Effect of Temperature Rising on the Stygobitic Crustacean Species Diacyclops belgicus: Does Global Warming Affect Groundwater Populations?

Abstract

Abstract:The average global temperature is predicted to increase by 3 • C by the end of this century due to human-induced climate change. The overall metabolism of the aquatic biota will be directly affected by rising temperatures and associated changes. Since thermal stability is a characteristic of groundwater ecosystems, global warming is expected to have a profound effect on the groundwater fauna. The prediction that stygobitic (obligate groundwater dweller) species are vulnerable to climate change includes assumptions about metabolic effects that can only be tested by comparisons across a thermal gradient. To this end, we investigated the effects of two different thermal regimes on the metabolism of the stygobitic copepod species Diacyclops belgicus (Kiefer, 1936). We measured the individual-based oxygen consumption of this species as a proxy of possible metabolic reactions to temperature rising from 14 to 17 • C. We used a sealed glass microplate equipped with planar oxygen sensor spots with optical isolation glued onto the bottom of 80-µL wells integrated with a 24-channel fluorescence-based respirometry system. The tests have provided controversial results according to which the D. belgicus populations should be prudently considered at risk under a global warming scenario.

Characteristics, Main Impacts, and Stewardship of Natural and Artificial Freshwater Environments: Consequences for Biodiversity Conservation

“…Together with GW overexploitation for many anthropic uses, climate change can help reduce seasonal water intake in the subsoil and determine an increase in the average temperature, a condition that is reflected not only on the quantitative and chemical-physical status of the GDEs but also on community composition. The effects of temperature increase due to climate change on GW fauna is still a matter of debate, even if recent studies have shown potential metabolic damage [79]. In particular, as regards the effect of climate change on the sensitivity of the invertebrates to agricultural pollutants, several studies [80][81][82] confirmed that an increase in temperature can alter the physiology of invertebrate species that live occasionally or permanently in the hyporheic habitat (for example, doubling the locomotion activity, altering the development time from the larval stages to the adult, increasing oxygen consumption rates, and even inducing death when the critical threshold is reached), increasing their sensitivity to pollutants, especially in those species with limited thermal tolerance (stenotherms) [79].…”

“…The toxicity of ionized ammonium to some GDE invertebrate species increases with temperature. Some other invertebrates are significantly stressed by a temperature increase of less than 3 • C relative to their thermal optimum [79]. For the GDE biota, the consequences of this double twine challenge may get worse than for SW communities.…”

Heat tolerance and acclimation capacity in subterranean arthropods living under common and stable thermal conditions

“…The relatively scarce, more recent studies that have specifically measured thermal breadth and plasticity in subterranean species show contrasting results for different taxa. Some species present the typical characteristics of stenothermal organisms, that is, low physiological plasticity (e.g., Di Lorenzo & Galassi, ) and narrow thermal breadths for survival (e.g., some deep subterranean spiders – Mammola, Piano, Malard, et al, ), locomotion or respiration (e.g., Issartel, Hervant, Voituron, Renault, & Vernon, ; Mermillod‐Blondin et al, ), being sensitive to changes of only a few grades below or above their habitat temperature. In contrast, other subterranean species have shown much wider thermal ranges for performance and survival (Issartel et al, ; Mammola, Piano, Malard, et al, ; Mermillod‐Blondin et al, ).…”

Comparison of some epigean and troglobiotic animals regarding their metabolism intensity. Examination of a classical assertion

“…Oxygen consumption as an estimator of metabolic activity, and the activities of respiratory enzymes are strongly affected by temperature and, therefore, frequently studied in terms of responses to temperature changes in different groups of organisms (e.g., Muskó et al, 1995;Simčič & Brancelj, 1997, 2000Simčič, 2005;Simčič et al, 2014;Žagar et al, 2015). However, studies on the thermal physiology of subterranean invertebrates are scarce (Issartel et al, 2005(Issartel et al, , 2007Mermillod-Blondin et al, 2013;Di Lorenzo & Galassi, 2017). In stable thermal environments, such as subterranean habitats, temperatures may vary a few degrees or even less throughout the year.…”