title: Effects of seawater alkalinity on calcium and acid-base regulation in juvenile European lobster (Homarus gammarus) during a moult cycle.
abstract: Fluxes of NH4(+) (acid) and HCO3(-) (base), and whole body calcium content were measured in European lobster (Homarus gammarus) during intermoult (megalopae stage), and during the first 24h for postmoult juveniles under control (~2000 μeq/L) and low seawater alkalinity (~830 μeq/L). Immediately after moulting, animals lost 45% of the total body calcium via the shed exoskeleton (exuvia), and only 11% was retained in the uncalcified body. At 24h postmoult, exoskeleton calcium increased to ~46% of the intermoult stage. Ammonia excretion was not affected by seawater alkalinity. After moulting, bicarbonate excretion was immediately reversed from excretion to uptake (~4-6 fold higher rates than intermoult) over the whole 24h postmoult period, peaking at 3-6h. These data suggest that exoskeleton calcification is not completed by 24h postmoult. Low seawater alkalinity reduced postmoult bicarbonate uptake by 29% on average. Net acid-base flux (equivalent to net base uptake) followed the same pattern as HCO3(-) fluxes, and was 22% lower in low alkalinity seawater over the whole 24h postmoult period. The common occurrence of low alkalinity in intensive aquaculture systems may slow postmoult calcification in juvenile H. gammarus, increasing the risk of mortalities through cannibalism.
authors.affiliation: Biosciences, College of Life and Environmental Sciences, Geoffrey Pope Building, University of Exeter, Stocker Road, Exeter EX4 4QD, UK. Electronic address: kombi@xtra.co.nz.
authors.forename: Karen L
authors.initials: KL
authors.lastname: Middlemiss
authors.affiliation: Biosciences, College of Life and Environmental Sciences, Geoffrey Pope Building, University of Exeter, Stocker Road, Exeter EX4 4QD, UK; Departamento de Zoología, Facultad de Ciencias Naturales y Oceanográficas, Universidad de Concepción, Casilla 160-C, Concepción, Chile. Electronic address: mauriciourbina@udec.cl.
authors.forename: Mauricio A
authors.initials: MA
authors.lastname: Urbina
authors.affiliation: Biosciences, College of Life and Environmental Sciences, Geoffrey Pope Building, University of Exeter, Stocker Road, Exeter EX4 4QD, UK. Electronic address: r.w.wilson@exeter.ac.uk.
authors.forename: Rod W
authors.initials: RW
authors.lastname: Wilson
mesh_terms: D000136:Acid-Base Equilibrium / Q000502:physiology*; D000468:Alkalies / Q000378:metabolism*; D000641:Ammonia / Q000378:metabolism; D000818:Animals; D001639:Bicarbonates / Q000378:metabolism; D002118:Calcium / Q000378:metabolism*; D018978:Molting / Q000502:physiology*; D008121:Nephropidae / Q000378:metabolism* / Q000502:physiology*; D012623:Seawater
chemical_list: D000468:Alkalies; D001639:Bicarbonates; D000641:Ammonia; D002118:Calcium
keywords: Ammonia excretion; Bicarbonate excretion; Calcification; Carbonate; Crustacean; Exuvia; Moult cycle