1. Assessment of different aspects of Sundarban mangrove ecosystem through static and dynamic modelling Santanu Ray Ecological Modeling Laboratory Department of Zoology (Centre for Advance Studies) Visva-Bharati University Santiniketan 731 235 India Email: [email_address]

2. Introduction Sundarban Mangrove Ecosystem Situated in the Gangetic delta of the Hooghly-Brahamputra estuarine complex Extend over two countries, India and Bangladesh Seven major rivers in this zone Approximately 170 km in length and 60 km width, greatest halophytic formation (4200 sq km) of the world Many mangrove plant species are found in this ecosystem About 450 deltaic islands, out of which 40% are reclaimed and rests virgin

6. Elements of Ecological Network Node – Collection of elements, each node represents a compartment (biotic or abiotic) Edges – Line connects the nodes are called edges, directed edges are called arcs. Arcs are named using the numerical identifiers of the nodes they connect. Each arc in an ecological flow network can have an associated value. This value represents the magnitude of flow that occurs from the initial to the terminal node of the arc in a given unit of time.

7. F = Flow Matrix, Z = Input Vector, E = Export Vector and R = Respiration Vector

8. Four Major Tasks Performed by Network Analysis The evaluation of all direct and indirect bilateral relationships in a network of trophic exchanges The elucidation of the trophic structure immanent in the network The identification and quantification of all pathways for recycling medium extant in the network The quantification of the overall status of the network’s structure

9. The equations for throughflow become either for outflow and for inflow respectively

10. Flow diversity (D) and flow specialization (S) are measured by using the following formulae: Ascendency (A) and development capacity (C) are calculated with the help of following formulae:

12. Application of static model in Hooghly-Matla estuarine ecosystem Food web of reclaimed island

13. Food web of virgin island

14. Information Indices (Kcal m-2 y-1) Total system throughput Development capacity Relative Ascendency imports exports Respiration Redundancy Finn cycling index Virgin Reclaimed 539040 136570 2571000 700300 37% 29% 13.8% 12.75% 12.2% 5.37% 17.3% 19.2% 19.6% 33.5% 21.3% 8.3%

15. Conclusion: Magnitude of inputs and outputs (export) is much higher in virgin than reclaimed forests Primary productivity of virgin system is almost threefold greater than that of the reclaimed Detritus production is about eight times greater in virgin system than Reclaimed counterpart The phytoplankton community makes a significant contribution to the community production of mudflat in reclaimed system but in virgin it is dominated by benthic community Virgin system is more efficient in producing commercially valuable resources Detritivory (from D to II strongly predominates over herbivory (from I to II) in virgin system and in reclaimed system herbivory is greater than detritivory The ratio of herbivory : detritivory is almost 1:1(13400 Kcal m^2 y-1 : 15700 Kcal m^2 y-1 ) in reclaimed Island and in virgin counterpart it is about 1:3 (31700 Kcal m^2 y-1 : 83604 Kcal m^2 y-1 )

16. Relative Ascendency (37%) is higher than Redundancy (19.6%) in virgin forest whereas the reclaimed system shows high redundancy (33.5%) than ascendency (29%) of trophic pathways and therefore reclaimed system is probably highly resilient to subsequent perturbations About 21.3% of the total energy flow travels over cyclical pathways in virgin forest and only 8.4% in reclaimed forest. Only (31) cycles existing the in reclaimed system and and (38) cycles in virgin forest Contribution of litterfall into detritus is almost 16 times higher in virgin than reclaimed counterpart.

17. Conceptual Model of the Nitrogen Dynamics of Mangrove Litterfall Application of dynamic model

22. Sensitivity Analysis +0.69 +1.11 +0.42 +0.16 +0.82 +0.09 -0.21 +0.21 +0.21 -0.12 +0.12 -0.12 0.00 0.00 -0.11 0.00 0.00 0.00 +0.90 +0.90 -0.14 0.00 +0.21 +0.21 0.00 0.00 -0.1 0.00 +0.21 0.00 0.00 0.00 +0.26 +0.28 +0.07 0.00 0.00 0.00 +0.30 0.00 +0.21 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Temperature coefficient Half saturation constant for oxygen Leaching rate for SON to TON in water Leaching rate for SIN to DIN in water Microbial degradation rate for SON Nitrogen mineralization rate KT KDO LchR1 LchR2 MDR minit System Sensitivity S DIN S DON S PON S TON S SIN S SON S STN Description Parameter

23. +0.41 +0.72 +0.61 0.00 +0.90 +0.90 0.00 0.00 0.00 0.00 0.00 0.00 -0.01 +0.23 0.41 0.00 0.00 0.00 +0.21 -0.19 -0.21 0.00 +0.90 +0.90 +0.21 +0.23 +0.41 0.00 0.00 0.00 0.00 +0.22 0.00 0.00 0.00 0.00 0.00 +0.23 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Conversion rate for WTON to DON Conversion rate for SON to PON Conversion rate for WTON to PON Input rate for DIDAO Input rate for IDSO Input rate for PIDAO KCrDON CrSPON CrWPON IrDIDAO IrIDSO IrPIDAO System Sensitivity S DIN S DON S PON S TON S SIN S SON S STN Description Parameter

24. Sensitivity analysis has been carried out using the formula S= [  x /x]/ [  p /p] (Jorgensen, 1994) +0.61 +0.29 +0.41 +1.64 +0.60 +0.47 +0.26 +0.29 0.00 +0.26 +0.27 +0.21 0.00 0.00 +0.41 +0.28 0.00 0.00 +0.35 0.00 0.00 +0.28 0.00 +0.26 0.00 0.00 0.00 +0.28 0.00 0.00 0.00 0.00 0.00 +0.26 +0.33 0.00 0.00 0.00 0.00 +0.28 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Loss rate due to detritivores Loss rate of DIN from system Loss rate of DON from the system Loss rate of HAFA from SON of system Loss rate due to Mangroves Settling rate for PON LrD LrDIN LrDON LrHAFA LrM SrPON System Sensitivity S DIN S DON S PON S TON S SIN S SON S STN Description Parameter

25. Simulated & Observed results of Soil Total Nitrogen (STN) and Soil Organic Nitrogen (SON) during Calibration of parameters p < 0.05, Chi-square=312.42 (STN) and 294.11 (SON)

26. Simulated & Observed results of Soil Inorganic Nitrogen (SIN) during Calibration of parameters P < 0.05, Chi-square= 68.67

27. Simulated & Observed results of Dissolved Organic Nitrogen (DON) and Dissolved Inorganic Nitrogen (DIN) during Calibration of parameters p < 0.05, Chi-square = 4.94 (DON) and 38.21 (DIN)

28. Simulated & Observed results of Soil Total Nitrogen (STN) and Soil Organic Nitrogen (SON) during Validation p <0.05, Chi-square= 261.16 (STN) and 199.46 (SON)

29. Simulated & Observed results of Soil Inorganic Nitrogen (SIN) during Validation p < 0.05, Chi-square= 72.06

30. Simulated & Observed results of Dissolved Organic Nitrogen (DON) and Dissolved Inorganic Nitrogen (DIN) during Validation p <0.05, Chi-square= 8.54 (DON) and 161.47 (DIN)

32. Thank You