Descrizione 1
Paolo Tomassetti, Tommaso Petochi
The indicator provides an estimate of the input and removal of nitrogen and phosphorus in coastal environments where aquaculture activities take place. Specifically, fish farming contributes to the release of these nutrients, while mussel farming facilitates their removal.
The balance between the nutrient input from farmed fish and the nutrient removal by bivalve shellfish allows for a regional-level assessment of the net quantitative contribution of aquaculture to trophic processes along the Italian coastline.
At the national level, in 2020, estimates of the nitrogen and phosphorus balance from intensive fish farming and mussel farming showed a reduction compared to 2019. This decrease was due to:
- A decline in nutrient input resulting from lower fish production
-
A decrease in nutrient removal due to the reduction in mussel production
At the regional level, in Veneto, Emilia-Romagna, Abruzzo, Molise, and Marche, the removal of nitrogen and phosphorus by mussels exceeded the input from farmed fish.
Intensive aquaculture of fish species in marine coastal areas results in the release of nitrogen- and phosphorus-based compounds into the environment. The input of nutrients occurs through the discharge of waste, including uneaten feed, metabolic excretion products, and feces.
These waste materials can be:
- Organic, in solid and/or dissolved form
- Inorganic, primarily composed of carbon, nitrogen, and phosphorus
If the release of these compounds into the environment exceeds the ecosystem’s natural carrying capacity, perturbations may occur in the receiving ecosystem, particularly in the water column and sediments. These phenomena are usually localized and of modest intensity, although in some cases, under specific environmental and farming conditions, may lead to:
- Eutrophication
- Reduction in dissolved oxygen
- Reduction in local biodiversity
The removal of nitrogen and phosphorus is carried out by extensive farming of bivalve shellfish, which reduces nutrient concentrations in the water column by utilizing them as a food resource.
This indicator provides an estimate of the input or removal of nitrogen and phosphorus, respectively, by fish and mussels in the coastal environment where aquaculture activities take place.
The indicator is particularly useful for carrying capacity analysis in the process of identifying Allocated Zones for Aquaculture (AZA).
To provide an estimate of the contribution to organic enrichment in the coastal zone generated by marine aquaculture.
The balance between the input of nutrients from farmed fish and their removal by bivalve shellfish allows for the estimation of the net quantitative contribution of aquaculture to trophic processes along the Italian coasts.
At the European level, the legislation does not establish common objectives, leaving it to Member States to define specific rules aimed at limiting the environmental impact of aquaculture activities.
In Italy, Legislative Decree No. 152/2006 on environmental regulations outlines the requirements for waters designated for bivalve shellfish farming (Article 87) and sets limits for nitrogen and phosphorus (Article 101, discharge regulations) in cases where wastewater from fish farming facilities with a stocking density greater than 1 kg/m² or a water flow rate of 50 l/s or less is discharged into sensitive areas (Tables 1 and 2, Annex 5, Part Three).
Regarding aquaculture facilities operating in freshwater, transitional waters, or marine environments, Article 111 of Legislative Decree 152/2006 mandates the issuance of a specific decree under the jurisdiction of the Ministry of the Environment (MATTM), in agreement with the Ministries of Agriculture and Forestry, Infrastructure and Transport, and Economic Development, and with prior consultation with the State-Regions Conference. This decree is intended to establish criteria for reducing the environmental impact of aquaculture activities.
To date, this legislative decree has not yet been issued, and there is no specific environmental legislation governing aquaculture activities.
Legislative Decree No. 190 of October 13, 2010, which transposes the Marine Strategy Framework Directive (2008/56/EC), identifies nitrogen and phosphorus inputs from aquaculture activities as pressure and impact factors, thereby requiring their quantitative assessment.
As part of the implementation activities of the directive, monitoring programs have been planned (Descriptor 5 "Eutrophication"; Operational Activity Plan 2021-2022-2023, Legislative Decree 190/2010). These programs, conducted by ISPRA-SNPA, aim to evaluate the organic enrichment produced by aquaculture facilities.
Descrizione 2
COM (2012) 494 Final. Crescita blu. Opportunità per una crescita sostenibile dei settori marino e marittimo.
COM (2019) 640 final. Il Green Deal europeo.
COM (2020) 381 final. Farm to Fork strategy for a fair, healthy and environmentally-friendly food system.
FAO. 2020.The State of World Fisheries and Aquaculture. 2020. Sustainability in action. Rome.
FAO. 2022.The State of World Fisheries and Aquaculture. 2020. Towards blue transformation. Rome.
Islam, M.S., 2005, Nitrogen and phosphorus budget in coastal and marine cage aquaculture and impacts of effluent loading on ecosystem: review and analysis towards model development. Marine Pollution Bulletin 50, 48-61.
ISPRA, anni vari, Annuario dei dati ambientali
Lupatsch, I., Kissil, G.W., 1998, Predicting aquaculture waste from gilthead seabream (Sparus aurata) culture using a nutritional approach. Aquatic Living Resources 11: 265-268.
Marino G., Petochi T., Cardia F. (2020). "Assegnazione di Zone Marine per l'Acquacoltura (AZA). Guida Tecnica", 214 p., Documenti Tecnici ISPRA 2020. https://www.isprambiente.gov.it/it/pubblicazioni/documenti-tecnici/assegnazione-di-zone-marine-perlacquacoltura-aza-guida-tecnica
MiPAAF (2014). Piano Strategico per l’Acquacoltura in Italia (2014-2020). pp.282. https://www.politicheagricole.it/flex/cm/pages/ServeBLOB.php/L/IT/IDPagina/8752
Palmerini R., Bianchi C.N., 1994, Biomass measurements and weight-to-weight conversion factors: a comparison of methods applied to the mussel Mytilus galloprovincialis. Mar. Biol., 120: 273-277.
Porrello S., Brigolin D., Marino G., Pastres R., Scardi M., 2013A, Nitrogen and phosphorus load from aquaculture activities. Methodological note as Supporting Documents for the implementation of Directive 2008/56EC.
Porrello S., Brigolin D., Tomassetti P., Scardi M., Pastres R., 2013B, Stima dei flussi di azoto e fosforo da Maricoltura: applicazione di modelli ad un caso studio (Mar Adriatico). Biol. Mar. Medit., 20(1): 110-111.
Programma operativo del FEAMP 2014-2020. https://www.politicheagricole.it/flex/cm/pages/ServeBLOB.php/L/IT/IDPagina/8752
Smaal A.C., Vonck A.P.M.A., 1997, Seasonal variation in C, N and P budgets and tissue composition of the mussel Mytilus edulis. Mar. Ecol. Prog. Ser., 153: 167-179.
The estimates provided in the indicator refer exclusively to the most commonly farmed species in Italy, namely gilthead seabream (Sparus aurata), European seabass (Dicentrarchus labrax), and mussels (Mytilus galloprovincialis). At present, reliable models for estimating nitrogen and phosphorus release or removal by other farmed species are not available.
Furthermore, there are no legally established reference values for nitrogen and phosphorus emissions from aquaculture into the environment. These may be considered in the upcoming decree defining the criteria for limiting the environmental impact of aquaculture activities, as per Article 111 of Legislative Decree 152/2006.
In the new round of Marine Strategy Monitoring Programs (annuals 2021-2022-2023), environmental surveys are planned in 11 marine areas occupied by aquaculture facilities. The monitoring protocols are aimed at assessing the organic enrichment produced by aquaculture facilities in the farming areas and estimating the contribution of aquaculture to “Eutrophication” (Descriptor 5). The results of these monitoring programs will enable implementation and refinement of the computational model used to estimate the nutrient balance in this indicator.
Qualificazione dati
Production data are those surveyed by MIPAAF under Regulation (EC) No. 762/2008 for 2019 and 2020, with support from CREA, and published in aggregate form by Eurostat: https://ec.europa.eu/eurostat/data/database.
Coastal Regions14/15
2019, 2020
Qualificazione indicatore
For estimating the input/removal of nitrogen and phosphorus, mathematical models based on the physiology of farmed organisms were used. These models take into account the percentages of nutrients—either provided as feed or present in the water column—that are utilized for growth or dispersed into the environment. Currently, these models are available for the two most important marine species in terms of national production: gilthead seabream (Sparus aurata) and European seabass (Dicentrarchus labrax).
To calculate the amounts of organic and inorganic compounds released due to farming activities for these two species, the models proposed by Lupatsch et al. (1998) and Islam (2005) were applied. These models consist of equations that relate, through simple linear regression based on previous studies, the nitrogen and phosphorus release per ton of fresh weight produced with the feed conversion ratio (FCR)—i.e., the ratio between the amount of feed supplied and the weight gain of farmed organisms.
For nutrient input estimation, since FCR is a key parameter, species-specific values were adopted, using an average value alongside minimum and maximum estimates for each species. This approach allowed the construction of an independent confidence interval for the regression line, thereby obtaining an estimated range for each FCR value.
For estimating the nutrient removal by farmed mussels, the calculations refer exclusively to the Mediterranean mussel considering the relationships indicated by Palmerini & Bianchi (1994) and Smaal & Vonck (1997). These estimates consist of equations that calculate the average nitrogen and phosphorus content per unit of farmed biomass. The estimation process involves conversions from wet weight (WW) to ash-free dry weight (AFDW), then from AFDW to dry flesh weight (DFW) (excluding the shell), and finally from DFW to nitrogen and phosphorus content. The description and application of the model are provided in Porrello et al. (2013A-B).
The indicator is calculated on a regional basis, but the methodology can be applied locally and in all marine coastal areas where fish and bivalve shellfish farming coexist.
The estimates of nitrogen and phosphorus input from fish farming facilities are considered as a total for euryhaline fish, summing the results for seabass and seabream without distinguishing between farming types (land-based tanks or offshore cages). The calculations cover the 14 marine-coastal regions in Italy where marine aquaculture facilities are present.
In 2020, the estimated nitrogen and phosphorus balance from marine aquaculture facilities indicates that nitrogen and phosphorus inputs from fish farms at the national level amounted to 1,038.4 and 178.6 tons per year, respectively, while the removal by farmed mussels accounted for 320.7 and 22.08 tons per year, respectively. This results in a net balance of 717.8 tons for nitrogen and 156.5 tons for phosphorus per year, with mussel farming contributing to the removal of over 30% of the nitrogen balance and 12% of the phosphorus balance.
Compared to 2018 (Database annuario 2020), in 2019 there was a decrease in nitrogen input of approximately 492.1 tons per year; similarly, phosphorus decreased by 84 tons per year. The removal of nitrogen and phosphorus by farmed mussels was also lower compared to 2018, by 56.5 and 3.9 tons per year, respectively. The data for 2020 indicate a further decrease compared to 2019 in nitrogen and phosphorus input, by approximately 79.8 and 13.7 tons per year, respectively. The removal of nitrogen and phosphorus by farmed mussels in 2020 was also lower, by 14.4 tons per year for nitrogen and 1 ton per year for phosphorus.
The net national balance, therefore, shows a reduction of approximately 435.6 tons of nitrogen and 80.1 tons of phosphorus released into the environment from marine aquaculture activities in 2019 compared to 2018, and a further reduction of 65.4 tons of nitrogen and 12.7 tons of phosphorus in 2020 compared to 2019. The observed decrease in both the input and removal of nitrogen and phosphorus is attributable to the lower production volumes of fish farming and mussel farming recorded in 2019 and 2020 (see the indicator "Aquaculture enterprises and production").
It is important to emphasize the need to develop and promote sustainable aquaculture systems capable of providing ecosystem services, as in the case of bivalve shellfish. In 2019, the estimated nitrogen and phosphorus balance from marine aquaculture facilities indicates that nitrogen and phosphorus inputs from fish farms at the national level amounted to 1,118.2 and 192.3 tons per year, respectively, while the removal by farmed mussels accounted for 335.1 and 23.07 tons per year, respectively. This results in a net balance of 783.2 tons for nitrogen and 169.23 tons for phosphorus per year, with mussel farming contributing to the removal of over 30% of the nitrogen balance and 12% of the phosphorus balance.
Dati
Table 1: Amounts of nitrogen and phosphorus from aquaculture facilities in the marine environment (2019, 2020)
ISPRA elaboration on MiPAAF-CREA data, EUROSTAT
Figure 1: Nitrogen balance from aquaculture facilities in the marine environment (2019)
ISPRA elaboration on data from MIPAAF-CREA, EUROSTAT
Figure 2: Phosphorus budget from aquaculture facilities in the marine environment (2019)
ISPRA elaboration on data from MIPAAF-CREA, EUROSTAT
Figure 3: Nitrogen balance from aquaculture facilities in the marine environment (2020)
ISPRA elaboration on data from MIPAAF-CREA, EUROSTAT
Figure 4: Phosphorus budget from aquaculture facilities in the marine environment (2020)
ISPRA elaboration on data from MIPAAF-CREA, EUROSTAT
In Table 1, the quantities of nitrogen and phosphorus released into the environment by seabass and gilthead seabream farms and the amounts removed by mussels for the years 2019 and 2020 are reported. The data related to fish farming have been calculated by combining both types of farming, namely, cage farming in the sea and land-based farming along the coastal strip or otherwise connected to it, and for both species, seabass and gilthead seabream. The data related to mussels refer to the most commonly adopted farming practice in Italy, which is longline farming with suspended ropes in the water column.
Tuscany is the region with the highest nitrogen and phosphorus input from aquaculture facilities, while Emilia-Romagna is the region where the highest removal of nutrients in marine coastal waters occurs (Table 1). This is due to the production volumes of mussels in Emilia-Romagna, which account for 24% of national production (see Aquaculture Enterprises and Production). The lowest removal of nitrogen and phosphorus was recorded in Molise. In Calabria, only one mussel farm was registered in 2020, while in Marche, Abruzzo, and Molise, there are no fish farming facilities.
For both years presented, in the regions of Molise, Abruzzo, Veneto, Marche, and Emilia-Romagna, the removal of nitrogen and phosphorus exceeds the input because the production volumes (and the number of farms) of mussels in these areas are higher than those of fish farming facilities (Figures 1-4). In the regions of Tuscany, Lazio, Sardinia, Liguria, Apulia, Friuli-Venezia Giulia, Campania, Sicily, and Calabria, the total net balance shows a higher input of nitrogen and phosphorus due to the greater production of farmed fish (Figures 1-4).