Attilio Rinaldi

Eutrophication, structure and dynamics of a marine coastal system: results of ten-year monitoring along the Emilia-Romagna coast (Northwest Adriatic Sea)

The process of eutrophication, which has been in progress for some two decades in the coastal area of the Northwest Adriatic Sea, shows mainly cyclic-seasonal features. In winter and spring large blooms of diatoms usually occur determining the so-called “dirty waters”, while in summer blooms of dinoflagellates cause “red tides”. Low salinity and high nutrient loads from the River Po and most minor rivers favour the production of these blooms. Recurrent episodes of anoxia in bottom waters cause fish kills and other nuisances that impair fisheries. Algal blooms over the years, and two episodes of mucilage formation during the summers of 1988 and 1989 have become a serious menace to the regional tourist industry.

Mucilages in Italian seas: the Adriatic and Tyrrhenian Seas, 1988–1991

Abstract Mucilage events, i.e. the accumulation of a gelatinous material at and below the water surface during summer months, have been known to occur at irregular intervals in the Northern Adriatic Sea for over 200 years, but events of the severity of those of 1872 and 1905 were less noted later in this century. The phenomenon reappeared in 1988 and in the years that followed. In 1991 it was also noted in the Tyrrhenian Sea. Our studies cover the events of 1988–1991 in the Northwest Adriatic and some aspects of the Tyrrhenian Sea. The results presented in this paper provide additional insight into the problem. In general, it can be stated that while we have a fair understanding of the phenomenological and dynamic aspects, and of the environmental consequences of the events, we know little about the causal factors which trigger and maintain the process.

Statistical inferences about the mucilage events in the Adriatic Sea, with special reference to recurrence patterns and claimed relationship to sun activity cycles

Abstract The secular hazard rate of mucilage events in the Northern Adriatic Sea appears to have remained constant over the last 120 years. The recurrence pattern can be described by either the exponential or the more general Weibull distribution model. There is a 50% probability that the next arrival of a mucilage event lies within a time period of 4–5 years, and a 90% probability for a mucilage event to return within 13–14 years or less. However, most events will be of local importance only and less severe than the 1988/1991 events. No statistically significant relationship between mucilage events and the 11-year sun activity cycles could be established. Increasing eutrophication and pollution do not appear to have a direct bearing on mucilage recurrence.

Eutrophication in the Emilia‐Romagna Coastal Waters in 1984–1985

Due to their geomorphic and hydrologic characteristics and because of the type and quantity of material carried down from inland regions, Emilia-Romagna’s coastal waters are subject to periodic and intense eutrophication. Over the last ten years this phenomenon has appeared in all of its by now well-known manifestations-abnormal water color, unpleasant smell, and, when the algae bloom in summer or autumn, a more or less extensive oxygen deficiency. This latter will depend on the extent of the bloom, the amount of the algae biomass, and the weather conditions (calm sea, water stratification, static hydrodynamic situation). As a general rule, eutrophication begins after rain. If such rains are heavy and widespread, they can increase the flow of the river Po and other coastal rivers, thus draining quantities of nutrients into the sea which can then set off and support algal bloom. If there are no high seas, the next phase involves a considerable increase in the concentration of the algal biomass. In fact, if we express this in terms of chlorophyll a , this can reach levels of 50-100 p g h . Under these circumstances, the water is cloudy and its color will take on a particular tone (red, brown, green, etc.) depending on the types of phytoplankton causing the bloom. Once the development stage is over, but especially once the supply of nutrients has been used up, the algae biomass dies and tends to deposit on the bottom where the mineralizing process carried out by bacteria requires very large amounts of oxygen dissolved in the water (FIG. 1). If this situation coincides with a calm sea, it can produce an oxygen deficiency that can be more or less extensive and cause the all too-well-known phenomenon of benthonic organism die-offs (bottom-feeding fish, molluscs, coelenterates, annelids, etc.) From the point of view of distribution, that is, the incidence of this phenomenon along the Emilia-Romagna coast, we can divide the entire section of this coast into three sub-areas (FIGS. 2 and 3). The first and most northerly includes the section between Goro and outer breakwaters of the port canal at Ravenna. This sector is most susceptible to eutrophication since it is not only directly affected by the water from the river Po (Po di Goro and Po della Gnocca-25 percent of the entire flow rate of the river), but it also receives water from the Burana-Volano, the Ferrarese Idrovia, from the Valli di Comacchio through tidal effect, and from the Reno, the Destra Reno and the Lamone rivers. Apart from the question of the nutrient input during the summer-autumn pe-

Mucilaginous masses in the Adriatic sea in the summer of 1989

Abstract This paper reports on one of the most recent episodes of mucilage formation in the central–northern part of the Adriatic coast in July–August 1989. The stretch of coast examined goes from the estuary of the River Po to the border of the Marche–Abruzzo coast (Italy). The possible events (nutrients, N/P ratio, particular climatic conditions) that cause the formation of the mucilage masses were examined and are discussed here. Furthermore, the oxygenation state of the water on the surface and on the bottom as well as the possible effects on molluscs were also examined. The field results indicated that no anoxia phenomena were found in bottom waters caused by mucilages, and that mollusc death was probably due to mechanical reasons. Finally the places where the mucillages formed and their subsequent movements are described.

Eutrophy and dystrophy in the Goro Lagoon (Italy)

The eutrophication of the lagoon systems in the coastal areas of the Northwest Adriatic Sea has caused serious damage not only to the ecosystem but also to the economy based on the tourist and fishing industries. This work presents the results of a study on the Goro Cove carried out during 1987-1988. An analysis of the data shows that the high trophic level and the consequent dystrophies (anoxia of the waters) are caused by the large amount of nutrients carried into the lagoon by the Po and Burana-Volano rivers

Contribution of Richard A. Vollenweider toward understanding eutrophication of the coastal Adriatic Sea

The main scope of the work of R. A. Vollenweider in Italy, that is to say his principal scientific merit, was to critically examine the cause-effect relationships related to the manifestations of the eutrophication phenomenon. These relationships were observed in the NW Adriatic Sea over more than 20 years, along the Emilia Romagna coast, an area strongly affected by Po river inputs, the principal Italian river (Vollenweider et al., 1992). In particular, he stressed the need to examine the integrated system, and to consider both scientific and socio-economic issues as interrelated. Accordingly, coastal waters and their catchment areas with related nutrient loads represent the total system, of which the natural, anthropogenic and socio-economic components are the respective subsystems. In more practical terms, he suggested nutrient load assessment based on the different sources of N and P, to prepare an inventory of all these sources according to types and quantity released, and in terms of pathways of transfer and input-output fluxes. In this way it was finally possible to reach a first realistic evaluation of N and P mass balance across the various productive compartments.

Time series analysis of oceanological parameters measured at a fixed station

Daily measurements of temperature, salinity, chlorophyll, oxygen, mineral nitrogen and phosphorus, among others, were made in 1986-1987 at a fixed station located 3 km offshore from Cesenatico. Data were analyzed using statistical and time series techniques. Some of the salient features of the short-term variability (maximum period 60 days) of these time series are discussed and compared with those found in a similar study made during 1979-1980 at the same station. Besides variations in nutrient supply from rivers, meteorological events such as wind and pressure variations are the most likely forcing factors involved in causing the time series patterns observed.

Eutrophication along the Emilia-Romagna coast: application of statistical analyses to 1984–1989 monitoring data

Eutrophication of the Northern Adriatic is a long-standing problem and in 1988 and 1989 a pale brown mucilage appeared in the sea, formed from extracellular polysaccharides produced by algae growing in the water. Data from the years 1984-89 from the extensive water quality data set collected by the M.N. Daphne was examined using the AARDVARK statistical software. The objective was to see if any features distinguished the years 1988 and 1989, in which mucilage was observed, from other years and whether any trends in water quality variables could be detected (...)