Alluvial soils are 38% clay, thus they have a greater surface area since they consist of finer particles. Hence, they hold more chemical compounds, especially heavy metals.

Nutrients are used so quickly after being released by decomposition that there is very little build up of detritus on the SF floor. Significant accumulation of nutrients normally occurs only after there is a disturbance. As an example, it was found that in a drained SF in Florida, there was a resultant canopy thinning that allowed greater light penetration to the ground. The result was a drier understory that inhibited decay and litter accumulation accelerated. Net primary productivity dropped 40%.

Primary production
Types of plants in the SF include trees, vines, herbs, and epiphytes.

Trees dominate total biomass which, here, is estimated at 3.5 lb/sq ft. Only 5% of the sunlight hitting the canopy reaches the ground.

Bottomland hardwood plants include:

Other species for bottomland hardwood include honey locust, cottonwood, and wateroak. As mentioned before, natural levees allow intrusion of live oak, green ash, and hackberry.

The most common forms of non-woody plants are vines such as poison ivy, greenbriar (smilax), trumpet creeper, ratan, muscadine grape, and peppervine.

The most common epiphyte, in both bottomland hardwood and swamp, is Spanish moss. Herbs are not very abundant because of the frequent inundations, but any high ground will be covered.

Swamp plants include:

Primary consumers
These are virtually the same as in hardwood forests, but some terrestrial forms (such as rabbits) may only have access during periods of low water.

Primary consumers are represented by the following: insects, nutria, woodducks, some turtles, etc.

Good example of movement of photosynthesis products:
Tent caterpillars can defoliate tupelo stands. There is some evidence to indicate that this defoliation may stimulate tree growth by moving organic substances from the canopy to the forest floor (via feces) during spring when little leaf fall is occurring.

Detritivores
Detritivores are very important in that swamps are detritivore-based with two-thirds of the energy entering the food web coming from this source. Detritivores in this habitat include insects, crustaceans, fungi, and microbes. Crawfish are among the most important detritivores in this habitat due to their habit of constantly shredding leaves, thus enhancing microbial activity by reducing the large leaves to smaller pieces (i.e., creating greater surface area). Microbes attack these bits and break them further while incorporating elements of the organic material into "microbial protein" (i.e., protein made during the life processes of the microbes). This microbial protein works its way up the ladder when larger detritivores ingest detritus which microbes are on and assimilate microbial protein in their tissue. Bigger things ingest them, bigger things ingest them, . . .

Secondary consumers
cottonmouths, largemouth bass, raccoons, bats, lizards, frogs, shrews, turtles, spiders, etc.

Tertiary consumers
Include large alligators, bald eagles and other raptors, bobcats, and humans.

Water bodies of the SF - bayous and lakes.
These don't function much in primary production, but more as conduits for moving excess nutrients and detritus from the SF.

Because of this, waterbodies of the SF tend to be heterotrophic (total consumption exceeds production). This is true more of bayous than lakes. Higher trophic levels are supported by runoff from the SF (estimated at 0.04 lb/sq ft/yr - an acre is 43,560 sq ft, so we are talking about 1,700 lb/ac/yr).

A 1976 study estimated that a des Allemands swamp yielded annually: 9900 tons organic matter, 940 tons nitrogen, and 140 tons phosphorus. All of this went to adjoining marshes to increase further productivity.

Primary production in SF water is from:

1. submergent vegetation (coontail, fanwort)
2. floating vegetation (duckweed, hyacinth, water lettuce)
3. emergent vegetation (alligator weed, smartweed)
4. phytoplankton - not too active because:
   • shading from trees and floating plants
   • turbidity of water

Primary consumers include some fish, red-eared turtles, insects, nutria, muskrats, etc. Secondary consumers (=predators, but not in the Schwarzenegger mode) include bass, crappie, snakes, lizards, snapping turtles, mink, otters, small alligators, etc. Tertiary consumers include large alligators, bald eagles and other raptors, cottonmouths, Cajuns, etc.

VALUES OF LOGS AND BRANCHES IN WATER ( taken verbatim from a brochure advertising a new book about the values of wood in water, such as logs in rivers, on beaches, in ponds, etc.). This applies to fresh and salt water.

1. Wood in streams and rivers is a source of food energy for invertebrate organisms; habitat for vertebrate organisms, such as fish; and a structural component that shapes, diversifies, and stabilizes channels while helping to dissipate the water's energy before it can scour channels.
2. Wood in estuaries is a major source of food and habitat for obligatory, wood-boring, marine invertebrates which in their feeding break it down and pass usable carbon into the water's current, where it enters the detrital-based marine food web.
3. Wood along the coastline stabilizes sand spits, beaches, and dune complexes, as well as battering rocky shores, where it creates new habitats for intertidal organisms and provides small splinters of wood to the coastal food chain.
4. Driftwood floating in the open ocean attracts a variety of marine invertebrates and fishes, forming a floating surface community that help organisms colonize new areas. Large fishes, such as tuna, not only feed on smaller fishes attracted to the wood but also drift with it because its movement is controlled by wind and current; thus tuna find the bet feeding areas -- current interfaces rich in food species.
5. The loss of wood to aquatic ecosystems means destabilization of streams, estuaries, dunes and beaches as well as food chains in the oceans of the world. Sooner or later it may mean the loss of jobs and unique cultural ways of life, such as the commercial fishing of certain species.

Habitat Table of Contents

III. FRESHWATER MARSH
- 19% of the Barataria Basin in 1976.

In freshwater marsh, water flow is unidirectional, from inland to the Gulf. Freshwater marshes can rebuild themselves through copious amounts of vegetation growth. Brackish and saltwater marshes cannot, so the only way they can be saved is to reintroduce sediments into them.

Louisiana has a wide variety of marshes. If one spends much time walking the wetlands, one will have experiences ranging from dry feet to sinking to one’s waist in smelly muck. Most marshes are growing in soil, so the more consolidated it is, the easier it is to walk.

Louisiana has a special form of marsh that can be found in either freshwater or intermediate marsh. It is called flotant (flow tawnt’) by the locals (and often referred to as la prairie tremblante, or, trembling prairie), because it is a floating marsh that is not anchored to the ground beneath. It consists of tightly entangled plants and their roots, mixed with peat; typically there is water flowing below it, then some oozing soil, then clay. Patches of it may occur within normal marsh, and from the surface, it looks like any other marsh. It may be rather thin and not able to support a person, or it may be very thickly vegetated and solid enough for a human to actually walk about on it. If one steps on flotant marsh, one will feel like he/she is standing on a water bed. As one steps around, waves of grass spread outward from each step. It is tempting to jump up and down, but the flotant is rarely thick enough and one usually ends up falling through.

Though the types of marshes may look the same, the overall ecology of flotant is very different from that of freshwater and intermediate marsh. By definition, flotant is floating, so it is never inundated with water and covered with sediments as the others are on occasion. However, some floating marshes don’t float all the time, lying on the bottom for part of the year - and maybe even being covered sometime by water.

When the water level drops and the floating marsh touches the bottom, there is danger that the roots will grow into the soil and, when the water rises again, the “floating marsh” stays attached and is drowned and may die.

Over time, as the floating marsh thickens, new and larger plants are able to grow on the mat. In some places, there comes a time when woody plants, especially Wax Myrtle (Myrica cerifera), can grow and be supported by the floating marsh. Even small cypress trees and the like can grow under some conditions. When this happens, the floating marsh is changing and will someday become swamp forest as the cypress and tupelo take over. Remember, this is a remarkable change since the area goes from being open marsh (water with no woody plants) to swamp (water with woody plants).

When Hurricane Andrew blew through south Louisiana, it passed over some of the best flotant marsh zones in the state. In some areas, terrible damage occurred. The flotant was ripped from the shore and the storm winds pushed it across the water where it bunched up in folds on the other shore. It looked like a bed spread does when one kicks one’s covers off during the night and they bunch up at the foot of the bed. We thought that this would be devastating, but over the next couple of years the flotant spread back out and reunited with the other shore. Most of these marshes look today like they did before the hurricane.

However, there is danger when flood waters from rivers enter floating marshes. They may lift the marsh, tear it into smaller pieces, and float it away until it enters estuaries and the Gulf. These conditions result is open expanses of water that may never, or will take decades to, become flotant again.

Floatant is deteriorating where no freshwater is entering the area it inhabits. In order to have a truly balanced ecosystem in our coastal wetlands, we need to protect all its components - and flotant is a very important segment.

Soil: 33% clay
65% organic - buildup of peat in many areas due to underdecomposed detritus.
Sulfides are high as are heavy metals.

Primary Production

Principal type of plants:

1. Standing vegetation (maidencane, bulltongue, spike rush, pickeral weed, bull whip, etc, etc)
2. epiphytes (algae on standing vegetation - may occasionally out-produce the host plants)
3. benthic algae - important during winter when the standing vegetation dies back and light penetration is better.

Primary consumers

Detritivores: crustaceans, microbes

Secondary consumers: insects, spiders, herps, birds, mink, raccoons, otters, etc.

Tertiary consumers: same as for swamp forest open water.

Habitat Table of Contents

IV. INTERMEDIATE MARSH. This was not broken out in the Bahr and Hebrard publication, so the following facts will identify this type of marsh.

Intermediate marsh is where most marsh deterioration has occurred in recent times. This is the interface between riverine and marine systems.

Ecologists who work the Louisiana marshes are the only ones who recognize this category of marsh. The reason that it is found in Louisiana is that our marshes are so extensive that, over time, this new assemblage of plants and associated animals has "evolved." These marshes are extensive and are always found between freshwater and brackish marshes. They are extemely productive. As an example, this is where peak alligator productivity occurs.

They are easily recognized in that they have nice stands of Spartina patens intermixed with many freshwater species.

Trophic structure is very much like freshwater marsh (with the introduction of S. patens and slightly decreased biodiversity).

Habitat Table of Contents

V. BRACKISH MARSH
- 20% of the Barataria Basin in 1976.

There is much more open water surface in brackish marsh than in freshwater marsh. There is bidirectional flow of water, so it is much more affected by saltwater movement. Tides and storm surge are important elements in their ecology.

Soils. Clays are 16-30%. Of the coastal habitats, brackish areas are highest in carbon (27.7%), nitrogen (1.6%), and sulfides. Heavy metals are about the same as the other habitats.

Primary production
Net primary production is the same as freshwater: 0.22 lb/sq ft annually.

Due to the harsher, less stable environment created by the presence of salt, species diversity in plants is lower, with two species (Spartina patens and Distichlis spicata) making up 68.5% of the flora.

Primary consumers:

Eat out - areas where there is an overpopulation of muskrats and they have eaten all the vegetation, often down to and through the roots. Since they often feed on the roots, their feeding inhibits regrowth of plants.

Secondary and tertiary consumers are as those listed below.

Brackish water bodies -
Plants:

There is much phytoplankton activity here.

Detritivores
We see the introduction of polychaete (many bristles) worms. Also, nematodes, microbes, and crustaceans are still important.

Primary consumers - Insects, mullet (phytoplankton feeders), etc.

Secondary consumers
- Egrets reverse the nutrient flow by pooping nutrients from brackish marsh back into the freshwater marsh. Crabs, croaker, speckled trout, redfish, flounder.

Tertiary consumers - Osprey, sharks, humans, etc.

Habitat Table of Contents

VI. SALTMARSH
Soils are 10% clay and 90% organic matter. There is no organic litter around the plants due to daily flushing from the tides. Fine debris builds and creates an anaerobic environment. Microbes produce methane, hydrogen sulfide, and ferrous compounds that stink to pooyi when you walk through the salt marsh.

Most elements are about the same as the other habitats; heavy metals are lower due to the decreased clay content.

Primary production
- 0.2 lb/sq ft (as high as 0.6)

This is the least diverse of the habitats, primarily due to the twice daily flushing that creates the extremes of dry and salty. 63% of the vegetation is one species, oyster grass (Spartina alterniflora). This species is well adapted for the salt environment due to the following characteristics:

1. It has the ability to concentrate salt in cells at higher concentrations than sea water, so it maintains a balanced osmoregularity.
2. It can excrete excess salt.
3. It has air tubes that take oxygen from the leaves to the roots.

Oyster grass can tolerate low salinity, but it has less competition in salt water. There are four very important positive values to oyster grass:

1. It has dense roots that inhibit erosion. In fact, it produces more biomass below the surface than above.
2. It acts as a nutrient pump. Its roots pull phosphorus out of the anaerobic mud to the surface.
3. Through death, it supplies the estuaries and the Gulf of Mexico with nutrients.
4. It provides important habitat for many critters.

Oyster grass is replaced at 5 cm above mean high tide by S. patens and D. spicata.

There are epiphytes and benthic algae (mostly diatoms) present.

Detritivores - same as for brackish.

Primary consumers

The edge effect (increased diversity found at the interface of two habitats) was studied in this habitat. It was found that, at the edge of the estuary, biomass of the primary consumers was 0.003 lb/sq ft. At 10 ft from the edge in the grass, it was 0.008 lb/sq ft. It gradually declined away from the water's edge to about 0.001 lb/sq ft.

Note: A place where two habitats overlap is called an ecotone. In an ecotone, the edge effect takes place.

Most primary consumers are found in the edge; only the periwinkle is somewhat evenly distributed.

Secondary consumers
Same as in brackish, but the number of species may thin out. It is dominated by wading birds. Some (e.g., ibises) may fly 50 miles to feed here.

Tertiary consumers: Same as brackish.

Habitat Table of Contents

VII. ESTUARIES.
Definition: An estuary is a semi-enclosed coastal body of water that has a free connection with the open sea and within which sea water is measurably diluted with freshwater derived from land drainage.

Estuaries may be very unstable in salinity depending on riverine input. There are 900 individual estuaries along the U.S. coast, making up 68,000 sq km.

Types of estuaries:

• Fjord - rocky coasts; created by glaciation. Norway, Alaska, northwest Canada.
• Fault block estuary - created by geologic changes where there is tectonic activity. San Francisco Bay.
• Coastal plain estuary - flooding of a river valley. Chesapeake Bay via sea level rise of the Holocene.
• Coastal lagoon - behind barrier islands. Gulf coast.
• River delta estuary - at the mouth of a river. Mississippi River estuaries (Pontchartrain, Barataria).

Salinity is primarily caused by the presence of sodium and chlorine (86% of sea water). If you add sulfur, magnesium, potassium, and calcium, it adds up to 99%.

	% salt content	parts per thousand (ppt)
Cl	55.0	19.6
SO4	7.6	2.7
HCO3	0.3	0.1
Na	30.6	10.8
Mg	3.7	1.3
Ca	1.2	0.4
K	1.1	0.4
TOTAL	99.5%	35.3 ppt

Because sea water is usually well mixed, relative proportions of major elements change little. Thus, determination of the most abundant element is a good index of the amount of salt present in a given volume of sea water.

Dissolved salt is usually expressed as chlorinity or salinity. As noted above, it is normally expressed in terms of parts per thousand (ppt, or ‰).

Chlorinity = amount of chlorine (in grams) in a kilogram of sea water.

Salinity = chlorinity X 1.80655. In normal sea water (35 ppt salinity), total salt content = 1.80655 the chlorine content.

Salinities for the four types of marsh are as follows:

Salinity in estuaries is extremely variable due to:

Vertical salinity:

Horizontal salinity:

The amount of freshwater inflow is very important. Mesquite Bay is located on the central Texas Gulf coast. During the 1950s, there was a lengthy drought and salinities ran 35-50 ppt. In early 1957, heavy rains caused salinities to drop to about 2.5 ppt in just two months.

Hypersaline estuaries may result when

1. the inflow of freshwater is low
2. tidal amplitude is low
3. evaporation is high.

Laguna Madre in coastal Texas gets as high as 60 ppt. By comparison, Great Salt Lake ranges 140-280 ppt.

PRODUCTIVITY
Primary producers - primarily phytoplankton, but there is widgeon grass, turtle grass, and relatives.

Primary consumers - shrimp, mullet, menhaden

Secondary consumers - wading birds, fishing birds (skimmers, terns, gulls, pelicans), diving ducks (scaup, merganzers), loons

Tertiary consumers - Northern Harriers, Osprey, Eagles, Peregrin Falcons, some alligators (crocodiles in extreme southern Florida), sharks

Productivity is very high in estuaries due to the following:

1. Estuaries are nutrient traps.
   • Benthic critters are rapidly recycling nutrients.
   • High formation of detritus and organic materials.
   • Recovery of deep sediment nutrients by microbial activity and penetrating roots.
2. Diversity of producers. All are present: macrophytes, benthic microphytes, and phytoplankton.
3. Water circulation. The constant movement of estuary water, back and forth, provides work to carry waste away and to move food about. This saves metabolic expenditure of the fauna and allows for the increase in number of sessile critters (those that sit in one place, like oysters, clams, sponges, etc.). The water movement also circulates nutrients and organic matter. Salt water wedges moving under freshwater do so, as well.

Habitat Table of Contents

VIII. BARRIER ISLANDS.
These are long, sand (often in dunes) covered islands that are roughly parallel to the coast and separated from the mainland by a lagoon or salt marsh.

How are they formed? There are three theories (see adjacent figures)

1. deBeaumont, 1845. This theory involves the emergence of submarine bars. Waves move sand to the bar until it emerges. Doug Johnson in 1919 showed that this happens when he demonstrated that the slope on the seaward side of the barrier island was scooped out, i.e. it was not on the same plane as the landward bottom.
   deBeaumont Model
   
2. Karl Gilbert, 1885. Spit growth occurs as sand moves along the coast. The water breaks through the spit and forms islands. John Fisher (1968) agreed, because if the submerged coast concept (see below) was true, scientists would find the remains of forests, etc., under lagoons (the reason one doesn't find the remains of swamps is that there were most often marshes in these areas).
   Gilbert-Fischer Model
   
3. W. D. McGee, 1890. This theory, called the "cyclic model of deltaic change" (we will call it the "Penland Model" [see below]), expressed the belief that barrier islands were left after the land behind them sank under water due to sea level rise. Hoyt (1967) reasoned that this was true because no marine organisms or their remains are found on the mainland side of the lagoon, so there must have been broad expanses of beach that were covered.

Our own Dr. Shea Penland, University of New Orleans, believes that this is how Louisiana's barrier islands formed. They were once sandy beaches along the leading edge of extensive subdeltas of the Mississippi River. As the river changed course and the subdeltas lost their source of nourishment, the marshes began to subside and left the barrier beaches standing in the open sea as barrier islands.
Penland Model
Lateral View

Aerial View

What causes the migration of barrier islands?

1. Waves remove sand from beaches during storms.
2. Longshore currents move sand along the beach.
3. Storms and bad tides flow over the island and:
   • push sand from the beach front to the rear of the island or, worse, into the lagoon. This is termed an overwash and is clearly visible from the air.
   • cut the island in two by forming a channel.
4. Where inlets occur, sand arriving with longshore currents enters the lagoon. These usually form ebb and flood tidal deltas.

How do people try to control barrier islands? (see figures)

1. Groins - This, and the next two, are referred to as hard engineering since they entail construction of structures. As previously defined, these are structures perpendicular to the beach that extend into the sea. Their function is to build beach at one point. They catch sand that is moving in longshore currents, but deprive beaches downshore of their normal diet of sand.

   Louisiana’s most famous (or infamous) groins (though they were widely and incorrectly called jetties) were those implemented in Grand Isle by the late Mayor Andy Valence. They were constructed of huge boulders (four feet in diameter) in the Gulf adjacent to the Edgewater Hotel. After thoughtful consideration, Mayor Valence developed a unique design (see adjacent figure “Grand Isle “Jetties”) that was intended to build land, with plans for adding new groins seaward until about a mile of new land developed. The concept was that onshore waves carrying sediment would enter the rectangular area bound by two T-shaped groins, four breakwaters, and the retainer wall. In theory, water entering this area would lose energy and sediment would settle out and fill the space. Also, the rocks in the groins were spaced so that 15% of the longshore current would pass through them and deposit sediment on the lee side. Then a new groin system would be build seaward. In fact, theory was not borne out. But, as expected, sand built up on the up-current (west) side of the groins and the beach declined on the down-current (east) side - as expected. The only solution for protecting Grand Isle is the U.S. Army Corps of Engineers pumping offshore sands to create new beach.

2. Jetties - Function as above, but are always located at the mouth of navigable channels. Their function is to keep the channel navigable!
3. Sea walls, bulkheads, revetments, and breakwaters - Sea walls are simply concrete walls built at the margin of the shore and the sea. Bulkheads are similar, but when this term is used, it usually means that construction if of wood and it is often along a channel. Revetments are places where objects are piled on a bank. Breakwaters are walls built in areas where waves normally rush to shore.

   Once any of these structures are established, the sand is washed away and the beach disappears. Eventually, a storm will undermine the structure.

4. Beach nourishment (called soft engineering) - This is where sand is pumped onto the beach area, either from existing offshore sand deposits or after being barged in. This is very expensive. After Hurricane Juan, the Corps of Engineers spent $6 million nourishing Grand Isle's beach (again!).

   There is now a proposal to mine sand from offshore deposits to be used to renourish beaches. This should be plenty controversial, but has potential.

5. Planting and dune fencing - This practice involves putting out new plantings or items (Christmas trees, bales of hay, fencing) to catch and hold the wind driven sand.
6. Construction or reconstruction - In Terrebone Parish, there are two excellent, successful examples of how barrier islands can be reconstructed or can be stabilized (for a period of time!) via leveeing techniques. Wine Island (formerly called Vine Island) was located near the mouth of the Houma Navigation Canal. The Parish implemented a plan whereby a ring of stones were placed where Wine Island used to be and dredge material was placed inside. Now there is an island again. On East Island (the eastern-most piece of the former Isle Dernier), a huge levee was built and filled in to a height of some six feet above sea level. It was then planted with many species of naturally occurring plants. This project has stabilized East Island for the next 10 years or so. A similar project was established on Fouchon Beach in 1994.

Rule of thumb: Barrier islands are and will always be dynamic, moving elements of our coast. This gradual movement is part of the natural order of geologic processes and cannot be controlled.

Dilemma: Barrier islands are very important as boundaries of lagoons and estuaries, yet people's use for houses, roads, etc., on these dynamic structures is hastening their loss. Anyone who builds a structure on any piece of land surely doesn't want to see the land move away and leave the structure in the water!

Future: The eustatic rise in sea level will eventually submerge the barrier islands. This is geologically cyclic. Our barrier islands are only several thousands of years old now (some are only 300 years old) and have come and gone in the past.

Habitat Table of Contents

IX. BEACHES AND THE WAVE CLIMATE NEAR THEM.
Definition: A broad ribbon of sand lying on the land at the edge of the sea.

Beaches actually belong to the sea since sand is constantly shifted by waves and longshore currents. They are a river of sand. They are extremely important since they protect marshes from constant wave energy and storm surges.

There is not much available sand near shore in western Louisiana, so most of our beaches are receding.

Primary producers.
Mostly evergreen perennials, so there is very little seasonal change. Most of them are xerophytes (plants that tolerate lack of available water) and they typically are very tolerant of disturbance. On the beach proper, characteristic plants include beach morning glory (Ipomea pes-carpe), railroad vine (I. stolonifera), sea oats, cakile, etc.

Detritivores.
There is an abundant community of detritivores supported by organic carbon that filters down into the sand from the marine waves. The wave action ensures an adequate supply of oxygen. These include especially crustaceans, mollusks, and polychaete worms.

Thixotropy - This allows critters to exploit the surf zone. When sand is covered and/or infused with water, it is very stable until agitated. Have you ever noticed that you can stand in the surf and not sink, but, if you wiggle your toes as the surf runs out, you sink. This is thixotropy. Many beach critters, such a mole crabs, take advantage of this by quickly moving about in the surf with the incoming waves and then, by agitating the sand with their limbs, rapidly disappearing with the outgoing surf. If thixotropy did not happen, fish would eat them immediately.

Primary consumers - insects, seed eating birds, nutria, etc.

Secondary consumers - shorebirds, fish, skunks, frogs, snakes, armadillos, etc.

Tertiary consumers - Sharks, Peregrin Falcons, Ospreys, humans.

For the next section, refer to the adjacent figure "Anatomy of the Shore."
A. Coast - The strip of land affected by the sea, extending landward from the beach to the first major change in terrain. On our beaches, it begins at the seaward edge of the dune field and extends as far inshore as do the effects of the sea. Along a low marshy coast, it is marked by the first permanent land vegetation.

B. Shore, or beach - This is a narrow strip of land in contact with the sea that lies between high and low tide. If composed of loose materials (as our beaches are), regardless of size, they are properly called a "beach."

1. Backshore - edge of the "coast" to the edge of the foreshore (where the beach slants toward to sea). The backshore is horizontal to sloping toward the coast. Berm - flat area of the backshore.
2. Foreshore, or beach face - between the backshore and the edge of the sea at low tide; tends to be flatter with finer sands and steeper with coarser materials. When wave action cuts a vertical cliff into the edge of the beach, this is called a beach scarp.
3. Berm crest - sharp break in the slope between the backshore and the foreshore, if the two can be differentiated.

C. Inshore, or surf, zone - This is located seaward from the foreshore to just beyond the breaker zone. It includes:

1. Longshore bars - these are raised zones of sand parallel to the beach. They remain in the same general area and are never exposed.
2. Trough - deep area in front of the longshore bar.
3. Ridges - Ridges form in shallow water and are similar in appearance to longshore bars, but instead of remaining in one place they move toward the foreshore. When first formed, they are submerged at low tide; as waves move sand over their leading edge, they slowly move shoreward and a) become exposed at low tide, then b) fuse to the foreshore (a process that takes from days to weeks).
4. Runnels - deep area in front of the ridge. These (or troughs if runnels are absent) are where longshore currents travel; they are caused when waves strike the beach at an angle, and then move parallel to the beach.

D. Offshore or continental shelf - from the seaward edge of the breaker zone to the edge of the shelf (at about 200 m). Waves affect this area only during storms.

Surfzone processes - These are governed by:

1. near shore currents - these transport sediment and erode formations.
2. tides - As these change the sea level, they spread the effects of the waves.
   • neap tides - lowest highs and highest lows; have the minimum tidal range. These occur when the moon is perpendicular to the plane of the earth and sun.
     
   • spring tides - highest highs and lowest lows; maximum tidal ranges. These occur when the moon is on the same plane as the earth and sun and has its maximum pull, in concert with the sun, on the water masses of earth.
     
3. waves - First, some terminology:
   • crest - the top of the wave
   • trough - the lowest portion on either side of a wave.
   • height - vertical distance from the crest to the trough.
4. wave length - horizontal distance from the center of a crest to center of an adjacent crest.
5. period - time it takes for a wave to pass a point.

Wave Terms

Waves crossing the open sea have little effect on the bottom. When water depth (d) is greater than ˝ the wave length (L), then it is considered a deep water wave. When d<˝L, then it is a shallow water (or shoaling) wave (interacting with the bottom).

As waves move to shore, the period remains the same, but the speed (= phase velocity) decreases due to friction. This causes the wave length to decrease and the height of the wave to increase. As its height/length ratio increases, it becomes more unstable and finally breaks. Each breaking wave releases a bit of its energy. If it crosses several bars, it continually loses energy, so the next breaker is likely to be smaller.

Movement of particles in waves (see adjacent figure"Particle motion in waves" from W. T. Fox. 1983. At the Sea's Edge. Prentice Hall Press.):

1. Deep water waves - motion is generally circular (called a wave orbit and its diameter is equal to the wave height). See fig. 3-6. As one goes deeper into the water, the diameter of the circle decreases so there is less motion at depths.
   • Rule - For each 1/9th of the surface wave length that one goes beneath the surface, the wave orbit is cut in half.
   • One can calculate the depth where water turbulence is not affected by storms. This is very important to submarines!
2. Shallow water (or shoaling) waves - Wave orbit becomes more elliptical (see fig. 3-10), so there is more shoreward movement. At the bottom, it is horizontal and the particle moves back and forth (see fig. 3-11: shoreward under the crest; seaward under the trough).

Standing waves - See adjacent figures "Standing waves, 2 pp." from W.T. Fox. 1983. At the Sea's Edge. Prentice Hall Press.

These are waves that are reflected back with little loss of energy, such as from a wall or steep shore. But if wave energy is low and even (long period swells), the same reflection occurs (seen along most beach faces, such as Destin, Navarre, Gulfshores, etc.).

See figs. 3-15 and 3-16 to see how the standing wave moves.

Water motion beneath the antinode is vertical; beneath the node it is horizontal in the opposite direction of the wave ( see fig. 3-17), so a standing wave tends to build bars (see fig. 5-7). More erratic waves tend to move the bars and otherwise destroy them.

The spacing of bars is directly proportional to the wave length of the standing wave.

Once bars are established, they become breaking sites for shallow water (shoaling) waves. This occurs not only because of the effect of shallower water, but since bars are under the antinode, they get the effect of adding the shoaling and standing waves.

Lithophide Stone (Beach Rock)
These flat stones are usually found in coastal deposits (often washed out on the beach front). They are an indication that the beach is eroding and that the spot where they were found used to be the rear of the barrier island. Where do they come from? Lithophide stones are formed in washover zones at the rear of barrier islands, at the interfaces of beach/marsh and water/sand. Methane is produced in marsh areas. When the methane reacts with shells in the presence of fine sands, a carbonate cement is formed. This becomes the lithophide stone. They are usually irregular in shape, though almost always flat. Holes are usually caused by a plant growing through them or them forming around something that has either fallen or eroded away. These stones may also form as a result of iron interacting with its surrounding environment.

Habitat Table of Contents

X. OFFSHORE AREAS.
See the adjacent figure "Features of the Sea" for proper terminology for the various zones of the sea.

These areas are greatly affected by organic materials from the estuaries and water and sediment from the Mississippi River (361 billion gal/day).

Primary producers
All primary producers in this zone are phytoplankton, but much energy comes from the organic material derived from coastal marshes. Primary consumers as basically the same as are present in inshore salt waters: menhaden, mullet, crustacean larva, many fish larva, etc.

Secondary consumers include almost every fish you can name, plus sea turtles, sea birds, and people!

Tertiary consumers are also like the estuaries: sharks, ospreys, people, and more.

What causes the richness of the shelf fauna off Barataria and Terrebone Bays? A freshwater "wall," formed by the outflow of the Mississippi River, exists to the southeast and south. Salt water fish can't penetrate this wall, so they can't emigrate.

HYPOXIC ZONES
Also noted in this area is an occasional expanse of water which is oxygen deficient (a zone of hypoxia). Oxygen deficient zones are correlated with high freshwater discharge and high temperatures. These "dead zones," as they have been called, appear to occur when the following combinations of events happen:

1. There is relatively low discharge of freshwater, so there is little turbulence and the discharged freshwater sheets out over the salty sea water and there is very little exchange between the horizontally stratified layers of water.
2. Temperatures are high.
3. Organic material that has washed out of the bays decomposes and consumes oxygen. There is no other source for oxygen since the waters are stratified.
4. The freshwater discharge may (and usually does) contain vast quantities of nutrients (mostly resulting from agricultural run-off of fertilizers). These induce huge algal blooms. These algae either die and consume oxygen as they decompose or they are eaten by zooplankton. Their presence in large numbers will certainly cause the growth of a large zooplankton community. These zooplankton are constantly defecating and dying (if not being eaten by a plankton feeder such as menhaden, manta rays, comb jellies, and the like); these fecal pellets and dead zooplankton settle to the bottom and decompose, thus consuming even more oxygen.

In hypoxic areas, species that can leave do, and those that can't die.

JUBILEES
An interesting occurrence is associated with these events, in the Barataria Basin and, most notably (due to human population density), in Mobile Bay. On occasion, flounder and crabs have been known to come ashore and be so lethargic that they can be scooped up with the hands. This is so exciting that people named these events jubilees. When they occur, no matter what time of day, friends and relatives call and shout,"Jubilee," and everyone comes running with their ice chests. The cause is rather simple. If a dead zone, as described above, forms and an offshore wind blows the surface water away from land, the oxygen deficient bottom water upwells. Normally swimming fish such as redfish and speckled trout simply swim away. If there are bottom dwelling species such as flounder and crabs between shore and the dead zone, they will crawl ashore as the oxygenless water forces them toward land. They are easily picked up due basically to suffocation from the oxygen deficient water that they are avoiding. If you get a chance, don't miss a jubilee!!!

THE VALUE OF OIL AND GAS RIGS AND PLATFORMS IN THE GULF
Of the 4500+ oil and gas related structures in the Gulf of Mexico, 90% are within Louisiana waters. Since the first offshore platform was constructed in 1947 in Ship Shoal (about 12 miles south of Terrebonne Parish), they have been very important in two ways: 1) they recently supplied our nation with 25% of its oil and gas requirements, and 2) they serve as hard structures (in an otherwise soft bottom environment) for reef species to grow (barnacles, corals, and all sorts of other reef animals). The latter, in conjunction with the cover provided, make the structures ideal habitat for all sorts of commercial and sport fish, especially snapper, grouper, cobia, amberjack, and various mackerels.

Since the structures have such value to fisheries, their removal caused concern. Senator John Breaux sponsored the National Fishing Enhancement Act of 1984 to encourage coastal states to establish artificial reef programs. This was followed by the Louisiana Fishing Enhancement Act of 1986 (LFEA) which set the standards for our state's program. It formed the Louisiana Artificial Reef Council to give oversight to the program and the Louisiana Artificial Reef Trust Fund (LARTF) to support it. Louisiana Department of Wildlife & Fisheries, in cooperation with the Louisiana Geological Survey and the Coastal Studies Institute (of LSU's Center for Energy and Environmental Research), administers the program.

It has been the responsibility of the oil and gas company to remove the structure within one year of when it completed production. This was normally done by taking the structure to land and dismantling it - a very expensive endeavor. LFEA gave them a new option. They could now scuttle the structures, thus saving large sums of money and retaining the resource. Each company must pay LARTF an amount equal to one half its savings realized by scuttling the structure rather than dismantling it.

Of course, there are controls. There are prohibited areas such as shipping lanes, known commercial fishing grounds, shallow waters, and the like. The decision of the fate of each structure is taken seriously and not all will qualify for use in the artificial reef program.

The beauty of the program is that everyone wins: we keep the resources, industry saves lots of money, and our program is funded without tapping the state's general fund.

ANOTHER POTENTIAL WIN-WIN SOLUTION.
At the Institute of Recyclable Materials at LSU, studies are underway to research the use of compressed gypsum blocks, made from gypsum by-product from the phosphate fertilizer industry, as a potential growth substrate for marine organisms. Early success may lead to a solution to our expanding piles of gypsum and the need for growth substrate in the northern Gulf of Mexico.

Habitat Table of Contents

Course Document List