# Mapping the Mangroves - MWL

## Introduction

Tropical ecosystems are typically nutrient poor. Heavy rainfall in terrestrial environments washes and leaches nutrients from the soil, and  consistent sunlight and year round climatic growth conditions for plants create high levels of competition for available nutrients. Most nutrients become locked up for years at a time in the living tissue of the organisms that collected them. The mangrove estuary is a bit of an anomaly in the tropics. Due to their geographic position, water flows into the estuary carrying eroded sediments and nutrients from the surrounding land scape where they form rich layers of sedimentary mud. These muds tend to be anaerobic due to the action of decomposing bacteria and the impermeability of the mud to oxygen. The anaerobic conditions are a barrier which most organisms can not overcome to access the sediments and nutrients in the muds. In addition to our anaerobic conditions, the estuary waters are either salt, or a combination of salt/fresh water (sweet water). This water scenario, along with the anaerobic conditions presents a unique set of circumstances for organisms to overcome before the estuary can riches can be accessed. The mangrove is one organism that has adapted to the saltwater and anaerobic conditions of the estuary, in doing so, it has become a keystone species that defines the ecosystem and serves as a hinge point for energy flow within the system.  The photosynthetic activity of the mangroves converts solar energy into chemical energy. This process allows for mangrove growth in which nutrients from the sediments are being assimilated. Mangroves leaves are periodically dropped, it is these leaves that serve as a major energy source for the rest of the pyramid. Colonies of bacteria decompose the leaf matter releasing energy that is picked up by plankton and other primary level consumers. These processes form the base of food pyramid. The shape of the pyramid tapers due to less energy being available as we work our way up the pyramid. Energy is lost to the pyramid due to organisms metabolism, death, etc.….approximately 90% of  is lost from one trophic level to the next. These processes define the types of organisms in a community and have major effects on population numbers of the organisms. Ultimately recognition of this ecosystems significance as a nutrient sink and nursery area are of primary importance.

## Objectives

• Students will explore energy flow in an ecosystem.
• Students will create diagrams to show the relationship of organisms in an ecosystem.

## Teaching Summary

Concept mapping is a great way to explore the connections between organisms.  There are an infinite variety of ways to present this material. Below is a word bank that students use to place the terms into correct positions on the pyramid. Having students justify term placement can increase level of difficulty in the activity. A trip to an estuary to see some of the fundamental organisms would be helpful, but internet searches can be substituted.

Word Bank:  producers, consumers, photosynthesis, consumer, solar energy, chemical energy, nutrients, nitrates, phosphates, primary, secondary, tertiary, decomposer, recycling, red mangrove, phytoplankton, zooplankton, sponge, pelican, diatom and dinoflagellates, fish, shark, kingfisher, bacteria.

Vocabulary: Photosynthesis, Consumers, Producers, Decomposers, Trophic Levels, Anaerobic, Aerobic

## Resources

Google searches for organisms and trophic strategies for mangrove estuaries.

## Assessment Questions

Questions:

1. Why are the producers found at the base of the pyramid?
2. If we started with 1000 units of energy at the base level of the pyramid, how much energy will be found at the top consumer level?
3. How does the term recycling fit into this activity?