Biological processes algal growth - unipd.itlasa.dii.unipd.it/mces/LEX/15_mces.pdf · Fixed...

University of Padova LASA – Environmental Systems Analysis Lab Modelling and Control of Environmental Systems

1

GAsmesrdt

dA

where A: weight concentration of algae [mgX/l]

: growth rate [1/d]

r: respiration rate [1/d]

es: exudation rate [1/d]

m: non-predatory mortality rate [1/d]

s: sedimentation rate [1/d]

G: grazing [mgX/l/d]

Biological processes – algal growth

,...,,, SiCPNfLfTfTrefMAX

Copyright © 2008 Field Studies Council

http://www.theseashore.org.uk/theseashore/Plankton/Phyto.htm

http://creativecommons.org/licenses/by-nc-nd/3.0/


2

Temperature dependence

Linear: min

min

TT

TTTf

ref

Exponential: refTTTf

Optimum:

2

3.2optx

opt

TT

TT

eTf




3

Temperature °C

m

ax (

1/d

ay)



4

Light dependence: I(t,h)

Saturation: (Michaelis Menten equation)

Ik

IIf

L

Optimum (Steele):

optI

I

opt

eI

IIf

1

Iopt(t)?




5



6

f(L) for the calculation of the growth rate: integrate the previous ones

over depth and photoperiod

d

L

Lp

eIk

Ik

d

fLf

0

0lnSaturation:

opt

d

opt I

Ie

I

I

pee

d

feLf

00

Optimum:



7

Nutrient limitation

• P

• N

• Si, Fe, …

• Liebig: the composition of an organism is (nearly)

constant

• Phytoplankton: mostly C, H, O, N, P, Si and S

116110263106 PNOHC


8

Nutrient limitation

,min

,

PfNf

PfNfPNf ;

NKN

NNf

PKP

PPf

; NutKNut

NutNutf

Fixed stochiometry model

Nut = external nutrient concentration

Liebig’s Law of minimum

multiplication ~ “sinergy”

• harmonic mean

...,...,,, SifCfPfNfSiCPNf

,...,,,min,...,,, SifCfPfNfSiCPNf

...

1111,...,,,

SifCfPfNf

nSiCPNf

n

SifCfPfNfSiCPNf

...,...,,,

• arithmetic mean


9

Limitation function

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

0 1 2 3 4 5 6 7 8 9 10

N

f(N)f(N)=N/(N+kN)

kN=??

kN = ?


10

Growth dynamics

• Uptake (influenced by the

external concentration and by

the internal concentration of

the nutrient in the cell)

• Growth (depends only on

internal quota)

A two-step process

Ck

C

qq

qqCqf

C

minmax

max),(

minmax

min

min

min

min

qq

qqqf

q

qqqf

qqk

qqqf

Michaelis

Menten !

linear

As above with

k=qmin


11

A two-step process


12

Nutrient bioavailability

• Nitrogen:

– Organic:

• Dissolved

• Particulate

– Inorganic:

• Ammonia-Ammonium

• Nitrite

• Nitrate

• Phosphorus:

– Organic:

• Dissolved

• Particulate

– Inorganic:

• Orthophosphate

• Polyphosphate

• Colloidal


13

Redfield Ratio (RR)

116110263106 PNOHC

RR > 7 = P is limiting

RR < 7 = N is limiting

pesoin 1

731

141

16

moliin 1

16

Redfield di Rapporto

PNRR

PNRR

PNRRRedfield Ratio

moles

weight


14

Redfield Ratio

116110263106 PNOHC

RR = N : P = 7

Often calculated using TN / TP, however:

• not all forms are bioavailable

• two-step dynamics

• even if concentration in water is low, uptake could be balanced by

other processes (e.g. flux from sediments)

• the limiting nutrient could be harder to reduce than others (e.g. P in

lakes)


15

Platt Index

• absolute • relative

P

NL

PP

NN

l

where:

; PfNfK ; NKN

NNf

PKP

PPf


16

Limitation due to other nutrients

• Silicon

• Oligoelements (Fe)

• Carbon (rarely limiting)


17

Silicon Limitation


18

Silicon Limitation

da: Cloern J.E., Our evolving conceptual model of the coastal eutrophication problem

Diatoms vs…


19

Co-limitation

0

0,05

0,1

0,15

0,2

0,25

+ C + P + N + TN + ALL -0,2

0

0,2

0,4

0,6

0,8

1

1,2

+ C + P + N + TN + ALL

0

0,1

0,2

0,3

0,4

0,5

0,6

0,7

0,8

0,9

+ C + P + N + TN + ALL

0

0,1

0,2

0,3

0,4

0,5

0,6

0,7

0,8

0,9

1

+ C + P + N + TN + ALL

da: Strener R.W & Gorver J.P., Algal growth in warm temperate reservoirs: Kinetic examination of Nitrogen, Temperature, Light and other nutrients

Chlorophyll growth rates

+C +P +N +TN +all +C +P +N +TN +all

+C +P +N +TN +all +C +P +N +TN +all


20

Biological processes – grazing

2020 T

np

T

ref zmmTgG

ZATfTCG greff

ZTfTCG grefg

GAsmesrdt

dA

j

iji GG

Copyright © 2008 Field Studies Council

http://www.theseashore.org.uk/theseashore/SpeciesPages/Pla

nkton/Copepod.JPG.html

http://creativecommons.org/licenses/by-nc-nd/3.0/


21

Biological processes

Zooplankton Growth

GZmexrgdt

dZ

where Z: weight zoopl concentration [mgX/l]

g: growth rate [1/d]

r: respiration rate [1/d]

ex: excretion rate [1/d]

m: non-predatory mortality rate [1/d]

G: predation mortality [mgX/l/d]

No settling


22

Phosphorus Cycle

• Key element for life:

– one of the 5 most important elements found in living organisms (60% of bones as calcium phosphate, also found in soft tissues)

– energetic metabolism: ADP – ATP

– found in DNA, RNA, phospholipids, etc.

• Agriculture (fertilizers) and industrial processes (e.g. detergents, medicines)


23

Mozetic et al. (2010)

Decreasing P load and aquatic ecosystem productivity

0

1000000

2000000

3000000

4000000

5000000

6000000

0

1000

2000

3000

4000

5000

6000

7000

19

68

19

71

19

74

19

77

19

80

19

83

19

86

19

89

19

92

19

95

Sard

ine

, kg

PO

4, t

Carico di PO4 scaricato dal fiume Po (t/y)

Sardine (kg sbarcato, lag di 1 anno)


24

Phosphorus cycle Slow, sedimentary cycle (no gas phase)

Marine sediments

P cycle

Storage (rock and

sedimentary deposits)

Up to million

years

Inputs (e.g. mining)


25

Phoshorus storages 0,1% Earth’s crust

Mainly

• Ca5F(PO4)3 (95%)

• Ca3(PO4)2

in magmatic and metamorphic rocks, sedimentary deposits (marine phosphorite beds 80% of potential P), guano from birds (most ancient fertilizer source)


26

Phosphorus in the environment Inorganic P: nearly always as phosphate

Orthophosphate (PO43- ion) is the main bioavailable form

pH play an important role:

Image from Holtan, H., Kamp-Nielsen, L., Stuanes, A.O., 1988. Phosphorus in

soli, water and sediment: an overview. Hydrobiologia 170: 19-34

{ Reduced forms, the most common in the environment

HPO42- in cultivated soil

(more basic)


27

Phosphorus in the environment

Organic P (hydrolyzed into inorganic P):

• Dissolved (mainly polyphosphate with low molecular

weight)

• Particulate (mainly polyphosphate with high molecular

weight adsorbed to organic sediments, organic acids,

esters)

• Colloidal (dispersed phase with dim. 10-6 – 10-9 m

throughout a continuous phase): bioavailable (but

secondarily)


28

Adsorbed P

Accumulated in the lithosphere

Adsorption:

• physical (reversible)

• chemical (irreversible or partially irrev.)

– Complexes with con metal cations (Ca, Fe, Al) are formed

– Substitution of water molecules or silicate ions (with high conc. of

phosphates) in clays. Enhanced by low pH.


29

Adsorbed P

P has a strong tendency to adsorbe →

• Land-sea transport through erosion (solid transport), no

transport of dissolved forms (e.g. leaching)

• Particulate P not much bioavailable = limiting despite

abundance, sometimes more limiting than N even if

organisms need less P than N


30

Adsorbed P

Deposition-release in water environments. Factors influencing adsorption:

• Granulometry (ads. increase with fine fraction)

• Organic substrate: not a general rule (can ads. phosphates, or block adsorption sites on inorganic particles)

• Redox potential:

– > 200 mV → Fe3+ and insoluble hydroxides with phosphates

– In reducing conditions, Fe2+ and P becomes soluble

Anoxia can lead to P release from sediments (Baltic)


31

Adsorbed P

Factors influencing adsorption:

• Temperature: influences bacterial processes which hydrolyze

organic P.

• pH: no general rule


32

P cycle

Food-web

plants animals

bacteria

P storages (rocks, guano, bones)

erosion, weathering (chemical, physical, biological),

resuspension, release from sediments, etc.

Birds, fish dead

organisms

Phosphate

bacteria

(degradation of

bones,

excretions, dead

organisms)

uptake from primary producer

from inorganic to organic

Marine sediments (losses)

Precipitation,

adsorption

Adattato da Calligaro e Mantovani, 2001

Dissolved phosphates

(inorganic P)


33

Surface water bodies: sources of P

loads

• Uncultivated soils

• Precipitations

• Wastewaters (1.5 gP/adult/day, detergents),

also industrial discharges, livestock

activities, etc.

• Diffuse sources (e.g., agricultural fields)


34

Internal loads: transport from sediments to

epilimnion (lakes)

Influenced by:

• Diffusion of P into water column (pH, redox, etc.)

• Turbulence (direct transport or re-create gradients)

• Convection (anaerobiosis: CH4, N2, CO2 bubbles)

• Bioturbation

• Low saturation capacity for the sediments

• Shallow depths


35

Dynamics of biogeochemical cycles

Biogeochemical cycles for different nutrients

are characterized by different dynamics and

time-scales (RR correction)

15 40 dtdt PN

University of Padova LASA – Environmental Systems Analysis Lab

For the modelling exercise: the k-C* model of

nutrient abatement in wetlands

0%

10%

20%

30%

40%

50%

60%

70%

80%

0 5 10 15 20 25 30

tempo di ritenzione (giorni)

eff

icie

nza d

i rim

ozio

ne

T=20°C

T=15°C

T=10°C

T=5°C

q

k

CC

CC

i

o

*

*ln

sA

Qq

365

Plug flow, 1st order; can be used for all pollutants: N, P, SS, bacteria, etc.

As= wetland surface, m2;

Ci = pollutant concentration in the inflow (mg/l);

Co = concentration in the outflow (mg/l);

C* = background concentration (mg/l);

k = first order rate (m/y); can depend on temperature

Q = average flow through the system (m3/d);

q = specific hydraulic load (m/y).

Rem

ov

al e

ffic

ien

cy

Retention time (days)


Real world is complicated

• Typical background values

Costituente Unità di misura Intervallo di concentrazioni

BOD5 mg/l 1-10

TSS mg/l 1-6

N organico + TN mg/l 1-3

Coliformi fecali MPN/100 ml 50-500

NH4-N mg/l <0.5

NO3-N mg/l <0.1

TP mg/l <0.1

Substance Currency Range of concentration


Books on wetland models

• Kadlec & Knight, 1996. Treatment wetlands. CRC

press (Second Edition also available by Kadlec &

Wallace)

• ANPA, 2002 Linee guida per la ricostruzione di

aree umide per il trattamento di acque superficiali http://www.apat.gov.it/site/it-

IT/APAT/Pubblicazioni/Manuali_e_linee_guida/Documento/manuali_lineeguida_2002_9.html

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