Adaptation and acclimatization to ocean acidification in marine ectotherms: an in situ transplant experiment with polychaetes at a shallow CO₂ vent system

Metabolic rate determines the physiological and life-history performances of ectotherms. Thus, the extent to which such rates are sensitive and plastic to environmental perturbation is central to an organism's ability to function in a changing environment. Little is known of long-term metabolic plasticity and potential for metabolic adaptation in marine ectotherms exposed to elevated pCO₂. Consequently, we carried out a series of in situ transplant experiments using a number of tolerant and sensitive polychaete species living around a natural CO₂ vent system. Here, we show that a marine metazoan (i.e. Platynereis dumerilii) was able to adapt to chronic and elevated levels of pCO₂. The vent population of P. dumerilii was physiologically and genetically different from nearby populations that experience low pCO₂, as well as smaller in body size. By contrast, different populations of Amphiglena mediterranea showed marked physiological plasticity indicating that adaptation or acclimatization are both viable strategies for the successful colonization of elevated pCO₂ environments. In addition, sensitive species showed either a reduced or increased metabolism when exposed acutely to elevated pCO₂. Our findings may help explain, from a metabolic perspective, the occurrence of past mass extinction, as well as shed light on alternative pathways of resilience in species facing ongoing ocean acidification

The effects of elevated temperature and PCO2 on the energetics and haemolymph pH homeostasis of juveniles of the European lobster, Homarus gammarus

Regulation of extracellular acid–base balance, while maintaining energy metabolism, is recognised as an important aspect when defining an organism's sensitivity to environmental changes. This study investigated the haemolymph buffering capacity and energy metabolism (oxygen consumption, haemolymph [l-lactate] and [protein]) in early benthic juveniles (carapace length <40 mm) of the European lobster, Homarus gammarus, exposed to elevated temperature and PCO2. At 13°C, H. gammarus juveniles were able to fully compensate for acid–base disturbances caused by the exposure to elevated seawater PCO2 at levels associated with ocean acidification and carbon dioxide capture and storage (CCS) leakage scenarios, via haemolymph [HCO3−] regulation. However, metabolic rate remained constant and food consumption decreased under elevated PCO2, indicating reduced energy availability. Juveniles at 17°C showed no ability to actively compensate haemolymph pH, resulting in decreased haemolymph pH particularly under CCS conditions. Early benthic juvenile lobsters at 17°C were not able to increase energy intake to offset increased energy demand and therefore appear to be unable to respond to acid–base disturbances due to increased PCO2 at elevated temperature. Analysis of haemolymph metabolites suggests that, even under control conditions, juveniles were energetically limited. They exhibited high haemolymph [l-lactate], indicating recourse to anaerobic metabolism. Low haemolymph [protein] was linked to minimal non-bicarbonate buffering and reduced oxygen transport capacity. We discuss these results in the context of potential impacts of ongoing ocean change and CCS leakage scenarios on the development of juvenile H. gammarus and future lobster populations and stocks. -- Keywords : Developmental physiology ; Ocean acidification ; Ocean warming ; Early benthic juvenile ; Acid–base balance ; Metabolism

Ultrastructural localization of carbonic anhydrase in gastric parietal cells with the immunoglobulin-enzyme bridge method

Ultrastructural immunostaining of carbonic anhydrase in gastric parietal cells was accomplished with the immunoglobulin-peroxidase bridge procedure applied to cryostat sections of fixed guinea-pig stomach prior to dehydration and embedment. Of a variety of fixatives tested, only freshly prepared paraformaldehyde buffered with calcium acetate provided both immunostaining and adequate preservation of ultrastructural morphology. Delipidization or exposure of specimens to detergent prior to staining enhanced the intensity of the immunostaining and increased the sensitivity of the method. Increased diaminobenzidine concentration in the peroxidase substrate appeared also to intensify the densification at the reactive site. Carbonic anhydrase was localized ultrastructurally with this pre-embedment immunobridge procedure in the hyaloplasm of gastric parietal cells and less consistently in the superficial surface epithelium. The basal portion of the parietal cells stained more intensely than the apical region and immunoreactivity appeared concentrated at the plasmalemma and around mitochondria.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/42849/1/10735_2005_Article_BF01012020.pd

Sperm motility and fertilisation success in an acidified and hypoxic environment

The distribution and function of many marine species is largely determined by the effect of abiotic drivers on their reproduction and early development, including those drivers associated with elevated CO2 and global climate change. A number of studies have therefore investigated the effects of elevated pCO2 on a range of reproductive parameters, including sperm motility and fertilisation success. To date, most of these studies have not examined the possible synergistic effects of other abiotic drivers, such as the increased frequency of hypoxic events that are also associated with climate change. The present study is therefore novel in assessing the impact that a hypoxic event could have on reproduction in a future high CO2 ocean. Specifically, this study assesses sperm motility and fertilisation success in the sea urchin Paracentrotus lividus exposed to elevated pCO2 for 6 months. Gametes extracted from these pre acclimated individuals were subjected to hypoxic conditions simulating an hypoxic event in a future high CO2 ocean. Sperm swimming speed increased under elevated pCO2 and decrease under hypoxic conditions resulting in the elevated pCO2 and hypoxic treatment being approximately equivalent to the control. There was also a combined negative effect of increased pCO2 and hypoxia on the percentage of motile sperm. There was a significant negative effect of elevated pCO2 on fertilisation success, and when combined with a simulated hypoxic event there was an even greater effect. This could potentially affect cohort recruitment and in turn reduce the density of this ecologically and economically important ecosystem engineer therefore potentially effecting biodiversity and ecosystem services

Temporal fluctuations in seawater pCO<inf>2</inf> may be as important as mean differences when determining physiological sensitivity in natural systems

Most studies assessing the impactsofocean acidification (OA) onbenthic marine invertebrates have used stable mean pH/pCO2 levelsto highlight variation in the physiological sensitivities in a range of taxa. However, many marine environments experience natural fluctuations in carbonate chemistry, and to date little attempt has been made to understand the effect of naturally fluctuating seawater pCO2 (pCO2sw) on the physiological capacity of organisms to maintain acid-base homeostasis. Here, for the first time, we exposed two species of sea urchin with different acid-base tolerances, Paracentrotus lividus and Arbacia lixula, to naturally fluctuating pCO2sw conditions at shallow water CO2 seep systems (Vulcano, Italy) and assessed their acid-base responses. Both sea urchin species experienced fluctuations in extracellular coelomic fluid pH, pCO2, and [HCO-3] (pHe, pCO2e, and [HCO-3]e, respectively) in line with fluctuations in pCO2sw. The less tolerant species, P. lividus, had the greatest capacity for [HCO-3]e buffering in response to acute pCO2sw fluctuations, but it also experienced greater extracellular hypercapnia and acidification and was thus unabletofully compensate for acid-basedisturbances. Conversely, themore tolerant A.lixula reliedonnon-bicarbonate protein buffering and greater respiratory control. In the light of these findings, we discuss the possible energetic consequences of increased reliance on bicarbonate buffering activity in P. lividus compared with A. lixula and how these differing physiological responses to acute fluctuations in pCO2sw may be as important as chronic responses to mean changes in pCO2sw when considering how CO2 emissions will affect survival and success of marine organisms within naturally assembled systems

The genetic architecture of the human cerebral cortex

The cerebral cortex underlies our complex cognitive capabilities, yet little is known about the specific genetic loci that influence human cortical structure. To identify genetic variants that affect cortical structure, we conducted a genome-wide association meta-analysis of brain magnetic resonance imaging data from 51,665 individuals. We analyzed the surface area and average thickness of the whole cortex and 34 regions with known functional specializations. We identified 199 significant loci and found significant enrichment for loci influencing total surface area within regulatory elements that are active during prenatal cortical development, supporting the radial unit hypothesis. Loci that affect regional surface area cluster near genes in Wnt signaling pathways, which influence progenitor expansion and areal identity. Variation in cortical structure is genetically correlated with cognitive function, Parkinson's disease, insomnia, depression, neuroticism, and attention deficit hyperactivity disorder