Fig 1.
In the map, P represents the pristine sites, MI represents the moderately impacted sites by only people, HI represents the highly impacted sites by only people and HV represents the highly impacted sites by people and vehicles. Map was created with QGIS v3.0 software.
Fig 2.
Overall ghost crab burrow density and opening diameter among impact types.
Variation in burrow density (mean burrow/m-2 ±S.E.) (a) and burrow opening diameter (mm ±S.E.) (b) for O. quadrata among impact types on South Carolina beaches. (P = pristine sites, MI = moderately impacted sites, HI = highly impacted sites by only people, HV = highly impacted sites by people and vehicles). Letters above bars represent significant differences.
Fig 3.
Ghost crab burrow diameters among impact types.
Relationship between the diameter (mm) of O. quadrata burrows and the distance from backshore vegetation (m) on South Carolina sandy beaches (a = pristine sites, b = moderately impacted sites, c = highly impacted sites by only people, d = highly impacted sites by people and vehicles).
Table 1.
Summary of generalized linear mixed effects model (GLMM) with poisson distribution showing the burrow density (burrow/m2) in quadrats and sites under various types of human impacts compared to pristine sites.
Fig 4.
Ghost crab burrow density among impact types and height of the beaches.
O. quadrata burrow density (burrows/m2 ± S.D.) on South Carolina sandy beaches with various disturbance levels and with height on the shore (transects).
Fig 5.
Variation in burrow shapes among impact types.
Percent frequency (%) of O. quadrata burrow shapes among impact types on South Carolina beaches.
Fig 6.
Burrow metrics among impact types.
Variation in residual burrow volume (mean ± S.E.) (a), residual burrow depth (mean ± S.E.) (b) and inclination angle (mean ± S.E.) for O. quadrata among impact types on South Carolina beaches. Capital letters within graph represent significant differences (c).
Table 2.
Summary of linear mixed effects model (LMER) with a Gaussian distribution showing the residual burrow metrics (burrow volume (cm3), burrow depth (cm) and burrow inclination angle (°) of ghost crab populations after accounting for crab size in the sites under various types of human impacts compared to pristine sites.
Fig 7.
Variation in environmental properties in O. quadrata burrows and among disturbance types. a) relative ambient and burrows humidity (mean ± S.E.) among disturbance types, b) burrow and ambient temperature (mean ± S.E.) among disturbance types.