2007) with raw data from an earlier study of macroalgal biomass levels in the same area (Amsler

et al. 1995), Amsler et al. (2008) estimated amphipod densities per unit area of the benthos in solid stands of the dominant brown macroalgae as over 300,000 amphipods · m−2 on D. menziesii and over 30,000 amphipods · m−2 on D. anceps. Richardson (1977) reported 11,253 amphipods from a single D. anceps individual at a more northerly location in the WAP, which is consistent with the estimate for our study area. Similarly, densities on the common, understory red alga Plocamium cartilagineum (Linnaeus) Dixon were estimated at over 26,000 amphipods · m−2 (Amsler et al. 2008). These estimated densities are one to three orders of magnitude higher than most reported amphipod densities in temperate and tropical waters (e.g., Nelson this website 1980, Wildish 1988, Brawley 1992, Reynolds et al. 2012, Myers and Heck 2013) and are particularly RO4929097 nmr impressive because D. menziesii and especially D. anceps commonly cover very wide areas of the benthos, often with nearly 100% cover (Wiencke and Amsler 2012, Wiencke et al. in press, authors’ personal observations). Although the macroalgal-associated amphipod fauna (Huang et al. 2007)

includes suspension feeding taxa such as members of family Ischyroceridae and predators such as Bovallia gigantea, a majority of the species are currently members of family Pontogeneiidae and are primarily considered to be herbivores and omnivores (Thurston 1972, 1974, De Broyer et al. 2007). No analysis of associated amphipod

density is available for the much larger, blade-forming H. grandifolius that dominates in deeper waters because its size precludes the quantitative sampling methods employed by Huang et al. (2007). However, Huang et al. (2007) observed lower PRKD3 amphipod densities on smaller blade-forming species compared to the highly branched Desmarestia spp. and P. cartilagineum and this is consistent with our personal observations of relatively lower amphipod densities on H. grandifolius. H. grandifolius does, however, appear to us to support relatively higher densities of gastropods, particularly of larger gastropod species, than the other dominant brown macroalgae. There are several reports of gastropod grazers being numerous in association with the larger macroalgae in the WAP (Richardson 1977, Picken 1979, 1980, Iken 1999). We have recently analyzed the gastropod fauna associated with the same individual macroalgae from which Huang et al. (2007) enumerated amphipods in our study area. Of the eight macroalgal species sampled, gastropod densities were generally an order of magnitude lower than amphipod densities, and were also somewhat lower than in previous reports from the region (Richardson 1977, Picken 1979, 1980). However, densities still ranged up to nearly one gastropod per gram wet algal biomass (M.O. Amsler, Y.M. Huang, unpublished).

No related posts.