Aquatic Ecosystems Ch. 7

Aquatic Ecosystems Temperature, sunlight, oxygen, nutrients determine where organisms live 3 groups of organisms Plankton- drifters, can’t swim against current – base of the food chain (phytoplankton=plants that serve as base of food, jellyfish (zooplankton) Nekton – free swimming organisms (fish, turtles, whales) Benthos – bottom dwellers, usually attached to hard surfaces (mussels, worms, barnacles)

Section 7-1: Freshwater: Lakes and Ponds Low salinity (salt) in water Form naturally where groundwater reaches the surface or where men or beavers dam up streams and rivers Littoral zone – near the shore, lots of sunlight, rich in nutrients, diverse and abundant life Benthic zone – bottom, inhabited by decomposers, insect larvae, clams Eutrophication – an increase in the amount of nutrients in a lake Large amount of algae and plant growth Decomposers (bacteria) use up the oxygen and kill out other organisms Accelerated by runoff

Freshwater: Wetlands Most are in the SE United States Areas of land covered with freshwater at least part of the year Marshes – non-woody plants Swamps – trees and shrubs

Freshwater Wetland: Environmental Functions Act as filters by absorbing and removing pollutants from water, improving water quality downstream Controls flooding by absorbing overflow from rivers Spawning area for freshwater game Habitat for native and migratory birds

Marshes Florida Everglades – largest wetland in US Occur in low flat lands with little water movement Plants root in rich bottom sediments and stick out above water Benthic zones are very rich in nutrients Salinity varies – some are brakish while others can be salty

Swamps Occur on flat, poorly drained land, often near streams Salinity varies and determines which species live there Ideal for amphibians, birds and reptiles

Human Impact on Wetlands Once thought of as wastelands and breeding grounds for insects Many have been drained, filled and cleared for development Florida Everglades once covered 8 million acres but now only covers 2 Vital functions of wetlands now recognized Government protects many wetlands

Freshwater: Rivers Begin at headwaters – usually snowmelt in the mountains Water flows fast and contains a lot of oxygen and is cold Downstream it becomes warmer, wider, and slower with more vegetation and less oxygen Life in a river – Near headwaters – mosses anchor to rocks, trout and minnows Downstream – plants root into the sediment, Catfish and carp in the calmer water

Section 7-2: Marine Ecosystems Coastal Wetlands – covered by salt water all or part of the year Provide habitat and nesting for birds and wildlife Protects from flooding by absorbing excess rain Filter out pollutants and sediments Provide recreational areas

Estuaries Area in which fresh water from a river mixes with salt water from the ocean Nutrient traps – currents cause nutrients and mineral- rich mud to fall to bottom Producers use nutrients to grow in the mud Always receiving fresh nutrients = super productive ecosystem

Plants and animals in estuaries Ecosystems support many organisms Lots of sunlight for photosynthesis Lots of nutrients from ocean and river Shallow water Organisms can tolerate variations in salinity because the salt varies with the mixing of ocean water and fresh water Plants, plankton, fish, dolphins, manatees, otters, oysters, clams and barnacles

Threats to estuaries 6 of the world’s 10 largest cities were built on estuaries Protected harbor, access to ocean and river Used as solid waste landfills then building sites Pollution from sewage, industrial waste, and agricultural runoff Estuaries cannot cope with excessive amounts of pollution caused by dense human populations

Types of estuaries Salt marshes – estuaries where rivers deposit mineral mud Supports clams, fish, aquatic birds, young shrimps, crabs Barrier Islands: run parallel to sandy shores and protect the mainland from storms and waves Mangrove swamps – swamps with a lot of mangrove trees in them (trees that can grow in shallow salty water) – above ground roots Protect shoreline from erosion and damage from storms Over 2,000 animal species Tropical and sub-tropical areas

Using the picture, list the biotic and abiotic factors in this marine ecosystem. Explain why an estuary is such a productive ecosystem.

Coral reefs Limestone ridges built by tiny coral animals One of the most diverse ecosystems in terms of the kinds of life there Found in clear, shallow tropical seas because they need warm salt water with enough light for photosynthesis Outer layer of reef contains living coral, inner layers are skeletons Coral animals sting their prey as they float by

Dangers to the reef Fragile ecosystem Can be harmed by Water temp that is too hot or too cold Muddy, polluted, or nutrient rich water (not enough light for photosynthesis) Coral bleaching – coral turns white when algae the live in the coral leave or die Occurring often enough will lead to death of coral 50% of today’s reefs are in danger of destruction Reefs grow too slowly to repair themselves from damage

Oceans Water absorbs sunlight down to about 100m Most of the life is in the shallow coastal waters where sunlight reaches bottom and river nutrients wash in Ocean surface – plankton, nekton (swimmers) Deep ocean – no sunlight, organisms depend on food that drifts down from above – Benthos (decomposers, filter feeders)

Threats to ocean Runoff pollution Sewage, city wastes, industrial wastes Overfishing, fishing methods (nets that tangle animals)

Closure Describe the abiotic and biotic factors of the coral reef and ocean ecosystems. Explain how these ecosystems are threatened.