Archive for October, 2017

High-level workshop discusses ocean acidification and coral reefs

Corals

While coral reefs represent less than 0.2% of the total surface of the oceans, they have major ecological importance as they provide habitats for over 30% of all marine fauna. (Photo: P. Swarzenski/IAEA)

The IAEA, through its Environment Laboratories organised, in partnership with the Scientific Centre of Monaco (CSM), a workshop on ocean acidification, which this year focused on the impact on ecosystem services and coral reefs. With sixty participants from twenty-two countries including HSH Prince Albert II of Monaco it aimed to bring the global discussion from sciences to solutions.

Recent research, including that done by the IAEA, shows that ocean acidification effects on fisheries, aquaculture and coral reefs are expanding, both in terms of geographical location and intensity. Some effects are direct such as on species’ physiology: growth, reproduction and calcification, while others may be indirect: e.g. impact on food sources, habitat degradation, changes in the food chain structure etc.

Continue reading ‘High-level workshop discusses ocean acidification and coral reefs’

Taphonomy and evolution of Lower Jurassic lithiotid bivalve accumulations in the Apennine Carbonate Platform (southern Italy)

Highlights

• A description of Lower Jurassic lithiotid taphofacies in the Apennine Carbonate Platform
• A spectacular record of the appearance, flourishing and demise of the lithiotids
Cochlearites and Mytiloperna dominate with subordinate Lithioperna.
• The rock-forming importance of lithiotids decreases near the Pl-To boundary.
• The sudden demise of lithiotids occurs at the onset of the T-OAE.

Abstract

Lower Jurassic Tethyan and Panthalassan marine shallow-water successions are characterized by aberrant lithiotid bivalves belonging to the Lithiotis Fauna. Their widespread occurrence, often in rock-forming abundance, represents a global biofacies, mostly restricted to the Pliensbachian–early Toarcian. Despite their wide occurrence and their prominent role as carbonate producers in shallow-water platforms, the biogeographic and stratigraphic distribution of this group of bivalves and their evolutionary history are obscure, mostly because they commonly have not been identified at the generic or specific level. In particular, their evolution and demise in relation to important global palaeoenvironmental perturbations, such as the Pliensbachian-Toarcian boundary event and the early Toarcian oceanic anoxic event are not yet known in detail.

In the Apennine Carbonate Platform of southern Italy, the Lithiotis Member, in the upper part of the Lower Jurassic Palaeodasycladus Limestones Formation, is characterized by the abundant occurrence of lithiotid bivalves. They disappear abruptly in the lowermost beds of the overlying Oolitic-oncolitic Limestones Formation, at the onset of the early Toarcian Oceanic Anoxic Event. More than 60 lithiotid bivalve concentrations occur in a nearly 120m-thick succession spectacularly exposed on freshly cut walls in a quarry west of Mercato San Severino (Salerno). Field observations on the taxonomic composition and fabric of the shell beds (packing, maximum shell size, degree of shell articulation and fragmentation) allowed to distinguish four taphofacies (A–D). Taphofacies A records the appearance and spreading of the lithiotids, with accumulations characterized mainly by small-sized and loosely packed shells. Taphofacies B records the acme of lithiotid bivalves, with densely packed accumulations of large shells. These two taphofacies yield prevailing articulated individuals, commonly in life position. Taphofacies C records a decrease of the shell packing and frequency of articulated shells. However, it is not clear whether this represents the beginning of a prolonged crisis or just the local response to less favourable environmental conditions around a sequence boundary. Taphofacies D consists of three shell beds, one in the uppermost part of the Lithiotis Member and two within the lowermost part of the Oolitic-oncolitic Limestones Formation, in the stratigraphic interval characterized by the negative carbon isotope excursion of the early Toarcian OAE. The bivalve shells of these two beds consist exclusively of disarticulated and fragmented shells, possibly reworked from underlying levels. The demise of the lithiotids carbonate factory in the Apennine Carbonate Platform and the extinction of the largest aberrant bivalves of the Lithiotis Fauna at the onset of the early Toarcian anoxic event were probably due to the physiological stress imposed by ocean acidification and increased nutrient input.

 

Continue reading ‘Taphonomy and evolution of Lower Jurassic lithiotid bivalve accumulations in the Apennine Carbonate Platform (southern Italy)’

Marine metal pollution and effects on seaweed species

Heavy metals are significant pollutants continuously released into the biosphere, both naturally and anthropogenically. Conceptually, metal speciation, bioavailability, and associated toxicity in marine organisms depend on a wide array of abiotic and biotic factors. Among these, pH variation is one of the most important environmental factors influencing metal speciation and toxicity. Due to this, ocean acidification is expected to modify metal speciation, altering the effects these nondegradable contaminants have on marine organisms, such as seaweeds. One clear effect of heavy metals on seaweeds is the rapid formation of reactive oxygen species (ROS). The production of ROS beyond the physiological tolerance threshold causes an oxidative stress condition that, if not attenuated, can irreversibly damage cellular constituents such as DNA/RNA, proteins, and lipids. To cope with heavy metal excess, several mechanisms exist in tolerant seaweed species, including the activation of an efficient ROS-scavenging system constituted by metal-binding compounds, antioxidant enzymes, and oxygenated polyunsaturated fatty acids, among others. Another adaptive mechanism involves the participation of ATP-binding cassette (ABC) transporter proteins in translocating a wide variety of compounds across cell membranes, including heavy metals. In contrast, an excessive heavy metal presence can inhibit photosynthesis, reduce pigment concentration and growth, induce cation losses, and disrupt gametophyte development in non-tolerant seaweed species. In a scenario of lowered ocean pH and increased heavy metal toxicity, the important roles played by non-tolerant seaweed species in structuring communities could be severely compromised, with unknown consequences for associated organisms. Therefore, in the upcoming decades, marine pollution could majorly shift and rearrange community compositions and the distributional ranges of species.

Continue reading ‘Marine metal pollution and effects on seaweed species’

ICOAE 2018 : 20th International Conference on Ocean Acidification and Environment

Venice, Italy, February 8 – 9, 2018

Abstracts/Full-Text Paper Submission Deadline: November 17, 2017

Conference Aims and Objectives

The ICOAE 2018: 20th International Conference on Ocean Acidification and Environment aims to bring together leading academic scientists, researchers and research scholars to exchange and share their experiences and research results on all aspects of Ocean Acidification and Environment. It also provides a premier interdisciplinary platform for researchers, practitioners and educators to present and discuss the most recent innovations, trends, and concerns as well as practical challenges encountered and solutions adopted in the fields of Ocean Acidification and Environment.

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Ocean acidification & hypoxia research findings

Date: November 18, 2017

Address: 2400 Hwy 101, Yachats, OR 97498 USA
Time: 1:00 PM

The rocky intertidal habitats in the Cape Perpetua Marine Reserve are a hotspot of biodiversity. Scientists have been monitoring the dynamics and intertidal species here for decades. In addition, scientists have been conducting oceanography, hypoxia and ocean acidification studies in this area since the early 2000s. Steven Rumrill, Shellfish Program Lead and Daniel Sund, Ocean Acidification and Hypoxia researcher with the Oregon Department of Fish and Wildlife Marine Reserves Program will present research related to ocean acidification along the Pacific Coast and its potential impact on coastal ecosystems.

Further information.

The effects of ocean acidification on growth, photosynthesis, and domoic acid production by the toxigenic diatom Pseudo-nitzschia australis

A northern California strain of Pseudo-nitzschia australis was examined using nonaxenic, batch cultures to examine the effects of more acidic conditions (reduced pH due to increased pCO2) on the growth, photosynthesis, and domoic acid production of this toxigenic diatom. Specific growth rates at the lowest pH tested (7.8) were 30 percent lower than the other three pH treatments (8.1, 8.0, 7.9). Macronutrient drawdown ratios of Si:N and Si:P decreased linearly with declining pH. Maximum rates of photosynthesis per cell were significantly elevated in the two lowest pH treatments relative to the control pH of 8.1. Domoic acid (DA) was detected in all pH treatments during both the nutrient-replete exponential growth phase and the nutrient-deplete stationary growth phase. Total cellular DA did not significantly differ among pH treatments during exponential growth, but increased with decreasing pH and reached a maximum of 3.61 pg DA • cell”1 during the stationary phase of growth.

Continue reading ‘The effects of ocean acidification on growth, photosynthesis, and domoic acid production by the toxigenic diatom Pseudo-nitzschia australis’

Reef-scale modeling of coral calcification responses to ocean acidification and sea-level rise

To predict coral responses to future environmental changes at the reef scale, the coral polyp model (Nakamura et al. in Coral Reefs 32:779–794, 2013), which reconstructs coral responses to ocean acidification, flow conditions and other factors, was incorporated into a reef-scale three-dimensional hydrodynamic-biogeochemical model. This coupled reef-scale model was compared to observations from the Shiraho fringing reef, Ishigaki Island, Japan, where the model accurately reconstructed spatiotemporal variation in reef hydrodynamic and geochemical parameters. The simulated coral calcification rate exhibited high spatial variation, with lower calcification rates in the nearshore and stagnant water areas due to isolation of the inner reef at low tide, and higher rates on the offshore side of the inner reef flat. When water is stagnant, bottom shear stress is low at night and thus oxygen diffusion rate from ambient water to the inside of the coral polyp limits respiration rate. Thus, calcification decreases because of the link between respiration and calcification. A scenario analysis was conducted using the reef-scale model with several pCO2 and sea-level conditions based on IPCC (Climate change 2013: the physical science basis. Contribution of working group I to the fifth assessment report of the intergovernmental panel on climate change, Cambridge University Press, Cambridge, 2013) scenarios. The simulation indicated that the coral calcification rate decreases with increasing pCO2. On the other hand, sea-level rise increases the calcification rate, particularly in the nearshore and the areas where water is stagnant at low tide under present conditions, as mass exchange, especially oxygen exchange at night, is enhanced between the corals and their ambient seawater due to the reduced stagnant period. When both pCO2 increase and sea-level rise occur concurrently, the calcification rate generally decreases due to the effects of ocean acidification. However, the calcification rate in some inner-reef areas will increase because the positive effects of sea-level rise offset the negative effects of ocean acidification, and total calcification rate will be positive only under the best-case scenario (RCP 2.6).

Continue reading ‘Reef-scale modeling of coral calcification responses to ocean acidification and sea-level rise’

Ocean acidification could doom key Arctic fish species: study

Ocean acidification combined with warming of the world oceans and loss of oxygen is having a severe impact on key Arctic marine species such as polar cod in the Barents Sea, according to a new study conducted by German scientists.

Continue reading ‘Ocean acidification could doom key Arctic fish species: study’

Effect of ocean acidification on the ecology of two tropical crustose coralline algae (phylum Rhodophyta)

Crustose coralline algae (CCA) are important members of coral reef communities. They accrete and consolidate the calcium carbonate framework of coral reefs, and some species are an important settlement substratum for coral larvae. CCA community composition is shaped, at least in part, by herbivory and competition. However, ocean acidification (OA) is negatively affecting CCA, with potential to affect CCA responses to herbivory (wounding) and their ability to compete for space. Changes in seawater chemistry because of OA cause reductions in the recruitment, abundance, and net calcification of CCA. In this thesis, the effects of OA on net calcification, regeneration of wounds, and competition was quantified for two species of CCA common in the back reefs of Mo’orea, French Polynesia; Porolithon onkodes and Lithophyllum insipidum. Three separate experiments were conducted in four flowing seawater tanks (flumes), each set to a different target pCO2 level representative of ambient (~ 400 µatm) or predicted end of the 21 century pCO2 (~ 700, 1000, and 1300 µatm). P. onkodes, was found to be the most abundant species of CCA in the back reefs of Mo’orea, followed by L. flavescens and L. insipidum. The abundance of P. onkodes is likely a direct result of its competitive ability. P. onkodes is thicker on average than the other common CCA in the back reefs of Mo’orea, and thicker species generally become dominant in areas of intense herbivory, such as coral reefs. In a flume experiment conducted from January to March 2016, net calcification declined 85% in P. onkodes at elevated pCO2 compared to a decline of 42% in L. insipidum, indicating that P. onkodes may be more negatively affected by OA. The differential responses to OA found here could alter the outcome of competitive interactions between P. onkodes and L. insipidum, leading to changes in the abundances of these species in CCA communities. Few studies have quantified the potential for OA to interact with natural disturbances, such as wounding of the thallus by herbivores. A flume experiment conducted from May to July 2016 found that there was a 58% reduction in the rate of vertical regeneration of artificial wounds within P. onkodes at elevated pCO2. This result could have important implications for the response of P. onkodes to grazing by excavating herbivores like parrotfish and sea urchins. Inability for CCA to recover from wounding, could increase the susceptibility of CCA to further wounding. In addition, the reductions in vertical regeneration of the wounds could also be indicative of reduced vertical growth rates. CCA with thicker thalli generally outcompete thinner CCA. Reduced vertical growth rates could reduce thallus thickness, and affect the outcome of competitive interactions among CCA. A flume experiment conducted from June to July 2016 found that there was no effect of elevated pCO2 on the outcome of competitive interactions between P. onkodes and L. insipidum. It is likely that this result may have been due to the relatively short duration of this experiment (one month). There was, however, an effect of the identity of the competitor on the proportion of live tissue remaining in focal individuals of P. onkodes. The proportion of live tissue remaining in focal individuals of P. onkodes was significantly lower in intraspecific pairings than in interspecific pairings or when paired with non-living substrate (controls). This result highlights the importance of including both intraspecific and interspecific interactions in future studies of the effects of OA on competition. Experiments of longer durations may elucidate the potential for elevated pCO2 to affect competition among CCA. CCA are ecologically important members of coral reefs. Changes in the community composition of CCA on coral reefs, because of altered competitive abilities under elevated pCO2, could affect the roles that CCA play in building and maintain coral reef ecosystems.

Continue reading ‘Effect of ocean acidification on the ecology of two tropical crustose coralline algae (phylum Rhodophyta)’

Changes in bioenergetics associated with ocean acidification and climate changes

Ocean global changes, including CO2-triggered ocean acidification and warming as well as associated changes in physical and chemical environments affect metabolisms of marine organisms and increase their energetic demand to cope with the environmental stresses. Phytoplankton species grown under ocean acidification conditions alter their metabolic pathways, down-regulating their CO2 concentrating mechanisms, up-regulating photorespiration and heatdissipating processes and generating extra energy by degrading accumulated phenolic compounds, which are toxic and can be transferred to higher trophic levels, changing food quality. Calcifying algae, under influence of ocean acidification, need more energy to maintain their calcification and to synthesize UV screening compounds due to reduced thickness of the calcified “shell”. Changes in the bioenergetics with exacerbating ocean global environmental issues will lead to ecological consequences and affect services of marine ecosystems.

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