Arthropod mesograzers reduce epiphytic overgrowth of subtidal coralline turf

Abstract

Benthic primary producers such as seaweeds and seagrasses are often inhabited by high densities of small arthropods, but little is known about the impact of these animals on their hosts, which could be positive if they keep them free of fouling epiphytes. We assessed the impact of small arthropods on algal epiphytes growing on coralline algal turf on a shallow, wave-exposed, rocky reef in warm temperate northeastern New Zealand. Plaster blocks impregnated with the insecticide carbaryl were used to reduce arthropod densities (by 96% relative to unmanipulated controls in the case of amphipods). By the end of the ~3.5 mo experiment total epiphyte cover was 88% when arthropods were excluded compared to 38% in unmanipulated controls, a 2.3-fold increase. Brown (Colpomenia spp.), green (Ulva spp.) and 'filamentous and microscopic' algal epiphyte taxa were responsible for the increase, while the cover of red foliose algal epiphytes decreased slightly. Hyalid amphipods (Protohyale spp.) were likely responsible for suppressing the epiphytes, as they were the most abundant arthropod mesograzer taxon and ate both Colpomenia spp. and Ulva spp. in a laboratory no-choice feeding assay. During the field experiment 2 large storms removed most of the epiphytes that had grown in the mesograzer exclusion treatment. Overall, our results indicate that the amphipods prevented overgrowth of the turf by epiphytes during calm periods. These results provide the first in situ cageless example of arthropod mesograzer-exerted control on the abundance and composition of primary producers on a subtidal rocky reef.

Habitat degradation alters trophic pathways but not food chain length on shallow Caribbean coral reefs

“…In addition, turf traps vast amounts of detritus, and some fishes that are considered as herbivorous actually feed on the detritus trapped in the turf 50 . Also importantly, algal turf constitutes one of the most productive habitats for small reef mesograzer invertebrates, in particular small crustaceans such as amphipods, isopods, ostracods, and tanaids 51 , 52 , which can be consumed by fishes 53 , 54 . Therefore, turf-feeding herbivores constitute an important trophic link between benthic primary production and secondary consumers 55 , 56 , especially since the use of stable isotopes has revealed that predators on coral reefs consume more herbivorous prey (both fishes and invertebrates) than previously reported 57 .…”

Macaronesian islands as promoters of diversification in amphipods: The remarkable case of the family Hyalidae (Crustacea, Amphipoda)

“…Like other peracarideans, development is direct, lacking a larval phase, which restricts species dispersal ability (Naylor, ). The occurrence and abundance of hyalid species are usually related to the complexity of the algal species, with juveniles preferring filamentous algae (e.g., Pterosiphonia , Gymnogongrus ), while the adults occur in less ramified and foliaceous algae (e.g., Sargassum , Gelidium , Ulva ) (Dubiaski‐Silva & Masunari, ; McBane & Croker, ; Moore, ) but they are also reported to have diet preferences in general (Berthelsen & Taylor, ). The exact number of Hyalidae species in NEA is uncertain, but at least 13 species have been reported in this region (De Broyer, Lowry, Jażdżewski, & Robert, ; Horton et al, ; Ruffo, ).…”

Bending strategies of convergently evolved, articulated coralline algae

“…Indeed, some degree of herbivory may help corallines thrive, as it facilitates the removal of epiphytes and fouling organisms from the epithallial surface (Steneck , Littler et al. , Berthelsen and Taylor ). While calcification may not completely prevent herbivory, it could provide just enough resistance to limit the depth of grazing that occurs or to facilitate rapid recovery (Steneck et al.…”

“…While calcification has typically been considered a (Littler and Littler 1980, Steneck and Watling 1982, Pennings and Paul 1992, this is largely dependent on the type of herbivore and it is associated feeding apparatus (Padilla 1989, Maneveldt andKeats 2008). Indeed, some degree of herbivory may help corallines thrive, as it facilitates the removal of epiphytes and fouling organisms from the epithallial surface (Steneck 1982, Littler et al 1995, Berthelsen and Taylor 2014. While calcification may not completely prevent herbivory, it could provide just enough resistance to limit the depth of grazing that occurs or to facilitate rapid recovery (Steneck et al 1991).…”