Posts Tagged 'morphology'

Variation in the effects of ocean acidification on shell growth and strength in two intertidal gastropods

Many marine organisms rely on calcified hard parts to resist predation, and ocean acidification (OA) affects calcification negatively. However, calcification-related consequences may manifest in variable and/or cryptic ways across species. For example, shell strength is a primary defense for resisting shell-crushing predation, yet the consequences of OA on such biomechanical properties cannot be assessed visually. We exposed 2 species of intertidal gastropods common to the west coast of North America (the black turban snail Tegula funebralis and the striped dogwhelk Nucella ostrina) to OA (pH decreased by ~0.5 units) and predation cues for 6 mo, then measured both shell growth and strength. Shell growth in T. funebralis was significantly depressed under OA and in the presence of predation cues (declines of 83 and 63%, respectively). Shells produced by OA-exposed T. funebralis were also 50% weaker. In contrast, shell growth of N. ostrina was unaffected by OA, yet its shells were still 10% weaker. These findings highlight the potential for both different and easily overlooked responses of organisms to seawater acidification. Moreover, such results raise the possibility of ensuing shifts in consumption rates and rankings of prey items by shell-crushing predators, leading to shifts in the balance of species interactions in temperate shoreline communities.

Continue reading ‘Variation in the effects of ocean acidification on shell growth and strength in two intertidal gastropods’

Ocean acidification reduces net calcification and wound healing in the tropical crustose coralline alga, Porolithon onkodes (Corallinales, Rhodophyta)


  • Wounding did not affect net calcification or tissue mortality in Porolithon onkodes.
  • In contrast, elevated pCO2 reduced net calcification and living tissue.
  • Elevated pCO2 also reduced tissue regeneration within wounds.
  • Reduced wound healing under elevated pCO2 could affect the ecology of coralline algae.


Reef dwelling algae employ a variety of physical and chemical defenses against herbivory, and the response to wounding is extremely important in algal communities. Wound healing mechanisms in crustose coralline algae (CCA) are related to skeletal growth and net calcification rate. Ocean acidification (OA) is known to affect rates of net calcification in a number of calcifying organisms, including CCA. Reduced rates of net calcification in CCA are likely to alter wound healing, and thus affect the consequences of herbivore-CCA interactions on coral reefs. The response of the tropical CCA Porolithon onkodes to OA and artificial wounding was quantified in a 51-day laboratory experiment. Eight artificially wounded (cut to a mean depth of 182 μm) and eight non-wounded samples of P. onkodes were randomly placed into each of four treatments (n = 64 samples total). Each treatment was maintained at a different pCO2 level representative of either ambient conditions or end-of-the-century, predicted conditions (IPCC, 2014); 429.31 ± 20.84 (ambient), 636.54 ± 27.29 (RCP4.5), 827.33 ± 38.51 (RCP6.0), and 1179.39 ± 88.85 μatm (RCP8.5; mean ± standard error). Elevated pCO2 significantly reduced rates of net calcification in both wounded and non-wounded samples of P. onkodes (slopes = −6.4 × 10−4 and −5.5 × 10−4 mg cm−2 d−1 per μatm pCO2, respectively over 51 days). There also was a significant reduction in the rate of vertical regeneration of thallus tissue within the wounds as pCO2 increased (slope = −1.5 × 10−3 μm d−1 per μatm pCO2 over 51 days). This study provides evidence that elevated pCO2 could reduce the ability of this important alga to recover from wounding. Because wounding by herbivores plays an important role in determining CCA community structure, we propose reduced wound healing as a mechanism by which OA might affect the structure and functional roles of CCA communities on coral reefs.

Continue reading ‘Ocean acidification reduces net calcification and wound healing in the tropical crustose coralline alga, Porolithon onkodes (Corallinales, Rhodophyta)’

Influence of water quality parameters on the prevalence of Livoneca redmanii (Isopoda; Cymothoidae) infestation of Mediterranean Sea fishes, Egypt

The quality of water in the aquatic ecosystem is a very sensitive issue and is controlled by many physical and chemical factors. The deterioration of water quality has variable effect on parasitic population and their rate of infestation and consequently the negative impact can impede fish viability and productivity. The current study aimed to: i) Surveying the parasitic isopod infesting some of the edible fish species inhabit the Egyptian Mediterranean Sea water ii) Assess the seasonal variations in water quality parameters of Mediterranean coastal water of Egypt. iii) Investigating the effect of water quality parameters on the rate of parasitic isopod infestation among the examined fishes. Water samples during each season were analyzed for physico-chemical parameters using standard methods. The selected parameters namely: temperature, pH, salinity, oxidizable organic matter (OOM), ammonia, nitrite, nitrate and some heavy metals (Lead, Copper, Arsenic and Mercury). A total of 400 Mediterranean Sea fish of Tilapia zilli, Solea spp, Mugil capito and Sardinella species were examined for isopod parasites. Parasites were preserved and identified. The results revealed isolation of the isopod species Livoneca redmanii, with an infestation rate of 19% among the examined fish species with the highest rate among Mugil capito (36%) and reached its total maximum value during summer (32%). Correlation analysis revealed that infestation rates were highly correlated (positively) with certain water quality parameters, such as temperature, oxidzable organic matter (OOM) and nitrite. High water temperatures during summer and spring seasons, and high nitrite concentrations were significantly associated with high infestation rates in Tilapia zilli (R2=0.91, P=0.046 and R2 = 0.97, P=0.015). The findings suggested that deterioration of water quality with varying seasons was stressful to fish, and consequently increased the incidences of the parasitic Isopod (Livoneca redmanii) so considered as a predisposing agent to parasitism. The study recommended
periodical monitoring of water quality parameters in fish water resources and the need to take all measures by the responsible authorities to prevent pollution of these resources to minimized and control the prevalence of parasite
infestations particularly of isopods.

Continue reading ‘Influence of water quality parameters on the prevalence of Livoneca redmanii (Isopoda; Cymothoidae) infestation of Mediterranean Sea fishes, Egypt’

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’

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


• 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.


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’

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


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.


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’

Little evidence of adaptation potential to ocean acidification in sea urchins living in “future ocean” conditions at a CO2 vent

Ocean acidification (OA) can be detrimental to calcifying marine organisms, with stunting of invertebrate larval development one of the most consistent responses. Effects are usually measured by short‐term, within‐generation exposure, an approach that does not consider the potential for adaptation. We examined the genetic response to OA of larvae of the tropical sea urchin Echinometra sp. C. raised on coral reefs that were either influenced by CO2 vents (pH ~ 7.9, future OA condition) or nonvent control reefs (pH 8.2). We assembled a high quality de novo transcriptome of Echinometra embryos (8 hr) and pluteus larvae (48 hr) and identified 68,056 SNPs. We tested for outlier SNPs and functional enrichment in embryos and larvae raised from adults from the control or vent sites. Generally, highest FST values in embryos were observed between sites (intrinsic adaptation, most representative of the gene pool in the spawned populations). This comparison also had the highest number of outlier loci (40). In the other comparisons, classical adaptation (comparing larvae with adults from the control transplanted to either the control or vent conditions) and reverse adaptation (larvae from the vent site returned to the vent or explanted at the control), we only observed modest numbers of outlier SNPs (6–19) and only enrichment in two functional pathways. Most of the outliers detected were silent substitutions without adaptive potential. We conclude that there is little evidence of realized adaptation potential during early development, while some potential (albeit relatively low) exists in the intrinsic gene pool after more than one generation of exposure.

Continue reading ‘Little evidence of adaptation potential to ocean acidification in sea urchins living in “future ocean” conditions at a CO2 vent’

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Ocean acidification in the IPCC AR5 WG II

OUP book