Posts Tagged 'temperature'

Season affects strength and direction of the interactive impacts of ocean warming and biotic stress in a coastal seaweed ecosystem

The plea for using more “realistic,” community‐level, investigations to assess the ecological impacts of global change has recently intensified. Such experiments are typically more complex, longer, more expensive, and harder to interpret than simple organism‐level benchtop experiments. Are they worth the extra effort? Using outdoor mesocosms, we investigated the effects of ocean warming (OW) and acidification (OA), their combination (OAW), and their natural fluctuations on coastal communities of the western Baltic Sea during all four seasons. These communities are dominated by the perennial and canopy‐forming macrophyte Fucus vesiculosus—an important ecosystem engineer Baltic‐wide. We, additionally, assessed the direct response of organisms to temperature and pH in benchtop experiments, and examined how well organism‐level responses can predict community‐level responses to the dominant driver, OW. OW affected the mesocosm communities substantially stronger than acidification. OW provoked structural and functional shifts in the community that differed in strength and direction among seasons. The organism‐level response to OW matched well the community‐level response of a given species only under warm and cold thermal stress, that is, in summer and winter. In other seasons, shifts in biotic interactions masked the direct OW effects. The combination of direct OW effects and OW‐driven shifts of biotic interactions is likely to jeopardize the future of the habitat‐forming macroalga F. vesiculosus in the Baltic Sea. Furthermore, we conclude that seasonal mesocosm experiments are essential for our understanding of global change impact because they take into account the important fluctuations of abiotic and biotic pressures.

Continue reading ‘Season affects strength and direction of the interactive impacts of ocean warming and biotic stress in a coastal seaweed ecosystem’

Combination of ocean acidification and warming enhances the competitive advantage of Skeletonema costatum over a green tide alga, Ulva linza

Highlights

• Coculture did not affect growth rate of U. linza but decreased it for S. costatum.

• Elevated CO2 relieved the inhibitory effect of U. linza on growth of S. costatum.

• At elevated CO2, higher temperature increased the growth rate of S. costatum.

• At elevated CO2, higher temperature reduced the growth rate of U. linza.

• Coculture did not affect respiration of U. linza but stimulated it for S. costatum.

Abstract

Red tide and green tide are two common algal blooms that frequently occur in many areas in the global oceans. The algae causing red tide and green tide often interact with each other in costal ecosystems. However, little is known on how future CO2-induced ocean acidification combined with temperature variation would affect the interaction of red and green tides. In this study, we cultured the red tide alga Skeletonema costatum and the green tide alga Ulva linza under ambient (400 ppm) and future CO2 (1000 ppm) levels and three temperatures (12, 18, 24 °C) in both monoculture and coculture systems. Coculture did not affect the growth rate of U. linza but significantly decreased it for S. costatum. Elevated CO2 relieved the inhibitory effect of U. linza on the growth of S. costatum, particularly for higher temperatures. At elevated CO2, higher temperature increased the growth rate of S. costatum but reduced it for U. linza. Coculture with U. linza reduced the net photosynthetic rate of S. costatum, which was relieved by elevated CO2. This pattern was also found in Chl a content, indicating that U. linza may inhibit growth of S. costatum via harming pigment synthesis and thus photosynthesis. In monoculture, higher temperature did not affect respiration rate of S. costatum but increased it in U. linza. Coculture did not affect respiration of U. linza but stimulated it for S. costatum, which was a signal of responding to biotic and/abiotic stress. The increased growth of S. costatum at higher temperature and decreased inhibition of U. linza on S. costatum at elevated CO2 suggest that red tides may have more advantages over green tides in future warmer and CO2-enriched oceans.

Continue reading ‘Combination of ocean acidification and warming enhances the competitive advantage of Skeletonema costatum over a green tide alga, Ulva linza’

Investigating the response of sea urchin early developmental stages to multiple stressors related to climate change

Within climate change biology, the red sea urchin Mesocentrotus franciscanus has
remained relatively overlooked despite its sizeable ecological and economic importance, particularly within the context of multi-stressor effects. I assembled and described a developmental transcriptome for M. franciscanus, providing a useful molecular resource with which to study this organism. I then examined both the physiological and molecular mechanisms that underlie the response of early developmental stage (EDS) M. franciscanus to different combinations of pH levels and temperatures that represented ecologically
relevant present and future ocean conditions. Elevated pCO2 levels decreased embryo body size, but at the prism embryo stage, warmer temperatures helped to offset this via an increase in body size. Warmer temperatures also slightly increased the thermal tolerance of prism stage embryos. Neither pCO2 nor temperature stressors affected prism metabolic rate as measured by rate of oxygen consumption. Gene expression patterns differed by developmental stage and by temperature exposure. Elevated temperatures led to an upregulation of cellular stress response genes. Under colder temperatures, the embryos
exhibited an up-regulation of epigenetic genes related to histone modifications.
There was a comparatively minimal transcriptomic response to different pCO2 levels. Examining the physiological and molecular responses of EDS M. franciscanus to multiple stressors provided much needed information regarding a species of significant ecological and economic value by examining its capacity to respond to stressors related to climate change and ocean acidification under an ecologically relevant context.

I also investigated the role of transgenerational plasticity (TGP), in which the
environmental conditions experienced by parents affect progeny phenotypes. TGP may provide a valuable mechanism by which organisms can keep pace with relatively rapid environmental change. Adult S. purpuratus were conditioned to two divergent, but ecologically relevant pH levels and temperatures throughout gametogenesis. The adults were spawned and crossed, and their progeny were raised under different pH levels to determine if maternal conditioning impacted the response of the progeny to low pH stress. I investigated maternal provisioning, a mechanism of TGP, by measuring the size, total protein content, and total lipid content of the eggs that they produced. Acclimatization of the
adult urchins to simulated upwelling conditions (combined low pH, low temperature) appeared to increase maternal provisioning of lipids to the eggs but did not affect egg size or protein content. I also investigated the physiology and gene expression of progeny responding to low pH stress, which were affected more by maternal conditioning than by offspring pH treatment. Maternal conditioning to simulated upwelling resulted in larger offspring body sizes. Additionally, I found the progeny expressed differential regulatory
patterns of genes related to epigenetic modifications, ion transport, metabolic processes and ATP production. This work showed that adult exposure to upwelling conditions can improve the resilience of EDS progeny to low pH levels.

Continue reading ‘Investigating the response of sea urchin early developmental stages to multiple stressors related to climate change’

Impact of ocean acidification and warming on mitochondrial enzymes and membrane lipids in two Gadoid species

Mitochondrial respiration is a multi-step pathway that involves matrix and membrane-associated enzymes and plays a key role in acclimation to variable environmental conditions, but until now it has not been clear which of these steps would be most important in acclimation to changing temperatures and CO2 levels. Considering scenarios of ocean warming and acidification we assessed the role and limitation to phenotypic plasticity in the hearts of two Gadoid species adapted to different thermal ranges: the polar cod (Boreogadus saida), an Arctic stenotherm, and the Northeast Arctic population of Atlantic cod (NEAC, Gadus morhua), a cold eurytherm. We analysed the capacity of single enzymes involved in mitochondrial respiration [citrate synthase (CS), succinate dehydrogenase (SDH), cytochrome c oxidase (CCO)], the capacity of the electron transport system and the lipid class composition of the cellular membranes. Juveniles of the two species were held for four months at four temperatures (0, 3, 6, 8 °C for polar cod and 3, 8, 12, 16 °C for NEAC), at both ambient and elevated PCO2 (400 µatm and 1170 µatm, respectively). Polar cod showed no changes in mitochondrial enzyme capacities and in the relative lipid class composition in response to altered temperature or elevated PCO2. The lack of cardiac cellular plasticity together with evidence at the whole-animal level coming from other studies is indicative of little or no ability to overcome stenothermy, in particular during acclimation to 8 °C. In contrast, eurythermal NEAC exhibited modifications of membrane composition towards a more rigid structure and altered enzyme capacities to preserve functionality at higher temperatures. Furthermore, in NEAC, the capacities of SDH, CCO and CS were increased by high levels of CO2 if combined with high temperatures (12 and 16 °C), suggesting the compensation of an inhibitory effect. These results indicate that the cold eurythermal species (NEAC) is able to alter its mitochondrial function to a far greater extent than the Arctic stenotherm (polar cod), indicating greater resilience to variable environmental conditions. This difference in plasticity may underpin differences in the resilience to climate change and affect future species distributions and, eventually, survival.

Continue reading ‘Impact of ocean acidification and warming on mitochondrial enzymes and membrane lipids in two Gadoid species’

Effects of pH on growth and biochemical responses in Agarophyton vermiculophyllum under different temperature conditions

The effects of pH (6.2, 7.2, 8.2, 9.2, and 10.2) under rising temperature (30 °C vs 20 °C) on Agarophyton vermiculophyllum growth and bio-physiology were investigated. Results showed that A. vermiculophyllum exhibited lower growth rates under elevated temperature in all pH values. Chlorophyll a, carotenoid, and phycocyanin levels were significantly enhanced by temperature elevation (p < 0.05). Enhanced H2O2 production either at lower or higher pH values correlated with lipid peroxidation (LPO) levels under elevated temperature, which suggested oxidative stress development. Oxidative damage was more severe at elevated pH values, which is confirmed by higher reactive oxygen species (ROS) levels. Compared with ambient pH 8.2 value, lower pH values under elevated temperature lead to increase activities of superoxide dismutase (SOD), catalase (CAT), and glutathione S-transferase (GST), indicating that these enzymes played an important role to combat stress. However, decreased glutathione reductase (GR) and glutathione peroxidase (GPx) activities indicate least contribution for ROS scavenging at lower pH values. On contrary, SOD and CAT declined at elevated pH values compared with ambient pH, suggesting least contribution for ROS removal. Moreover, enhanced GR and GPx activities at elevated pH and temperature are not enough to scavenge ROS production. These data are consistent with higher H2O2 and LPO levels, and lower GST activities. Collectively, our results indicated that either pH fluctuations or elevated temperature displayed a disadvantageous influence on growth and bio-physiology of A. vermiculophyllum. Therefore, rising temperature alleviates adverse effects of seawater acidification, but it aggravates the negative effects of seawater alkalization on growth and bio-physiology of A. vermiculophyllum.

Continue reading ‘Effects of pH on growth and biochemical responses in Agarophyton vermiculophyllum under different temperature conditions’

Cloning and characterization of a novel Lustrin A gene from Haliotis discus hannai

Highlights

• The cysteine-rich and proline-rich domains in Lustrin A can be grouped into structural repetitive unit.

• Components of structural repetitive unit reflect the evolutionary distance.

• The expression of Lustrin A is associated with shell regeneration and innate immunity.

• Warming and acidification affected the expression pattern of Lustrin A.

Abstract

Lustrin A is the first nacre protein with specific structure and amino acid residue content that was identified in abalone; since its identification, homologs have been found in several abalone species. In this study, we isolated and cloned the complete cDNA of Lustrin A from Haliotis discus hannai, which was named Hdh-Lustrin A. Hdh-Lustrin A has characteristic cysteine- and proline-rich domains, glycine- and serine-rich domains, and a whey acidic protein (WAP)-like C-terminus. The cysteine- and proline-rich domains showed internal similarity repeats that arrayed in gene coding region, and the phylogenetic tree of these repeats indicated that the similarity of structural repetitive unit components in different abalone species, reflecting their evolutionary distance. A tissue distribution analysis showed that the mRNA level of Hdh-Lustrin A has tissue-specific expression in mantle. Under lipopolysaccharide (LPS) challenge, Hdh-Lustrin A showed a significantly increase, while it showed a more complex pattern with two peaks in the process of shell regeneration. Moreover, acidification and warming raised the expression level of Hdh-Lustrin A in shell regeneration in two different manners; acidification raised the gene expression in quick response, in contrast the long run in warming treatment. Similar pattern also has been detected in immune reaction and the thermal treatments. These results suggest that the Hdh-Lustrin A is a nacre protein, which can be distinguished by its cysteine- and proline-rich domain. It involves in shell regeneration and innate immunity in abalone, and its expression pattern during shell regeneration can be disrupted by physicochemical properties of the environment.

Continue reading ‘Cloning and characterization of a novel Lustrin A gene from Haliotis discus hannai’

Ecotoxicological responses of a reef calcifier exposed to copper, acidification and warming: a multiple biomarker approach

Highlights

• Copper increased bleaching, respiration and inhibited calcification-related enzymes.

• Thermal stress was the main driver of mortality.

• Relative tolerance to climate change scenario (ocean warming + acidification).

• Integrated biomarker response related more to co-exposures than isolated biomarkers.

• Integrated analysis showed higher stress under climate change + copper condition.

Abstract

Multiple global and local stressors threat coral reefs worldwide, and symbiont-bearing foraminifera are bioindicators of reef health. The aim of this study was to investigate single and combined effects of copper (Cu) and climate change related stressors (ocean acidification and warming) on a symbiont-bearing foraminifer by means of an integrated biomarker analysis. Using a mesocosm approach, Amphistegina gibbosa were exposed for 25 days to acidification, warming and/or Cu contamination on a full orthogonal design (two levels each factor). Cu was the main factor increasing bleaching and respiration rates. Warming was the main cause of mortality and reduced growth. Calcification related enzymes were inhibited in response to Cu exposure and, in general, the inhibition was stronger under climate change. Multiple biological endpoints responded to realistic exposure scenarios in different ways, but evidenced general stress posed by climate change combined with Cu. These biological responses drove the high values found for the ‘stress index’ IBR (Integrated Biomarker Response) – indicating general organismal health impairment under the multiple stressor scenario. Our results provide insights for coral reef management by detecting potential monitoring tools. The ecotoxicological responses indicated that Cu reduces the tolerance of foraminifera to climate change (acidification + warming). Once the endpoints analysed have a high ecological relevance, and that responses were evaluated on a classical reef bioindicator species, these results highlight the high risk of climate change and metal pollution co-exposure to coral reefs. Integrated responses allowed a better effects comprehension and are pointed as a promising tool to monitor pollution effects on a changing ocean.

Continue reading ‘Ecotoxicological responses of a reef calcifier exposed to copper, acidification and warming: a multiple biomarker approach’


Subscribe to the RSS feed

Powered by FeedBurner

Follow AnneMarin on Twitter

Blog Stats

  • 1,300,210 hits

OA-ICC HIGHLIGHTS

Ocean acidification in the IPCC AR5 WG II

OUP book