fluxes of CaCO₃, triggered by phytoplankton diatoms. Seasonal changes of the Ca contents (between 4.1 and 30.7 percent of the dry weight) and of the Sr concentrations (from 12 to 75 × 10^-3 percent) in the settling material were closely correlated. This suggests a coprecipitation mechanism with a nearly constant stoichiometry of (atoms Sr/atoms Ca) × 1000 of 0.84. Coprecipitation of Sr or Ca with organic matter was insignificant. In the hypolimnion some Sr and Ca were released from the settling material. These results strongly suggest that the cycle of Sr in Lake Constance is driven predominantly by coprecipitation with calcite. The principal chemical mechanisms leading to coprecipitation are discussed.     

Location-dependent infection of fish parasites in Lake Constance

Perch Perca fluviatilis and roach Rutilus rutilus were caught at various locations around Lake Constance (Bodensee). Infection of perch and roach with the eyeflukes Diplostomum spathaceum and Tylodelphis clavata was greatest in the western location (Bottighofen). The varied occurrence of parasite species at different locations indicated that maximum interchange between fish populations was slight. Whitefish Coregonus lavaretus migrating up the River Rhine were less infected with both the tapeworm Proteocephalus exiguus and the copepod Ergasilus sieboldi than whitefish from the middle of the lake. Some of the parasites had already left their hosts. Newly established infections were not found in migrating whitefish.     

Prehistoric land use as recorded in a lake-shore core at Lake Constance

The second part of a pollen profile from Hornstaad/Lake Constance (Germany), containing the Atlantic and Subboreal (6400 cal B.C. to 700 cal B.C.) is presented. The diagram has a sampling interval of 1 cm and an average time resolution of 10 years. The cereal curve provided the basis for cereal zones, which are used to classify the human impact. Twenty-six cereal zones can be distinguished, most of them divided into subzones, from 5500 cal B.C. to 700 cal B.C. They correspond to both known and, mostly, unknown settlements in the surrounding landscape from the Early Neolithic to the Late Bronze Age. Charcoal and chemical analyses as well as sediment accumulation, confirmed by accelerator dates, provide evidence for human impact on the environment.A contribution to the 8th IPC, Aix-en-Provence, Sept. 1992     

Trophic interactions among heterotrophic microplankton,nanoplankton, and bacteria in Lake Constance

A considerable portion of the pelagic energy flow in Lake Constance (FRG) is channelled through a highly dynamic microbial food web. In-situ experiments using the lake water dilution technique according to Landry & Hasset (1982) revealed that grazing by heterotrophic nanoflagellates (HNF) smaller than 10 µm is the major loss factor of bacterial production. An average flagellate ingests 10 to 100 bacteria per hour. Nano- and micro-ciliates have been identified as the main predators of HNF. If no other food is used between 3 and 40 HNF are consumed per ciliate and hour. Other protozoans and small metazoans such as rotifers are of minor importance in controlling HNF population dynamics.Clearance rates varied between 0.2 and 122.8 nl HNF^–1 h^–1 and between 0.2 and 53.6 µl ciliate^–1 h^–1, respectively.Ingestion and clearance rates measured for HNF and ciliates are in good agreement with results obtained by other investigators from different aquatic environments and from laboratory cultures. Both the abundance of all three major microheterotrophic categories — bacteria, HNF, and ciliates — and the grazing pressure within the microbial loop show pronounced seasonal variations.     

Movements of ultrasonically tagged brown trout (Sulmo trutta L.) in Lake Constance

In Lake Constance from September 1986 to May 1988 13 adult lake dwelling brown trout ( Sulmo trutta L.) were tagged with ultrasonic transmitters and tracked almost continuously for up to 13 days. Two behaviour types were observed: (a) random movement in locally restricted areas and (b) excursions of up to 40 km distance. Swimming activity during the day was significantly higher than at night in most experiments. In summer swimming depth ranged between 8 and 16 m, and in winter between 0 and 3m. The preferred water temperature was about 14°C in the thermally stratified waterbody. During the experiments mean swimming speed ranged between 0.3 km h⁻¹ (0.1 bodylengths s⁻¹) and 0.9 km h⁻¹ (0.6 bodylengths s⁻¹).     

Distribution and onshore migration behaviour of burbot larvae in Lake Constance, Germany

Larval abundance of burbot Lota lota in the pelagic zone of Lake Constance, Germany, peaked during April and remained at a constant but lower level until mid‐June. From the end of May onwards a significant diel vertical migration pattern was observed: while burbot larvae were distributed above as well as below the thermocline in the daytime with the highest percentages of abundance at water depths of 30 and 50 m (below the thermocline) on 5 and 25 June, they were concentrated from 2 to 15 m (above the thermocline) during the night. This migration pattern coincided with a significant decline in the food items preferred by burbot at this life stage, cyclopoid copepods. This phase of diel vertical migration lasted for c . 4 weeks until the burbot larvae suddenly disappeared from the pelagic zone. This indicated a short phase, lasting only a few days, of larval settlement into profundal benthic habitats. This was supported by a significant, abrupt decrease in the absolute growth rates of the larvae at day 56 after hatching. The day–night pattern of vertical migration observed could be assumed to be a transition phase from a pelagic to a benthic lifestyle, as reported for juveniles of several other, marine gadoid species.     

Human impact as registered in the pollen record: some results from the western Lake Constance region,Southern Germany

Pollen analytical results from a littoral profile taken in Lake Constance compared with pollen profiles from small kettle holes nearby form the basis for conclusions concerning human population density, the economy and environment from the Neolithic period to the Middle Ages. Early Neolithic human impact is implicated in a lime decline and also the expansion of beech. The late Neolithic lakeshore settlements caused a decline of elm, beech and lime and, by shifting cultivation, considerably changed the forest cover. The settlements were abandoned after less than 100 years. There were long periods without distinct human impact in the middle and towards the end of the late Neolithic period. Since at least the Late Bronze Age there has been permanent habitation in the region. Human impact was greatest in the High Medieval period and later, and was also substantial in the late La Tène and Roman periods. Distinct declines in human impact can be observed between the La Tène and Roman periods and in the Migration and Merovingian periods. In these intervals, open land and grazed oak forest were replaced by birch and later on by beech forests. The decreases in human impact are not of the same intensity in all diagrams.     

Fecundity of whitefish (Coregonus lavaretus) during the eu-and oligotrophication of Lake Constance

About 20 ovaries of the whitefish 'Blaufelchen' ( Coregonus lavaretus L.) of Lake Constance (Bodensee) were collected annually from 1964-1991. Absolute and relative fecundity peaked in the early 1980s, lagging about 2 years behind the maximum of total-P in the water (during the circulation period). Out of the biological time-series of Lake Constance, whitefish fecundity is the only one known to follow the phosphorus curve, and this may be the first time-series documented case of parallel trend reversal in the trophic state of a lake and fish biology. It is concluded that fish fecundity serves, at best, as an unspecific monitor of the overall well-being of the fish.     

Dissolved oxygen dependent phosphorus release from profundal sediments of Lake Constance (Obersee)

Phosphorus release rates from profundal sediments of Lake Constance (Obersee) have been determined in D.O., pH regulated sediment-water systems. Above 10% O₂ saturation (> 1.2 ppm D. O.) and with pH as in situ, no net release could be found. Sedimentations of diatom sludge (Asterionella formosa) and carbonate-phosphate coprecipitate (CaCO₃.CaHPO₄) increased the release to 0.5 mg × m^–2 × d^–1 which, however, will not be relevant to the P balance in Obersee. The annual phosphorus accumulation in profundal Obersee and Ueberlingersee is, therefore, observed as due to sinking of phosphorus-bound detritus during the stagnation period.The experimental work was carried out at the Limnological Institute of the University of Freiburg/Breisgau (West Germany) and has been supported by the Industrieverband Körperpflege und Waschmittel e.V. and the Gernan Research Council (DFG)The experimental work was carried out at the Limnological Institute of the University of Freiburg/Breisgau (West Germany) and has been supported by the Industrieverband Körperpflege und Waschmittel e.V. and the Gernan Research Council (DFG)     

Tidal variations in suspended matter floc size in the Elbe river and Dollard estuaries

In-situ floc size measurements were made in suspended matter of the Elbe and Dollard estuaries. Floc size was found to be generally smaller in the surface water than in the bottom water and varied systematically with time in relation to the tidal phase. Maximum floc size was also related to particle concentration and, in the Dollard, probably also to flow on and off the tidal flats. Salinity and the total organic matter content of the suspended matter played a minor or no role. Since flocs break up into uniform size distributions during sampling and analysis, Coulter counter particle size was about constant during the tidal cycle. temporarily at Netherlands Institute for Sea Research, Texel, The Netherlands.     

The role of suspended matter in the distribution of dissolved inorganic phosphate,iron and aluminium in the Ems estuary

In winter 1992/1993, a persistent local maximum in fluorescence, dissolved iron, dissolved aluminium and dissolved inorganic phosphate was found, upstream of the turbidity maximum in the freshwater zone of the Ems estuary (The Netherlands — Federal Republic Germany; western Europe). Upstream of this local maximum values ranged from 6 to 9 rel. units fluorescence, 0.9 to 2.4 μmol dm⁻³ iron, 0.5 to 0.7 μmol dm⁻³ aluminium and 0.6 to 2.3 μmol dm⁻³ dissolved inorganic phosphate. Within the maximum peak values of 24 rel. units fluorescence, 5.8 μmol dm⁻³ iron, 1.4 μmol dm⁻³ aluminium and 8.3 μmol dm⁻³ dissolved inorganic phosphate were observed. Downstream, fluorescence (indicator of dissolved organic carbon) showed conservative mixing with sea water, whereas dissolved iron, aluminium and dissolved inorganic phosphate did not. Dissolved aluminium and iron were quickly removed from solution to reach values of ∼100 nmol dm⁻³ aluminium and ∼0.3 μmol·dm⁻³ Fe at salinities of approximately 7 PSU. Further seaward iron concentrations gradually decreased to levels below 0.04 μmol dm⁻³. Dissolved aluminium first decreased to ∼20 nmol dm⁻³ at 29 PSU and increased again to concentrations of 30–44 nmol dm⁻³ at higher salinities. Dissolved inorganic phosphate, however, first decreased to upstream concentrations before reaching a secondary peak in the mid-estuarine reaches. At salinities >25 PSU dissolved inorganic phosphate mixed conservatively with sea water. It is hypothesized that adsorption-desorption equilibria are responsible for the local maximum values of fluorescence (DOC), iron, aluminium and dissolved inorganic phosphate. The similarity between the observed curves suggests a common underlying process, possibly related to the adjustment of new equilibria between suspended matter of marine and riverine origin.     

Trace elements in suspended particulate matter from the Yarra River,Australia

Suspended particulate matter (SPM) was collected from two sites in the Yarra River, Australia under a range of flow conditions using a continuous flow centrifuge. The SPM from the upstream, largely rural, site at Warrandyte had higher concentrations of organic matter, phosphorus and manganese. SPM collected from the downstream, largely urban, site at Heidelberg had elevated concentrations of lead and zinc. The concentrations of iron, copper and chromium in the SPM changed little between the two sites.Over the study period, the flow-weighted mean concentration of SPM increased 5-fold between the two sites and the load increased 7-fold. The annual load of SPM transported past Heidelberg was estimated to be 170 000 tonne, with approximately 80% occurring during high flows (> 15 m³ s^-1 ). Detailed study of the SPM concentrations during flood events suggests that the northern tributaries to the Yarra are the main contributors of SPM in the region between Warrandyte and Heidelberg.The mean annual load of total phosphorus transported by the Yarra River at Heidelberg was estimated to be 220 tonne, approximately 2.5 times greater than at Warrandyte. Approximately 60% of this load was associated with SPM. The majority (ca. 80%) of this SPM-bound phosphorus was extractable with 0.1 M NaOH, and is therefore potentially biologically available.There was little difference between the two sites in the flow-weighted mean concentrations of iron, copper and chromium in SPM. The manganese concentration was approximately halved between Warrandyte and Heidelberg, with most of the loss occurring in the exchangeable and reducible fractions. Lead and zinc concentrations in SPM increased 15 to 16-fold between the two sites, with most of this increase occurring in the exchangeable and reducible fractions. This is some cause for concern, since metals in both these fractions could become available to biota under conditions known to exist in the Yarra estuary.     

南海南部悬浮颗粒物脂肪酸组成

中国水产科学研究院南海水产研究所"南锋号"科考船在2012年2月22日—3月20日调查期间,对南海南部海域0 m、75 m和150 m层水体悬浮颗粒物进行了脂肪酸(FA)组成的研究。FA含量在表层、75 m层和150 m层的变化范围分别为9.9—15.65μg/L,10.45-14.45μg/L和9.65—16.45μg/L。FA与叶绿素a的比值垂向变化非常大,在表层和150 m层都大于70,而在75 m层小于30(除A7)。悬浮颗粒物的FA组成以饱和脂肪酸和单不饱和脂肪酸为主,而多不饱和脂肪酸含量较低。饱和脂肪酸主要包括C16:0和C18:0,其次是C12:0,单不饱和脂肪酸主要包括C14:1n3、C16:1n7和C16:1n9,多不饱和脂肪酸主要为C18:2n6和C22:2n6。主成分分析表明,第一主成分主要与C16:0、C18:0、C20:0等正相关,可认为第一主成分主要表征浮游植物和碎屑,而第二主成分所表征的可能与浮游动物等有关的信息。悬浮颗粒物的脂肪酸标记物中,C16:1n7/C16:0和∑C16:1/∑FA之间呈显著正相关,同时C16:1n7/C16:0与∑C18/∑FA呈显著负相关,将C16:1n7/C16:0和C16:1/∑FA结合起来适宜于指示硅藻类的组成,∑C18/∑FA可用来指示甲藻类组成。     

东湖沉积物中微生物磷脂的垂向分布

以武汉东湖柱状沉积物为研究对象,利用磷脂法测定了3个采样点各层的微生物量,同时测定了沉积物中各层的pH,简要分析了沉积物中磷脂含量的垂向分布与pH垂向分布的相关性。结果表明:各样点沉积物中磷脂平均含量分别为:1号点59.40nmol/g.dw,2号点为20.56nmol/g.dw,3号点为31.57nmol/g.dw。在沉积物的垂向分布上,微生物量与pH均随着沉积物深度的增加而降低,并且存在很高的相关系数。     

The first decade of oligotrophication in Lake Constance

Phytoplankton biomass and species composition were measured with a relatively high temporal resolution (once or twice a week during the growing season) from 1979 to 1989 in Lake Constance/Überlingersee. Over this period soluble reactive phosphorus (SRP) concentrations during winter mixing were reduced by ca. 50% from 104 to 47 g 1^–1, which caused a prolongation and amplification of the epilimnetic P depletion during the growth period. Seasonal dynamics of phytoplankton reacted to the decrease of SRP in the following ways: (1) Algal biomass decreased at least proportionally to the winter SRP concentrations in summer, but not in spring and autumn when biomass fluctuated irregularly. (2) The peak of biomass concentration changed from summer to spring. (3) The earlier onset of epilimnetic P depletion during the season in recent years promoted a stronger growth of some pennate diatoms in spring. It caused an amplification of the silicon depletion in summer, which may cause still greater reduction of diatoms and total algal biomass in summer. (4) Reduction of algal biomass during the clear-water phase proper became shorter and less pronounced. (5) The temporal variability of algal biomass decreased in summer and autumn but not in spring. (6) Average cell sizes remained unchanged in summer and autumn but increased in spring during the beginning of oligotrophication. These results are largely in agreement with other studies on lake restoration and expectations derived from the PEG (Plankton Ecology Group) model (Sommer et al. 1986). They show that a 50% reduction of SRP concentrations during homothermy may have pronounced effects on seasonal dynamics of algal biomass in a large and deep lake. The algal response to the external change of SRP concentrations can be described by the Le Chatelier principle, implying that the internal structure of the system (e.g. species composition) changes in order to minimize the effect of the external pressure (e.g. reduction of total biomass). Suggestions are made as to how this system behaviour may emerge from local interactions.     

Pigment patterns in suspended matter from the Elbe estuary,Northern Germany

In the Elbe hardly anything is known about the actual fate of phytoplankton and the resultant pigment composition of suspended matter. As part of a longterm study on the role of suspended matter in the cycles of nitrogen and associated oxygen consumption processes in the Elbe estuary in northern Germany (‘Sonderforschungsbereich 327 Elbe’ project) and the characterization of estuarine and coastal water bodies with regard to the transport of pollutants such as heavy metals, we have started to characterize suspended matter with regard to the pigments present therein. This will allow us to study phytoplankton turnover and to determine the role of phytoplankton decay mechanisms in the mobilization, binding, and transport of pollutants associated with particulate matter. Our first data on the pigment composition of suspended matter from the Elbe and particularly over the region of Hamburg harbour, obtained using a High Performance Liquid Chromatography (HPLC) method, is presented. The pigment concentrations varied considerably over the summer months. Values up to 250 mg l⁻¹ of chlorophyll a were observed upstream of Hamburg. We found that on its course through Hamburg the concentrations (μg g⁻¹ of particulate matter) of all pigments in the Elbe drop to under half those found upstream of Hamburg. The pigment concentrations in the turbidity maximum were significantly lower than in the rest of the estuary due to the decline of algae as a result of inadequate light conditions and the salinity gradient. The highest particulate matter concentrations were found in the turbidity maximum and just downstream of Hamburg. The highest particulate organic carbon values were found just downstream of Hamburg. The presence of of fucoxanthin and the chlorophyllsc andb, and the changes in pigment patterns were indicative for the dominant algal classes and the phytoplankton succession in the suspended matter. The ratio of chlorophylla to lutein was found to be a possible indicator of phytoplankton breakdown.     

Effect of suspended mineral matter on production characteristics of bacterio- and phytoplankton

The effect was determined of organo-mineral detritus (OMD), one of the components of suspended mineral matter in aquatic ecosystems, on the production characteristics of bacterioplankton (bacterial production P _b and destruction of organic matter R _b, as well as bacterial growth efficiency BGE). The relation was determined between these parameters and the ratio of the content of suspended mineral matter M to the total organic carbon content (M/TOC). More active utilization of organic matter by bacterioplankton in the presence of OMD resulted in its positive effect on specific production characteristics of the phytoplankton.     

梯级水电站开发对香溪河悬浮颗粒物粒径及浓度的影响

通过对香溪河悬浮颗粒物粒度及浓度的实验分析,研究梯级水电站开发对河流悬浮颗粒物的影响,结果表明:(1)香溪河干流悬浮颗粒物粒径由上游到中游逐渐减小,并且在无水电站干扰时颗粒物粒径减小幅度较大;(2)从进水口至出水口河段,水电站悬浮颗粒物粒径总体变化不显著;(3)水电站从进水口河段至出水口河段,总悬浮颗粒物浓度(CTPM)在某些位置有所增加,有机颗粒物浓度(CPOM)无明显变化.悬浮颗粒物粒度及浓度的变化与水流流速及流量有着相当大关系.     

Environmental chemistry of rivers and lakes, Part VII. Fractionation by calculation of suspended particulate matter in Lake Biwa into three types of particles of different origins

During the period from July 1992 to March 1995, suspended particulate matter in Lake Biwa was collected at 1-month intervals, and the contents of Al, Si, and P were determined. Based on the analytical data, the particulate matter was fractionated by calculation into three types of particles of different origins: particles of terrigenous origin, particles of diatom origin, and particles due to microorganisms except for diatoms. The relative abundance of the respective particles was featured in water depth-time (month) diagrams, with contours in terms of weight per liter of lake water. As a result, the characteristic distributions of the particles were revealed, and their inherent roles in natural purification were distinguished from each other. Of the three types of particles, the particles of diatom origin were anticipated to be the principal scavengers not only of nutritious elements of silicon and phosphorus, but also of various metal ions dissolved in the lake. Received: October 5, 2000 / Accepted: June 6, 2001