Abstract
Ecosystem engineers can modulate harsh abiotic conditions, thus creating habitat for species that cannot withstand the local environment. In this study, we investigated if vacant boreholes created by the rock-boring bivalve Petricola dactylus increase species richness in the low intertidal zone of a Patagonian rocky shore characterized by intense hydrodynamic forcing and sediment scour. Invertebrate species richness was three times higher in engineered than unengineered habitats (i.e., with and without Petricola boreholes, respectively) and the increase in species richness was area-independent. The most prevalent species in unengineered areas showed strong adhesion mechanisms, whereas infaunal and vagile species were mostly restricted to boreholes. The positive influence of engineered microhabitats on species richness can largely be attributed to amelioration of physical conditions, particularly a reduction in hydrodynamic forces and sediment trapping/stabilization within boreholes. We conclude that vacant boreholes are essential microhabitats for the maintenance of biodiversity within the otherwise inhospitable low intertidal zone.
Highlights
Local abiotic conditions are often suitable to a fraction of the species in the broader species pool (e.g., [1,2])
We evaluate if the microhabitats created by a physical ecosystem engineer—the rock-boring bivalve, Petricola dactylus—positively contribute to species richness in the physically harsh, low intertidal zone of a southwestern Atlantic rocky shore
Since the microhabitat within boreholes is protected from extreme hydrodynamic forces and scour and, as a consequence, retains sediments, we predicted that it will positively contribute to the overall invertebrate species richness of the low intertidal zone and, to an extent, an area larger than what it adds to the seabed
Summary
Local abiotic conditions are often suitable to a fraction of the species in the broader species pool (e.g., [1,2]). Since the microhabitat within boreholes is protected from extreme hydrodynamic forces and scour and, as a consequence, retains sediments (i.e., a critical habitat element for the infauna, Figure 1c), we predicted that it will positively contribute to the overall invertebrate species richness of the low intertidal zone and, to an extent, an area larger than what it adds to the seabed. To test this prediction, we compared invertebrate species richness in patches with and without P. dactylus boreholes, and evaluated if differences in species richness are proportional to the amount of surface area sampled in each patch type.
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