Where the ocean biome meets land, there is the seashore. Our planet is covered in water, so seashores are abundant around the edges of continents and islands, both large and small, found throughout the world’s oceans. While all seashores are a combination of land and sea, they appear differently depending on their location and even the time of day.
Assorted colors and types of sand, varying sizes and shapes of pebbles and rocks, and the changing tides mean no two seashores look exactly the same. Whether waves pummel rocky ledges or the ocean gently laps a soft, sandy beach, seashores are brimming with life. Plants find a way to grow among the rocks and shifting sands, peppered constantly with salty spray. And hardy creatures tough it out in an ever-changing ecosystem.
As you explore the seashore in this chapter, you will discover the different types of beaches as well as the various parts that make up the beach. You will learn about the relentless waves and the dense salt water that makes them. You’ll study coastal landforms and how they are shaped through weathering and erosion. You will investigate the tides and their impact on wildlife. Your knowledge of sand dunes and seashore plants will grow, as will your understanding of the diverse creatures that make the seashore their home.
THE SEASHORE ECOSYSTEM
Seashores are dynamic ecosystems that border the edges of all continents and islands in between. Seashore ecosystems store and filter water, and trap sediment. Often, rocky and sandy beaches act as buffers when storms roll in, taking the brunt of the wind and punishing waves. The beach face is always changing as the water moves in and out.
The coast supplies ample areas for grasses and other vegetation to help secure sand and create valuable dune areas. And animals like sea turtles, marine mammals, birds, crabs, clams, fish, octopuses, sea stars, and others use shores and the surrounding areas as feeding, nesting, and nursery sites, as well as homes.
Anatomy of a Beach
COASTAL LANDFORMS
Diverse and beautiful landforms develop around the seashore based on geography, weather patterns, and water movement. Because of this, seashores are ever-changing.
FUN FACT
Lagoons may form behind tombolos.
SPITS form through a process called longshore drift when winds blow in at an angle to the coastline, creating a drift of sediment in that direction.
COASTAL LAGOONS are shallow, protected areas of water that are fed by the ocean or rivers.
TOMBOLOS are spits that continue to form until they connect the mainland to an island, like a beach bridge.
HEADLANDS are created when the sea pounds away at the coast, and areas of softer rock are worn away. Bays usually form in the area where the rock was eroded.
BEACHES form when sediment, whether sand, mud, or rock, is carried in from another location.
ARCHES may form if caves in the headlands continue to wear away. Eventually, the arches will widen enough to collapse and form stacks.
The Sand Dune Ecosystem
Sand dunes are flourishing ecosystems! These dry beach areas support plant species like grasses and shrubs. Dunes store sand, and they help protect the coasts further inland from flooding. Burrowing animals can dig through the sand and take shelter in dunes. They feed on the vegetation and other animals there.
THE OCEAN
Covering more than 70 percent of Earth, the world’s salt water is divided into the Pacific, Atlantic, Indian, Arctic, and Southern oceans. They surround the world’s continents, forming smaller bays and inlets, estuaries, and lagoons along the coasts. The area just offshore called the coastal ocean is full of life!
Ocean Zones
The open ocean is divided into five major ZONES.
The EPIPELAGIC zone extends from the surface to about 650 feet (200 m). Sunlight allows for plants to photosynthesize, and most of the animal life scientists know about is found here.
The MESOPELAGIC zone reaches 3,300 feet (1,000 m) below the ocean’s surface. Very little light makes it dark, and the water temperature dips dramatically.
The BATHYPELAGIC zone reaches 2½ miles (4,000 m) deep. Also known as the midnight zone, no sunlight reaches this area. Fish in this zone have unique adaptations like bioluminescence.
The ABYSSOPELAGIC zone makes up approximately 60 percent of Earth’s ocean area. It stretches down 3¾ miles (6,000 m) below the water’s surface and lacks light, heat, and oxygen.
The HADALPELAGIC zone contains trenches carved into the ocean floor— may reach 36,000 feet (11,000 m) deep in some areas.
Water & Waves
An Elemental Look at Water
Ocean water contains many minerals that combine to form salts. These minerals are known as solutes, which are dissolved in ocean water.
WHERE DOES THIS SALT COME FROM?
RUNOFF from rain on land gathers minerals from rocks, drains into rivers, and eventually empties into the ocean.
VENTS in the ocean floor also contribute to Earth’s salty seas through chemical reactions that occur when water is heated by magma beneath the ocean floor.
Vast SALT DEPOSITS underground and under the sea floor also help make the ocean salty.
THE TIDE
If you have ever visited the beach, you probably noticed the water level moving toward or away from you throughout the day. The movement of water inland and then back out is the tide. Twice each day, seashores experience high tides and low tides.
As the Moon revolves around Earth, its gravitational pull moves water toward it. The ocean water bulges toward the Moon on both the side of the Earth closest to the Moon and the opposite side, which causes high tides in those areas.
Tide Pool Habitat
Tide pools form in the intertidal zone and can be found on every type of beach, from smooth sand to jagged rocks. They form as the tide comes in and begins to fill up crevices and depressions in the seashore with water. Animals and plants living in tide pools must be adapted to living without water for some of the day.
Tide pool life is ever-changing, but with the right adaptations, animals can survive. For example, creatures must be able to hold on tightly to avoid being carried away by the ocean waves. Sea stars hang on to rocks with their tube feet, often hiding in crevices to avoid predators and the hot sun. Barnacles create a strong glue to hold on to the rocky tide pool walls, so crashing waves do not dislodge them.
SEASHELLS
Seashells are the exoskeletons of mollusks like clams, oysters, and snails. Shells protect their soft bodies from both predators and harsh conditions in their environment. Mollusks’ shells grow with them. They have an outer layer on their soft bodies called the mantle that makes the three-layered shell and connects the mollusk to it. The layer closest to the mollusk is smooth and shiny. The middle layer gives the shell its strength. And the outermost layer, made mostly of proteins, can be bumpy or ridged.
CONCH
SCALLOP
AUGER
CONE
CLAM
TURRET
COCKLE
ANIMALS
Seashores support living creatures, both large and small. Even tiny or microscopic creatures make their way to the seashore. Seashore animals must deal with the sun, salt, and surf. Waves may bounce them around or carry them out to sea. Life is definitely dynamic in this habitat where only the well-adapted survive.
Seashore Visitors
Female sea turtles visit the seashore to lay their eggs on sandy beaches. Often these turtles will lay more than 100 small, round eggs in the sand before returning to the sea. When the hatchlings emerge in two months’ time, the tiny turtles will crawl through the sand toward their new ocean home.
COASTAL FISH
The diversity of fish in coastal habitats includes both large and small species. Tiny sculpins are adapted to get oxygen from the air when tide pool water levels drop. Leopard sharks adapted to feeding on a variety of fish found in the brackish waters of estuaries, which helps their species’ success. Eels use their long bodies to squeeze into crevices of coral reefs and ambush prey with their sharp teeth.
Despite their adaptations to different ocean habitats, fish actually share many characteristics.
They are vertebrates and have an internal skeleton made of bone (or cartilage in the case of sharks and their relatives).
They usually have gills to take oxygen from the water.
They are often covered in scales.
Most species are cold-blooded, or ectothermic, meaning their surroundings determine their body temperature.
PREDATORY FISH
Microscopic phytoplankton by the billions, along with seagrasses, other plants, and kelp, create the base of the ocean food chain. Creatures like manatees, shrimp, and mollusks feed on these plentiful producers. Smaller meat-eaters, like herring and cod, eat small creatures. Large fish and other sea creatures are on the menu of apex predators like sharks, tuna, and billfish.
Seashore Food Chain
MARINE MAMMALS
Many marine mammals can be observed from shore. This diverse group of creatures includes mammals that live their whole lives in the ocean, such as whales and dolphins. With streamlined bodies, they travel in family groups. They have speed to catch prey and blowholes to breathe air as they surface while swimming. Some marine mammals such as seals and walruses spend time in the sea but come ashore to rest and raise their young.
Dolphin vs. Shark Fin
When viewing from shore, you will notice dolphins’ dorsal fins are shaped like an ocean wave, slightly rounded with a curved rear edge. Sharks’ dorsal fins are more triangular in shape.
Whale Watching
To spot cetaceans (whales and dolphins) from shore, begin by slowly scanning the ocean. Watch for spouts of water going upward. You might get a peek at dorsal fins and flukes emerging from the water. Large splashes in the water may indicate a whale has breached, and smaller splashes could mean a pod of dolphins is offshore.
BIRDS
Birds at the seashore fill different niches to avoid competing with each other for food in their coastal ecosystem. Shorebirds are usually carnivorous species that feed on fish, mollusks, and crustaceans on the beach and in shallow coastal waters. They are social creatures, with different species flocking together at times.
Bird Beaks
PLANTS
Seagrasses and kelp, which are brown algae, grow around the world’s coastal waters, feeding creatures and sheltering animals. Marine plants and kelp have roots to anchor them or structures that wrap around rocks to keep them from floating away. Coastal plants have to deal with salty sea spray, sandy soil, and harsh winds. Many of them are low to the ground and have small leaves to keep them from losing water.
ACTIVITIES
You have walked the world’s seashores and examined this extraordinary ecosystem from the tiniest plankton to the largest coastal predators. In this section, you will find a collection of activities related to your understanding of this part of the ocean biome.
