Abstract
Barnacles are less common in rock pools of the rocky intertidal zone than on open rock surfaces adjacent to those pools. Rock pools on the Andaman coastlines of Thailand showed diurnal variations in water temperature, salinity, pH, and dissolved oxygen level, peaking in the afternoon. Multivariate analysis showed that water temperature and salinity (not pH and dissolved oxygen) can affect barnacle abundance in rock pools. The present study tests the hypothesis that a lack of recruitment or pool environmental conditions (continuous submergence, water temperature, and salinity extremes) affect the abundance of barnacles (Chthamalus malayensis and Amphibalanus amphitrite) in rock pools. During the recruitment season, recruits were found in a number of rock pools, but at significantly lower abundances than those in adjacent open rock surfaces. In a laboratory experiment, C. malayensis and A. amphitrite that were continuously submerged had a lower survival (80%) than the controls (simulated tide conditions; >90% survivals). Under different water temperature and salinities treatments, barnacles had low survival (<50%) in the low salinity (0‰) and high temperature treatment (40°C). The present study suggests that C. malayensis and A. amphitrite can recruit into rock pools, and the interplay of continuous submergence, high water temperature and low salinity in rock pools can bring about mortality in barnacles.
Highlights
The factors affecting species distribution constitute an interesting topic in ecological studies
A total of 76 rock pools was measured for surface area, depth, water temperature, salinity, pH and dissolved oxygen, and the corresponding abundances of C. malayensis and A. amphitrite
Salinity ranged from ∼5–46◦/oo, pH ranged from ∼6–9.7 and dissolved oxygen concentration ranged from ∼0.9–11 mg L−1 (Figure 2 and Table 1)
Summary
The factors affecting species distribution constitute an interesting topic in ecological studies. The rocky intertidal zone can comprise a variety of microhabitats, including vertical rocks, horizontal rocks, shaded and exposed surfaces, rock pools, and crevices (Williams and Morritt, 1995; Seabra et al, 2011) These microhabitats differ mainly in their levels of heat stress, which affect species distribution (Williams and Morritt, 1995; Wang et al, 2020). The physico-chemical environment of rock pools, comprising water temperature, salinity, pH, and dissolved oxygen levels, is largely regulated by the tides (Metaxas and Scheibling, 1993; Chan, 2000; Legrand et al, 2018) This environment varies with the volume, surface area, depth, and tidal position (intertidal vs supratidal) of pools (Metaxas and Scheibling, 1993; Chan, 2000). Ascidians, hydroids, and gobies are often found in intertidal pools (Evans et al, 2016)
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