Sri Lanka’s Mangroves

CNN has a story up today about the importance of, and efforts to conserve, the mangrove forests in Sri Lanka. The article features some nice photojournalism as well.

From the article:

Education is key as mangroves play a crucial role in Sri Lanka’s — and the world’s — coastal ecosystem that extends far beyond the aesthetics they bring to a boat tour. They provide critical shelter for young fish (replenishing coral reefs and fisheries, thus facilitating the livelihood of Sri Lankans who fish for a living) and sequester up to 50 times more carbon dioxide than other kinds of forests, making them indispensable in combating climate change.

They also act as a buffer against tropical storms, reducing damage to coastal communities. (Some studies have shown that areas with more substantial mangrove forests fared better during the 2004 tsunami than did communities without them.) But for all their virtues, mangroves are also at risk, having been dangerously depleted in recent decades thanks in large part to the country’s shrimp-farming industry.

Various members of my research group have been in discussions exploring the use of systems like mangrove forests as a coastal defence option for some time, both at Cambridge and in Liverpool. It’s now made it into our undergraduate curriculum/seminars as well.

Water Challenges in Jordan, Israel and Palestine

Back in September I was invited to participate in a 3-day conference/workshop titled ‘Sharing innovation to address water challenges in the Levant’ .

The conference was hosted at Wilton Park (which is, incidentally, a very unique and nice and venue) and brought together stakeholders from across the region to discuss challenges and possible solutions, in particular through research collaboration

The report is now publicly available here.

Neil DeGrasse Tyson on the merits of Audacious Endeavours

Fareed Zakaria had a segment with some predictions and thoughts for 2017 on his show GPS this week. Tyson was on the panel and started his response with a point about investment in basic science, but what I found really resonated was this response to a follow-up question from Zakaria:

[W]hat happens is — if you go big and audacious, you can attract the best people because you’re challenging them to the limits of their intellectual abilities, which people like to have happen.

So, for example, if we went to Mars and we announced that, what do you need? You need, like, the best engineers of all stripes. You need biologists, if you’re looking for life. You need chemists if you want to till the soil. And there will be patents; there will be innovations; there will be discoveries all along the way.

In Mars, you might want to extract the water from — submerged in the soil. There won’t be much, but someone who wants to do that might invent some device that you bring back to Earth and extract water from the deserts of Sahara. But if you told that person, “I need you to get the water out of Sahara,” that might not excite them as much as doing that on Mars.

So if you want to — from my experience and my read of the history of innovation, if you want to turn — if you want to transform a sleepy country into an innovation nation, the large projects tend to galvanize everybody’s energy and everybody’s capacity to think about the future.

Transcript here.

Rethinking Metabolic Assumptions and Data from High Salinity Ponds

Oren has another interesting paper out, focusing on community metabolism in hypersaline systems. The communities in the studied solar salterns consist of a primary producer, the alga Dunaliella, and halophillic prokaryotes (mostly archae, of which the majority are halobacter).

In sunny conditions the phototroph Dunaliella converts light energy to chemical forms in the system, fixing carbon and producing oxygen (oxygenic photosynthesis). The produced oxygen can be used to produce energy chemically (aerobic respiration) by Dunaliella itself (when there is insufficient light energy available) but also by halophillic prokaryotes. The halophillic prokaryotes have a way of their own to use photons, using ‘retinal’ pigments to power a proton pump and generate ATP, filling a similar role that chlorophyll does in other organisms.

The abstract reads:

We have explored the use of optical oxygen electrodes to study oxygenic photosynthesis and heterotrophic activities in crystallizer brines of the salterns in Eilat, Israel. Monitoring oxygen uptake rates in the dark enables the identification of organic substrates that are preferentially used by the community. Addition of glycerol (the osmotic solute synthesized by Dunaliella) or dihydroxyacetone (produced from glycerol by Salinibacter) enhanced respiration rates. Pyruvate, produced from glycerol or from some sugars by certain halophilic Archaea also stimulated community respiration. Fumarate had a sparing effect on respiration, possibly as many halophilic Archaea can use fumarate as a terminal electron acceptor in respiration. Calculating the photosynthetic activity of Dunaliella by monitoring oxygen concentration changes during light/dark incubations is not straightforward as light also affects respiration of some halophilic Archaea and Bacteria due to action of light-driven proton pumps. When illuminated, community respiration of brine samples in which oxygenic photosynthesis was inhibited by [the herbicide] DCMU decreased by ~40%. This effect was interpreted as the result of competition between two energy yielding systems: the bacteriorhodopsin proton pump and the respiratory chain of the prokaryotes. These findings have important implications for the interpretation of other published data on photosynthetic and respiratory activities in hypersaline environments.

So a measurement is made of the total energy needs, which can only be met using respiration when the lights are off, of a community consisting of principally Dunaliella and halophillic prokaryotes. When the lights are turned on the total respiration used to meet the same community’s energy needs, drops by about 40%. Since Dunaliella has been prevented (with DCMU) from using photosynthesis (and is thus presumably still respiring at the same rate) the drop is inferred to be coming from the prokaryotes, which seem, effectively, to opt in light to produce some portion of the energy they need from their retinal proton pumps, thereby reducing their respiration requirement.

A couple of other excerpts summarize the implications

The fact that light excitation of retinal-based proton pumps may cause a significant decrease in respiration of the (photo)heterotrophs that dominate the prokaryotic community in the system now requires a critical re-evaluation of all older data on primary productivity in salt lakes and saltern ponds […], as respiration of the prokaryotic heterotrophic component of the community may be strongly light-dependent.

There’s also an interesting side point made in the paper about the advantages of the characteristic low background oxygen level and high community densities for in situ activity studies in these sorts of systems.

Global Prevalence of Water Scarcity

Interesting new paper by Mekonnen and Hoekstra. Here’s the abstract:

Freshwater scarcity is increasingly perceived as a global systemic risk. Previous global water scarcity assessments, measuring water scarcity annually, have underestimated experienced water scarcity by failing to capture the seasonal fluctuations in water consumption and availability. We assess blue water scarcity globally at a high spatial resolution on a monthly basis. We find that two-thirds of the global population (4.0 billion people) live under conditions of severe water scarcity at least 1 month of the year. Nearly half of those people live in India and China. Half a billion people in the world face severe water scarcity all year round. Putting caps to water consumption by river basin, increasing water-use efficiencies, and better sharing of the limited freshwater resources will be key in reducing the threat posed by water scarcity on biodiversity and human welfare.

A major change from past estimates is the use of higher temporal resolution (monthly vs annual) indications of water scarcity. A couple of other issues are the spatial scale and the lack of environmental flow requirements. The presented numbers are pretty concerning — the monthly approach suggests scarcity is about 1.3-2 times more prevalent than previous estimates.

The supplementary materials are also worth reading and include an additional set of figures and a table summarizing some of the earlier estimates.