Principal scientist C.N. Bianchi (ENEA, S. Teresa, La Spezia)
Background
A number of major benthic ecosystem types in the Mediterranean are dominated by animals. These include virtually most areas on incoherent soft bottoms, where the dominant biota is usually infauna, but also many areas on hard bottoms, where sessile invertebrates may shape the underwater landscape. The so-called "coralligene" is considered as the "climax" of the Mediterranean circalittoral zone and is of major interest for both scientific and practical reasons, due to it intrinsic value of biodiversity. Among the animal dominating on hard bottoms, species with high bioconstructional capability, such as corals and other clones or gregarious invertebrates with carbonatic exoskeletons, are important as structure builders and for harboring a rich associated fauna, thus increasing biodiversity. On the other end, soft bottoms cover the vast majority of the continental shelf and harbor many different infaunal communities whose composition and structure mostly change according to sediment features.
Zoobenthic communities are essentially composed of sedentary species, with little or no capacity of moving. Even agile species show little mobility, being usually tied to their territories in the range of meters or few tens of meter. This implies that long-lived invertebrates withstand and subsequently witness any environmental change, both "natural" (e.g., climatic) or anthropogenic. It is extremely difficult to tell climatic from anthropogenic effects on the marine benthic biota with the usual ecological tools (Lewis, 1996). To monitor shifts in the species composition of the nearly "immobile" benthic communities may be of help: for example, "southern" species may extend or become commoner northward in the presence of sea-water warming (Astraldi et al. 1995), whereas pollution and other anthropogenic influences should have little to do with this kind of change.
Another way of relating climatic fluctuations or change to benthic animals is sclerochronology. Many hard structures built by animals, such as carbonatic skeletons and shells, show different growth rates according to different climatic conditions. In living colonies of corals, for example, calcareous corallites may record climatic changes of the last decades (Barnes & Lough 1993). This is even more true in corals from temperate seas, such as the Mediterranean Sea, since seasonality - and hence density banding - is stronger (Peirano et al. 1996). Thus, sclerochronology may parallel lepidochronology for detecting decadal variability in growth and productivity and also to infer about climate variability.
Scientific objectives
Zoobenthic communities on both hard bottoms and shallow (especially sandy) soft bottoms are dominated by suspension feeders. Suspension feeders act as consumers of particulate organic matter (POM), which has been mainly produced in the planktonic systems. By this way, high biomass suspension-feeding macrobenthic communities can control primary and "paraprimary" production in the pelagic system. The conversion of pelagic biomass (consisting of small organisms with high weight-specific metabolic rates) into the biomass of large, long-lived benthic suspension feeders (with low weight-specific metabolic rates) may stabilize overall ecosystem behaviour (Ott, 1991).
Connections between plankton and benthos are very strong both from a structural and functional point of view. Appreciation of such links is forcing marine ecologists towards an integrated approach, bridging the gap in the seasonal and/or interannual discontinuity of species composition through life history analysis. Recently (Boero et al., 1996; and see references therein), emphasis has been given to this aspect, pointing out that plankton and benthos are not indipendent units and that their joint dynamics cannot be fully understood without an integrated investigation. It is now well recognized that almost all groups of aquatic organism may overcome adverse periods (months,years) as resting stages, the morphology of which is much different to that of the functional stages. In the sea, pelagic resting stages might remain suspended in the water column or, especially in coastal waters, sink to the bottom, and become incorporated into the sediments as spores, cysts or resting eggs.
Zoobenthic communities withstand the influence of both direct (e.g., changes in the temperature regime and in the frequency of periods of heavy sea) and indirect (e.g., influence of changed discharge rate of rivers). Zoobenthic community adjusts to climatic change by a modification in the recruitment and mortality patterns of the populations. Zoobenthic communities are particularly suited for an analysis of complex interactions of interannual climatic variations with the resident bottom fauna, that shows a vast array of response due to different life spans, from less than one year to many years.
Zoobenthic communities on both soft and hard bottoms have wide distribution along Italian coasts. Thus, the project will aim to compare interannual and seasonal variability in different areas, paying special to seasonal and interannual fluctuations of the population structure of some key-species. The role of the zoobenthos in increasing biodiversity will be analyzed especially for bioconstructional zoobenthos.
Subtasks
C.3.2.a - Interannual and seasonal variability of zoobenthic infaunal communities will be studied in Ligurian Sea, Tyrrhenian Sea and Adriatic Sea, to contrast local with global trends, the latter to be correlated with climatic fluctuations. In the Ligurian Sea, two main long-term data-sets are available: one on a sandy to muddy bottom off Chiavari, 10 m deep, 1977 to present (Cattaneo e Albertelli 1983; Albertelli e Fraschetti 1992; Albertelli et al. 1993, 1994a, 1994b, 1994c, 1996); and one in the Magra river estuary, 1987 to 1993 (Morri et al. 1989, 1991). In both sites, wide seasonal and interannual fluctuations have been evidenced. In the Tyrrhenian Sea, series of data are available from the coast tract between Argentario and Montalto di Castro (seasonal samples to 40 m of depth, 1983 to 1984) and from the gulfs of Naples (1987), Salerno (1981 and 1987) and Policastro (1982), at 2 to 100 m depth on various bottom types (Colognola et al. 1984; Maggiore et al. 1984; Russo e Fresi 1984; Gambi et al. 1984, 1986, 1996; Scipione et al. 1989; Somaschini, 1993. Surveys have been performed at quite large scale in order to encompass both both geographic (climatic) and local factors (sediment types, proximity of river mouths, presence of secondary hard substrata, of seagrass and algal covering, etc.). The influence of local factors have been seen to hide that of climatic ones, even though they act at a different spatial and temporal scale. In the Adriatic Sea, a long-term data base exists for a coastal area facing the Po river delta: 9 stations (depth from 2.5 to 8 m), on sandy to muddy sediments were sampled seasonally during the period from 1979 to 1994 (Ambrogi & Occhipinti Ambrogi 1987; Ambrogi et al. 1994, 1995). The aims of the present study are: 1) to analyse historical data, comparing different areas and situations, to generate hypotheses on change; 2) to continue or resume field-data, thus enlarging time-series at the various sites in order to estimate long-term variability; 3) to compare data from different areas and seas to detect large scale variability and to distinguish climatic and local influences.
C.3.2.b - Decadal change in a hard-bottom community will be studied in the Ligurian Sea, comparing present situation with historical data taken in the late 50's on a "coralligene" community between 20 and 50 m depth at P.ta Mesco (Rossi 1965). First evidences of change have been seen in the 80's (Peirano & Tunesi 1989; Peirano e Sassarini 1991) and have been correlated to local factors (coastal works, dumping, urban development). Photographic samples will be collected by SCUBA divers in exactly the same sites as in early studies. Comparison between previous and present data and correlation with climatic data will allow to tell climatic to local influences on change.
C.3.2.c - Populations dynamics of the benthic fish Thalassoma pavo will be studied in the Ligurian Sea. This is a southern species, very rarely recorded north of the Tuscan Archipelago in the past. Its repeated occurrence in the Ligurian Sea since 1985 has been considered as a clue of sea-water warming (Bianchi & Morri, 1993, 1994; Astraldi et al. 1995). There, it presently reaches sexual maturity and possibly reproduces.
C.3.2.d - Sclerochronology of the scleractinian coral Cladocora caespitosa (Peirano et al. 1996) will be used to compute growth and production in the past 50-60 years, to be correlated with temperature and other available climatic data.
C.3.2.e - Internannual and seasonal variability in growth and productivity of the bioconstructional bryozoan Pentapora fascialis will be studied in the Ligurian Sea. Results will be compared with climatic and hydrological data.
C.3.2.f - Resting stages will be studied in the “Mar Piccolo” of Taranto. There, a continuos monitoring on the bottom cyst bank (Belmonte et al., 1996) have been started since 1992, which already allowed to find out near 100 different cyst morphs within a density of approx. 160 millions of cyst per square meter.
The study is aimed to:
1) Identification of patterns of mid-term variations and short-term fluctuations in species compositions of phyto- and zooplanktonic assemblages, by correlations of stratigraphic analysis, chemico-physical and plankton data series with the typology and abundance of resting stages in the sediments.
2) Build-up of a cyst data bank, with an atlas of identification of the commonest resting stages, providing new explanations for the “mysterious” appearance of blooms and tools of previsional values.
3) Identifications of key organism/population with higher sensitivity to environmental changes reflected in correspondent rates of cyst production.
4) Finding out, by laboratory encystment-excystment bioassays, the environmental cues for key species with resting stages.
5) Investigation of the mechanism responsible for the suspension (dormancy) and/or the reversal of life cycles in selected organisms (e.g.: jellyfish, see Piraino et alo., 1996) at different level of biological organization (organism, cells molecules).
C.3.2.g - Transport of benthic species in the Mediterranean water masses Transport of benthic species in the Mediterranean water masses
Variability of benthic species transported by the main water masses of the Mediterranean
circulation will be studied.
Most of benthic species spent a part of their life in the plankton where they can be moved away by
water currents and reach new environments. Different strategies are used by benthic species to
widespread (Aliani & Meloni, 1996) and the interest in coupling current variability with changes in
species stocks is arising especially when related to climatic changes (Astraldi et al., 1995). Studies
on the dispersal of benthic invertebrates in the Mediterranean are rare although increasing interest
on species migration.
This work will focus on macrobenthic species that are transported by currents in strategic sites of the
Mediterranean where the main water masses of the Mediterranean circulation flow between different
basins. Current meter moorings deployed within different subtasks of section B of this project will
provide hydrological data and the substratum for colonisation of benthic species from the water
column.
This task will be performed with a collaboration with the UO of different subtasks of section B that
will use instruments positioned in moorings and deployed in the sea. Strategic sites in the
Mediterranean will be surveyed and the exchange of species between the main basins will be checked
and monitored. A check list of species transported by the main water masses of the Mediterranean
Principal Scientist: Dr. D.Levi (ITPP-CNR,Mazara del Vallo)
Introduction
The interactions/correlation between different components of the ecosystem can be explored where long data series are present for both fish stocks and environmental parameters. Such a problem is more critical for fish stocks than for oceanographic data, for oceanographic data more than for meteorological ones.
Two pathways can be followed to circumvent this problem: to concentrate where fairly long data series exist at all levels (e.g. Adriatic Sea) and/or to rely upon the interpretation of fuzzy logic signals where fisheries data are scanty (e.g. Sicilian Straits). A third possible clue could emerge from the analysis of paleo/old traces of fish stocks fluctuations if the measurements in sediments will be successful.
Biological resources on which to concentrate are: small pelagics, where the influence of fishing has already been ranked low on biomass fluctuations, and clams, which are coastal and sessile, therefore not escaping environmental negative feedback. In the following tasks we present two approaches to the problem of seasonal and interannual fluctuations in fish stocks and their relationship with physical and biochemical parameters characterizing the water column.
Task C.4.1 Fluctuations and trends of small pelagic fish stocks
Responsible: Dr. D.Levi (ITPP-CNR, Mazara del Vallo)
Background
In the Mediterranean long and acceptably reliable fisheries data series are not available but also elsewhere a major problem applies to fisheries data on small pelagics. For the very resources which are most affected by the environment in their fluctuations (at any time scale), catch per unit of effort is a signal of vulnerability rather than an index of abundance.
The development of “quasi-independent from effort” assessment methods (Sequential Population Analysis, SPA) has only partly solved the above problem. In fact, direct (i.e. not based on fisheries data) assessment methods should in principle overcome the problem, but they are still affected by major weak points (e.g. target recognition for echo-surveys; spawners fecundity for egg-larvae surveys,...).
Pending the solution of the above drawbacks, as a matter of fact only one fisheries based historical data set collected by a scientific Institution exists in the whole Mediterranean and it was built up in Italy; its analysis by SPA has so far showed the independence of fluctuations from fishing effort.
Conversely, some decadal or bi-decadal sets of eggs-larvae data have grown in the last two decades either from regular surveys or from fixed stations, often coupled with measurements of environmental factors, just as the data series mentioned under C.1. Finally, in Italy, one bi-decadal echo-survey data series exist.
Scientific Objectives
- to verify the availability and accessibility of the above mentioned time series; to build up a comprehensive data-base with audited field-data from all possible scientific sources in Italy
- to identify seasonal and interannual regularities and anomalies
- to explore their correlations with environmental data series within SINAPSI at sensible space/time scales.
Task C.4.2 The climatic variability of sardine and anchovy fish catch in the Adriatic
Responsible: Dr. N.Cingolani (IRPEM, Ancona)
Background
Anchovies (Engraulis encrasicolus, L.) and sardines (Sardinia pilchardus, Walb.). are among the most important fishery resources of the Adriatic. Anchovy has a wider market, higher prices and in general it is commercially more important than sardine. Although the Adriatic has a surface of about one twentieth of the Mediterranean the Adriatic anchovy fishery yields about 20% of the whole Mediterranean catches of anchovy (Cingolani, et al., 1995) and more than 70% of the Italian catches of anchovy (ISTAT). A similar situation is reported also for sardines.
Since 1975 IRPEM has been collecting systematically catch and effort data regarding the fishery for anchovy and sardine in the Adriatic. Catch data have been collected for nearly every port whereas in the most important ports (Trieste, Chioggia, Porto Garibaldi, Cesenatico, Cattolica, Ancona, S. Benedetto del Tronto e Vieste) also biological samples (a box of fish from the catch) have been collected in order to study the demographic structure of the population in terms of length frequency distribution and (by means of otolith or scale reading) in terms of age distribution of the catches.
This sampling scheme gives a wide covering in time (more than twenty years) and in space because the main fishing area which coincides with the area with the highest abundance lays from Trieste to the Gargano promontory. The collection of these data allowed also to increase the knowledge of the behavior of the fishing fleet and therefore the fishing grounds of each local fleet is now broadly known.
A wide scientific literature on anchovy and sardine in the Adriatic exists (see reference list), the biology of the two species has been studied also in other areas, a good database of fishery data is available, all these facts makes this subject the most appropriate for a deep investigation in the interrelationship between environment and fishery resource. It must not be forgotten that the Adriatic is also a sea with very particular characteristics (low depth, high nutrient inputs etc.) which could facilitate to some degree this kind of investigation.
Scientific objectives
The major scientific objectives of this study are:
- to look for possible interrelationship between the data on biomass abundance and demographic structure of the population (particularly for anchovy) with environmental data (oceanographic, satellite etc.).
- to focus the elaboration in particular on the collapse of the anchovy stock of the Adriatic which took place in 1987.
- to follow in the years subsequent to the crash the recovery of the stock of anchovy comparing this situation (and the present) with the situation of the late seventies early eighties when the highest biomass abundance were recorded.
- to look for possible difference in the environmental influences between anchovy (mostly summer spawner) and sardine (mostly winter spawner) and possible interspecific competition.
Workplan
- identification of the necessary environmental data banks and development of the ad hoc software for data elaboration.
- time series analysis with particular attention to seasonality, interannual variations and spatial distribution.
- possible relationships between the Adriatic and the rest of the Mediterranean basin as far as fluctuation of anchovy and sardine biomasses are concerned.
- investigation on a model which could explain and predict the relationships between environment and anchovy and sardine fishery resources. This part should be developed in collaboration with the team which is involved in historical time series of environmental data (Paschini).
Description of team
Institution Personnel Position Man/month
IRPEM N. Cingolani CTER 2
IRPEM G. Giannetti CTER 2
IRPEM E. Arneri Researcher 2
IRPEM A. Santojanni Ph.D. 12
Financial budget *
Total
1997
45
1998
45
Total
90
*All costs are in Millions of Lire
Task C.4.3 Relationships between spatio/temporal characteristics of pelagic fish system and environment.
Principal scientist: Ing. M. AZZALI (I.R.PE.M.-CNR, Ancona)
Background
The long term data set gathered by acoustic group of I.R.PE.M. is summarized in the following table:
Hystorical data on Adriatic sea (1976-1996)
Available data
Acoustic data set on pelagic fish populations (1976-1996)
Satellite infra-red images (1982-1996)
Dolphins data set (1988-1996)
River flow (Po) (1980-1996)
Data not yet
available but in
course of recovering
from archivies
Meteorological data (wind)
River plume (Po)
Environmental data (CTD)
Data can be divided in three blocks:
1) Spatial/temporal data on pelagic fish populations, acquired in Adriatic using acoustic methodology
since 1976.
2) Satellite data on sea surface temperature of Adriatic collected since 1982. Meteorological and
river flow data, can be recovered from archivies.
3) Spatial/temporal data on dolphins as predators of pelagic fish populations and competitors of man
acquired in Adriatic since 1988.
Scientific objectives
The objectives of project activity are the study of:
1) The relationships between spatio/temporal characteristics and the environmental variables in
the period 1976-1996 (long-term scale).
2) The determinism of these relationships in the period of collapse of the anchovy (around 1987;
small temporal-scale).
Work plan
Complete and order the biological and environmental data-base.
Implement the Geographical Data-Base System developed by I.R.PE.M. since 1985 for processing and cartographic imaging of biological and environmental data.
Assess the relationships between environmental and biological spatial/temporal characteristics in a long-term scale (20 years).
Determine these relationships in the period of collapse of anchovy (1987), through the analysis of fine structures and dynamics of the fish distribution and of the main environmental descriptors.
Description of team:
Institution Personnel Position man/month
I.R.PE.M.-CNR M. Azzali scientist 2
I.R.PE.M.-CNR M. Luna technician 2
I.R.PE.M.-CNR G. Cosimi technician 2
I.R.PE.M.-CNR J.Kalinowski scientist 2
I.R.PE.M.-CNR S. Catacchio technician 2
Financial budget* Total
1997 20
1998 20
Total 40
*All costs are in Millions of lires
TASK C.5. Quantitative assessment of transport processes and biogeochemical cycles in the Northern Adriatic coastal area.
Principal scientist: Dr. Mariangela Ravaioli (IGM-CNR, Bologna)
Introduction
Short term climate changes and human activities strongly influence the behaviour of the continental shelf, in terms of transport of mass and energy, and biogeochemical cycles. A wise policy for the future requires fundamental understanding of how the coastal system operates and responds to changes. Recent advances of the tools available have greatly enhanced our ability to investigate the complex processes in the coastal areas. Furthermore, the pointhas been reached at which substantial new advances require major interdisciplinary efforts that can be formulated based on existing information. Therefore, it is now possible to obtain a new level of quantitative understanding of the processes that dominate the transports, transformations and fates of biologically, chemically and geologically important matter on the coastal area of the Northern Adriatic Sea. Task C.5.1 is designed to provide the quantitative understanding of key biogeochemical processes and anthropogenic influences over short time scales, while Task C.5.2 addresses the study of the response of of planktic communities to the environmental changes, and the knowledge of how the primary signal is recorded in sediments in terms of fluxes.
Task C.5.1 Short time scale variability of key biogeoche!mical processes and anthropogenic influence in the Northern Adriatic coastal area.
Responsible: Dr. M. Ravaioli (IGM-CNR, Bologna)
Background
At present we have substantial knowledge of the basic scheme of water circulation, sediment transport and distribution, pollutant behaviour, sediment-water interactions, and other related processes. In fact, many data have been obtained in the last two decades especially focused on understanding sediment pollution (Frascari et al., 1988), factors controlling eutrophic conditions (Giordani et al., 1987) and therole of sediments in eutrophication processes (Spagnoli and Bergamini, 1997), river inputs (Frignani et al., 1992), sediment accumulation (Frignani et al., 1991), effects of drilling operations (Frascari et al., 1996; Mauri et al., 1996), scavenging processes and particle fluxes (Frignani et al., in preparation). A significant improvement of the research has been the achievement of time-series data (Matteucci and Frascari, 1997) and the tentative formulation of mass budgets (Alvisi et al., 1996) but, despite of this large effort the quantitative behaviour of the system, in terms of fluxes, rates of processes and mass balances, remains poorly known, and modeling of processes is still in early stages. It is especially necessary to examine the present knowledge from a unified point of view and provide a quantitative description of coastal processes that can be the basis for an ecological model. The study area will be the Northern Adriatic Sea, with a special emphasis on the area in front of the Emilia-Romagna. A time scale of a century should be optimal for this study.
A number of key problems should be addressed in this study, through the collection of new data and the reinterpretation of the existing ones:
- evolution of weather on different time scales;
- inputs of both sedimentary and anthropogenic materials from rivers and the atmosphere, and their variability as a function of time and weather conditions;
- transport, distribution, accumulation and export of material in the area;
- primary production, particle sinking through the water column, transformations among solutes, particles and organisms and nutrient regeneration;
- the role of processes that couple the benthic and pelagic zones;
- changes over the last 100 years as recorded in sediments, quality of the sedimentary record, processes of bioturbation and physical mixing;
- resuspension and its role on the transport of sedimentary materials;
- the anthropogenic influence on the coastal area and superimposition of its effects on those of climate.
All the above issues can be related to climate change and its evolution. It is known, for example, that neither the coastal system impact on climatic change nor the climatic change’s influence on the coastal area can be predicted without assessing the potential changes in coastal productivity, sedimentation, transport patterns and ecosystem structure. This is the ultimate purpose of our research.
Scientific Objectives
The main goal of this study will be the assessment of quantitative links among processes which depend on climate or climate-related forcings. Of particular interest will be:
- the reconstruction of the history of sediment delivery by the principal rivers and the atmosphere to the study area, and the role of weather;
- the refinement of the sediment mass budget;
- the establishment of relationship betwen water circulation and sediment transport and sedimentation;
- the separation of the effects of bioturbation and resuspension on sediment mixing;
- the understanding of the coupling between production, sinking of particulate matter and chemical and physical processes in surficial sediments;
- the assessment of the role of sediment as sink and/or source of contaminants and nutrients to the overlying waters;
- the assessment of the variability of the system in terms of magnitude and time scales of processes as related to climate or to antropogenic influences.
- a contribution to the development of an ecologic model for the Northern Adriatic coastal area.
Subtasks
C.5.1a. (Responsible: Dr. M. Ravaioli) Data inventory (weather, river inputs, atmospheric input, sedimentogy, geochemistry, pollution). Archive data and available publications, especially papers not published in major periodicals, will be used.
Sedimentology will be defined on the basis of preexisting data and new experiments. The transport along shelf and across shelf will be defined through the measurement of fluxes and mass budgets. The delivery of fines to the relict sand area will be studied using 210Pb inventories.
C.5.1b. (Responsible: Dr. F. Frascari) Sediment fluxes trough the water column and degradation of sinking particles will be studied using moored sediment traps at selected sites. Concentration-depth profiles of the most important pollutants (metals, nutrients, organic microcontaminants) will be obtained at selected sites. Density, composition, changes and autoecology of benthic communities will be assessed as a function of environmental characteristics. The role of benthos in determining burial rates of biogenic material, pore water chemistry and benthic fluxes will be defined.
C.5.1c. (Responsible: M. Frignani) Sediment chronologies will be obtained using 210Pb, 137Cs, 239,240Pu, and 14C. Short-term ratesof bioturbation will be quantified over one year using radiotracers and luminophores. Other experiments will be carried out in order to understand sediment resuspension processes. The information will be used to assess the quality of the sedimentary record and obtain accurate accumulation rates and chronologies. Fluxes of materials and chemical species across the sediment water interface will be calculated.
Data reinterpretation: the existing information and the new data will be interpreted in such a way to meet the objective of the program, that is quantify fluxes and kinetic constants of processes. A framework which follows the structure of the ecological model ERSEM will be used (Vichi et al., 1998). The problem of scale integration of our findings will taken into consideration.
Workplan
Subtasks Year 1 Year 2
C.5.a =============== ===============
C.5.b =============== ===============
C.5.c =============== ===============
Description of team
Institution Personnel Position Man/Month
IGM-CNR, Bologna M.Ravaioli Scientist 2
M.Frignani Scientist 2
F.Frascari Scientist 2
to be founded fellowship 22
to be founded fellowship 22
L.G. Bellucci Scientist .........2
S. Albertazzi Scientist .........3
F. Alvisi Scientist .........3
D. Sorgente Scientist .........3
M. Marcaccio Scientist .........2
C. Bergamini Scientist .........2
G. Matteucci Scietist .........2
IMGA-CNR, Bologna M. Zavattarelli Scientist .........1
M. Vichi Scientist .........2
MSRC-SUNY (NY) J.K.Cochran Full Professor 1
University of Tolouse M.Gerino Scientist 1
============================
Financial budget* Total
1997 80
1998 70
Total 150
===========================
*All costs are in millions of lire
Task C.5.2 Biological and geochemical cycles in the Adriatic area: fossil and present record
Responsible: Prof. Laurita Boni (Dipartimento di Biologia, Università di Bologna)
Introductions and methodology
The study of the planktic community in both modern and ancient assemblage is of primary importance because they reflect the climatic (and environmental ) variations. In particular the phytoplankton communities are known to rapidly respond to the paleoceanographic and environmental changes. In fact diatoms under conditions of nutrients availability and no silica limiting appear to be the most competitive phytoplankton group originating blooms. Also among calcareous phytoplankton in modern assemblage abrupt blooms of the species Emiliania huxleyi occur and can be easily seen in satellite pictures. However, in the fossil record, diatoms remains are very rarely observed and also the different blooms of E. huxleyi cannot be clearly discerned.
The study of the modern assemblage modifications in the oceans is of primary importance to understand the response of planktic communities to the environmental changes but becomes more important the knowledge of how much of the primary signal is recorded in the sediment. Recently the study of the biogenic fluxes in the water column has become possible through the development of sediment traps or plankton tows. The use of these devices will allow us to monitor biogeochemical fluxes in the Adriatic sea and by means of box core analyses we will analyze their record on the superficial sediments.
In particular we intend to analyze the phyto and zooplankton fluxes and some chemical tracers as alkenones, sterols and hydrocarbons.
As already mentioned, the study of both zooplakton and phytoplankton fluxes (Calcareous, Siliceous and other) compared to the available archive data will also help us to monitorate variations of those group seasonally, while the study of the superficial sediment content will give us the answer about how much of the primary signal is recorded in such layers.
The ubiquitous unicellular marine coccolithophorid E. huxleyi, contains long chain (C37-C39) alkenones, whose unsaturation changes with growth temperature in laboratory cultures. These compounds also occur in contemporary bottom sediments, and they are derived from the phytoplankton living in the photic zone of the overlying water column. Differences in the alkenone unsaturation reported from sediments in different climatic regimes suggest that this feature reflect water temperature of the euphotic zone. The results of analyses on core sediments are expected to reflect the past climate temperature fluctuations.
To further test the influence of changing physical parameters and / or the occurrence of biogeochemical tracers (I.e.Sterols on Dinoflagellates, highly branched isoprenoid hydrocarbons on Diatoms) on marine Plankton and Benthos communities, laboratory cultures will be performed.
Such an approach can help to point the boundary conditions for the origin of climate related variations in sediment composition. The extension of these studies to the sediments would allow us to recognize the amplitude of the primary signal and the burial effect on the composition of the biogenic fraction of the sediments. The hydrocarbons determination allow us to understand the origin of the main sources of organic matter sediments in basin as for instances microalgae and vascular land plants. In recent sediments this method also allow to discriminate possible anthropic contamination.
To improve the interpretation of acquired data sets we need to extend the biogeochemical proxies to a wider time interval. Therefore we plan to concentrate on the stratigraphic record of a critical period in the middle Pliocene (sensu Rio et al., 1994) where oscillation driven by incipient polar ice increase, produced conditions similar to the Holocene ones (e.g. Warnke et al., 1996).
Since 10-15 years a large amount of detailed studies, concerning the identification of marker horizons of past relative sea level changes and the development on the astronomically tuned geologic time scale, provide a valid data set for the comparison between land and marine sequences ranging in the same time interval (Langereis & Hilgen, 1991; Poore & Sloan (eds.), 1996).
Selected middle Pliocene sections (around 3 Ma) of the Apennine foreland basin are available for a paleooceanographic study to test the validity of the methodological approach proposed for the study of the living communities and their biogeochemical signature. This deep water record, characterized by high depositional rates and laminated anoxic layers, shows high preservation of both organic matter and skeletal remains of some planktonic producers. Furthermore the diagenetic modifications of the fossil assemblage appears very low, mainly because the studied successions escaped from a deep burial.
Within the framework of a classical isotope- magneto- and bio-stratigraphy, we plan to apply the other analytical approaches above described. This sedimentary succession appears, in fact, suitable to test the imprint of sterols and highly branched isoprenoid hydrocarbons.
Finally, a time equivalent carbonate platform, has been analyzed in terms of sediment dynamics, and fossil communities. A comparison between the platform productivity and the pelagic planktonic productivity will be used as a proxy of the biological response to the environmental physical changes. This kind of study represents a useful tool to understand the evolution of analogous Holocene carbonate mounds, occurring in the Adriatic Sea.
Workplan
Following this approach we intend to perform plankton tows in selected stations of the Northern Adriatic sea in order to check seasonal fluctuations. In correspondence of these stations we will deploy a box core in order to study the superficial sediment biogenic fraction that will compare with samples of the Apennine marine record.
We plan to perform the following analyses
A) Water column :
-Phytoplankton fluxes
-Zooplankton fluxes
-Alkenones on living coccolithophore
B) superficial sediment
-biogenic fraction analyses sampling every 0.5 cm : calcareous and
siliceous microfossil content
-Hydrocarbon characterization
-Steroles in Dinoflagellates
-C and O Isotopes
-Alkenones
fossil record
- isotope stratigraphy,
- magnetostratigraphy
- microplankton and microbenthos quantitative analysis
- biogeochemical characterization of the organic matter,
- Corg and Ccarb quantitative analysis
- Hydrocarbon characterization
D) Laboratory cultures:
-Recognize surviving strategy when physical and chemical parameters
are changed.
-biochemical study of Dinoflagellates to verify a possible influence of cell age on the composition of the 4-methyl sterol fraction
Universita’ di Ancona Alessandra Negri Scientist (Calcareous Phytopl.)
Cecilia Totti Scientist (Siliceous Phytopl)
To be funded
Università di Bologna Laurita Boni Professor (Dynoflagellates)
Paolo Serrazanetti Professor (Hydrocarbons)
Giampiero Pagliuca Scientist (Sterols)
Otello Cattani Scientist (Biochemistry)
Giovanni Gabbianelli Scientist (Sedimentology)
Rossella Capozzi Scientist (Sedimentology)
Vincenzo Picotti Scientist (Sedimentology)
Simona Giunta Ph.D. student (Alkenones)
IGM/CNR Bologna (Benthic and Planktic Forams)
Annamaria Borsetti Scientist
Lucilla Capotondi Scientist
ETH Zürich Giovanni Muttoni Scientist (Magnetostratigraphy)
Financial budget*
1997 70
1998 70
* all costs in millions of lire
Detailed explanation of costs (in millions of lire)
1997 1998
Consum. Travel Personnel Consum. Travel Personnel
30 10 30 30 10 30
Subproject D
Climate variability of past climate regimes
Coordinator: F. Trincardi (IGM-CNR, Bologna)
Scientific Background
Purpose
The general aim of this subproject is to provide quantitative constrains on short-term climate variability during critical time slices within the last 20,000 years; this interval is characterized by an eustatic sea level rise of about 120 m and by the transition from full glacial to modern interglacial climatic conditions. We plan to work on existing data (or to collect a few new cores at no cost to this project) to integrate work done on key cores that is not yet a multi-proxy work. We plan to refine chronologies and to improve our resolution to a decadal scale in the marine record. Finally, we plan to apply and refine transfer functions to marine data and to provide quantitative estimates of past changes in temperature, salinity and productivity of sea waters.
Background
Climatic modeling is routinely applied on historical records that date back a few decades only (see subprojects A,B,C). This short time interval is long enough to demonstrate that oscillations taking place at annual to subdecadal scales play a key role on climate change. However, the short excursion of these historical records does not allow a full representation of other kinds of short-term variability that may have been at work in the geologic past and may become important in future scenarios.
While the evidence of climatic variability is clearly expressed in a variety of geologic records (both in marine sediments, continental deposits and ice caps) the forcing acting on the climate systems is still largely unknown. In particular, growing geologic evidence prove that significant natural variations affected the atmosphere, the hydrosphere and the cryosphere on time scales of hundreds to thousands of years. Recent studies provide evidence of repeated short-term climatic changes during the last glacial-interglacial cycle. Where chronology is accurate enough, evidence of synchronous variability from many regions of both hemispheres indicates that at least some of these oscillations were global.
Scientific objectives
The objectives of our subproject are twofold: 1) analyze paleo-climatic and paleoenvironmental data sets on the terrestrial biosphere sector to extract seasonal, interannual and decadal time scale fluctuations in the atmospheric climate of the past 200 years; 2) determine if, and under what conditions, short-term environmental and climate changes may be recorded in marine sediments. To achieve the first goal alpine ice cores, tree rings and lake sediments will be analyzed to extract fluctuations in temperature, humidity, atmospheric dust load and vegetation cover. To achieve the second goal we plan to extract several complementary proxy records from the sedimentary archive in the Mediterranean basin. We concentrate on intervals when short-term change plays a critical role in the transition from different climatic modes: the beginning and the end of the Younger Dryas event, the Mid Holocene climatic warming and the late-Holocene (following the Roman optimum and including the Little Ice Age). To achieve this, we need to: 1) define key sites for ultra-high-resolution stratigraphic reconstruction, 2) establish and test cm-scale correlation schemes between sites, 3) develop refined chronologies using multiple dating and calibration techniques, 4) extract quantitative multi-proxy data from sedimentary archives, 5) improve our techniques for multivariate and time-series analyses, 6) extract quantitative measurements of mean past atmospheric and sea-surface temperatures using transfer functions from complementary records.
Choosing key sites for paleoclimatic reconstruction
Within the Mediterranean area investigations in deep-water sedimentary deposits are carried out routinely with conventional piston-coring devices; deep-water sediments, however, provide stratigraphic records that are too condensed, affected by the action of bottom currents and far away from mainland (e.g.: lakes) where other kinds of stratigraphic records are suitable for comparative studies. Heavily-sediment clastic continental margins provide expanded stratigraphic records that contain critical information to enhance paleoceanographic and paleoclimatic reconstruction for the last few hundred thousands of years. Because the stratigraphic architecture on both continental margins and deep-sea basins is complex, complementary stratigraphic records should be extracted from core transects and referred to high-resolution seismic stratigraphic surveys. DGPS positioning techniques should be adopted. This subproject aims at defining representative sites for high-resolution stratigraphic work in both shallow continental margin settings (continental shelves and slope basins) and in deep-sea areas and at establishing correlation between the two.
Establishing cm-scale correlation between sites
We plan to focus on existing stratigraphic data, provided that these are based on very high-resolution stratigraphic schemes referred to reflection-seismic surveys. Because no single core contains the same definition through the entire stratigraphic record, between-site correlations are necessary; these correlations should be based on multiple and independent stratigraphic techniques including both biostratigraphy (for example pollen, foraminifera, ostracods etc.) and physical sediment properties (such as magnetic properties, tephras etc).
Developing refined chronologies
Working on short-term paleoenvironmental signals requires the use of refined chronologies referred to calendar years (Stuvier and Brazunias, 1993; Goszlar et al., 1995; Wolfarth, 1995). Given the time intervals to investigate, AMS 14C is the main dating technique for this project; however, problems are commonly encountered in the use of this dating method: the production of 14C in the atmosphere was not constant but dependent upon astronomical factors. Furthermore, the reservoir age in the ocean changes significantly with latitude and is not constant in time (Bard et al., 1994; Austin et al., 1995). Reservoir increases dramatically from low latitudes towards the poles. The only exception to this trend is the North Atlantic ocean where thermohaline circulation helps renewing bottom waters. For these reasons we plan to 1) transform 14C years into calibrated or calendar years; 2) determine the changes in reservoir that occurred during the past ten thousand years; 3) define the bioturbation bias below which sediment and fauna association are mixed and may result in smoothed trends.
Extracting multi-proxy data from the same set of cores
Because of the complexity of the climate system, a variety of multi-proxy records is necessary to possibly quantify environmental change, define ecosystems response and extract the signature of climate change. Quantitative determinations of changes in sea surface temperature from complementary proxy records will become possible from such a steady.
We plan to provide a refined data base of multi-proxy paleoenvironmental data for each of the three time slices selected. These data will be quantitative and well-defined chronologically, suitable to enter in the world climate data bases, and should provide the basis for future integrated work in the Mediterranean region.
