Aquatic Biodiversity Part 1—Introduction & Marine Systems

General Nature of Aquatic Systems

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

Key factors determining biodiversity in aquatic systems are

1. Temperature

2. Dissolved oxygen content

3. Availability of food

4. Availability of light, and nutrients necessary for photosynthesis.

Most of the Earth Is Covered with Water

Aquatic life zonesSaltwater life zones (marine life zones)

Oceans and estuariesCoastlands and shorelinesCoral reefsMangrove forests

Freshwater life zonesLakesRivers and streamsInland wetlands

Fig. 8-2, p. 169

Saltwater: global ocean divided into 4 areas: Atlantic, Pacific, Arctic, Indian.The salty oceans cover 71% of the earth’s surface and contain 97% of the earth’s water. Almost all of the earth’s water is in the interconnected oceans, which cover 90% of the planet’s ocean hemisphere (left) and nearly half of its land-ocean hemisphere (right). Freshwater systems cover less than 2.2% of the earth’s surface (only a fraction of this is drinkable.

The Ocean Planet

Fig. 8-3, p. 170

Aquatic Systems

Where Aquatic Species Live

Key factors in the distribution of organisms areTemperatureDissolved oxygen contentAvailability of foodAvailability of light and nutrients needed for

photosynthesis in the euphotic (photic) zone

Turbidity, degree of cloudiness in water, inhibits photosynthesis

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

Plankton—free floating

1. Phytoplankton—primary producers for most aquatic food webs

2. Ultraplankton—tiny photosynthetic bacteria

3. Zooplankton Primary and secondary consumers Single-celled to large invertebrates like jellyfish

Nekton—strong swimmers: fish, turtles, whales

Benthos—bottom dwellers: oysters, sea stars, clams, lobsters, crabs

Decomposers—mostly bacteria

Why Are Marine Aquatic Systems Important?

Saltwater ecosystems are • Irreplaceable reservoirs of biodiversity

• Provide major ecological and economic services.

Oceans Provide Vital Ecological and Economic Resources

Estimated $12 trillion per year in goods and services, due to

reservoirs of diversity in three major life zones

1. Coastal zone Warm, nutrient rich, shallow Shore to edge of continental shelf Usually high NPP from ample sunlight and nutrients

2. Open sea

3. Ocean bottom

Fig. 8-5, p. 172

Which two ecological services and which two economic services do you think are the most important? Why?

Major Ecological and Economic Services Provided by Marine Systems

Fig. 8-6, p. 173

This diagram illustrates the major life zones and vertical zones.

Available light determines the euphotic, bathyal, and abyssal zones.

Temperature zones also vary with depth, shown here by the red line.

Question: How is an ocean like a rain forest?

Major Life Zones and Vertical Zones in an

Ocean

Estuaries and Coastal Wetlands Are Highly Productive

Estuaries and coastal wetlands—seawater mixes with

freshwater

Very productive ecosystems with high nutrient levels

Include:Mouths of rivers InletsBaysSoundsSalt marshesMangrove forests

Fig. 8-7, p. 173

View of an Estuary from Space

Estuaries and Coastal Wetlands

Seagrass BedsGrow underwater in shallow areasSupport a variety of marine speciesStabilize shorelinesReduce wave impactSince 1980, about 29% of the world’s sea grass

beds have been lost to pollution and other disturbances.

Mangrove forestsAlong tropical and subtropical coastlines69 different tree species that grow in saltwater

This mangrove forest is in Daintree National Park in Queensland, Australia. The tangled roots and dense vegetation in these coastal forests act like shock absorbers to reduce damage from storms and tsunamis. They also provide highly complex habitat for a diversity of invertebrates and fishes.

Estuaries and Coastal Wetlands

Offer important ecological and economic servicesCoastal aquatic systems maintain water quality

by filteringToxic pollutantsExcess plant nutrientsSediments

Absorb other pollutants

Provide food, timber, fuelwood, and habitats

Reduce storm damage and coast erosion

Rocky and Sandy Shores Host Different Types of Organisms

Intertidal zone Rocky shores Sandy shores: barrier beaches

Organism adaptations necessary to deal with daily salinity and moisture changes

Sand dunes are important

Beach flea

Peanut worm Tiger beetle

Barrier Beach Blue crab ClamDwarf olive

High tide

SandpiperGhost shrimpSilversides Low tide Mole

shrimp

White sand macoma

Sand dollar

Moon snail

Rocky Shore BeachSea star Hermit

crab Shore crab

High tide

Periwinkle

Sea urchin AnemoneMussel

Low tideSculpin

Barnacles

KelpSea lettuce

Monterey flatworm

Nudibranch

Stepped Art

Fig. 8-11, p. 176

Living between the tides: Specialized Niches

Coral Reefs

Tiny animals (polyps) and

algae have mutualistic

relationship

Polyps secret calcium carbonate shells, which become coral reefs

Habitats for one-fourth of all marine species

Marine equivalent of tropical rain forests

Important Ecological and Economical Services

1. Moderate atmospheric temperatures2. Act as natural barriers protecting coasts from

erosion3. Provide habitats4. Support fishing and tourism businesses5. Provide jobs and building materials6. Studied and enjoyed

1. Coastal development2. Pollution3. Overfishing4. Increasing ocean acidity

• Warmer ocean temperatures and turbidity leading to coral bleaching• A bleached coral reef has lost most of its algae because of changes in

the environment • With the algae gone, the white limestone of the coral skeleton

becomes visible. • If the environmental stress is not removed and no other algae fill the

abandoned niche, the corals die. • These diverse and productive ecosystems are being damaged and

destroyed at an alarming rate

Degradation and Decline

Fig. 8-12, p. 177

Gray reef sharkGray reef shark

Sea nettleSea nettle

Green sea turtle

Green sea turtle

Blue tangBlue tang

Fairy bassletFairy basslet

Parrot fishParrot fishBrittle starBrittle star

Sergeant majorSergeant majorHard coralsHard corals AlgaeAlgae

Banded coral

shrimp

Banded coral

shrimpPhytoplanktonPhytoplankton

Symbiotic algae

Symbiotic algae

ConeyConey

ZooplanktonZooplankton

Blackcap bassletBlackcap basslet

SpongesSponges

Moray eel

Moray eel

BacteriaBacteria

Producer to primary consumer

Primary to secondary consumer

Secondary to higher-level consumer

All producers and consumers to decomposers

Natural Capital: Some Components and Interactions in a Coral Reef Ecosystem

Three Vertical Zones of the Open Sea

1. Euphotic zone—upwelling brings nutrients to euphotic zone Nutrient levels low Dissolved oxygen levels high Phytoplankton

2. Bathyal zone Dimly lit Zooplankton and smaller fishes

3. Abyssal zone Dark and cold High levels of nutrients Little dissolved oxygen Deposit feeders Filter feeders

Human Activities Are Disrupting and Degrading Marine Systems

Coastal developmentOverfishingUse of fishing trawlers Runoff of nonpoint source pollutionPoint source pollutionHabitat destruction Introduction of invasive speciesClimate change from human activitiesPollution of coastal wetlands and estuaries

Fig. 8-13, p. 179

Natural Capital DegradationMajor Human Impacts on Marine

Ecosystems and Coral Reefs

Marine Ecosystems

Coral Reefs

Half of coastal wetlands lost to agriculture and urban development

Ocean warming

Over one-fifth of mangrove forests lost to agriculture, development, and shrimp farms since 1980

Soil erosion

Rising ocean acidity

Beaches eroding because of coastal development and rising sea levels

Bleaching

Algae growth from fertilizer runoff

Ocean bottom habitats degraded by dredging and trawler fishing

Increased UV exposure

Rising sea levels

At least 20% of coral reefs severely damaged and 25–33% more threatened

Damage from anchors

Damage from fishing and diving

Fig. 8-14, p. 180

Chesapeake BayThe Chesapeake Bay is the largest estuary in the United States. However, the bay is severely degraded as a result of water pollution from point and nonpoint sources in six states and the District of Columbia, and from the atmospheric deposition of air pollutants.

The Chesapeake Bay—an Estuary in Trouble

Human population increased

Point and nonpoint sources raised pollution

Phosphate and nitrate levels too high

Excess sediments from runoff and decreased vegetation

Oysters, a keystone species, greatly reduced

1983: Chesapeake Bay Program Integrated coastal management with local, state, federal

governments and citizens’ group

2008 update: 25 years and $6 billion Program met only 21% of goals Water quality “very poor”