Benthic Macroinvertebrates: River Health Indicators

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San Antonio River and foliage.

Last Updated on March 31, 2023

As part of our commitment to safe, clean, enjoyable creeks and rivers, the San Antonio River Authority (River Authority) relies on water quality scientists, aquatic biologists, stormwater scientists, and environmental investigators to collect and analyze data that identifies positive and negative conditions in the San Antonio River. As part of water quality monitoring efforts, our aquatic biologists use a variety of indicators and some of them can be found in nature itself.

Benthic macroinvertebrates are an example of bio-indicators of river health. Read along as we share info from our aquatic biologists, who you may see collecting water samples to monitor the health of our creeks and rivers when you visit the river.

What are Benthic Macroinvertebrates?

Mayfly larvae (Family Ephemeropteraare found in the San Antonio River Basin 

Benthic macroinvertebrates are organisms that lack a backbone and are visible without the aid of a microscope. Aquatic macroinvertebrates are good indicators for stream health. They spend all or most of their lives in the stream, are easy to catch and the different species have different tolerances to pollution.  These aquatic macroinvertebrates live under and on rocks, leaf litter, woody debris, plants in the stream, and sediment of the stream bottom. They are also found in different flow types: fast-moving and slow-moving streams. It’s easy to collect macroinvertebrates. Simply pick up rocks or sticks from a stream and look closely!

Benthic macroinvertebrates are a vital part of the food web and play an important role in our ecosystem. They are affected by chemical, physical, and biological conditions of a stream. Their limited mobility does not allow them to escape pollution and show effects from long- and short-term pollution events.

River Health Indicators

River Authority staff conducting a kick sampling technique

River Authority staff conducting a kick sampling technique 

(SCIENCE TERM AHEAD! A taxon [or plural: taxa] is a unit of any rank designating an organism or a group of organisms. This is also known as a taxonomic unit.)

The abundance and diversity of the various taxa are indications of river health. Rivers in healthy biological condition support a wide variety and high number of macroinvertebrate taxa, including many that are intolerant of pollution. Samples yielding only pollution–tolerant species or very little diversity or abundance may indicate a less healthy waterbody.

Some of the species that may be found in the San Antonio River Basin include:

Water Penny                    Dragonfly                         Midge

Riffle Beetle                      Crayfish                             Leech

                         Scud                                   Blackfly

Mayfly                               Caddisfly                           Aquatic Worm                                                                                                                                        

Learn More About River Health!

report card home banner

The River Authority developed the San Antonio River Basin Report Card to shine a light on the healthy and the unhealthy aspects of the basin in order to educate the public and serve as a catalyst for community discussions that lead to individual choices and public policy decisions, actions, and investments that support a sustainable San Antonio River Basin. The River Authority selected 12 indicators that were based on observations of basin health and comprised of accessible and defensible data that’s easy to understand for all audiences. We invite you take a look and learn the status of the basin and what you can do to help improve the health of our basin! 

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Alerts

SASPAMCO Paddling Trail Temporarily Closed

Staff have removed two large log jams just downstream of Helton Nature Park, keeping the southern portion of the SASPAMCO Paddling Trail temporarily closed. Staff are working to contact adjacent landowners to support a land-based removal solution.

Stem Density Efforts

Please be advised that trails near the Confluence Park and Conception Park area will be temporarily closed due to ongoing Stem Density efforts. We appreciate your cooperation and ask that you remain mindful of workers and closures when in the vicinity. Thank you for your patience as we work to improve our natural spaces!

 

Gas Spill

The San Antonio River Authority and the City of San Antonio are actively working to contain a recent gas spill in the Downtown River Walk Loop area, which occurred earlier today. The source of the spill is unknown but has stopped. At this time, no environmental impacts have been observed, and teams are implementing measures to fully contain and remove the substance. We will provide updates as the situation develops.

West Bank Trail Closure Notice

Due to the construction of a new trail and bridge, the West Bank of the trail between Schiller St. and Newell St. will be closed for the next couple of months. The East Bank will also be intermittently closed on Monday, November 4th, to install the bridge. Please use caution when navigating around this area. We apologize for any inconvenience.

Please refer to the map for reference. 

San Pedro Creek Culture Park

The restrooms at South Alamo will be temporarily closed for maintenance and repairs. We apologize for any inconvenience and appreciate your understanding. 

Acequia Trail Notice

The Acequia trail will have heavy traffic near MROC starting May 22nd until further notice. The SAWS Acequia project will be bringing in crews to work on the lift station site and across the street. There will have flaggers to stop traffic, please use caution. 

SASPAMCO Paddling Trail

The SASPAMCO paddling trail is open from River Crossing Park to Helton Nature Park.
*Please Note: Paddling Trail from Helton Nature Park to HWY 97 is still closed due to blockages. 

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