Coordinator: Dr. Nadia Pinardi
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- Bu səhifədəki naviqasiya:
- Task C.3 Benthic ecosystem evolution and climate changes Principal scientist
- Task C.3.1 Phytobenthic ecosystems Principal scientist: L. Mazzella (SZ, Napoli)
- -------------------------------- Management
- Institution Personnel Position
| *All costs are in Millions of Lire Detailed explanation of costs 1997 1998 Consum. Travel Personnel Tot. Consum. Travel Personnel Tot. Unit 3 20 5 20 45 20 5 20 45 Task C.3 Benthic ecosystem evolution and climate changes Principal scientist: Dr. L. Mazzella (SZN, Napoli) Background Benthic organisms are characterized by a higher capability to store energy during their life span as compared to planctonic communities. Consequently, the temporal evolution of the ecosystems is strongly influenced by the biological properties of their "structural" species. A great diversity exists in the structure and function of benthic communities, which respond to environmental changes at different time-scales. For these reasons, relationships between abiotic and biotic descriptors have to be tested according to the biological functions of the species taken into account, and, at higher level, to the functional mechanisms of the ecosystem. Space and time series data analysis, performed in the framework of the EC- COST 647 project on coastal benthic ecology, showed the influence of climatic factors on long-term patterns on benthic ecosystems at various spatial scale, and indicated the importance of long-term time series studies. (Keegan 1991). Signals of previous events can be detected in the life history traits of benthic organisms, and they could be tracers of environmental variability both over a short and a long temporal scale. In this particular framework both phytobenthic, in particular seagrasses, and zoobenthic ecosystems constitute the most suitable subject of study. Task C.3.1 Phytobenthic ecosystems Principal scientist: L. Mazzella (SZ, Napoli) Vegetated benthic ecosystems in the Mediterranean Sea, such as seagrass beds or some algal meadows, play a key role in the dynamics of the littoral area of the basin. They highly contribute to the productivity of coastal waters and provide a structurally diverse habitat supporting rich communities of algae, invertebrates and vertebrates (Mazzella et al., 1992). Seagrass meadows in particular, due to the multifunctional role exerted in all tropical and temperate waters, have been mentioned in the UNCED Action paper (Agenda 21) as ecosystems to be given the highest priority for protection. Seagrass beds are complex but fragile ecosystems, being generally structured by one species, as in the case of the endemic Posidonia oceanica, or two species as Cymodocea nodosa and Zostera noltii, which form mixed stands. These Mediterranean seagrass systems represent different stages of a succession in which P. Oceanica can be identified as "climax". Biological issues of the plant, such as growth and reproduction mode, strongly influence the colonization patterns, stability and resilience of the systems. Regression of P. Oceanica beds, widespread all over the basin, is in strong relationships to both environmental changes and anthropogenic influences. Competition with more tolerant seagrass species or with algae, which have a developed frond canopy and form vegetated stands, is in this framework. In particular recently introduced species, such as Caulerpa taxifolia, are successfully colonizing Mediterranean coastal areas, yet it is unknown to which extent this phenomenon is in relation to some climatic changes. Seagrasses, as clone plants, exhibit biological issues in the rhizome elongation and leaf production, which represent chronological signals, as they do in higher plants. These issues provide a powerful information in detecting variability of growth and production over a relatively long time-scale (decades). The relatively simple plant architecture, with the reiterative modules (rhizomes, roots and shoots), ensures a close relationship between rhizome elongation and leaf production. The insertion points of leaves in the rhizomes are identifiable by scars after leaf abscission or, as in P. Oceanica, by leaf sheaths which remains on the rhizomes according to seasonal patterns. Methods which exploit such plant properties (lepidochronology or plastochrone interval) will allow us to detect interannual and decadal variability in production yields of these ecosystems (Pergent et al., 1991; Duarte et al., 1994). This property is lacking in algal systems, where classical methods can be used to monitor temporal and spatial evolution of their stands. By studying P. Oceanica, C. nodosa and C. taxifolia we examine systems which possess different "memory", with P. Oceanica representing the long living system and showing the lowest resilience to anthropogenic disturbances. Scientific objectives Benthic ecosystems structured by macrophytes (seagrasses and macroalgae) produce, store and export energy to adjacent habitats, thus having an influence on both close benthic systems and the above water column, and being very distinct from those structured by invertebrates which depend on alloctonous energy. In this respect, the role of seagrass systems is poorly known. Growing effort has been given in quantifying their annual productivity and growth dynamics; this studies have been conducted in several coastal areas (Buia et al., 1992; Perez & Romero, 1994). However, their actual importance in the Mediterranean basin is extrapolated from local studies. Yet the seagrass wide distribution makes them playing a pivotal role in the whole basin. The main problem remains to understand variations in their production yields obtained in different years and to relate these to climatic changes. Again, many studies have been locally performed and the importance of local factors over large-scale environmental changes has hardly been assessed (Alcoverro, 1995). Due to the wide distribution of seagrasses along coastal waters, the main aim of this project will be to estimate seagrass production along the Italian coasts and to assess the interannual variability in relation to climatic changes. Although light is considered to be the main factor regulating their distribution pattern, recent works are presently highlighting the role of temperature in influencing seasonal patterns of production of these species (Zupo et al., in press). Calibration methods are needed to relate interannual variations in production of these systems with environmental parameters (mainly irradiance and temperature). The aim is to provide realistic estimation of the contribution of these systems to the carbon budget of the basin and to obtain a "map" of the production of these systems for some areas, where a mapping of seagrass bed expansion already exists. The second fundamental question is in which extent macrophytes exert the role of structural species by increasing the diversity of coastal benthos and how the diversity of such complex ecosystems is influenced by climatic changes. Previous studies indicated the role of plant architecture and standing crop, and habitat complexity in influencing the structure of associated communities and the food webs established in the ecosystems (Mazzella et al., 1989; Mazzella et al., 1992). This second aim will be performed by relating, for different years, plant architecture and biomass of the two seagrasses to species richness and abundance of their associated communities. Species composition and structure of the algal and animal communities associated to seagrass systems will be compared to those associated to algal canopy forming species, such as Caulerpa taxifolia. For this macroalga the structure and abundance of associated communities are unknown. Finally it is worth investigating to which extent the success of the establisment of C. taxifolia, newly introduced in the Mediterranean, is in relation to some climatic changes over a long temporal scale. Subtasks C3.1a Annual estimation of production yields of seagrass beds will be achieved by detecting chronological signals in seagrass leaf scales, and by evaluating rhizome and leaf production in plants of different age. In P. Oceanica this will be performed with two methods: a) lepidochronology, which is referred to dendrochronology of terrestrial plants; b) the plastochron interval (time interval in producing new leaves). The second method will be used for C. nodosa. One sampling campaign is needed for Posidonia beds, while two seasonal samplings are essential for C. nodosa. Samples will be collected by scuba diving. Different meadows of the Italian coasts will be considered (2 sites along the Northern Tyrrhenean coasts, 2 sites along the Southern Tyrrhenean, one along the Sicilian coasts and one in Adriatic Sea). Yearly growth and production will be related to environmental parameter changes. Temperature and irradiance data are provided by the task B." and the data archiving activity of the project; C3.1b Spatial and temporal evolution of Caulerpa taxifolia stands will be assessed in relation to the pioneer introduction in the Messina Strait and along the Elba Island, where previous investigations on this species have been conducted. The production of stands will be estimated and related to the main regulating abiotic factors. Seasonal samplings (4) will be performed for this purpose; C3.1c Seasonal fluctuations in rhizome growth and primary production of seagrasses in different years will be related to the variability of environmetal parameters (mainly irradiance and temperature), in those areas where time-series studies are available. The right time-scale in relating variability in primary production and environmental changes should be identified; C3.1d The "structural" role of seagrass meadows will be assessed by identifying temporal (seasonal and annual) and spatial variations in the structure of associated algal and invertebrate communities (e.g. Polychaetes, Crustaceans), in relation to the meadow physiognomy. Carbon in the plants, epiphytes and invertebrate communities will also be evaluated in order to identify the carbon stocks and fluxes in the ecosystems. This section will be performed only in sites where annual data series are already available (e.g. Ischia, Gulf of Naples); C3.1e Community structure and abundance of invertebrates associated to Caulerpa in relation to the spatial variability of stands will be identified. Also this section will be developed seasonally in one site (Sicily); C3.1f Methods for obtaining maps of production of seagrasses at landscape scale will be applied and elaborated. Workplan
Management Budget requirements include personnel costs, consumable and travel expenses and in less extent equipment. The latter is mainly devoted to a microtome which is essential for determinations of leaf section dimensions for lepidochronological investigations, in plant samples where simple methods cannot be used. This will be used by all working groups. Other equipment is needed for underwater samplings (i.e. underwater vehicles) e some personal computers for the different participants. Consumable expenses mainly concern sampling devices and software packages. The personnel requested consists of two graduate students, one be involved in phytobenthos (samplings and production estimation) and one in zoobenthos (fauna collection and identification). Travel expenses will mainly needed for group meetings.
*All costs are in Millions of Lire Detailed explanation of costs: 1997 1998 Consum. Travel Personnel Tot. Consum. Travel Personnel Tot. 66 54 54 172 55 42 54 151 Description of team: (For each team, only the name of the principal investigator is indicated)
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