Aquatic Ecology: Biodiversity in Aquatic Life Zones G. Tyler Miller’s Living in the Environment 13th Edition Chapter 7
Key Concepts Factors that influence aquatic systems Saltwater life zones Freshwater life zones Human activities that affect aquatic systems
Aquatic Environments: Types Aquatic Life Zones – aquatic equivalents of biomes. Organisms in each determined by salinityThere are two major types: Marine and Freshwater Marine systems – salt water environments primarily composed of oceans, mangrove swamps, coastal marshes, coral reefs, and estuaries Freshwater systems – primarily lakes, ponds, rivers, streams and inland wetlands Fig. 7-2 p. 145
Aquatic Environments: Components Phytoplankton – photosynthetic plant plankton Producers that support most aquatic food chains. (Ex. cyanobacteria and algae) Zooplankton – nonphotosyntheticanimal plankton Consumers. Primarily feed on phytoplankton or other zooplankton Nekton – strong swimming consumers such as fish, turtles, & whales Benthos – bottom-dwellers such as shell fish, worms, & crustacean Decomposers – mostly bacterial that break down organic compounds in dead bodies of marine organisms
Key Characteristics: advantages and disadvantages Physical boundaries fluid, less fixed than terrestrial . Difficult to count and manage More complex and longer food chains/webs More difficult to monitor and study
LIMITING FACTORS Depth: surface, middle, bottom Euphotic zone: (light) photosynthesis Oxygen: enters system via photosynthesis and absorbed from atmosphere. Can be reduce by algae blooms Carbon dioxide: from aerobic respiration of consumers, decomposers and atmosphere; provides CO2 sink; form CO3(carbonate ions) in form of CaCO3 of sand, sediments, shells
Dissolved Oxygen Depends On: – enters aquatic systems from interface with atmosphere and through photosynthesis by producers. Varies by…. Temperature Number of producers releasing oxygen Number of consumers removing oxygen Deep ocean circulation (can cause oxygen rich water to sink and spread) DO under 5ppm = death to many fish
Nutrient supply Shallow water: supplies plenty due to presence of primary producers Deep water: nutrients dependent on upwellings for nitrates, phosphates, iron. Limits NPP Benthos: slow growers/reproducers due to limited nutrients. Vulnerable to overfishing
Planet OCEAN? Saltwater 71% of surface Oceans make up 99.5% of world’s habitable space 250,000 animal and plant species Supply both ecological and economic benefits 5% explored!
Major biological life zones COASTAL OPEN SEA Warm, nutrient-rich, shallow Extends from high-tide region to shallow edge of continental shelf Human activity is high 90% of all marine species;10% of ocean’s area Ample amounts of sun and nutrients. Euphotic: photosynthesis/low nutrient levels Bathyal: dim, no photosynthesis Abyssal: dark; cold; little DO; enough nutrients to support 98% of species
Saltwater Life Zones(Coastal) Coastal zone (a.k.a. Neritic Zone) – warm, nutrient rich, shallow water that extends from high-tide mark to the shallow edge of the continental shelf. Highly affected by human activities.Makes up less than 10% of ocean volume but has 90% of all marine species. Ample supplies of (1) sunlight and (2) plant nutrients Estuaries & Coastal Wetlands – highly productive areas in coastal zone. A partially enclosed area of coastal water where seawater mixes with fresh water and nutrients from rivers and streams. These include (1) river mouths, (2) inlets, (3) bays, (4) sounds, (5) mangrove forest swamps and salt water marshes. Intertidal zones – rocky sand shores that make up the area between high and low tides. Organisms here must be able to withstand varying levels of sunlight, water, temperature and stress. Barrier islands – long, thin, low offshore islands of sediment that run parallel to shore and serve to disperse energy from storm waves.
Aquatic Biological Zones(Open Sea) : based on light penetration Euphotic Zone – upper layer of aquatic zones beyond the continental shelf through which light can penetrate permitting photosynthesis to occur. Nutrient levels are low except around areas of upwelling. Populated by large, fast-swimming predatory fish. Bathyal Zone (a.k.a. Transitional Zone) – dimly lit middle zone that begins at a depth of approximately 200m. Does not contain photosynthetic producers due to lack of light. Populated by zooplankton and small fish which migrate to the surface at night to feed. Abyssal Zone – very deep cold and dark section of the ocean which begins at a depth of about 1,500m. Has little dissolved O2 but ample supply of nutrients in sediment on the ocean floor.
Ocean Zones Fig. 7-7 p. 148 Refer to Figs. 7-11 & 7-12 p. 151 & 152
Coral Reefs? Coral reefs Warm coastal waters Marine equivalents of tropical rainforest (Fig. 6-1a) Polyps (jellyfish relative), CaCO3, symbiotic zooxanthellae(single cell algae) 0.1% of world’s ocean area Ecological and economic services Moderate atmospheric temperature(remove CO2) Natural barriers protective 15% of world’s coastline Provides habitats for marine organisms Produce one-tenth of global fish catch Building materials for poor countries Ecotourism
Coral Reefs: Transfer of Energy Fig. 7-16 p. 154
Impacts of Human Activities on Marine Systems: Red Alert Humans have an affinity for the coast: 40% of people on planet live within 62 miles of a sea coast. By 2030 6.3 people will live near a coast. Ecological and economic services being degraded or destroyed. Sea marshes, estuaries are now golf courses, shrimp farms, marinas By 2080 half of coastal wetland will be lost to agriculture and urban development, rising seas Lose of mangrove forests due to clearing. 35% of world’s original forests lost since 1980 due to development, rice fields,aquaculture
Benefits of marine systems:Ecological Economic Climate control CO2 absorption Nutrient cycling Waste treatment and dilution Reduced storm impact Habitats and nurseries Scientific info Biodiversity &genetic resources Food & Animal feed Pharmaceuticals Harbors & transportation Coastal homes Recreation & jobs Oil, minerals, building materials
Freshwater Life Zones • Concentrations of dissolved salt is less than 1% by volume • Account for less than 1% of Earth’s surface water • Runoff is the primary source of freshwater and carries both organic and inorganic materials as well as pollutants Fig. 7-20 p. 158
Freshwater Aquatic Life Zones Lentic (standing) – standing bodies of fresh water such as lakes, ponds and inland wetlands. Lotic (flowing) – flowing bodies of fresh water such as streams and rivers. Life Zones in Freshwater Lakes(defined by depth/distance from shore) Littoral Zone – shallow sunlit water near shore up to where rooted plants stop growing . High bio activity Limnetic Zone– open sunlit surface water away from near shore extending to the depth reached by sunlight. Contains photosynthetic producers. Prod. Food/O2 Profundal Zone– deep, cool, open water too dark for photosynthesis. O2 levels are low. Benthic Zone– lake bottom. Inhabited by organisms which tolerate cool temperatures and low O2 levels
Types of Lakes: Oligotrophic/Eutrophicclassified by nutrient content and Primary productivity Fig. 7-21 p. 158 Oligotrophic– state of being poorly nourished, often seen in newly formed lakes: small pop. of phytoplankton, crystal clear, deep, steep banks, low NPP
Types of Lakes: Eutrophic Fig. 7-21 p. 158 Eutrophic – state of being well nourished; shallow, murky brown ; high NPP, little DO at bottom in warm months Cultural Eutrophication – eutrophication that is accelerated due to the impact or activities of humans
Seasonal Changes in Lakes due to thermal stratification(Water is densest at 4C(39F); which is why ice floats! (ice = 0C) Epilimnion– upper layer of warm water w/high dissolved O2 Thermocline– temperature changes rapidly with depth, moderate dissolved O2. Acts as barrier in summer. Keeps nutrients and DO from the hypolimnion Hypolimnion– lower layer of cold, dense water w/low concentration of dissolved O2. Fall & Spring Overturn – surface temperature changes causes convection currents that reduce temperature and O2gradient; brings nutrients to surface Fig. 7-22 p. 159
River Systems Fig. 7-23 p. 160 Runoff – precipitation not evaporated or absorbed into ground Watershed or Drainage basin – land area that delivers runoff, sediment, and dissolved substances to a stream Source Zone: High DO, pop. by cold water fish Transition Zone: supports more producers, warmer waters, bl. Bass Floodplain Zone: high temp. less DO, lg. pop. of algae and cyanobac.
Wetlands Def. -lands covered by water all or most of the time excluding lakes, reservoirs, streams Include: Marshes: few trees Swamps: trees, shrubs Prairie potholes: depressions from glacial carvings Floodplains: excess rain flood Bogs and fens: waterlogged soils, peat Wet arctic tundra(in summer)
Inland Wetlands: cover with freshwater all or part of time Provide water quality and and flood control protection Worth billions of $$/year Fig. 7-25 p. 162
Human Impact on Marine & Freshwater Systems: Approximately 40% of the worlds population lives on or within 100km of a coast. This is expected to more than double by 2030. Clearing Wetlands and Estuaries for agricultural use or real estate development Beaches are eroding due to coastal development and rising sea levels Ocean bottom habitats are being degraded due to seaway dredging and the harvesting of bottom fish and shellfish Almost 60% of the world’s 237 large rivers are fragmented by dams, diversions, or canals Levees and dikes built for flood control alter aquatic habitat and disconnect rivers from floodplains eliminating wetlands typically used as spawning grounds for fish In US, 53% of wetlands from 1600 have been drained, filled or covered up
Sustainability of Aquatic Life Zones • Everything is connected! • Bad News: The human impact on each rivers, stream, and lake reflects the cumulative effect of all that occurs within their watershed. Ultimately, these nutrients, wastes and pollutants end up running into the ocean. • Good News: Aquatic life zones are highly resilient provided that they are not overloaded with pollutants or overfished. • Hydrologic process can purify water • Nutrients cycle in and out • Populations can be replenished given the opportunity • We still need to improve our understanding of how • How our activities impact Earth’s biodiversity and, • What we can do to live more sustainably
Sustainability All water leads to the ocean; therefore anything that enters water systems affects ocean life. Water can: be naturally purified by hydrologic processes; allow nutrients to move in and out; populations can replenish themselves with time and opportunity. EVERYTHING IS CONNECTED!!