Aquatic Biodiversity

APES CHAPTER 8

CORE CASE STUDY –CORAL REEFS

What coral reefs require? Dissolved oxygen, light &

nutrients What threatens coral

reefs? (3) Chemical pollution, global

warming, extra UV ozone hole, excess sediment from rivers (soil erosion), human contact

Coral Reefs

What percent of reefs is estimated to be destroyed by human intervention?

10 percent

What about estuaries and wetlands? About 50%(US) through filling, sewage, runoff

pollution, and diversion

8-1 What Is the General Nature of Aquatic Systems?

Concept 8-1A Saltwater and freshwater aquatic life zones cover almost three-fourths of the earth’s surface with oceans dominating the planet.

Concept 8-1B The key factors determining biodiversity in aquatic systems are temperature, dissolved oxygen content, availability of food and availability of light and nutrients necessary for photosynthesis.

Aquatic life zones cover almost three-fourths of the earth’s surface

• Saltwater: marine • Estuaries• Coastal wetlands• Coral reefs• Mangrove forests• Open Ocean

8-1 What Is the General Nature of Aquatic Systems?

• Freshwater• Lakes• Rivers and streams• Inland wetlands

Most Aquatic Species Live in Top, Middle, or Bottom Layers of Water

Aquatic systems contain floating, drifting, swimming, bottom-dwelling, and decomposer organisms.

• Plankton: important group of weakly swimming, free-floating organisms• Phytoplankton (plant), Zooplankton (animal),

Ultraplankton (photosynthetic bacteria)

• Necton: fish, turtles, whales

• Benthos: bottom dwellers (barnacles, oysters)

• Decomposers: breakdown organic compounds (mostly bacteria)

Types and numbers of organism found depend on:• Temperature• Access to sunlight for photosynthesis• Dissolved oxygen content• Nutrient availability

These characteristics vary with depth.

Most Aquatic Species Live in Top, Middle, or Bottom Layers of Water

Euphotic zone (“well lit” in Greek)• The upper layer through which

sunlight can penetrate.

8-2 Why Are Marine Aquatic Systems Important?

Concept 8-2 Saltwater ecosystems are irreplaceable reservoirs of biodiversity and provide major ecological and economic services.

8-2 Why Are Marine Aquatic Systems Important?

The oceans that occupy most of Earth’s surface provide many ecological & economic services.

Scientists estimate marine systems provide $12 trillion in goods/services/ year – 70% more than terrestrial ecosystems.

Estuaries and Coastal Wetlands Are Highly Productive

The coastal zone: the warm, nutrient-rich, shallow water that extends from the shoreline to the 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.• Subject to human disturbance because of high

populations along ocean coastlines.

Estuaries are where fresh water rivers empty into the salt water oceans.• The fresh water is less

dense so it floats on top of the more dense salt water.

Estuaries include river mouths, bays, salt marshes, and mangrove forests.

Estuaries and Coastal Wetlands Are Highly Productive

Fig. 7.7, p. 157

Estuary – Madagascar’s Betsiboka River

Madagascar Satellite pix Sediment

plume(turbidity by runoff) forms @ mouth as flow thru estuary into Mozambique Channel.

Topography, heavy rains, deforestation, Madagascar is world’s most eroded country.

Estuaries and coastal marshes provide ecological and economic services.• Filter toxic pollutants, excess plant nutrients, sediments,

and other pollutants.• Reduce storm damage by absorbing waves and storing

excess water produced by storms and tsunamis.• Provide food and habitats for many aquatic species.

Estuaries and Coastal Wetlands Are Highly Productive

Rocky and Sandy Shores Host Different Types of Organisms

Intertidal Zone: the area of a shoreline between low and high tides.

Organisms living in the intertidal zone have evolved a number of ways to survive under harsh and changing conditions. They must deal with daily changes in temperature, salinity, wave action, and being left “high and dry”.

Coral reefs form in clear, warm coastal waters of the tropics and subtropics.• Very important that they have

consistently warm water

They are home to a huge amount of biodiversity• 25% of all marine species• “Rain Forest of the Ocean”

Coral Reefs Are Amazing Centers of Biodiversity

Core Case Study: Why Should We Care about Coral Reefs?

Biodiversity

Important ecological and economic services:• Moderate atmospheric temperatures• Act as natural barriers protecting coasts from

erosion• Provide habitats• Support fishing and tourism businesses• Provide jobs and building materials• Studied and enjoyed

Degradation and decline:• Pollution• Overfishing• Warmer ocean temperatures • Causing coral bleaching

• Increasing ocean acidity• Dissolving coral (calcium carbonate)

Core Case Study: Why Should We Care about Coral Reefs?

The Open Sea and Ocean Floor Host a Variety of Species

Euphotic zone: brightly lit surface layer• Nutrient levels low, dissolved O2 high, plenty of

photosynthetic activity.

Bathyal zone: dimly lit middle layer• No photosynthetic activity, zooplankton and fish live

there and migrate to euphotic zone to feed.

Abyssal zone: dark bottom layer• Very cold, little dissolved O2.

• High nutrient levels – filter down from the layers above• Upwelling – nutrients are brought to the surface by currents

Major Life Zones and Vertical Zones in an Ocean

8-3 How Have Human Activities Affected Marine Ecosystems?

Concept 8-3 Human activities threaten aquatic biodiversity and disrupt ecological and economic services provided by saltwater systems.

Major threats to marine systems:• Coastal development• Overfishing• Runoff of nonpoint source

pollution• Point source pollution• Habitat destruction• Introduction of invasive species• Climate change from human

activities• Pollution of coastal wetlands and

estuaries

8-3 How Have Human Activities Affected Marine Ecosystems?

8-4 Why Are Freshwater Ecosystems Important?

Concept 8-4 Freshwater ecosystems provide major ecological and economic services and are irreplaceable reservoirs of biodiversity.

Freshwater life zones include:

• Standing (lentic) water• lakes, ponds, and inland

wetlands

• Flowing (lotic) systems• streams and rivers

8-4 Why Are Freshwater Ecosystems Important?

Lakes are large natural bodies of standing freshwater formed from precipitation, runoff, and groundwater seepage consisting of:

• Littoral zone (near shore, shallow, with rooted plants)

• Limnetic zone (open, offshore area, sun-lit)

• Profundal zone (deep, open water, too dark for photosynthesis)

• Benthic zone (bottom of lake, nourished by dead matter)

Water Stands in Some Freshwater Systems and Flows in Others

Distinct Zones of Life in a Fairly Deep Temperate Zone Lake

During the summer and winter, lakes become stratified into temperature layers.

In the spring and fall, the temperature equalizes and the lakes “overturn”.• Oxygen is brought from the surface to the lake bottom and

nutrients from the bottom are brought to the top.

Turnover in a Lake

Some Lakes Have More Nutrients Than Others

Plant nutrients from a lake’s environment affect the types and numbers of organisms it can support.

• Oligotrophic (poorly nourished) lake: Usually newly formed lake with small supply of plant nutrient input.

• Mesotrophic (medium nourished) lake: most lakes are in between

• Eutrophic (well nourished) lake: Over time, sediment, organic material, and inorganic nutrients wash into lakes causing excessive plant growth.

Cultural eutrophication:• Human inputs of nutrients from the atmosphere and

urban and agricultural areas can accelerate the eutrophication process.

Some Lakes Have More Nutrients Than Others

Water flowing from mountains to the sea creates different aquatic conditions and habitats.

Freshwater Streams and Rivers Carry Water from the Mountains to the Oceans

Watershed or drainage basin• the land area that delivers

runoff, sediment, and dissolved substance to a stream or river.

The larger the watershed, the larger the river it feeds into.

Freshwater Streams and Rivers Carry Water from the Mountains to the Oceans

Inland wetlands act like natural sponges that absorb and store excess water from storms and provide a variety of wildlife habitats.

Freshwater Inland Wetlands Are Vital Sponges

Filter and degrade pollutants. 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.

Freshwater Inland Wetlands Are Vital Sponges

8-5 How Have Human Activities Affected Freshwater Ecosystems?

Concept 8-5 Human activities threaten biodiversity and disrupt ecological and economic services provided by freshwater lakes, rivers, and wetlands.

Human activities are disrupting the freshwater ecosystems in many ways:

• Construction of dams and canals on rivers

• Flood control levees and dikes alter and destroy aquatic habitats.

• Cities and farmlands add pollutants and excess plant nutrients to streams and rivers.

• Many inland wetlands have been drained or filled for agriculture or (sub)urban development.

8-5 How Have Human Activities Affected Freshwater Ecosystems?