Impact of light and water flow on the responses of coralline algae to ocean acidification

Coralline algae are globally abundant components of benthic habitats and play foundational roles in coastal ecosystems such as temperate kelp forests and coral or rocky reefs, where they are often the dominant substrate cover. The emerging understanding of the sensitivity of coralline algae to ocean acidification (OA) has emphasised the need to determine the natural variability of parameters that could influence growth and reproduction of coralline algae in situ to improve experimentation as well as predictions of climate change outcomes for this group.

To identify spatiotemporal variability of seawater pH inside a Macrocystis pyrifera kelp forest, typical for southern New Zealand with high coralline algae cover, long term (> 1 year) pH, irradiance and temperature data were collected. Seawater pH was highly variable (pHT 7.45–8.49) and exhibited strong diel and seasonal differences that were associated with metabolic activity of the surrounding macroalgal community and linked to peaks of photosynthesis and respiration. These results show that coralline algae inhabit a highly variable environment, with occasional pH minima lower than end of the century predictions for the open ocean. Coralline recruitment peaked between late autumn and winter, when irradiance reaching the benthic communities was up to 85 % lower than during the summer months.

Continue reading ‘Impact of light and water flow on the responses of coralline algae to ocean acidification’

Virtual workshop 2021: session 1 talk 2, essential ocean variables

An introduction to sustained ocean observations and Essential Ocean Variables as a system to improve scientific knowledge about the ocean climate and ecosystems, human impact, and human vulnerability.
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Virtual workshop 2021: session 2 talk 1, monitoring ocean acidification equipment

Overview of how to assemble and connect Ocean Acidification monitoring equipment. The focus will be on pH sensor connectivity, downloading the data files, and familiarising yourself with the suite of cables.
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Virtual workshop 2021: session 3 talk 2 monitoring ocean acidification, learning from the data

We will present some of the data collected from CMEP OA Kits so far and discuss how this data has been used to identify drivers of pH on Barrier Reefs.
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Virtual workshop 2021: session 3 talk 1 monitoring ocean acidification data processing (video & text)

We will demonstrate how to process, quality control and analyse the data collected by the pH and CTDO sensors. We will also give you some recommendations on how to present your data when writing reports.
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Adult exposure to ocean acidification and warming remains beneficial for oyster larvae following starvation

Climate change is expected to warm and acidify oceans and alter the phenology of phytoplankton, creating a mismatch between larvae and their food. Transgenerational plasticity (TGP) may allow marine species to acclimate to climate change; however, it is expected that this may come with elevated energetic demands. This study used the oysters, Saccostrea glomerata and Crassostrea gigas, to test the effects of adult parental exposure to elevated pCO2 and temperature on larvae during starvation and recovery. It was anticipated that beneficial effects of TGP will be limited when larvae oyster are starved. Transgenerational responses and lipid reserves of larvae were measured for 2 weeks. Larvae of C. gigas and S. glomerata from parents exposed to elevated pCO2 had greater survival when exposed to elevated CO2, but this differed between species and temperature. For S. glomerata, survival of larvae was greatest when the conditions experienced by larvae matched the condition of their parents. For C. gigas, survival of larvae was greater when parents and larvae were exposed to elevated pCO2. Larvae of both species used lipids when starved. The total lipid content was dependent on parental exposure and temperature. Against expectations, the beneficial TGP responses of larvae remained, despite starvation.

Continue reading ‘Adult exposure to ocean acidification and warming remains beneficial for oyster larvae following starvation’

Slow-onset events: a review of the evidence from the IPCC special reports on land, oceans and cryosphere

This paper reviews the evidence on slow-onset events presented in the Special Report on Climate Change and Land (SRCCL) and the Special Report on the Ocean and Cryosphere in a Changing Climate (SROCC), both published in 2019. It analyses how the reports, and recent literature cited in them, deal with the eight types of slow-onset events, specified by the UNFCCC: increasing temperatures, sea level risesalinizationocean acidification, glacial retreat, land degradationdesertification and loss of biodiversity. The authors used qualitative data analysis software to analyse the reports, and for each of the SOEs, they coded and analysed information about the state, rate of change, timescale, geography, drivers, impacts, management responses, adaptation limits and residual losses and damages. The paper provides an overview of the state of the art on SOEs and helps to identify gaps and challenges in understanding the nature of SOEs, their impact and effective management approaches.

Continue reading ‘Slow-onset events: a review of the evidence from the IPCC special reports on land, oceans and cryosphere’

Climate and ocean acidification effects on benthos in Kongsfjorden, Svalbard

Climate change and ocean acidification effects on marine organisms are being studied in Kongsfjorden. In field and lab studies, researchers in the Fram Centre Ocean Acidification Flagship test whether the fjord’s environmental gradients can serve as natural analogues for future, more acidic marine conditions.

Arctic glacial fjords, such as Kongsfjorden, have strong environmental gradients in salinity, sedimentation, primary production, and biogeochemistry. Because of glacial meltwater input, the inner fjord area becomes fresher, and suspended sediments reduce light transmission into the water column, thus restricting primary production. Sediment gradients along the fjord axis exist in Kongsfjorden seasonally, but also are representative of future changes: due to increased run-off from land, light attenuation in the water column has increased in Kongsfjorden during the last two decades, which has resulted in less macroalgae in the deeper part (>15 m depth), where it has become too dark for their photosynthesis and growth.

As part of the Fram Centre Ocean Acidification (OA) Flagship, we started to explore the possibility of using Kongsfjorden’s environmental gradients as natural analogues for investigations on effects of climate change. The concept behind the natural analogue idea is that researchers can use existing gradients to study how organisms respond to various factors in their environment, for instance those related to climate change.

Natural analogues provide an opportunity to study changes in community or population structure and how well species can adapt to a changing environment. Parameters relevant for studying possible future ocean acidification include increases in partial pressure of CO2 (pCO2), and reduced carbonate-ion concentration ([CO32-]) and pH. Measurements have shown reduction in [CO32-]during summer in the inner part of Kongsfjorden due to freshwater input, combined with suspended glacial sediments that block sunlight, reducing the ability of phytoplankton and macroalgae to remove CO2 from the water through photosynthesis. Together, these factors help create an environmental gradient along the length of Kongsfjorden – a natural analogue that can be used to study the effects of OA.

We tested the natural analogue idea in two studies with organisms collected at various sites in Kongsfjorden (see map). The first study examined three populations of the circumpolar Arctic/subarctic amphipod Gammarus setosus in the Kongsfjorden–Krossfjorden area of Svalbard. These were examined both in the field and in the laboratory for signs of physiological stress related to changes in salinity and pCO2.

In field tests, populations subject to low salinity, and generally lower pH, showed reduced metabolic rates and cellular energy allocation (CEA), which may affect their growth and reproduction (see fact box). However, the effect of pCO2 could not be separated from the effect of salinity.

In the lab, both the lower-salinity (Blomstrandhalvøya) and higher-salinity (Ny-Ålesund) populations were exposed to ambient (400 atm) and elevated (1000 atm) pCO2 at two different salinities (23‰ and 30‰), and several physiological and energetic responses were measured. The physiological responses were consistently higher under more acidic conditions (that is, at higher pCO2), and CEA was consistently lower regardless of salinity. Fresher fjord water owing to increased glacial melting may become limiting for G. setosus, especially as temperature increases.

Despite being found naturally at salinities down to 12‰ in Kongsfjorden, the amphipod’s tolerance has been shown to decrease with increasing temperature. Thus, G. setosus may be confined to the colder inner part of glacial fjords, whereas Atlantic species, such as the boreal Gammarus oceanicus, may occupy vacant habitats. Gammarus oceanicus has a wider thermal tolerance and is already more common in the outer part of Kongsfjorden.

The other study investigated summer and winter levels of magnesium carbonate (MgCO3) in the skeleton of Arctic bryozoans. Bryozoans are colonial suspension feeders, often attached to rocks or macroalgae. They occur worldwide at broad depth ranges from abyssal to the intertidal zone. Because of their high abundance and diversity, they are considered important components of Arctic marine ecosystems and significant calcium carbonate producers. Arctic bryozoan colonies often consist of thousands of units (zooids) in most cases composed of calcite (calcium carbonate; CaCO3) with variable amounts of MgCO3. Because the magnesium (Mg) content in biogenic CaCO3 skeletons determines their solubility and mechanical properties, it is important to understand what factors control it within calcified skeletons.

The study tested whether changes in seawater chemistry due to seasonal primary production, and thus changes in carbonate-ion concentration ([CO32-]) and pH, can influence the uptake of bio-available Mg2+ into calcified skeletons of Arctic bryozoans.

If Mg content in skeletons follows seasonal variation and depth-related gradients, this could indicate environmental control of skeletal parameters.

Five bryozoan species were sampled at different depths (50, 100, 150 m) and locations in Kongsfjorden during summer and winter (see map), and the concentration of MgCO3 was determined in their calcified skeletons in the laboratory. No clear differences between summer and winter levels of skeletal MgCO3 were found despite seasonal differences in calcium carbonate saturation in the water. Nor did we detect any depth-related differences in skeletal MgCO3 content.

This suggests that Arctic bryozoans can control skeletal MgCO3 concentrations biologically. Yet the variability in MgCO3 content in skeletons from stations with different seawater parameters suggests that environmental factors can also, to some extent, shape the skeletal chemistry of Arctic bryozoans.

Both studies produced results related to effects of ocean acidification and other climate-related changes in Arctic marine organisms. Salinity appears to have effects on energy allocation in amphipods and we observed some environmentally-induced variation in bryozoans.

Lack of effects of ocean acidification, within an existing environmental range in biogeochemical variables, is also an important finding, which gives hope that these Arctic marine organisms can continue to persist in marine waters with higher pCO2. Field experiments making use of natural analogues appear promising, but must move from simpler gradient-type studies to include more complex spatial-temporal mosaics of environmental drivers.

These need to be backed up by laboratory experiments, as was done in the amphipod study, to further deduce responses to environmental parameters in marine organisms. Such approaches will be critical in determining the tolerance limits of Arctic marine organisms in a higher CO2 world.


These projects were partially funded by the Fram Centre Ocean Acidification Flagship.

Locations in Kongsfjorden and Krossfjorden for collection of the three populations of Gammarus setosus (black dots) and bryozoans during winter (red) and summer (green). Land map from Norwegian Polar Institute, bathymetry from Norwegian Mapping Authority (Figure modified from Brown et al 2020; used with permission).

Framsenteret, 15 April 2021. Full article.

An analysis of community perceptions and policy responses to ocean acidification on the West Coast (text & video)

Ocean acidification disrupts the carbonate chemistry of coastal ecosystems, which indirectly and directly affects communities that depend on critical marine organisms. Ocean acidification research typically seeks to understand natural system responses; yet, there is insufficient research that examines community and institutional responses or, more generally, their vulnerability to ocean acidification. Considering the insufficient information to direct policy efforts to combat ocean acidification, this project aims to understand the Dungeness crabbers’ perceptions of the adaptive capacity of ocean acidification and other environmental stressors. By understanding the perceptions of the four coastal communities, alongside perceptions of Oregonian decision and policy makers, the project hopes to contribute to broader efforts to apply human adaptive capacity to ocean acidification.

Continue reading ‘An analysis of community perceptions and policy responses to ocean acidification on the West Coast (text & video)’

YOUmake Miami online: ocean conservation

Date and Time: 16 April 4:00 pm – 5:00 pm

Location: Online

Discover threats to our oceans and join us to brainstorm solutions to protect and clean our ocean. Participants will engage in experiments about threats such as ocean acidification, erosion and oil spills. Presented by Miami EcoAdventures. Space is limited for this online event. Registration is required. Zoom link will be emailed to registrants within 24 hours of the event start time. Ages 6 yrs.+

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Ocean acidification in the IPCC AR5 WG II

OUP book