Quality, location and quantity of water are essential to primary production. Epiphytes attached to the roots can add significantly to this production. Estuarine mangrove systems are second only to the tropics in primaryproductivity. Estimates of 8.8 dry tons/hectare/year of organic material have been recorded. Factors affecting productivity are species composition, age, competition, substrate, wave action, bird activity, hurricanes, etc.

Three methods that produce estimates of primary productivity are biomass, gas exchange, litter fall. Table 2 compares above and below ground biomass estimates in a Puerto Rican and a South Florida red mangrove forest. It seems that if all root material is taken into account, below ground biomass may exceed above ground estimates. However, all biomass estimates are probably highly variable from forest to forest. Another method of estimating production is net amount of carbon. In general, Red mangroves have the greatest net production, Blacks intermediate, and Whites the lowest figures of net primary production.

Red mangroves intercept 95% of the available light at 13 feet (4 m) below top of the canopy. Therefore, it is not suprising that 90% of the leaf biomass exists in this upper portion of the canopy. Possible explanations are shading and environmental stress (salt, anaerobic conditions, etc). Litter fall of Florida mangrove forests estimates range from 2-3 dry g/m2/day in well developed stands. Leaves fall all year with a minor peak in early summers. Additionally, sporadic litter fall exists after stress.

Few animals graze directly on mangroves. The mangrove periwinkle (Littorina angulifera) and the coffee bean snail (Melampus coffeus) are known to eat Black mangrove propagules. Primary consumers are the decomposers. Bacteria and protozoans colonize plant litter and begin breaking it down chemically into organic compounds, minerals, CO2, and nitrogenous wastes. Amphipods and other small grazers speed up the process by reducing the litter mechanically to detritus. This increase in surface area aids microbial colonization which speeds up decomposition. Due to the increased activitiy of shredding organisms (crabs, amphipods, etc.), decomposition of Red mangrove leaves is faster in marine waters than freshwater or dry conditions. Faster decomposition is also apparent with an increase in tidal fluctuation.

Detritus, enriched nutritionally by its microbial population is utilized as a food source by a variety of organisms. The role of mangrove detritus and its importance to nearby reef systems is problematic. Surface waters associated with mangrove habitats are often characterized by a wide range of salinity (0-->40ppt), low macronutrient concentrations (especially Phosphorus), a relative low dissolved 02 concentration, frequently increased color and turbidity.These conditions are most pronounced in the Everglades with decreased pronounced effects in the Keys.

There is a hypothesis that mangroves may pulse the detritus food webs in nearby coastal waters. However, there is not enough data to prove this theory. Due to an increased epibiontic population there is a tendency for mangrove ecosystems to act as consumers of 02 and a sink for nutrients such as nitrogen and phosphorus.

Mangrove biomass is not totally reduced through decomposition. Litter that persists in absence of physical forces flushing the habitat may form peat. Red mangrove root material produces the most easily recognized peat reaching depths of several meters. The acidic nature of peat is capable of dissolving limestone underneath. Acidity is due to the release of organic acids during anaerobic decomposition. Reduced sulfur compounds are oxidized when drained and dried in the sun. These conditions are responsible for the characteristic smell of mangrove communities.

There exists a classic mangrove zonation model with red mangroves dominating from their maximum depth of water for growing 1.5 feet (.4 m) into the intertidal zone. Black mangroves take over the intertidal zone and predominate area covered by high tides. White mangroves appear in this area, but predominate along with Buttonwoods above the high tide line. However, there is much variation of this model from forest to forest. Recent general conclusions suggest that all species can grow together on a new site.

mangrove periwinkle

leaf litter

leaf breaking down

shredded leaf