Estuaries

What is an estuary?An estuary is a partially enclosed body of

water where two different bodies of water meet and mix (e.g. fresh water from rivers or streams and salt water from the ocean, or fresh water from rivers or streams and chemically distinct water of a large lake).

Transition zone between river environments and ocean environments

Subject to both marine influences, such as tides, waves, and the influx of saline water; and riverine influences, such as flows of fresh water and sediment.

The flow of both seawater and freshwater provide high levels of nutrients in both the water column and sediment, making estuaries among the most productive natural habitats in the world.

Turbid watersWaters in estuaries are often turbid and

brackish Turbidity is caused by stirred up sediment

and the influx and withdrawal of organisms such as phytoplankton.

Two main challenges in an estuarySedimentation – Can be problematic for phytoplankton if

sustained, plankton need sunlight to survive, they do not get this if they are submerged in the sediment

Osmoregulation – Osmoregulators  Maintain a constant internal water/salt balance even though the

environment is different. Includes freshwater fish, many marine fish, all terrestrial animals  OsmoconformersHave internal osmolarity similar to that of the surroundings.  Most marine invertebrates, some vertebrates, e.g. sharks• http://www.youtube.com/watch?v=lBbSsUpCRdM

Freshwater fish tend to gain water and loose salt

Marine fish tend to gain salt and loose water

Provide habitats for large number of species – fish nurseries (salmon, sea trout etc). Also feeding grounds for many birds.

Primary producers are phytoplankton which feed on detritus in the water.

Many species of bacteria live in the sediment of estuaries, this can have implications on other sediment dwelling species as they are in direct competition for resources (oxygen).

Common species found in British estuariesMany animal species are found in British

estuaries, these include:arthrop0ds (crustaceans and insects) molluscscnidariansPolychaetesBirdsEchinodermsMany grass, phtyoplankton and seaweed

species

Threats to estuaries6o% of the worlds population live around estuaries and the

coast– Why?22/36 of the worlds biggest cities sit directly on estuaries.

Human threats:Increased sedimentation due to soil erosion up streamOverfishingDrainage of wetlandsEutrophication from nitrates and phosphates – causes algal

blooms etc – results in hypoxia and ultimately dead zonesPollutants including PCB’s plastics and heavy metalsOver management and damming of areas for human

purposes.http://www.youtube.com/watch?v=D1iv37Yn8bg

Task - Each of you have a journal article relating to

estuaries in some form, the journals do not have abstracts. Your job is to write one, it should be between 100 – 200 words.

https://springerlink3.metapress.com/content/v875220495363h23/resource-secured/?target=fulltext.pdf&sid=1xa24bw1tuh4wnjghond2tob&sh=www.springerlink.com

http://www.psparchives.com/publications/our_work/hood_canal/hood_canal/hood_canal_onsite_factor_2.pdf

http://archimer.ifremer.fr/doc/00000/3080/