Estuaries Ecosystem : Where River Meets Ocean Everything about estuary ecosystem has been elaborated including Introduction, Types, Physical and Chemical Characteristics , Biota, Marsh Lands, Mangrove Forests, Food Web, Threats, Conservation, Restoration etc....

1. MAHATMA GANDHI CENTRAL UNIVERSITY
MOTIHARI BIHAR
ESTUARIES ECOSYSTEM
Presented By:
Raviranjan Kumar Gupta
M.Sc Zoology
MGCU2019ZOOL4012
Mahatma Gandhi Central
University, Motihari Bihar
Special Thanks:
Dr. Kundan Kishor Rajak
Mahatma Gandhi Central
University, Motihari Bihar

2. CONTENTS
 Introduction
 Types Of Estuaries
 Physio-Chemical Characteristics
 Biota Of Estuarine Ecosystem
 Salt Marshes
 Mangrove Forests
 Food Web In Estuarine Ecosystem
 Productivity Of Estuary
 Importance Of Estuaries
 Threats To Estuarine Ecosystem
 Conservation And Restoration Of Marsh Lands
 References

3. INTRODUCTION
 An Estuary is a semi-enclosed
areas where freshwater from
rivers meet ocean water, the two
being mixed by the action of
tides.
 Estuaries are highly productive
ecosystem and characteristically
are more productive than the
adjacent sea or river.
 The degree of mixing of salt and
freshwater depends on the
morphology of the estuary basin,
the rate and volume of
freshwater and the amount of
tidal flow.
The Yaquina Estuary
(Courtesy: The Wetlands Conservancy)

4.  In Estuaries, the salty ocean
mixes with a freshwater river,
resulting in brackish water.
Brackish water is somewhat salty
but not as salty as the ocean.
Brackish water has higher
dissolve salts than of fresh
water. i.e, 0.5-35%.
 An estuary may also be called a
bay, lagoon, sound or slough.
 Estuary possess unique
ecological features and biotic
communities. Estuaries are most
productive system of world. e.g,
The Coast Of Kerala
Continue………
Diagram Showing Mixing Of Freshwater and
Saltwater and Formation Of Brackish Water

5.  Coastal plain estuaries are created
when sea level rise and fill in an
existing river valley. The
Chesapeake Bay, on the East Coast
of the United States, is a coastal
plain estuary.
 The Chesapeake Bay was formed at
the end of the last ice age.
Massive glaciers retreated, leaving
a carved-out landscape behind. The
Atlantic Ocean rushed to fill in
the wide coastal plain around the
Susquehanna River, creating a large
estuary known as a Ria:A drowned
river mouth.
 There are four types of estuaries based on how they created
TYPES OF ESTUARIES
1.COASTAL PLAIN ESTUARIES
The Chesapeake Bay

6.  Tectonic Estuaries are caused by the
folding or faulting of land surfaces.
These estuaries are found along major
fault lines, like the San Francisco Bay
area in California.
 California’s San Francisco Bay is a
tectonic estuary.
2.TECTONIC ESTUARIES
San Francisco Bay
San Francisco Bay turns brown after nonstop storms:
Deposition Of Clay sized particles from 2 central rivers

7.  Bar-Built Estuaries form when a shallow
lagoon or bay is protected from the ocean
by a sand bar or barrier island.
 Eastern Seaboard and The Gulf Coast Of
North America are examples of Bar-Built
Estuaries.
3.BAR-BUILT ESTUARIES
Bar-Built Estuaries

8.  Fjords are U-shaped valleys formed by
glacial action.
 Fjords are found in areas with long
histories of glacier activity like
Northern Europe, Alaska and Canada.
 Puget Sound is a series of Fjords
estuaries in the U.S. state of
Washington.
4. FJORDS
Puget Sound Series Of Estuaries

9.  Estuaries having large variation in several parameters and create stressful
environment for organisms. This is the reason that large organisms are less
in number in this area than smaller organisms.
 Estuaries are dominated by soft muddy (combination of silt and clay)
substrate and is rich in organic matter. When the strong current prevails,
the substrate will be sand. If current is calm, the substrate is only fine
slit, will settle out.
 PHYSIO-CHEMICAL PROPERTIES
CHARACTERISTICS
Different zone has different climatic conditions,
making stressful for organisms

10.  The Water temperature in
estuaries, except fjords,
varies markedly because of
their shallow depths and
large surface area.
 It heats up and cools down
more rapidly under
atmospheric conditions &
the reason for this is
freshwater input.
 The surface water have the
greatest temperature range
& the deeper water have
lower temperature range.
 Temperature
CHARACTERISTICS
Temperature
Variation over
the year
Months
Temperature
Cooler Water Sinks
At Bottom And
Warmer Water At
Surface

11.  All the variations i.e,
the salinity, the
texture of substrate,
temperature, organic
matter content and
available oxygen are
controlled by wave
action and currents.
 The wave action in
estuary is small.
 As a result, there is
deposition of fine
sediments and
development of rooted
plants.
 Wave Action And Its Effect
CHARACTERISTICS
Deposition of fine sediments as tidal sand
banks and development of rooted plants

12.  When dense, salty seawater flows
into an estuary, it has an
estuarine current. High tides can
create estuarine currents.
Saltwater is heavier than
freshwater, so estuarine currents
sink and move near the bottom of
the estuary.
 When less-dense freshwater from a
river flows into the estuary, it
has an anti-estuarine current.
Anti-estuarine currents are
strongest near the surface of the
water . Heated by the sun, anti-
estuarine currents are much
warmer than estuarine currents.
 Estuarine Current
CHARACTERISTICS

13.  Current in estuaries are caused primarily by tidal action and river flow.
Velocities up to several knots can occur.
 The highest velocities occur in middle whereas in the bottom and side bank
the velocity is lowest.
 The erosion & deposition in the estuaries are due to currents which is a
natural cycle. However, In estuaries deposition exceeds erosion so there is a
net accumulation of silt. During dry part of the year, water movement is
severely reduced leading to stagnation, reduced oxygen content, formation of
algal blooms and incidence of fish kills.
 Current Velocities And Its Effects
CHARACTERISTICS
Lowest velocity at bank and bottom Highest velocity at middle

14.  The water of estuaries is
turbid because of the great
number of particulates in
suspension in the water.
 The turbidity is minimum
near the mouth and increase
with distance inland.
 The major ecological effect
of turbidity is a marked
decrease in the penetration
of light. Thus, in turn
decreases photosynthesis by
phytoplankton and benthic
plants, thereby reducing
productivity.
 Turbidity
CHARACTERISTICS
Ecological Effect Of Turbidity

15.  Oxygen is also the most important factors
in the estuary system.
 Since the solubility of oxygen in water
decreases with increase in temperature
and salinity, so the amount of oxygen
varies with these parameters.
 Oxygen is severely depleted in the
substrate. The high organic content and
bacterial population of the sediments
exert a large oxygen demand on the water.
 Estuarine sediments are ,therefore,
anoxic below the first few centimeters,
unless they have large no of burrowing
animals such as ghost shrimp Callianasa
and hemichordate worm Balanoglossus which
by their activities oxygenate lower
sediment layers.
 Oxygen
CHARACTERISTICS
Dissolve Oxygen Pattern

16.  In Estuaries, water level and salinity rise and fall with the tides. These
features also rise and fall with the seasons.
 During the rainy season, rivers may flood the estuary with freshwater and
lowers the salinity. During the dry season, the outflow from rivers may slow
to a trickle, the estuary shrinks and becomes much more saline.
 During the storm seasons, storm surges and other ocean waves may flood the
estuary with salt water.
 Most estuaries, however, are protected from the ocean’s full force, ocean
waves and wind by Geographical features such as reefs, islands, mud and sand.
 Salinity
CHARACTERISTICS
Profile of an idealized estuary
Types of species
living in an
idealized
estuary in
relation to
salinity

17.  Salinity also varies with depth in the
estuary. The salty seawater is more dense
and stays on the bottom. It flows in
along the bottom in what is frequently
known as a salt wedge. Meanwhile, the
fresher, less dense water from the river
flows out on the surface.
 It moves up the estuary on the rising
tide, then recedes as the tide falls.
This means that organisms that stay in
one place are faced with dramatic
fluctuations in salinity. They are
submerged under the salt wedge at high
tide and under low-salinity water at low
tide. If the area has a diurnal tide, the
organisms are subjected to two shifts in
salinity every day: one as the tide moves
upstream and a second as it retreats. In
an estuary with semidiurnal tides,
salinity changes four times a day.
 Salinity And Its Effects
CHARACTERISTICS
At high tide the crab is covered
by water with a salinity of 35‰.
At low tide it is covered by water with
a low salinity, between 5‰ and 15‰.

18.  The biota of estuaries is, in turns
regulated by degree of mixing.
 Estuarine diversification is lower than
river or marine because of tremendous
variation in physical environment.
 Major species are restricted to the
estuarine situation, such as Oyester & Crabs
and those that come from sea, such as
Shrimp.
 Very few species are derived from freshwater
and only those that are capable of
osmoregulation in the saltier environment.
 Estuaries are nursery ground for vast number
of marine animals shrimps and crabs to
fishes.
 Biota of Estuarine Ecosystem
BIOTA OF ESTUATINE ECOSYSTEM

19.  Although not always evident, primary producers do flourish on mudflats (The
bottoms of estuaries that become exposed at low tide often form mudflats)
 A few seaweeds—like the green algae Enteromorpha sea lettuce, and some red
algae—grow on bits of shell.
 Bacteria and archaea are extremely abundant on mudflats. They decompose the huge
amounts of organic matter brought in by rivers and tides. When the oxygen is used
up by decay, some bacteria produce hydrogen sulfide. This in turn is used by
sulfur bacteria, chemosynthetic bacteria that derive energy by breaking down
sulfur compounds like hydrogen sulfide.
 Diatoms and bacteria, including photosynthetic bacteria, actually account for
most of the primary production on mudflats
 Primary Producers
BIOTA OF ESTUATINE ECOSYSTEM
Enteromorpha
Red Algae

20.  The dominant animals on mudflats burrow in
the sediment and are known as infauna.
 Burrowers, like the fat innkeeper (Urechis
caupo), polychaete (Hesperonoe adventor), a
crab (Scleroplax granulata), a fish
(Clevelandia ios) and other guests.
 Mudflat inhabitants that feed on detritus
are:-
1. Deposit Feeders- Animals feeding on organic
matter that settles in the sediment.
2. Suspension Feeders- Animals, including
filter feeders, that feed on particles
suspended in the water column.
 Many deposit feeders and some other members
of the infauna are known as bioturbators
because they move and mix sediment when
burying or digging. Bioturbation helps in
the oxygenation of sediment, a most
important role in the case of the typically
anoxic sediments of estuaries.
 Infauna
BIOTA OF ESTUATINE ECOSYSTEM
Infauna

21.  The Protozoans, nematodes, and many
other minute animals that compose
the meiofauna also thrive on
detritus.
 The meiofauna are also known as
interstitial animals.
 The larger burrowing animals, or
infauna, include many polychaetes.
 Most are deposit feeders.
 Other polychaetes are suspension
feeders that filter water or
extrude tentacles to collect the
detritus that falls from the water
column.
 Meiofauna
BIOTA OF ESTUATINE ECOSYSTEM
a&b. Nematoda
c. Tardigrada
d. Kinorhyncha

22.  Very few mudflat animals can
be classified as epifauna,
those that either live on the
sediment surface or are
attached to a surface as
sessile forms.
 Crabs , Mercenaria mercenaria
, Mya arenaria , Macoma ,
ghost, mud snail (Upogebia)
shrimps and Uca are some
examples for epifauna.
 Some of these are of
considerable commercial
importance.
 Epifauna
BIOTA OF ESTUATINE ECOSYSTEM
Epifauna

23.  Most important predators in the
mudflat community are fishes and
birds.
 Fishes invade mudflats at high tide,
whereas birds congregate at low tide
to feed.
 The most significant predators on
mudflats are wading shorebirds.
 These include the willet, godwits,
dowitchers, and many species of
plovers and sandpipers such a curlews
and phalaropes. They feed on
polychaetes, ghost shrimps and other
small crustaceans, clams, and mud
snails.
 Predators
BIOTA OF ESTUATINE ECOSYSTEM
Differences in the bill length of wading shorebirds

24.  Estuaries in temperate and subarctic
regions worldwide are usually bordered
by extensive grassy areas that extend
inland from the mudflats. These
intertidal areas are partially flooded
at high tide and are known as salt
marshes, or sometimes tidal marshes .
 Sometimes they are grouped with coastal
environments flooded at high tide and
with freshwater marshes and collectively
called wetlands.
 Salt Marshes plants are Spartina
alterniflora, Spartina foliosa, Spartina
patens.
 It is characterized by a large variety
of plants resistant to salt spray, like
salt grasses and several species of
pickleweed.
SALT MARSHES

25. SALT MARSHES
 Bacteria
 The muddy salt-marsh substrate is home to decay bacteria, diatoms, and thick
mats of filamentous green algae and cyanobacteria.
 Bacteria play a crucial role by decomposing the large amounts of dead plant
material produced in the salt marsh.
 These bacteria and the partially broken-down organic matter are a major source
of the detritus that feeds many of the inhabitants of the estuary.
 Some bacteria are nitrogen fixers that enrich the sediment.
filamentous green algae DiatomsBacteria

26. SALT MARSHES
 Salt Marsh Animals
 The Some burrowing animals of
mudflats also inhabit salt
marshes. Nematodes, small
crustaceans, larvae of land
insects, and other small
invertebrates live among the
algal mats and decaying marsh
plants.
 Crabs are conspicuous
inhabitants of salt marshes .
Other marsh crabs are
scavengers that eat dead
organic matter. Some of these
species live in burrows.
 Marsh plants provide shelter
and food to many marine and
land animals.
Abludomelita obtusata Crabs
LobsterKrillShrimp

27. MANGROVE FORESTS
Mangroves are a group of trees and shrubs that live in the coastal intertidal
zone.
All of these trees grow in areas with low-oxygen soil, where slow-moving waters
allow fine sediments to accumulate. Mangrove forests only grow at tropical and
subtropical latitudes near the equator because they cannot withstand freezing
temperatures.
Mangrove forests provide food, fuel, timber and medicines either directly or indirectly.
 Mangrove forests stabilize the
coastline, reducing erosion from
storm surges, currents, waves,
and tides.
 The intricate root system of
mangroves also makes these
forests attractive to fish and
other organisms seeking food and
shelter from predators.
 Some common species are red
mangrove (Rhizophora mangle),
black mangrove(Avicennia
germinans) and the white
mangrove(Laguncularia racemosa).

28. MANGROVE COMMUNITIESDistributionofmangrovespeciesinWestCoastestuaries
Complex food web of Mangrove communities

29. FOOD WEB IN ESTUARINE ECOSYSTEM
Generalized food webs in estuarine ecosystems. Salt marshes (left) occur in temperate regions, mangroves (right) in the tropics.

30.  The high productivity results from estuaries being nutrients traps for both
physical(Based on the degree of mixing) and biological(Rapid recycling)
reasons.
 Also estuarine producers, which include seaweeds and marsh grasses as well as
benthic algae and phytoplankton, are capable of nearly year-round
photosynthesis.
 The higher the fluctuation of water level, the higher the productivity, the
tides serving to remove waste and to transport food and nutrients.
 Estimates of primary production range from 130 to nearly 6,000 grams dry
weight/m2/year for cordgrasses in salt marshes on the Atlantic coast of the
United States.
Why High Productive ?

31.  The Estuaries are tremendously productive and are home to large numbers of organisms,
many of which are of commercial importance. Estuaries also provide vital breeding and
feeding grounds for many animals.
 Estuaries are important stopover and wintering areas for many species of migratory
birds. The open spaces offer them safety from natural enemies, and food is plentiful.
 The worldwide economic value of marine wetlands as sources of food and as nurseries of
many food species, in recreation and tourism, as sources of wood and other materials,
in protection against storms and erosion, as well as in the maintenance of
biodiversity and water quality, is enormous.
 Estuarine environments are of great cultural and economic importance to the general
community.
 As transition zones between land and water, estuaries are invaluable laboratories for
scientists and students studying the complexity of biology, geology, chemistry,
physics, history and social issues.
 Tourism, fisheries, and other commercial activities thrive on the wealth of natural
resources estuaries supply. In New South Wales, commercial fishing around estuaries is
worth over $80 million per year, with recreational fishing estimated to be worth $500
million per year. The building industry sources sand and gravel from estuary areas
worth over $100 million per year.
 The protected coastal waters of estuaries also support important public
infrastructure, serving as harbours and ports vital for shipping, transportation and
industry.
Importance Of Estuaries

32.  The human intrusion in marine wetlands, particularly in highly productive salt
marshes and mangrove forests, have been disastrous.
 Countless have been obliterated, and many surviving ones are in danger of
disappearing.
 All around the globe estuaries are being dredged to make marinas, artificial
harbors, and sea-ports. Others are filled to create everything from industrial
parks and urban development to garbage dumps.
 The dredging of navigation channels increases the exposure of estuaries to
wave action, which often results in the destruction of salt marshes.
 Another problem in some estuaries is the reduction or elimination of normal
freshwater input when rivers are dammed or diverted. Sediment input from
rivers is decreased so that erosion of sediments by tides is not re-
plenished. The opposite can also be a problem.
 Deforestation and agriculture brings about an increase in sediment, which in
estuaries like Chesapeake Bay, decreases water quality and increases
pollution.
HUMAN INTRUSION AND THREATS TO ESTUARIES

33.  The destruction of salt marshes by human activities is a major worldwide
problem.
 The restoration of disturbed salt marshes to their natural condition is being
carried out as part of efforts to protect and preserve coastal wetlands.
 Some biologists encourage the natural regeneration of disturbed salt marshes,
but others prefer to accelerate recovery by replanting dominant species,
particularly cordgrass (Spartina ). For example, the University of Southern
Mississippi operates a nursery that grows salt marsh plants that are
transplanted in damaged marshes.
 The success of replanting depends on factors such as wave action and tides,
water chemistry (salinity, dissolved nutrients), and the substrate (slope,
sediment size, oxygen content).
 Recovery can take many years, and the length of the recovery period depends
on the degree of disturbance, environmental factors, and the relative
maturity of marshes. The more mature marshes take the longest to recover.
CONSERVATION AND RESTORATION OF MARSH LANDS

34. • IGNOU Study Materials “Ecosystem : Functioning And Types”
• Ecology And Environment, P.D.Sharma, Thirteenth Edition
• http://info.mheducation.com/rs/128-SJW-347/images/Marine_Science_Sample_Chapter_14.pdf
• www.google.com
• http://www.nzdl.org/gsdlmod?e=d-00000-00---off-0hdl--00-0----0-10-0---0---0direct-10---4-----
--0-1l--11-en-50---20-about---00-0-1-00-0--4----0-0-11-10-0utfZz-8-
00&cl=CL1.2&d=HASHd10071ff5b9a81a2180c80.4.3&gt=1
• https://www.nationalgeographic.org/encyclopedia/estuary/
REFERENCES