Ocean acidification changes balance of biofouling communities

A new study of marine organisms that make up the ‘biofouling community’ — tiny creatures that attach themselves to ships’ hulls and rocks in the ocean around the world — shows how they adapt to changing ocean acidification. Reporting in the journal Global Change Biology, the authors examine how these communities may respond to future change.

There is overwhelming evidence to suggest the world’s oceans are becoming, and will continue to become more acidic in the future, but there are many questions about how it will affect marine life. The ‘biofouling community’ — consisting of tiny species like sea squirts, hard shell worms and sponges — affects many industries including underwater construction, desalination plants and ship hulls. Removing these organisms (a process called antifouling) is estimated to cost around $22 billion a year globally.

Continue reading ‘Ocean acidification changes balance of biofouling communities’

Acidification effects on biofouling communities: winners and losers

How ocean acidification affects marine life is a major concern for science and society. However, its impacts on encrusting biofouling communities, that are both the initial colonizers of hard substrata and of great economic importance, are almost unknown. We showed that community composition changed significantly, from 92% spirorbids, 3% ascidians and 4% sponges initially to 47% spirorbids, 23% ascidians and 29% sponges after 100 days in acidified conditions (pH 7.7). In low pH, numbers of the spirorbid Neodexiospira pseudocorrugata were reduced ×5 compared to controls. The two ascidians present behaved differently with Aplidium sp. decreasing ×10 in pH 7.7, whereas Molgula sp. numbers were ×4 higher in low pH than controls. Calcareous sponge (Leucosolenia sp.) numbers increased ×2.5 in pH 7.7 over controls. The diatom and filamentous algal community was also more poorly developed in the low pH treatments compared to controls. Colonization of new surfaces likewise showed large decreases in spirorbid numbers, but numbers of sponges and Molgula sp. increased. Spirorbid losses appeared due to both recruitment failure and loss of existing tubes. Spirorbid tubes are comprised of a loose prismatic fabric of calcite crystals. Loss of tube materials appeared due to changes in the binding matrix and not crystal dissolution, as SEM analyses showed crystal surfaces were not pitted or dissolved in low pH conditions. Biofouling communities face dramatic future changes with reductions in groups with hard exposed exoskeletons and domination by soft-bodied ascidians and sponges.

Continue reading ‘Acidification effects on biofouling communities: winners and losers’

Effects of ocean acidification on larval development and early post-hatching traits in Concholepas concholepas (loco)

Larval stages represent a bottleneck influencing the persistence of marine populations with complex life cycles. Concholepas concholepas is a gastropod species that sustains the most important small-scale artisanal fisheries of the Chile-Peru Humboldt Coastal current system. In this study, newly-laid egg capsules of C. concholepas collected from 3 localities along the Chilean coast were used to evaluate the potential consequences of projected near-future ocean acidification (OA) on larval development and early post-hatching larval traits. We compared hatching time, hatching success and early survivorship of encapsulated larvae reared under contrasting average levels of pCO2: 382 (present-day), ca. 715 and ca. 1028 µatm CO2 (levels expected in near-future scenarios of OA). Moreover, we compared morphological larval traits such as protoconch size, thickness and statolith size at hatching. Some of the developmental traits were negatively affected by pCO2 levels, source locality, female identity, or the interaction between those factors. Meanwhile, the effect of pCO2 levels on morphological larval traits showed significant interactions depending on differences among egg capsules and females. Our results suggest that OA may decouple hatching time from oceanographic processes associated with larval transport and reduce larval survivorship during the dispersive phase, with a potential impact on the species’ population dynamics. However, the results also show geographic variability and developmental plasticity in the investigated traits. This variation may lead to an increased acclimatization ability, facilitate the persistence of natural populations and mitigate the negative effects that OA might have on landings and revenues derived from the fishery of this species.

Continue reading ‘Effects of ocean acidification on larval development and early post-hatching traits in Concholepas concholepas (loco)’

Continuous monitoring of in vivo chlorophyll a fluorescence in Ulva rigida (Chlorophyta) submitted to different CO2, nutrient and temperature regimes

A Monitoring-PAM fluorometer with high temporal resolution (every 5 min) was used to assess the effects on photosynthesis in Ulva rigida (Chlorophyta) during exposure to 2 different CO2 conditions: current (‘LC’, 390 ppm), and the predicted level for the year 2100 (‘HC’, 700 ppm) in a crossed combination with 2 different daily pulsed nitrate concentrations (‘LN’, 5 µM and ‘HN’, 50 µM) and 2 temperature regimes (ambient and ambient +4°C). Effective quantum yield (ΔF/Fm’) in the afternoon was lower under HCLN conditions than under the other treatments. The decrease in ΔF/Fm’ from noon to the afternoon was significantly lower under +4°C compared to ambient temperature. Maximal quantum yield (Fv/Fm) decreased during the night with a transient increase 1 to 3 h after sunset, whereas a transient increase in ΔF/Fm’ was observed after sunrise. These transient increases have been related to activation/deactivation of the electron transport rate and the relaxation of non-photochemical quenching. Relative electron transport rate was higher under the LC and +4°C treatment, but the differences were not significant due to high variability in daily irradiances. Redundancy analysis on the data matrix for the light periods indicates that photosynthetically active radiation through the day is the main variable determining the physiological responses. The effects of nutrient levels (mainly carbon) and experimental increase of temperature were low but significant. During the night, the effect of nutrient availability is of special importance with an opposite effect of nitrogen compared to carbon increase. The application of the Monitoring-PAM to evaluate the effects of environmental conditions by simulating climate change variations under outdoor-controlled, semi-controlled conditions is discussed.

Continue reading ‘Continuous monitoring of in vivo chlorophyll a fluorescence in Ulva rigida (Chlorophyta) submitted to different CO2, nutrient and temperature regimes’

Mass-transfer gradients across kelp beds influence Macrocystis pyrifera growth over small spatial scales

Nitrogen is essential for algal productivity but often reaches limiting concentrations in temperate ecosystems. Increased water motion enhances nitrogen uptake by decreasing the thickness of the diffusion boundary layer surrounding algal surface tissue, allowing for increased nitrogen mass-transfer across this boundary. Macrocystis pyrifera forms large beds that span the water column and can alter the surrounding physical environment by creating bed-wide boundaries that may reduce current and wave propagation to the bed interior; reduced water motion may decrease mass-transfer rates and therefore alter nitrogen uptake. We investigated whether a water mass-transfer gradient across M. pyrifera beds exists by identifying 3 bed types likely to experience different water motion intensities (open, shoreline exterior and shoreline interior) and whether this gradient influenced heterogeneity in M. pyrifera growth and tissue status during low nitrogen (summer) and high nitrogen (winter) conditions. Gypsum dissolution suggested that mass-transfer significantly increased across beds; open bed dissolution rates were approximately 6% higher than the shoreline exterior, which exhibited mean dissolution rates 17% higher than the shoreline interior. Summer kelp growth, pigmentation, tissue %N and C:N paralleled mass-transfer, where exterior kelp exhibited higher values than interior kelp. The same trends did not exist during the winter, when ambient nitrogen concentrations were high, suggesting that mass-transfer is an important mechanism for nitrogen acquisition during limitation events. This study highlights mass-transfer variability across relatively small macroalgal beds and the corresponding effects on kelp growth and nitrogen status, which previously might have been assumed as uniform due to the general wave exposure.

Continue reading ‘Mass-transfer gradients across kelp beds influence Macrocystis pyrifera growth over small spatial scales’

Glacial melt could change chemistry and food web in world’s oceans

Along with increasing sea levels, melting glaciers are putting something else into the world’s oceans — a huge load of organic carbon that has the potential to change marine chemistry and ecosystems, says a newly published study by a team of mostly Alaska scientists. (…)

The accelerated melt of glaciers gets attention because of its contribution to sea-level rise, but the “real take-home message” of the new study is that there will be “not just changes to the level of the ocean but changes to the chemistry and the food web,” Hood said.

Organic carbon is eaten by microbes and is at the base of the food web, he said. But it can also break down into inorganic carbon, which changes marine chemistry in other ways, he said. (…)

Continue reading ‘Glacial melt could change chemistry and food web in world’s oceans’

Oceans face higher acidity levels as more man-made CO2 gets absorbed

Just about 5 million tons of carbon dioxide (CO2) is dumped into the atmosphere every hour from the burning of fossil fuels mostly for transportation, electrical generation, industry and heating.

This is the fastest rate of CO2 generation that the earth has experienced in millions of years. It’s been estimated that about a quarter of the man-made carbon dioxide from the burning of fossil fuels has been absorbed by the oceans, one quarter by the land, and the rest has accumulated in the atmosphere. All told, around 600 billion tons of CO2 gas since the Industrial Revolution has been absorbed by the ocean.

The absorption of all this CO2 by the world’s oceans has certainly benefited us by reducing the amount of this greenhouse gases in the atmosphere. However, the introduction of massive amounts of CO2 in the world’s oceans is changing the sea’s water chemistry.

Continue reading ‘Oceans face higher acidity levels as more man-made CO2 gets absorbed’


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Ocean acidification in the IPCC AR5 WG II

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