AP Environmental Science Aquatic Ecology Chapter 8 “The Water Zone”

Objectives for Aquatic Ecology Answer the following questions: What are the types of aquatic life zones? What factors influence the kinds of life found there? What are the types of saltwater and freshwater life zones? How is the aquatic environment being affected by humans ? How can we help sustain the water world?

Must Know for Aq. Biome Quiz Know descriptions of biomes Significant abiotic limiting factors Significant adaptations to LTD factors Trophic relationships Human factors

Aquatic Life Zones (Biomes) 1. The Saltwater or Marine life zone in the oceans of the world. 75% of world’s surface is water. 2. The Freshwater life zone includes the rivers, ponds, streams, lakes and wetlands.

Aquatic Life Zones in Ocean

Common Organisms in Aquatic Life Zones Nektons are swimming life forms. Plankton are organisms that float or only weakly swim. Benthos organisms are the bottom dwellers. Decomposers are the bacteria.

Plankton

Nekton

Benthos Things that crawl/swim at bottom of ocean

Unique Factors for water life Sunlight only penetrates the first 100 feet. Pressure increases greatly with depth Temperature drops quickly through thermoclines. Salinity of the water dehydrates cells. Buoyancy provides physical support. Nutrients and pollution are in the water so they are dissolved and diluted. Chemicals for life (O2) have to be taken out of solution.

Euphotic Zone of Ocean The zone of photosynthesis ( first 100 feet) Zone of CO2 absorption from the atmosphere. Oceans help clean the greenhouse gases out of the atmosphere. It turns the CO2 into carbonate ions that are stored in sediment of the ocean bottom. Dissolved Oxygen content varies widely from 1.5 ppm to 7.5 ppm.

Oceans 75% of Earth’s surface. Key role in environment. Hydrologic cycle starting point. Controlling factor in weather. Important chemical sink and cycle controller. Absorbs Heat from sun and redistributes it, regulating temperature. 250,000 known species of life. Two life zones: Costal and Open sea.

Coastal Zone Shore to end of continental shelf. 10% of ocean area: 90% of the life in the ocean. Site of large commercial fisheries. Site of most aquatic biodiversity: Reefs

Reef System in the Ocean

INTERTIDAL ZONE The area of shoreline between low and high tides is the intertidal zone. The organisms must be adaptable to the ocean or shore life because of changing conditions of salinity. They must also be able to hold on to rocks or sand when the waves crash on them.

INTERTIDIAL ZONE LIFE

Barrier Islands These are long, thin, low level, off shore islands of sediment that generally run parallel to the shore. They protect the mainland and estuaries, lagoons and coastal wetlands by dispersing the energy of approaching storm waves. Gentle waves build them up and storms flatten and erode them away.

REEF SYSTEMS Coral reef systems are a collection of many species co-habitat-ing in a mutualistic and sometimes synergistic relationship. These are the rain forests of the ocean. The most biologically diverse habitat in the ocean.

Effects of Mankind on Coasts 3.9 billion people (2/3 of world population) live along coasts or within 100 miles of a coast. Since 1900, the world has lost approximately half of the coastal wetlands by development. 55% of the USA wetlands and estuaries have been lost by development. This includes dredging and filling and waste contamination. California has lost 91% of its coastal wetlands.

Effects of Mankind on Reefs Mankind has killed 10% of the world’s reef systems. 30% are in critical condition. 30% are in threatened condition. Only 30% are stable. At current rates 60% of the world’s reefs could be dead in 20-40 years.

Open Ocean Biological Zones Open Sea zone has 3 vertical zones based on the penetration of sunlight. It contains about 10% of the marine species. Euphotic- First 200 meters. The upper zone, photosynthesis, high Dissolved oxygen, low nutrient levels, 90% of the oceans surface. Only 10% of commercial fish for the world. Bathyal- middle zone, 200-1500 meters, no photosynthesis. Lower Dissolved oxygen and colder. Pressure higher. Abyssal- bottom zone, totally dark, strange life forms. Lowest level of dissolved oxygen, coldest. Temp can be below freezing , but pressure keeps it liquid. Highest nutrient layer due to the sediments.

Marine Life Zones

Freshwater Life Zones Freshwater has < 1% dissolved salt concentrations. Lentic bodies of water are standing still, like ponds, lakes and inland wetlands. Lotic Systems are flowing bodies of water like streams and rivers. 41% of the world’s fish live in these waters. Easiest contaminated due to the surroundings.

Zones in Freshwater Lakes Zones are based upon depth and distance from shore. Each has different niches. Littoral zone – the shallow shoreline to the depth of plant growth. Most productive. Normal flora include phytoplankton and rooted plants (cattails, lilies, muskgrass). Normal fauna are fish, frogs, snails, insects and other consumers.

Zones in Freshwater Lakes Limnetic zone, is the open sunlit water surface layer away from the shore that extend to the depth penetrated by sunlight. The limnetic zone contains varying amount of phytoplankton, zooplankton and fish, depending on the nutrients available. Normal fish are the pikes, bass and bluegill.

Zones in Freshwater Lakes The Profundal zone is the deep open water zone that has no photosynthesis and is inhabitated by fish adaped to the cooler, darker water. The Benthic zone is the bottom of the lake and is inhabited mostly by decomposing bacteria and fungi, and some detritus feeding clams, insects and catfish.

Freshwater Lake Systems

Plant Nutrients in Lakes Science classify lakes according to their nutrient content and their primary productivity level. Oligotrophic lakes are mostly newly formed and has only a small supply of plant nutrients. Eutrophic lakes have a large or excess amount of plant nutrients. The plants grow and decompose to from bottom sediments. ‘These are mostly shallow and the water is brown and murky. They have a high net productivity and contain large populations of phytoplankton.

Plant Nutrients in Lakes

Regions of a River Upper Reaches: Middle Reaches: Lower Reaches:

Upper Reaches narrow V-shaped channel steep slopes water flow causes downward cutting through earth- canyons and valleys erosion Substrate is boulders, rocks, cobble rapids and waterfalls channel is shaded by riparian vegetation- water is cooler and temp. is consistent few nutrients- litter from outside the stream provides most of the energy species diversity is generally low

Middle Reaches wider channel that are U-shaped moderate slopes more aquatic plants floodplains have developed water flow causes bank cutting more sediment more nutrients more organisms temperature are more varied

Lower Reaches Wider channel Slower water flow Less changes in temperature Gentle gradient Wide valleys Wide flood plains Many meanders Increased depth and turbidity