Temporal variability of sedimentation rates and mobile fauna inside and outside a gorgonian garden

Abstract

Paramuricea clavata (Cnidaria, Octocorallia) is an important ecosystem engineer of coralligenous assemblages increasingly threatened by anthropogenic activities and climate changes. As climate warming is predicted to continue in the coming years it is important to hypothesize future scenarios. Here we tested the influence of gorgonian colonies on sedimentation rates and vagile fauna trends, comparing sediments collected by traps inside and outside a gorgonian garden, in a coralligenous community of the Western Ligurian Sea, at 32 m depth, over a period of 1 year. The results indicated that sea fans created a sort of homeostatic effect on the surrounding habitat. We found evidence that where gorgonian colonies were present, the monthly fluctuations of sediments rate were lower than outside a garden. Gorgonian colonies also influenced the distribution of the associated vagile fauna; these organisms were generally more abundant inside than outside the garden. The data collected in this work appear to confirm the role of P. clavata as an ecosystem engineer, affecting biomass and variability of the surrounding habitat at both spatial and temporal scales.

The understorey of gorgonian forests in mesophotic temperate reefs

“…At high gorgonian density, edaphic conditions (e.g. physical factors such as light, currents, and sedimentation rates) may be strongly modified, increasing habitat complexity and supporting many necto‐benthic organisms (Cerrano et al, ; Ponti et al, ; Valisano, Notari, Mori, & Cerrano, ). This study highlighted that the direct or indirect effects of the gorgonians on the abundance of other species, such as green algal turfs and non‐encrusting peyssonneliacean algae, may vary with gorgonian density, in terms of percentage cover.…”

“…Moreover, the habitat complexity built up by ecosystem engineers induces physical changes, but may also modify many biological processes, with unpredictable ecological effects (Kelaher, ). Although the mechanisms underlying these processes are still not well understood, forests of P. clavata , besides modifying the microscale hydrodynamics, may provide additional food resources, being an effective suspension feeder able to modify littoral marine food webs (Coma et al, ; Gili & Coma, ), and increase refuges and the available surface area (Ponti et al, ; Valisano et al, ), as well as affect recruitment processes (Ponti et al, ). According to the present results, these animal forests support high species diversity and promote bioconstruction processes in their understorey.…”

Local Ecological Knowledge Indicates Temporal Trends of Benthic Invertebrates Species of the Adriatic Sea

“…VMEs and EFHs include spawning, nursery and feeding grounds, together with foundation species (Dayton, 1972), i.e., "a single species that defines much of the structure of a community by creating locally stable conditions for other species, and by modulating and stabilizing fundamental ecosystem processes." This is the role played for examples, by the animal forests, in particular anthozoans (Cerrano et al, 2010;Valisano et al, 2016) whose functional and structural role is receiving increasing attention (Rossi et al, 2017). Numerous initiatives have been developed in order to map the presence and distribution of VMEs and EFHs, and to provide useful tools to help managers and decision makers in the selection of priority areas and in the definition of management plans to ensure the long-term conservation and sustainable use of marine resources (Stecf, 2006;OSPAR Commission, 2010;Rogers and Gianni, 2010;Rengstorf et al, 2013).…”

Resilience of Octocoral Forests to Catastrophic Storms

“…Under the environmental and biotic conditions prevailing on present-day shallow Caribbean reefs, octocoral communities have exhibited resilience and some resistance 51,60 to major disturbances including hurricanes (present data), bleaching 61 , eutrophication 24 , diseases 62 and early signs of the effects of ocean acidification on seawater pH 63,64 . At high population densities, Caribbean octocorals form underwater forests 50 that alter environmental conditions, such as light, currents, and sedimentation, beneath their canopy, and create habitat utilized by many species 50,65,66 . Octocoral forests, unlike scleractinians, do not build hard, wave resistant structures, but they provide some of the ecosystem services formerly supported by scleractinians (e.g., providing fish habitat 67 , acting as a carbon sink 68 and generating sediments 69 ).…”