Ecological traps in shallow coastal waters—Potential effect of heat-waves in tropical and temperate organisms

Abstract

Mortality of fish has been reported in tide pools during warm days. That means that tide pools are potential ecological traps for coastal organisms, which happen when environmental changes cause maladaptive habitat selection. Heat-waves are predicted to increase in intensity, duration and frequency, making it relevant to investigate the role of tide pools as traps for coastal organisms. However, heat waves can also lead to acclimatization. If organisms undergo acclimatization prior to being trapped in tide pools, their survival chances may increase. Common tide pool species (46 species in total) were collected at a tropical and a temperate area and their upper thermal limits estimated. They were maintained for 10 days at their mean summer sea surface temperature +3°C, mimicking a heat-wave. Their upper thermal limits were estimated again, after this acclimation period, to calculate each species’ acclimation response. The upper thermal limits of the organisms were compared to the temperatures attained by tide pool waters to investigate if 1) tide pools could be considered ecological traps and 2) if the increase in upper thermal limits elicited by the acclimation period could make the organisms less vulnerable to this threat. Tropical tide pools were found to be ecological traps for an important number of common coastal species, given that they can attain temperatures higher than the upper thermal limits of most of those species. Tide pools are not ecological traps in temperate zones. Tropical species have higher thermal limits than temperate species, but lower acclimation response, that does not allow them to survive the maximum habitat temperature of tropical tide pools. This way, tropical coastal organisms seem to be, not only more vulnerable to climate warming per se, but also to an increase in the ecological trap effect of tide pools.

Thermal response of demersal and pelagic juvenile fishes from the surf zone during a heat‐wave simulation

“…The lower ARR observed for this species reaffirms the trade‐off hypothesis, commonly behold in organisms of tropical regions that present a high thermal tolerance (e.g. Duarte, Tejedo, & Katzenberger, ; Vinagre et al, ; Vinagre et al, ).…”

“…For the first T a , the temperature of 25°C was established considering the mean water temperature in latitude 23°S ‐Santos (SIMCOSTA: average of 2014 and 2015; http://www.simcosta.furg.br; accessed 22 November 2018). For the “heat‐wave experiment”, the T a temperature was 30°C, as it was 5°C above of the local average temperature (+5°C the average maximum heat‐wave being estimated for the period 1961–1990; see: Vinagre et al, ). To achieve and maintaining T a , the water temperature was raised by a heater coupled to a digital thermostat (ATMAN 200‐Electronic Heater–200 W) at 1°C/h from the initial maintenance temperature.…”

“…Prior to transfer to the experimental aquaria, the fish fasted for 24 hr. Given the duration of the experimental procedures and due to logistic restrictions, the trials to determine the critical thermal tolerance to each fish species were conducted separately in a single tank, using an experimental approach that has been widely used to determine thermal tolerance in fishes (for example see: Morita, Fukuwaka, Tanimata, & Yamamura, ; Zhang & Kieffer, 2014; Vinagre et al, ). Care was taken to maintain similar water quality properties between the experimental tanks during the trials, in order to avoid any rearing conditions effect on the thermal tolerance determined to each fish species.…”

“…Climate change has been predicted to drive distinct effects on fish populations between the open ocean, continental shelf and coastal waters (Lehodey et al, ; Walther et al, ). Among these habitats, climate‐warming impacts are more drastic in the shallow coastal waters, where both the lower depths and thermal regime are directly affected by both oceanographic and atmospheric conditions (Vinagre et al, ). Furthermore, the air temperatures increase faster than ocean temperatures (IPCC, ).…”

“…Extreme climate events, such as heat‐waves, can quickly turn shallow coastal waters into thermally unstable environments, making these events ecologically more concerning than those changes in global average temperature (Easterling et al, ; Meehl et al, ; Stenseth et al, ). However, most studies on climate change are focusing on average predicted temperatures for global warming scenario and fail to address the potential impacts of changes in both intensity and temporal occurrence of heat‐waves on living organisms (Sorte, Fuller, & Bracken, ; Vinagre et al, ). Heat‐waves are a result of a very fast variation of air temperature when the daily maximum temperature exceeds the average of maximum current temperature by 5°C for more than five consecutive days (Vinagre et al, ).…”