Abstract. Dissolution of anthropogenic CO2 is chronically
acidifying aquatic ecosystems. Studies indicate that ocean acidification
will cause marine life, especially calcifying species, to suffer at the
organism and ecosystem levels. In comparison, freshwater acidification has
received less attention, rendering its consequences unclear. Here, juvenile
Chinese mitten crabs, Eriocheir sinensis, were used as a crustacean model to investigate the
impact of CO2-mediated freshwater acidification. Our integrative
approach, investigating changes in the animal's acid–base homeostasis,
metabolism, calcification, locomotory behaviour, and survival rate,
indicates that this economically relevant crustacean will face energetic
consequences from future freshwater acidification. These energetic
trade-offs allow the animal to maintain its acid–base homeostasis at the
cost of reduced metabolic activity, exoskeletal calcification, and
locomotion, reducing the animal's overall fitness and increasing its
mortality. Results indicate that present-day Chinese mitten crab could be
heavily affected by freshwater acidification like their marine counterparts
and emphasize the importance of understanding the long-term implications of
freshwater acidification on species' fitness.
Abstract. Dissolution of anthropogenic CO2 is chronically acidifying aquatic ecosystems. Studies indicate that ocean acidification will cause marine life, especially calcifying species, to suffer at the organismal and ecosystem levels. In comparison, freshwater acidification has received less attention rendering its consequences unclear. Here, juvenile Chinese mitten crabs, Eriocheir sinensis, were used as a calcifying model to investigate the impacts of CO2-mediated freshwater acidification. Our integrative approach investigating changes in the animal's acid-base homeostasis, metabolism, calcification, locomotory behaviour, and survival rate indicate that the crab will face energetic consequences from future freshwater acidification. These energetic trade-offs allow the animal to maintain its acid-base homeostasis at the cost of reduced metabolic activity, exoskeletal calcification, and locomotion reducing the animal's overall fitness and increasing its mortality. Results suggest that present-day calcifying invertebrates could be heavily affected by freshwater acidification similar to their marine organisms and emphasizes the importance in understanding the long-term implications of freshwater acidification on species fitness.
Cephalopods are ancient mollusks that can be found in many different ecological niches in the ocean ranging from the intertidal zone to the deep-sea abyss. In order to adapt to a lifestyle in various habitats, cephalopods have evolved a variety of locomotory modes to accommodate their respective habitats. Most cephalopods have relatively high metabolic rates due to their less efficient swimming mode by jet propulsion. This lifestyle is characterized by a high level of energy expenditure, fueled exclusively by protein diets that are rapidly digested and may produce metabolic nitrogenous waste NH3/NH4 +accumulation and acid-base disturbances. This study observed that the NH4 +transport rate in pelagic bigfin reef squid (Sepioteuthis lessoniana) is two times faster than benthic common octopus (Octopus vulgaris). Inhibition of Na+/H+ exchangers (NHEs) showed significant disruption of NH4 + and H+ excretory processes in gills of octopus but not in squid. However, inhibition of vacuolar-type H+-ATPase (VHA) significantly disrupts NH4 + and H+ transport rates in gills of both animals. Accordingly, for NH4 + and H+ homeostasis, benthic octopus with lower aerobic respiration rates utilize both active and Na+-driven secondary transport machinery. In order to avoid NH4 + accumulated in the blood, pelagic squids with higher aerobic respiration rates prefer active NH4 + and H+ transport mechanisms that consume ATP intensively.
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