Gianmarco Giordani , Maria Snoussi and MaghLag partners

1. LOICZ biogeochemical budgets of six North African coastal lagoons: an application in the framework of the MaghLag network GianmarcoGiordani, Maria Snoussi and MaghLag partners

2. Objectives • Applied the LOICZ biogeochemical approach to the MaghLag coastal systems: • MoulayBouselham (Morocco, Atlantic Coast) • Nador (Morocco, Mediterranean Coast) • El Mellah (Algeria) • Bizerte (Tunisia) • El Biban (Tunisia) • Ghar el Melh (Tunisia) • Support cooperation and networking among North African Countries

3. Main characteristics of LOICZ Biogeochemical model (LOICZ-BM) • Use a general approach that can be apply to the majority of coastal systems. • Use few data that are normally collected in the monitoring activities • Easily applicable and with results that can be easily understood • Robust; • Informative about processes of CNP fluxes.

4. Output of the LOICZ-BM Important information on: Water fluxes through the system (residence time) Nutrient fluxes (input, output, source, sink) Ecosystemic functions linked to the metabolism (NEM, Nfix-denitr) Details, tutorial and examples at the LOICZ- Biogeochemical Modelling Node web page : http://nest.su.se/mnode/

5. Location of the MaghLagsites Algerie Main characteristics: Mediterranean climate with 2 main seasons (wet and dry) (except MoulayBouselham): High freshwater inputs are observed during wet season. Dry season is characterized by strong marine intrusion due to high evaporation rates in comparison with precipitation. Most of nutrient and pollutants are delivered during wet season. Main human impacts are relative to population, agriculture and livestock, occasionally industries play some roles. Strong economic growth is expected in the near future with consequent increase of human impacts.

6. Datasets • Water fluxes, salinities and nutrient concentrations are relative to few years in the last decade. • Most of the data are relative to published papers or specific research activities and usually are incomplete and/or have few replicates • No data are available from routine monitoring • Big efforts from the participants to find consistent information !!

7. Main problems (we’re working on them..) • MoulayBouselham: • NEM and (Nfix-denit) values are too high • Nador: • Nutrients concentrations are available only for wet season; • Salinity in the system (Ssys) is too similar to salinity in the Sea (Ssea), salt budgets would provide too rough estimates of exchange flow (Vx) between Sea and system • Mellah: • Vx is negative in the dry season since there is marine intrusion but Ssys is lower than Ssea (a significant freshwater input is missing?) • Mellah, Ghar el Melhand El Biban • Nutrient inputs from the watershed are missing (a rough estimation was conducted from the list of human activities conducted in the watershed and standard coefficients to convert them in nutrient inputs considering soil retention) • All data need to be validated !!

8. Water and salt budgets • Eight consistent water and salt budgets are obtained • All of them follow the one-box one layer model • Wet and dry seasons budgets are available for Bizerte and MoulayBouselham • Wet season budgets are available for Nador and El Mellah • Annual budgets are available for El Biban and Ghar el Melh lagoons

9. Area versus Water residence time Bizerte dry (B-d) and wet (B-w) season El Biban annual (EB-a) Ghar el Melh annual (G-a) El Mellah wet season (EM-w) Nador wet season (N-w) Sites with high water residence time are more sensitive to pollution than small sites with fast water renewal Moulay Bouselham dry (MB-d) and wet (MB-w) season

10. High water fluxes are reported for MB (probably due to high tidal flushing) and N in wet season. Low water fuxes are reported for EM and G probably because of their size Marine intrusions are reported for B-d and EB-a. Water Fluxes Vr=residual flow (negative => water export from the lagoon positive => marine water intrusion Vx = exchange flow (always positive is the lagoon water replacedwith marine water)

11. Nutrientfluxes In the systems where direct estimations are not available (El Mellah, Ghar el Melh and El Biban), nutrient loads are estimated as follwing: Human activities conversion: STANDARD COEFFICIENT (per individual) (OECD, 2008) • Inhabitants: 22 mol P/y ; 321 mol N/y • Cattles/camels: 239 mol P/y ; 3914 mol N/y • Sheep/goats: 26 mol P/y ; 350 mol N/y • Poultry: 5 mol P/y ; 34 mol N/y 50% of the loads of humans and 95% for animals was retained in the soil before reaching the system.

12. Nador and El Mellah are the systems that received the highest DIP loads DIP loads to Bizerte are minimal and limited to the wet season

13. Nador and El Mellah are still the systems that received the highest DIN loads Bizerte received high DIN loads in the wet season. The loads to the other systems are lower than 50 mmol m-2 y-1

14. Redfield DIN:DIP ratio in the loads are generallyconsideredas “balanced”. Higher ratios are indicative of agriculture pollution (not point source of pollution): Bizerte? Lowerratios are indicative or urbanpollution (point source pollution ): MoulayBouselham ?? El Mellah, Ghar El Melh and El Biban have ratios similar to Redfield since they are calculated

15. *1 *2 *1 =18.32 mmol m-2 d-1 *2= 50.44 mmol m-2 d-1 Nutrient internal transformation ( D positive => source; D negative => sink) DIP: High seasonal variation in MoulayBouselham El Mellah, Ghar el Melh and El Biban are DIP sinks Nador is a modest source of DIP and Bizerte is well balanced DIN: MoulayBouselham have very high values (to be checked). Nador , El Mellah and El Biban are DIN sink Bizerte is a DIN source

16. Ecosystemic functions: Net Ecosystem metabolism (NEM) = (p-r) NEM overlap DDIP since is based on DDIP and C:P ratio of the dominant primary producers that in all system is considered 106:1 (Redifield: phytoplancton). High seasonal variation in MoulayBouselham In El Mellah, Ghar el Melh and El Biban production (p) dominate over respiration (r) Nador and Bizerte are well balanced

17. Ecosystemic functions: N fixation – denitrification = (Nfix-denit) * * * Out ofrange It’s always the more problematic result as it’s at the end of all calculations and all errors accumulate. MoulayBouselham have values higher than 20 mmol m-2 d-1 (not consisent). Nador and El Mellah are net denitrifier, while in Bizerte, Ghar el Melh and El Biban , N fixation is the dominat process.

18. Concluding remarks • LOICZ biogeochemical approach is a good tool to collect information and identify data gaps in coastal systems. It supports collaboration among different researchers and data owners. • In MaghLag lagoons ,this exercise is only at the beginning but interesting indications are emerging. Anyway the results have to be considered as preliminary. • Available datasets are not exhaustive and with low numbers of replicates. Temporal and seasonal variations are usually not considered. LOICZ approach can be a useful tool to orient future monitoring and research activities • All data and results need to be validated. Sensitivity analyses could be useful tools to support results and identify uncertainties. • MaghLag is a great opportunity for consolidating cooperation and networking among North-African countries which share common threats, perspectives and goals.

19. Thanks for your attention!!!!! Merci pur votreattention !!!!

20. Merci Gianmarco!