Lake In Central Italy Research Articles

Invasive crayfish in Europe: the impact of Procambarus clarkii on the littoral community of a Mediterranean lake

Summary1. Despite the growing number of non‐indigenous crayfish species introduced worldwide, little scientific attention has been given to their effects on the recipient communities. Here, we quantified the impact of adult red swamp crayfish (Procambarus clarkii) on key components of the littoral community of a mesotrophic lake in central Italy. We used two densities of crayfish plus a no‐crayfish control, and two complementary methods –in situ enclosures and a laboratory study.2. Both experiments showed that P. clarkii strongly affects the community even at a low density (4 m−2), although a high crayfish density (8 m−2) showed a more pronounced impact in a shorter time.3. In enclosures, P. clarkii quickly consumed the pond snail Haitia acuta, notwithstanding its anti‐predator behaviour, but not the mosquitofish Gambusia affinis. The biomass of the hydrophytes Nymphoides peltata and Potamogeton spp. was strongly reduced by crayfish grazing, coupled with their non‐consumptive plant clipping and uprooting, which were particularly intense in the case of Potamogeton crispus. In contrast, Utricularia australis was avoided by P. clarkii, even when other resources were exhausted.4. The introduction of P. clarkii could reduce biodiversity and increase biotic homogenisation in a short time.

Microcystin diversity in a Planktothrix rubescens population from Lake Albano (Central Italy)

The cyanobacterium Planktothrix rubescens Anagnostidis & Komarek (previously Oscillatoria rubescens DC ex Gomont) is present in several Italian lakes and it is known to produce cyanotoxins. The dynamics and toxin production of P. rubescens population in Lake Albano, a volcanic crater lake in Central Italy, has been studied for 5 years (January 2001–April 2005). Winter–spring superficial blooms with frequent scums were observed every year. Total microcystin (MC) levels were measured from April 2004 to October 2005 by liquid chromatography-tandem mass spectrometry. MC levels up to 14.2 μg/l were measured, with high concentrations found in summer at a 20–25 m depth. The intracellular toxin content varied between 1.5 (surface, January 2004) and 0.21 pg/cell (surface, May 2004). Six different MCs were detected, the most abundant being two desmethyl-MC-RR isomers. Of the 13 water wells monitored in the Lake Albano area, two of them showed MC contamination during winter, confirming the ability of these toxins to migrate through groundwater towards public water sources. These results highlight the need for further studies on the mobility and fate of these pervasive cyanobacterial toxins.

Nutritional quality and safety of European perch ( Perca fluviatilis) from three lakes of Central Italy

European perch ( Perca fluviatilis) harvested from three lakes of Central Italy were studied in different seasonal periods of a year to evaluate their nutritional quality and some safety aspects related to the pollution of the aquatic environment. The lakes considered, located in the Latium region, differed with respect to their volcanic (Bolsena and Bracciano Lakes) or artificial (Salto Lake) origin. Fillets of fish caught in the three lakes were characterised by good protein (17–19%) and mineral contents and low lipid levels (0.6–1.2%) throughout the year. Total lipids were characterised by low cholesterol levels (41.9–74.7 mg/100 g) and high percentages of total n − 3 polyunsaturated fatty acids (27.7–33.8% of total fatty acids), in particular docosahexaenoic acid (14.2–25.3% of total fatty acids). The qualitative analysis of the stomach content of perch confirmed their predatory feeding behaviour. The chemical and nutritional profiles of perch from the three lakes were comparable except for rubidium and cesium levels, which were higher in the muscle tissues of perch from the volcanic lakes. These minerals may represent elements of traceability of the origin of fish. Low levels of organochlorine pesticides and polychlorinated biphenyls, well below the Italian and European action limits, were detected in the muscle tissue of perch from all three lakes.

Modelling the long-term behaviour of radiocaesium and radiostrontium in two Italian lakes

The present paper describes the application of a state-of-the-art model to two lakes in central Italy (Trasimeno and Monterosi) for the assessment of migration parameters of 137Cs and 90Sr (migration velocity to sediment, transfer rates from sediment to water and to bottom sediment). Applications of a compartment model and a model based on the diffusion equation to predict the behaviour of pollutants in water and through bottom sediment are presented and discussed. The application of the diffusion equation shows some difficulties of a general nature and typical of such a modelling approach. Moreover, there is no evidence of significant improvements of the model performances when the diffusion equation is applied. Very low levels of sedimentation rate of suspended matter in Lake Monterosi were evaluated by the quantitative assessment of radiocaesium migrating to bottom sediment. This suggests that, in this lake, the removal of radionuclide from the water column is mainly due to the turbulent mixing of bottom sediment causing radionuclide burial.

Mineral magnetism and geomagnetic secular variation of marine and lacustrine sediments from central Italy: timing and nature of local and regional Holocene environmental change

Sediment core palaeomagnetic and mineral magnetic records from two crater lakes in central Italy and from the western margin of the Adriatic Sea have been used to evaluate local and regional responses to Holocene environmental change. In all cores, sediment magnetism reflects the interplay between catchment material and the in situ production of bacterial magnetite (magnetotactic bacteria). In the lakes, the earliest Holocene sediments record a waning catchment input that we attribute to rising lake levels and increased tree cover in the catchment. From ∼9000 to 5000 yr BP, both lakes become anoxic, a consequence of water-mass stratification driven by high lake levels. Bottom-water anoxia also developed in the Adriatic, with sapropel S1 produced between ∼9000 and 7000 yr BP. Subsequently, the lake and Adriatic mineral magnetic records show evidence for increased catchment delivery, consistent with pollen evidence for Bronze Age deforestation. In the lakes, this evidence is first recorded at ∼4300 yr BP and a number of distinct clearance events are recorded. In comparison, at Adriatic site RF93-30, lithogenic input increases abruptly at ∼3500 yr BP and is followed by a slowly changing record of waxing and waning sediment delivery. Inter-site comparisons of palaeomagnetic data point to a possible link between the magnitude of the bacterial magnetite component and the recorded magnetic inclination. The sites are at near identical latitudes and have similar sediment accumulation rates but the Adriatic sites have a core-average magnetic inclination that is some 10° steeper than the lake average values. We suggest that the large dipole moment of the magnetosome chains, which in life produce the passive alignment of the bacterium along the local geomagnetic field line, produce a more faithful (albeit smoothed) record of the geomagnetic field.

Classification of the ecological status of volcanic lakes in Central Italy

A synthesis is made of biological data collected in the last three decades on five volcanic lakes in Central Italy with the aim of evaluating their environmental status by means of biological parameters related to zooplankton, littoral and profundal zoobenthos frequently used to detect water quality changes in lakes. A number of bioindicators and bioindices were selected for this purpose, as far as possible following an integrated approach using information drawn from physical and chemical variables. Our results allowed the lakes to be classified according to their biological quality level, which proved to be in good agreement with physical and chemical diagnoses. Lake Bracciano exhibited the best environmental quality, due to the presence of a ring waste water collecting system, to its large size and depth, and to its strong hydrodynamism. Lake Martignano followed, with some symptoms of stress in the hypolimnion due to a marked summer deoxygenation. Oxygen depletion in the profundal characterized also Lake Vico, which showed a mesotrophic condition in the sixties, and 20 years later now shows clear signs of increased trophy (meso-eutrophy). Lake Albano seemed meso-eutrophic with total absence of fauna below a depth of 120 m due to a meromictic status. Finally Lake Nemi, exposed to domestic wastes in the 70s, suffered a heavy eutrophication with dramatic algal blooms and fish kills. Following the diversion of discharges that occurred in the early 90s, today this lake is characterized by the partial improvement of many ecological features. The need for integration between physical and chemical analyses and biological data in order to obtain a reliable evaluation of lake environmental quality is stressed, especially as far as routine implementation in managing and recovery procedures is concerned.

The Status of the Twaite Shad, Alosa agone, in Italy and the Western Balkans

Abstract. The twaite shad, Alosa agone, is still quite common in Italy and the western Balkans, but locally is endangered or extinct. Two eco‐phenotypes are recognized: the migratory‘Cheppia’or‘Laccia’and the landlocked‘Agone’. The two forms have never been in contact, at least in Italy. The migratory form is more endangered since barriers and dams prevent it from reaching upstream spawning grounds. A few reproductive communities are documented, e. g. in the Po River in Italy and Neretva River in Croatia. Resident stocks have increased to substantial populations in the large lakes of Italy, especially in the last ten years, probably as a result of improved water quality. The landlocked form from northern Italy was successfully introduced into lakes of central Italy about 75 years ago. In Sardinia a population derived from the migratory form was established about 80 years ago in the artificial Lake Omodeo. In Croatia the‘Cheppia’seems to live only in the lower course of the Neretva River. In Montenegro,‘Cheppia’and‘Agone’live in sympatry in Lake Skadar, but a dam built in 1960 caused a strong decline of both forms. The twaite shad is a very variable species, able to modify its morphology and biology according to its adaptation to freshwater or marine biotopes. In the Mediterranean area, only one taxon should be then recognized, Alosa agone (Scopoli, 1786). This will replace Alosa fallax (Lacépède, 1803), a taxon described from the Atlantic drainage area which seems to be distinct from Mediterranean populations. A survey of the distribution of reproductive communities of the migrating form in the Mediterranean area must be carried out.

Palaeoproductivity and environmental changes during the Holocene in central Italy as recorded in two crater lakes (Albano and Nemi)

Three cores from two crater lakes in central Italy (Albano and Nemi) spanning the last ca. 11 kyr BP are discussed here. They were analysed for organic matter, dry density, algal and photosynthetic bacteria pigments, diatoms and Cladocera. These palaeolimnological records show great internal consistency in their response to distinct, but inter-related, aspects of the lake-catchment system, and reflect major changes in these systems particularly in lake productivity. The early Holocene was characterised by very high productivity at both sites. Trends in productivity are similar for many proxies in the Holocene records of Lake Albano and Lake Nemi. Trophic levels throughout much of the period of human activity (ca. 4000 yr BP onward) are lower but have remained relatively high and stable at both lakes. It is only in the last few decades that inferred productivity levels have exceeded those of the early Holocene. Statistical analysis (CONstrained Incremental Sum of Square cluster analysis, CONISS) showed five distinct periods during the Holocene characterised by major variations in the abundance and community structure of biological remains and geochemistry. A comparison of results from the different taxonomic groups has enabled the reconstruction of phases of increased productivity and the recognition of signals of anthropogenic impact on the lakes and their catchments. From published pollen diagrams, nine major deforestation events are recognised during the Holocene. These events, in particular the one which occurred in both lakes at 1800 yr BP and identifies the Roman Period, plus another at 3000–3500 yr BP related to agricultural activity during the Bronze Age, produced profound changes in the pelagic community structure of diatoms and Cladocera, which in some cases were even more marked than the accelerated eutrophication seen in recent times. The mid-Holocene climatic transition is also clearly evident and is characterised by a strong decrease in the concentrations of the biological proxies. Most of the observed lacustrine environmental changes are almost synchronous in the two lakes indicating the importance of regional rather than local changes.

Palaeoenvironmental and palaeoclimatic implications of the Late‐Quaternary sediment record of Vico volcanic lake (central Italy)

AbstractA 15‐m‐long sediment core recovered from the Lago di Vico caldera lake in central Italy has been the subject of macrofacies description and sedimentological (organic carbon content, grain size and mineralogy) investigation. The results have been integrated with the pollen data from the same core in order to provide a regional climatic and environmental history, with inferences on past lake levels and on moisture and temperature regimes. Radiometric (14C and 40Ar/39Ar) dating, biostratigraphical considerations and tephra analyses provide a chronological framework and indicate that the sequence spans the last 90 000 yr. Several moist periods have been identified that were characterised by enhanced weathering by hydrolysis of the catchment rocks. These alternated with relatively dry phases associated with lowering of lake‐levels. The lowest hydrolysis efficiency of the whole record, accompanied by notable aeolian deposition, was attained during the last glacial phase but moisture conditions were such that the lake‐level did not decrease, probably owing to reduced temperatures. Evidence for cool climate also emerges for the early Pleniglacial. The highest available moisture was achieved within the Holocene at 5 kyr BP. The Late Holocene does not show either increase of aridity or degradation of the vegetation cover, until at least Roman times. Copyright © 2001 John Wiley & Sons, Ltd.

Evidence for short-lived oscillations in the biological records from the sediments of Lago Albano (Central Italy) spanning the period ca. 28 to 17 k yr BP

We report the results of analyses of pigments (derived from algae and photosynthetic bacteria), diatoms and invertebrate fossil remains (ostracods, cladocerans, chironomids) in two late Pleistocene sediment cores from Lago Albano, a crater lake in Central Italy. The record contains evidence for oscillations in lake biota throughout the period ca. 28 to 17 k yr BP. The earliest of these are contained in the basal 3.5 m of light olive-gray and yellowish-gray spotted muds sampled in core PALB 94-1E from 70 m water depth. The later oscillations are best represented in the more extended sediment sequence recovered from a second core site, PALB 94-6B, in 30 m water depth. The sediments at site 1E, containing the earlier oscillations (ca. 28-24 k yr BP), predate any sedimentation at the shallower site, from which we infer an initially low lake level rising to permit sediment accumulation at site 6B from ca. 24 k yr onwards. At site 6B, massive silts rich in moss remains are interbedded with laminated silts and carbonates. These sediments span the period ca. 24 to 17 k yr and are interpreted as representing, respectively, times of shallow water alternating with higher lake stands, when the lake was stratified and bottom water was stagnant. A range of mutually independent chronological constraints on the frequency and duration of the oscillations recorded in the lake biota indicate that they were aperiodic and occurred on millennial to century timescales. We interpret them as responses to climate forcing through its impact on lake levels and changing aquatic productivity. The time span they occupy, their frequency and their duration suggest that at least some of these changes may parallel both the Dansgaard-Oeschger events recorded in Greenland Ice Cores and the contemporary oscillations in North Atlantic circulation documented in marine sediment cores.

Sediments from Lago di Mezzano, central Italy: a record of Lateglacial/Holocene climatic variations and anthropogenic impact

Microscopic, geochemical and pollen analysis of sediment samples of a Lateglacial/Holocene profile from Lago di Mezzano, a maar lake in central Italy, reveals evidence of significant climatic and human-induced environmental changes. Time control is provided by a combination of varve chronology and radiocarbon dating. The well-known Lateglacial climatic variations, a warmer interstadial and the Younger Dryas cold phase are clearly represented in all the parameters. During the interval between 9200 and 5600 cal. BP of the Holocene climatic optimum, annually laminated, organic-rich diatom gyttja was deposited. Two periods of diminished total organic carbon are identified within this interval. The first one (P1) ranges from 8200 to 7800 cal. BP while the second (P2) is centred around 6500 cal. BP. During P1, a predominance of diatoms ( Stephanodiscus parvus and S. minutulus) over other algae (represented by the total organic carbon content) is observed. The timing of this period coincides with the early to mid-Holocene climatic transition, reported from ice cores and lake sediments (Stager and Mayewski, 1997). P2 is characterized by a decrease in all biogenic parameters including biogenic opal, organic carbon as well as arboreal pollen. From 5000 cal. BP to date, the sediment pattern changes coincide with the mid-Holocene climatic deterioration. In addition to these natural variations, human impact has been recorded and recognized from sedimentological features such as turbidites and charcoal, as well as from reduced arboreal pollen content. Two Middle Bronze Age (3700 cal. BP and 3300 cal. BP), Etruscan/early Roman (2500 cal. BP), Longobardic (ad 900) and‘modern settlements’ (since ad 1700) have been distinguished on the basis of these data.

Modelling the radionuclide balance in some water bodies of central Italy

This article illustrates the quantitative analysis of the radionuclide behaviour in some lakes of central Italy and in their outlets. The migration rates and the effective transport velocities of the radionuclides to sediment were estimated. In the examined lakes (Albano, Bolsena, Bracciano, Nemi and Vico), the concentrations of 90Sr and 137Cs show a marked exponential time decay due to the radioactive decay, the radionuclide removal by the outlets and the radionuclide migration from water to bottom sediments. It was estimated that the 137Cs average migration rate to sediment is 1.2 × 10 −9 s −1 corresponding to an effective migration velocity of 5.8 × 10 −8 m s −1. The radionuclide concentrations in watercourses Marta (outlet of Lake Bolsena) and Rio Vicano (outlet of Lake Vico) were fitted by exponential (decay) functions of the distance from the lake. The ‘half-distance’ of the above process (‘half-distance’ = the distance for the radionuclide concentration reduces to one half) is 12.6 km and 3.9 km for 137Cs in river Marta and Rio Vicano, respectively. The half-distances for 90Sr in the above watercourses are, respectively, 30 km and 5.8 km. The half-distances were quantitatively related to the effects of water dilution and to the radionuclide contribution from catchment. The analysed data offered the opportunity of calculating that the 90Sr contribution from catchment to the examined watercourses is in the order of 10 −3–10 −4 Bqs −1m −1 (radionuclide flowing per second and per metre of river).

Macrobenthos in Montedoglio Reservior, central Italy

An investigation was carried out on the macrobenthos of Montedoglio Reservoir, an artificial lake in central Italy. Seven qualitative and quantitative samplings, performed by drag netting and airlifting at 5 stations, revealed a total of 48 taxa during 1992–94. The highest density and most frequent terms were Tubificidae, Chironomidae of the genera Procladius, Tanypus, Chironomus and Polypedilium and Chaoboridae. Tubificidae were found mainly at a depth of 7–9 m, Chironomidae at 1–3 m. The modest density and low biological diversity values are probably attributable to the substrate characteristics and a drop in hypolymnic oxygen during thermic stratification. The oxygen stress at the lake bed, which was unexpected given the scarce planktonic productivity, may have been caused by recent impoundment.

Bioaccumulation of 137Cs in the Main Species of Fishes in Lakes of Central Italy

Bioaccumulation of ¹³⁷Cs in the Main Species of Fishes in Lakes of Central Italy

An 11 000‐year record of vegetation and environment from Lago di Martignano, Latium, Italy

AbstractA pollen diagram from Lago di Martignano, a maar lake in central Italy, provides an 11000‐year record of vegetation and environment change. The earliest pollen spectra are dominated by Artemisia and Gramineae, representing late glacial steppe vegetation typical of the Mediterranean region. Broad‐leaved forests were established by ca. 11 000 yr BP. Although Quercus initially dominated their canopy, a wide range of other mesophyllous trees were also present. Pollen values for sclerophyllous tree and shrub taxa characteristic of Mediterranean woodlands and scrub are initially low (<10%). After ca. 7000 yr BP, however, they begin to increase and rise to a peak of >40% of total land pollen at ca. 6700 yr BP, with Olea europaea the single most abundant taxon. Human influence upon the vegetation only becomes significant somewhat after this peak, with progressive clearance of woodland and expansion of herbaceous communities. Castanea sativa and luglans regia pollen is recorded consistently from the beginning of the rise in pollen values for taxa characteristic of Mediterranean scrub communities. Pollen values for arable crops increase progressively after ca. 5500 yr BP, following the peak pollen values for taxa characteristic of Mediterranean scrub vegetation. Late glacial and Holocene climate changes have been complex in this region, with the present character of the climate developing only during the last millennium. Rates of change of pollen spectra peak during this period.

The measurement of undrained cohesion in normally consolidated lacustrine clays

Geotechnical investigations have been carried out on normally consolidated slit clay deposits, resulting from the drying up of a Plio-Pleistocenic lake in Central Italy. In situ investigations included borings (with SPT and vane tests) and static cone penetration tests; undrained cohesion has been also measured by means of consolidated, drained triaxial tests.

Alterations of the plankton in a much polluted lake in central Italy (Latium), the volcanic Lake Nemi

Alterations of the plankton in a much polluted lake in central Italy (Latium), the volcanic Lake Nemi