Aquatic ecosystems

Determinants of community composition in aquatic ecosystems

• Salinity
• Light penetration
• Dissolved oxygen
• Nutrients
• Temperature
• pH
• Flow

Types of marine organisms

• Plankton
  • Phytoplankton
  • Zooplankton
• Nekton
• Benthos

Rivers

Threats to rivers

• Non-point-source pollution
• Siltation
• Dam

Freshwater lakes

Thermal stratification

Threats to lakes

• Rivers tend to flow into lakes
• Water withdrawals

Wetlands

• ``[S]hallow ecosystems in which the land surface is saturated or submerged at least part of the year''
• Contain vegetation adapted to grow in these saturated environments
• Legal definition is critical due to disproportionate importance of wetlands

Types of wetlands

Swamp

(Forested wetland) Wetlands dominated by trees; high biological productivity; high nutrient levels

Marsh

Wetland dominated by grasses and other vegetation; high biological productivity; high nutrient levels

Bog

Area of water-saturated ground, fed by precipitation; containing layers of undecayed vegetation (peat); low biological productivity; low nutrient levels

Fen

Area similar to bog, but fed by groundwater

Forested wetland

Marsh

Bog

Threats to wetlands

• Urban sprawl
• Development
• Agriculture
• Pollution
• Pest eradication

Estuaries

• Combination of factors place them among the most fertile ecosystems:
  1. Rivers carry terrestrial nutrients into the estuary
  2. Tidal action promotes rapid nutrient cycling and waste removal
  3. Significant light penetration into shallow water
  4. Numerous plants act as primary producers and trap detritus
• Critical habitats for fish and other organisms

Salt marsh

Mangrove forest

Threats to estuaries

• Coastal development
• Pollution
• Aquaculture

Marine life zones

• Intertidal environment
  • Supratidal zone
  • Intertidal zone
  • Subtidal zone
• Pelagic environment
  • Neritic province
  • Oceanic province
• Benthic environment

Intertidal environment

Pelagic environment

Benthic environment

• Seagrass bed -- less than 10 m, high primary productivity, food and habitat source
• Kelp forest -- approximately 25 m along rocky shorelines, habitat and indirect food source (through decomposition)
• Coral reef -- warm, shallow water with year-round sunlight (cold-water reefs also exist), water may be nutrient poor
  • Fringing reef
  • Atoll
  • Barrier reef

Seagrass bed

Kelp forest

Coral reef

Fringing reef

Atoll

Barrier reef

Threats to the ocean

• Non-point-source pollution
• Point-source pollution
• Invasive-alien species
• Overharvesting
• Bycatch
• Aquaculture
• Coastal development
• Habitat destruction
• Climate change