The invertebrate colonization during decomposition of Eichhornia azurea Kunth in a lateral lake in the mouth zone of Paranapanema River into Jurumirim reservoir (São Paulo, Brazil).

N De L Stripari,R Henry

doi:10.1590/s1519-69842002000200014

N De L Stripari, R Henry

Open Access

https://doi.org/10.1590/s1519-69842002000200014

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Abstract

The invertebrate colonization during decomposition of Eichhornia azurea was observed in a lateral lake in the mouth zone of Paranapanema River into Jurumirim Reservoir in two periods of the year. The litter bags method was used for measuring the decomposition rate as well as to evaluate the invertebrates colonization. Forty-two litter bags, measuring 15 x 20 cm in size and 2 mm mesh net, were incubated "in situ". Six litter bags (three for colonization and three for decomposition measurements) were removed after the 1st, 3rd, 7th, 14th, 28th, 56th and 72nd days of incubation. After each day, the material was carefully cleaned for detritus removal and invertebrate sampling. The biological material was fixed with 4% formaline and then sorted and identified. The remaining plant material was dried in an oven (at 60 degrees C) and weighed. A fast material loss occurred during the first 24 hours and the decomposition rate was higher during the rainy season than in the dry season. A peak on invertebrate density (110 ind.g.DW-1) on the remaining detritus of Eichhornia azurea was recorded in the 56th day of dry season, when the polyphenol concentration of plant detritus was 0.57 UDO.g.DW-1. In the rainy season, higher density was found in the 28th day of incubation, when the polyphenol concentration was 4.36 UDO.g.DW-1. Apparently, the reduction in the polyphenol concentration was followed by an increase in invertebrate densities. The majority of the species observed in the detritus belongs to the collector group that was dominant after the 7th and 14th days in the rainy and dry seasons, respectively.

Highlights

Studies on invertebrates living in macrophyte stands have shown a great species richness and a high density of organisms when compared with the benthic fauna in sediments (Soszka, 1975; Ramcharan & Paterson, 1978). Vicent et al (1982) observed that the fauna in the macrophytes presents a magnitude of two to three times the abundance of zoobenthos in the litoral zone.Macrophytes are an important biotope for the aquatic invertebrates
According to Moschini-Carlos et al (1998), the marginal bay of Paranapanema, called Camargo Lake, receives riverine influences, specially when the hydrological level increases and a water input occurs into the lateral lake
The highest water level was observed in August during the dry season (Pompêo, 1996)

Summary

Introduction

Studies on invertebrates living in macrophyte stands have shown a great species richness and a high density of organisms when compared with the benthic fauna in sediments (Soszka, 1975; Ramcharan & Paterson, 1978). Vicent et al (1982) observed that the fauna in the macrophytes presents a magnitude of two to three times the abundance of zoobenthos in the litoral zone.Macrophytes are an important biotope for the aquatic invertebrates. Studies on invertebrates living in macrophyte stands have shown a great species richness and a high density of organisms when compared with the benthic fauna in sediments (Soszka, 1975; Ramcharan & Paterson, 1978). Vicent et al (1982) observed that the fauna in the macrophytes presents a magnitude of two to three times the abundance of zoobenthos in the litoral zone. Macrophytes are an important biotope for the aquatic invertebrates. A significant number of organisms use this habitat for reproduction, for protection against predators and for food resources, during part or all their life cycle. According to Gadelha et al (1990), the aquatic macrophytes present high nutritive quality and are an important food resource for aquatic animals. In some ecosystems, they are a very significant source of organic matter for the detritivorous chain, specially in tropical regions where the high temperatures increase the decomposition velocity of particulate matter (Junk et al, 1989)

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