Seawater temperature in the microhabitats of intertidal marine invertebrates in Sea Point, 03 January to 11 February 2021

To better understand the physiological effects of marine invertebrates to changing environmental conditions, long-term monitoring which captures the natural variability of environmental parameters is required. In this way, experimental findings can be related back to field conditions, and better predictions can be made as to how marine invertebrates, particularly in the harsh intertidal, will fair with rising temperature. In May 2020, Cape Sea Urchins, Parechinus angulosus, were collected from intertidal rock pools at Sea Point, which is situated along the southwest coast of South Africa. After chronic incubation in low pH conditions at the Department of Forestry, Fisheries and the Environment's (DFFE) Sea Point Research Aquarium, their response to thermal stress was investigated in recent experimental trials. To calculate the thermal window for these marine invertebrates, both habitat temperatures, as well as their threshold temperatures are required. The latter was obtained by examining the Critical Thermal Maximum temperatures (CTmax), i.e. the temperatures at which organisms respond with uncoordinated mobility, whereas habitat temperatures are available through the deployment of temperature loggers in the intertidal pools inhabited by these organisms. Three prominent rockpools were chosen Sea Point, Cape Town (>5 m apart) to install HOBO TidbiT temperature loggers. Two loggers were placed in each pool. Here we present the cleaned up version of temperature measurements from Pool 1: 33.920317 S, 18.379417 E, logger 10687237 and 20195550; Pool 2: 33.920267 S, 18.379417 E, logger 10687240 and 20195554; Pool 3: 33.920167 S, 18.379717 E, logger 20195539 and 20195574, from 03 January to 11 February 2021.