Evidence on Night Movements of Macroinvertebrates to Macrophytes in a Pampean Stream

Nicolás Ferreiro

doi:10.4236/ojmh.2014.43009

Abstract

Nocturnal invertebrate abundance peaks in lotic systems are usually associated to drift, however, diel migrations other than drift may be important in slow-flowing systems. Then, macroinvertebrate distribution on macrophytes may change along the day as result of vertical or horizontal migration from sediments or the water column. My objective was to determine whether macroinvertebrate abundance on macrophytes changes along 24 h. Three Ceratophyllum demersum patches were sampled in late spring from the Las Flores stream (Central Argentina) at 11:20 h, 17:10 h, 23:00 h and 5:00 h. Macroinvertebrates were counted and identified, and relative abundances were estimated for each sampling time. The dominant groups of macroinvertebrates sampled were Oligochaeta, Amphipoda and Cladocera. The relative abundance of macroinvertebrates on macrophytes was the highest at 5:00 h, when dissolved oxygen in water reached its minimum. In conclusion, the abundance of macroinvertebrates on macrophytes in Pampean streams may increase at night, probably as result of nocturnal migration driven by changes in predation risk or dissolved oxygen.

Highlights

The darkness is an environmental condition that is as important as light to almost all living organisms, How to cite this paper: Ferreiro, N (2014) Evidence on Night Movements of Macroinvertebrates to Macrophytes in a Pampean Stream
Night movements are associated with a behavioral change which is mainly explained by differences in light intensity [2] [6], some have reported oxigen driven (Wiley & Kohler, 1980) and endogenous behavioral changes [7]
A great variation among macrophyte patches for each sampling time and among sampling times for each patch was found in macroinvertebrate density (Figure 1) and relative abundance (Figure 2)

Summary

Introduction

The darkness is an environmental condition that is as important as light to almost all living organisms, How to cite this paper: Ferreiro, N (2014) Evidence on Night Movements of Macroinvertebrates to Macrophytes in a Pampean Stream. While in lotic systems it has long been recognized the existence of a nocturnal peak in drift rates [3] [4], in lentic systems the existence of diel vertical migration is well known [5]. In both cases, night movements are associated with a behavioral change which is mainly explained by differences in light intensity [2] [6], some have reported oxigen driven (Wiley & Kohler, 1980) and endogenous behavioral changes [7]. Since natural light and dark cycles have existed throughout evolutionary time, many organisms may have evolved behaviors that are cued by or are dependent upon darkness, like foraging and reproductive behaviors [8]

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