Aquatic Ecosystems Chapter 54

In general…  Aquatic ecosystems are classified primarily on abiotic factors: temperature, salinity, dissolved oxygen, current temperature, salinity, dissolved oxygen, current These factors are often related to water depth These factors are often related to water depth  Three ecological categories of organisms: Plankton – at the mercy of current and waves: Plankton – at the mercy of current and waves: Phytoplankton – photosynthetic organismsPhytoplankton – photosynthetic organisms Zooplankton – heterotrophic protozoa and animalsZooplankton – heterotrophic protozoa and animals Nekton – stronger swimmers (fish) Nekton – stronger swimmers (fish) Benthic – live on or in the bottom (worms) Benthic – live on or in the bottom (worms)

Freshwater ecosystems  Flowing water  Headwater streams are usually shallow, fast- flowing, highly oxygenated. They depend primarily on detritus for energy input  Rivers – typically deeper, slower flowing, with less dissolved oxygen  Organisms in different locations are adapted accordingly, especially for O 2 levels and current

Freshwater ecosystems…  Standing-water ecosystems  Ponds and lakes  Large lakes can be divided into zones: Littoral zone – shallow area around shore; may contain emergent and nonemergent plants Littoral zone – shallow area around shore; may contain emergent and nonemergent plants Limnetic zone – deeper water; phytoplankton is the base of the food chain Limnetic zone – deeper water; phytoplankton is the base of the food chain Profundal zone – below the depth of light penetration Profundal zone – below the depth of light penetration  Thermal stratification may occur in temperate lakes and have areas of warm water over cold Thermocline – the zone of rapid temperature change Thermocline – the zone of rapid temperature change Turnover – in the fall and spring the waters mix Turnover – in the fall and spring the waters mix

Freshwater ecosystems…  Wetlands – transitional between aquatic and terrestrial ecosystems  Include hardwood bottomland forests, prairie potholes, and peat bogs, as well as swamps (with trees) and marshes (without trees)  Are important in flood control, breeding sites for birds, recharge of groundwater

Transitional ecosystems  Estuaries – where freshwater and salt water meet  Salt marshes – in temperate locations  Mangrove forests – in tropical areas  Undergo marked changes in temperature, salinity, current, and other abiotic factors  Extremely productive areas  Threatened by pollution and human population growth

Marine Ecosystems  Intertidal zone – transition between land and ocean between high and low tide  Highly productive but very stressful habitat

Marine ecosystems…  Benthic zone – ocean floor  Seagrass beds – flowering plants adapted to being submerged  Kelp forests – the largest brown algae  Coral reefs – very productive habitats; restricted to shallow water because coral polyps have a symbiotic relationship with photosynthetic zooxanthellae

Marine ecosystems…  Neritic province – shallow waters close to shore  Euphotic region – the lit zone where photosynthesis occurs  Phytoplankton  zooplankton  nektonic organisms

Marine ecosystems…  Oceanic province – most of the ocean; greater than 200 m deep  Marine ‘snow’ – organic debris that ‘rains’ down into the darker regions

Marine Ecosystems…  Overfishing is a threat Many commercially important fishes have reached commercial extinction due to overfishing Many commercially important fishes have reached commercial extinction due to overfishing  Pollution is also a threat Many of the world’s largest cities began as ports Many of the world’s largest cities began as ports Garbage has long been dumped in the sea Garbage has long been dumped in the sea