According to stream ecology theory, small head water streams rely on detritus from dense riparian vegetation. The amount of shade over the channel prevents algal growth and the main source of carbon for the food web is the leaf litter that enters from riparian vegetation. This is a well established point for many temperate region streams. However, some evidence indicates that tropical streams might present a different dynamics.
We studied small tropical forest streams in Puerto Rico to better understand their trophic basis. We measured secondary production of aquatic insects, an indicator of how much energy they move along food webs, and estimated the resources that were providing the energy necessary to support that production.
Important: We conducted this study before Hurricane Maria impacted the forest.
Our study indicates that aquatic insect production is based on allochthonous organic matter, which agrees with the small size and closed canopy cover over the study streams.
Some important points:
Rosas, K.G., Colón-Gaud, C. & A. Ramírez, 2020. Trophic basis of production in tropical headwater streams, Puerto Rico: an assessment of the importance of allochthonous resources in fueling food webs. Hydrobiologia. Read it here.
Our first study is the first quantification of secondary production and trophic basis of the non-shrimp macroinvertebrate assemblage in tropical island streams.
We studied small tropical forest streams in Puerto Rico to better understand their trophic basis. We measured secondary production of aquatic insects, an indicator of how much energy they move along food webs, and estimated the resources that were providing the energy necessary to support that production.
Important: We conducted this study before Hurricane Maria impacted the forest.
Our study indicates that aquatic insect production is based on allochthonous organic matter, which agrees with the small size and closed canopy cover over the study streams.
Some important points:
- Production estimates were similar to those reported for other tropical streams and low relative to temperate region reports.
- In contrast to most studies, production was much higher in pool than in riffle habitats.
- All insects consumed mostly amorphous detritus and plant tissue.
Rosas, K.G., Colón-Gaud, C. & A. Ramírez, 2020. Trophic basis of production in tropical headwater streams, Puerto Rico: an assessment of the importance of allochthonous resources in fueling food webs. Hydrobiologia. Read it here.
Our first study is the first quantification of secondary production and trophic basis of the non-shrimp macroinvertebrate assemblage in tropical island streams.
What’s next?
A large part of the secondary production measured in our study comes from amorphous detritus, a resource that is difficult to assign to a specific resource. We are now working with stable isotopes to better understand the energy source.
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