Posts Tagged 'biological response'



Abiotic drivers of interannual phytoplankton variability and a 1999–2000 regime shift in the North Sea examined by multivariate statistics

The Dutch coastal zone is a region of the North Sea with a marked interannual and long‐term abiotic and phytoplankton variability. To investigate the relationship between abiotic variability and phytoplankton composition, two routine water monitoring data sets (1991–2005) were examined. Multivariate statistics revealed two significant partitions in the data. The first consisted of interannual abiotic fluctuations that were correlated to Rhine discharge that affected the abundance of summer and autumn diatom species. The second partition was caused by a shift in the abiotic data from 1998 to 1999 that was followed by a shift in phytoplankton composition from 1999 to 2000. Important factors in the abiotic shift were decreases in suspended matter (SPM) and phosphate (DIP) concentrations, as well as in pH. The decrease in SPM was caused by a reduction in wind speed. The increase in water column daily irradiance from the decrease in SPM led to increases in the abundance of winter–spring species, notably the prymnesiophyte Phaeocystis globosa. Because wind speed is related to the North Atlantic Oscillation (NAO) index it was possible to correlate NAO index and P. globosa abundance. Only five abiotic variables representing interannual and long‐term variability, including Rhine discharge and NAO index, were needed to model the observed partitions in phytoplankton composition. It was concluded that interannual variability in the coastal phytoplankton composition was related to year‐to‐year changes in river discharge while the long‐term shift was caused by an alternating large‐scale meteorological phenomenon.

Continue reading ‘Abiotic drivers of interannual phytoplankton variability and a 1999–2000 regime shift in the North Sea examined by multivariate statistics’

Combined effects of ocean acidification and temperature on larval and juvenile growth, development and swimming performance of European sea bass (Dicentrarchus labrax)

Ocean acidification and ocean warming (OAW) are simultaneously occurring and could pose ecological challenges to marine life, particularly early life stages of fish that, although they are internal calcifiers, may have poorly developed acid-base regulation. This study assessed the effect of projected OAW on key fitness traits (growth, development and swimming ability) in European sea bass (Dicentrarchus labrax) larvae and juveniles. Starting at 2 days post-hatch (dph), larvae were exposed to one of three levels of PCO2 (650, 1150, 1700 μatm; pH 8.0, 7.8, 7.6) at either a cold (15°C) or warm (20°C) temperature. Growth rate, development stage and critical swimming speed (Ucrit) were repeatedly measured as sea bass grew from 0.6 to ~10.0 (cold) or ~14.0 (warm) cm body length. Exposure to different levels of PCO2 had no significant effect on growth, development or Ucrit of larvae and juveniles. At the warmer temperature, larvae displayed faster growth and deeper bodies. Notochord flexion occurred at 0.8 and 1.2 cm and metamorphosis was completed at an age of ~45 and ~60 days post-hatch for sea bass in the warm and cold treatments, respectively. Swimming performance increased rapidly with larval development but better swimmers were observed in the cold treatment, reflecting a potential trade-off between fast grow and swimming ability. A comparison of the results of this and other studies on marine fish indicates that the effects of OAW on the growth, development and swimming ability of early life stages are species-specific and that generalizing the impacts of climate-driven warming or ocean acidification is not warranted.

Continue reading ‘Combined effects of ocean acidification and temperature on larval and juvenile growth, development and swimming performance of European sea bass (Dicentrarchus labrax)’

Flow-driven micro-scale pH variability affects the physiology of corals and coralline algae under ocean acidification

Natural variability in pH in the diffusive boundary layer (DBL), the discrete layer of seawater between bulk seawater and the outer surface of organisms, could be an important factor determining the response of corals and coralline algae to ocean acidification (OA). Here, two corals with different morphologies and one coralline alga were maintained under two different regimes of flow velocities, pH, and light intensities in a 12 flumes experimental system for a period of 27 weeks. We used a combination of geochemical proxies, physiological and micro-probe measurements to assess how these treatments affected the conditions in the DBL and the response of organisms to OA. Overall, low flow velocity did not ameliorate the negative effect of low pH and therefore did not provide a refugia from OA. Flow velocity had species-specific effects with positive effects on calcification for two species. pH in the calcifying fluid (pHcf) was reduced by low flow in both corals at low light only. pHcf was significantly impacted by pH in the DBL for the two species capable of significantly modifying pH in the DBL. The dissolved inorganic carbon in the calcifying fluid (DICcf) was highest under low pH for the corals and low flow for the coralline, while the saturation state in the calcifying fluid and its proxy (FWHM) were generally not affected by the treatments. This study therefore demonstrates that the effects of OA will manifest most severely in a combination of lower light and lower flow habitats for sub-tropical coralline algae. These effects will also be greatest in lower flow habitats for some corals. Together with existing literature, these findings reinforce that the effects of OA are highly context dependent, and will differ greatly between habitats, and depending on species composition.

Continue reading ‘Flow-driven micro-scale pH variability affects the physiology of corals and coralline algae under ocean acidification’

Multi-decadal change in reef-scale production and calcification associated with recent disturbances on a Lizard Island reef flat

Climate change is threatening the persistence of coral reef ecosystems resulting in both chronic and acute impacts which include higher frequency and severity of cyclones, warming sea surface temperatures, and ocean acidification. This study measured net ecosystem primary production (NEP) and net ecosystem calcification (NEC) on a reef flat after the most severe El Nino-driven mass bleaching event on Australia’s Great Barrier Reef (GBR) in 2016 and again in 2018 after another consecutive bleaching event in 2017. Our results indicate temporal changes in reef metabolism likely as result of both the continuing press disturbance of ocean acidification and severe pulse disturbances (cyclones and bleaching events). In 2016, NEP was within the range of values reported in past studies, however, it declined in 2018. NEC over a 12-h period was lower in 2016 than 2018; but when compared with past studies there was a severe decline in daytime net calcification from 2008–2009, to 2016 followed by an increase in 2018 (but still NEC remained lower than values reported in 2008–2009). Conversely, nighttime net calcification was similar to that reported in 2009 indicating nighttime dissolution did not increase over the past decade. Overall coral cover remained stable following recent disturbances, however, algal turf was the dominant benthic component on the reef flat, while calcifiers (corals and calcified algae) were minor components (<20% of total benthic cover). This study documented temporal changes in community function following major pulse disturbances (bleaching events and cyclones) within the context of ongoing OA at the same location over the last decade. Repeated pulse disturbances could jeopardize the persistence of the reef flat as a net calcifying entity, with the potential for cascading effects on other ecosystem services.

Continue reading ‘Multi-decadal change in reef-scale production and calcification associated with recent disturbances on a Lizard Island reef flat’

Effects of long-term exposure to reduced pH conditions on the shell and survival of an intertidal gastropod

Highlights

• Prolonged exposures to high pCO2 can severely affect Phorcus sauciatus shell.

• No effects of high pCO2 were found on size-frequency or population density of P. sauciatus.

• Shells from reduced pH sites exhibited a higher shell aspect ratio and greater percentages of shell dissolution and break.

• Shells from high pCO2 areas exhibited changes in mechanical strength.

• Similar desiccation tolerance was found among contrasting environment populations.

Abstract

Volcanic CO2 vents are useful environments for investigating the biological responses of marine organisms to changing ocean conditions (Ocean acidification, OA). Marine shelled molluscs are highly sensitive to changes in seawater carbonate chemistry. In this study, we investigated the effects of reduced pH on the intertidal gastropod, Phorcus sauciatus, in a volcanic CO2 vent off La Palma Island (Canary Islands, North East Atlantic Ocean), a location with a natural pH gradient ranging from 7.0 to 8.2 over the tidal cycles. Density and size-frequency distribution, shell morphology, shell integrity, fracture resistance, and desiccation tolerance were evaluated between populations from control and CO2 vent sites. We found no effects of reduced pH on population parameters or desiccation tolerance across the pH gradient, but significant differences in shell morphology, shell integrity, and fracture resistance were detected. Individuals from the CO2 vent site exhibited a higher shell aspect ratio, greater percentages of shell dissolution and break, and compromised shell strength than those from the control site. Our results highlight that long-term exposure to high pCO2 can negatively affect the shell features of P. sauciatus but may not have a significant effect on population performance. Moreover, we suggest that loss of shell properties could lead to changes in predator-prey interactions.

Continue reading ‘Effects of long-term exposure to reduced pH conditions on the shell and survival of an intertidal gastropod’

Effects of elevated carbon dioxide on the growth and welfare of Juvenile tiger grouper (Epinephelus fuscoguttatus) × giant grouper (E. lanceolatus) hybrid

Highlights

• High CO2 impair the growth performance and health of hybrid grouper, TGGG juveniles.

• Blood haematological and biochemical indicate TGGG juveniles are unwell when being cultured in high CO2.

• The release of glucose and cortisol in stress condition (high CO2) may include a disturbance of the metabolic balance which inhibit growth and affect the gill structure.

• The stressor (high CO2) may increase the susceptibility to disease in fish as indicated by the swollen gill structure in TGGG juveniles.

Abstract

Increasing carbon dioxide (CO2) in the ocean are predicted to affect vital physiological functions and possibly reduce growth of marine fish. Yet, studies on the impacts on marine fish with the increasing CO2 is still limited. Therefore, this study aimed to explore the elevated CO2 effect on the growth and welfare (condition factor, blood parameters, stress analysis, gill histology) of newly developed commercially important marine fish, tiger grouper (Epinephelus fuscoguttatus) × giant grouper (E. lanceolatus) hybrid or TGGG. TGGG juveniles were exposed for 120 days in a laboratory condition of CO2 groups: 390 μatm (control-current CO2), 610 μatm (moderate) and 1010 μatm (high) consistent with projections for CO2 concentrations in the ocean over the next 50–100 years. The experiments were done in triplicate (20 fish/tank; N = 180, total length = 20.0 ± 0.5 cm, weight = 94.0 ± 3.0 g). Results showed that the lowest specific growth rate (SGR) (0.65 ± 0.05% day−1) and condition factor (1.12 ± 0.01) were observed in high CO2. Unfavourable blood haematological and biochemical parameters were observed in high CO2 group. The highest stress level measured by glucose (102 ± 8 mg dL−1) and cortisol concentration (1.0 ± 0.1 ng mL−1) were also observed in the high CO2. Gill lesions were histologically observed in high CO2 treatment. The results suggested that high CO2 negatively affected the growth and welfare of TGGG. Outputs of this study would offers a simple tool to evaluate the potential risk of elevated CO2 to an important commercial marine grouper.

Continue reading ‘Effects of elevated carbon dioxide on the growth and welfare of Juvenile tiger grouper (Epinephelus fuscoguttatus) × giant grouper (E. lanceolatus) hybrid’

CO2 and HCl-induced seawater acidification impair the ingestion and digestion of blue mussel Mytilus edulis

Highlights

1. The effect of two acidifying treatments, CO2 enrichment and HCl addition, on Mytilus edulis manifests different degrees of damage.

2. The effect of seawater acidification on mussels is not from a single factor (H+) but other action factors related to CO2.

3. Seawater acidification might inhibit the energy intake of mussels through interfering with the processes of ingestion and digestion.

Abstract

Anthropogenic CO2 emissions lead to seawater acidification that reportedly exerts deleterious impacts on marine organisms, especially on calcifying organisms such as mussels. A 21-day experiment focusing on the impacts of seawater acidification on the blue mussel, Mytilus edulis, was performed in this study, within which two acidifying treatments, CO2 enrichment and HCl addition, were applied. Two acidifying pH values (7.7 and 7.1) and the alteration of the key physiological processes of ingestion and digestion were estimated. To thoroughly investigate the impact of acidification on mussels, a histopathological study approach was adopted. The results showed that: (1) Seawater acidification induced either by CO2 enrichment or HCl addition impaired the gill structure. Transmission electron microscope (TEM) results suggested that the most obvious impacts were inflammatory lesions and edema, while more distinct alterations, including endoplasmic reticulum edema, nuclear condensation and chromatin plate-like condensation, were placed in the CO2-treated groups compared to HCl-treated specimens. The ciliary activity of the CO2 group was significantly inhibited simultaneously, leading to an obstacle in food intake. (2) Seawater acidification prominently damaged the structure of digestive glands, and the enzymatic activities of amylase, protease and lipase significantly decreased, which might indicate that the digestion was suppressed. The negative impacts induced by the CO2 group were more severe than that by the HCl group. The present results suggest that acidification interferes with the processes of ingestion and digestion, which potentially inhibits the energy intake of mussels.

Continue reading ‘CO2 and HCl-induced seawater acidification impair the ingestion and digestion of blue mussel Mytilus edulis’


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Ocean acidification in the IPCC AR5 WG II

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