rockyshores

ECOLOGY: The wasted report

ROCKY SHORES

PHYSICAL FEATURES

Formation

Physical Processes – changes of  slopes, presence of rock pools, gullies (furrows), crevices (cracks), and boulders (stones)

Land-based processes or Historic Geologic Process – erosion, deposition, volcanic or tectonic processes (changes caused by land movement)

 

Physical Characteristics

Its characteristics depend on the prevailing rock types while the profile (shapes) depends on its strata (layers)

The size of the rocky intertidal is determined by the physical environment, and varies with three factors

slope of the substrate (due to currents, ice, salt, sediments, temperature)

tidal range

exposure to wave action (waves and wind)

BIOLOGICAL FEATURES

Zonation Patterns

Zonation refers to the regular appearance of specific plants and animals at specific places along an intertidal area, the area that lies between the low and the high tide mark. Zonation may be noticeably different from one location to another. The pattern of zonation and the daily rhythm of the tides have made rocky shores interesting and relatively easy habitats to observe and study. This is especially true in coastal areas that experience extreme tidal ranges.

SUPRALITTORAL ZONE

Also called as:

Splash Zone

Spray Zone

Supratidal Zone

Exists in areas that may be above the waterline at times while the other portions reach depths of about 10 meters (32.8 feet)

Part of this zone may be reached by extreme high water of spring tides, but most of its water comes from wave splash

Dominant organisms are periwinkles

The greatest challenges facing by the organisms living in this zone are drying and thermal stress. Constant spray of seawater that evaporates also results in high salt levels.

Organisms with habitats in this area have adaptations that help them retain moisture. They can either: (a) obtain oxygen from the air or (b) store sufficient oxygen in their tissues to endure many hours out of the water. Additionally, they need to be hardy enough to withstand periodic motion and pounding of waves Barnacles, periwinkles, and limpets are example of organisms adapted to life in the supralittoral zone.

EULITTORAL ZONE

Also called as:

Midlittoral Zone

Mediolittoral Zone

Foreshore

The broadest part of the rocky intertidal

It extends from the spring high tide line to the neap low tide line, which is rarely inundated (flooded). The wave action and turbulence of recurring tides shaped and reforms cliffs, gaps, and caves, offering a huge range of habitats for sedentary (inactive) organisms.

Exposed sites show a wider extension and are often divided into further zones

SUBLITTORAL ZONE

Also known as:

Neritic Zone

This area is rarely exposed to air – only at extremely low tides. With ample water, nutrients and sunlight, this is highly productive region in most coastal ecosystems. One challenge to life here, therefore, is massive competition.

If the  middle shore has the greatest species diversity (variety), the lower shore is most prolific (abundant, productive, fertile)

It starts immediately below the Eulittoral Zone. The zone is permanently covered with seawater. In physical oceanography, the sublittoral zone refers coastal regions with significant tidal flows and dissipation (indulgence), including non-linear flows, internal waves, river outflows and oceanic fronts. In practice, this typically extends to the edge of continental shelf, with depths around 200m. In marine biology, sublittoral refers to the areas where sunlight reaches the ocean floor, that is, where the water is never so deep as to take it out of the photic zone. This results in high primary production and makes the sublittoral zone the location of majority of sea life. As in physical oceanography, this zone typically extends to the edge of continental shelf. The benthic zone in the sublittoral is much more stable than in the intertidal zone; temperature, water pressure, and the amount of sunlight remain fairly constant. Sublittoral corals do not have to deal with as much change as intertidal corals. Corals can live in both zones, but they are more common in sublittoral zone.

Within the sublittoral, marine biologists also identify the ff:

The INFRALITTORAL ZONE is the algal dominated zone to be 5m below the water mark.

The CIRCALITTORAL ZONE is the region beyond the infralittoral. That is, below the algal zone and dominated by sessile animals such as oysters

Shallower regions of the sublittoral zone, extending not far from the shore, are sometimes referred as SUBTIDAL ZONE.

ECOLOGICAL FEATURES

Since rocky shores are transition zones between land and sea and are influenced by the daily rise and fall of the tides, the animals and plants that live there are well-adapted to a number of situations. These adaptations help them deal with specific physical processes or biological factors that may limit their distribution, growth, and survival. All adaptations have some purpose in enhancing the ability of an organism to survive.

 

 

CAUSES OF ZONATION (OR THE LIMITING FACTORS):

 

Critical tide levels –Criticaltide levels are points exhibiting sharp increases in exposure time over short distances in rocky intertidal. These results to (a) the maximum time of continuous emergence or submergence are of primary importance; (b) the zonation reflects different tolerances of organisms to exposure to air (especially temperature and desiccation). Tide per se does not cause the limit, but exposure time to air is the major factor

 

Drying Out (Desiccation) – The processes that affect the physical characteristics of the rocky shore also affect life in the intertidal zone. To be successful, animals and plants must have evolved special adaptations to deal with these stresses. For example, as the tide rises and falls, organisms may dry out. This can occur not only as a result of sun, but also wind. Some organisms have developed an ability to tolerate high water loss. Others have developed mechanisms to retain water.

 

 

Temperature – Changing temperatures have demonstrable effects on many animals. On rocky shores, air temperatures may range seasonally from -30°C to +30°C. Even in summer, air temperatures reaching +30°C are contrasted against water temperatures that may only be 5°C. Again, the shelled animals deal with this limiting factor much in the same way they deal with drying out. The barnacle also has this wonderful ability to close up tightly, retain water, and stay moist and cool during low tide in the summer and relatively warm and moist in the winter.

 

Changing Salinity (Salt) – Intertidal organisms also deal with the potential of being drenched by fresh water during torrential downpours, or being in tide pools where salinity concentrations can be reduced over longer periods of time by rain. Salinity also changes with increasing evaporation potential. As temperature and / or wind increase, tide pools can become more saline.

 

 

Light and Dark – Light is another physical factor that limits the distribution and success of animals living intertidally. Light is essential for photosynthesis and therefore for plant growth.

 

Light is also a stimulus that many animals respond to. Because light is essential for plant growth and some animals are plant feeders, there may be a positive response by herbivores to light. As a result, they may be attracted to it. Others may respond negatively to light, searching for shaded areas to hide. Shade represents protection from predators and from extremes in environmental conditions.

 

 

COMPETITION and PREDATION – Competition is the common use of space, food, or light by a number of animals and/or plants of the same or different species. On the rocky shore both animals and plants need space. Some species tend to crowd out or restrict others.

 

The rocky shore is filled with examples of predator/prey relationships or predation. Predation is the act of one animal eating another and on the rocky shore these food chains and webs can be readily seen in action. Predatory animals can alter the composition of species within an ecosystem. In fact it is possible for a predator to eliminate a species, making the area more inviting for other species. Like carnivorous predators, grazing herbivores (plant eaters) can alter species composition within an area.

 

 

 

Availability Of Food – In a marine environment many animals have adaptations that allow them to take small food particles out of the water through filtration. These filter feeders therefore are dependent on the amount of time they spend in the water. Their size and distribution on a rocky shore is determined by this immersion time.

 

ADAPTATIONS

 

RESISTANCE TO WATER LOSS

The simplest mechanism for avoiding water loss in highly motile animals, e.g., crabs, is to move from exposed surfaces into cracks and crevices where it is moist & cool i.e., just avoid adverse conditions by seeking a suitable microhabitat the immediate environment of an organism, especially a small organism

 

Many sessile and sedentary simply are adapted to tolerate severe water loss from their tissues some algae, e.g, Enteromorpha can survive 60–90% water loss; some chitons: 75 % water loss; some limpets: 30–70 % water loss

 

 Some species have mechanisms for prevention of water loss barnacles and bivalves can just clam up; some limpets have a “home scar” that their shells fit exactly so that they can clamp down in home scar to reduce water loss; some littorines have an operculum that completely seals off aperture to reduce water loss; The snail Smaragdinella calyculata covers itself with mucus that reduces water loss

 

MAINTENANCE OF HEAT BALANCE

Mechanisms to avoid over-heating at low tide

 

Reduce heat gained from environment

Have a high volume: surface ratio (i.e., be big)

A large body size means less surface area relative to volume and less area to absorb heat;

A larger body also takes longer to heat up;

However, a large body is a disadvantage in heavy wave action

Some nerites resolve this problem by increasing their internal volume by modifying interior structure of shell

The shell can then hold more tissue and more water compared to subtidal snails.

 

Reduce the area of body tissue in contact with the substrate

Periwinkles survive substrate temperatures of up to 49°C [120°F], because the snail attaches its shell to the substrate with a mucous “curtain” and withdraws its foot into shell

The dried mucus serves as insulation between the snail and the substrate

 

Increase sculpture (on shells)

Ridges and spines act like radiator fins to facilitate heat loss

 

MECHANICAL STRESS

Intertidal organisms must have the ability to resist smashing and tearing effects of waves breaking

The simplest adaptation is to cement the skeleton to substrate, e.g., barnacles, oysters, vermetids

One strategy is to form a strong, but not permanent, attachment to the substrate, e.g., holdfast of algae, abyssal threads of mussels

Another strategy is to possess a strong foot and thick shell, e.g., most intertidal gastropods

 

RESPIRATION

Because of the risk of desiccation at low tide, gills must be enclosed in a cavity to prevent them from drying, e.g., barnacles, mollusks

FEEDING

Intertidal animals are exposed to desiccation and predation when feeding

Therefore, feeding activity is usually restricted to a time when the intertidal is either covered by the sea or the substrate is wet from wave splash

SALINITY STRESS

During heavy rains, intertidal animals must close their shell or clamp onto the substrate to keep freshwater out

 Therefore, adaptations for this stress are similar same to adaptations to resist desiccation

REPRODUCTION

 Because of the sedentary or sessile nature of most intertidal organisms, they must rely upon planktonic larval development for dispersal of their young

Also, spawning usually occurs during spring tides to insure that gametes reach open sea, and spawning is mostly timed for falling tides

 

SANDY SHORE

 

PHYSICAL FEATURES

 

Formation

Most beach sand comes from glacial erosion. Eroding forces break down rocks into smaller particles. In the past, during glaciation, glacial rivers transported sand to the coast. Today, headlands and cliffs are eroded and sand is formed.

 

Wind and water sort the sand.

 

SAND is a naturally occurring granular material composed of finely divided rock and mineral particles. The composition of sand is highly variable, depending on the local rock sources and conditions, but the most common constituent of sand in inland continental setting and non-tropical coastal settings is silica (silicon dioxide or SiO2), usually in the form of quartz

Sandy Shores also called as “beaches” in which serve as buffer zones or shock absorbers that protect the coastline, sea cliffs, or dunes from direct wave attack.

BEACH referred as the zone above the water line at a shore of a body of water, marked by an accumulation of sand, stone, or gravel that has been deposited by the tides or waves. It may be also refer as:

 

Physical Characteristics

These can be categorized in:

Shape of the beach (due to currents, ice, freshwater, salt, sediments, temperature)

Tidal range

Exposure of waves (and wind)

BIOLOGICAL FEATURES

 

Fauna of Sandy Shores

 

The fauna of sandy shores:

EPIFAUNA, living on the surface

INFAUNA, which live in burrows in the sediment. Most infauna either occupies permanent or sedimentary tubes within the sand or mud is able or able to burrow rapidly into the substrate.

MACROFAUNA which feed off particles within the sand as they move below the surface, and the interstitial fauna, which are small enough to move between particles. They are large enough to be seen by the naked eye. They are often abundant and, in some cases, attain exceptionally high densities. They are larger than 1mm (0.04 inch) such as sponges, crustaceans, anthozoans, polychaete worms

MEIOFAUNA has a size range between 0.1mm and 1mm in size, organisms like cocepods, ostracods, nematodes and gastrotrichs. They have hooks to grab the sand. The biological community of sandy shores varies according to the exposure to the tide and can range from a macrofauna-dominated community in sheltered sites to a microfauna or meiofauna dominated community in exposed sites.

MICROFAUNA, smaller than 0.1mm including diatoms, bacteria, ciliates, amoeba, and flagellates.

 

FAUNA is all of the animal life of any particular region or time. They are the benthos beneath the seafloor. The corresponding term for plants is flora fauna and other forms of life such as collectively referred to as BIOTA.

Zonation

DUNES – a hill of sand built by eaolian processes. Dunes occurred in different forms and sizes, formed by interaction with the wind. This is where you can see the Primary (active) and Secondary (fixed) Dunesand also, swale, the hollow between dunes, often close enough to the water table so that marsh plants or peatland plants can get established. Stagnant freshwater pools can develop

BACK BEACH OR BACKSHORE – rarely touched by wave action and ends at the edge of the first dune

FORESHORE or SURF ZONE – the sloping portion of the beach between high and low tide. It consists of berm which isnearly horizontal and is formed when the waves deposit sand. A storm berm can mark the highest limit of storm waves. Several berms can occur at spring and neap tide levels.

There are THREE BASIC TYPES OF BEACHES:

REFLECTIVE BEACH – this type occurs when conditions are calm and/or the sediment is coarse. There is no surf zone and waves flow upon the beach. It reflects a major part of the incoming wave.

INTERMEDIATE BEACH – this was formed when bigger waves cut back reflective beach and spread out its sediments to form a surf zone

 DISSIPATIVE BEACH – this was created when wave action is strong and/or sediment particle size is fine. This type has a flat and maximally eroded beach.

ECOLOGICAL FEATURES

STRESS AND SURVIVAL

The beach is not an easy place to live. Waves constantly pound the shore; wind desiccates plants and carries salt and sand inland; temperatures fluctuate during the course of a day; fresh water is not easy to come by; and the shifting sand leaves small organisms in constant danger of being crushed

ADAPTATIONS

MOBILITY – burrowing, vertical tidal migrations

RESPIRATION – facultative anaerobes, evaporative cooling

REPRODUCTION – iteroparous (frequent time); semelparous (once a year)

PROTECTION– burrowing; tidal migration; phenotypic plasticity (escaping movement)

 

 FACTORS CURRENTLY IMPACTING SANDY SHORES.

STORMS – they represent the greatest natural hazard faced by sandy-shore animals

DISRUPTION OF SAND TRANSPORT – This has resulted most obviously from the construction of harbours, breakwaters, jetties (piers) and groins, which deprive down-drift beaches of sand while updrift sand accumulates and advances seawards.

BEACH NOURISHMENT AND BULLDOZING - Beach nourishment by importing sand and bulldozing to restore dunes, by transferring sand from low to high levels, have become common practices in some parts of the world, such as North Carolina, USA, which face ongoing beach erosion from man-made structures or from natural causes (Leonard et al. 1990; Peterson et al. 2000).

POLLUTION – oil pollution; organic enrichment (that leads to a lowering of oxygen tensions within the sand and a consequent upward encroachment of anoxic ‘black layers’. This in turn results in impoverishment of the fauna); Factory effluents

MINING - removal of sand itself, mining may take place for precious stones, such as diamonds, or  for various minerals

TRAMPLING - direct damage to vegetation and the fauna,but also physical impact on the substratum, notably compaction, which influences soil moisture, run-off, erosion, vegetation and micro-organisms (Liddle & Moore 1974)

 

BEACH CLEANING – deprives the ecosystem of valuable nutritional input, semi-terrestrial forms such as talitrid amphipods, oniscid isopods and ocypodid crabs being the most deprived

GROUNDWATER CHANGES - intensified by the hardening of surfaces, so that surface water from rain is diverted to storm water drains instead of sinking into the soil

BAIT COLLECTING - populations are often drastically reduced by these activities, they are seldom if ever eliminated, as they reach a level at which the effort of collecting fails to justify the reward

Fishing. Recreation/tourism, Littering

 

 

 

 

 

 

 

MUDDY SHORES

 

The term “MUD” is loosely applied to deposits containing a high proportion of silt or clay particles. Muddy shores develop on places where clay and silt (particles finer than sand) are deposited by river currents or by tidal action.

 

result of the erosion and deposition of the surrounding coastal bedrock

 

Catastrophic events sometimes create situations that completely alter the properties of a mudflat for short periods of time

 

Muddy shores, with their finer sediment, have smaller interstitial spaces and these trap organic matter.Smaller spaces mean that drainage when the tide drops is less and so muddy shores hold on to their water

 

Mud, deposited in calm conditions, will be a flatter habitat (hence the term mudflat) and water is unlikely to drain. This minimal desiccation negates much in the way of zonation on the shore. However, the diversity of species is likely to be higher than sand. Smaller creatures will be commonplace

In places where the velocity of the water is low enough the fine particles will sink to the bottom where bottom organisms will fixate them

 

It provides source of organic material for organisms living within and on top of the mud, called the endo- and epibenthos.The benthic communities on muddy shores are often low in diversity and productivity, due to limited oxygen restricting chemical and biological degradation processes

 

While feeding on surface detritus, Baltic Macoma produces incredible amounts of faeces (droppings). The total daily production of Macoma droppings, in the Minas Basin, may be as much as 6 x 106 kg of dry sediment. What this provides is a surface around which bacterial colonies can grow and become a valuable food source

MANGROVE SWAMPS

 

CHARACTERISTICS

 

Specialized Root System

Woody plants that grow at the interface between land and sea in tropical and sub-tropical latitudes where they exist in conditions of high salinity, extreme tides, strong winds, high temperatures and muddy, anaerobic soils. There may be no other group of plants with such highly developed morphological and physiological adaptations to extreme conditions.

Morphological specializations include profuse lateral roots that anchor the trees in the loose sediments, exposed aerial roots for gas exchange and viviparous water-dispersed propagules

AERIAL ROOTS:

 

Breathing Roots (Pneumatophores) – Special vertical roots, called pneumatophores, form from lateral roots in the mud, often projecting above soil permitting some oxygen to reach the oxygen-starved submerged roots.

Stilt Roots- are the main organs for breathing especially during the high tide. They are very common in many species of Rhizophora and Avicennia. Aeration occurs also through lenticels in the bark of mangrove species.

 

Reproductive Strategies Of Mangroves

Virtually all mangroves share two common reproductive strategies:

Dispersal

Vivipary

Coping With Salt

Because of their environment, mangroves are necessarily tolerant of high salt levels and have mechanisms to take up water despite strong osmotic potentials. Some also take up salts, but excrete them through specialized glands in the leaves. Others transfer salts into senescent leaves or store them in the bark or the wood. Still others simply become increasingly conservative in their water use as water salinity increases.

DEFINITIONS

The term “mangrove” used to refer to a habitat comprised of a number of halophytic (salt-tolerant) plant species, of which there are more than 12 families and 50 species worldwide.

 

They are found in warmer areas between the latitudes of 32 degrees north and 38 degrees south, along the tropical and subtropical coasts of Africa, Australia, Asia and North and South America. In the U.S., mangroves are commonly found in Florida.

 

Mangrove plants have a tangle of roots which are often exposed above water, leading to the nickname “walking trees.” The roots of mangrove plants are adapted to filter salt water, and their leaves can excrete salt, allowing them to survive where other land plants cannot. Thus, mangrove is a non-taxonomic term used to describe a diverse group of plants that are all adapted to a wet, saline habitat.

 

The term “mangrove” often refers to both the plants and the forest community. To avoid confusion, Macnae (1968) proposed that “mangal” should refer to the forest community while “mangroves” should refer to the individual plant species. Duke (1992) defined a mangrove as, “…a tree, shrub, palm or ground fern, generally exceeding one half metre in height, and which normally grows above mean sea level in the intertidal zone of marine coastal environments, or estuarine margins.” This definition is acceptable except that ground ferns should probably be considered mangrove associates rather than true mangroves.

TAXONOMY

Mangroves are not a single genetic group but representing a large variety of plant families that are adapted to tropical intertidal environment. Tomlinson (1986) recognized three groups of mangroves:

Major mangrove species – the strict or true mangroves, recognized by most or all of the following features:

 They occur exclusively in mangal.

 They play a major role in the structure of the community and have the ability to form pure stands.

 They have morphological specializations – especially aerial roots and specialized mechanisms of gas exchange.

They have physiological mechanisms for salt exclusion and/or excretion.

They have viviparous reproduction.

 They are taxonomically isolated from terrestrial relatives. The strict mangroves are separated from their nearest relatives at least at the generic level, and often at the sub‐family or family level.

Minor mangrove species - less conspicuous elements of the vegetation and rarely form pure stands.

Mangrove associates

 

PHYSIOLOGY

Salt regulation

Mangroves are physiologically tolerant of high salt levels and have mechanisms to obtain fresh water despite the strong osmotic potential of the sediments (Ball, 1996). They avoid heavy salt loads through a combination of salt exclusion, salt excretion, and salt accumulation

Salt concentrations in the sap may also be reduced by transferring the salts into senescent leaves or by storing them in the bark or the wood (Tomlinson, 1986).

As water salinity increases, some species simply become increasingly conservative in their water use, thus achieving greater tolerance (Ball and Passioura, 1993)

In the wet season, the fine root biomass increases in response to decreased salinity of the surface waters, directly enhancing the uptake of low-salinity water (Lin and Sternberg,1994).

Most mangrove species directly regulate salts.

Because mangrove roots exclude salts when they extract water from soil, soil salts could become very concentrated, creating strong osmotic gradients (Passioura et al., 1992).

Transpiration rates vary with season, being higher in the dry season than in the wet season. This corresponds to changes in stomatal movement..This includes increases in vapor pressure deficit and osmotic potential of the substrata (Naidoo and Von-Willert, 1994).

Photosynthesis

Temperature-induced changes in the relative rates of photosynthesis and respiration, in turn, influence overall growth rates.

Strong sunlight can also reduce mangrove photosynthesis through inhibition of Photosystem II (Cheeseman et al., 1991). The photosynthetic rates of mangroves saturate at relatively low light levels despite their presence in high sunlight tropical environments. The fairly low photosynthetic efficiency may be related to the concentration of zeaxanthin pigments in the leaves (Lovelock and Clough, 1992). To prevent damage to the photosystems, the mangroves dissipate excess light energy via the xanthophylls cycle (Gilmore and Bjorkman, 1994) and through the conversion of O2 to phenolics and peroxidases (Cheeseman et al., 1997).

 

REPRODUCTION

Reproduction, dispersal and establishment Bhosale and Mulik (1991) described four methods of mangrove reproduction: Viviparity, Cryptoviviparity, normal germination on soil, and vegetative propagation.

 

Dispersal by means of water and;

Vivipary – means that the embryo develops continuously while attached to the parent tree. They may grow in place, attached to the parent tree for one to three years, reaching length up to one meter, before breaking off from the parent plant & falling into the water, these seedling then lodged in the mud where they quickly produce additional roots and begin to grow

 

SUMMARIZATION

Rhizophora mangle
red mangrove

Avicennia germinans
black mangrove

Laguncularia recemosa
white mangrove

Flowering Season

all year, but maximum in late spring and summer

spring and early summer

spring and early summer

Shape of Propagule

cigar, alrge green bean

oblong/elliptical, lima bean

flattened, pea green when fall, sunflower seed

Length of Propagule

15 cm

2 - 3 cm

less than .5 cm

Degree of Vivipary

extensive while on tree

intermediate?

“semi-viviparious”
germination during dispersal

Obligate Dispersal

40 days

14 days

8 days

Root Establishment

15 days (either vertical or horizontal)

7 days

5 days

Viable Longevity

365 days

110 days

35 days

Seedling Mortality

lowest

intermediate

highest

Sucession

due to emgbryonic reserves, can establish under canopy and wait for tree to fall

need adequate light; need strand period of 5 days above tide

need adequate light; need strand period of 5 days above tide to hold soil

 

 

 

               

 

 

 

ADAPTATION

Red Mangroves(Rhizophora mangle)

Closest to the water - in fact in the water at high tide

 

The roots of the red mangrove are distinctive, with long arching aerial prop roots that help anchor the plant in the sediment. These roots are firmly mired in the organic muck; decomposition in this muck (manure) releases nutrients that the tree can use, but there is no oxygen.  The roots of the red mangrove are able to obtain water from the ocean by pumping magnesium ions into the root.  These positive ions force other positive ions, such as sodium, out of the root.  The high concentration of magnesium in the root creates a high osmotic potential, and this in turn attracts water in from the surrounding seawater. The net effect is to set up “reverse osmosis” or to exclude salt from the root.  Oxygen to support the cells moving all those magnesium ions is provided through air channels in the roots. 

Red mangroves are distinguished by the dendritic network of aerial prop roots extending from the trunk and lower branches to the soil. The prop roots are important adaptations to living in anaerobic substrates and providing gas exchange, anchoring system, and absorbing ability. Within the soils, microroots stabilize fine silts and sands maintaining water clarity and quality.

 

Life Cycle of the Red Mangrove: Flowers of the red mangrove (above, right) are fertilized and begin to develop.  The propagule or seedling, does not drop from the tree immediately, but continues to grow in place, reaching about 6" in length (15cm).  When it does drop off, the propagule (also known as a pencil) can float.  It is heavier at the root end, and eventually the lower end makes contact with soil and begins to grow (below).  If there are no storms or other disturbances, the red mangrove seedling and its companions can advance the shoreline as they stabilize the soils beneath them.  In nature however, storms tend to keep the system in balance.  Human cutting of mangroves can cause severe erosion problems during major storms or tsumani, as we learned in 2004 and 2005 with the Indonesian Tsumani and Huricane Katrina.  See also:

http://www.earthisland.org/map/katrina.html

 

 

 

 Black Mangroves (Avicennia germinans)

Next inland, usually above the high tides

These trees deal with salt by excreting it onto the leaves; also, like the red mangroves, the roots of the black mangrove are metabolically very active.  To supply the roots with oxygen in the oxygen-poor sediments the black mangrove has an extensive development of pneumatophores (species have root extensions that take in oxygen for the roots).  These structures grow up out of the soil and their spongy construction helps convey oxygen down to the roots.  Unlike the red mangrove which actively excludes ocean salts from entering at the root, the black mangrove allows the salt to enter but excretes it on the surface of the roots and the leaves.  You can often find salt crystals on the leaves of the black mangrove.  It can survive the higher salinities then the red mangrove; such higher salinities might be expected further up on the beach where the black mangroves are found.

 

White Mangroves (Laguncularia racemosa)

Neither aerial prop roots or pneumatophores are usually visible (but either may be present if conditions warrant; the pneumatophores take the form of peg roots).   Like the black mangrove, the white mangrove excretes salts on the leaf surface.

You may have noticed that the scientific names for the mangroves differ greatly (Rhizophora mangle, Avicennia germinans, Laguncularia racemosa).  This is because the word “mangrove” indicates an ecological rather than a taxonomical grouping.   For instance, when we speak of oaks or maples we are referring to trees of the genera Quercus and Acer, respectively.  However, when we speak of mangroves we are speaking of tropical, salt-tolerant trees that grow along the shore.  Hence, the 3 species of mangrove mentioned all hail from different genera and are not closely related to each other.

Another interesting tidbit is the way the trees segregate themselves in the habitat.  Red mangrove seeds are much larger than either of the other two and simply aren’t carried very far inland.  Black mangrove seeds are smaller and will be washed further up the beach by the tides.  White mangrove seeds are the smallest and are carried the furthest inland.  Thus, each tree species has a seed that is adapted to be carried to the appropriate habitat for the tree to grow.

 

Buttonwood

Buttonwoods grow to 12 to14 m (39 to 46 ft) in height in a shrub or tree form,but do not produce a true propagule in Florida (Tomlinson 1986). Bark is greyand very furrowed providing attachment for epiphytes. Leaves are thin, broadto-narrow, and pointed. There are two morphotypes: the green with mediumgreen leaves found on peninsular Florida and the silver with pale pastel greenPage 3-524MANGROVES Multi-Species Recovery Plan for South Floridaleaves historically limited to the Florida Keys but now widespread by nurserypractices. It is thought the silver buttonwood is an adaptation to the rocky, dryhabitats associated with the Keys archipelago. Two glands are found at theapex of the petiole that excrete extra floral nectar and salt. Tiny brownishflowers are found in a sphere on the terminal ends of branches. These producea seed cluster known as the button. Buttonwoods are able to grow in areasseldom inundated by tidal waters. The mangrove adaptations to the osmoticdesert of salt water, also adapted buttonwoods to arid areas of barrier islandsand coastal strands.ROCKY SHORES

PHYSICAL FEATURES

Formation

Physical Processes – changes of  slopes, presence of rock pools, gullies (furrows), crevices (cracks), and boulders (stones)

Land-based processes or Historic Geologic Process – erosion, deposition, volcanic or tectonic processes (changes caused by land movement)

 

Physical Characteristics

Its characteristics depend on the prevailing rock types while the profile (shapes) depends on its strata (layers)

The size of the rocky intertidal is determined by the physical environment, and varies with three factors

slope of the substrate (due to currents, ice, salt, sediments, temperature)

tidal range

exposure to wave action (waves and wind)

BIOLOGICAL FEATURES

Zonation Patterns

Zonation refers to the regular appearance of specific plants and animals at specific places along an intertidal area, the area that lies between the low and the high tide mark. Zonation may be noticeably different from one location to another. The pattern of zonation and the daily rhythm of the tides have made rocky shores interesting and relatively easy habitats to observe and study. This is especially true in coastal areas that experience extreme tidal ranges.

SUPRALITTORAL ZONE

Also called as:

Splash Zone

Spray Zone

Supratidal Zone

Exists in areas that may be above the waterline at times while the other portions reach depths of about 10 meters (32.8 feet)

Part of this zone may be reached by extreme high water of spring tides, but most of its water comes from wave splash

Dominant organisms are periwinkles

The greatest challenges facing by the organisms living in this zone are drying and thermal stress. Constant spray of seawater that evaporates also results in high salt levels.

Organisms with habitats in this area have adaptations that help them retain moisture. They can either: (a) obtain oxygen from the air or (b) store sufficient oxygen in their tissues to endure many hours out of the water. Additionally, they need to be hardy enough to withstand periodic motion and pounding of waves Barnacles, periwinkles, and limpets are example of organisms adapted to life in the supralittoral zone.

EULITTORAL ZONE

Also called as:

Midlittoral Zone

Mediolittoral Zone

Foreshore

The broadest part of the rocky intertidal

It extends from the spring high tide line to the neap low tide line, which is rarely inundated (flooded). The wave action and turbulence of recurring tides shaped and reforms cliffs, gaps, and caves, offering a huge range of habitats for sedentary (inactive) organisms.

Exposed sites show a wider extension and are often divided into further zones

SUBLITTORAL ZONE

Also known as:

Neritic Zone

This area is rarely exposed to air – only at extremely low tides. With ample water, nutrients and sunlight, this is highly productive region in most coastal ecosystems. One challenge to life here, therefore, is massive competition.

If the  middle shore has the greatest species diversity (variety), the lower shore is most prolific (abundant, productive, fertile)

It starts immediately below the Eulittoral Zone. The zone is permanently covered with seawater. In physical oceanography, the sublittoral zone refers coastal regions with significant tidal flows and dissipation (indulgence), including non-linear flows, internal waves, river outflows and oceanic fronts. In practice, this typically extends to the edge of continental shelf, with depths around 200m. In marine biology, sublittoral refers to the areas where sunlight reaches the ocean floor, that is, where the water is never so deep as to take it out of the photic zone. This results in high primary production and makes the sublittoral zone the location of majority of sea life. As in physical oceanography, this zone typically extends to the edge of continental shelf. The benthic zone in the sublittoral is much more stable than in the intertidal zone; temperature, water pressure, and the amount of sunlight remain fairly constant. Sublittoral corals do not have to deal with as much change as intertidal corals. Corals can live in both zones, but they are more common in sublittoral zone.

Within the sublittoral, marine biologists also identify the ff:

The INFRALITTORAL ZONE is the algal dominated zone to be 5m below the water mark.

The CIRCALITTORAL ZONE is the region beyond the infralittoral. That is, below the algal zone and dominated by sessile animals such as oysters

Shallower regions of the sublittoral zone, extending not far from the shore, are sometimes referred as SUBTIDAL ZONE.

ECOLOGICAL FEATURES

Since rocky shores are transition zones between land and sea and are influenced by the daily rise and fall of the tides, the animals and plants that live there are well-adapted to a number of situations. These adaptations help them deal with specific physical processes or biological factors that may limit their distribution, growth, and survival. All adaptations have some purpose in enhancing the ability of an organism to survive.

 

 

CAUSES OF ZONATION (OR THE LIMITING FACTORS):

 

Critical tide levels –Criticaltide levels are points exhibiting sharp increases in exposure time over short distances in rocky intertidal. These results to (a) the maximum time of continuous emergence or submergence are of primary importance; (b) the zonation reflects different tolerances of organisms to exposure to air (especially temperature and desiccation). Tide per se does not cause the limit, but exposure time to air is the major factor

 

Drying Out (Desiccation) – The processes that affect the physical characteristics of the rocky shore also affect life in the intertidal zone. To be successful, animals and plants must have evolved special adaptations to deal with these stresses. For example, as the tide rises and falls, organisms may dry out. This can occur not only as a result of sun, but also wind. Some organisms have developed an ability to tolerate high water loss. Others have developed mechanisms to retain water.

 

 

Temperature – Changing temperatures have demonstrable effects on many animals. On rocky shores, air temperatures may range seasonally from -30°C to +30°C. Even in summer, air temperatures reaching +30°C are contrasted against water temperatures that may only be 5°C. Again, the shelled animals deal with this limiting factor much in the same way they deal with drying out. The barnacle also has this wonderful ability to close up tightly, retain water, and stay moist and cool during low tide in the summer and relatively warm and moist in the winter.

 

Changing Salinity (Salt) – Intertidal organisms also deal with the potential of being drenched by fresh water during torrential downpours, or being in tide pools where salinity concentrations can be reduced over longer periods of time by rain. Salinity also changes with increasing evaporation potential. As temperature and / or wind increase, tide pools can become more saline.

 

 

Light and Dark – Light is another physical factor that limits the distribution and success of animals living intertidally. Light is essential for photosynthesis and therefore for plant growth.

 

Light is also a stimulus that many animals respond to. Because light is essential for plant growth and some animals are plant feeders, there may be a positive response by herbivores to light. As a result, they may be attracted to it. Others may respond negatively to light, searching for shaded areas to hide. Shade represents protection from predators and from extremes in environmental conditions.

 

 

COMPETITION and PREDATION – Competition is the common use of space, food, or light by a number of animals and/or plants of the same or different species. On the rocky shore both animals and plants need space. Some species tend to crowd out or restrict others.

 

The rocky shore is filled with examples of predator/prey relationships or predation. Predation is the act of one animal eating another and on the rocky shore these food chains and webs can be readily seen in action. Predatory animals can alter the composition of species within an ecosystem. In fact it is possible for a predator to eliminate a species, making the area more inviting for other species. Like carnivorous predators, grazing herbivores (plant eaters) can alter species composition within an area.

 

 

 

Availability Of Food – In a marine environment many animals have adaptations that allow them to take small food particles out of the water through filtration. These filter feeders therefore are dependent on the amount of time they spend in the water. Their size and distribution on a rocky shore is determined by this immersion time.

 

ADAPTATIONS

 

RESISTANCE TO WATER LOSS

The simplest mechanism for avoiding water loss in highly motile animals, e.g., crabs, is to move from exposed surfaces into cracks and crevices where it is moist & cool i.e., just avoid adverse conditions by seeking a suitable microhabitat the immediate environment of an organism, especially a small organism

 

Many sessile and sedentary simply are adapted to tolerate severe water loss from their tissues some algae, e.g, Enteromorpha can survive 60–90% water loss; some chitons: 75 % water loss; some limpets: 30–70 % water loss

 

 Some species have mechanisms for prevention of water loss barnacles and bivalves can just clam up; some limpets have a “home scar” that their shells fit exactly so that they can clamp down in home scar to reduce water loss; some littorines have an operculum that completely seals off aperture to reduce water loss; The snail Smaragdinella calyculata covers itself with mucus that reduces water loss

 

MAINTENANCE OF HEAT BALANCE

Mechanisms to avoid over-heating at low tide

 

Reduce heat gained from environment

Have a high volume: surface ratio (i.e., be big)

A large body size means less surface area relative to volume and less area to absorb heat;

A larger body also takes longer to heat up;

However, a large body is a disadvantage in heavy wave action

Some nerites resolve this problem by increasing their internal volume by modifying interior structure of shell

The shell can then hold more tissue and more water compared to subtidal snails.

 

Reduce the area of body tissue in contact with the substrate

Periwinkles survive substrate temperatures of up to 49°C [120°F], because the snail attaches its shell to the substrate with a mucous “curtain” and withdraws its foot into shell

The dried mucus serves as insulation between the snail and the substrate

 

Increase sculpture (on shells)

Ridges and spines act like radiator fins to facilitate heat loss

 

MECHANICAL STRESS

Intertidal organisms must have the ability to resist smashing and tearing effects of waves breaking

The simplest adaptation is to cement the skeleton to substrate, e.g., barnacles, oysters, vermetids

One strategy is to form a strong, but not permanent, attachment to the substrate, e.g., holdfast of algae, abyssal threads of mussels

Another strategy is to possess a strong foot and thick shell, e.g., most intertidal gastropods

 

RESPIRATION

Because of the risk of desiccation at low tide, gills must be enclosed in a cavity to prevent them from drying, e.g., barnacles, mollusks

FEEDING

Intertidal animals are exposed to desiccation and predation when feeding

Therefore, feeding activity is usually restricted to a time when the intertidal is either covered by the sea or the substrate is wet from wave splash

SALINITY STRESS

During heavy rains, intertidal animals must close their shell or clamp onto the substrate to keep freshwater out

 Therefore, adaptations for this stress are similar same to adaptations to resist desiccation

REPRODUCTION

 Because of the sedentary or sessile nature of most intertidal organisms, they must rely upon planktonic larval development for dispersal of their young

Also, spawning usually occurs during spring tides to insure that gametes reach open sea, and spawning is mostly timed for falling tides

 

SANDY SHORE

 

PHYSICAL FEATURES

 

Formation

Most beach sand comes from glacial erosion. Eroding forces break down rocks into smaller particles. In the past, during glaciation, glacial rivers transported sand to the coast. Today, headlands and cliffs are eroded and sand is formed.

 

Wind and water sort the sand.

 

SAND is a naturally occurring granular material composed of finely divided rock and mineral particles. The composition of sand is highly variable, depending on the local rock sources and conditions, but the most common constituent of sand in inland continental setting and non-tropical coastal settings is silica (silicon dioxide or SiO2), usually in the form of quartz

Sandy Shores also called as “beaches” in which serve as buffer zones or shock absorbers that protect the coastline, sea cliffs, or dunes from direct wave attack.

BEACH referred as the zone above the water line at a shore of a body of water, marked by an accumulation of sand, stone, or gravel that has been deposited by the tides or waves. It may be also refer as:

 

Physical Characteristics

These can be categorized in:

Shape of the beach (due to currents, ice, freshwater, salt, sediments, temperature)

Tidal range

Exposure of waves (and wind)

BIOLOGICAL FEATURES

 

Fauna of Sandy Shores

 

The fauna of sandy shores:

EPIFAUNA, living on the surface

INFAUNA, which live in burrows in the sediment. Most infauna either occupies permanent or sedimentary tubes within the sand or mud is able or able to burrow rapidly into the substrate.

MACROFAUNA which feed off particles within the sand as they move below the surface, and the interstitial fauna, which are small enough to move between particles. They are large enough to be seen by the naked eye. They are often abundant and, in some cases, attain exceptionally high densities. They are larger than 1mm (0.04 inch) such as sponges, crustaceans, anthozoans, polychaete worms

MEIOFAUNA has a size range between 0.1mm and 1mm in size, organisms like cocepods, ostracods, nematodes and gastrotrichs. They have hooks to grab the sand. The biological community of sandy shores varies according to the exposure to the tide and can range from a macrofauna-dominated community in sheltered sites to a microfauna or meiofauna dominated community in exposed sites.

MICROFAUNA, smaller than 0.1mm including diatoms, bacteria, ciliates, amoeba, and flagellates.

 

FAUNA is all of the animal life of any particular region or time. They are the benthos beneath the seafloor. The corresponding term for plants is flora fauna and other forms of life such as collectively referred to as BIOTA.

Zonation

DUNES – a hill of sand built by eaolian processes. Dunes occurred in different forms and sizes, formed by interaction with the wind. This is where you can see the Primary (active) and Secondary (fixed) Dunesand also, swale, the hollow between dunes, often close enough to the water table so that marsh plants or peatland plants can get established. Stagnant freshwater pools can develop

BACK BEACH OR BACKSHORE – rarely touched by wave action and ends at the edge of the first dune

FORESHORE or SURF ZONE – the sloping portion of the beach between high and low tide. It consists of berm which isnearly horizontal and is formed when the waves deposit sand. A storm berm can mark the highest limit of storm waves. Several berms can occur at spring and neap tide levels.

There are THREE BASIC TYPES OF BEACHES:

REFLECTIVE BEACH – this type occurs when conditions are calm and/or the sediment is coarse. There is no surf zone and waves flow upon the beach. It reflects a major part of the incoming wave.

INTERMEDIATE BEACH – this was formed when bigger waves cut back reflective beach and spread out its sediments to form a surf zone

 DISSIPATIVE BEACH – this was created when wave action is strong and/or sediment particle size is fine. This type has a flat and maximally eroded beach.

ECOLOGICAL FEATURES

STRESS AND SURVIVAL

The beach is not an easy place to live. Waves constantly pound the shore; wind desiccates plants and carries salt and sand inland; temperatures fluctuate during the course of a day; fresh water is not easy to come by; and the shifting sand leaves small organisms in constant danger of being crushed

ADAPTATIONS

MOBILITY – burrowing, vertical tidal migrations

RESPIRATION – facultative anaerobes, evaporative cooling

REPRODUCTION – iteroparous (frequent time); semelparous (once a year)

PROTECTION– burrowing; tidal migration; phenotypic plasticity (escaping movement)

 

 FACTORS CURRENTLY IMPACTING SANDY SHORES.

STORMS – they represent the greatest natural hazard faced by sandy-shore animals

DISRUPTION OF SAND TRANSPORT – This has resulted most obviously from the construction of harbours, breakwaters, jetties (piers) and groins, which deprive down-drift beaches of sand while updrift sand accumulates and advances seawards.

BEACH NOURISHMENT AND BULLDOZING - Beach nourishment by importing sand and bulldozing to restore dunes, by transferring sand from low to high levels, have become common practices in some parts of the world, such as North Carolina, USA, which face ongoing beach erosion from man-made structures or from natural causes (Leonard et al. 1990; Peterson et al. 2000).

POLLUTION – oil pollution; organic enrichment (that leads to a lowering of oxygen tensions within the sand and a consequent upward encroachment of anoxic ‘black layers’. This in turn results in impoverishment of the fauna); Factory effluents

MINING - removal of sand itself, mining may take place for precious stones, such as diamonds, or  for various minerals

TRAMPLING - direct damage to vegetation and the fauna,but also physical impact on the substratum, notably compaction, which influences soil moisture, run-off, erosion, vegetation and micro-organisms (Liddle & Moore 1974)

 

BEACH CLEANING – deprives the ecosystem of valuable nutritional input, semi-terrestrial forms such as talitrid amphipods, oniscid isopods and ocypodid crabs being the most deprived

GROUNDWATER CHANGES - intensified by the hardening of surfaces, so that surface water from rain is diverted to storm water drains instead of sinking into the soil

BAIT COLLECTING - populations are often drastically reduced by these activities, they are seldom if ever eliminated, as they reach a level at which the effort of collecting fails to justify the reward

Fishing. Recreation/tourism, Littering

 

 

 

 

 

 

 

MUDDY SHORES

 

The term “MUD” is loosely applied to deposits containing a high proportion of silt or clay particles. Muddy shores develop on places where clay and silt (particles finer than sand) are deposited by river currents or by tidal action.

 

result of the erosion and deposition of the surrounding coastal bedrock

 

Catastrophic events sometimes create situations that completely alter the properties of a mudflat for short periods of time

 

Muddy shores, with their finer sediment, have smaller interstitial spaces and these trap organic matter.Smaller spaces mean that drainage when the tide drops is less and so muddy shores hold on to their water

 

Mud, deposited in calm conditions, will be a flatter habitat (hence the term mudflat) and water is unlikely to drain. This minimal desiccation negates much in the way of zonation on the shore. However, the diversity of species is likely to be higher than sand. Smaller creatures will be commonplace

In places where the velocity of the water is low enough the fine particles will sink to the bottom where bottom organisms will fixate them

 

It provides source of organic material for organisms living within and on top of the mud, called the endo- and epibenthos.The benthic communities on muddy shores are often low in diversity and productivity, due to limited oxygen restricting chemical and biological degradation processes

 

While feeding on surface detritus, Baltic Macoma produces incredible amounts of faeces (droppings). The total daily production of Macoma droppings, in the Minas Basin, may be as much as 6 x 106 kg of dry sediment. What this provides is a surface around which bacterial colonies can grow and become a valuable food source

MANGROVE SWAMPS

 

CHARACTERISTICS

 

Specialized Root System

Woody plants that grow at the interface between land and sea in tropical and sub-tropical latitudes where they exist in conditions of high salinity, extreme tides, strong winds, high temperatures and muddy, anaerobic soils. There may be no other group of plants with such highly developed morphological and physiological adaptations to extreme conditions.

Morphological specializations include profuse lateral roots that anchor the trees in the loose sediments, exposed aerial roots for gas exchange and viviparous water-dispersed propagules

AERIAL ROOTS:

 

Breathing Roots (Pneumatophores) – Special vertical roots, called pneumatophores, form from lateral roots in the mud, often projecting above soil permitting some oxygen to reach the oxygen-starved submerged roots.

Stilt Roots- are the main organs for breathing especially during the high tide. They are very common in many species of Rhizophora and Avicennia. Aeration occurs also through lenticels in the bark of mangrove species.

 

Reproductive Strategies Of Mangroves

Virtually all mangroves share two common reproductive strategies:

Dispersal

Vivipary

Coping With Salt

Because of their environment, mangroves are necessarily tolerant of high salt levels and have mechanisms to take up water despite strong osmotic potentials. Some also take up salts, but excrete them through specialized glands in the leaves. Others transfer salts into senescent leaves or store them in the bark or the wood. Still others simply become increasingly conservative in their water use as water salinity increases.

DEFINITIONS

The term “mangrove” used to refer to a habitat comprised of a number of halophytic (salt-tolerant) plant species, of which there are more than 12 families and 50 species worldwide.

 

They are found in warmer areas between the latitudes of 32 degrees north and 38 degrees south, along the tropical and subtropical coasts of Africa, Australia, Asia and North and South America. In the U.S., mangroves are commonly found in Florida.

 

Mangrove plants have a tangle of roots which are often exposed above water, leading to the nickname “walking trees.” The roots of mangrove plants are adapted to filter salt water, and their leaves can excrete salt, allowing them to survive where other land plants cannot. Thus, mangrove is a non-taxonomic term used to describe a diverse group of plants that are all adapted to a wet, saline habitat.

 

The term “mangrove” often refers to both the plants and the forest community. To avoid confusion, Macnae (1968) proposed that “mangal” should refer to the forest community while “mangroves” should refer to the individual plant species. Duke (1992) defined a mangrove as, “…a tree, shrub, palm or ground fern, generally exceeding one half metre in height, and which normally grows above mean sea level in the intertidal zone of marine coastal environments, or estuarine margins.” This definition is acceptable except that ground ferns should probably be considered mangrove associates rather than true mangroves.

TAXONOMY

Mangroves are not a single genetic group but representing a large variety of plant families that are adapted to tropical intertidal environment. Tomlinson (1986) recognized three groups of mangroves:

Major mangrove species – the strict or true mangroves, recognized by most or all of the following features:

 They occur exclusively in mangal.

 They play a major role in the structure of the community and have the ability to form pure stands.

 They have morphological specializations – especially aerial roots and specialized mechanisms of gas exchange.

They have physiological mechanisms for salt exclusion and/or excretion.

They have viviparous reproduction.

 They are taxonomically isolated from terrestrial relatives. The strict mangroves are separated from their nearest relatives at least at the generic level, and often at the sub‐family or family level.

Minor mangrove species - less conspicuous elements of the vegetation and rarely form pure stands.

Mangrove associates

 

PHYSIOLOGY

Salt regulation

Mangroves are physiologically tolerant of high salt levels and have mechanisms to obtain fresh water despite the strong osmotic potential of the sediments (Ball, 1996). They avoid heavy salt loads through a combination of salt exclusion, salt excretion, and salt accumulation

Salt concentrations in the sap may also be reduced by transferring the salts into senescent leaves or by storing them in the bark or the wood (Tomlinson, 1986).

As water salinity increases, some species simply become increasingly conservative in their water use, thus achieving greater tolerance (Ball and Passioura, 1993)

In the wet season, the fine root biomass increases in response to decreased salinity of the surface waters, directly enhancing the uptake of low-salinity water (Lin and Sternberg,1994).

Most mangrove species directly regulate salts.

Because mangrove roots exclude salts when they extract water from soil, soil salts could become very concentrated, creating strong osmotic gradients (Passioura et al., 1992).

Transpiration rates vary with season, being higher in the dry season than in the wet season. This corresponds to changes in stomatal movement..This includes increases in vapor pressure deficit and osmotic potential of the substrata (Naidoo and Von-Willert, 1994).

Photosynthesis

Temperature-induced changes in the relative rates of photosynthesis and respiration, in turn, influence overall growth rates.

Strong sunlight can also reduce mangrove photosynthesis through inhibition of Photosystem II (Cheeseman et al., 1991). The photosynthetic rates of mangroves saturate at relatively low light levels despite their presence in high sunlight tropical environments. The fairly low photosynthetic efficiency may be related to the concentration of zeaxanthin pigments in the leaves (Lovelock and Clough, 1992). To prevent damage to the photosystems, the mangroves dissipate excess light energy via the xanthophylls cycle (Gilmore and Bjorkman, 1994) and through the conversion of O2 to phenolics and peroxidases (Cheeseman et al., 1997).

 

REPRODUCTION

Reproduction, dispersal and establishment Bhosale and Mulik (1991) described four methods of mangrove reproduction: Viviparity, Cryptoviviparity, normal germination on soil, and vegetative propagation.

 

Dispersal by means of water and;

Vivipary – means that the embryo develops continuously while attached to the parent tree. They may grow in place, attached to the parent tree for one to three years, reaching length up to one meter, before breaking off from the parent plant & falling into the water, these seedling then lodged in the mud where they quickly produce additional roots and begin to grow

 

SUMMARIZATION

Rhizophora mangle
red mangrove

Avicennia germinans
black mangrove

Laguncularia recemosa
white mangrove

Flowering Season

all year, but maximum in late spring and summer

spring and early summer

spring and early summer

Shape of Propagule

cigar, alrge green bean

oblong/elliptical, lima bean

flattened, pea green when fall, sunflower seed

Length of Propagule

15 cm

2 - 3 cm

less than .5 cm

Degree of Vivipary

extensive while on tree

intermediate?

“semi-viviparious”
germination during dispersal

Obligate Dispersal

40 days

14 days

8 days

Root Establishment

15 days (either vertical or horizontal)

7 days

5 days

Viable Longevity

365 days

110 days

35 days

Seedling Mortality

lowest

intermediate

highest

Sucession

due to emgbryonic reserves, can establish under canopy and wait for tree to fall

need adequate light; need strand period of 5 days above tide

need adequate light; need strand period of 5 days above tide to hold soil

 

 

 

               

 

 

 

ADAPTATION

Red Mangroves(Rhizophora mangle)

Closest to the water - in fact in the water at high tide

 

The roots of the red mangrove are distinctive, with long arching aerial prop roots that help anchor the plant in the sediment. These roots are firmly mired in the organic muck; decomposition in this muck (manure) releases nutrients that the tree can use, but there is no oxygen.  The roots of the red mangrove are able to obtain water from the ocean by pumping magnesium ions into the root.  These positive ions force other positive ions, such as sodium, out of the root.  The high concentration of magnesium in the root creates a high osmotic potential, and this in turn attracts water in from the surrounding seawater. The net effect is to set up “reverse osmosis” or to exclude salt from the root.  Oxygen to support the cells moving all those magnesium ions is provided through air channels in the roots. 

Red mangroves are distinguished by the dendritic network of aerial prop roots extending from the trunk and lower branches to the soil. The prop roots are important adaptations to living in anaerobic substrates and providing gas exchange, anchoring system, and absorbing ability. Within the soils, microroots stabilize fine silts and sands maintaining water clarity and quality.

 

Life Cycle of the Red Mangrove: Flowers of the red mangrove (above, right) are fertilized and begin to develop.  The propagule or seedling, does not drop from the tree immediately, but continues to grow in place, reaching about 6" in length (15cm).  When it does drop off, the propagule (also known as a pencil) can float.  It is heavier at the root end, and eventually the lower end makes contact with soil and begins to grow (below).  If there are no storms or other disturbances, the red mangrove seedling and its companions can advance the shoreline as they stabilize the soils beneath them.  In nature however, storms tend to keep the system in balance.  Human cutting of mangroves can cause severe erosion problems during major storms or tsumani, as we learned in 2004 and 2005 with the Indonesian Tsumani and Huricane Katrina.  See also:

http://www.earthisland.org/map/katrina.html

 

 

 

 Black Mangroves (Avicennia germinans)

Next inland, usually above the high tides

These trees deal with salt by excreting it onto the leaves; also, like the red mangroves, the roots of the black mangrove are metabolically very active.  To supply the roots with oxygen in the oxygen-poor sediments the black mangrove has an extensive development of pneumatophores (species have root extensions that take in oxygen for the roots).  These structures grow up out of the soil and their spongy construction helps convey oxygen down to the roots.  Unlike the red mangrove which actively excludes ocean salts from entering at the root, the black mangrove allows the salt to enter but excretes it on the surface of the roots and the leaves.  You can often find salt crystals on the leaves of the black mangrove.  It can survive the higher salinities then the red mangrove; such higher salinities might be expected further up on the beach where the black mangroves are found.

 

White Mangroves (Laguncularia racemosa)

Neither aerial prop roots or pneumatophores are usually visible (but either may be present if conditions warrant; the pneumatophores take the form of peg roots).   Like the black mangrove, the white mangrove excretes salts on the leaf surface.

You may have noticed that the scientific names for the mangroves differ greatly (Rhizophora mangle, Avicennia germinans, Laguncularia racemosa).  This is because the word “mangrove” indicates an ecological rather than a taxonomical grouping.   For instance, when we speak of oaks or maples we are referring to trees of the genera Quercus and Acer, respectively.  However, when we speak of mangroves we are speaking of tropical, salt-tolerant trees that grow along the shore.  Hence, the 3 species of mangrove mentioned all hail from different genera and are not closely related to each other.

Another interesting tidbit is the way the trees segregate themselves in the habitat.  Red mangrove seeds are much larger than either of the other two and simply aren’t carried very far inland.  Black mangrove seeds are smaller and will be washed further up the beach by the tides.  White mangrove seeds are the smallest and are carried the furthest inland.  Thus, each tree species has a seed that is adapted to be carried to the appropriate habitat for the tree to grow.

 

Buttonwood

Buttonwoods grow to 12 to14 m (39 to 46 ft) in height in a shrub or tree form,but do not produce a true propagule in Florida (Tomlinson 1986). Bark is greyand very furrowed providing attachment for epiphytes. Leaves are thin, broadto-narrow, and pointed. There are two morphotypes: the green with mediumgreen leaves found on peninsular Florida and the silver with pale pastel greenPage 3-524MANGROVES Multi-Species Recovery Plan for South Floridaleaves historically limited to the Florida Keys but now widespread by nurserypractices. It is thought the silver buttonwood is an adaptation to the rocky, dryhabitats associated with the Keys archipelago. Two glands are found at theapex of the petiole that excrete extra floral nectar and salt. Tiny brownishflowers are found in a sphere on the terminal ends of branches. These producea seed cluster known as the button. Buttonwoods are able to grow in areasseldom inundated by tidal waters. The mangrove adaptations to the osmoticdesert of salt water, also adapted buttonwoods to arid areas of barrier islandsand coastal strands.

Before the storm… 🌧🌧🌧
#bigwaves at #windansea #blueandgreen #blue #green #moodygrams #cloudyday #cloudysky #blueforyou #instamood #iphonography #iphoneonly #rockyshore #instagood #instapic #instanature #outdoors #travelgram #waves #whitecaps (at Little Point La Jolla)