Water An Introduction to aquatic ecosystems An ecosystem

Water An Introduction to aquatic ecosystems…

• An ecosystem is a functional/dynamic What is an Aquatic Ecosystem? unit comprising all living organisms (biotic factors) in a community and the Non living (abiotic) environment with which they interact • Aquatic ecosystems are ecosystems in bodies of water comprising aquatic communities and associated abiotic factors • Even though they are some of the most productive ecosystems, they are heavily exploited by man

• Aquatic Types of Aquatic Ecosystems ecosystems are classified according to abiotic factors such as Salinity • Salinity is the concentration of dissolved salts in a body of water Lowest Salinity Fresh water ecosystems Marine ecosystems Highest Salinity Source: Marine Ecosystems and Global Change Oxford University Press. ISBN 978 -0 -19 -955802 -5

1. Fresh water ecosystems • Fresh water ecosystems consist of lakes, rivers, streams etc. • Even though freshwater ecosystems constitute only 2% of earth’s surface, they assist greatly in the hydrological cycle by recycling surface runoff into the oceans • Fresh water ecosystems are mainly divided into 3 categories; - Lentic ecosystems - Lotic ecosystems - Freshwater wetlands

1. Lentic Ecosystems 2. Lotic Ecosystems 3. Fresh water wetlands Standing water ecosystems which include ponds and lakes. Flowing water ecosystems which include streams and rivers. Located in river banks and act as holding areas for excess water during flooding

Large Lakes can be divided into 3 zones… Littoral Zone Limnetic Zone Littoral Zone Profundal Zone Limnetic Zone Profundal Zone Source: Lake Access. org

“Man made tanks in Sri Lanka are also considered as freshwater ecosystems due to the large species diversity they support while in harmony with agricultural practices. But today, due to public ignorance, these tanks have been polluted by visitors, threatening the balance of these ecosystems”

2. Marine ecosystems • Marine ecosystems are divided into several zones Intertidal Zone Benthic Zone (Ocean floor) Pelagic Zone (Ocean water) - Neritic Province - Oceanic Province • They are the most diverse of all ecosystems on Earth owing to the fact that 71% of Earth is covered in oceans

Oceanic Zones Pelagic environment Neritic Province Oceanic Province Inter tidal Zone Bathyal Zone Benthic Environment Abyssal Zone Hadal Zone Source : 9 th Edition Biology by Solomon, Berg, Martin

• Due to excessive pollution of marine environments, oceanic dead zones have been identified • Oceanic dead zones are Hypoxic areas containing very low oxygen levels unfavorable for life “More than 4000 oceanic dead zones have been identified mainly due to pollution by surface runoff from agricultural lands containing excess fertilizer. ” Source: NOAA

References… • https: //www. nationalgeographic. com/environment/freshwater/ aquatic-ecosystems/ • http: //www. worldbank. org/en/news/feature/2017/01/22/increa sing-salinity-in-a-changing-climate-likely-to-alter-sundarbansecosystem • http: //www. lakeaccess. org/ecology/lakeecologyprim 9. html • https: //oceanservice. noaa. gov/facts/deadzone. html