Temporal variation of amphipod assemblages associated with Sargassum filipendula (Phaeophyta) and its epiphytes in a subtropical shore

Abstract

The phytal assemblages change in response to variation in biological and environmental conditions. In the present study, we evaluated the temporal variation of amphipod assemblages associated with a Sargassum filipendula bed in a subtropical shore, in relation to variation of the host alga, its epiphytes and local environmental conditions. Samples of S. filipendula with associated amphipods, water temperature, water movement and suspended solids were obtained monthly from June 2000 to May 2001. We recorded 24 species of amphipods associated with S. filipendula. Species richness varied throughout the year, with maximum values in October 2000 and minimum in April 2001. Total amphipod density gradually increased during the sampling period, with the highest value in March 2001. Amphipod diversity and evenness were both positively influenced by epiphyte load and negatively by temperature, with higher values during summer months. Total density and tube-builder density were also positively influenced by temperature, whereas nestler density was influenced by epiphyte load. Individual amphipod species showed significant density fluctuations over the year. The canonical correspondence analysis performed explained 88.2% of the variation, with a strong correlation of water movement, temperature and suspended solids with the first axis, and a strong effect of epiphyte load on both the first and the second axes. The temporal structural variation of the studied algal bed strongly influenced amphipod diversity and assemblage composition, possibly through direct and indirect effects.

Variation of amphipod assemblage along the Sargassum stenophyllum (Phaeophyta, Fucales) thallus

“…Despite the limitations of this work concerning time and spatial sampling, we are confident that the results allow a consistent discussion since the families of amphipods found here are frequently associated to Sargassum in this region (Tanaka and Leite, 2003;Jacobucci et al, 2009). Moreover, considering these amphipod families have a wide distribution (Barnard and Karaman, 1991), we point out the patterns found in our study may be observed in other areas with straight thallus algae.…”

“…Natural history aspects, such as behavior and feeding habits, can influence the occurrence of amphipods in macroalgae (Tanaka and Leite, 2003;Jacobucci et al, 2009). The basal portion of Sargassum may be less subject to the action of waves (Rossi et al, 2000;Fraschetti et al, 2006) and because of the proximity to the physical substrate and the weak currents, it may accumulate a larger amount of particles (e.g.…”

“…The Sargassum fronds have approximately 30 cm of height and compose dense patches. We performed our sampling in the spring (October 2013), when most of the amphipods associated to Sargassum occur (Tanaka and Leite, 2003;Jacobucci et al, 2009).…”

“…Among its associated fauna, the amphipods present high abundance and species richness (Tanaka and Leite, 2003;Jacobucci et al, 2009), making them especially sensitive to changes in the spatial physical structure of the substrates. The amphipod assemblage associated to Sargassum presents distinct behavior and feeding habits (herbivores, predators and detritivores) (Barnard and Karaman, 1991;Guerra-García et al, 2014) that can promote changes in the species community regarding their use of microhabitats.…”

The role of epiphytic algae and different species of Sargassum in the distribution and feeding of herbivorous amphipods

“…These species can show distinct frond dimensions and degree of branching depending on water movement (Paula, 1988;Széchy & Cordeiro-Marino, 1991). This structural variation can determine differences in the composition and relative abundance of epiphytic algae and of the associated epifauna (Jacobucci et al, 2009). Among the organisms of the macro-epifauna whose occurrence can be influenced by the presence of epiphytes in Sargassum fronds, there are various species of amphipods (Norton & Benson, 1983;Martin-Smith, 1993;Viejo, 1999;Leite & Turra, 2003), some of which utilize algae not only as refuge, but also as a food resource.…”