Preface Acknowledgements Part I. General Account: 1. Ecology 2. Floristics 3. Biogeography 4. Shoot systems 5. Root systems 6. Water relations and salt balance 7. Flowering 8. Seedlings and seeds 9. Utilization and exploitation Part II. Detailed Descriptions by Family References Index.

The botany of mangroves

Mangroves are 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.

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 Morphological specializations include profuse lateral roots that anchor the trees in the loose sediments, exposed aerial roots for gas exchange and viviparous waterdispersed propagules.

Mangroves create unique ecological environments that host rich assemblages of species. The muddy or sandy sediments of the mangal are home to a variety of epibenthic, infaunal, and meiofaunal invertebrates Channels within the mangal support communities of phytoplankton, zooplankton and fish. The mangal may play a special role as nursery habitat for juveniles of fish whose adults occupy other habitats (e.g. coral reefs and seagrass beds).

Because they are surrounded by loose sediments, the submerged mangroves' roots, trunks and branches are islands of habitat that may attract rich epifaunal communities including bacteria, fungi, macroalgae and invertebrates. The aerial roots, trunks, leaves and branches host other groups of organisms. A number of crab species live among the roots, on the trunks or even forage in the canopy. Insects, reptiles, amphibians, birds and mammals thrive in the habitat and contribute to its unique character.

Living at the interface between land and sea, mangroves are well adapted to deal with natural stressors (e.g. temperature, salinity, anoxia, UV). However, because they live close to their tolerance limits, they may be particularly sensitive to disturbances like those created by human activities. Because of their proximity to population centers, mangals have historically been favored sites for sewage disposal. Industrial effluents have contributed to heavy metal contamination in the sediments. Oil from spills and from petroleum production has flowed into many mangals. These insults have had significant negative effects on the mangroves.

Habitat destruction through human encroachment has been the primary cause of mangrove loss. Diversion of freshwater for irrigation and land reclamation has destroyed extensive mangrove forests. In the past several decades, numerous tracts of mangrove have been converted for aquaculture, fundamentally altering the nature of the habitat. Measurements reveal alarming levels of mangrove destruction. Some estimates put global loss rates at one million ha y−1, with mangroves in some regions in danger of complete collapse. Heavy historical exploitation of mangroves has left many remaining habitats severely damaged.

These impacts are likely to continue, and worsen, as human populations expand further into the mangals. In regions where mangrove removal has produced significant environmental problems, efforts are underway to launch mangrove agroforestry and agriculture projects. Mangrove systems require intensive care to save threatened areas. So far, conservation and management efforts lag behind the destruction; there is still much to learn about proper management and sustainable harvesting of mangrove forests.

Mangroves have enormous ecological value. They protect and stabilize coastlines, enrich coastal waters, yield commercial forest products and support coastal fisheries. Mangrove forests are among the world's most productive ecosystems, producing organic carbon well in excess of the ecosystem requirements and contributing significantly to the global carbon cycle. Extracts from mangroves and mangrove-dependent species have proven activity against human, animal and plant pathogens. Mangroves may be further developed as sources of high-value commercial products and fishery resources and as sites for a burgeoning ecotourism industry. Their unique features also make them ideal sites for experimental studies of biodiversity and ecosystem function. Where degraded areas are being revegetated, continued monitoring and thorough assessment must be done to help understand the recovery process. This knowledge will help develop strategies to promote better rehabilitation of degraded mangrove habitats the world over and ensure that these unique ecosystems survive and flourish.

pdf/biology-of-mangroves-and-mangrove-ecosystems-u4nj7vn8om.pdf

Biology of mangroves and mangrove Ecosystems

The Botany of Mangroves

The fossil record for angiosperm pollen types which are comparable to recent taxa is evaluated, following a similar survey published in 1970. Special attention is paid to the dating of the sediments. Evidence for 139 families is considered to be reliable, for others the records are cited as provisional, pending the accumulation of more evidence. Some published records are shown to be erroneous.

Fossil pollen records of extant angiosperms.

Mangroves are species of halophytic intertidal trees and shrubs derived from tropical genera and are likely delimited in latitudinal range by varying sensitivity to cold. There is now sufficient evidence that mangrove species have proliferated at or near their poleward limits on at least five continents over the past half century, at the expense of salt marsh. Avicennia is the most cold-tolerant genus worldwide, and is the subject of most of the observed changes. Avicennia germinans has extended in range along the USA Atlantic coast and expanded into salt marsh as a consequence of lower frost frequency and intensity in the southern USA. The genus has also expanded into salt marsh at its southern limit in Peru, and on the Pacific coast of Mexico. Mangroves of several species have expanded in extent and replaced salt marsh where protected within mangrove reserves in Guangdong Province, China. In south-eastern Australia, the expansion of Avicennia marina into salt marshes is now well documented, and Rhizophora stylosa has extended its range southward, while showing strong population growth within estuaries along its southern limits in northern New South Wales. Avicennia marina has extended its range southwards in South Africa. The changes are consistent with the poleward extension of temperature thresholds coincident with sea-level rise, although the specific mechanism of range extension might be complicated by limitations on dispersal or other factors. The shift from salt marsh to mangrove dominance on subtropical and temperate shorelines has important implications for ecological structure, function, and global change adaptation.

/pdf/mangrove-expansion-and-salt-marsh-decline-at-mangrove-4uoy2pl8g8.pdf

Mangrove expansion and salt marsh decline at mangrove poleward limits

The mangrove community of the Neotropics shows a progressive increase in diversity through the Cenozoic. Palynofloras from the early Eocene -50 Ma (million years ago) indicate that brackish-water coastal areas were occupied by four principal genera-Acrostichum, the extinct Brevitricolpites variabilis, Nypa, and Pelliceria (Pellicera). Avicennia is first reported in the late Miocene - 10 Ma. Extinctions, introductions, and adaptations varied the composition and increased net diversity to six mangrove and three associated genera by the middle Pliocene (-3.5 Ma)-Acrostichum, Avicennia, Crenea, Laguncularia, Pelliceria, Rhizophora; Acacia, Hampea/Hibiscus, and Pachira. Modernization continued in the Quaternary with the first microfossils of Conocarpus, and with the addition of eight possible associates, for a total of 15 genera. Twelve others, unknown as fossils, were added during the Cenozoic to constitute the presentday community of -27 genera of mangroves and associates. The fossil record identifies a trend of increasing diversity that can be assessed as new assemblages are studied, and provides a first quantitative estimate of Neotropical history through the Cenozoic Era.

http://www.redciencia.cu/geobiblio/paper/1995_Graham.pdf

Diversification of Gulf/Caribbean Mangrove Communities through Cenozoic Time1

New discoveries of fossil pollen of Pelliceria in Tertiary deposits of the Caribbean extend both the stratigraphic and geographic range of the genus in the Antilles and Central America. The new records include specimens from the Eocene of Jamaica, Eocene of Panama, and Oligo-Miocene of Panama. Factors suggested for explaining the range restriction of Pelliceria, from once widespread throughout the Caribbean, to presently from Pacific Costa Rica to northwestern Colombia, include sea-level fluctuations, climatic trends toward cooler conditions, and competition from extensive communities of Rhizophora which first developed in the Caribbean region during the Oligocene. THE GENUS Pelliceria' is a monotypic member of the Theaceae (Pelliceriaceae fide Airy Shaw 1966) presently restricted to lowland coastal areas from Puntarenas in Costa Rica, through Panama and northwestern Colombia, to the Esmeraldas Province of Ecuador (Holdridge, pers. comm. 1976). The single species, P. rhizophorae Planchon and Triana (the 'palo de sal' in Panama), is a mangrove but lacks the characteristic prop-roots (cf. Kobuski, 1951: 258). It frequently occupies sites where rivers empty into the Pacific (Genuty, pers. comm. 1976), or slightly brackish water zones behind the mesoto euryhaline strand of Rhizophora-Laguncularia-Avicennia. In the mangrove region of the Osa Peninsula of Costa Rica, however, it is associated with Rhizophora in areas of highest salinity. At Main Beach and Playa Grande, Panama, "It develops best along the main drainage channels of the swamp in constantly wet soils that are very shallowly inundated at high tide, usually in company with Rhizophora and Laguncularia" (Johnston 1949: 207). Pelliceria is a small tree, usually between 5-10 m in height but occasionally reaching 20 m. In the Golfo Duke region it has . . . "a very straight, unbranched trunk and narrow crown. The trees have a very strongly developed, deeply fluted pyramidal buttress at the base, even in young specimens, and are unique in this character in the mangrove association" (Allen 1956: 287). Kobuski (1951) and Cuatrecasas (1958) provide further taxonomic and ecological information on the genus. In 1964 van der Hammen and Wijmstra described a fossil pollen type, Psilatricolporites crassus, from the Tertiary of the Guiana Basin. Subsequently Langenheim et al (1967) reported "Pelliciera-type pollen" from the Oligo-Miocene Simojovel Group of Chiapas, Mexico (plate XLII: 315). Wijmstra (1968) recognized the Chiapas specimens as similar to Psilatricolporites, and the biological affinities of the latter were established. Later pollen of Pelliceria was also described from the Oligocene of Puerto Rico (Graham and Jarzen 1969, figs 66-68). Germeraad et al. ( 1968) summarize its stratigraphic range in the Caribbean as basal Eocene to Recent. Thus with the recognition of fossil pollen of P. ctasus as belonging to Pelliceria, the latter, presently restricted to Pacific Central and northern South America, is revealed as a once widely distributed mangrove extending from northern South America to south-central Mexico and the Antilles (fig. 1). Recently, new occurrences of Pelliceria have been discovered in the Caribbean Tertiary establishing the genus as even more abundant and widespread. The pollen of Pelliceria is variable both in size and ornamentation. Some specimens have conspicuous mound-like scabrae with a fine sub-reticulum evident at lower focal levels (fig. 2A insert, fig. 2B). In others the scabrae are less conspicuous, and the grains are distinctly reticulate (e.g., figs. 2G, H). Size ranges from ca. 40,u to 90u in modern pollen, with moderate percentages of smaller abortative grains present in some preparations. Germeraad et al. (1968) noted these variations and suggested they may represent various states of preservation (viz., erosion of the scabrae). However, comparable range in size and ornamentation is also evident on modern reference slides prepared from a single flower. The pollen of Pelliceria is distinct, and similar ranges in size and ornamentation are present in both modern pollen and fossil specimens from the Caribbean.

New records of pelliceria new record theaceae pelliceriaceae in the tertiary of the caribbean

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Diversification of Gulf/Caribbean Mangrove Communities through Cenozoic Time1

New records of pelliceria new record theaceae pelliceriaceae in the tertiary of the caribbean