Biosphere & Biomes: Aquatic Biomes

Define aquatic biomes

- Aquatic biomes are biomes under water

- They are characterised by their physical (pattern/speed of water, nearby landforms & climate) and chemical (fresh/salt water) enviroments

List 3 basic facts about aquatic biomes

- Marine biomes have a salt concentration of 3%

- Freshwater biomes have a salt concentration of less than 1%

- Aquatic biomes cover 70-75% of the earth

Give a simple overview of the zonation aquatic biomes

Photic zone

- 200m and above

- Has light

(photosynthesis can occur)

- Where most organisms are

Aphotic zone

- No light

- Below 200m

Benthic zone

- The seafloor of the whole ocean (abyssal to photic)

- Organisms in this zone are called benthos

Abyssal zone

- Right at the bottom of the sea

- Has freaky fish that have evolved to high pressure

- A lot of nutrients come from dead things falling down (called detritus)

Does water temperture in aquatic biomes change significantly?

No

- This is becuase water changes temp slowly, which means it never fully heats up

- Pressure is the main thing that changes significantly

What is a thermocline?

- Thermal stratification

- Caused by hot water rising to the surface

- When the warm upper layer of water seperates from the cold deeper layer of water

^ typically happens in summer bc of high terrisitral temp

- Apart of process called semi-annual mixing (water mixes in spring & autumn, thermocline in summer and top layer frozen in winter)

Name the types of terrisitral biomes

- Lakes

- Wetlands

- Streams & rivers

(streams lead into rivers)

- Estuaries

- Intertidal zones

- Ocean pelagic zone

- Coral reefs

- Marine benthic zone

Lakes

- Anything from small pond to big lake

- Enclosed by land

- Seasonal lakes have seasonal thermocline vs tropical-lowland lakes have year round thermocline

Oligotrophic lakes

- Nutrient poor

- O2 rich (due to less life bc ↓ no of nutrients)

Eutrophic lakes

- Too much nutrients

- More likely to have thermocline

- O2 depletion due to lots of life (algae)

Wetlands

- Inundated by water some of the year

- Plants are well adapted to water-saturated soils

- Rapid organic production and decompisition

- Developed in shallow basins, along flooded riverbanks

- Wetlands are VERY important, they purify water and help reduce the impacts of flooding

- 90% of NZ wet lands have been built over:(

Streams & rivers

- Streams typically start at high altitudes (bc of rainfall)

- Fast moving current, lots of H20, little nutrients (as has not travelled far)

- Streams connect together and form rivers

- Rivers are slower moving, warmer and have more nutrients

- Stones on the bottom of rivers are very important as they provide home for small fish

DN↓

if there is a build up of silt (can happen from damming/changing river flow/loss of ripirain vegitation) then habitat is lost=fish die

Estuaries

- Intertidal zone w freshwater influence

- Transition between river and sea (freshwater and saltwater)

- Salinity changes a lot due to tides going in/out

- Water lvl changes a lot bc of tide going in/out

^ Organisms that live here have to be well adapted to water/salinty changes

- Plants grow well bc high light exposure

- Nutrient rich & highly productive

- Saltmarsh grasses and algae are major producers

Intertidal zones

- Where tides go in/out in a 12 hour pattern

- Lots of O2 and nutreints

- Between marine & terristiral enviroment

- Organisms have to be adapted to being periodically submeraged/exposed

- Beach/coastline

- Lots of life lives on rocks

- Made from what was valleys/harbours in the ice age but got covered by water

Ocean pelagic zone

- The top of the sea

- Constantly mixed by wind driven currents

- O2 lvls tend to be high

- Generally photic

- Seasonal turnover in temperate oceans renews nutreints in the photic zones

- Year-round thermal stratification (thermocline) in tropical oceans causes ↓ nutrients in top of photic zone

- Covers 70% of the earth

Plankton in the ocean's pelagic zone (DN)

- Phytoplankton and zooplankton are the dominant organsims in this zone

- They account for 50-85% of photosynthesis in the world

- Provide a carbon sink (like coral reefs)

Coral reef

- Formed from the calcium carbonate skeletons of corals (cnidarians)

Shallow reefs

- Occur in the photic zone in warm (20-30ºC), clear water

Deep sea reefs

- Corals live at 200-1,500m (aphotic zone)

- Corals requires high oxygen conc. and soild substrate (rock) for attachment

- Coral has a mutalisitc relationship w unicellular algae (provides them w organic molecules/nutrients

- Die easily from high temp

How are coral reefs formed? (DN)

- Corals need hard substrate to attach

- Volcano is hard

- Coral attach to volcano/volcanic island

- Volcano gradually sinks

- Coral reef remains

Marine benthic zone

- The seafloor of below surface water (costal to deepsea)

- Organisms at the very deep benthic (abyssal) zone experience VERY high pressure

^ also there is little nutrients (mainly dead stuff from above layers) and light

- Shallow (photic) waters contain seaweed and algae

- Substrate is mainly soft sediment+some rocks

- Threatened by fishing (particually deepsea trawling)

Describe deepsea hydrothermal vents (DN)

- Come from volcanos (warmth is provided)

- Found in mid-oceanic ridges (junctions between continental plates)

- Life includes chemoautotrophic prokaryotes, echinoderms and arthropods