Manipulating thermal stress on rocky shores to predict patterns of recruitment of marine invertebrates under a changing climate

Abstract

For rocky intertidal organisms, temperature is often considered the most influential factor governing early survival and growth. Nevertheless, our review of the literature revealed that few studies have manipulated temperatures in the field to test for effects on these critical early life history processes. Here, we present the results from a novel manipulation of substratum temperature using settlement plates of different colour (black, grey and white) and infrared measurements of temperature to test hypotheses that temperature influences the early survival and growth of recent settlers of the intertidal barnacle Tesseropora rosea. Mean surface temperatures of black and grey plates were as great as 5.8°C (on average 2.2°C) and 4.8°C (on average 1.6°C) hotter than white plates across the sampling period, respectively. Cooler, white plates had significantly greater settlement and early growth than hotter, black plates, but differences in plate temperature did not significantly influence early survival or recruitment, though patterns were consistent with thermal variability. Comparisons between grey coloured natural rock and plates indicate that grey plates thermally mimic natural rock. Nevertheless, on average, more than twice as many larvae settled on plates than on natural rock, but early post-settlement survival on natural rock was double that on plates, suggesting that this artificial surface may not adequately capture the natural variability in early life history processes. Regardless, our simple and repeatable thermal manipulation represents a useful tool for experimentally investigating the effects of temperature on recruitment processes and simulating future temperature variability associated with climate change.

Early life-history processes and their implications for the invasion of the barnacle Balanus glandula

“…both barnacles may have wide thermal tolerances), or the temperatures experienced on plates were so stressful that almost all barnacles were severely affected regardless of the treatment. While it is notable that the differences among temperature treatments in the present study are of a similar magnitude as those recorded by a study that detected an effect of temperature on the early life-history characteristics of the barnacle Tesseropora rosea Krauss, 1848 (Lathlean & Minchinton 2012), in the latter study temperatures sometimes exceeded 30°C, with maximum temperatures on grey and black plates exceeding 32°C. This is in contrast to the work presented here, during which it is unlikely that treatments reached such high temperatures as the study took place in spring of a year when air temperatures above 22°C were rare This suggests that the temperatures induced may not have acutely, thermally challenged the barnacles, despite chronically exposing them to different temperatures.…”

“…Following Lathlean & Minchinton (2012), at each site four treatments were used to manipulate rock temperature. Black, grey, white and clear granulated non-slip HW Aquac tape was secured onto clear PVC plates of 0.5mm thickness using clear marine glue.…”

Intertidal community responses to field‐based experimental warming

“…Chthamalus dalli cirri (feeding apparatus) beating reaches maximum levels at 28°C and ceases at 35°C in water (Southward and Southward ). In Australia, barnacle settlement and growth were inhibited when the substratum was warmed 2.2°C (Lathlean and Minchinton ), confirming that Australian barnacles are sensitive to slight increases in substratum temperature. Subsequent work in this system will elucidate the mechanisms controlling Pacific barnacle demographic responses to warming (Kordas and Harley unpubl.…”

Benthic assemblages associated with native and non-native oysters are similar

“…The use of experimental plates, rather than manipulating oyster abundance directly on bedrock, was unavoidable for sampling thus, care should be taken when interpreting results according to general methodological caveats (Kennelly, 1983;Lathlean and Minchinton, 2012;Nozawa et al, 2011). Although we did not have plates without any oysters attached to compare to natural rock we can compare directly for effects of experimental treatments within similar experimental conditions.…”