Tolerance to Copper and to Salinity in Daphnia longispina: Implications within a Climate Change Scenario

Abstract

Considering IPPC climate change scenarios, it is pertinent to predict situations where coastal ecosystems already impacted with chemical contamination became exposed to an additional stressor under a future scenario of seawater intrusion. Accordingly, the present study aimed at evaluating if a negative association between tolerance to a metal and to saltwater exists among genotypes of a freshwater organism. For this, five clonal lineages of the cladoceran Daphnia longispina O.F. Müller, exhibiting a differential tolerance to lethal levels of copper, were selected. Each clonal lineage was exposed to lethal and sublethal concentrations of sodium chloride (assumed as a protective surrogate to evaluate the toxicity of increased salinity to freshwater organisms). Mortality, time to release the first brood and total number of neonates per female were monitored and the somatic growth rate and intrinsic rate of natural increase were computed for each clonal lineage. Data here obtained were compared with their lethal responses to copper and significant negative correlations were found. These results suggest that genetically eroded populations of D. longispina, due to copper or salinity, may be particularly susceptible to a later exposure to the other contaminant supporting the multiple stressors differential tolerance.

Sensitivity of freshwater species under single and multigenerational exposure to seawater intrusion

“…The majority of studies addressing salinity effects on freshwater biota used mostly specific salts (NaCl, MgCl 2 , among others) in monospecific standard toxicity tests [17][18][19][20][21]. It is still unclear whether such surrogate salts may be safely used for the preliminary risk assessment framework of SW intrusion because available literature comparing toxicity data from surrogate salts and toxicity data of SW is still scarce [10,[22][23][24].…”

Progressive acclimation alters interaction between salinity and temperature in experimental Daphnia populations

“…Again, this emphasizes the need to build comprehensive frameworks for the risk assessment of chemicals, including those that may occur naturally or as a consequence of climate change (e.g., salinisation). This includes designing experiments accounting for acclimation (Chen and Stillman, 2012; this study) and adaptation to stress (Lopes et al, 2005;Jansen et al, 2011), interactions between environmental factors and contaminants (Antunes et al, 2004;Tassou and Schulz, 2012), interactions among contaminants (Leitão et al, 2013;Santos et al, 2013), and interactive scenarios with biotic relationships (Loureiro et al, 2013b;Scherer et al, 2013) -see also review by Fischer et al (2013) and the rationale for the multifactorial design of Scherer et al (2013).…”

“…Sodium chloride was used as a protective surrogate of seawater (Leitão et al, 2013;Loureiro et al, 2013a,b), because its toxicity to freshwater organisms is comparable or only slightly higher than equivalent seawater dilutions (ongoing results of project Saltfree). Neonates from the initial culture (see above) were used as propagules (F0 generation) to inoculate each new culture.…”

Feeding inhibition tests as a tool for seston quality evaluation in lentic ecosystems: salinization impact

“…Cladocera is the most important primary group of consumers in lentic ecosystems, and has been widely used to evaluate the impact of environmental changes due to their key position in the trophic web and sensibility at different stressors (Zhang et al 2010;Jeppesen et al 2011;Leitão et al 2013;Loureiro et al 2015;Lari et al 2017;Venâncio et al 2018). Aladin (1991) and Bezirci et al (2012) verified that cladocera organisms presented a high sensitivity to osmotic stress and therefore an ideal bioindicator of saline stress.…”