Abstract
Oxygen availability, together with water temperature, greatly varies in coastal habitats, especially in those characterized by elevated primary production. In this study, we investigate the combined role of dissolved oxygen and temperature on the thermal physiological response of the mud crab Thalamita crenata living in an equatorial system of coastal habitats. We sampled temperature, oxygen and salinity in T. crenata habitats, mangrove creeks and fringes and seagrass meadows, at Gazi Bay (Kenya). We found that seagrass meadows exhibited higher temperature and oxygen saturation than the mangrove habitats during the day, creating conditions of oxygen supersaturation. By investigating the effect of different levels of oxygen saturation on the thermal response of T. crenata, we demonstrated that the respiratory physiology of this ectotherm has a pronounced resistance to heat, directly influenced by the amount of dissolved oxygen in the water. Under low oxygen saturation levels, the mud crab significantly reduced its metabolism, becoming temperature-independent. This result shows that aquatic species can modulate their thermal response in a stringent dependency with water oxygen saturation, corroborating previous findings on the thermal response of T. crenata under supersaturation. This contribution provides further support for the need to adopt an ecologically-relevant approach to forecast the effect of climate change on marine ectothermal species.
Highlights
Temperature-driven community changes in the ocean occur as a result of the effect of global warming on the physiological tolerance and performance of marine species (Antão et al, 2020)
Coastal organisms evolved under highly variable oxygen saturation and temperature conditions, such as those occurring in seagrass meadows, coral reefs, seaweed prairies, and/or highly productive microbial mats associated with mangroves (Dubuc et al, 2019; Giomi et al, 2019)
Salinity was significantly different among the three sites at low tide, with the mangrove creek showing an average salinity of 32.1 ± 0.6 ppt increasing to ± 0.6 ppt in the fringe and up to ± 0.1 ppt in the seagrasses meadows (Anova, F2,32 = 4.626; p < 0.05; Figure 2A)
Summary
Temperature-driven community changes in the ocean occur as a result of the effect of global warming on the physiological tolerance and performance of marine species (Antão et al, 2020). These changes may be exacerbated by the predicted progressive oxygen loss in seawater caused by increasing water temperature and from the accumulation and retention of heat in seawater masses (Breitburg et al, 2018). At a fine spatial scale, highly productive coastal habitats undergo acute fluctuations of dissolved. Coastal ecosystems are often characterized by mosaics of habitats where acute environmental fluctuations are important drivers of the tolerance and adaptability of aquatic fauna. Coastal organisms evolved under highly variable oxygen saturation and temperature conditions, such as those occurring in seagrass meadows, coral reefs, seaweed prairies, and/or highly productive microbial mats associated with mangroves (Dubuc et al, 2019; Giomi et al, 2019)
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