Chapter 6 Aquatic Biodiversity

Why should we care about coral reefs? Figure 6.1 Natural capital: a healthy coral reef in the Red Sea covered by colorful algae (left) and a bleached coral reef that has lost most of its algae (right) because of changes in the environment (such as cloudy water or too warm temperatures). With the algae gone, the white limestone of the coral skeleton becomes visible. If the environmental stress is not removed and no other alga species fill the abandoned niche, the corals die. These diverse and productive ecosystems are being damaged and destroyed at an alarming rate. Fig. 6-1a, p. 126

Why should we care about coral reefs? Figure 6.1 Natural capital: a healthy coral reef in the Red Sea covered by colorful algae (left) and a bleached coral reef that has lost most of its algae (right) because of changes in the environment (such as cloudy water or too warm temperatures). With the algae gone, the white limestone of the coral skeleton becomes visible. If the environmental stress is not removed and no other alga species fill the abandoned niche, the corals die. These diverse and productive ecosystems are being damaged and destroyed at an alarming rate. Fig. 6-1b, p. 126

Why Should We Care About Coral Reefs? Help moderate atmospheric temperature by removing CO2 from the atmosphere. Act as natural barriers that help protect 14% of the world’s coastlines from erosion by battering waves and storms. Provide habitats for a variety of marine organisms.

Harbors and transportation routes Natural Capital Marine Ecosystems Economic Services Ecological Services Climate moderation Food CO2 absorption Animal and pet feed Nutrient cycling Pharmaceuticals Waste treatment Harbors and transportation routes Reduced storm impact (mangroves, barrier islands, coastal wetlands) Coastal habitats for humans Figure 6.4 Natural capital: major ecological and economic services provided by marine systems. Scientists estimate that marine systems provide $21 trillion in goods and services per year—70% more than terrestrial ecosystems. QUESTION: Which two ecological services and which two economic services do you think are the most important? Habitats and nursery areas Recreation Employment Genetic resources and biodiversity Oil and natural gas Minerals Scientific information Building materials Fig. 6-4, p. 129

AQUATIC ENVIRONMENTS Saltwater and freshwater aquatic life zones cover almost three-fourths of the earth’s surface Figure 6-2

AQUATIC ENVIRONMENTS Saltwater and freshwater aquatic life zones cover almost three-fourths of the earth’s surface Figure 6-3

What Kinds of Organisms Live in Aquatic Life Zones? Aquatic systems contain floating, drifting, swimming, bottom-dwelling, and decomposer organisms. Plankton: important group of weakly swimming, free-floating biota. Phytoplankton (plant), Zooplankton (animal), Ultraplankton (photosynthetic bacteria) Nekton: fish, turtles, whales. Benthos: bottom dwellers (barnacles, oysters). Decomposers: breakdown organic compounds (mostly bacteria).

Life in Layers Life in most aquatic systems is found in surface, middle, and bottom layers. Temperature, access to sunlight for photosynthesis, dissolved oxygen content, nutrient availability changes with depth.

Life in Layers Surface – Top “Photic Zone” Sunlight penetrates Higher oxygen (O2) concentrations

Life in Layers Middle “Pelagic Zone” “Open Sea”

Life in Layers Bottom “Benthic Zone” Usually dark Low O2 concentrations High decomposition rates

FRESHWATER LIFE ZONES Freshwater life zones include: Standing (lentic) water such as lakes, ponds, and inland wetlands. Flowing (lotic) systems such as streams and rivers. Figure 6-14

Lakes: Water-Filled Depressions Lakes are large natural bodies of standing freshwater formed from precipitation, runoff, and groundwater seepage consisting of four zones.

Lakes: Water-Filled Depressions Four Lake Zones: Littoral zone (near shore, shallow, with rooted plants). Limnetic zone (open, offshore area, sunlit). Profundal zone (deep, open water, too dark for photosynthesis). Benthic zone (bottom of lake, nourished by dead matter).

Lakes: Water-Filled Depressions Figure 6-15

Lakes: Water-Filled Depressions During summer and winter in deep temperate zone lakes they become stratified into temperature layers and will overturn. This equalizes the temperature at all depths. Oxygen is brought from the surface to the lake bottom and nutrients from the bottom are brought to the top. Overturning brings oxygen to lower depths and nutrients from the bottom to the surface.

Effects of Plant Nutrients on Lakes: Too Much of a Good Thing Plant nutrients from a lake’s environment affect the types and numbers of organisms it can support. Figure 6-16

Primary Productivity Gross Primary Productivity (GPP) versus Net Primary Productivity (NPP) Chapter 3 (Figure 3-21)

Lakes are distinguished based on their nutrient content and PP Lakes are distinguished according to their nutrient content and primary productivity Oligotrophic (poorly nourished) lake: Usually newly formed lake with small supply of plant nutrient input (low NPP) Eutrophic (well nourished) lake: Over time, sediment, organic material, and inorganic nutrients wash into lakes causing excessive plant growth and poor visibility (high NPP) Mesotrophic lake: in the middle

Effects of Plant Nutrients on Lakes: Too Much of a Good Thing Cultural eutrophication: Human inputs of nutrients from the atmosphere and urban and agricultural areas can accelerate the eutrophication process.

Freshwater Streams and Rivers: From the Mountains to the Oceans Water flowing from mountains to the sea creates different aquatic conditions and habitats. Figure 6-17

Freshwater Streams and Rivers: From the Mountains to the Oceans SOURCE ZONE Headwaters & upper portion of river Shallow, steep, cold, clear and swift High DO content Animals here, like trout need lots of DO Trout are an indicator species of the water’s health

Freshwater Streams and Rivers: From the Mountains to the Oceans TRANSITION ZONE Wider, deeper, gentler Warmer waters, less DO content Supports species needing less DO like bass

Freshwater Streams and Rivers: From the Mountains to the Oceans FLOODPLAIN ZONE Slow moving, crossing broad, flat valleys More meanders (curves) Warmest temperatures and least DO More algae and cyanobacteria More silt found here, murkier waters

Freshwater Inland Wetlands: Vital Sponges Inland wetlands act like natural sponges that absorb and store excess water from storms and provide a variety of wildlife habitats. Figure 6-18

Freshwater Inland Wetlands Wetlands are covered with water all or part of the time. They are sometimes considered swamps (trees and grasses) or marshes (no trees). They are highly productive ecosystems – very nutrient rich and have high biodiversity

Wetlands are very fragile ecoystems! These wetlands have been ditched and drained for cropland conversion. Figure 6-19

Freshwater Inland Wetlands Filter and degrade pollutants and toxins Reduce flooding and erosion by absorbing slowly releasing overflows. Help replenish stream flows during dry periods. Help recharge ground aquifers. Provide economic resources and recreation.

Saltwater Life Zones TWO MAJOR ZONES

The Coastal Zone warm, nutrient-rich (high NPP), shallow water that extends from the high-tide mark on land to the gently sloping, shallow edge of the continental shelf. The coastal zone makes up less than 10% of the world’s ocean area but contains 90% of all marine species. Provides numerous ecological and economic services. Subject to human disturbance.

Open Ocean Low average NPP, but highest GPP because of size Upwelling – areas where nutrient-rich bottom waters rise to the surface Brings an abundance of plankton > fish

The Coastal Zone Figure 6-5

Estuaries and Coastal Wetlands: Centers of Productivity Estuaries include river mouths, inlets, bays, sounds, salt marshes in temperate zones and mangrove forests in tropical zones. Figure 6-7

Figure 6.6 Natural capital degradation: view of an estuary taken from space. The photo shows the sediment plume at the mouth of Madagascar’s Betsiboka River as it flows through the estuary and into the Mozambique Channel. Because of its topography, heavy rainfall, and the clearing of forests for agriculture, Madagascar is the world’s most eroded country. Fig. 6-6, p. 130

Mangrove Forests Are found along about 70% of gently sloping sandy and silty coastlines in tropical and subtropical regions. Figure 6-8

Barrier Islands Low, narrow, sandy islands that form offshore from a coastline. Primary and secondary dunes on gently sloping sandy barrier beaches protect land from erosion by the sea. Figure 6-10

Estuaries and Coastal Wetlands: Centers of Productivity Estuaries and coastal marshes provide ecological and economic benefits. Filter toxic pollutants, excess plant nutrients, sediments, fertilizer runoff & other pollutants. Reduce erosion and storm damage Stabilize coastlines Provide food, habitats and nursery sites for many aquatic species.

Estuaries and Coastal Wetlands: Centers of Productivity However these ecosystems are rapidly disappearing due to: Industrial development Road surfaces Aquaculture Climate Change It is estimated that 1/3 of the world’s mangroves have already been destroyed!

Coral Reefs Form in clear, warm coastal waters of the tropics and subtropics “Rainforest” of the oceans Figure 6-11

Coral Reefs Very sensitive ecosystems that require clear, warm (64 to 86F) and shallow water with high salinity Home to 25% of all marine species High biodiversity High productivity Figure 6-11

Coral Reefs They have a high commercial value (aquaculture and fishing) Recreation and tourism trades depend on them

Coral Reefs Threatened by: Algae growth from fertilizers Sediments Disease Damage from humans (boating, swimmers, overfishing, overdevelopment) Rising sea levels It is estimated that 20% are so damaged they may not recover

Coral Bleaching Occurs from environmental stress or ocean acidification Algae dies off White or bleached skeleton of calcium carbonate remains

Biological Zones in the Open Sea: Light Rules 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.

Biological Zones in the Open Sea

Effects of Human Activities on Marine Systems: Red Alert Human activities are destroying or degrading many ecological and economic services provided by the world’s coastal areas. Figure 6-13