Hot Rocks and Not-So-Hot Rocks on the Seashore: Patterns and Body-Size Dependent Consequences of Microclimatic Variation in Intertidal Zone Boulder Habitat

Abstract

Synopsis Microclimatic variation has emerged as an important driver of many ecological and evolutionary processes. Nonetheless, fine-scale temperature data are still rare in most habitats, limiting our ability to understand the consequences of microclimatic variation under current and future conditions. We measured fine-scale thermal variation in a common, species-rich, but rarely studied habitat with respect to temperature: the airspaces under rocks on intertidal zone boulder shores. The effects of thermal variation were investigated using physiological, behavioral, and demographic responses of the porcelain crab Petrolisthes cinctipes. Habitat temperatures were measured at fine spatial and temporal resolution over 18 months, producing 424,426 temperature records. Microclimatic variation increased with increasing intertidal elevation, particularly with respect to heat extremes. However, mean temperatures were similar across the entire intertidal zone. Overheating risk for P. cinctipes increases with intertidal elevation but is size dependent, as large animals are more heat sensitive than small animals. Still, microclimatic variation high in the intertidal zone provided thermal refugia even under the warmest conditions. Size-dependent thermal responses predicted that large crabs should be rare high in the intertidal zone, which was supported by demographic data. Furthermore, simulations parameterized by our microclimate and organismal data recapitulated demographic patterns. Therefore, interactions between microclimatic variation and size-dependent thermal responses may have significant ecological repercussions that warrant greater attention.

Rocks of different mineralogy show different temperature characteristics: implications for biodiversity on rocky seashores

“…In this study, a temperature range as large as 16.3 • C was recorded across an individual boulder surface. This temperature range is larger than the 5.0 • C (Leal et al, 2020) or 8.2 • C (Lathlean, Ayre & Minchinton, 2012) maximum ranges recorded among replicate quadrats sampled on the same rock platforms, but considerably smaller than the 24.0 • C maximum range detected between between the edge and centre of rocks (maximum length <2 m) sheltering garter snakes (Huey et al, 1989), the 25 • C maximum range detected between replicate boulders sampled on the same seashore (Gunderson et al, 2019), or the 25.5 • C maximum range detected between different seashore microhabitats (Chapperon & Seuront, 2011;Chapperon, Studerus & Clavier, 2017). Consequently, these new results for single boulder surfaces indicate that temperature range is likely be specific to the type(s) of substrate, habitat and region investigated.…”

“…With predictions of hotter air temperatures and an increased frequency of extreme-heat events associated with global climate change ( IPCC, 2013 ), the survival and persistence of some intertidal species is likely to be challenged further. To predict the future fate of species and populations, ecologists have collected baseline rock temperature data ( Helmuth, 1999 ; Denny et al, 2011 ; Judge, Botton & Hamilton, 2011 ; Gunderson et al, 2019 ), created heat budget models ( Helmuth, 1999 ; Choi et al, 2019 ), investigated how x species is affected by y substrate temperature ( Raimondi, 1988 ; Lathlean, Ayre & Minchinton, 2012 ; Lathlean, Ayre & Minchinton, 2013 ; Lamb, Leslie & Shinen, 2014 ), or used biomimetic loggers to investigate how internal body temperatures can be variously affected by environmental temperature ( Helmuth & Hofmann, 2001 ; Seabra et al, 2011 ; Lathlean et al, 2015 ; Seuront et al, 2019 ). All of these studies confirm that temperature is an important driving force that can influence the distribution of species on rocky seashores.…”

“…Comparing across studies that investigate substratum temperature, a number of rock temperature observations have been made. Rock temperature is affected by its colour ( Raimondi, 1988 ; Judge, Botton & Hamilton, 2011 ; Gunderson et al, 2019 ), size and orientation relative to the sun ( Bertness, 1999 ; Chapperon et al, 2016 ; Chapperon, Studerus & Clavier, 2017 ). Marshall, McQuaid & Williams (2010) reported lighter-coloured sandstone was cooler than darker-coloured ferruginous sandstone.…”

“…Studies investigating intertidal rock temperature have also shown that observed substratum temperature is not homogenous (e.g., Huey et al, 1989 ; Gómez-Heras, Smith & Fort, 2006 ; Helmuth et al, 2006 ; Lathlean, Ayre & Minchinton, 2012 ; Gunderson et al, 2019 ; Leal et al, 2020 ). Instead, substratum temperature is heterogeneous, with temperature differences up to 25.5 °C identified between the hottest and coolest locations (e.g., Huey et al, 1989 ; Denny et al, 2011 ; Lathlean, Ayre & Minchinton, 2012 ; Gunderson et al, 2019 ; Leal et al, 2020 ). The scale of these patterns of temperature difference can vary enormously, from many kilometres down to millimetres ( Helmuth et al, 2006 ; Denny et al, 2011 ; Judge, Botton & Hamilton, 2011 ; Lathlean, Ayre & Minchinton, 2012 ; Lathlean, Ayre & Minchinton, 2013 ).…”

Effects of Intertidal Position on Metabolism and Behavior in the Acorn Barnacle,Balanus glandula

“…There is also a small body of evidence for variation in metabolic physiology between species that inhabit discrete vertical zones (e.g., porcelain crabs ( Stillman and Somero 1996 ; Gunderson et al 2019 ) and acorn barnacles ( Augenfeld 1967 ; Vial et al 1999 )). Stillman and Somero (1996) observed significant differences in resting metabolic rates, cardiac parameters, and aerial lactate production between closely related species of porcelain crabs characteristic of different tidal heights.…”