Sandy+Beaches+and+Mudflats

=Sandy Beaches and Mud Flats =

Elyse Britton, Justina Buzza, Stephanie Clift, and Ashlee Parsons
=Under Construction=

=Sandy Beaches =

Table of Contents

 * 1) ===Overview of Sandy Beaches===
 * 2) ===Geology of Sandy Beaches===
 * 3) ===Plant Life===
 * 4) === Animal Life===
 * 5) ===Environmental Importance===
 * 6) ===References===

Overview of Sandy Beaches
Continually being reshaped by crashing waves, shifting winds, and fluctuating tide, sandy beaches can be ruthless environments for any inhabitants. However, animals that are native to the sandy beaches have developed several capabilities and adaptations to allow them to live in this harsh habitat. Food in these regions is scarce so many of the animals rely on beach wrack, or detritus, as a major portion of their diet. Due to constant wave action, sand accretion and erosion, and the exposure to salt spray, plant life is very restricted in both diversity and abundance. 3] Most of the vegetation can be found on the cliffs or in the dunes that typically margin the sandy beaches. 2] Depending on the surrounding area species associate themselves correspondingly to that respective domain. Despite our fancy for picturesque, serene sandy beach, in reality this environment is anything but peaceful. (See Figure 1)

Geology of Sandy Beaches
Sandy beaches are commonly found all around the world. Due to the average 8,000 waves that crash on the shores each day, the physical aspects are persistently changing. Although the waves, winds, and tides might not drastically change the beach on a day to day basis, the elements of different seasons have a great impact on the appearance of the shores. Winter storms bring large breakers that etch away at the shoreline. In the winter, the fine sands have been washed or blown away leaving mostly course sand to endure the fierce wave. The summers hold a different appeal. The small gentle waves of summer accumulate the sand, allowing for shallow shores with finer sand. 2] Most of the tides are an affect of the gravitational pull between the earth, sun and moon. Tides are then modified by the sea floor, coastline, and weather. 1]

Sandy beaches can be divided into three main regions. The first is the region beyond the tide, also called the subtidal zone. This zone is always covered by the waves and is not exposed at low tide. Bordering the subtidal zone is the intertidal zone. This region is comprised of the surf and swash zones. 2] The tides rise and fall, concealing and exposing the foreshore immediately in front of the berm crest. The region above the tide or, after the berm crest, contains the backshore. The backshore extends from the highest point of wave action to the nearby bluffs or dunes. 1] Depending on their capabilities and adaptations, animals are allocated among the distinctive regions. 4]

Plant Life
As previously stated, the constant wave action, sand accretion and erosion, and the exposure to salt spray, plant life is very restricted in both diversity and abundance on sandy beaches. 1] Although it is incapable of growing on the sandy beaches, seaweed that has been disconnected and washed ashore is common. These decaying clumps, along with other organisms that have been left on shore by the tides, form what is called beach wrack. While these decomposing heaps of organic material can be seen as undesirable, many sandy beach creatures depend on beach wrack. 2]

Very little food is produced in the sandy beach habitat. What primary productivity occurs in the sand comes from the microscopic algae in the top few centimeters of the sand. 2] Microscopic diatoms are the major producers of this food web, and collectively with fungi and bacteria, that obtain nutrients from the deposited organic matter, they supply food for protozoans such as flagellates and ciliates. 5] Adjacent to the sandy beaches typically exist bluffs or coastal dunes that are inhabited by a diverse variety of flora. Typically plants are equipped to sustain themselves by retaining water. Coastal scrub comprised of drought-deciduous plants such as coyote bush, brochas bush, and succulents are common in these areas. Ice plants, yucca plants, agave, and cacti are some examples of succulents. (See Figure 2).

Animal Life
The animal life on sandy beaches depend on the different zones. Each zone is a home to several species of life. Crabs, fish and birds are the most common of these species and are also the most dominant of them all. These species all depend on each other, as well as the ocean, for survival.

**Crustaceans**
In the high intertidal, there are multiple types of crustaceans that dominate the beaches. The most common species is the Talitrid amphipods, or ‘beach hoppers’. These creatures usually hop or crawl along the sand, using their gills as lungs. They cannot live submerged in water, and just enter the surf to re-wet their gills. These bugs are nocturnal, and leave their homes at night to feed on any plant or animal material left on the shore (they are categorized as ‘non-specific’ scavengers).5]

The sand crab (//Emerita analoga//), also known as the Mole Crab, is the most popular form of life found here. The sand crab inhabits the lower intertidal zone. Unlike most crabs, it can only move backwards, which makes efficient digging more successful. Their legs are used like paddles for advanced swimming capability and strength when the sand is stirred by crashing waves. When burrowing, they dig tail first and leave only their eyes and antennae above the sand to catch phytoplankton when the tides recede. (The Spiny Mole Crab is also found here).5]
 * Crabs:**

**Clams**
The Pismo Clam is found in the Low Intertidal Zone. Mostly scavenging on //Emerita// and any animal matter, these species dominate the Intertidal Zone, leaving few other species with a chance of survival in their zone.6]

**Fish**
Several species of fish live in the sandy beach habitat, just under the oceans surface. Flatfish, Rays and Skates are a few of the various life forms found here. When the tides are in, these fish feed on the crabs, clams and worms of the intertidal zone. Their fins work as ‘wings’ to move sand away to expose their prey. Surfperches and sand eels are also located in this zone, a little farther out from the shore. They hover to retrieve crabs and worms that are unobtainable by the flatfish, rays and skates.6]

**Birds**
Although the sandy beaches contain mostly fish and crabs, there are many species of birds that live there as well. The most common of these are called Sanderlings. These birds are found flying back and forth along the surf, waiting for prey to emerge from the waves before re-burrowing into the sand. The Snowy Plovers are found higher up on the beach in the dry sand, snatching insects and beach hoppers from the surface of the sand, and the Gulls are found feeding on anything that washes up on the beach. These Gulls are the most populated species in this zone.6]

Environmental Importance
Sandy beaches are important to both humans and the animals and plants that live there. These beaches provide homes to hundreds of species of land and water animals. Without the comfort of the sand, many crabs and beach hoppers would become extinct, and the birds and fish that prey on these species would also suffer. This ecosystem harbors abundant and diverse number of species of crustaceans and other marine animals. Without these beaches, scientists would lack the knowledge of marine diets, lifestyles, populations and habits of these animals. Also, we would not be aware of the complexity and importance of marine life, or the tide patterns and their effects on these species. Besides the importance of the life on these beaches, humans would not have the luxury of a nice day at the beach without the beauty and nature of sandy beaches.

Table of Contents

 * 1) ===Overview of Mud Flats ===
 * 2) ===Geology of Mud Flats ===
 * 3) ===Plant and Algae Life  ===
 * 4) === Animal Life ===
 * 5) ===Environmental Importance===
 * 6) ===References ===

Overview of Mud Flats
Mud flats are viewed as layers of rich mud composed of sand, clay, and finer silts. Mud flats can only occur along coastlines with shores that are protected from waves. They are usually exposed during low tide and covered during high tide, and therefore are found in intertidal zones. Mud flats typically support large populations of plants and animals living along the edges of the mud flats, on the surface of the mud, and underneath the surface of the mud. They receive nutrients from tidal flow and the nearby salt marshes.

Geology of Mud Flats
Mud Flats are found along coastlines with shores that are sheltered from waves such as bays and lagoons, and are often known as a form of an estuary. Mud Flats are formed where fresh water such as tides or rivers meet the ocean, and are often formed adjacent to salt marshes. Clay particles are deposited by the gentle water flow of streams and rivers, and sand is deposited by the ocean as it flows into the mouth of the river with high tides and flows out of the mouth of the river with low tides. Finer silts are also deposited by the gentle movement of fresh water and salt water across the sediment. The mixture of clay particles, sand, and finer silts settle out to form layers of mud known as a mud flat. 1]

Scientists have divided many coastal habitats, including mud flats, into four different zones depending on the amount of tidal exposure. Zone 1, also called the uppermost horizon, is the area above the mean of high tides, causing this zone to only be wetted when the tide is much higher than average. Zone 2, also known as the high intertidal zone, is made up of areas reached by the high tide. Zone 3 is also known as the middle intertidal zone, and is found between the mean of the high tide and the mean of the low tide. This zone is usually covered and uncovered one or two times every day. Zone 4, also called the low intertidal zone, is the area with the lowest tide and is typically covered for the majority of the day. These four zones determine the distribution of animals throughout the mud flats. [3 ]

[[image:1SeaLettuce,_1.jpg width="289" height="214" align="right" caption="Figure 3: Sea Lettuce Found in Morro Bay, CA. Image Credit: Elyse Britton" link="Sandy Beaches and Mudflats#animalbeach"]]
There are very few plants that can grow in a mud flat, so the main producers found in this habitat are microscopic algae, macroscopic algae, and sea grasses. Plants have a difficult time flourishing in mud flats due to the composition of the mud flats and the amount of tidal exposure. Numerous plants found in salt marshes also grow along the edges of mud flats, but because they are more productive in salt marshes they will not be discussed here.

**Microscopic Algae**
Benthic microscopic algae are single-celled plants that appear as a golden brown film covering the surface of the mud. They grow in the top three centimeters of mud where oxygen and light allow them to photosynthesize. Benthic microscopic algae are an important source of food for invertebrates living in mud flats. It is estimated that benthic microscopic algae may provide up to 50% of the necessary production of food in some mud flat habitats. [ 2]

**Macroscopic Algae**
A few species of macroscopic algae are found in mud flats, and they are important sources of food for herbivores and crabs. Macroscopic algae often form extensive mats and commonly cover rocks, shells, and debris on the surface of the mud. Macroscopic algae are able to thrive in this habitat because it is protected from waves and strong currents. Sea lettuce and mermaid's hair are the most common macroscopic algae found thriving in mud flats because they can tolerate lots of fresh water and drying out from low tides.4] Sea lettuce (//Ulva expansa//) is bright green sheet-like algae with lobed edges on its leaves and looks like lettuce. (See Figure 3). An important characteristic of sea lettuce is that it is able to continue growing when a piece has been broken and is free-floating in the water, allowing this algae to continue to thrive in its habitat. Mermaid's hair (//Enteromorpha tubulosa//) is yellow-green algae that is made up of long and slender branch-like leaves, resembling the hair of a mermaid. This algae is able to continuously grow to cover large expanses of the surface of mud flats. (See Figure 4). 1]

**Sea Grasses**
Sea grasses are found in the lowest levels, zone 4, in mud flats and often form extensive beds. The most common sea grass is eelgrass (//Zostera marina//), which is able to thrive in mud flats because it is one of very few plants with roots that are able to take hold and grow in the mud, and it is one of few plant that can grow while submerged completely in salt water. Eelgrass has numerous roots and nodes with long blades that can grow up to four feet long. This plant plays an important role in the food web in mud flats because it is consumed by ducks, geese, invertebrates, and fish. 4]

Animal Life
Mudflats have a rich animal life which can be found on the surface of the sediment, and underneath the surface of the mud. There are numerous visible holes burrowed in to the surface of the mud by many animals. (See Figure 5). Just one inch below the surface of the mud you can find several species of clams, worms and crustaceans. Fish and crabs move through with the tides and birds and preditary animals come to feed. Phytoplankton and Zooplankton are abundant and because of this oysters and clams are their to feed on them.Many of the animals in the mudflats have early planktonic stages and therefore at certain times of the year mudflats can be filled with young mollusks, crustaceans and worms. 2]

** WORMS **
Worms are the most diverse group of species in the mudflats and are most commonly found in the middle intertidal zone. The common worms are segmented annelid polychaetes, and slender nermerteans or round worms. The bamboo worm (//Axiothella rubrocincta//) is commonly found intertidally in mud flats. This worms burrows U-shaped tubes that may extend up to 30 centimeters below the surface. The bamboo worm leaves small tubes projecting from the surface of hard packed mud. All of the worms in mud flats are  usually eaten by the many birds that migrate to the area, and by the fish that are found in mudflats during high tide. 3]

**BIRDS**
The most common birds are dowitchers, plovers, sandpipers, herons and gulls. Most of the birds observed in mud flats are migratory birds, and are usually found in this habitat mid to late summer. Birds are commonly found in mudflats looking for food. The bills and long legs of these birds are well adapted for feeding on the organisms that burrow into the mud. It is very common to see bird prints scattered over the surface of the mud.2] (See Figure 6).

**CRABS**
One of the most common crabs found in mud flats is the //Hemigrapsus Oregonesis//. This burrowing crab is found in the uppermost horizon and the high intertidal zones. The //Hemigrapsus oregonensis// is light gray or yellow dorsally, and white ventrally with hair on its walking legs. This crab is known to be very agressive and fights often. The diet of the //Hemigrapsus oregonensis// mainly consists of diatoms and green algae, however they may sometimes scavenge for meat. 3]

**SNAILS**
A typical snail of mud flats is the tall-spired horn snail (//Cerithidea californica//). It is tolerant of extreme conditions of salinity, temperature and exposure. 3] The tall-spired horn snail is one to two inches long and may be found by the hundreds or thousands on the surface of the mud. As a deposit feeder, the tall-spired horn snail ingests the mud and digests the detritus in the mud. 1] (See Figure 7).

Environmental Importance
Mud flats hold different ecological importance to different species. Tidal mud flats are very important for migrating birds. The birds that travel through the mud flats also help control the ecosystems in other places such as the Arctic. The relationship of mud flats to salt marshes can also be important to humans. Mud flats and salt marshes help support natural coastal systems and also support human agricultural systems. Mud flats are also a vital habitat for education of coastal ecosystems 2]