Panel 1
Patrizia Borrello, Emanuela Spada
Ostreopsis cf. ovata is a potentially toxic benthic benthic microalgae, currently present in most Italian coastal regions with blooms that can give rise to phenomena of human intoxication and toxic effects on benthic marine organisms (states of suffering or mortality). The continuous expansion along the Italian coasts of Ostreopsis cf. ovata, its blooms and the health, environmental and economic problems associated with it, has led to the establishment of a microalga surveillance monitoring program since 2007. This activity is carried out annually in the summer season by the Regional Agencies for the Environment (ARPA). The data provided so far by ARPA, collected and processed by ISPRA have clarified the distribution and trend of blooms at national and regional level. To date, microalgae has been found at least once in the monitoring campaigns carried out so far in 12 of 15 coastal regions. In 2024, Ostreopsis cf. ovata is present in 11 coastal regions or in 135/196 stations (68.9%), while it is absent in all the samples taken along the coasts of Emilia-Romagna, Marche, Molise and Veneto.
The indicator measures the trend of the concentration and distribution of Ostreopsis cf. ovata along the Italian marine-coastal areas and contributes to the environmental assessment of bathing water carried out through the drafting of the "Ban bathing water profiles" (DM 30/3/2010, All. E) and E). It is also associated with the potential toxic and harmful risk of benthic marine biocenosis and humans. Annex C of the DM 30/3/2010 used until the 2018 bathing season shows an alert threshold, corresponding to a concentration in the water column of 10,000 cells. /L (cells per liter), beyond which (emergency threshold) is planned to adopt protection measures. Since the 2019 bathing season, the new alert or emergency reference values for the protection of human health have been adopted in the ISS (ISTISAN Report 14/19) guidelines pursuant to Ministerial Decree 19/4/2018. Ostreopsis ovata is a potentially toxic dinoflagellate detected in Italy since 1989, with very high abundances (flowering), especially in the benthic sector. The blooms can result in cases of suffering or mortality of benthic marine organisms resulting in qualitative deterioration of water. They occur during the summer and autumn season, often with the concomitant presence of mucilaginous reddish-brown films to cover widespread funds and hard substrates and the presence of flocculi suspended in the water column. The conditions that seem to favor development and blooms are: low depth of water, presence of rocky and / or macroalgae substrates, poor hydrodynamics due to the natural morphology of the coast or the presence of artificial brushes and barriers for the containment of coastal erosion, weather-sea conditions of great stability, water temperatures exceeding 25 degrees Celsius related to the climate changes in progress.
Assessing the presence of microalgae, the space-time trend of its proliferation and the potential risk to the marine environment benthic, man and bathing water.
Toxic Algae Directive of the Minister of the Environment (GAB/2006/6741/B01); Directive 2006/7/EC; Legislative Decree no. 152/2006; D.Lgs. 116/2008; DM 30 March 2010; DM 19 April 2018; Directive 2008/56/EC; Legislative Decree no. 190/2010; Agreement RA.MO.GE (France, Principality of Monaco, Italy).
Since 2006, following the Toxic Algae Program Directive of the Minister of the Environment and the Protection of the Territory and the Sea, ISPRA has activated with the coastal ARPA the line of work "Algal flowers of Ostreopsis ovata along the Italian coasts" in order to identify elements for a common national strategy of sampling, analysis, monitoring, surveillance, information, communication and management of the phenomenon "toxic algae". At the same time, the Ministry of Health has prepared guidelines for the "Management of the risk associated with the blooms of Ostreopsis ovata in the Italian coasts" (May 2007). As one of the purposes of Directive 2006/7/EC is to preserve, protect and improve the quality of the environment and to protect human health by integrating Directive 2000/60/EC, as well as in its Italian transposition, activities on Ostreopsis have been useful for environmental assessments. For this purpose, the blooms are to be indicated in the Annex E "Sappaing water profiles" of the Ministerial Decree 30 March 2010 which reports in Article 3 as amended by Ministerial Decree 19 April 2018 (Article 3 paragraph c) the adoption of ISPRA operational protocols in surveillance and monitoring activities and the new reference values set out in the ISS guidelines (ISTISAN 14/19 Report) pursuant to the aforementioned DM 19/4/2018.
In particular, the alert phase provides water column density of 10,000-30,000 cell/L, sufficient hydrodynamicism and unfavorable temperatures at flowering or density of 30,000-100,000 cells. /L and unfavorable weather conditions to the formation of aerosols and splashes; while, in the emergency phase, it involves “Density in the column of water 30,000 cells. /L and weather-sea conditions favorable to the formation of aerosols and splashes of water” or “Density in the water column ?100,000 cell. /L, regardless of the weather conditions.”
The indicator, moreover, has been used for the Initial Assessment pursuant to the Marine Strategy Framework Directive (2008/56/EC received with Legislative Decree no. 190/2010). The RA.MO.GE Agreement, with the GdL GIZC-Ostreopsis ovata, has allowed Italian, French and Monegasque scholars and health authorities since 2010, to discuss national surveillance plans, flowering management methods.
Panel 2
ISPRA Rapporti: 127/2010,148/2011, 173/2012, 188/2013, 211/2014, 232/2015, 253/2016, 275/2017, 298/2018, 325/2019, 336/2020, 357/2021, 379/2022, 396/2023, 405/2024.
Report SNPA 21/2021, Rapporto sugli indicatori di impatto dei cambiamenti climatici.
ISPRA, Quaderni Ricerca Marina n. 5, 2012
Linee guida ISS (Rapporto ISTISAN 14/19)
Climate change and harmful benthic microalgae. Patricia A. Tester, R. Wayne Litaker, Elisa Berdalet. Harmful Algae, Vol, 91, 2020 https://doi.org/10.1016/j.hal.2019.101655 https://www.researchgate.net/publication
Stefano Accoroni, Francesca Neri, Marika Ubaldi, Tiziana Romagnoli, Cecilia Totti, 2024.Trend of Ostreopsis cf.ovata (Dinophyceae) along the Conero Riviera (northern Adriatic Sea) over two decades. Phycologia https://doi.org/10.1080/00318884.2024.2318819
Lack of an environmental reference threshold value.
Quantitative study of effects on benthos. Determination of an environmental threshold concentration value.
Data quality assessment
Coastal ARPA
Used the data of the coastal ARPA provided to ISPRA as part of the activity line: "Algal flowers of Ostreopsis ovata along the Italian coasts" (Dir. Program toxic algae no. GAB/2006/6741/B01) sent in the form of excel reports and tables by e-mail or pec ISPRA and uploaded to SINTAI with specific format.
Coastal regions
2010-2024
Indicator assessment
Abundance is expressed as cell. /L, cell./g fw or cell./cm2 respectively for samples taken in water columns, on macroalgae or on hard substrate. All the matrices contribute to indicating the presence of Ostreopsis ovata in the collection station, considering as positivity the presence of Ostreopsis at least once in the monitoring campaign. The concentration in cell. /L is compared with the new health reference values set out in the ISS guidelines (ISTISAN Report 14/19) pursuant to DM 19/4/2018. In particular, the emergency phase is reached with a density of 30,000 cell/L and weather-sea conditions favorable to the formation of aerosols and splashes of water. The space-time comparison of abundances shows the trend of blooms at regional, interregional and national level in the reference year and in previous years. In addition, the presence of Ostreopsis also expressed as a percentage of positive sites is reported at regional and national level in the current year and during the observation period.
The 2024 monitoring, carried out in 15 coastal regions, made it possible to assess the space-time trend of the indicator per single sampling point. In 7 regions there was an excess of 30,000 cell/l and in 5 of these also the exceedance of 100,000 cells/L (Table 1). The first is an alert value and the second an emergency value, according to the guidelines of the Ministry of Health. In 2024, no episodes of suffering were observed against marine organisms but only the presence of foam and floccules in the water column (Lazio) and patina on the substrates (Friuli-Venezia Giulia), during the peak of flowering. The percentage of positive sites, which describes the spatial distribution of the indicator, remains almost unchanged: 68.9% in 2024 and 68.7% in 2023. It is not currently possible to assess the state from an environmental point of view only on the basis of the presence of the algae, as there is no environmental reference value that represents a risk to the health of marine-bentonic organisms. The Chernoff icon in this case is assigned only on presence/absence.
A negative trend is attributed since the trend over the 15 years considered does not show a clear reversal of the trend. In fact, since 2010 there has been an increase over time, of more than 21 percentage points, of sites with the presence of Ostreopsis ovata (2010: 48.3%, 2024: 68.9%) (Figure 2 and Table 3). There are also minimal variations in the number of sites with the presence of microalgae in the period 2010-2015 and greater between 2016 and 2024. The maximum value, equal to 71%, was recorded in 2020.
Data
Figure 1: Presence of Ostreopsis cf. ovated along the Italian coasts (2024)
ISPRA processing on data from coastal ARPA
Table 1: Presence of Ostreopsis cf. ovated along the Italian coasts (2024)
ISPRA processing on data from coastal ARPA
Table 2: Presence and abundance of Ostreopsis ovata along the Italian coasts (2024)
ISPRA processing on data from coastal ARPA
Le celle vuote indicano assenza di monitoraggio nella matrice considerata
Table 3: Percentage of sites with presence of Ostreopsis cf. ovata at regional level (2010-2024)
ISPRA processing on coastal ARPA data
* monitoraggio non effettuato
Figure 2: Percentage of sites with presence of Ostreopsis cf. ovata 2010-2024
ISPRA processing on coastal ARPA data
In 2024, the monitoring of the potentially toxic benthical benthic microalgae Ostreopsis cf. ovata was carried out along the coasts of the 15 coastal regions (Table 1 and Figure 1). The surveys were carried out by the Regional Agencies for the Environment (ARPA) both for the purposes of the control of water intended for bathing, in compliance with current legislation (DM 30/3/2010, DM 19 April 2018 and Legislative Decree 116/08 and ss.mm.ii), and in the context of ARPA/Region projects, or as activities related to the monitoring of potentially toxic species in the waters for molluscs).
196 sampling stations with hydromorphological characteristics suitable for the development of microalgae (presence of macroalgae, rocky substrates, shallow waters and moderate hydrodynamics, natural reefs and breakwater barriers or brushes) or have recorded microalgae presence and/or blooms in the previous years. The monitoring was generally carried out in the period June-September 2024, anticipated in May in Emilia-Romagna and Molise and postponed in some cases in October (Marche and Veneto). The frequency of fortnightly or monthly sampling has been intensified in cases of exceeding the reference values (30,000 cells/l, 100,000 cells/l), as indicated in the contingency phases described in the surveillance plans respectively of the Guidelines of the Ministry of Health contained in DM 30/3/2010 and DM 19/4/2018 and in the ISTISAN Report 14/19.
Water and macroalgae samples were taken, according to shared methodologies. The chemical-physical parameters of the water were also detected and recorded on a special field card, information on the sampling site, any signs of manifest microalgae flowering or states of suffering at the expense of marine organisms (rice, mussels, starfish, fish, macroalgae, etc.).
In 2024 Ostreopsis cf. ovata was found in 11 coastal regions, while it was absent in all the samples taken along the coasts of Veneto, Emilia-Romagna, Marche and Molise (Table 2) and is present at least once in 135/196 stations (68.9%), considering all types of sampled matrices (Table 1 and Figure 1). This means that the sites where the presence of the microalgae is detected being "at potential risk of toxic algal proliferation" are to be reported in the environmental profile of bathing water to be monitored through monitoring (DM 30/3/2010 and 19/4/2018). In addition, the health reference value of an alert of 30,000 cell/l has been exceeded at least once in 23 monitoring sites (calculation carried out only on the water matrix, Figure 1) and the emergency health value of 100,000 cell/L has been exceeded at least once in 8 sites (Abruzzo 1, Calabria 1, Puglia 2, Sicily 3, Tuscany 1). The first surveys (at low concentrations) are found in June in Basilicata, Calabria, Campania, Lazio, Liguria, Puglia, Sardinia and Sicily, while the highest abundances above 30,000 cell / L are distributed between June and September in Abruzzo, Calabria, Friuli-Venezia Giulia, Lazio, Puglia, Sicily and Tuscany. In particular, in the last three regions mentioned, there was both an excess of 30,000 cells/l and the overcoming of 100,000 cells/L. The maximum concentration value was 1,500,266 cells. /L found at a single site in Calabria. The two hot-spot sites, Hotel Riva del Sole (Apulia) and Passetto acensore (Marche), which every year had high and recurring abundances with values greater than 30,000 cell/L, in 2024 showed an opposite trend as usual, with concentrations ranging from 0 to a maximum of 4,473 cell/L in the “Hotel Riva del Sole” station and even abundances equal to 0 cell/L throughout the period of “Passevery”. This reversal of the trend will be investigated and confirmed in the next monitoring cycles.
In addition, based on data collected over previous years, the duration of flowering varies from a few days to 7-10 days but depending, however, on the environmental conditions that favor and maintain it.