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Fish, forests, and phosphorus: How do tropical fish, rainforest canopies, and volcanic groundwater inputs affect stream phosphorus cycling?

Author(s): Carissa Ganong1, Gaston Small2

1. Missouri Western State University 2. University of St. Thomas

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Summary:
Rainforest stream nutrient concentrations vary with groundwater source, and different stream fish species feed on aquatic and/or terrestrial prey. Explore how phosphorus cycling changes with stream characteristics and relates to tropical…

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Rainforest stream nutrient concentrations vary with groundwater source, and different stream fish species feed on aquatic and/or terrestrial prey. Explore how phosphorus cycling changes with stream characteristics and relates to tropical conservation.
Contents:

Description

Overview of Module:

This activity introduces students to the role that animals play in ecosystem-scale nutrient cycling via analysis of data collected on fish excretion in streams at La Selva Biological Station, Costa Rica. Students are introduced to three key variables that predict phosphorus (P) excretion rates: fish body P content (bonier fish require more dietary P as they grow); fish diet (insectivorous fish species ingest more P in their diet compared to species that feed primarily on algae); and stream dissolved P concentrations (in higher-P streams, the algae and aquatic insects are enriched in P). Additionally, some fish specialize in feeding on terrestrial insects, meaning that their dietary P content is high regardless of which stream they live in.

This module involves reading about the study and interpreting data and includes eight questions – some directly from the reading, some more open-ended – that could be used as an assignment. The module provides a fun, interactive way for students to explore a real-life example of nutrient cycling and its potential impacts on conservation.

Learning Objectives:

1. Explain how nutrient cycling is influenced by

  • keystone species
  • aquatic-terrestrial linkages
  • water chemistry

2. Describe how ecosystem function, in the context of nutrient cycling, could be maintained by conserving individual species as well as linkages between ecosystems.

 

Support was provided by: A grant from the United States National Science Foundation (DBI-RCN-UBE 2120141).

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