APES Notes: Aquatic Biodiversity Key Factors Determining Biodiversity in Aquatic Systems Types of Organisms Phytoplankton Plankton Zooplankton Nekton Benthos Decomposers Ultraplankton MARINE Biological Zones in the Open Sea • Euphotic zone: brightly lit surface layer. – Nutrient levels low, dissolved O2 high, photosynthetic activity. • Bathyal zone: dimly lit middle layer. – No photosynthetic activity, zooplankton and fish live there and migrate to euphotic zone to feed at night. • Abyssal zone: dark bottom layer. – Very cold, little dissolved O2. Estuaries and Coastal Wetlands: Centers of Productivity • Estuaries and coastal marshes provide ecological and economic services. – Filter toxic pollutants, excess plant nutrients, sediments, and other pollutants. – Reduce storm damage by absorbing waves and storing excess water produced by storms and tsunamis. – Provide food, habitats and nursery sites for many aquatic species. Pelagic/Open Sea Zones Netritic Oceanic Abyssal FRESHWATER 1. Lakes & Ponds Lake - Large natural bodies of standing water formed when precipitation, runoff, or groundwater seepage fills depression in earth’s surface. Ponds – Shallow, Sunlight penetrates, usually only one zone. Plant Nutrients Oligotrophic Poorly nourished - clear Mesotrophic Moderately nourished Eutrophic well nourished – excessive plant growth Cultural Eutrophication: 2. Rivers & Streams Zones Source (headwaters) Transition Floodplain 3. Marshes & Swamps Marshes & Swamps: Covered by shallow water at least part of the year. Waterlogged, anaerobic, rich in organic material Marshes: Swamps: Importance of Wetlands: Human Impact • Fragmentation by dams, diversions, or canals • Flood control levees and dikes – Alter or destroy aquatic habitats – Disconnect rivers and floodplains – Eliminate wetlands • Draining or filling of wetlands • Cities and farmlands add pollutants and excess plant nutrients to streams and rivers.