Synergistic effect of extreme climatic events and urbanization on population density of the ghost crab Ocypode quadrata (Fabricius, 1787)

Abstract

The combined effects of urbanization and extreme climatic events were examined on the ghost crab Ocypode quadrata, a well‐recognized ecological indicator in sandy beaches. The effect of storm waves was assessed before and after these climate events in beaches with different levels of urbanization in the coast of Brazil, Tropical Atlantic Ocean. The number of burrows was used as a metric for the population size of O. quadrata and the number of humans along the beaches as a proxy for the urbanization level. Significant differences were recorded in this species’ population density according to the human pressure. Our core modelling approach showed that the number of O. quadrata burrows was lower after storm waves in urbanized zones, compared to non‐urbanized ones. The interaction between storm waves and urbanization impacted the number of O. quadrata burrows negatively, and suggest that species’ populations are more vulnerable to the combined effects of extreme climatic events and urbanization. Extreme events are predicted to increase in frequency in the next few decades, and may modify or impair ecosystem functioning in sandy beaches by reducing populations of the O. quadrata, an important beach scavenger, which markedly contribute to the flux of energy in coastal trophic webs.

Recovery of ghost crabs metapopulations on urban beaches during the Covid-19 “anthropause”

“…Since 2013, the lower ghost crab abundance in high-impact beach sector compared to low-impact one on Grussaí Beach Arc has been attributed to urbanization and recreational activities ( Suciu et al, 2018 ; Machado et al, 2019 ; Costa and Zalmon, 2019 ). Even though ghost crab larvae potentially settle in the most impacted beach sectors, pulse and press disturbances have hindered metapopulation establishment in urban areas ( Costa and Zalmon, 2019 ; Costa et al, 2020b ; Machado et al, 2019 ).…”

Response of Ocypode quadrata to storm waves on an urbanized sandy beach

“…Regarding our results, during a period of 6 months, the area suffered 5 storm wave events, with two of them occurring sequentially over a 10-day period. These recurrent impacts, coupled with the fragility of the population at an urbanized location (Gül & Griffen, 2019a;Machado et al, 2019), may have triggered a weak but constant Table 1. Mean ± standard deviation of ecological parameters measured before, during and after the storm wave events.…”

“…After this, the distribution was restricted to supralittoral and upper supralittoral in most weeks. Although this could be a consequence of crabs searching for a higher protection from predators (Branco et al, 2010), it is also possible that individuals could have temporarily migrated into dunes and other protected areas of the shore during storm waves (Gül & Griffen, 2019a;Machado et al, 2019). Furthermore, the occurrence of frequent storm waves associated with the anthropogenic impacts characteristic of an urbanized beach such as trampling, could hinder the return of individuals to the area they previously occupied (Machado et al, 2019).…”

“…Although this could be a consequence of crabs searching for a higher protection from predators (Branco et al, 2010), it is also possible that individuals could have temporarily migrated into dunes and other protected areas of the shore during storm waves (Gül & Griffen, 2019a;Machado et al, 2019). Furthermore, the occurrence of frequent storm waves associated with the anthropogenic impacts characteristic of an urbanized beach such as trampling, could hinder the return of individuals to the area they previously occupied (Machado et al, 2019). This was reflected in the distribution of the different age classes, with adults being registered over most of the weeks, opposite of the pattern registered by Gül & Griffen (2019b).…”

Impact of vehicles on benthic macrofauna on a subtropical sand beach

“…Benthic macrofauna have been continually studied because they play a key role in coastal areas and are potentially vulnerable to impact on beaches (McLachlan & Defeo, 2017a, 2017b). Once they generally occupy the sand matrix of the intertidal zone, these organisms are subject to different types of mechanical impacts, such as trampling (Machado, Tavares, & Zalmon, 2019; Suciu, Tavares, & Zalmon, 2018), beach cleaning (Morton, Ward, & Berg, 2015), and also vehicle traffic (Schlacher, Richardson, & McLean, 2008; Schlacher & Thompson, 2007).…”