Posts Tagged 'mortality'

Effects of diel-cycling hypoxia and acidification on juvenile weakfish Cynoscion regalis growth, survival, and activity

During summertime, dissolved oxygen (DO) and pH/pCO2 cycle daily in shallow estuarine waters used by young fishes as nursery habitat. Laboratory experiments on juvenile weakfish Cynoscion regalis examined individual and interactive impacts of present-day levels of diel-cycling hypoxia and acidification on growth and activity. Fish were exposed to 3 DO treatments (extreme cycling DO, 1-11 mg O2 l-1; moderate cycling DO, 3-9 mg O2 l-1; and constant normoxia, 7.5 mg O2 l-1) and 3 pH treatments (extreme cycling pH, 6.8-8.1; moderate cycling pH, 7.2-7.8; and constant pH, 7.5) for 20 d in a 3 × 3 factorial design. Growth was not impacted by moderate diel cycles of DO and acidification with mean daily lows of 3.0-3.3 mg O2 l-1 and mean daily highs of 7.8-9.5 mg O2 l-1 (mean daily low pH 7.03-7.47 and high pCO2 ~16000-5000 µatm). However, 100% mortality occurred within ~10 d at extreme diel-cycling hypoxia during which DO cycled between mean daily lows of 1.5-2.1 mg O2 l-1, mean daily low pH 6.99-7.44, and associated high pCO2 of ~16500-5500 µatm. We found no clear independent or interactive effect of pH/pCO2 on growth or survival despite pH being as low as 6.86 and pCO2 as high as ~20000 µatm. Furthermore, fish that survived as much as 10 d exposure to extreme and moderate diel cycles of DO and acidification experienced no residual negative impact on growth following return to normoxia and static pH. Our results suggest that juvenile weakfish have substantial tolerance of diel cycles of oxygenation and acidification encountered in shallow estuarine nursery habitat.

Continue reading ‘Effects of diel-cycling hypoxia and acidification on juvenile weakfish Cynoscion regalis growth, survival, and activity’

Assessment of the environmental impacts of ocean acidification (OA) and carbon capture and storage (CCS) leaks using the amphipod Hyale youngi

This study aims to ascertain the effects of CO2 induced water acidification and leaks from Carbon Capture and Storage activities on the South American amphipod Hyale youngi. A 10-day acute toxicity test was performed using sediments from two sites located inside the Santos Estuarine System. They were subjected to five pH treatments (8.1, 7.6, 7.0, 6.5, and 6.0). Metals (Cd, Cu, Cr, Pb, Ni and Zn) and the metalloid As were analyzed to determine the influence of their acidification-related mobility on the amphipods mortality. The results showed that mortality becomes significant when compared to control in pH 6.5 in the Canal de Piaçaguerasediment (contaminated) and at pH 6.0 in Ilha das Palmas sediment (reference).

Continue reading ‘Assessment of the environmental impacts of ocean acidification (OA) and carbon capture and storage (CCS) leaks using the amphipod Hyale youngi’

Effect of increased pCO2 in seawater on survival rate of different developmental stages of the harpacticoid copepod Tigriopus japonicus

The rapid increase in carbon dioxide levels in seawater is causing ocean acidification and is expected to have significant effects on marine life. To explore the ability of the harpacticoid copepod Tigriopus japonicus to adapt to an increased concentration of dissolved carbon dioxide (CO2) in seawater, we compared the survival rates of adult and nauplius stages at 400, 1000, and 1550 ppm pCO2 over a 14-day period. The survival rate of T. japonicus dramatically decreased over time with increase in pCO2concentration. At 1550 ppm, the survival rate showed a decrease of more than 20% at the end of the experimental period over that at 400 ppm. Furthermore, the survival rate decreased by a greater amount at all concentrations in nauplii than in adults, with a greater effect in wild-collected specimens than in culture-derived individuals. The results suggest that future ocean acidification may negatively influence the sustainability of T. japonicus and thus may eventually influence benthic ecosystems.

Continue reading ‘Effect of increased pCO2 in seawater on survival rate of different developmental stages of the harpacticoid copepod Tigriopus japonicus’

Similar oyster reproduction across estuarine regions differing in carbonate chemistry

In laboratory studies, shellfish larvae often respond negatively to augmented [CO2], but no prior tests have related wild bivalve larval performance and carbonate chemistry spatiotemporally. The geography of Willapa Bay (Washington, USA) naturally generates two distinct regions of carbonate chemistry where non-native Pacific oysters (Crassostrea gigas) dominate the intertidal fauna and successfully reproduce. On the river-influenced east side, pCO2 is higher and alkalinity lower, which both contribute to reduced aragonite saturation state (Ωaragonite 1.3–1.5) relative to the west side receiving low watershed inputs (Ωaragonite 1.8–1.9). pHsws is also >0.1 lower on the east vs. west sides. Despite this difference in field conditions, no biological signal related to carbonate chemistry was apparent in oyster reproduction based on coupled chemical–biological comparisons over three summers. Instead, survival was equal between the two sides of the bay, and settlement was equal or higher on the low-Ωaragonite, low-pH east side. In a temporal comparison of four larval cohorts, settlement differed by two orders of magnitude and increased with water temperature. These field data on oyster reproduction illustrate that population-level effects may not emerge in higher mean [CO2] conditions, with possible decoupling due to local adaptation, spatio-temporal heterogeneity, or higher sensitivity to other axes of environmental variability such as temperature.

Continue reading ‘Similar oyster reproduction across estuarine regions differing in carbonate chemistry’

Effects of increasing pCO2 on life history traits and feeding of the littoral mysid Praunus flexuosus

Mysids, an important food web component in the littoral zone of coastal waters, have been neglected so far in ocean acidification research. Juveniles of the littoral mysid Praunus flexuosus were exposed in the laboratory to four pCO2 levels (530, 930, 1200, and 1600 µatm) for 5 weeks. In addition, juveniles were provided with two different food levels during the experiment. High pCO2 did not affect survival, but delayed moulting. Juvenile growth decreased and inter-moult period between the last moulting events increased with increasing pCO2 at low but not at high food supply, suggesting that high food availability is needed to prevent these negative effects of elevated pCO2. However, small individual juveniles showed lower feeding rates at high pCO2 compared to the control after prolonged exposure, suggesting decreased activity likely due to impaired metabolism. The subtle negative effects of elevated pCO2 on life history traits observed in this study suggest that P. flexuosus probably has to adapt to counteract adverse effects of predicted high pCO2, especially when food is limiting.

Continue reading ‘Effects of increasing pCO2 on life history traits and feeding of the littoral mysid Praunus flexuosus’

Short-term effects of increased temperature and lowered pH on a temperate grazer-seaweed interaction (Littorina obtusata/Ascophyllum nodosum)

There has been a significant increase in the literature regarding the effects of warming and acidification on the marine ecosystem. To our knowledge, there is very little information on the potential effects of both combined stressors on marine grazer-seaweed interactions. Here, we evaluated, for the first time several phenotypic responses (e.g periwinkle survival, condition index, consumption rates, seaweed photosynthetic activity and oxidative stress) of the temperate periwinkle Littorina obtusata (grazer) and the brown seaweed Ascophyllum nodosum (prey) to such climate change-related variables, for 15 days. Increased temperature (22 °C, pH 8.0) elicited a significant lethal effect on the periwinkle within a short-term period (mortality rate > 90%). Acidification condition (18 °C, pH 7.6) was the one that showed lower mortality rates (≈20%), reflected by lower impact on periwinkle fitness and consumption rates. Under a scenario of increased temperature and lowered pH the antioxidant defences of L. obtusata seemed to be supressed increasing the risk of peroxidative damage. The seaweed evidenced signs of cellular damage under such conditions. These results suggest that: i) lower pH per se seems to benefit the interaction between grazer and seaweed while, ii) a combined scenario of increased temperature and lowered pH may be negative for the interaction, due to the unbalance between periwinkle mortality rates and consumption rates. But most importantly, since grazing often plays an important role on structuring natural communities, such predator-prey disturbances can elicit cascading effects on the remaining community structure and functioning of the temperate rocky-shore ecosystems.

Continue reading ‘Short-term effects of increased temperature and lowered pH on a temperate grazer-seaweed interaction (Littorina obtusata/Ascophyllum nodosum)’

The survival, recovery, and diversification of metazoan reef ecosystems following the end-Permian mass extinction event

The Triassic Period records important ecological transitions in the aftermath of the end-Permian mass extinction and is a key interval in the evolution of modern coral reefs. There have been several critical developments in our understanding of Triassic reef evolution over the past decade: the timing of events and duration of stages have changed dramatically; the discovery of metazoan reefs in the Early Triassic; details about the environmental perturbations that drove the extinction; the relationship between tectonic activity and platform margin reef proliferation; and additional proxy evidence for the co-evolution of coral reef-builders and their photosymbionts. Here, we provide an up-to-date synthesis of reef collapse and recovery dynamics following the end-Permian extinction, specifically integrating recent discoveries. The evolution of reef ecosystems can be divided into five phases based on their composition. 1) Microbial-metazoan reefs represent survival communities that characterize the immediate extinction aftermath. 2) The re-establishment of reefs built by metazoans (small sponge biostromes and bivalve buildups) is observed in oxygenated settings in the Olenekian (Early Triassic). 3) Towards the end of the Olenekian and into the Anisian (Middle Triassic) low-diversity, “Tubiphytes”-dominated reefs formed, which represent the first Triassic platform-margin reefs; platform-margin reefs, however, are not widespread until the late Anisian. 4) Late Anisian reefs also record a composition change and increase in species richness with sponges and “Tubiphytes” as the main reef builders. 5) The first scleractinian corals (which are the main reef builder in modern marine reef ecosystems) evolved during the Anisian but are not reported as dominant reef builders until the Late Triassic. The radiation of coral reefs is posited to be coupled to the acquisition of photosymbionts (e.g., zooxanthellae). There is clearly a stepwise evolution of reef types during the Triassic; however, once each reef type appears it persists throughout the remainder of the Triassic. The survival, recovery, and diversification of reef ecosystems is, therefore, more complex than previously outlined, particularly with respect to the earliest post-extinction ecosystems. These recent advances highlight the need to thoroughly document the faunal compositions of understudied reef systems as well as to continue the exploration of Triassic ecosystems in underrepresented regions.

Continue reading ‘The survival, recovery, and diversification of metazoan reef ecosystems following the end-Permian mass extinction event’


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Ocean acidification in the IPCC AR5 WG II

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