Diversity and abundance of conspicuous macrocrustaceans on coral reefs differing in level of degradation

Abstract

Coral reefs sustain abundant and diverse macrocrustaceans that perform multiple ecological roles, but coral reefs are undergoing massive degradation that may be driving changes in the species composition and abundance of reef-associated macrocrustaceans. To provide insight into this issue, we used non-destructive visual census techniques to compare the diversity and abundance of conspicuous macrocrustaceans (i.e., those >1 cm and visible without disturbance) between two shallow Caribbean coral reefs similar in size (∼1.5 km in length) and close to each other, but one (“Limones”) characterized by extensive stands of the branching coral Acropora palmata, and the other (“Bonanza”) dominated by macroalgae and relic coral skeletons and rubble (i.e., degraded). We also assessed the structural complexity of each reef and the percent cover of various benthic community components. Given the type of growth of A. palmata, we expected to find a greater structural complexity, a higher cover of live coral, and a lower cover of macroalgae on Limones, and hence a more diverse and abundant macrocrustacean community on this reef compared with Bonanza. Overall, we identified 63 macrocrustacean species (61 Decapoda and two Stomatopoda). Contrary to our expectations, structural complexity did not differ significantly between the back-reef zones of these reefs but varied more broadly on Limones, and the diversity and abundance of macrocrustaceans were higher on Bonanza than on Limones despite live coral cover being higher on Limones and macroalgal cover higher on Bonanza. However, the use of various types of microhabitats by macrocrustaceans differed substantially between reefs. On both reefs, the dominant species were the clinging crab Mithraculus coryphe and the hermit crab Calcinus tibicen, but the former was more abundant on Bonanza and the latter on Limones. M. coryphe occupied a diverse array of microhabitats but mostly coral rubble and relic skeletons, whereas C. tibicen was often, but not always, found associated with colonies of Millepora spp. A small commensal crab of A. palmata, Domecia acanthophora, was far more abundant on Limones, emerging as the main discriminant species between reefs. Our results suggest that local diversity and abundance of reef-associated macrocrustaceans are partially modulated by habitat degradation, the diversity of microhabitat types, and the establishment of different commensal associations rather than by structural complexity alone.

Coral Reef Degradation Differentially Alters Feeding Ecology of Co-occurring Congeneric Spiny Lobsters

“…Habitat degradation and fragmentation is known to affect the trophic ecology and isotopic niche of fish mesopredators (Layman et al, 2007b;Ashworth et al, 2014;Hempson et al, 2017;Letourneur et al, 2017), but here we examined the impact of coral reef degradation on the trophic ecology of two co-occurring, omnivorous mesopredatory spiny lobsters. Our analysis of benthic constituents confirmed that, of our two study reefs, Bonanza is more degraded, with far more cover of fleshy and calcareous macroalgae as well as cyanobacterial mats, whereas Limones still has abundant coral communities dominated by A. palmata (Rodríguez-Martínez et al, 2014;González-Gómez et al, 2018;Morillo-Velarde et al, 2018). We found that the trophic ecology of P. guttatus (the habitat specialist) appeared to be more impacted by reef degradation than that of P. argus.…”

“…By contrast, on the fore-reef zone (the exposed zone of the reef facing the open sea) the coral cover is mostly of low relief and is limited to a depth of ∼25 m by a broad sand platform that extends to the edge of the continental slope (Jordán-Dahlgren, 1993). The present study is part of a larger research project into the impacts of coral reef degradation on local food webs and associated communities (González-Gómez et al, 2018;Morillo-Velarde et al, 2018). The research was conducted on two large coral reef units differing in level of degradation, "Limones" (centered at 20 • 59.1 N, 86 • 47.9 W) and "Bonanza" (centered at 20 • 57.6 N, 86 • 48.9 W).…”

“…However, in order to understand reef dynamics under rapidly changing conditions, it is necessary to assess ecological changes in other groups, such as motile invertebrates, as these organisms serve as trophic links and can drive key ecological processes on coral reefs (Stella et al, 2011;Kramer et al, 2015). Although these groups have overall been less studied than corals and reef fishes, recent works have found little effects of reef degradation on the diversity or abundance of mobile reef-associated invertebrates in general and of crustaceans in particular (Head et al, 2015;Nelson et al, 2016;Lozano-Álvarez et al, 2017;González-Gómez et al, 2018). Reef degradation, however, may affect associated species in sub-lethal, more subtle ways, such as altering their trophic niche (Letourneur et al, 2017) or reducing their physiological condition due to changes or declines in food availability or quality (Pratchett et al, 2009;Hempson et al, 2018).…”

Host-related Morphological Variation of Dwellings Inhabited by the Crab Domecia acanthophora in the Corals Acropora palmata and Millepora complanata (Southern Caribbean)

“…Here, the same crab was also found in Acropora cervicornis (Lamarck, 1816) and Acropora prolifera (Lamarck, 1816), while it was also observed wandering on corals of other species [12,13]. Domecia acanthophora has also been reported as associated fauna of fire corals, like Millepora alcicornis Linneaus, 1758 at Brazil [14] and Millepora spp, at Yucatán, México [15]. However, no information is available on the morphology of Domecia pits in Millepora and its possible difference with Acropora.…”

Untangling the effects of size, habitat and invertebrate biodiversity on parasite prevalence in the Caribbean spiny lobster

“…All underwater identifications were conducted by two scientific observers thoroughly trained prior to the samplings. Training was achieved by repeatedly studying an extensive guide of local invertebrate species created in our lab from photos and drawings obtained from many different sources (e.g., Stanley 1970;Chace 1972;Abbot 1974;Williams 1984;Abele and Kim 1986;Wagner 1990;Humman 1994;Hendler et al 1995;García-Cubas et al 1999;Medina et al 2006;Ng et al 2008;Laguarda-Figueras et al 2009;McLaughlin et al 2010; de Grave and Fransen 2011; Diez García and Jover Capote 2015; Carmona-Suárez and Poupin 2016), followed by direct identification in the field during preliminary dives, with the results being cross-checked between both divers (Lessios 1996;González-Gómez et al 2018).…”