Posts Tagged 'morphology'

Effects of salinity and pH of seawater on the reproduction of the sea urchin Paracentrotus lividus

Fertilization and early development are usually the most vulnerable stages in the life of marine animals, and the biological processes during this period are highly sensitive to the environment. In nature, sea urchin gametes are shed in seawater, where they undergo external fertilization and embryonic development. In a laboratory, it is possible to follow the exact morphological and biochemical changes taking place in the fertilized eggs and the developing embryos. Thus, observation of successful fertilization and the subsequent embryonic development of sea urchin eggs can be used as a convenient biosensor to assess the quality of the marine environment. In this paper, we have examined how salinity and pH changes affect the normal fertilization process and the following development of Paracentrotus lividus. The results of our studies using confocal microscopy, scanning and transmission electron microscopy, and time-lapse Ca2+ image recording indicated that both dilution and acidification of seawater have subtle but detrimental effects on many aspects of the fertilization process. They include Ca2+ signaling and coordinated actin cytoskeletal changes, leading to a significantly reduced rate of successful fertilization and, eventually, to abnormal or delayed embryonic development.

Continue reading ‘Effects of salinity and pH of seawater on the reproduction of the sea urchin Paracentrotus lividus’

The role of aspartic acid in reducing coral calcification under ocean acidification conditions

Biomolecules play key roles in regulating the precipitation of CaCO3 biominerals but their response to ocean acidification is poorly understood. We analysed the skeletal intracrystalline amino acids of massive, tropical Porites spp. corals cultured over different seawater pCO2. We find that concentrations of total amino acids, aspartic acid/asparagine (Asx), glutamic acid/glutamine and alanine are positively correlated with seawater pCO2 and inversely correlated with seawater pH. Almost all variance in calcification rates between corals can be explained by changes in the skeletal total amino acid, Asx, serine and alanine concentrations combined with the calcification media pH (a likely indicator of the dissolved inorganic carbon available to support calcification). We show that aspartic acid inhibits aragonite precipitation from seawater in vitro, at the pH, saturation state and approximate aspartic acid concentrations inferred to occur at the coral calcification site. Reducing seawater saturation state and increasing [aspartic acid], as occurs in some corals at high pCO2, both serve to increase the degree of inhibition, indicating that biomolecules may contribute to reduced coral calcification rates under ocean acidification.

Continue reading ‘The role of aspartic acid in reducing coral calcification under ocean acidification conditions’

Coccolithophore community response to ocean acidification and warming in the Eastern Mediterranean Sea: results from a mesocosm experiment

Mesocosm experiments have been fundamental to investigate the effects of elevated CO2 and ocean acidification (OA) on planktic communities. However, few of these experiments have been conducted using naturally nutrient-limited waters and/or considering the combined effects of OA and ocean warming (OW). Coccolithophores are a group of calcifying phytoplankton that can reach high abundances in the Mediterranean Sea, and whose responses to OA are modulated by temperature and nutrients. We present the results of the first land-based mesocosm experiment testing the effects of combined OA and OW on an oligotrophic Eastern Mediterranean coccolithophore community. Coccolithophore cell abundance drastically decreased under OW and combined OA and OW (greenhouse, GH) conditions. Emiliania huxleyi calcite mass decreased consistently only in the GH treatment; moreover, anomalous calcifications (i.e. coccolith malformations) were particularly common in the perturbed treatments, especially under OA. Overall, these data suggest that the projected increase in sea surface temperatures, including marine heatwaves, will cause rapid changes in Eastern Mediterranean coccolithophore communities, and that these effects will be exacerbated by OA.

Continue reading ‘Coccolithophore community response to ocean acidification and warming in the Eastern Mediterranean Sea: results from a mesocosm experiment’

Elevated temperature and CO2 have positive effects on the growth and survival of larval Australasian snapper

Highlights

• Larval Snapper were positively affected by projected end of century temperature and pCO2 from fertilization to 16 days post-hatching.

• Elevated temperature increased the size of larvae, however high pCO2 had no effect.

• High pCO2 significantly increased survival at 16 days post-hatch, but elevated temperature had no effect.

• Some species and populations of marine fish exhibit positive effects from projected environmental change.

Abstract

Rising water temperature and increased uptake of CO2 by the ocean are predicted to have widespread impacts on marine species. However, the effects are likely to vary, depending on a species’ sensitivity and the geographical location of the population. Here, we investigated the potential effects of elevated temperature and pCO2 on larval growth and survival in a New Zealand population of the Australasian snapper, Chrysophyrs auratus. Eggs and larvae were reared in a fully cross-factored experiment (18 °C and 22 °C/pCO2 440 and 1040 μatm) to 16 days post hatch (dph). Morphologies at 1 dph and 16 dph were significantly affected by temperature, but not CO2. At 1dph, larvae at 22 °C were longer (7%) and had larger muscle depth at vent (14%), but had reduced yolk (65%) and oil globule size (16%). Reduced yolk reserves in recently hatched larvae suggests higher metabolic demands in warmer water. At 16 dph, larvae at elevated temperature were longer (12%) and muscle depth at vent was larger (64%). Conversely, survival was primarily affected by CO2 rather than temperature. Survivorship at 1 dph and 16 dph was 24% and 54% higher, respectively, under elevated CO2 compared with ambient conditions. Elevated temperature increased survival (24%) at 1 dph, but not at 16 dph. These results suggest that projected climate change scenarios may have an overall positive effect on early life history growth and survival in this population of C. auratus. This could benefit recruitment success, but needs to be weighed against negative effects of elevated CO2 on metabolic rates and swimming performance observed in other studies on the same population.

Continue reading ‘Elevated temperature and CO2 have positive effects on the growth and survival of larval Australasian snapper’

An uncertain future: effects of ocean acidification and elevated temperature on a New Zealand snapper (Chrysophrys a uratus) population

Highlights

• Modelling suggests the effect of climate change on snapper populations is uncertain.

• Impacts range from a 29% reduction to a 44% increase in fishery yield.

• These impacts are most likely mediated via impacts on recruitment.

Abstract

Anthropogenic CO2 emissions are warming and acidifying Earth’s oceans, which is likely to lead to a variety of effects on marine ecosystems. Fish populations will be vulnerable to this change, and there is now substantial evidence of the direct and indirect effects of climate change on fish. There is also a growing effort to conceptualise the effects of climate change on fish within population models. In the present study knowledge about the response of New Zealand snapper to warming and acidification was incorporated within a stock assessment model. Specifically, a previous tank experiment on larval snapper suggested both positive and negative effects, and otolith increment analysis on wild snapper indicated that growth may initially increase, followed by a potential decline as temperatures continue to warm. As a result of this uncertainty, sensitivity analysis was performed by varying average virgin recruitment (R0) by ±30%, adult growth by ±6%, but adjusting mean size at recruitment by +48% as we had better evidence for this increase. Overall adjustments to R0 had the biggest impact on the future yield (at a management target of 40% of an unfished population) of the Hauraki Gulf snapper fishery. The most negative scenario suggested a 29% decrease in fishery yield, while the most optimistic scenario suggested a 44% increase. While largely uncertain, these results provide some scope for predicting future impacts on the snapper fishery. Given that snapper is a species where the response to climate change has been specifically investigated, increasing uncertainty in a future where climate change and other stressors interact in complex and unpredictable ways is likely to be an important consideration for the management of nearly all fish populations.

Continue reading ‘An uncertain future: effects of ocean acidification and elevated temperature on a New Zealand snapper (Chrysophrys a uratus) population’

Investigating the effects of climate co-stressors on surf smelt energy demands

Surf smelt (Hypomesus pretiosus) are ecologically and economically important to the Pacific Northwest. They play a critical role in the food web and support numerous commercially important species and are an economically important baitfish. Surf smelt interact closely with the nearshore environment, utilizing approximately 10% of Puget Sound coastlines for spawning throughout the year. Surf smelt spawn at high tide and adhere fertilized eggs to beach sediment, causing their embryos to be exposed to air and seawater throughout embryonic development. Because of this unique life history, surf smelt may be susceptible to anthropogenic stressors including coastal development and climate change. However, very few studies have attempted to test the tolerance of surf smelt to climate change, including elevated temperature and ocean acidification. The purpose of this study was to examine the interactive effects of climate co-stressors ocean acidification and seawater warming on the energy demands of developing surf smelt. Surf smelt embryos and larvae were collected and placed into experimental basins under three temperature treatments (12°C, 15°C, and 18°C) and two total carbon treatments (ambient and elevated) for a period of 14 days for the embryos, and 4 days for the larvae. Increased temperature significantly decreased yolk size in developing surf smelt embryos and larvae. During this time, embryo yolk sacs in the high temperature treatment were on average 10.2% smaller than embryo yolk sacs in ambient temperature water. Larval yolk and oil globules mirrored this trend with larvae in the high temperature treatment having on average 32.5% smaller yolk sacs and 20.0% smaller oil globules compared to larvae in ambient temperature. While no effect of acidification as a singular stressor was observed, the interaction with temperature significantly increased surf smelt embryo heart rates by 5% above ambient conditions. These results indicate that near-future climate change scenarios are going to impact the energy demands of developing surf smelt, a result that may have a variety of potential impacts including altered hatch times, larval deformities, and increased mortality, all of which will increase interannual variability in adult recruitment. The results of this study highlight the need to increase focus on studying surf smelt in the context of ecological and climate change research.

Continue reading ‘Investigating the effects of climate co-stressors on surf smelt energy demands’

Are long-term growth responses to elevated pCO2 sex-specific in fish?

Whether marine fish will grow differently in future high pCO2 environments remains surprisingly uncertain. Long-term and whole-life cycle effects are particularly unknown, because such experiments are logistically challenging, space demanding, exclude long-lived species, and require controlled, restricted feeding regimes—otherwise increased consumption could mask potential growth effects. Here, we report on repeated, long-term, food-controlled experiments to rear large populations (>4,000 individuals total) of the experimental model and ecologically important forage fish Menidia menidia (Atlantic silverside) under contrasting temperature (17°, 24°, and 28°C) and pCO2 conditions (450 vs. ~2,200 μatm) from fertilization to ~ a third of this annual species’ life span. Quantile analyses of trait distributions showed mostly negative effects of high pCO2 on long-term growth. At 17°C and 28°C, but not at 24°C, high pCO2 fish were significantly shorter [17°C: -5 to -9%; 28°C: -3%] and weighed less [17°C: -6 to -18%; 28°C: -8%] compared to ambient pCO2 fish. Reductions in fish weight were smaller than in length, which is why high pCO2 fish at 17°C consistently exhibited a higher Fulton’s k (weight/length ratio). Notably, it took more than 100 days of rearing for statistically significant length differences to emerge between treatment populations, showing that cumulative, long-term CO2 effects could exist elsewhere but are easily missed by short experiments. Long-term rearing had another benefit: it allowed sexing the surviving fish, thereby enabling rare sex-specific analyses of trait distributions under contrasting CO2 environments. We found that female silversides grew faster than males, but there was no interaction between CO2 and sex, indicating that males and females were similarly affected by high pCO2. Because Atlantic silversides are known to exhibit temperature-dependent sex determination, we also analyzed sex ratios, revealing no evidence for CO2-dependent sex determination in this species.

Continue reading ‘Are long-term growth responses to elevated pCO2 sex-specific in fish?’

Multimarker response of the ragworm Hediste diversicolor (Polychaeta) to seawater acidification derived from potential CO2 leakage from the CCS sub-seabed storage site in the Baltic Sea

Highlights

• Seawater acidification affected physiological traits, LPO and growth of Hediste diversicolor from the southern Baltic Sea.

• Moderate hypercapnia (pH 7.5–7.1) induced an increase in metabolic rate of the polychaetes and a decline of their growth.

• The most acidic environment (pH 6.5) caused metabolic slow down limiting energy turnover and growth.

• Reduced seawater pH did not impact energetic reserves so, proteins were not used as substrates under acidic conditions.

• High tolerance of the ragworms to hypercapnia stems probably from pre-adaptation to natural pH reduction events in sediment.

Abstract

Sub-seabed Carbon Capture and Storage (CCS) is conceived as safe technology with small likehood of negative consequences to the marine ecosystem but CO2 escape from geological reservoir still poses potential environmental risk. If carbon dioxide leakage occurs carbonate chemistry in the bottom zone and sessile benthic fauna are expected to be the most likely affected by elevated levels of CO2. Though generic mechanisms and advisory conclusions on the presumable impact of increased acidity on the marine benthic biota were formulated they cannot be applied uniformly across different environmental variables as specific local conditions may alter biological response to hypercapnia. A laboratory experiment was conducted to quantify the effects of medium-term (8 wk) exposure to seawater acidification (pH 7.7–6.5) on the infaunal polychaete Hediste diversicolor from the southern Baltic Sea using multimarker approach. Under moderate acidity (pH 7.5 and 7.1) the polychaetes were found to increase metabolic rate (by 13.4% and 19.6%, respectively) and reduce their body mass (by 8.1% and 5.5% wet weight, respectively and by 6.1% and 3.0% dry weight, respectively) whilst enhancing synthesis of antioxidant malondialdehyde (by 22.8% and 65.3%, respectively). In the most acidic environment (pH 6.5) the ragworms showed overall metabolic slow down (by 34.8%) and impaired growth (e.g. by 10.2% for length of the first three segments) indicative of low vulnerability to hypercapnia. High implicit tolerance of the polychaetes to increased acidity in the environment stems inevitably from a certain level of pre-adaptation to pH reduction events which occur in organic-rich stratified sediments due to intense aerobic biomineralization leading often to oxygen depletion and formation of toxic hydrogen sulphide. Acidification did not affect energetic reserves suggesting that costs of acid-base maintenance were covered mainly from assimilated food and that proteins were not used as metabolic substrates.

Continue reading ‘Multimarker response of the ragworm Hediste diversicolor (Polychaeta) to seawater acidification derived from potential CO2 leakage from the CCS sub-seabed storage site in the Baltic Sea’

Effects of ocean acidification on toxicity of two trace metals in two marine molluscs in their early life stages

Ocean acidification (OA) is usually thought to change the speciation of trace metals and increase the concentration of free metal ions, hence elevating metal bioavailability. In this study, embryos of the oyster Crassostrea angulata and abalone Haliotis discus hannai were cultured under 4 pCO2 conditions (400, 800, 1500 and 2000 µatm) with Cu and Zn added. Fertilization rate was measured 2 h post-fertilization (hpf), while larval deformation and larval shell length were measured 24 hpf. Our results show that OA can alleviate Cu and Zn inhibition of C. angulata fertilization by 86.1 and 26.4% respectively, and Zn inhibition of H. discus hannai fertilization by 43.7%. However, OA enhanced the inhibitory effect of Cu on fertilization of H. discus hannai by 34.7%. OA enhanced the toxic effect of Cu on larval normality of C. angulata by 22.0% and the effect of Cu and Zn on larval normality of H. discus hannai by 71.4 and 37.2%, respectively. OA also enhanced the inhibitory effects of Cu and Zn on larval calcification in H. discus hannai by 8.8 and 8.6%, respectively. However, OA did not change the effect of Cu on the calcification of C. angulata larvae. OA decreased Zn inhibition of oyster larval calcification from 3.1 to 1.5%. Based on our results, the toxic effects of metal on early development of molluscs are not always increased by rising pCO2 and differ across developmental stages, egg structure and species. This complexity suggests that caution should be taken when carrying out multiple environmental stressor tests on molluscan embryos.

Continue reading ‘Effects of ocean acidification on toxicity of two trace metals in two marine molluscs in their early life stages’

Upwelling intensity modulates the fitness and physiological performance of coastal species: implications for the aquaculture of the scallop Argopecten purpuratus in the Humboldt Current System

Highlights

• The activity of PLV upwelling centre affected the environmental variability of Tongoy Bay.

• Stronger upwelling generated more acidic and low oxygen environmental conditions.

• A. purpuratus showed biological mechanisms to handle acidified and hypoxic conditions.

• More intense upwelling events decreased the survivorship of A. purpuratus.

• A potential upwelling intensification will negatively impact the scallop aquaculture.

Abstract

Understanding how marine species cope with the natural environmental variability of their native habitats will provide significant information about their sensitivity to the potential environmental changes driven by climate change. In particular, marine species inhabiting upwelling ecosystems are experiencing low seawater temperatures, as well as, acidic and low oxygen conditions as a consequence of the nature of the deep upwelled waters. Our study is focused on one of the most important socio-economical resources of the Humboldt Current System (HCS): the scallop Argopecten purpuratus which has been historically subjected to intensive aquaculture in areas influenced by upwelling processes. Here, a long-term field experiment was performed to understand how tolerant and well-locally-adapted is A. purpuratus to upwelling conditions by studying a set of fitness, physiological, and biomineralogical traits. Stronger upwelling generated a minor water column stratification, with lower temperatures, pH, and oxygen conditions. On the contrary, as upwelling weakened, temperature, pH, and oxygen availability increased. Finally, upwelling intensity also determined the number, duration, and intensity of the cooling and de-oxygenation events occurring in A. purpuratus habitat, as well as, the food availability (chlorophyll-a concentration, Chl-a). Physiologically, A. purpuratus was able to cope with stressful environmental conditions imposed by higher upwelling intensities by enhancing its metabolic and calcification rates, as well, producing higher concentrations of the shell organic matter under stronger upwelling conditions. However, these physiological changes impacted the total energy budget, which was highly dependent on Chl-a concentration, revealing traits trade-offs with significant fitness costs (higher mortalities emerged when longer and more intense upwelling events succeed). Our study increases the knowledge about the physiological performance and tolerance of this important resource to the ocean acidification and ocean-deoxygenation imposed by variable upwelling intensities, as well as, its potential vulnerability under future changing conditions driven by a potential upwelling intensification.

Continue reading ‘Upwelling intensity modulates the fitness and physiological performance of coastal species: implications for the aquaculture of the scallop Argopecten purpuratus in the Humboldt Current System’


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