MANGROVE ECOLOGY WORKSHOP MANUAL Edited by IIka C. Feller Marsha Sitnik Cover illustration provided by Molly Kelly Ryan, Dept. of Invertebrate Zoology, National Museum of Natural History, Smithsonian Institution, Washington, DC 20560 MANGROVE ECOLOGY: A Manual for a Field Course A Field Manual Focused on the Biocomplexity on Mangrove Ecosystems Edited by ILKA C. FELLER Smithsonian Environmental Research Center, Smithsonian Institution MARSHA SITNIK Department of Systematic Biology, Smithsonian Institution Addresses of the editor and contributors of this report Richard Blanquet Noel D. Jacobs Department of Biology MBRS - Project Coordinating Unit Georgetown University Coastal Resources Multicomplex Building Washington. DC 20057 Princess Margaret Drive E-mail: [email protected] P. O. Box 93 Belize City, Belize Aaron M Ellison E-mail: [email protected] Clapp Laboratory Mt. Holyoke College Karen L. McKee South Hadley, MA 01075 National Wetlands Research Center, USGS E-mail: [email protected] 700 Cajundome Blvd. Lafayette, LA 70506 Ilka C. Feller Phone: 337 266-8662 Smithsonian Environmental Research Center Fax: 337-266-8592 647 Contees Wharf Rd. E-mail: [email protected] PO Box 28 Edgewater MD 21037 Marsha Sitnik E-mail: [email protected] Department of Systematic Biology National Museum of Natural History Janet Gibson Smithsonian Institution Coastal Zone Management Program Washington, DC 20560 Department of Fisheries E-mail: [email protected] Belize City, Belize E-mail: [email protected] Thomas J. Smith III USGS/BRD Walter I. Hatch Ctr. for Coastal Geol. & Regional Marine Department of Biology Studies St. Mary_s College of Maryland 600 Fourth St., South St. Mary_s City, MD 20686 St. Petersburg, FL 33701 E-mail: [email protected] E-mail: [email protected] Will Heyman Christopher E. Tanner Marine Projects Coordinator Department of Biology The Nature Conservancy St. Maryʼs College of Maryland 4245 N. Fairfax, Suite 100 St. Maryʼs City, MD 20686 Arlington VA 22203 E-mail: [email protected] E-mail: [email protected] This manual was prepared especially for the Mangrove Education and Training Program for Belize. © Smithsonian Institution 1996 Washington. DC ii TABLE OF CONTENTS Editors’ preface .........................................................................................................................................iv Acknowledgements....................................................................................................................................v Part I: Lectures A. Mangrove Ecosystems: Definitions, Distribution, Zonation, Forest Structure, Trophic Structure, and Ecological Significance Karen L. McKee ............................................................... 1 B. Mangrove Forest Structure Thomas J. Smith III............................................................................................ 7 C. Biodiversity in the Mangrove Supratidal Zone Ilka C. Feller..................................................................... 15 D. Biodiversity in the Mangrove Intertidal and Subtidal: Algal and Seagrass Communities Christopher E. Tanner, Ilka C. Feller, and Aaron M. Elison........................................................................ 23 E. Zooplankton of Coastal Lagoons with Emphasis on the Mangrove Environment Noel J. Jacobs ........... 29 F. Biological Adaptations to Environmental Extremes in Mangrove Flora Karen L. McKee ...................... 35 G. Adaptations to Environmental Change in Marine Fauna Richard Blanquet and Walter I. Hatch............. 39 H. Role of Mangrove Environment in the Life History of Marine Fishes Will Heyman ............................... 43 Part II: Field Activities Mangrove and Mangrove Associates................................................................................................................... 57 Mangrove Forest Structure ................................................................................................................................... 65 Mangrove Arboreal Communities........................................................................................................................ 79 Mangrove Intertidal and Subtidal Habitats - Algal and Seagrass Communities................................................ 87 The Zooplankton Community at Calabash Caye, Belize.................................................................................... 99 Environmental Extremes and Adaptive Strategies in Mangroves .................................................................... 103 Water Quality and Response of the Mangrove Jellyfish Cassiopea to Varying Salinity ................................. 107 Diversity of Macrofauna in Mangrove, Seagrass, and Coral-Reef Communities............................................111 Larvae Transport from Fish Spawning Aggregation Sites................................................................................ 115 The Value of Mangrove Swamps as Nurseries.................................................................................................. 119 Hurricane Hattie Damage at Soldier Cay........................................................................................................... 123 Glossary...................................................................................................................................................121 Selected References................................................................................................................................129 iii Editors’ preface Intertidal mangrove swamp communities dominate the world’s tropical and subtropical coasts, paralleling the geographical distribution of coral reefs. They survive in substrate salinities ranging from fresh water alongside rivers to hypersaline ponds and mudflats. Mangrove plants are pioneer as well as mature-phase species. They not only help form these environments, they create habitats for a diverse and characteristic community, including numerous mangrove-dependent organisms. The term “mangrove” refers to an ecological rather than a taxonomic assemblage of plants. Worldwide, 34 species or so in nine genera in five families are considered “true mangroves” and another 80 or so species occur as “minor components” and “mangrove associates.” True mangroves are ecologically restricted to tidal swamps and form extensive monospecific stands. They are morphologically adapted with aerial roots and vivipary. As halophytes, they are physiologically adapted for either salt exclusion or excretion. Taxonomically, true mangroves are isolated from their nearest terrestrial relatives, at least at the generic level. Mangroves are critical, not only for sustaining biodiversity in these intertidal swamps, but also for their direct and indirect benefit to human activities. Energy and nutrients are assimilated and stored in leaves of mangrove trees. As a detritus-based ecosystem, leaf litter from these trees provides the basis for adjacent aquatic and terrestrial food webs. Because most energy and nutrients are biotically stored rather than free in the water or substrate, species diversity of these swamps is directly dependent on primary productivity by mangrove plants. Mangrove swamps function as nurseries for most of the sport and commercial fishes found in deeper waters. Mangrove swamps also provide feeding grounds for large reef fishes. As a result, mangrove-assimilated energy and nutrients are exported to surrounding coral reefs. Besides supporting and renewing coastal fishing stock, mangrove swamps also benefit human economic development by stabilizing shorelines. This is a critical function in tropical coastal areas that are periodically battered by tropical storms and hurricanes. Bangladesh offers examples of the devastation that can happen when deltaic and island mangrove swamps are deforested. “Land” in mangrove swamps is peat, produced primarily by red-mangrove rootlets. This organic substrate is not soil and cannot sustain human activities such as agriculture, buildings, or dredging. Undisturbed, mangrove swamps can buffer the effects of storms and protect property and human life behind these coastal fringes. Mangrove forests are generally oligotrophic ecosystems. Human-caused enrichment is one of the major global threats to these and other coastal environments. Our experiments show that nutrients are not uniformly distributed among or even within mangrove forests and that soil fertility can switch from conditions of nitrogen to phosphorus limitation across narrow gradients. Likewise, not all ecological processes respond similarly to the same nutrient. Enrichment affects plant growth, metabolism, and tissue quality, which in turn affect primary consumption. It alters litter quality, thereby linking nutrient enrichment to detritivory, decomposition, and below-ground processes. Interactions and feedback among nutrient availability, microbial communities, nutrient cycling, and higher trophic levels have not been explored in mangrove forests. Enrichment with nitrogen and phosphorus may affect microbial communities and activity, nutrient dynamics, photosynthesis, and ultimately, peat accumulation and habitat stability. Furthermore, hydrology and sediment physico-chemical parameters may also influence these interactions and feedbacks. Despite their ecological and economic significance, mangrove swamps are an imperiled ecosystem. Throughout the tropics, they are threatened directly and indirectly by commercial development. Tropical iv and subtropical