Explain bioaccumulation and biomagnification

5.3.3 · Biology › Conservation & Human Impact

WHAT are we talking about?

WHY does it happen? (the two conditions)

Ek substance tabhi biomagnify karta hai jab woh:

Persistent ho — chemically/biologically break down na ho (e.g. DDT, PCBs, methylmercury). Agar woh jaldi degrade ho jaaye, toh kabhi accumulate nahi hoga.
Poorly excreted / strongly retained in tissue ho — body use flush karne ki bajaye store kare. Yeh retention do tareekon se ho sakti hai:
- Fat-soluble (lipophilic) substances (e.g. DDT, PCBs) paani ki jagah fatty tissue mein dissolve ho jaate hain, isliye urine mein nahi jaate.
- Protein-binding substances (e.g. methylmercury) muscle/tissue ke proteins se tightly chipak jaate hain, isliye woh bhi excretion resist karte hain — bina lipid-soluble hue.

HOW does the concentration multiply? (derive it from scratch)

Chalte hain maths banate hain, memorise nahi karte.

Step 1 — Consumers ke beech energy/biomass ka transfer efficiency define karo. Ek consumer trophic level se dusre tak, sirf lagbhag 10% biomass transfer hoti hai (baaki heat/respiration mein jaati hai). Toh 1 kg predator banane ke liye, roughly $10$ kg prey khaana padta hai. Yeh step kyun? Kyunki predator ko apni mass se kai zyada khaana padta hai — yahi concentration ka engine hai. (Note: yeh 10% rule consumer→consumer steps govern karta hai; paani se producers mein pehla uptake ek alag assimilation process hai — neecha mistake mein dekho.)

Step 2 — Toxin track karo, jo khota NAHI hai. Maano prey mein toxin concentration $C_{p r ey}$ hai (toxin ki mass per kg tissue). Mass $m_{e a t e n}$ prey khaane se toxin milta hai: $T = C_{p r ey} \times m_{e a t e n}$ Yeh step kyun? Total toxin ingested = concentration × amount eaten.

Step 3 — Predator (lagbhag) saara toxin rakhta hai lekin sirf 10% mass. Predator mass bani: $m_{p r e d} = f m_{e a t e n}$ jahaan $f \approx 0.1$ (transfer efficiency). Agar toxin ka fraction $r$ retain hota hai (persistent poisons ke liye $r \approx 1$ maano): $C_{p r e d} = \frac{T \cdot r}{m _{p r e d}} = \frac{C _{p r ey} m _{e a t e n} r}{f m _{e a t e n}} = \frac{r}{f} C_{p r ey}$

Step 4 — Simplify karo. $m_{e a t e n}$ cancel ho jaata hai! Humein magnification factor milta hai: $C_{p r e d} = \frac{r}{f} C_{p r ey}$ $r = 1, f = 0.1$ ke saath: $C_{p r e d} = 10 C_{p r ey}$

Yeh ek derivation hai, dump nahi: ×10 directly "10% biomass passes lekin 100% toxin passes" se aata hai.

Figure — Explain bioaccumulation and biomagnification

Worked Examples

Common Mistakes

Flashcards

Bioaccumulation ek toxin ka build-up hai

ek single organism mein uski lifetime mein

Biomagnification toxin concentration ka increase hai

food chain ke successive trophic levels mein

Ek substance ko biomagnify karne ke liye do properties chahiye

persistent (degrade na ho) AUR strongly retained/poorly excreted (fat-storage YA protein-binding ke through)

Approximate concentration factor per consumer trophic step

×10 (kyunki ~10% biomass transfer hoti hai lekin ~100% toxin transfer hota hai)

Retained toxins magnify kyun karte hain lekin freely-excreted nahi karte

retained toxins tissue mein rehte hain (fat ya protein mein) aur khaaye jaane par upar pass hote hain; excreted wale urine mein nikal jaate hain

Kya methylmercury fat-soluble hone ki wajah se magnify karta hai

nahi — yeh muscle mein proteins se tightly bind karta hai; retention, lipophilicity nahi, key hai

Formula

C_{n} = (r / f)^{n} C_{0}

mein

f

kya hai

consumer trophic levels ke beech biomass transfer efficiency (~0.1)

Derivation mein mass-eaten term kyun cancel hota hai

predator saara toxin rakhta hai lekin sirf 10% biomass, isliye concentration = toxin/mass amount eaten se independent hai

Kaun sa step 10% energy rule se govern nahi hota

abiotic water → producer uptake (bioconcentration factor, BCF se set hota hai)

DDT biomagnification ka classic real-world example

raptor (osprey/eagle) eggshells ka patla hona, population crash

Agar retention fraction r=0.05 aur f=0.1 ho, toh kya yeh magnify karega

nahi, factor 0.5 < 1 hai, concentration chain upar jaate jaate ghatti hai

Recall Feynman: explain to a 12-year-old

Maano tumhare paas aise stickers hain jo tumhare haath se kabhi nahi dhulte. Ek chota bug 1 sticker pick up karta hai. Ek frog 10 bugs khaata hai, toh ab frog ke paas 10 stickers hain. Ek saanp 10 frogs khaata hai — 100 stickers! Ek eagle 10 saanp khaata hai — 1000 stickers! Koi naye stickers nahi bane; eagle ne bas sabke stickers collect kar liye. Aur kyunki stickers chipak jaate hain (dhulte nahi — kuch tumhare skin ke grease mein chipak jaate hain, kuch glue ki tarah pakad lete hain), yeh dherte rehte hain. Isliye top wale jaanwar ke paas poison bhar jaata hai chahe paani mein sirf thoda sa tha.

Connections

Food Chains and Trophic Levels — 10% energy rule ×10 factor ko power karta hai
Persistent Organic Pollutants (POPs) — DDT, PCBs, dioxins (fat-soluble)
Mercury and Methylmercury Cycle — protein-binding metal biomagnification
Bioconcentration Factor (BCF) — water→producer uptake step
Pesticides and Silent Spring — Rachel Carson, DDT & raptors
Ecological Pyramids — pyramid of biomass vs pyramid of toxin (inverted)
Human Health & Fish Consumption Guidelines
Conservation & Human Impact — parent chapter