The effect of wind exposure and filamentous algae on the distribution of surf zone macroinvertebrates in Lake Esrom, Denmark

Abstract

Distribution and composition of the epilithic macroinvertebrate fauna was studied on 21 different sites situated in the surf zone of Lake Esrom . A relative degree-of-exposure (windinduced wave activity) was calculated for each station from the specific number of wind days, wind velocity and a measured wind fetch . Macroinvertebrate abundance averaged 20200 ind . m-2 stone bottom, and was composed primarily of six taxa (70% of the mean densities) . The distribution patterns of the 48 most common taxa were compared to exposure, the amount of filamentous algae and shore slope, by regression, cluster analysis and ordination analysis (PCA and RDA) . The abundance of 25 taxa was significantly correlated to the amount of filamentous algae, and a protectional effect of algae growth was suggested for the exposed sites . Seventeen taxa showed significant difference in abundance between sheltered western stations and exposed eastern stations . Stations with a gentle slope were characterised by sand covered stones and a fauna that qualitatively was similar to the fauna at greater depth in the littoral . Redundancy analysis (RDA) showed filamentous algae and slope to be the most important factors controlling the species distribution, whereas the gradient of exposure in Lake Esrom was too short to explain the species tolerance range .

Ecology of freshwater shore zones

“…Although there are devices to measure exposure as either peak wave energy (Bell and Denny 1994;Guinez and Pacheco 1999) or dissolution rate of a substance such as gypsum (Petticrew and Kalff 1991; Thompson and Glenn 1994;Porter et al 2000), these methods are rarely used in fresh water. Instead, exposure usually is estimated by measuring the wind fetch at a site (Keddy 1982;Brodersen 1995;Ekebom et al 2003), if it is estimated at all. Exposure acts as a disturbance (e.g., Keddy 1983) that dislodges or kills organisms.…”

“…Likewise, the effects of exposure may depend on the biota of a site, as some plants and sessile animals are able to ameliorate the effects of exposure for other organisms (Fig. 10;Brodersen 1995;O'Donnell 2008). Disturbances other than wind and wave action also are important.…”

“…We will not document all of these interactions, but simply cite a few examples to show the strength and diversity of these interactions. Aquatic and terrestrial plants support animal communities that differ from those of unvegetated sediments, and often differ across plant species (e.g., Moon 1934;Brodersen 1995;Radomski and Goeman 2001;Romanuk and Levings 2003;Salovius and Kraufvelin 2004;Kraufvelin and Salovius 2004). Consequently, invasions of alien plants frequently not only push out native plants but also change associated animal communities (e.g., Ailstock et al 2001;Strayer et al 2003).…”

Epiphytic chironomids on rigid hornwort (Ceratophyllum demersum L.) - the relation between the community structure and lake status

“…al. 1998;Chaloner, Wotton 1996), the periphyton abundance and the slope (Brodersen 1995;James et al 2000).…”

“…The structure of phytophilous invertebrates is closely related to habitat conditions, among them the distribution and species composition of macrophytes and associated epiphytic algae become the most important ones (Brodersen 1995;van den Berg 1997;Weatherhead, James 2001). The species composition and biomass of macroinvertebrates usually differ between plant species.…”