Introduction:

The fauna from the subsurface sediments where groundwaters and surface waters are exchanged, called “hyporheic fauna”, fulfills important ecological functions in rivers, but has not been sufficiently studied in Colombia.

Objective:

To identify relationships between hyporheic invertebrates and physicochemical variables in the Dagua River, Colombia.

Methods:

In three field trips (between October 2017 and December 2018) to five sites along the river basin, we drilled with the Karaman-Chappuis method (sediment, water, and invertebrates), and recorded granulometry and organic matter in sediments; and nutrients, ions, and metals in water.

Results:

The headwater stations had substrates with coarser sediments (gravel and stone), higher oxygen levels, and lower water temperature. Both richness and species diversity were higher at the headwater stations, dominated by Copepoda and Insecta, while the lower basin was dominated by Arachnida (Hydrachnidiae), Clitellata (Oligochaeta), and Nematoda.

Conclusions:

The distribution and abundance of the hyporheic fauna were principally influenced by changes in the granulometry of the hyporheic substrate and its content of organic matter.