Biology subjects

Engelhard, G. H.

Publications and source records attributed to Engelhard, G. H..

3 recordsLinked to original sources

bioRxiv2021

Rapid blood acid-base regulation by European sea bass (Dicentrarchus labrax) in response to sudden exposure to high environmental CO2

Fish in coastal ecosystems can be exposed to acute variations in CO2 that can approach 1 kPa CO2 (10,000 atm). Coping with this environmental challenge will depend on the ability to rapidly compensate the internal acid-base disturbance caused by sudden exposure to high environmental CO2 (blood and tissue acidosis); however, studies about the speed of acid-base regulatory responses in marine fish are scarce. We observed that upon exposure to ~1 kPa CO2, European sea bass (Dicentrarchus labrax) completely regulate erythrocyte intracellular pH within ~40 minutes, thus restoring haemoglobin-O2 affinity to pre-exposure levels. Moreover, blood pH returned to normal levels within ~2 hours, which is one of the fastest acid-base recoveries documented in any fish. This was achieved via a large upregulation of net acid excretion and accumulation of HCO3- in blood, which increased from ~4 to ~22 mM. While the abundance and intracellular localisation of gill Na+/K+-ATPase (NKA) and Na+/H+ exchanger 3 (NHE3) remained unchanged, the apical surface area of acid-excreting gill ionocytes doubled. This constitutes a novel mechanism for rapidly increasing acid excretion during sudden blood acidosis. Rapid acid-base regulation was completely prevented when the same high CO2 exposure occurred in seawater with experimentally reduced HCO3- and pH, likely because reduced environmental pH inhibited gill H+ excretion via NHE3. The rapid and robust acid-base regulatory responses identified will enable European sea bass to maintain physiological performance during large and sudden CO2 fluctuations that naturally occur in coastal environments. Summary statementEuropean sea bass exposed to 1 kPa (10,000 atm) CO2 regulate blood and red cell pH within 2 hours and 40 minutes, respectively, protecting O2 transport capacity, via enhanced gill acid excretion.

physiology↗

bioRxiv2021

Temperature and O2, but not CO2, interact to affect aerobic performance of European sea bass (Dicentrarchus labrax)

Climate change causes warming, decreased O2, and increased CO2 in marine systems and responses of organisms will depend on interactive effects between these factors. We provide the first experimental assessment of the interactive effects of warming (14 to 22{degrees}C), reduced O2 ([~]3 - 21 kPa O2), and increased CO2 ([~]400 or [~]1000 {micro}atm ambient CO2) on four indicators of aerobic performance (standard metabolic rate, SMR, maximum metabolic rate, MMR, aerobic scope, and hypoxia tolerance, O2crit), blood chemistry, and O2 transport (P50) of a marine fish, the European sea bass (Dicentrarchus labrax). Warming increased SMR and O2crit (i.e. reduced hypoxia tolerance) as well as MMR in normoxia but there was an interactive effect with O2 so that hypoxia caused larger reductions in MMR and aerobic scope at higher temperatures. Increasing CO2 had minimal effects on SMR, MMR and O2crit and did not show interactive effects with temperature or O2 for any measured variables. Aerobic performance was not linked to changes in blood chemistry or P50. Despite lack of effects of CO2 on aerobic performance, increased CO2 induced 30% mortality of fish exercised in low O2 at 22{degrees}C indicating important threshold effects independent of aerobic performance. Overall, our results show temperature and O2, but not CO2, interact to affect aerobic performance of sea bass, disagreeing with predictions of the oxygen- and capacity-limited thermal tolerance hypothesis.

ecology↗

bioRxiv2020

Climate-risk to European fisheries and coastal communities

With the majority of the global human population living in coastal regions, correctly characterising the climate risk that ocean-dependent communities and businesses are exposed to is key to prioritising the finite resources available to support adaptation. We apply a climate risk analysis across the European fisheries sector for the first time to identify the most at-risk fishing fleets and coastal regions and then link the two analyses together. We employ a novel approach combining biological traits with physiological metrics to differentiate climate hazards between 556 populations of fish and use these to assess the relative climate risk for 380 fishing fleets and 105 coastal regions in Europe. Countries in southeast Europe as well as the UK have the highest risks to both fishing fleets and coastal regions overall while, in other countries, the risk-profile is greater at either the fleet level or at the regional level. European fisheries face a diversity of challenges posed by climate change and climate adaptation, therefore, needs to be tailored to each country, region and fleets specific situation. Our analysis supports this process by highlighting where and what adaptation measures might be needed and informing where policy and business responses could have the greatest impact. Significance StatementWe present a novel climate risk analysis for i) 105 ocean-dependent communities and ii) 380 fishing fleets in Europe. Our unique approach provides a perspective over the climate risks in this diverse and populous continent that is unprecedented in both its breadth and detail. We show that countries in southeast Europe as well as the UK have the highest climate risk overall, both in terms of fishing fleets and coastal communities. Substantial variation in climate risk is seen even within countries, emphasizing that climate adaptation interventions need to be tailored to the specific characteristics of the fleet or community. A focus on sustainable fisheries management and diversification of fish portfolios can reduce climate risks across the board.

ecology↗