Invertebrate assemblages associated with root masses of Eichhornia crassipes (Mart.) Solms-Laubach 1883 in the Alvarado Lagoonal System, Veracruz, Mexico

This paper describes the spatial and temporal variation of aquatic invertebrate assemblages associated with root masses of Eichhornia crassipes collected at 12 sites between July 2000 and June 2002 in the Alvarado Lagoonal System (ALS), Veracruz, Mexico. A total of 96 taxa were registered; acari showed the highest species richness with 15 taxa followed by decapods (14), mollusks (12), amphipods (9), and isopods (7). Freshwater organisms represented 44% of the total taxa, 53% belonged to estuarine taxa, and marine taxa 3%. The isopod Munna sp. was the dominant taxon throughout the entire study period, followed by Ephemeroptera, Hyalella azteca, Chydorus sp., Physella sp., Podura aquatica, and Fossaria sp. during the low salinity period (July-September 2001, 1.6-3.8 psu), and Neritina virginea, Cassidinidea ovalis, Macrobrachium acanthurus and Melita longisetosa during the high salinity period (March-May 2001 9.7-12.7 psu and April-May 2002, 8.2-8.9 psu). A spatial gradient of species richness and diversity was registered for the freshwater organisms. Additionally, the spatial and temporal patterns of invertebrate densities could be explained due to the movements of Eichhornia crassipes mats through the system, and the temporal variation of environmental variables such as salinity, dissolved oxygen, and turbidity.