Eutrophication occurs when a body of water becomes overly enriched with minerals and nutrients, inducing excessive algae growth. This can deplete oxygen levels and harm plants and animals. Eutrophication can be natural, occurring over geological time, or cultural, accelerated by human activities like fertilizer and sewage runoff. Effects include hypoxia, which can kill fish, and algal blooms that block sunlight from reaching underwater plants and animals. The aquatic food chain is also disrupted, favoring bacteria and phytoplankton over larger zooplankton and reducing energy transfer efficiency. Preventing eutrophication requires reducing nutrient runoff from agriculture, development, and vehicles.

1. Eutrophication; food chain
in aquatic ecosystems
PRESENTED BY:
Mousami Jaria
St. George College of Management
and Science
MSc Microbiology
Semester 2

2. INTRODUCTION
• Eutrophication means when a waterbody is
oversupplied with minerals and nutrients
which induces excessive growth of algae .
• It results in oxygen depletion of the water
body eg; algal bloom, increase of
phytoplankton etc.
• It is induced by the discharge of nitrate or
phosphorus.

4. • Phosphate containing detergents, fertilizers
or sewage, domestic run outs into aquatic
ecosystem.
• Most lakes follow the path of
eutrophication over geologic time in. When
the addition of organic matter proceeds at
an increasing rate ,the process of
eutrophication accelarates.
• Eutrophication is a process and a trophic
state. The key element is change.

5. • Upwelling systems cycle through phases of
increased nutrient availability, high primary
and secondary productivity,and often oxygen
depletion in the lower water coloumn.

6. TYPES
• NATURAL EUTROPHICATION:
o Caused by natural process of nature not
interfered by human activities.
o Takes many years to affect whole water
bodies.
o Water bodies near industrial or human habitat
are affected by such source of eutrophication.

7. • CULTURAL EUTROPHICATION:
o It speeds up natural eutrophication because of
human activities.
o Results in algal bloom.
o Reduces amount of dissolved oxygen in water
leading to plant and animal death.

9. EFFECTS
• Oxygen depletion or hypoxia is a common
effect of eutrophication in water.
• The direct effect is that it kills fish specially
those which require high levels of oxygen.
• The algal blooms prevents sunlight from
entering into water thereby killing plants and
animals underneath.

10. DIED FISHES DUE TO
EUTROPHIC WATER

11. ALGAL BLOOM IN WATER

12. FOOD CHAIN IN AQUATIC ECOSYSTEM
• In lakes the food chain includes :
 BACTERIA
PHYTOPLANKTON
PROTOZOA
MICRO and MACROZOOPLANKTON
And the trophic links between them.
• Plankton food chain in lakes is affected in a
predictable manner by eutrophication.
• Phytoplankton biomass becomes relatively
greater while macrozooplankton biomass
declines.

13. • The relative biomass of protozoa may also
increase.
• Food chain function also is affected :
ecological transfer efficiency is lowest in
ultraoligotrophic lakes and hypereutrophic
lakes and highest in mesotrophic lakes.
• In ultra oligotrophic lakes co-occurance of
picoplankton with copepods that cannot
directly graze such small particles results in
long, energitically inefficient foodwebs.

14. • In hypereutrophic lakes similar food web
occurs owing to co occurance of cyanobacteria
and small macrozooplankton.
• The dominance of cyanobacteria in these
lakes can be linked to enrichment with
nutrients (nitrogen, phosphorus), while
zooplankton attributes to intense fish
predation.
• Changes in plankton food chain structure and
function can be reversed if nutrient loads are
substantially reduced.

15. • Effect of nutrient loadings are different in
freshwater and marine ecosystem.
• In ultraoligotrophic and hypereurotrophic
lakes the size or palatability of phytoplankton
disrupt the flux of energythroughout the food
chain by inhibiting large zooplankton grazing.
• In mesotrophic lakes short food chains
efficiently transfer energy from primary
producers to fish.
• Marine systems display more complex
planktonic food chains

16. • The main pathway of carbon flow from
cyanobacteria to zooplankon is from detritus
and dissolved organic matter ( microbial loop).
• Cyanobacteria may be used via microbial
pool.
• The carbon transfer to fish reflects the activity
in grazing food chain, because unsaturated
fatty acids are known to rapidly decompose

17. PREVENTION
• Shifts in phytoplankton and zooplankton
communities.
• Shifts in foodwebs as they support loss of
biodiversity
• Change in trophic interaction and changes in
ecosystem functions and biogeochemical
processes.

18. CONCLUSION
• Eutophication is a major problem in aquatic
ecosystems that is driven primarily by sulphur
and phosphorus loading.
• Eutrophication can result in increased incidence
and significance of algal bloom , anoxic
conditions, ocean acidification and altered plant
species diversity.
• The effects are production of toxins that affect
human and animal health, fish kills that
negatively impact the food security, food web

19. disruption and dead zones that disrupt
ecosystem.
• The disruptions in ecosystem functions
negative impact to tourism industry with
economic consequences
• To reduce the impact of eutrophication,
leaching should be reduced from
agriculturalactivities, growing perrenial plants,
reduced applicatin of fertilizers, planting
winter cover crops to reduce nutrient
leaching.

20. • Others include vehicle efficiency
advancements, enhanced removal of Nox
from exhaust, stricter emission standards etc.

21. THANK YOU