Estuaries

A Brief information of Estuaries

1. ESTUARIES
L A N D S C A P E R E S O U R C E S
V. Akhil Akash | 1190700032 | M. Arch Landscape | II year III sem| SPAV

2. CONTENT
•Introduction
•Characteristics
•Types of estuaries
•Estuaries in India
Landscape Resources
•Faunal resources
•Ecosystem resources
•Economic resources
•Cultural resources
•Environmental value
•People and estuaries
•Threats Estuarine
habitats

3. INTRODUCTION
•Estuaries are places where rivers discharge the water into the sea and they are semi enclosed water bodies connected
to open sea.
•These are semi enclosed bodies of water, connected to open sea, but are diluted by fresh water from land.

4. CHARACTERISTICS
Salinity
•The flow of fresh water from land give rise to a variety of saline
water across the cross section of estuaries
•Salinity changes with season and tidal periods
•Eg: Mandovi-Zuariestuary in Goa and Cochin backwaters in
Kerala are typical estuaries in which surface salinity ranges from
0.65% at the peak of the monsoon in August to 33.64% in the
hot pre-monsoon period in April.
Temperature
•Temperatures vary widely in estuaries owing to the mixing of
water of different temperatures and shallowness of the water.
•In shallow estuaries, the water is much cooler in winter and
warmer in summer.
•These temperature fluctuations affect the species composition
and eliminate most animals that cannot withstand wide changes.

5. CHARACTERISTICS
Sediments
•The sediment type influences the organisms living in the estuary,
especially plants and benthic animals. (animals that occur at
bottom of the ocean)
•Mudflats are common. The substrate here is composed of soft,
loose mud or a mixture of mud and sand.
•Characteristic vegetation such as eel grass in temperate areas
and mangroves in the tropics develops on mudflats, making
estuarine ecosystems very productive and at the same time
providing special habitat for animals.
•Mangroves are found in most estuaries along the Indian coast.
Sediment flow in Waikato and Waiparivers
Source: Compound Specific Stable Isotope tracing of sediment sources -tools to manage a sticky problem
in New Zealand’s freshwaters and estuaries | NIWA

6. CHARACTERISTICS
Turbidity
•Silt suspended in the water in estuaries causes the water to be
turbid.
•The degree of turbidity varies widely throughout the year; it is at
a maximum during the rainy season. It also varies from place to
place within the estuary.
•Turbid water prevents light from penetrating even one meter
below the water surface. This reduces the level of
photosynthesis by phytoplankton in the deeper layers.
•Shore plants which are not covered by turbid waters are
therefore the most important photosynthesizes of organic
matter.
•Salt-marsh plants such as spartina and zoosteraand mangrove
forest assume great importance as primary producers.
Turbidity in Amazon delta
Source: Compound Specific Stable Isotope tracing of sediment sources -tools to manage a sticky problem
in New Zealand’s freshwaters and estuaries | NIWA

7. CHARACTERISTICS
Nutrient flows
•The fertility of the estuary depends on the flow of nutrients from
the river and on tidal currents.
•Drainage from the land is the major source of nutrient inputs into
the estuary. In addition, industrial effluents and city waters also find
their way into the estuary.
•Some estuaries in Gujarat are subject to heavy industrial pollution,
making it difficult for fish to survive.
•The overall productivity of most Indian estuaries is low because of
their high turbidity. In Cochin backwaters, only 25% of the total
phytoplankton production is estimated to be used by the herbivore
population. The unconsumed food sinks to the bottom as detritus.
•Even though the estuarine phytoplankton production is low, it is well
compensated by the productivity of plants such as marsh grass,
reeds and mangroves.
•More than 50% of production is available to estuaries in the form of
detritus. Land drainage also supplies abundant detritus.
•The abundant detritus means that it is the basis for most of the
estuarine food chain. Several animals, or zooplankton, feed on the
detritus and thus are primary consumers.
Detritus-waster or debris of any kind
Nutrient flow in water bodies

8. TYPES
•Bar-built estuaries
form when a shallow
lagoon or bay is
protected from the
ocean by a sand bar,
sand delta or barrier
island.
Bar-built estuaries
•Tectonic estuaries are
caused by the folding
or faulting of land
surfaces.
Tectonic estuaries
•Coastal plain estuaries
are formed by the sea
level rising and filling
an existing river valley.
Coastal plain estuaries
•Fjords and rias are U-
shaped valleys formed
by glacial action.
Fjords are found in
areas with long
histories of glacier
activity.
Fjords and rias

9. ESTUARIES IN INDIA
Indian Coastal StatesEstuaries
Avg. discharge
(m3/sec/day)
Gujarat
Ambica
1
Bhadar
16
Daman ganga
93
Dhatarwadi
2
Gulf of Kutch
< 1
Machhundri
3
Madhuvanti
1
Mahi
383
Meghal
7
Narmada
190
Prabhas Patan
4
Sabarmati
33
Singoda
3
Tapi
210
Maharashtra
Daman ganga
93
Narmada
190
Karnataka
Karwar
128
Mandovi
56
Kerala Periar Estuary
8
Tamil Nadu
Cauvery
600
Ponnaiyar
21
Vaigai
28
Andhra Pradesh
Godavari
3, 500
Krishna
2, 100
Pennar
200
Odisha Mahanadi
2,100
West Bengal Ganges delta
35, 217
Source: Centre for Coastal Zone Management and Coastal Shelter Belt
Source 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

10. LANDSCAPE RESOURCES

11. FAUNAL RESOURCES
•Brackish waters are poorer in species diversity as compared to
the sea or fresh water.
•Seasonal fluctuations in salinity influence the distribution of
organisms in the estuary.
•Continuous rains during the monsoon harms marine fauna.
When salinity returns to normal after few months, the marine
animals re-establish themselves.
•Estuarine animals either adapt to avoid unfavorable salinities or
tolerate a range in salinity by using physiological mechanisms.
Eg: To avoid unfavorable salinity, barnacles shut their valves, mussels
close their shells, eupogebiaburrow into the substrate, and other
creatures migrate up and down the estuary.

12. ECOSYSTEM RESOURCES
•Estuaries are most productive ecosystems on earth
•They maintain water quality through natural filtration as
microbes break down organic matter and sediments bind
pollutants
•They help maintain biodiversity by providing a diverse range of
unique habitats that are critical for the survival of many species.

13. ECONOMIC RESOURCES
•They are tourist attractions.
•Used for transport and industry.
•They have ecological importance to commercial fisheries.
•Maintain water quality which benefits both people and marine
life
•Natural buffer between the land and ocean, absorbing
floodwaters and storm surges.
•They help maintain biodiversity by providing a diverse range of
unique habitats that are critical for the survival of many species.
•Many species of commercially important fish and shellfish use
estuaries as nurseries to spawn and allow juveniles to grow.
Boating in Estuarine waters of Hudson River in New York
Source: Seven Fun and Rewarding Things to Do in Americas Estuaries | The Pew Charitable Trusts
(pewtrusts.org)

14. CULTURAL RESOURCES
•People value estuaries for recreation, scientific knowledge,
education, aesthetic and traditional practices
•Estuaries also provide a great deal of aesthetic enjoyment for the
people who live, work, or use them for recreation.
•Estuaries provide us with numerous resources upon which
cannot be valued in market terms.
•They offer benefits and services which greatly improve our
lifestyle.
•Estuaries are an irreplaceable natural resource that must be
managed carefully for the mutual benefit of all who enjoy and
depend on them.
Sundarbans, West Bengal

15. ENVIRONMENTAL VALUE

16. ENVIRONMENTAL VALUE

17. ENVIRONMENTAL VALUE

18. PEOPLE AND ESTUARIES
•Estuariesareexcellentsitesforcommunityliving.
•Theyprovidefreshwaterfordrinkingandhygiene,accesstoboth
riversandoceanshelpsthedevelopmentoftradeand
communication.
•Someoftheearliestcivilizationsintheworlddevelopedaround
estuaries.Ur,inIraq,developedaround3800BCEnearthe
estuaryoftheEuphratesRiverwhereitmetthePersianGulf.
•Manymoderncitieshavegrownaroundestuaries,including
Jakarta,Indonesia,NewYorkCity,NewYork;andTokyo,Japan.
•Theseurbanareashaveundergonerapidchange,andputtheir
estuariesatenvironmentalrisk.

19. THREATS
LandReclamation
•Communitiesfilledestuariesforhousingandindustries
•Thesandandsiltdredgedfromtheestuariesisusedtocreate
newlandandbeachesEg:Jakarta,CiliwungRiverandJavaBay
Pollution
•Pollutionfromupstreamandalsooilspillsfromshipsare
unregulatedforyears
•Eg:AgriculturalrunofffromagricultureandindustryinNewYork
andNewJersey
•Oystershavebecometootoxictoconsumedueto
bioaccumulation.
Jakarta's land reclamation project
Pollution at New York NJ Harbor Estuary

20. THREATS
Overfishing
•Manyestuarieshavebeenoverfished.Therangeofpacifichave
drasticallyreduced.
•Eg:Bluefintuna,largepredatoryfishhavereducedinnumberand
arenowfarmedinTokyoBay
FloodingandNaturalhazards
•Destroyingestuariescreatesconditionsforflooding
•Estuariesprovideanaturalbarriertooceanwaves,whicherode
theshorelineanddestroycoastalhomesandbusinessandthese
areespeciallyvulnerableinearthquakesandtsunamis.
Tokyo’s Bluefin tuna market
Tsunami hit coast

21. OTHER THREATS
Invasive flora Invasive fauna Changes in flow of fresh waterBuilt structures
Climate change Land uses Unpermitted estuary openings Acidic soils

22. ESTUARINE HABITATS
Mangroves Marshes Sea grass beds Rocky reefs
River deltas Tidal pools Mid estuary sand banks Intertidal flats

23. ESTUARINE HABITATS
Estuarine beaches Muddy fringing marshesShallow open salt water Shallow open fresh water

24. REFERENCES
•Estuaries | NIWA
•estuary | National Geographic Society