Archive for September, 2017

New version of seacarb: functions for processing SeaFET pH data

The R package seacarb calculates parameters of the seawater carbonate system and includes functions useful for ocean acidification research. A new version is available (3.2.2). It provides two new functions for processing data from SeaFET ocean pH sensors: (1) sf_calib computes calibration coefficients using reference samples, and (2) sf_calc uses the calibration coefficients to calculate pH from voltage measurements. These functions are R-code translations from MATLAB code published by Bresnahan et al. (2014). Samir Alliouane and Lydia Kapsenberg contributed these functions to seacarb. You can check the ChangeLog, function help files, and Bresnahan et al. (2014) for more details.

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Quantifying pCO2 in biological ocean acidification experiments: A comparison of four methods

Quantifying the amount of carbon dioxide (CO2) in seawater is an essential component of ocean acidification research; however, equipment for measuring CO2 directly can be costly and involve complex, bulky apparatus. Consequently, other parameters of the carbonate system, such as pH and total alkalinity (AT), are often measured and used to calculate the partial pressure of CO2 (pCO2) in seawater, especially in biological CO2-manipulation studies, including large ecological experiments and those conducted at field sites. Here we compare four methods of pCO2 determination that have been used in biological ocean acidification experiments: 1) Versatile INstrument for the Determination of Total inorganic carbon and titration Alkalinity (VINDTA) measurement of dissolved inorganic carbon (CT) and AT, 2) spectrophotometric measurement of pHT and AT, 3) electrode measurement of pHNBS and AT, and 4) the direct measurement of CO2 using a portable CO2 equilibrator with a non-dispersive infrared (NDIR) gas analyser. In this study, we found these four methods can produce very similar pCO2 estimates, and the three methods often suited to field-based application (spectrophotometric pHT, electrode pHNBS and CO2 equilibrator) produced estimated measurement uncertainties of 3.5–4.6% for pCO2. Importantly, we are not advocating the replacement of established methods to measure seawater carbonate chemistry, particularly for high-accuracy quantification of carbonate parameters in seawater such as open ocean chemistry, for real-time measures of ocean change, nor for the measurement of small changes in seawater pCO2. However, for biological CO2-manipulation experiments measuring differences of over 100 μatm pCO2 among treatments, we find the four methods described here can produce similar results with careful use.

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XPRIZE Big Ocean Button Challenge – vote for the best app

The Big Ocean Button Challenge sponsored by the XPRIZE Ocean Initiative, is an app competition to advance development in ocean data sets in categories such as Fishing, Shipping and Trade, Ocean Acidification, Public Safety and Exploration. XPRIZE has received 20 submissions that are now competing for $100,000 in prizes.

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Using multiple lines of evidence to assess the risk of ecosystem collapse

Effective ecosystem risk assessment relies on a conceptual understanding of ecosystem dynamics and the synthesis of multiple lines of evidence. Risk assessment protocols and ecosystem models integrate limited observational data with threat scenarios, making them valuable tools for monitoring ecosystem status and diagnosing key mechanisms of decline to be addressed by management. We applied the IUCN Red List of Ecosystems criteria to quantify the risk of collapse of the Meso-American Reef, a unique ecosystem containing the second longest barrier reef in the world. We collated a wide array of empirical data (field and remotely sensed), and used a stochastic ecosystem model to backcast past ecosystem dynamics, as well as forecast future ecosystem dynamics under 11 scenarios of threat. The ecosystem is at high risk from mass bleaching in the coming decades, with compounding effects of ocean acidification, hurricanes, pollution and fishing. The overall status of the ecosystem is Critically Endangered (plausibly Vulnerable to Critically Endangered), with notable differences among Red List criteria and data types in detecting the most severe symptoms of risk. Our case study provides a template for assessing risks to coral reefs and for further application of ecosystem models in risk assessment.

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Components of a flexible phenotype in two species of scleractinian coral under ocean acidification

A developmental reaction norm integrates three tightly linked factors of ontogeny, genotype, and environment to address the ability of an organism to deal with environmental change. This concept of organismic flexibility is termed plasticity, and is well characterized in coral reef systems. However, there has been little quantification of how phenotypic plasticity in scleractinian corals may modulate their response to ocean acidification. This thesis consists of two studies addressing the role of ontogeny, genotype, and environment as influences on phenotypic complexity in scleractinian corals that may affect their response to ocean acidification. In Chapter 2, to address ontogeny, I investigated the effects of elevated pCO2 on the movement and behavior of brooded Pocillopora damicornis larvae in Okinawa, Japan, in 2016. A change in behavior in this developmental stage may alter distribution and settlement patterns of adult colonies of P. damicornis. I found that brooded larvae freshly released from P. damicornis are able to regulate their vertical position in the seawater over at least 12 h, and that this response, likely driven by a combination of modified buoyancy and active swimming, is affected by high pCO2. A change in vertical position of larvae due to elevated pCO2 has the potential to mediate pelagic larval duration (PLD) by determining their exposure to differing horizontal strata of water, thereby mediating the extent of larval connectivity among populations. In Chapter 3, to address genotype and environment, I first observed the effect of genotype-specific variation within adult colonies of P. damicornis in their growth response to elevated pCO2 in Moorea, French Polynesia, in 2016. In this preliminary experiment, I found differences among genotypes in mean growth rate that varied among trials conducted in different months, likely due to the environmental history of the corals. To quantify plasticity in two different environments, I conducted an experiment in 2017 that investigated how a plastic response in a coral to an environment change might modulate success in a fitness trait under elevated pCO2. I quantified plasticity using a suite of morphological traits in Pocillopora verrucosa at two different depths, and measured growth of plastic genotypes in high pCO2. Results suggest that genotype-specific morphological plasticity does not influence success in growth in high pCO2. Overall, the goal of this thesis was to better understand the scope of a coral’s ability to deal with environmental heterogeneity (e.g. increasing ocean acidity) based on the formation and flexibility of its phenotype. Results indicate that under projected ocean acidification conditions, the formation of a coral’s phenotype (e.g. larval behavior) will be affected by high pCO2, but that a flexible phenotype in adult corals does not appear to modulate growth success in high pCO2.

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Ecological performance of construction materials subject to ocean climate change

Artificial structures will be increasingly utilized to protect coastal infrastructure from sea-level rise and storms associated with climate change. Although it is well documented that the materials comprising artificial structures influence the composition of organisms that use them as habitat, little is known about how these materials may chemically react with changing seawater conditions, and what effects this will have on associated biota. We investigated the effects of ocean warming, acidification, and type of coastal infrastructure material on algal turfs. Seawater acidification resulted in greater covers of turf, though this effect was counteracted by elevated temperatures. Concrete supported a greater cover of turf than granite or high-density polyethylene (HDPE) under all temperature and pH treatments, with the greatest covers occurring under simulated ocean acidification. Furthermore, photosynthetic efficiency under acidification was greater on concrete substratum compared to all other materials and treatment combinations. These results demonstrate the capacity to maximise ecological benefits whilst still meeting local management objectives when engineering coastal defense structures by selecting materials that are appropriate in an ocean change context. Therefore, mitigation efforts to offset impacts from sea-level rise and storms can also be engineered to alter, or even reduce, the effects of climatic change on biological assemblages.

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Assessing the impact of ocean acidification on reef building corals

Summary
This activity introduces students to an actual data set that explores the impacts of ocean acidification on tropical coral reef ecosystems. Students are first given a scenario for a field site in the Caribbean and are asked to design an experiment that answers the question: How will a decline in surface ocean pH by the 21st century impact tropical coral growth? Students then gather actual data (from coral images collected from the field site) to calculate calcification rates of different coral samples. Finally, students use the provided saturation state values to predict the extent to which coral calcification is expected to decline by the 21st century.

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Plastic responses of bryozoans to ocean acidification

Phenotypic plasticity has the potential to allow organisms to respond rapidly to global environmental change, but the range and effectiveness of these responses are poorly understood across taxa and growth strategies. Colonial organisms might be particularly resilient to environmental stressors, as organizational modularity and successive asexual generations can allow for distinctively flexible responses in the aggregate form. We performed laboratory experiments to examine the effects of increasing dissolved carbon dioxide (i.e. ocean acidification) on the colonial bryozoan Celleporella cornuta sampled from two source populations within a coastal upwelling region of the northern California coast. Bryozoan colonies were remarkably plastic under these carbon dioxide (CO2) treatments. Colonies raised under high CO2 grew more quickly, investing less in reproduction and producing lighter skeletons when compared to genetically identical clones raised under current atmospheric values. Bryozoans held in high CO2 conditions also changed the Mg/Ca ratio of skeletal calcite and increased the expression of organic coverings in new growth, which may serve as protection against acidified water. We also observed strong differences between populations in reproductive investment and organic covering reaction norms, consistent with adaptive responses to persistent spatial variation in local oceanographic conditions. Our results demonstrate that phenotypic plasticity and energetic trade-offs can mediate biological responses to global environmental change, and highlight the broad range of strategies available to colonial organisms.

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Marine snails know how to budget their housing costs

For nearly 50 years, researchers have been stumped as to why sea shells from warm tropical waters are comparatively larger than their cold water relatives. New research, led by the ARC Centre of Excellence for Coral Reef Studies (Coral CoE) at James Cook University in Australia with researchers at British Antarctic Survey, suggests that it all comes down to ‘housing cost.’

Using an impressive data set spanning over 16,000 km, with sampling locations from the chilly Arctic waters off Svalbard, Norway to the balmy seas off Singapore, researchers found that sea snails and other calcifying marine molluscs, are frugal investors in their cost of housing and use less than 10% of their energy for shell growth.

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Transgenerational exposure of North Atlantic bivalves to ocean acidification renders offspring more vulnerable to low pH and additional stressors

While early life-stage marine bivalves are vulnerable to ocean acidification, effects over successive generations are poorly characterized. The objective of this work was to assess the transgenerational effects of ocean acidification on two species of North Atlantic bivalve shellfish, Mercenaria mercenaria and Argopecten irradians. Adults of both species were subjected to high and low pCO2 conditions during gametogenesis. Resultant larvae were exposed to low and ambient pH conditions in addition to multiple, additional stressors including thermal stress, food-limitation, and exposure to a harmful alga. There were no indications of transgenerational acclimation to ocean acidification during experiments. Offspring of elevated pCO2-treatment adults were significantly more vulnerable to acidification as well as the additional stressors. Our results suggest that clams and scallops are unlikely to acclimate to ocean acidification over short time scales and that as coastal oceans continue to acidify, negative effects on these populations may become compounded and more severe.

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