Inverse Modeling of the Microbial Loop J. Steele & A. Beet Woods Hole Oceanographic Institution
Benthivorous Fish Pelagic Invertebrate Predators Micro- Phytoplankton (>20 m) Seabirds Deposit-feeding Benthos Suspension- feeding Benthos Detritus Ammonia Fishing R Micro- Zooplankton (2-200 m) Meso- Zooplankton (>200 m) Nitrate Nano- Phytoplankton (<20 m) Planktivorous Fish Piscivorous Fish Pre-recruits Marine Mammals spawning recruitment
BiBi NiNi Losses from System due to inefficiency, e i External Inputs, K i N i = e i ( a ij N j ) + K i 0 < e i < 1.0, “Ecopath type” solution; specify e i, a ij K i solve for N i There are an equal number of variables and equations A unique solution exists
Benthivorous Fish B: 0.88 Pelagic Invertebrate Predators Sullivan & Meise Phytoplankton Seabirds Deposit-feeding Benthos Suspension- feeding Benthos DOC 638 Detritus 2.2x10^6 mg at N s^ -1 Ammonia Fishing Lobsters: 0.9 Shellfish: 0.9 Fish: Phyto 501 R Zoo ? 285 Micro- Zooplankton 202 Meso- Zooplankton 4.8x10^5 mg at N s^ -1 Nitrate+Nitrite 2793 Nano- Phytoplankton Planktivorous Fish B: 9.85 Piscivorous Fish B: Pre-recruits Marine Mammals 6.0 from fish & Squid 1.8 from Zoo 7.8 total spawning recruitment 900 Bacteria
BiBi NiNi External Inputs, K i N i = e i ( a ij N j ) + K i “Inverse” solution: set bounds on e i,, and solve for N i = b i. B i where b i is turnover rate Losses from System due to inefficiency, e i Problem: There are more variables than equations There is no unique solution
To obtain a unique solution the introduction of an objective function is needed. The maximization or minimization of this function provides a unique solution. Vezina and Platt, 1988 Question ecological; how appropriate is this function? Alternative maximize resilience
Phyto Microz mesoZ Detritus NO3 Pel.F. Dem.F Regn. S.P. L.P.
Phyto Microz mesoZ Detritus NO3 Pel.F. Dem.F Regn. S.P. L.P.
Phyto Microz mesoZ Detritus NO3 Pel.F. Dem.F Regn. S.P. L.P.
N1 Phyto N2 Microz N3 mesoZ N4 Detritus NO3 Pel.F. Dem.F S.P. L.P. R3 R2 R1 R4 Fluxes Regn Losses Reg n Graz
Proportion of intake to Z, D to higher levels F-ratioFraction of detritus regeneration / / M <= 1 (Resilience / Sum of squares) Proportion of intake to Z, D to higher levels F-ratioFraction of detritus regeneration / / M <= 1 (Resilience / Sum of squares)
Proportion of intake to Z, D to higher levels F-ratioFraction of detritus regeneration / / / / / / M <= 1 (Resilience / Sum of squares) Proportion of intake to Z, D to higher levels F-ratioFraction of detritus regeneration / / / / / / M <= 1 (Resilience / Sum of squares)