Nitrate limitation and ocean acidification interact with UV-B to reduce photosynthetic performance in the diatom

It has been proposed that ocean acidification (OA) will interact with other environmental factors to influence the overall impact of global change on biological systems. Accordingly we investigated the influence of nitrogen limitation and OA on the physiology of diatoms by growing the diatom Phaeodactylum tricornutum Bohlin under elevated (1000 µatm; high CO2- HC) or ambient (390 µatm; low CO2-LC) levels of CO2 with replete (110 µmol/L; high nitrate-HN) or reduced (10 ?mol/L; low nitrate-LN) levels of NO3- and subjecting the cells to solar radiation with or without UV irradiance to determine their susceptibility to UV radiation (UVR, 280-400 nm). Our results indicate that OA and UVB induced significantly higher inhibition of both the photosynthetic rate and quantum yield under LN than under HN conditions. UVA or/and UVB increased the cells' non-photochemical quenching (NPQ) regardless of the CO2 levels. Under LN and OA conditions, activity of superoxide dismutase and catalase activities were enhanced, along with the highest sensitivity to UVB and the lowest ratio of repair to damage of PSII. HC-grown cells showed a faster recovery rate of yield under HN but not under LN conditions. We conclude therefore that nutrient limitation makes cells more prone to the deleterious effects of UV radiation and that HC conditions (ocean acidification) exacerbate this effect. The finding that nitrate limitation and ocean acidification interact with UV-B to reduce photosynthetic performance of the diatom P. tricornutum implies that ocean primary production and the marine biological C pump will be affected by OA under multiple stressors.

Effect of simulated ocean acidification on the acute toxicity of Cu and Cd to Tigriopus japonicus

Heavy metals pollution in marine environments has caused great damage to marine biological and ecological systems. Heavy metals accumulate in marine creatures, after which they are delivered to higher trophic levels of marine organisms through the marine food chain, which causes serious harm to marine biological systems and human health. Additionally, excess carbon dioxide in the atmosphere has caused ocean acidification. Indeed, about one third of the CO2 released into the atmosphere by anthropogenic activities since the beginning of the industrial revolution has been absorbed by the world's oceans, which play a key role in moderating climate change. Modeling has shown that, if current trends in CO2 emissions continue, the average pH of the ocean will reach 7.8 by the end of this century, corresponding to 0.5 units below the pre-industrial level, or a three-fold increase in H+ concentration. The ocean pH has not been at this level for several millions of years. Additionally, these changes are occurring at speeds 100 times greater than ever previously observed. As a result, several marine species, communities and ecosystems might not have time to acclimate or adapt to these fast changes in ocean chemistry. In addition, decreasing ocean pH has the potential to seriously affect the growth, development and reproduction reproductive processes of marine organisms, as well as threaten normal development of the marine ecosystem. Copepods are an important part of the meiofauna that play an important role in the marine ecosystem. Pollution of the marine environment can influence their growth and development, as well as the ecological processes they are involved in. Accordingly, there is important scientific value to investigation of the response of copepods to ocean acidification and heavy metals pollution. In the present study, we evaluated the effects of simulated future ocean acidification and the toxicological interaction between ocean acidity and heavy metals of Cu and Cd on T. japonicus. To accomplish this, harpacticoids were exposed to Cu and Cd concentration gradient seawater that had been equilibrated with CO2 and air to reach pH 8.0, 7.7, 7.3 and 6.5 for 96 h. Survival was not significantly suppressed under single sea water acidification, and the final survival rates were greater than 93% in both the experimental groups and the controls. The toxicity of Cu to T. japonicus was significantly affected by sea water acidification, with the 96h LC50 decreasing by nearly threefold from 1.98 to 0.64 mg/L with decreasing pH. The 96 h LC50 of Cd decreased with decreasing pH, but there was no significant difference in mortality among pH treatments. The results of the present study demonstrated that the predicted future ocean acidification has the potential to negatively affect survival of T. japonicus by exacerbating the toxicity of Cu. The calculated safe concentrations of Cu were 11.9 (pH 7.7) and 10.5 (pH 7.3) µg/L, which were below the class I value and very close to the class II level of the China National Quality Standard for Sea Water. Overall, these results indicate that the Chinese coastal sea will face a

Distribution of biological, anthropogenic, and volcanic constituents in the San Francisco Bay Coastal System

Although conventional sediment parameters (mean grain size, sorting, and skewness) and provenance have typically been used to infer sediment transport pathways, most freshwater, brackish, and marine environments are also characterized by abundant sediment constituents of biological, and possibly anthropogenic and volcanic, origin that can provide additional insight into local sedimentary processes. The biota will be spatially distributed according to its response to environmental parameters such as water temperature, salinity, dissolved oxygen, organic carbon content, grain size, and intensity of currents and tidal flow, whereas the presence of anthropogenic and volcanic constituents will reflect proximity to source areas and whether they are fluvially- or aerially-transported. Because each of these constituents have a unique environmental signature, they are a more precise proxy for that source area than the conventional sedimentary process indicators. This San Francisco Bay Coastal System study demonstrates that by applying a multi-proxy approach, the primary sites of sediment transport can be identified. Many of these sites are far from where the constituents originated, showing that sediment transport is widespread in the region. Although not often used, identifying and interpreting the distribution of naturally-occurring and allochthonous biologic, anthropogenic, and volcanic sediment constituents is a powerful tool to aid in the investigation of sediment transport pathways in other coastal systems.

Seawater carbonate chemistry and biological processes of oysters Crassostrea virginica during experiments, 2010

Estuarine organisms are exposed to periodic strong fluctuations in seawater pH driven by biological carbon dioxide (CO2) production, which may in the future be further exacerbated by the ocean acidification associated with the global rise in CO2. Calcium carbonate-producing marine species such as mollusks are expected to be vulnerable to acidification of estuarine waters, since elevated CO2 concentration and lower pH lead to a decrease in the degree of saturation of water with respect to calcium carbonate, potentially affecting biomineralization. Our study demonstrates that the increase in CO2 partial pressure (pCO2) in seawater and associated decrease in pH within the environmentally relevant range for estuaries have negative effects on physiology, rates of shell deposition and mechanical properties of the shells of eastern oysters Crassostrea virginica (Gmelin). High CO2 levels (pH ~7.5, pCO2 ~3500 µatm) caused significant increases in juvenile mortality rates and inhibited both shell and soft-body growth compared to the control conditions (pH ~8.2, pCO2 ~380 µatm). Furthermore, elevated CO2 concentrations resulted in higher standard metabolic rates in oyster juveniles, likely due to the higher energy cost of homeostasis. The high CO2 conditions also led to changes in the ultrastructure and mechanical properties of shells, including increased thickness of the calcite laths within the hypostracum and reduced hardness and fracture toughness of the shells, indicating that elevated CO2 levels have negative effects on the biomineralization process. These data strongly suggest that the rise in CO2 can impact physiology and biomineralization in marine calcifiers such as eastern oysters, threatening their survival and potentially leading to profound ecological and economic impacts in estuarine ecosystems.

Seawater carbonate chemistry and biological processes of bivalve shellfish Mercenaria mercenaria and Argopecten irradians during experiments, 2011

The combustion of fossil fuels has enriched levels of CO2 in the world's oceans and decreased ocean pH. Although the continuation of these processes may alter the growth, survival, and diversity of marine organisms that synthesize CaCO3shells, the effects of ocean acidification since the dawn of the industrial revolution are not clear. Here we present experiments that examined the effects of the ocean's past, present, and future (21st and 22nd centuries) CO2concentrations on the growth, survival, and condition of larvae of two species of commercially and ecologically valuable bivalve shellfish (Mercenaria mercenariaand Argopecten irradians). Larvae grown under near preindustrial CO2concentrations (250 ppm) displayed significantly faster growth and metamorphosis as well as higher survival and lipid accumulation rates compared with individuals reared under modern day CO2 levels. Bivalves grown under near preindustrial CO2 levels displayed thicker, more robust shells than individuals grown at present CO2 concentrations, whereas bivalves exposed to CO2 levels expected later this century had shells that were malformed and eroded. These results suggest that the ocean acidification that has occurred during the past two centuries may be inhibiting the development and survival of larval shellfish and contributing to global declines of some bivalve populations.

Data compilation on the biological response to ocean acidification: environmental and experimental context of data sets and related literature

The exponential growth of studies on the biological response to ocean acidification over the last few decades has generated a large amount of data. To facilitate data comparison, a data compilation hosted at the data publisher PANGAEA was initiated in 2008 and is updated on a regular basis (doi:10.1594/PANGAEA.149999). By January 2015, a total of 581 data sets (over 4 000 000 data points) from 539 papers had been archived. Here we present the developments of this data compilation five years since its first description by Nisumaa et al. (2010). Most of study sites from which data archived are still in the Northern Hemisphere and the number of archived data from studies from the Southern Hemisphere and polar oceans are still relatively low. Data from 60 studies that investigated the response of a mix of organisms or natural communities were all added after 2010, indicating a welcomed shift from the study of individual organisms to communities and ecosystems. The initial imbalance of considerably more data archived on calcification and primary production than on other processes has improved. There is also a clear tendency towards more data archived from multifactorial studies after 2010. For easier and more effective access to ocean acidification data, the ocean acidification community is strongly encouraged to contribute to the data archiving effort, and help develop standard vocabularies describing the variables and define best practices for archiving ocean acidification data.

Seawater carbonate chemistry and biological processes during experiments with oyster Crassostrea gigas, 2009

An increasing number of studies are now reporting the effects of ocean acidification on a broad range of marine species, processes and systems. Many of these are investigating the sensitive early life-history stages that several major reviews have highlighted as being potentially most susceptible to ocean acidification. Nonetheless there remain few investigations of the effects of ocean acidification on the very earliest, and critical, process of fertilization, and still fewer that have investigated levels of ocean acidification relevant for the coming century. Here we report the effects of near-future levels of ocean acidification (?0.35 pH unit change) on sperm swimming speed, sperm motility, and fertilization kinetics in a population of the Pacific oyster Crassostrea gigas from western Sweden. We found no significant effect of ocean acidification - a result that was well-supported by power analysis. Similar findings from Japan suggest that this may be a globally robust result, and we emphasise the need for experiments on multiple populations from throughout a species' range. We also discuss the importance of sound experimental design and power analysis in meaningful interpretation of non-significant results.

Experiment: Acidified seawater impacts sea urchin larvae pH regulatory systems relevant for calcification

Calcifying echinoid larvae respond to changes in seawater carbonate chemistry with reduced growth and developmental delay. To date, no information exists on how ocean acidification acts on pH homeostasis in echinoderm larvae. Understanding acid-base regulatory capacities is important because intracellular formation and maintenance of the calcium carbonate skeleton is dependent on pH homeostasis. Using H(+)-selective microelectrodes and the pH-sensitive fluorescent dye BCECF, we conducted in vivo measurements of extracellular and intracellular pH (pH(e) and pH(i)) in echinoderm larvae. We exposed pluteus larvae to a range of seawater CO(2) conditions and demonstrated that the extracellular compartment surrounding the calcifying primary mesenchyme cells (PMCs) conforms to the surrounding seawater with respect to pH during exposure to elevated seawater pCO(2). Using FITC dextran conjugates, we demonstrate that sea urchin larvae have a leaky integument. PMCs and spicules are therefore directly exposed to strong changes in pH(e) whenever seawater pH changes. However, measurements of pH(i) demonstrated that PMCs are able to fully compensate an induced intracellular acidosis. This was highly dependent on Na(+) and HCO(3)(-), suggesting a bicarbonate buffer mechanism involving secondary active Na(+)-dependent membrane transport proteins. We suggest that, under ocean acidification, maintained pH(i) enables calcification to proceed despite decreased pH(e). However, this probably causes enhanced costs. Increased costs for calcification or cellular homeostasis can be one of the main factors leading to modifications in energy partitioning, which then impacts growth and, ultimately, results in increased mortality of echinoid larvae during the pelagic life stage.