Mangrove Ecology with a case study from Ecuador Introduction to Coastal Management

Mangrove or “Mangal” DefinitionDefinition –Tropical hardwood trees adapted to grow in marine intertidal environments Develop only on shorelines protected from wave action (estuaries, bays, lagoons) Common throughout the tropical regions of the world Typically flooded once or twice per day Red Mangroves (Rhizophora mangle)

Distribution of Mangroves Generally occur between 30 degrees N.L. and 30 degrees S.L.Generally occur between 30 degrees N.L. and 30 degrees S.L. Generally follow the 24 degree C. (75 degrees F.) isotherm of sea surface temperatureGenerally follow the 24 degree C. (75 degrees F.) isotherm of sea surface temperature Tolerate little or no frostTolerate little or no frost Uncommon along arid coastsUncommon along arid coasts Distribution of mangroves (green) in southern North American and Northern South America

Mangrove or “Mangal” Characteristics Low diversity of plant and animal speciesLow diversity of plant and animal species Canopy high and monotonousCanopy high and monotonous Soils waterlogged and anaerobicSoils waterlogged and anaerobic Substrate variable (muds, sand, rock, organic)Substrate variable (muds, sand, rock, organic)

Mangrove or “Mangal” Characteristics Mangrove species show characteristics of pioneer species in their reproductive biologyMangrove species show characteristics of pioneer species in their reproductive biology –r-selection properties in finding a habitat Mangrove species show characteristics of mature phase species in aspects of community structure and vegetative growthMangrove species show characteristics of mature phase species in aspects of community structure and vegetative growth –K-selection properties in maintaining habitat

Mangrove Specializations Most species have some part of root system exposed to atmosphereMost species have some part of root system exposed to atmosphere Leaves large, thick, leathery and evergreenLeaves large, thick, leathery and evergreen Many are capable of excreting salts from leavesMany are capable of excreting salts from leaves Most cannot be propagated vegetativelyMost cannot be propagated vegetatively Most have no growth ringsMost have no growth rings All mangroves distributed by water and propagules floatAll mangroves distributed by water and propagules float

Mangrove Characteristics FaunaFauna –highly variable; not characteristic –insects common –birds--few –mud skippers, crabs, oysters, snails –crocodiles, snakes (few poisonous) –tiger (Ganges River mangal is refuge) –deer, raccoon, bats (bats are visitors) Frigate Bird (Fregata magnificens) Raccoon (Procyon lotor) White-tailed Deer (Odocoilus ____)

Mangrove Characteristics Once the mangrove becomes established:Once the mangrove becomes established: –little structure to the community –succession not documented –no understory –no stratification –species distributed by edaphic factors (soil type, soil salinity)

Utilization and Exploitation of Mangroves ForestryForestry –boat building an fish traps –poles –firewood (charcoal) –tannins and dyes –chip and sell as cellulose base

Utilization and Exploitation of Mangroves AgricultureAgriculture –typical agricultural plants cannot survive in mangrove environments –rice fields –mariculture (shrimp, finfish, shellfish)

Utilization and Exploitation of Mangroves FisheriesFisheries –documented as nutrient source for nearshore fisheries –stabilize shorelines; reduce sedimentation into estuaries –habitat for juvenile fish –habitat for oysters and shellfish

Utilization and Exploitation of Mangroves Salt conversionSalt conversion Sewage treatment (garbage dump)Sewage treatment (garbage dump) Coastal protection (storm buffer, stabilize shoreline)Coastal protection (storm buffer, stabilize shoreline) Wildlife management (deer, crocodiles, tigers)Wildlife management (deer, crocodiles, tigers)

Ecuadorian Shrimp Mariculture Shrimp farming developed in the late 1960sShrimp farming developed in the late 1960s By 1982, 44% of fish exports were shrimpBy 1982, 44% of fish exports were shrimp Ecuadorian children seining for gravid female shrimp Ecuadorian shrimp farms created by removing mangrove forests along estuarine shoreline Ecuadorian worker seining for shrimp in man-made ponds

Shrimp Exports to the United States from Ecuador, Panama and Mexico ( )

Tradeoffs for Intensive versus Extensive Mariculture

Solutions? Intensify mariculture to increase yieldsIntensify mariculture to increase yields Discourage location of ponds in mangrovesDiscourage location of ponds in mangroves Train extension agentsTrain extension agents Link research and field applicationsLink research and field applications Discourage international funding for new sitesDiscourage international funding for new sites Charge single agency with mariculture managementCharge single agency with mariculture management