Structure of an epiphytic hydroid community on Cystoseira at two sites of different wave exposure

Anuschka Faucci,Ferdinando Boero

doi:10.3989/scimar.2000.64s1255

Anuschka Faucci, Ferdinando Boero

Open Access

https://doi.org/10.3989/scimar.2000.64s1255

Copy DOI

Abstract

Epiphytism is a strategy by which opportunistic species such as hydroids, escape the intense levels of competition in marine hard bottom communities. Species of the macroalgae Cystoseira have a seasonal turnover of the frond, and we hypothesise that epiphytic hydroids colonising such an unstable substrate might show some degree of specialisation. Here the first systematic study on hydroid-Cystoseira communities is presented. In particular, the seasonal and spatial distribution of epiphytic hydroids on three species of Cystoseira at two sites of different wave exposure at Porto Cesareo (Ionian Sea/Italy) were investigated. Thirty-two hydroid species were recorded which are well known from other substrates and thus are not specific to Cystoseira; dominant species were all thecates. The influence of biological factors such as competition and the structure and abundance of the host, seem to have little influence on the hydroid community. The factors of greatest influence were mostly abiotic: sedimentation rate, nutrient levels, temperature and most especially water movement. The importance of water movement was evident in the higher colonisation of algal stems, higher hydroid frequency, larger colonies, reduced colony height, species composition, and distribution on the stems at the wave-exposed site.

Highlights

The environmental factors limiting species distribution in marine benthic communities are temperature, light, water movement and substrate availability, among others
With a maximum of four species per stem, C. compressa was colonised by fewer species per stem than the other species of Cystoseira, both with maximal seven species per stem
This study examined the seasonal and spatial distribution of epiphytic hydroids on three species of the brown algae belonging to the genus Cystoseira

Summary

Introduction

The environmental factors limiting species distribution in marine benthic communities are temperature, light, water movement and substrate availability, among others. Water movement supplies the organisms with food, nutrients and dissolved gases, prevents accumulation of sediments, and disperses waste products and larvae, and acts as a mechanical stress factor. Many organisms have evolved morphological adaptations to withstand such stress. These structural responses are reflected by the different distribution of families, species, or morpho-types due to differences in water movement intensity (Riedl, 1966). Among sessile organisms increasing intensity of water movement induces smaller size, lower colony height, higher population density, and a morphology that withstands high mechanical stress (Riedl, 1971; Boero, 1981b, 1984). The distribution of adults is the result of competition and settlement behaviour, which is regulated by larval substrate choice (Hayward, 1980)

Methods

Results

Conclusion