Descrizione 1
Patrizia Borrello, Emanuela Spada
Ostreopsis cf. ovata is a potentially toxic benthic microalga, currently present in most Italian coastal regions with blooms that can lead to human intoxication phenomena and toxic effects on benthic marine organisms (states of distress or mortality). The continuous expansion along the Italian coasts of Ostreopsis cf. ovata, of its blooms and the associated health, environmental and economic issues, has led to the establishment of a monitoring surveillance program of the microalga starting from 2007. This activity is carried out annually in the summer season by the Regional Environmental Agencies (ARPA). The data so far provided by the ARPA, collected and processed by ISPRA, have clarified the distribution and trend of blooms at national and regional level. To date, the microalga has been detected at least once in the monitoring campaigns carried out so far in 12 out of 15 coastal regions. In 2023, Ostreopsis cf. ovata is present in 12 coastal regions, that is in 145/221 stations (68.7%), while it is absent in all samples taken along the coasts of Emilia-Romagna, 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 waters carried out through the drafting of the "Bathing water profiles" (DM 30/3/2010, Annex E). It is also associable with the potential toxic and harmful risk on benthic marine biocoenoses and on humans. Annex C of DM 30/3/2010 used until the 2018 bathing season reports an alert threshold, corresponding to a concentration in the water column equal to 10,000 cells/L (cells per liter), beyond which (emergency threshold) the adoption of protection measures is foreseen. From the 2019 bathing season, new reference values for alert or emergency have been adopted for the protection of human health reported in the ISS guidelines (ISTISAN Report 14/19) pursuant to DM 19/4/2018. Ostreopsis ovata is a potentially toxic dinoflagellate detected in Italy starting from 1989, with very high abundances (blooms), especially in the benthic compartment. The blooms can cause cases of suffering or mortality of benthic marine organisms with consequent qualitative deterioration of the water. They occur during the summer and autumn season, often with the simultaneous presence of brown-reddish mucilaginous films extensively covering bottoms and hard substrates and presence of floccules suspended in the water column. The conditions that seem to favor the development and blooms are: low water depth, presence of rocky substrates and/or macroalgae, poor hydrodynamics due to the natural morphology of the coast or the presence of groynes and artificial barriers for the containment of coastal erosion, highly stable weather-marine conditions, water temperatures above 25 °C, relatable to the ongoing climate changes.
To assess the presence of the microalga, the spatial-temporal trend of its proliferation and the potential risk to the benthic marine environment, to humans and to bathing waters.
Directive Toxic Algae Program of the Minister of the Environment (GAB/2006/6741/B01); Directive 2006/7/EC; Legislative Decree 152/2006; Legislative Decree 116/2008; DM 30 March 2010; DM 19 April 2018; Directive 2008/56/EC; Legislative Decree 190/2010; RA.MO.GE Agreement (France, Principality of Monaco, Italy).
Since 2006, following the Directive Toxic Algae Program of the Minister of the Environment and Protection of Land and Sea, ISPRA has activated with the coastal ARPAs the work line "Blooms 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 “toxic algae” phenomenon. At the same time, the Ministry of Health prepared the guidelines for the "Risk management associated with the blooms of Ostreopsis ovata along the Italian coasts" (May 2007). Since 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 integrating Directive 2000/60/EC, as well as in its Italian transposition, the activities on Ostreopsis have been useful for environmental assessments. To this end, blooms are to be indicated in Annex E "Bathing water profiles" of DM 30 March 2010 which reports in art. 3 as amended by DM 19 April 2018 (art. 3 paragraph c) the adoption of ISPRA operational protocols in surveillance and monitoring activities and the new reference values reported in the ISS guidelines (ISTISAN Report 14/19) pursuant to the aforementioned DM 19/4/2018.
In particular, the alert phase provides for densities in the water column of 10,000–30,000 cells/L, sufficient hydrodynamics and temperatures unfavorable to the bloom or densities of 30,000–100,000 cells/L and weather conditions unfavorable to the formation of aerosol and spray; while, the emergency phase involves "Density in the water column >30,000 cells/L and weather-marine conditions favorable to the formation of aerosol and water sprays" or "Density in the water column >100,000 cells/L, regardless of weather-climatic conditions".
The indicator is also used for the Initial Assessment pursuant to the Marine Strategy Framework Directive (2008/56/EC transposed with Legislative Decree 190/2010). The RA.MO.GE Agreement, with the GIZC-Ostreopsis ovata working group, has allowed since 2010 Italian, French and Monegasque scholars and health authorities to compare national surveillance plans, bloom management methods.
Descrizione 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.
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.
Qualificazione dati
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
2010-2023
Qualificazione indicatore
The abundances are expressed as cells/L, cells/g fw or cells/cm² respectively for samples taken in the water column, on macroalgae or on hard substrate. All matrices contribute to indicate the presence data of Ostreopsis ovata in the sampling station, considering as positivity the presence of Ostreopsis at least once in the monitoring campaign. The concentration in cells/L is compared with the new health reference values reported in the ISS guidelines (ISTISAN Report 14/19) pursuant to DM 19/4/2018. In particular, the emergency phase is reached with density >30,000 cells/L and weather-marine conditions favorable to the formation of aerosol and water spray. The spatial-temporal comparison of abundances shows the trend of blooms at regional, interregional and national level in the reference year and in previous years. Furthermore, the presence of Ostreopsis expressed also as a percentage of positive sites is reported at regional and national level in the current year and in the observation period.
The 2023 monitoring, carried out in 15 coastal regions, made it possible to assess the spatial-temporal trend of the indicator for each sampling point. In 6 regions the 30,000 cells/l threshold was exceeded and in three of these also the 100,000 cells/L threshold. The first is an alert value and the second an emergency value, based on the Ministry of Health guidelines. In 2023, no suffering episodes were observed in marine organisms but only sporadic presence of foam in the water, reddish films covering the rocks (Sardinia), presence of floccules in the water column (Lazio) and a mucilaginous net present on macroalgae in Friuli-Venezia Giulia during the bloom peak. In 2023, there is an increase in sites with presence of the microalga 145 sites (about 69%) compared to 134 sites (66%) in 2022, which describe the spatial distribution of the indicator. It is not currently possible to assess the environmental status solely based on the presence of the alga, since an environmental reference value representing a risk to the health of benthic marine organisms is lacking. The Chernoff icon in this case is assigned only based on presence/absence.
A negative trend is attributed because the trend in the 14 years considered does not show a clear reversal. In fact, since 2010, there has been an increase over time, of about 21 percentage points, in sites with presence of Ostreopsis ovata (2010: 48.3%, 2023: 68.7%) (Figure 2 and Table 3). Moreover, minimal variations are observed in the number of sites with presence of the microalga in the period 2010–2015 and more significant ones between 2016 and 2023. The maximum value, equal to 71%, was recorded in 2020.
Dati
Figure 1: Presence of Ostreopsis cf. ovated along the Italian coasts (2023)
ISPRA processing on data from coastal ARPA
Table 1: Presence of Ostreopsis cf. ovated along the Italian coasts (2023)
ISPRA processing on data from coastal ARPA
empty cells indicate no monitoring
Table 2: Abundance of Ostreopsis cf. ovated along the Italian coasts 2023
ISPRA processing on data from coastal ARPA
empty cells indicate no monitoring
Figure 2: Percentage of sites with Ostreopsis ovata 2010-2023
ISPRA Processing
Table 3: Percentages of sites with presence of Ostreopsis cf. ovata at regional level (2010-2023)
ISPRA Processing
*monitoring not carried out
In 2023, monitoring activities of the potentially toxic benthic microalga Ostreopsis cf. ovata were carried out along the coasts of the 15 coastal regions (Table 1 and Figure 1). The investigations were carried out by the Regional Environmental Agencies (ARPA) both for the purposes of bathing water control activities, in compliance with the current legislation (DM 30/3/2010, DM 19 April 2018 and Legislative Decree 116/08 and subsequent amendments), and as part of ARPA/Region projects, or as activities included in the monitoring of potentially toxic species in waters intended for shellfish farming (Friuli-Venezia Giulia).
211 sampling stations were identified and monitored with hydromorphological characteristics suitable for the development of the microalga (presence of macroalgae, rocky substrates, shallow waters and moderate hydrodynamics, natural cliffs and breakwaters or groynes) or which in previous years recorded presence and/or blooms of the microalga. Monitoring was generally carried out from June to September 2023, anticipated to May in Molise and postponed in some cases to October (Marche and Veneto). The frequency of biweekly or monthly sampling was intensified in cases of exceeding reference values (30,000 cells/l, 100,000 cells/l), as indicated in the emergency phases described in the surveillance plans respectively of the Ministry of Health Guidelines 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. Furthermore, chemical-physical parameters of the water were recorded on a special field sheet, information on the sampling site, any signs of manifest microalgal bloom or states of distress affecting marine organisms (sea urchins, mussels, starfish, fish, macroalgae, etc.) was noted.
In 2023 Ostreopsis cf. ovata was found in 12 coastal regions, while it was absent in all samples taken along the coasts of Veneto, Emilia-Romagna and Molise (Table 2 available in the Environmental Indicators Database) and is present at least once in 145/211 stations (68.7%), considering all types of sampled matrices (Table 1 and Figure 1). This means that the sites where the presence of the microalga is detected being "at potential risk of toxic algal proliferation" must be reported in the environmental profile of bathing waters to be monitored (DM 30/3/2010 and 19/4/2018). Moreover, the health reference alert value of 30,000 cells/l was exceeded at least once in 14 monitoring sites (calculation made only on the water matrix, Figure 1) and the health emergency value of 100,000 cells/L was exceeded at least once in 5 sites (Lazio no. 1, Puglia no. 3 and Sicily no. 1). The first detections (at low concentrations) are recorded in June in Campania, Calabria, Lazio, Liguria, Sardinia and Sicily, while the highest abundances above 30,000 cells/L are distributed between June and September in Abruzzo, Friuli-Venezia Giulia, Liguria, Lazio, Puglia and Sicily. In particular, in the latter three regions mentioned, both the 30,000 cells/L threshold and the 100,000 cells/L threshold were exceeded. The maximum concentration value was equal to 220,110 cells/L found in a single site in Puglia.
Moreover, based on the data collected in previous years, the duration of the bloom varies from a few days up to 7–10 days but depends, in any case, on the environmental conditions that favor and maintain it.