Aquatic, Coastal & Wetland Ecosystems

Final

Marine Ecosystems

Saltwater

• open water

• coastal

Freshwater Ecosystems

• lotic - flowing water (rivers and streams)

• Lentic - non-flowing water (ponds, lakes, wetlands

Hydrological cycle

what all aquatic ecosystems are linked directly or indirectly to 

ponds 

lentic - inland depressions that contain standing water 

Typically shallower and smaller than lakes 

• sunlight reaches that bottom in most areas 

• rooted plants to grow across much of the area 

Lakes

lentic - inland depressions that contain standing water 

Typically larger and deeper than ponds

• may have areas where sunlight cannot reach the bottom

• usually has distinct lake zones with thermal stratification

Glacial erosion and deposition

What lakes originate through

• kettle lakes

• pothole lakes

Kettle lakes

form when large chucks of glacial ice break off, become buried in sediment and later melt

pothole lakes 

formed where glaciers carved out a depression that later filled 

Rivers Damming Themselves with sediment

What lakes originate through

• oxbow lakes

Oxbow lakes

U-shaped body of water formed when a river meander becomes cut off from the main channel through erosion and deposition

Tectonic or Volcanic Activity

What lakes originate through

• tectonic Lakes

• Crater lakes

Tectonic Lakes

form by faulting or subsidence of of the earths crust

Crater lakes 

form in the caldera of extinct volcanoes 

Geological dissolution

What lakes originate through

• solution or sinkhole (karst) lakes

Solution or sinkhole (karst) lakes

form through the chemical dissolution of soluble bedrock

Non-geological activity 

What lakes originate through 

• lakes formed by beaver dams, human-created dams, quarries, and surface mines 

Littoral Zone

Lake Zonation

shallow, nearshore area

• where life is most abundant because sediments accumulate and keep water depth low, sunlight reaches the bottom, and plants provide food and habitat

Limnetic zone

Lake zonation

open water

• phytoplankton act as the main primary producers. Zoo plankton feed on the phytoplankton and are a key link in energy flow. Spring and fall turnover brings bottom nutrients to the surface which causes a phytoplankton bloom followed by a population decline once nutrients are depleted

• Fish make up most of the nekton and distribute themselves based on food, oxygen, and temperature

Profundal zone

Lake zonation

deeper water below the reach of sunlight

Benthic zone

Lake zonation

bottom of the lake

• contains organic debris that sinks from above or washes in from shore. Typically dominated by anaerobic bacteria and periphyton 

Oligotrophic 

characteristic of a lake tied to nutrient input and availability from the surrounding landscape 

low in nutrients, clear water, supports fewer plants and algae 

Mesotrophic

characteristic of a lake tied to nutrient input and availability from the surrounding landscape 

moderate nutrient levels with a balanced amount of plant and algal growth; intermediate clarity and oxygen

Eutrophic

characteristic of a lake tied to nutrient input and availability from the surrounding landscape 

high in nutrients, leading to dense plant and algal growth; often murky, with low oxygen in deeper waters due to decomposition

Dystrophic

characteristic of a lake tied to nutrient input and availability from the surrounding landscape 

brown, tea-colored lakes rich in organic acids; low nutrients, low pH, and limited productivity due to the types of trees (Florida)

Headwaters 

small, fast, and straight; often with rapids and waterfalls 

are of orders 1 to 3

Midstream

as the slope decreases, the stream slows down, begins to meander and deposits sediment

mouth

where the river empties into a lake or ocean. velocity drops sharply, sediment settles

Flowing-water ecosystems vary in structure and types of habitats by 

• streams often begin as springs, seeps, glacial melt, or as outflows from ponds and lakes 

  • as they move downhill, their path and flow are shaped by the landscape 

  • stream characteristics change as it moves from source to destination 

• As streams flow farther from their source, they grow larger and their physical features begin to shift 

• streams grow larger as they travel downstream and join with other streams 

  • a stream’s order increases only when two streams of the same order meet

First order stream

small headwater stream with no tributaries

seconds order stream

forms when two first order streams join

third order stream

forms when two second-order streams join

medium-sized streams

are of orders 4 to 6

Rivers

are of orders 7 to 12

Fast moving stream adaptations 

streamlined bodies to reduce drag 

flattened bodies and broad limbs that help insect larvae cling to rocks 

protective cases that anchor larvae to stones 

sticky underside in snails and planaria for gripping surfaces 

filamentous algae cling tightly substrate 

slow moving stream adaptations

Water moves gently, so organisms don’t need strong anchoring structures

tolerate lower oxygen and typically use gills or air-breathing strategies (siphons)

feed on fine organic particles (collectors, filter feeders)

live in soft bottoms (burrowers, detritivores)

support more plants and algae, providing food and habitat

Shredders

feeding role within stream ecosystem

break down leaves and coarse organic matter while feeding on the microbes growing on them

collectors 

feeding role within stream ecosystem

filter or gather fine particles created by shredders

Grazers

feeding role within stream ecosystem

scrape algae from rocks and other surfaces

Gougers

feeding role within stream ecosystem

burrown into waterlogged wood for food and shelter

predators 

feeding role within stream ecosystem

insect larvae and fish that feed on grazers and detrital feeders 

River Continuum Concept

feeding group thrives under different conditions, their abundance changes predictably from headwaters to midstream to downstream

basin wetlands

form in low depressions such as shallow basins or former lakes; water mainly moves up and down (vertical flow)

riverine wetlands

occur along rivers and streams; periodically flooded and have one-way downstream flow

fringe wetlands

found along the edges of large lakes; influenced by rising and falling lake levels with back-and-forth flow (bidirectional)

hydrophytic plants

adapted to grow in water or oxygen-poor saturated soils

Obligate

must have very saturated soil

facultative

can grow in wet or dry soils

marshes

wetlands dominated by emergent herbaceous vegetation

Wetland grassland – reeds, sedges, grasses, cattails

swamps

forested wetlands

deepwater tree dominated - cypress, tupelo, swamp oak

shrub dominated - alder, willows

riparian woodlands

occasionally or seasonally flooded by river waters

peatlands

are wetlands where organic matter (peat) builds up over time

fed by ground water = fens

rely on rainwater = bog

salt marsh

occur in temperate latitudes where coastlines are protected from wave action

low marsh

seaward edge. Dominated by tall cordgrass, which tolerates high salinity and has hollow stems that move oxygen to the roots.

high marsh

Flooded only at high tides; supports short cordgrass and other plants, which are less salt tolerant

Mangroves

sediment accumulates, wave action absent, prop roots for support, pneumatophores take in O2

estuary

A semi-enclosed part of the coastal ocean where freshwater joins saltwater

The countercurrent traps nutrients with vertical mixing, making them highly productive nursery habitats

rocky coast

erosional landforms where the interface between land and sea is made of hard, resistant rock. Found along active continental margin

sandy coast

form when rocks inland and along coast break down into tiny pieces from wave action. Rivers and waves can carry this material and deposit it along shoreland as sand.

Epipelagic zone

sunlit top layer

phytoplankton

mesopelagic zone

twilight second layer

zooplankton

Describe the roles of phytoplankton and zooplankton

Zooplankton feed on phytoplankton and key link in energy flow. Spring and fall turnover brings bottom nutrients to the surface which causes a phytoplankton bloom followed by population decline once nutrients are depleted. Dead phytoplankton and zooplankton fall to bottom where they become the nutrients later pulled up to the surface

Microbial loop

small-scale food chain within plankton

Photosynthetic nanoflagellates and cyanobacteria are responsible for a large part of photosynthesis in the sea

Heterotrophic bacteria feed on wastes produced by these organisms

Heterotrophic nanoflagellates eat the bacteria and pass energy up the food chain

Explain how excess nutrients lead to algal blooms, oxygen depletion, and the formation of coastal dead zones

Productivity in oceans is linked to light and nutrients

Thermocline blocks nutrients from rising so productivity depends on seasonal mixing (when the thermocline breaks down) and upwelling (the bringing of nutrient rich waters from the deep to the surface

Any extra nutrients that human activities bring (fertilizer) boosts nutrients in a negative way that leads to large phytoplankton and algae blooms. Eventually the excess dies and falls to the floor where they are broken down by bacteria which depletes oxygen throughout the whole pelagic zone rather than just the benthic zone. This creates a dead zone where nothing can survive.