Chapter 8 - Aquatic Environments
A. Saltwater and freshwater cover 71% of the earth’s surface.
B. Salinity of the water determines the major types of organisms in aquatic environments.
C. Four major types of organisms in aquatic systems:
1. Plankton are free-floating, generally one-celled organisms.
Three major types of plankton: phytoplankton (plant plankton), zooplankton (animal plankton) and ultraplankton - photosynthetic bacteria – 2 micrometers wide.
2. Nekton - fish, turtles and whales
3. Benthos are bottom dwellers - barnacles, oysters, worms, lobsters and crabs
4. Decomposers
D. Three layers of aquatic life zones: surface, middle, bottom.
1. Temperature, sunlight, dissolved oxygen D.O., and nutrient availability determine types and numbers of producers found in these zones.
2. Photosynthesis is confined to the upper layer – euphotic zone or photic zone – at lower depth respiration from animals replaces photosynthesis
Turbidity –cloudiness of water. Can be caused by algal blooms in the euphotic zones of lakes
*List the ecological an economic services of marine ecosystems
Saltwater Life Zones
A. Oceans have three major life zones: coastal and open ocean
1. The coastal zone interacts with the land – highly affected by human activities.
- High NPP per unit area - 10% of the oceans and 90% of all marine species.
- sunlight and nutrients flow from land.
- extends from top of high water mark out to the edge of the continental shelf.
- subject to tidal rhythms, runoff from land, and seawater that mixes with freshwater and nutrients.
- Mangrove forest swamps grow in sheltered regions of tropical coasts.
- estuaries (where rivers and sea meet) make nutrients available due to constant stirring of bottom sediment.
- they filter toxic pollutants, filter excess plant nutrients, reduce storm damage and provide nursery sites for aquatic species.
- 1/3 have already been lost by degradation.
- Intertidal zone – area of shoreline between high and low tide organisms need several adaptations for this habitat (waves, temp, salinity) and have specialized niches (pg. 131- 133) –
Barrier beaches – gentle sloping and sandy
- Barrier islands are low, narrow sandy, islands that form offshore from a coastline.
These help protect the mainland, estuaries, and coastal wetlands from heavy storm damage.
(list the various issues with people living on these islands).
- Coral reefs in shallow coastal tropical oceans support a very diverse ecosystem.
- They grow slowly and are vulnerable to damage.
- Coral bleaching occurs if temperature increases 1degree over maximum range
(List the various threats to coral reefs)
2. The open sea is divided into vertical zones based on light.
a. The euphotic zone - floating phytoplankton carrying on photosynthesis – low nutrient levels
D.O. level is high. swordfish, shark and bluefin tuna.
b. The bathyal zone is the dimly lit middle zone; no producers. Zooplankton and smaller fish
3. The abyssal zone is dark, very cold with little dissolved oxygen. The nutrients from above –marine snow – feed deposit feeders and nutrients on the ocean floor – feed filter feeders.
hydrothermal - specialized bacteria feed on chemical nutrients
*Low average primary productivity and NPP occurs, but oceans are so large they make the largest contribution to NPP overall.
* 45% of the world population lives along coasts. Over half of US population lives near the coast.
List natural capital degradation of marine ecosystems
Freshwater Life Zones
Standing (lentic) bodies - lakes, ponds and wetlands
Flowing (lotic) systems - streams and rivers.
*List the ecological and economic services of Freshwater ecosystems
Lakes - feed by rainfall, melting snow, streams
Four zones
Littoral area near shore with rooted plants
Limnetic zone is open, sunlit water near shore most productive area for food and oxygen production.
Profundal zone is deep open water too dark for photosynthesis less oxygen.
Benthic zone -decomposers and detritus feeders. Sediment washing and dropping detritus feed this area.
Deep layers become stratified by temperature – no mixing
During fall and spring turnover of water brings up nutrients, re-oxygenates bottom levels, and evens out water temperature.
Lakes are described by amount of plant nutrients.
oligotrophic lake
eutrophic lake
mesotrophic lakes
Streams
Watershed - surface water flows into streams and rivers and the area it drains
Three aquatic life zones along stream flow
1. source zone
- narrow and fast moving.
- large amounts of oxygen from air
- plants are attached to rocks. not very productive.
- fallen debris from trees add most productivity
2. The transition zone
- wider, deeper streams, flow down gentler sloped.
- warmer, with more nutrients and support more producers – more algae
- slightly lower dissolved oxygen.
3. The floodplain zone
- wider, deeper rivers
- water temperature is warmer, less dissolved oxygen is present and flow is slower
- large numbers of producers such as algae, cyanobacteria, and rooted plants.
Streams are fairly open ecosystems and receive many nutrients from surrounding lands.
(List some of these sources)
Inland wetlands - swamps, marshes, prairie potholes, floodplains
- number of days of saturation, soil type, and vegetation determine wetland
- wetlands provide ecological services such as filtering toxic wastes/pollutants, absorbing/storing excess water from storms and providing habitats for a variety of species.
· List the four major impacts humans have on freshwater ecosystems
Ø Cultural eutrophication:
l Human inputs of nutrients from the atmosphere and urban and agricultural areas can accelerate the eutrophication process – runoff of fertilizers, livestock, sewage – excess algae – die and decomposers use up oxygen
11
Aquatic Biodiversity