1. Aquatic ecosystems

2. Aquatic Ecosystems An ecosystem located in water bodies
rivers, streams and springs
Fresh water ecosystems
Flowing water (rivers, streams and springs)
Static / slow moving water (ponds, lakes, pools / swamps)
lakes
ponds
Open sea
Marine eco systems
Open sea
Coastal
Estuary and salt marshes
Coral reefs and mangroves
Estuary and salt marshes
Coral reefs and mangroves

3. Fresh Water Ecosystems
Fresh water covers 0.8% of the Earth's surface and contain 0.009% of its total water.
Freshwater ecosystems contain 41% of the world's known fish species.
Two types of freshwater ecosystems:
Lotic : Flowing water (rivers, streams and springs)
Lentic: Static / slow moving water (ponds, lakes, pools)

4. Lotic Ecosystems
Species adapted to live in conditions of constant flow
Variation in lotic ecosystems (even within a river or a stream) is considerable and is determined by
Shape of stream / river bed (can form microhabitats)
Stream / river bed's gradient
Quantity of water
Velocity of the current
Faster moving water has higher concentrations of dissolved oxygen, and therefore supports greater biodiversity
Light
Temperature
most lotic species are poikilotherms, whose internal temperature varies with the surrounding temperature
Water chemistry (which changes in large rivers)
Ecosystems of rivers, streams, springs and other such freshwater bodies where there is water flow are called ‘Lotic ecosystems’. Lotic refers to flowing water, derived from the Latin word lotus.
Though both a tiny mountain spring and a river are lotic waters, there are certain characteristics that are common to lotic ecosystems, making them different from others. Most importantly, the biotic matter in these ecosystems is adapted to live in conditions of constant unidirectional flow.
But there is also a high degree of heterogeneity in lotic ecosystems, depending upon a number of biotic and abiotic factors. The shape of the river / stream bed, its gradient, the quantity of water that is flowing and its velocity all have a bearing on the ecosystem components. Flowing water changes the contours of the bed and bank due to deposition and erosion. It can also create pools of water which have their own microhabitat. Water flowing at a faster rate has more dissolved oxygen and therefore supports greater biodiversity.
Light is an important abiotic factor in lotic ecosystems. It provides the energy necessary for photosynthesis in primary producers. Turbulent water allow less light to pass through, as do tree covers surrounding a flowing water body. Lotic waters with lesser light penetration are preferred by prey species, since it provides them greater cover.
Temperature is an important abiotic factor that determines the nature of lotic ecosystems. This is because most lotic species are poikilotherms whose internal temperature varies with the surrounding temperature. Shallow streams are typically well mixed and maintain a relatively uniform temperature within an area. In deeper, slower moving water systems, however, a strong difference between the bottom and surface temperatures may develop.
Water chemistry plays an important role in determining the ecosystem of the river / stream. Oxygen is an important chemical parameter since it is required by all aerobic organisms for survival. It enters the water mostly via diffusion at the water-air interface. Oxygen’s solubility in water decreases as water temperature increases. Fast, turbulent waters expose more of the water’s surface area to the air and tend to have low temperatures and thus more oxygen than slow moving waters. Oxygen is a byproduct of photosynthesis, so systems with a high abundance of aquatic algae and plants may also have high concentrations of oxygen during the day. These levels can decrease significantly during the night when primary producers switch to respiration. Oxygen can be limited if there is a large amount of organic decay occurring. (Source: Wikipedia)

5. Lotic Ecosystems Mammals (dolphins, otters)
Reptiles (turtles, crocodiles, snakes)
Amphibians (salamander)
reptiles
amphibians
Fish
The biotic components of lotic ecosystems include
1. Bacteria – who play an important role in energy transfers
2. Primary producers like algae (phytoplankton and periphyton) that have a larger population in slow moving streams; mosses and liverworts that attach themselves to rocks and other solid substrates; duckweed and water hyacinth that are free floating on the water’s surface.
3. Primary consumers like macroinvertebrates. Up to 90% of the invertebrates in some lotic systems are insects. They occupy almost every available habitat and have developed special adaptations like anchored pads, claws, suction cup like devices and streamlines bodies for surviving in lotic waters. Other invertebrates common to flowing waters include molluscs (snails, clams, mussels etc.) and crustaceans (crabs, crayfish etc. These invertebrates are prey to organisms higher in the food chain.
4. Fish – An adaptation in fish in lotic ecosystems is that they are dorso-ventrally flattened to reduce flow resistance. They are also adapted to live in sheltered areas and the bottom of the rivers / streams, since swimming in strong currents requires a lot of energy. Some fish in lotic ecosystems can move between fresh and salt water.
5. Reptiles, amphibians
6. Mammals
Fish
Macro invertebrates
Insects
Molluscs (snails, clams, mussels)
Crustaceans (crabs)
Frog
Macroinvertebrates
Primary producers
Algae, Mosses, Liverwort,
Duckweed, Water hyacinth
decomposers
Primary producers
Bacteria
Sunlight
nutrients
riparian

6. Lentic Ecosystems Physical characteristics Chemical characteristics
Lakes are heterogenous and not a uniform mass of water
Biodiversity within a lake is also variable and depends on
Physical characteristics
Light
Temperature
Water currents
Chemical characteristics
Nutrients
Contaminants
Lentic is derived from the Latin word ‘lentus’ which means sluggish
The physical, chemical, and biological characteristics of lakes are extremely variable. Lakes vary physically in terms of light levels, temperature, and water currents. Lakes vary chemically in terms of nutrients, major ions, and contaminants. Lakes vary biologically in terms of biomass, population numbers, and growth rates. The heterogeneity is spread over space (spatial) and time (temporal – time of day, season etc.) and is very structured.
Source:
Light is an important abiotic factor that affects the lentic ecosystem. It impacts water temperature and photosynthesis, which in turn has an effect on the oxygen content in the water. Light intensity at the lake surface varies seasonally and with cloud cover and decreases with depth down the water column. The presence of a lot of decaying organic matter and suspended matter reduces the depth to which light can reach. The deeper into the water column that light can penetrate, the deeper photosynthesis can occur.

7. Lake zones Littoral zone Limnetic zone (open water) Terrestrial plants
Emerged plants
Floating plants
Submerged plants
A typical lake has distinct zones. The littoral zone is the near shore area where sunlight penetrates all the way to the sediment and allows aquatic plants to grow. Plants that grow in the littoral zone act as a food source and provide a habitat for fish and other organisms.
The limnetic zone refers to the open water areas where light does not generally penetrate all the way to the bottom. Within the limnetic zone, the Euphotic zone is the zone where light penetrates enough for photosynthesis to occur.
The bottom sediment, known as the benthic zone, has a surface layer abundant with organisms. Most of the organisms in the benthic zone are invertebrates, such as insect larvae or small crustaceans. Lakes with rocky bottoms have a greater biodiversity since they provide refuge from predators as well as a substrate for algae and invertebrates. Lakes with sandy bottoms have less nutrients and therefore lesser biodiversity.
Source:
Euphotic zone
Benthic zone

8. Lake organisms Creatures that go where ever they choose to go
Larger zooplanktons
fish
amphibians
Creatures that go where ever the water takes them
Living creatures – planktons
Animals: zooplanktons
Algae : phytoplankton
Bacteria : bacterioplankton
Dead creatures –Detritius
Internal: produced within lake
External: washed in from wash shed
Lentic organisms have special adaptations. For example, phytoplankton have vacuoles or flagella and the leaves and stems of plants have less woody tissue to help them stay afloat. The plants are usually flexible and bend with wind and flow of water.
Crustaceans, molluscs and insects are found in areas where there are more aquatic plants because these areas are rich in food and oxygen and are warmer than other parts. The plants also offer protection from predators.
Very few invertebrates are able to inhabit the cold, dark, and oxygen poor profundal zone (if present). Because the concentration of oxygen within this zone is low, species that are found there construct borrows in which they can hide and make the minimum movements so that they don’t expend much energy.
Creatures that live on the lake bottom
Animals
Aquatic insects, clams, snails
worms, cray fish
Bacteria and fungi
Sewage sludge
Plants
macrophytes
periphyton

9. The food chain in a lake PISCIVOROUS FISH PLANKTIVOROUS ZOOPLANKTON
NUTRIENTS
EAT
USE
RECYCLE
PISCIVOROUS
FISH
PLANKTIVOROUS
ZOOPLANKTON
ALGAE
BENTHIC
ORGANISMS
Photosynthetic organisms include algae suspended in the water (phytoplankton), algae attached to surfaces (periphyton), and vascular aquatic plants (macrophytes). Algae provide food and oxygen. Macrophytes provide food, oxygen and habitat.

10. Food and energy web in a lake
DECOMPOSERS
LOSS
THROUGH
OUTLET
LOST TO
SEDIMENTS
RECYCLED NUTRIENTS
TERITIARY CONSUMERS
SECONDARY CONSUMERS
PRIMARY CONSUMERS
PRIMARY PRODUCERS
OUTSIDE NUTRIENTS
SOLAR ENERGY
There are two basic life-sustaining processes in lakes, just as on land; photosynthesis and respiration. Green plants capture energy from sunlight to convert nonliving, inorganic chemicals (carbon dioxide, water, and mineral compounds) into living, organic plant tissue. Lake photosynthesizers include algae and macrophytes. Together, they are the primary producers, because they create the organic material required by most other organisms for nutrients and energy. Oxygen, the waste product of photosynthesis, adds to the oxygen supplied to the lake by the atmosphere.
These plants may die and decompose or be eaten by primary consumers – the second trophic level. This link in the food chain typically involves zooplankton grazing on algae but also includes larval fish eating zooplankton and a variety of invertebrates that eat attached algae (periphyton) and higher plants.
Other animals, such as small fish, secondary consumers (third trophic level) eat the primary consumers and thus are considered secondary consumers. Still larger consumers such as large fish, ospreys, and people are tertiary consumers (fourth trophic level). Thus, energy and nutrients originating from the photosynthetic production of biomass and energy cascade through the food web.
Excreted and dead organic material is consumed by decomposers which are microorganisms like bacteria and fungi.

11. 200m
10 degree C
700 to 1,000m
4 degree C
2000 to 1,000m
6,000m
Ocean zones
10,000m

12. Marine ecosystems Spread over 71% of the Earth’s surface Open sea
Coastal
Estuary and salt marshes
Coral reefs and mangroves
Each is a complex ecosystem
Producers, consumers and decomposers as
in other ecosystems