Repeated measurement of MO2 in small aquatic organisms: a manual intermittent flow respirometer using off-the-shelf components

Measurement of rates of oxygen consumption (MO2) in small aquatic embryos or larvae (< 1mm) in response to altered environmental conditions has traditionally been challenging. Here, using modifications of a commercially available fluorescent optode flow-through cell (FTC: PreSens{trade mark, serif} FTC-PSt3) and routine laboratory supplies (syringes, stopcocks, tubing), we have constructed a manual intermittent flow respirometer (MIFR) that allows measurement of MO2 in small numbers of individuals when sequentially exposed to different environmental conditions (e.g. changes in seawater pH) through a gravity-driven media replacement perfusion system. We first show that the FTC can be used in ‘static’ mode while incubating small numbers of embryos/larvae contained within the planar oxygen sensor (POS) chamber with Nitex filters. We then demonstrate the use of the MIFR by exposing larval echinoderms (Fellaster zelandiae, Evechinus chloroticus, Centrostephanus rodgersii) to seawater equilibrated with elevated CO2, and measured MO2 during acute and chronic exposure to hypercapnia. This MIFR method will allow investigators to address questions regarding the respiratory physiology of small aquatic animals, such as the thresholds for metabolic depression in embryonic and larval forms.

Continue reading ‘Repeated measurement of MO2 in small aquatic organisms: a manual intermittent flow respirometer using off-the-shelf components’

Reduced spore germination explains sensitivity of reef-building algae to climate change stressors

Reduced seawater pH and changes in carbonate chemistry associated with ocean acidification (OA) decrease the recruitment of crustose coralline algae (CCAcf.), an important coral-reef builder. However, it is unclear whether the observed decline in recruitment is driven by impairment of spore germination, or post-settlement processes (e.g. space competition). To address this, we conducted an experiment using a dominant CCA, Porolithon cf. onkodes to test the independent and combined effects of OA, warming, and irradiance on its germination success and early development. Elevated CO2 negatively affected several processes of spore germination, including formation of the germination disc, initial growth, and germling survival. The magnitude of these effects varied depending on the levels of temperature and irradiance. For example, the combination of high CO2 and high temperature reduced formation of the germination disc, but this effect was independent of irradiance levels, while spore abnormalities increased under high CO2 and high temperature particularly in combination with low irradiance intensity. This study demonstrates that spore germination of CCA is impacted by the independent and interactive effects of OA, increasing seawater temperature and irradiance intensity. For the first time, this provides a mechanism for how the sensitivity of critical early life history processes to global change may drive declines of adult populations of key marine calcifiers.

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Hope for coral facing ocean acidification

New research suggests corals can adapt their metabolism to increases in ocean acidity.

Coral may cope better with ocean acidification than scientists had thought.

Coral may cope better with ocean acidification than scientists had thought.
Prasit / Getty


Coral may be able to acclimatise and thrive despite increasingly acidic oceans, according to new collaborative research that suggests some hope for reefs.

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Climate change projections for the surface ocean around New Zealand

The future status of the surface ocean around New Zealand was projected using two Earth System Models and four emission scenarios. By 2100 mean changes are largest under Representative Concentration Pathway 8.5 (RCP8.5), with a +2.5°C increase in sea surface temperature, and decreases in surface mixed layer depth (15%), macronutrients (7.5–20%), primary production (4.5%) and particle flux (12%). Largest macronutrient declines occur in the eastern Chatham Rise and subantarctic waters to the south, whereas dissolved iron increases in subtropical waters. Surface pH projections, validated against subantarctic time-series data, indicate a 0.335 decline to ∼7.77 by 2100. However, projected pH is sensitive to future CO2 emissions, remaining within the current range under RCP2.6, but decreasing below it by 2040 with all other scenarios. Sub-regions vulnerable to climate change include the Chatham Rise, polar waters south of 50°S, and subtropical waters north of New Zealand, whereas the central Tasman Sea is least affected.

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Ocean acidification poses looming threat to corals

Precise measurement of boron isotopes in skeleton reveals impact

Researchers at the University of Tokyo and their collaborators have revealed that boron isotope ratios in skeletons of long-lived reef-building corals, called Porites, in the western North Pacific Ocean are experiencing a rapid decrease in recent years. The group used coral skeletons collected from Japan’s Chichijima and Kikaijima islands, in the Ogasawara and Amami archipelagoes, respectively, to analyze the boron isotope ratios, which reflect the pH (acidity) of the skeletons’ calcification fluid. This finding promises to provide important insights for projecting the future response of coral reef ecosystems to climate change caused by humans.

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BIOACID Science Portrait: Felix Ekardt (video, in German; English subtitles)

The jurist, philosopher and sociologist Prof. Felix Ekardt is founder and director of the Research Unit Sustainability and Climate Policy and external professor for public law and legal philosophy at Rostock University.

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Sauer ist gar nicht lustig (in German)

Mit ihren CO2-Emissionen veranstaltet die moderne Zivilisation auch ein gigantisches Chemie-Experiment in den Weltmeeren. Langsam wird klar, was dabei herauskommt. Es ist gruselig.

Zehn Jahre ist es her, dass die Whiskey Creek Shellfish Hatchery ein ernstes Problem bekam. Die Firma an der Küste des amerikanischen Bundesstaates Oregon ist spezialisiert auf die Aufzucht von Muschellarven, insbesondere der Pazifischen Felsenauster. Damit beliefert sie Dutzende von Austernfarmer der Region. Sie sind Arbeitgeber von insgesamt 3200 Menschen. Im Herbst 2007 aber starben die Austernbabys wie die Fliegen. „Wir vermuteten zuerst ein Bakterienproblem und desinfizierten alles“, notierte Alan Barton, der Produktionsmanager des Unternehmens, unlängst in einem Blog. Doch es half nichts. 2008 weitete sich das Problem aus, bis zu 75 Prozent der Produktion gingen verloren.

Continue reading ‘Sauer ist gar nicht lustig (in German)’

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Ocean acidification in the IPCC AR5 WG II

OUP book