Characteristics of digestive enzymes of calanoid copepod species from different latitudes in relation to temperature, pH and food

In calanoid copepods it is poorly understood how enzymatic activities and patterns are affected by abiotic and biotic factors. Such knowledge, however, is crucial to assess metabolic functioning and performance of organisms in different habitats. Therefore, our study focuses on digestive enzyme activities in relation to temperature, pH and food in the Arctic species Calanus glacialis and in Centropages hamatus and Temora longicornis from the North Sea. Enzyme activities were measured over a range from 0 to 70 °C (lipases/esterases, proteinases) and pH 5 to 9 (proteinases). In all species, relative proteinases activity peaked at 40/50 °C and pH 6; relative lipases/esterases activity peaked at 30 °C. Between 0 and 20 °C, lipase activity of C. glacialis was higher (40-70% of maximum) than that of the boreal copepods (25-64%), which suggests thermal adaptation of the lipid metabolism in the polar species. Incubating C. glacialis with the diatom Thalassiosira weissflogii showed (i) that enzyme activities increased especially in the alkaline range and (ii) that enzyme patterns, revealed by gel electrophoresis, differed from that of starving individuals, indicating that feeding induced enzyme expression. Such studies, linking abiotic and biotic conditions to enzyme functioning, can help elucidating the capacity of copepods to respond to environmental changes.

Ocean acidification and the loss of phenolic substances in marine plants

Rising atmospheric CO₂ often triggers the production of plant phenolics, including many that serve as herbivore deterrents, digestion reducers, antimicrobials, or ultraviolet sunscreens. Such responses are predicted by popular models of plant defense, especially resource availability models which link carbon availability to phenolic biosynthesis. CO₂ availability is also increasing in the oceans, where anthropogenic emissions cause ocean acidification, decreasing seawater pH and shifting the carbonate system towards further CO₂ enrichment. Such conditions tend to increase seagrass productivity but may also increase rates of grazing on these marine plants. Here we show that high CO₂ / low pH conditions of OA decrease, rather than increase, concentrations of phenolic protective substances in seagrasses and eurysaline marine plants. We observed a loss of simple and polymeric phenolics in the seagrass Cymodocea nodosa near a volcanic CO₂ vent on the Island of Vulcano, Italy, where pH values decreased from 8.1 to 7.3 and pCO₂ concentrations increased ten-fold. We observed similar responses in two estuarine species, Ruppia maritima and Potamogeton perfoliatus, in in situ Free-Ocean-Carbon-Enrichment experiments conducted in tributaries of the Chesapeake Bay, USA. These responses are strikingly different than those exhibited by terrestrial plants. The loss of phenolic substances may explain the higher-than-usual rates of grazing observed near undersea CO₂ vents and suggests that ocean acidification may alter coastal carbon fluxes by affecting rates of decomposition, grazing, and disease. Our observations temper recent predictions that seagrasses would necessarily be “winners” in a high CO₂ world.

Pre-dinosaur extinction killed 95% of sea species

It may never be as well known as the Cretaceous extinction, the one that killed off the dinosaurs. Yet the much earlier Permian extinction – 252 million years ago – was by far the most catastrophic of the planet’s five known paroxysms of species loss.

No wonder it is called the Great Dying: Scientists calculate that about 95 percent of marine species, and an uncountable but probably comparable percentage of land species, went extinct in a geological heartbeat.

The cause or causes of the Permian extinction remain a mystery. Among the hypotheses are a devastating asteroid strike, as in the Cretaceous extinction; a catastrophic volcanic eruption; and a welling-up of oxygen-depleted water from the depths of the oceans.

Now, painstaking analyses of fossils from the period point to a different way to think about the problem. And at the same time, they are providing startling new clues to the behavior of modern marine life and its future.

In two recent papers, scientists from Stanford and the University of California, Santa Cruz, adopted a cellular approach to what they called the “killing mechanism”: not what might have happened to the entire planet, but what happened within the cells of the animals to finish them off.

Attention heroes: who will save the world’s oceans?

The planet has five major oceans. A lesser known fact is that the acidity in the ocean is contributing to the die-off of shellfish populations and the bleaching of coral reefs. Imagine no shells at the beach. Or no oysters and salmon — other species currently at risk.

The cause? Excess emissions of carbon dioxide in the atmosphere are causing changes in the chemistry of the world’s oceans.

This weekend, at the X Prize Foundation’s Visioneering Conference, Wendy Schmidt, President of the Schmidt Family Foundation and spouse of Google Executive Chairman Eric Schmidt, announced her intent to sponsor a prize to address the issue.

The X Prize Foundation creates competitions for big ideas, focused on solving the world’s grand challenges.

To compete in the Ocean Health X Prize, winners must: Build and demonstrate the most accurate and reliable deep ocean pH sensors to help measure the global effects of climate change on the world’s oceans.

Current pH sensor technology can only make accurate measurements in shallow waters or in isolated samples of the deeper seas. The prize is seeking improvements in the speed, depth tolerance, and lifetime of autonomous pH sensors.

Integrated management of nutrients from the watershed to coast in the subtropical region

This paper is a brief review on nutrient variation (changes in element concentrations and ratios) and the associated aquatic ecosystem responses in the subtropical region. Human activities have significantly modified both the flux and the ratio of nutrients delivered to aquatic ecosystems. Climate perturbations influence the hydrological regime and enhance nutrient mineralization and transport from land to receiving waters. Changes in land use and damming have resulted in changes in the balance among nitrogen, phosphorus and silicon elements, thus increasing the risk of algal bloom. Nutrient variation and its ecological effects in the subtropical region could be more significant than in other areas because of rapid development and high population. Aquatic ecosystems respond to nutrient variation in complex and dynamic ways resulting in eutrophication, hypoxia/anoxia, acidification, and changes in phytoplankton and microbial communities. This review suggests that harmful algal bloom, jellyfish bloom, and serious pathogens are often associated with nutrient variations. The current challenges to scientific research and management include the facts that (1) the link between nutrient dynamics and ecosystem responses is poorly understood; (2) monitoring data to support modeling and management are scarce; (3) aquatic ecosystems are site-specific and/or situation-specific and are highly dynamic, giving greater complexity in research and management; and (4) the lack of regional coordination in traditional management causes transboundary gaps. To address these current challenges, an integrated management framework was proposed for effective nutrient management. Institutional arrangements should be developed to coordinate across multiple government agencies and other stakeholders from watershed to coast. The framework should integrate an interdisciplinary scientific approach and adaptive principles regarding nutrient management.

Marine microbiology: evolution on acid

The prediction of marine microbial responses to ocean acidification is a key challenge for marine biologists. Experimental evolution offers a powerful tool for understanding the forces that will shape tomorrow’s microbial communities under global change.

Temperate and tropical brown macroalgae thrive, despite decalcification, along natural CO2 gradients

Predicting the impacts of ocean acidification on coastal ecosystems requires an understanding of the effects on macroalgae and their grazers, as these underpin the ecology of rocky shores. Whilst calcified coralline algae (Rhodophyta) appear to be especially vulnerable to ocean acidification, there is a lack of information concerning calcified brown algae (Phaeophyta), which are not obligate calcifiers but are still important producers of calcium carbonate and organic matter in shallow coastal waters. Here we compare ecological shifts in sub-tidal rocky shore systems along CO₂ gradients created by volcanic seeps in the Mediterranean and Papua New Guinea, focussing on abundant macroalgae and grazing sea urchins. In both the temperate and tropical systems the abundances of grazing sea urchins declined dramatically along CO₂ gradients. Temperate and tropical species of the calcifying macroalgal genus Padina (Dictyoaceae, Phaeophyta) showed reductions in CaCO₃ content with CO₂ enrichment. In contrast to other studies of calcified macroalgae, however, we observed an increase in the abundance of Padina spp. in acidified conditions. Reduced sea urchin grazing pressure and significant increases in photosynthetic rates may explain the unexpected success of decalcified Padina spp. at elevated levels of CO₂. This is the first study to provide a comparison of ecological changes along CO₂ gradients between temperate and tropical rocky shores. The similarities we found in the responses of Padina spp. and sea urchin abundance at several vent systems increases confidence in predictions of the ecological impacts of ocean acidification over a large geographical range.

Productivity gains do not compensate for reduced calcification under near-future ocean acidification in the photosynthetic benthic foraminifera Marginopora vertebralis

Changes in the seawater carbonate chemistry (ocean acidification) from increasing atmospheric carbon dioxide (CO₂) concentrations negatively affect many marine calcifying organisms, but may benefit primary producers under dissolved inorganic carbon (DIC) limitation. To improve predictions of the ecological effects of ocean acidification, the net gains and losses between the processes of photosynthesis and calcification need to be studied jointly on physiological and population levels. We studied productivity, respiration, and abundances of the symbiont-bearing foraminifera Marginopora vertebralis on natural CO₂ seeps in Papua New Guinea and conducted additional studies on production and calcification on the Great Barrier Reef (GBR) using artificially enhanced pCO₂. Net oxygen production increased up to 90% with increasing pCO₂, with temperature, light and pH together explaining 61% of the variance in production. Production increased with increasing light and increasing pCO₂, and declined at higher temperatures. Respiration was also significantly elevated (~25%), while calcification was reduced (16-39%) at low pH/high pCO₂ compared to present day conditions. In the field, M. vertebralis was absent at three CO₂ seep sites at pH_Total levels below ~7.9 (pCO₂ ~700 μatm), but it was found in densities of over 1000 m⁻² at all three control sites. The study showed that endosymbiotic algae in foraminifera benefit from increased DIC availability, and may be naturally carbon limited. The observed reduction in calcification may have been caused either by increased energy demands for proton pumping (measured as elevated rates of respiration), or by stronger competition for DIC from the more productive symbionts. The net outcome of these two competing processes is that M. vertebralis cannot maintain populations under pCO₂ exceeding 700 μatm, thus are likely to be extinct in the next century.