Archive for June, 2019

Ocean acidification boosts algal growth but impairs ecological relationships


Photo Credit: CC0 Public Domain

Shrimp fed on marine algae grown in acidic water do not undergo a sex change that is a characteristic part of their reproductive life-cycle, report Mirko Mutalipassi and colleagues at Stazione Zoologica Anton Dohrn in Italy in a study publishing June 26 in the open-access journal PLOS ONE.

The marine shrimp Hippolyte inermis lives in coastal meadows of the seagrass Posidonia oceanica and it has two breeding seasons a year, with some males born in spring developing rapidly and turning into females that produce eggs the following autumn. This depends on a bioactive compound produced by microalgae present in their spring diet (Cocconeis scutellum parva) that triggers male endocrine cells to die. To investigate the impact of ocean acidification on this unusual reproductive cycle, the researchers fed shrimp on algae grown in waters at either pH 8.2 representing current conditions, or pH 7.7 representing forecasted levels of ocean acidity by 2100.

Continue reading ‘Ocean acidification boosts algal growth but impairs ecological relationships’

Shellfish growers are feeling climate change’s effects now

Shellfish growers are feeling climate change’s effects now

Ralph Solomon checks on crops of oyster seed at the Lummi Shellfish Hatchery on June 18. Photo Credit: Mathew Roland / BBJ

Shellfish farming in Washington is a multimillion-dollar industry with a history as deep as Puget Sound. However, recent decades of warming oceans and higher levels of ocean acidification continue to challenge shellfish farming practices.

In and around Whatcom County there are several aquaculture farms, such as Lummi Shellfish Hatchery, Drayton Harbor Oyster Co., Blau Oyster and Taylor Shellfish in Samish Bay. Each farm varies in size, number of employees and type of shellfish produced, but they share one thing in common: the water quality of Puget Sound.

Continue reading ‘Shellfish growers are feeling climate change’s effects now’

Ocean acidification influences plant-animal interactions: the effect of Cocconeis scutellum parva on the sex reversal of Hippolyte inermis

Ocean acidification (O.A.) influences the ecology of oceans and it may impact plant-animal interactions at various levels. Seagrass meadows located at acidified vents in the Bay of Naples (Italy) are considered an open window to forecast the effects of global-changes on aquatic communities. Epiphytic diatoms of the genus Cocconeis are abundant in seagrass meadows, including acidified environments, where they play key ecological roles. A still-unknown apoptogenic compound produced by Cocconeis triggers the suicide of the androgenic gland of Hippolyte inermis Leach 1816, a protandric hermaphroditic shrimp distributed in P. oceanica meadows located both at normal pH and in acidified vents. Feeding on Cocconeis sp. was proven important for the stability of the shrimp’s natural populations. Since O.A. affects the physiology of diatoms, we investigated if, in future scenarios of O.A., Cocconeis scutellum parva will still produce an effect on shrimp’s physiology. Cell densities of Cocconeis scutellum parva cultivated in custom-designed photobioreactors at two pH conditions (pH 7.7 and 8.2) were compared. In addition, we determined the effects of the ingestion of diatoms on the process of sex reversal of H. inermis and we calculated the % female on the total of mature individuals-1 (F/mat). We observed significant differences in cell densities of C. scutellum parva at the two pH conditions. In fact, the highest cell densities (148,808 ±13,935 cells. mm-2) was obtained at day 13 (pH 7.7) and it is higher than the highest cell densities (38,066 (±4,166) cells. mm-2, day 13) produced at pH 8.2. Diatoms cultured at acidified conditions changed their metabolism. In fact, diatoms grown in acidified conditions produced in H. inermis a proportion of females (F/mat 36.3 ±5.9%) significantly lower than diatoms produced at normal pH (68.5 ±2.8), and it was not significantly different from that elicited by negative controls (31.7 ±5.6%).

Continue reading ‘Ocean acidification influences plant-animal interactions: the effect of Cocconeis scutellum parva on the sex reversal of Hippolyte inermis’

Aprender a interpretar la acidificación oceánica con recursos on-line y experimentación contextualizada

In this paper we present an introductory experience of the process of Ocean Acidification –decrease in the pH of sea water–, as part of the Experimental Sciences course of the Bachelor’s Degree in Primary Education. The experience involved the use of on-line resources and contextualized experimentation, in order to promote student’s development of scientific competences and to formulate proposals of improvement within the framework of education for sustainability. Satisfactory results are shown in terms of knowledge acquisition, interpretation of the process analyzed here and awareness of environmental problems. We suggest improvements in the educational curriculum and formulate questions which can generate new research. Finally, limitations of the experience regarding its novelty and the lack of adequate educational resources are discussed.

En este artículo se presenta una experiencia de introducción al proceso de acidificación oceánica –disminución del pH del agua del mar– en aulas de Ciencias Experimentales del Grado en Educación Primaria, utilizando recursos on-line y experimentación contextualizada, para contribuir al desarrollo de competencias científicas y formular propuestas de mejora del currículo en el marco de la educación para la sustentabilidad. Se ha contribuido a la adquisición de conocimientos, a la interpretación del proceso estudiado y a la concienciación ambiental. Se han hecho propuestas de mejora del currículo y se han formulado preguntas que darán origen a nuevas investigaciones. Finalmente, se señalan limitaciones de la experiencia relativas a su novedad y a la escasez de recursos didácticos adecuados.

Continue reading ‘Aprender a interpretar la acidificación oceánica con recursos on-line y experimentación contextualizada’

Training course on best practices for ocean acidification experiments in multi-stressor scenarios

DSC_0553The IAEA Environment Laboratories in Monaco welcomed 16 participants from 16 countries on 24-28 May 2019, for a training course on designing and running multi-stressor experiments. The course taught participants how to use the Multiple Environmental Driver Design Lab for Experiments (MEDDLE), produced by the Scientific Committee on Oceanic Research (SCOR) Working Group 149.  This new product includes a handbook, decision support tools, an experiment simulator, and video tutorials. Participants were able to use these new tools to plan their own experimental designs and research questions. An interdisciplinary lecture team, including members of the SCOR Working Group 149, led this course: Dr. Christina McGraw (University of Otago, New Zealand), Dr. Sam Dupont (University of Gothenburg, Sweden), Dr. Marcello Vichi (University of Cape Town, South Africa),  Dr. Steeve Comeau (Institut de la Mer de Villefranche, France), and Dr. Christian Pansch-Hattich (GEOMAR, Germany).

Continue reading ‘Training course on best practices for ocean acidification experiments in multi-stressor scenarios’

Seasonal interactive effects of pCO2 and irradiance on the ecophysiology of brown macroalga Fucus vesiculosus L.

Stochastic upwelling of seawater in the Baltic Sea from the deep, anoxic bottoms may bring low-pH water rich in CO2 close to the surface. Such events may become more frequent with climate change and ongoing ocean acidification (OA). Photoautotrophs, such as macroalgae, which are important foundation species, have been proposed to benefit from increased carbon availability due to reduced energetic cost in carbon acquisition. However, the exact effects of CO2 fertilization may depend on the ambient light environment, as photosynthesis rates depend on available irradiance. In this experimental study, interacting effects of CO2 addition and irradiance on the habitat-forming macroalga Fucus vesiculosus were investigated during two seasons – winter and summer – in the northern Baltic Sea. Growth rates remained unaffected by CO2 or irradiance during both seasons, suggesting that direct effects of elevated CO2 on mature F. vesiculosus are small. Increases in CO2 affected algal elemental ratios by increasing carbon and decreasing nitrogen content, with resulting changes in the C:N ratio, but only in winter. In summer, chlorophyll a content increased under low irradiance. Increases in CO2 caused a decline in light-harvesting efficiency (decrease in Fv/Fm and α) under high irradiance in summer, and conversely increased α under low irradiance. High irradiance caused increases in the maximum relative electron transport rate (rETRmax) in summer, but not in winter. Differences between winter and summer indicate that F. vesiculosus responses to CO2 and irradiance are season-specific. Increases in carbon content during winter could indicate slightly positive effects of CO2 addition in the long run if the extra carbon gained may be capitalized in growth. The results of this study suggest that increases in CO2, either through upwelling or OA, may have positive effects on F. vesiculosus, but these effects are probably small.

Continue reading ‘Seasonal interactive effects of pCO2 and irradiance on the ecophysiology of brown macroalga Fucus vesiculosus L.’

Corals can survive in acidified ocean conditions, but have lower density skeletons


Researchers transplanted coral fragments to sites with low-pH conditions similar those expected with future ocean acidification, then monitored their survival and growth. This photo shows the control site at the start of the experiment. (Photo courtesy of Donald Potts)

Coral reefs face many challenges to their survival, including the global acidification of seawater as a result of rising carbon dioxide levels in the atmosphere. A new study led by scientists at UC Santa Cruz shows that at least three Caribbean coral species can survive and grow under conditions of ocean acidification more severe than those expected to occur during this century, although the density of their skeletons was lower than normal.

The study took advantage of the unusual seawater chemistry found naturally at sites along the Caribbean coastline of Mexico’s Yucatan Peninsula, where water discharging from submarine springs has lower pH than the surrounding seawater, with reduced availability of the carbonate ions corals need to build their calcium carbonate skeletons.

Continue reading ‘Corals can survive in acidified ocean conditions, but have lower density skeletons’

Species-specific calcification response of Caribbean corals after 2-year transplantation to a low aragonite saturation submarine spring

Coral calcification is expected to decline as atmospheric carbon dioxide concentration increases. We assessed the potential of Porites astreoides, Siderastrea siderea and Porites porites to survive and calcify under acidified conditions in a 2-year field transplant experiment around low pH, low aragonite saturation (Ωarag) submarine springs. Slow-growing S. siderea had the highest post-transplantation survival and showed increases in concentrations of Symbiodiniaceae, chlorophyll a and protein at the low Ωarag site. Nubbins of P. astreoides had 20% lower survival and higher chlorophyll a concentration at the low Ωarag site. Only 33% of P. porites nubbins survived at low Ωarag and their linear extension and calcification rates were reduced. The density of skeletons deposited after transplantation at the low Ωarag spring was 15–30% lower for all species. These results suggest that corals with slow calcification rates and high Symbiodiniaceae, chlorophyll a and protein concentrations may be less susceptible to ocean acidification, albeit with reduced skeletal density. We postulate that corals in the springs are responding to greater energy demands for overcoming larger differences in carbonate chemistry between the calcifying medium and the external environment. The differential mortality, growth rates and physiological changes may impact future coral species assemblages and the reef framework robustness.

Continue reading ‘Species-specific calcification response of Caribbean corals after 2-year transplantation to a low aragonite saturation submarine spring’

Fish facing global change: are early stages the lifeline?

• The potential benefits of plasticity depend on several factors.

• Further knowledge of concurrent effects of several environmental factors is needed.

• It is also crucial to pursue and deepen transgenerational work.

• Models should take phenotypic plasticity into greater account.

The role of phenotypic plasticity in the acclimation and adaptive potential of an organism to global change is not currently accounted for in prediction models. The high plasticity of marine fishes is mainly attributed to their early stages, during which morphological, structural and behavioural functions are particularly sensitive to environmental constraints. This developmental plasticity can determine later physiological performances and fitness, and may further affect population dynamics and ecosystem functioning. This review asks the essential question of what role early stages play in the ability of fish to later cope with the effects of global change, considering three key environmental factors (temperature, hypoxia and acidification). After having identified the carry-over effects of early exposure reported in the literature, we propose areas that we believe warrant the most urgent attention for further research to better understand the role of developmental plasticity in the responses of marine organisms to global change.

Continue reading ‘Fish facing global change: are early stages the lifeline?’

Ocean acidification reduces growth and grazing of Antarctic heterotrophic nanoflagellates

High-latitude oceans have been identified as particularly vulnerable to ocean acidification if anthropogenic CO2 emissions continue. Marine microbes are an essential part of the marine food web and are a critical link in biogeochemical processes in the ocean, such as the cycling of nutrients and carbon. Despite this, the response of Antarctic marine microbial communities to ocean acidification is poorly understood. We investigated the effect of increasing fCO2 on the growth of heterotrophic nanoflagellates (HNF), nano- and picophytoplankton, and prokaryotes in a natural coastal Antarctic marine microbial community from Prydz Bay, East Antarctica. At CO2 levels ≥ 634 μatm, HNF abundance was reduced, coinciding with significantly increased abundance of picophytoplankton and prokaryotes. This increase in picophytoplankton and prokaryote abundance was likely due to a reduction in top-down control of grazing HNF. Nanophytoplankton abundance was significantly elevated in the 634 and 953 μatm treatments, suggesting that moderate increases in CO2 may stimulate growth. Changes in predator-prey interactions with ocean acidification could have a significant effect on the food web and biogeochemistry in the Southern Ocean. Based on these results, it is likely that the phytoplankton community composition in these waters will shift to communities dominated by prokaryotes, nano- and picophytoplankton. This may intensify organic matter recycling in surface waters, leading to a decline in carbon flux, as well as a reducing the quality and quantity of food available to higher trophic organisms.

Continue reading ‘Ocean acidification reduces growth and grazing of Antarctic heterotrophic nanoflagellates’

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Ocean acidification in the IPCC AR5 WG II

OUP book