Aquaculture America 2021

August 11 - 14, 2021

San Antonio, Texas

ECOLOGICAL MANAGEMENT OF NUISANCE ALGAL BLOOMS AND AQUATIC WEEDS IN STREAMS AND PONDS

 Patricia L. Duncan
 Ecological Aquatic Systems  Research and Management
Uvalde, Texas
patduncan@swtexas.net
 

Habitat degradation, excessive nutrients, reduced streamflow and water  scarcity  create  an environment conducive to  undesirable algal blooms and nuisance aquatic weeds in  streams and ponds. Nuisance algal blooms and aquatic weed s are often removed with  herbicides or chemical treatments .   The application of chemical treatments not only removes target species but also  removes beneficial bacteria and algal species, along with disrupting the existing microbial ecosystem which assimilates nutrients and wastes.  An alternative method  to chemical treatments  is to enhance the natural microbial communities to process nutrients and waste.

The W ater C leanser (Marine Easy Clean, Aust.) provides an alternate means of eliminating algal blooms, including Cyanobacteria and filamentous algal mats.  The Water Cleanser  is a wax block infused with carbonaceous  and trace  elements along with millions of microscopic capillaries which provide habitat for beneficial bacteria.  T he development of a biofilm of beneficial bacteria and other microbiota, increases the process of organic waste decomposition.

Methods of utilizing blocks to eliminate Cyanobacteria and filamentous algal  blooms along with aquatic weeds were developed for streams and ponds .  Blocks were evaluated in  different  high and low flow streams at numerous sites.  The blocks were also evaluated in three one- acre ponds with  Comanche Springs pupfish with duplicate ponds with blocks and a control pond receiving no treatment. Ponds were monitored for water quality, dissolved oxygen, fish health  and  abundance.   Blocks were also evaluated in channel catfish ponds.

The blocks were effective in eliminating Cyanobacteria and filamentous algal blooms in ponds and streams.  Cyanobacteria , filamentous algal  blooms  and Chara  sp. were eliminated within one to two weeks with the use of blocks in streams. Untreated parts of the stream continued to have nuisance algal blooms.  Blocks were used in pupfish ponds  with existing Cyanobacterial mats, filamentous algae and Chara sp.   Besides reducing Cyanobacteria, filamentous algae and Chara sp. ,  zones of submerged aquatic plants were  also eliminated.  D issolved oxygen concentrations were less variable  in treated ponds than in the pond with no blocks .  When adequate numbers of blocks were used in channel catfish ponds, there was improved water quality and the elimination of algal mats and selected weeds. Overall, the blocks were effective in algae, Cyanobacteria and selected aquatic plant removal when the appropriate number and placement of blocks were employed. Proper use of the blocks resulted in improved water quality, health and propagation in the both  channel catfish and pupfish.