Essentials of Ecology

CONCEPT 8-2 169

Undisturbed barrier beaches generally have one or
more rows of natural sand dunes in which the sand is

held in place by plant roots (Figure 8-10, p. 170). These
dunes are the first line of defense against the ravages

of the sea. Such real estate is so scarce and valuable

that coastal developers frequently remove the protec-

tive dunes or build behind the first set of dunes and

cover them with buildings and roads. Large storms can

then flood and even sweep away seaside buildings and

severely erode the sandy beaches. Some people incor-

rectly call these human-influenced events “natural

disasters.”

White sand macoma Sand dollar Moon snail

Mole

shrimp

Ghost

shrimp

Tiger

beetle

Beach flea

High tide

Clam

Sandpiper

Dwarf

olive

Peanut worm

Blue crab

Silversides Low tide

Barrier Beach

Nudibranch

Sculpin

Sea urchin Anemone

Low tide

Monterey flatworm

Kelp Sea lettuce

Barnacles

Mussel

Periwinkle

High tide

Rocky Shore Beach Sea star Hermit crab Shore crab

Figure 8-9 Living between the tides. Some organisms with specialized niches found in various zones on rocky shore
beaches (top) and barrier or sandy beaches (bottom). Organisms are not drawn to scale.