Archive for April, 2017



Human dimensions of environmental change in small island developing states: some common themes

Climate change and its consequence of sea level rise are major issues for small island developing states (SIDS), as they worsen many other pressures on their people and their environment. Accordingly, articles in this special issue of Regional Environmental Change on SIDS address research gaps in the following thematic areas of the human dimensions of climate change. (1) Islander perceptions of climate change and the information sources on which these are based. (2) Migration to richer countries, which dominates popular media articles, so that scholars from a wide range of disciplines have given their perspectives on it. For many SIDS, however, relocation within that country is much more of an issue, but little studied as yet. (3) Community-based adaptation, a theme which only rarely appears in peer-reviewed journals. (4) National, regional and international policies and the effectiveness of their implementation. (5) Social and cultural issues arising from the above. This paper provides an overview of these and some related themes of importance to SIDS, including ocean acidification and land degradation. Researchers based in the SIDS and regional organisations have an important role in recognising these issues and in developing the local skills base needed to deal with them. The Paris Agreement of 2015 is a positive (but as yet inadequate) step towards the international action on climate change that SIDS need.

Continue reading ‘Human dimensions of environmental change in small island developing states: some common themes’

Calcareous nannoplankton response to the latest Cenomanian Oceanic Anoxic Event 2 perturbation

Morphometric analyses were performed on Biscutum constans, Zeugrhabdotus erectus, Discorhabdus rotatorius and Watznaueria barnesiae specimens from five sections spanning the Cenomanian-Turonian boundary interval including Oceanic Anoxic Event (OAE) 2 (~ 94 Ma). The study provides evidence for size fluctuations and dwarfism of B. constans during OAE 2, followed by a partial recovery at the end of the event: this taxon appears to be the most sensitive species, with similar and coeval size trends in all the analyzed sections. Conversely, morphometry shows negligible or unsystematic coccolith variations in Z. erectus, D. rotatorius and W. barnesiae. The comparison of OAE 2 data with those available for the early Aptian OAE 1a and latest Albian OAE 1d, indicates that B. constans repeatedly underwent size reduction and temporary dwarfism possibly implying that the same paleoenvironmental factors controlled calcification of B. constans during subsequent OAEs although the amplitude of B. constans coccolith reduction is significantly larger for OAE 1a than OAE 2. Paleoceanographic reconstructions suggest that ocean chemistry related to the amount of CO2 and toxic metal concentrations played a central role in B. constans coccolith secretion, while temperature and nutrient availability do not seem to have been crucial. Contrary to OAE 1a, Z. erectus, D. rotatorius and W. barnesiae appear to be substantially unrelated to OAE 2 paleoenvironmental stress, possibly because of different degrees of perturbation.

Continue reading ‘Calcareous nannoplankton response to the latest Cenomanian Oceanic Anoxic Event 2 perturbation’

Elevated temperature has adverse effects on GABA-mediated avoidance behaviour to sediment acidification in a wide-ranging marine bivalve

Sediment acidification is known to influence the burrowing behaviour of juvenile marine bivalves. Unlike the alteration of behaviour by ocean acidification (OA) observed in many marine organisms, this burrowing response to present-day variation in sediment pH is likely adaptive in that it allows these organisms to avoid shell dissolution and mortality. However, the consequences of global climate stressors on these burrowing responses have yet to be tested. Further, while neurotransmitter interference appears to be linked to the alteration of behaviour by OA in marine vertebrates, the mechanism(s) controlling the burrowing responses of juvenile bivalves in response to present-day variation in sediment acidification remain unknown. We tested the interactive effects of elevated seawater temperature and sediment acidification on juvenile soft-shell clam burrowing behaviour (measured as the proportion of clams burrowed into sediment) to test for effects of elevated temperature on bivalve burrowing responses to sediment acidification. We also examined whether GABAA-like receptor interference could act as a potential biological mechanism underpinning the burrowing responses of these clams to present-day variation in sediment acidification. Results showed that both elevated temperature and gabazine administration reduced the proportion of clams that avoided burrowing into low pH sediment. These results suggest that CO2 effects on neurophysiology (GABAA receptors) can act to mediate adaptive behaviours in juvenile marine bivalves to elevated CO2, but that these behaviours may be adversely affected by elevated temperature.

Continue reading ‘Elevated temperature has adverse effects on GABA-mediated avoidance behaviour to sediment acidification in a wide-ranging marine bivalve’

Achieving accurate spectrophotometric pH measurements using unpurified meta-cresol purple

For best accuracy, spectrophotometric characterizations of seawater pH are obtained using a purified pH-sensitive dye—usually meta-cresol purple (mCP) for typical ranges of seawater pH. In recognition of practical limitations, though, a straightforward method is here proposed to improve measurements made using unpurified mCP. The user first determines, for a particular lot of unpurified mCP, the absorbance contribution of indicator impurities at 434 nm (434Aimp). Correction for this contribution is then mathematically applied to the measurements of seawater pH. We tested this approach using six unpurified lots of mCP and, for comparison, purified mCP in a synthetic experimental solution over the pH range 7.25–8.25. The 434Aimp correction yielded substantial improvements in pH accuracy: on the order of 0.005 at low pH (~ 7.25) and 0.01 or more at higher pH (~ 8.25). The pH accuracy achieved by the corrective model was also examined relative to the Global Ocean Acidification Observing Network (GOA-ON) “weather” and “climate” goals for pH measurements (uncertainties of ± 0.02 and ± 0.003, respectively). When previously published algorithms (appropriate for purified mCP) were used, none of the unpurified dyes met the more stringent “climate” goal in waters of pH > 7.6. With the algorithms proposed here (i.e., incorporating the lot-specific 434Aimp correction), three of the six lots came into “climate” compliance over the full experimental pHT range and two additional lots achieved “climate” compliance up to pH ~ 8.0. This protocol offers a simple, user-determined correction to significantly improve the accuracy of pH measurements made with unpurified mCP.

Continue reading ‘Achieving accurate spectrophotometric pH measurements using unpurified meta-cresol purple’

Lower Nehalem Watershed Council Speaker Series: Ocean Acidification, 11 May 2017

Date & Location: 11 May 2017, Pine Grove Community House (225 Laneda Ave, Manzanita)

Ocean acidification is a global challenge to the sustainability of marine ecosystems. It is a major water quality issue linked to the reduction of shell material in our coastal waters and the mortality of shell forming marine life worldwide. Oregon has emerged as ground zero for ocean acidification science, policy making and actions. Join Lower Nehalem Watershed Council and co-host, Friends of Cape Falcon Marine Reserve, in welcoming Dr. Francis Chan for a presentation on this important issue. Chan will share about the evolving understanding of the geography of ocean acidification and ecological vulnerability. His presentation will also discuss the role of marine reserves and the local community in advancing the states understanding of ocean acidification impacts within our coastal waters as well as policy efforts and actions that are underway to address the challenges ahead.

The presentation will be held on Thursday, May 11, at the Pine Grove Community House (225 Laneda Ave) in Manzanita. Doors open at 6:30 p.m. for refreshments. The presentation will start at 7:20 p.m. following an update from Lower Nehalem Watershed Council at 7:00 p.m.

Continue reading ‘Lower Nehalem Watershed Council Speaker Series: Ocean Acidification, 11 May 2017’

Large-scale seaweed cultivation diverges water and sediment microbial communities in the coast of Nan’ao Island, South China Sea

Seaweed cultivation not only provides economy benefits, but also remediates the environment contaminated by mariculture of animals (e.g., fish, shrimps). However, the response of microbial communities to seaweed cultivation is poorly understood. In this study, we analyzed the diversity, composition, and structure of water and sediment microbial communities at a seaweed, Gracilaria lemaneiformis, cultivation zone and a control zone near Nan’ao Island, South China Sea by MiSeq sequencing of 16S rRNA gene amplicons. We found that large-scale cultivation of G. lemaneiformis increased dissolved oxygen (DO) and pH but decreased inorganic nutrients, possibly due to nutrient uptake, photosynthesis and other physiological processes of G. lemaneiformis. These environmental changes significantly (adonis, P < 0.05) shifted the microbial community composition and structure of both water column and sediment samples in the G. lemaneiformis cultivation zone, compared to the control zone. Also, certain microbial taxa associated with seaweed, such as Arenibacter, Croceitalea, Glaciecola, Leucothrix and Maribacter were enriched at the cultivation zone. In addition, we have proposed a conceptual model to summarize the results in this study and guide future studies on relationships among seaweed processes, microbial communities and their environments. Thus, this study not only provides new insights into our understanding the effect of G. lemaneiformis cultivation on microbial communities, but also guides future studies on coastal ecosystems.

Continue reading ‘Large-scale seaweed cultivation diverges water and sediment microbial communities in the coast of Nan’ao Island, South China Sea’

Effects of elevated CO₂ on speckled sanddab (Citharichthys stigmaeus) behaviour

The direct and indirect effects of ocean acidification (OA) are a growing concern, particularly in areas already experiencing elevated levels of oceanic CO₂. Studies with marine fishes suggest that elevated CO₂ levels may affect behavior by interfering with an important brain neurotransmitter. Studies examining the effects of OA fish behavior have been predominately conducted on tropical fishes; few have been conducted on fishes from temperate and boreal regions. The productive ecosystems of these regions, such as those of the California Current, support important commercial fisheries. Parts of the California Current are already experiencing elevated CO₂ during seasonal upwelling events. Flatfishes are an important component of the ecosystems of the California Current; not only do flatfishes support important regional fisheries, but they also are an important link in energy transfer within marine food webs. To date there has been little work examining the effects of OA on flatfish behavior. In laboratory experiments, I first examined speckled sanddab (Citharichthys stigmaeus) behavioral responses to potential predation cues (predator odor, damaged skin cues from injured conspecifics, and sight of a predator) under ambient CO₂ conditions. Whereas sanddab exhibited reductions in conspicuousness and foraging following exposure to the sight of a predator, they increased activity and foraging following exposure to damaged skin cues from injured conspecifics. I then examined the effects of elevated CO₂ levels on posture, activity, and foraging of sanddab, and if CO₂ altered their responses to damaged skin cues. CO₂ treatments reflected present-day CO₂ levels (~ 400μatm) and those predicted to occur over the next 150 years (~1,000 μatm and ~1,600 μatm). While there was no major effect of CO₂ treatment on the behavior of speckled sanddab, there were non-significant trends of fish from the medium CO₂ treatment exhibiting the lowest posture and activity scores, longest feeding latencies, and fewest feeding strikes. Results suggest that aspects of speckled sanddab behavior might resistant to OA. It is also possible that prolonged exposure to elevated CO₂ enabled speckled sanddab to compensate, mitigating the effects observed in other fishes following shorter-term exposure to elevated CO₂. Experiments further examining the interactive effects of elevated CO₂ with other environmental conditions on speckled sanddab behavior can also provide insight into the potential ecological consequences of life in an ocean altered by global climate change. Additional studies of ecologically relevant behaviors across diverse species assemblages will be needed to evaluate the impact of ocean acidification on marine food webs.

Continue reading ‘Effects of elevated CO₂ on speckled sanddab (Citharichthys stigmaeus) behaviour’

Inorganic carbon physiology underpins macroalgal responses to elevated CO2

Beneficial effects of CO2 on photosynthetic organisms will be a key driver of ecosystem change under ocean acidification. Predicting the responses of macroalgal species to ocean acidification is complex, but we demonstrate that the response of assemblages to elevated CO2 are correlated with inorganic carbon physiology. We assessed abundance patterns and a proxy for CO2:HCO3− use (δ13C values) of macroalgae along a gradient of CO2 at a volcanic seep, and examined how shifts in species abundance at other Mediterranean seeps are related to macroalgal inorganic carbon physiology. Five macroalgal species capable of using both HCO3− and CO2 had greater CO2 use as concentrations increased. These species (and one unable to use HCO3−) increased in abundance with elevated CO2 whereas obligate calcifying species, and non-calcareous macroalgae whose CO2 use did not increase consistently with concentration, declined in abundance. Physiological groupings provide a mechanistic understanding that will aid us in determining which species will benefit from ocean acidification and why.

Continue reading ‘Inorganic carbon physiology underpins macroalgal responses to elevated CO2’

Sea creature dissolves fast in warm, acidic ocean

Marine animals that live in warm as well as acidic oceans are dissolving quickly under conditions at the Northern California coast, says a study from the University of California, Davis. This applies especially to the bryozoans.

Scientists published their study in the journal Proceedings of the Royal Society B: Biological Sciences. Researchers from the UC Davis Bodega Marine Laboratory raised bryozoans, more commonly called “moss animals” in seawater tanks. They exposed them to different levels of water temperature, food, and acidity.

Growing them in warm waters and then exposing them to acidity dissolved the bryozoans quickly. Large parts of their skeletons got dissolved in just two to three months, according to Science Daily. Even though they expected some thinning or reduced mass, lead author Dan Swezey, a recent Ph.D. graduate in professor Eric Sanford’s lab at the UC Davis Bodega Marine Laboratory said that they witnessed entire features just dissolving in front of their eyes!

Continue reading ‘Sea creature dissolves fast in warm, acidic ocean’

Effect of pH on temperature controlled degradation of reactive oxygen species, heat shock protein expression, and mucosal immunity in the sea cucumber Isostichopus badionotus

This study evaluated the effect of pH on the activity of antioxidant and immune enzymes in the sea cucumber Isostichopus badionotus exposed to different temperatures. The organisms (530 ±110 g) were exposed to 16, 20, 24, 28, 30, 34 and 36°C for 6 h to evaluate thermal limits at two water pH values (treatment = 7.70; control = 8.17). For the thermal tolerance experiment, the organisms were exposed to sublethal temperature of 34°C for 3, 6, 12, 24, and 48 h. I. badionotus showed signs of thermal stress by synthesizing heat shock protein 70 (hsp70) at the cold (16°C) and warm thermal limits (34°C). The glutathione peroxidase (GPx) showed a negative correlation with superoxide dismutase (SOD) activity in modulating the effect of oxidative stress at different temperature levels. Specifically, GPx activity was maximal at the extremes of the cold and warm temperatures (16, 20, and 36°C) tested, while contrarily, the SOD activity increased significantly in the narrow range of temperature between 28 and 30°C, as a part of a reaction to offset oxidative damage. The effect of pH on the expression of hsp70 was not significant, whereas the antioxidant enzymes activity was stimulated at pH 7.70. Mucosal immunity, evidenced by the activation of the phenoloxidase (PO) system, increased above the basal level at pH 7.70 and at 28, 30, and 34°C. Independent of pH, the temperature of 34°C was identified as the 12 h-sublethal upper limit for I. badionotus.

Continue reading ‘Effect of pH on temperature controlled degradation of reactive oxygen species, heat shock protein expression, and mucosal immunity in the sea cucumber Isostichopus badionotus’


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