Global transcriptional responses of the toxic cyanobacterium, Microcystis aeruginosa, to nitrogen stress, phosphorus stress, and growth on organic matter

Whole transcriptome shotgun sequencing (RNA-seq) was used to assess the transcriptomic response of the toxic cyanobacterium Microcystis aeruginosa during growth with low levels of dissolved inorganic nitrogen (low N), low levels of dissolved inorganic phosphorus (low P), and in the presence of high levels of high molecular weight dissolved organic matter (HMWDOM). Under low N, one third of the genome was differentially expressed, with significant increases in transcripts observed among genes within the nir operon, urea transport genes (urtBCDE), and amino acid transporters while significant decreases in transcripts were observed in genes related to photosynthesis. There was also a significant decrease in the transcription of the microcystin synthetase gene set under low N and a significant decrease in microcystin content per Microcystis cell demonstrating that N supply influences cellular toxicity. Under low P, 27% of the genome was differentially expressed. The Pho regulon was induced leading to large increases in transcript levels of the alkaline phosphatase phoX, the Pst transport system (pstABC), and the sphX gene, and transcripts of multiple sulfate transporter were also significantly more abundant. While the transcriptional response to growth on HMWDOM was smaller (5–22% of genes differentially expressed), transcripts of multiple genes specifically associated with the transport and degradation of organic compounds were significantly more abundant within HMWDOM treatments and thus may be recruited by Microcystis to utilize these substrates. Collectively, these findings provide a comprehensive understanding of the nutritional physiology of this toxic, bloom-forming cyanobacterium and the role of N in controlling microcystin synthesis.

Land surface hydrology in a general circulation model: global and regional fields needed for validation

For the last two decades most general circulation models (GCMs) have included some kind of surface hydrology submodel. The content of these submodels is becoming increasingly complex and realistic. It is still easy to identify defects in present treatments. Yet, to improve our ability to model the contribution of land hydrology to climate and climate change, we must be concerned not with just the surface hydrology submodel per se, but also with how it works in the overall context of the GCM.

Fish for the future: Fisheries development and food security for Kiribati in an era of global climate change

The Republic of Kiribati is a vast South Pacific island group with one of the largest exclusive economic zones (EEZs) in the world. Kiribati waters support a wealth of marine fisheries activities. These activities occur in oceanic, coastal and inshore environments and range from large, foreign, industrial-scale oceanic fishing operations to small-scale, domestic, inshore subsistence fisheries, aquaculture and recreational fisheries. Kiribati has developed a framework of domestic and international governance arrangements that are designed to sustainably manage its wealth of marine resources. The report provides background information for fisheries projects in Kiribati that aim to build food security, improve artisanal livelihoods and strengthen community engagement in fisheries governance. It provides information on the current status of Kiribati fishery resources (oceanic and coastal), their current governance and future challenges. Fish and fisher alike pay little heed to maritime boundaries and bureaucratic distinctions. This report covers both sides of the oceanic/coastal boundary because of the I-Kiribati communities’ interest in oceanic fisheries such as tuna and their heavy dependence on its fisheries resources for food security and economic development. The report focuses on two potential pilot sites for community-based fisheries management projects: North Tarawa and Butaritari.

Initial global perspective of climate for the last thousand years: the ice core record

Climatic and environmental records from low, middle, and high latitude ice cores greatly increase our knowledge of the course of past events. This historical perspective is essential to predict climatic oscillations, dominated as they may be by increasing greenhouse gas concentrations. Forcing factors, internal and external, that have operated in the past will continue to influence the course of events.

Volcanic activity and global change: probable short-term and possible long-term linkages

Article reviews annual to decadal climate response to volcanism; long-term climatic response to volcanism; and recent results from ocean drilling in the North Pacific.

Simulation of recent global temperature trends [abstract]

EXTRACT (SEE PDF FOR FULL ABSTRACT): Observations show that global average tropospheric temperatures have been rising during the past century, with the most recent portion of record showing a sharp rise since the mid-1970s.

Quantifying global terrestrial carbon influx and storage as stimulated by an increase in atmospheric carbon dioxide concentration

EXTRACT (SEE PDF FOR FULL ABSTRACT): Measurements of spatial and temporal distributions of carbon dioxide concentration and carbon-13/carbon-12 ratio in the atmosphere suggest a strong biospheric carbon sink in terrestrial ecosystems. Quantifying the sink, however, has become an enormous challenge for Earth system scientists because of great uncertainties associated with biological variation and environmental heterogeneity in the ecosystems. This paper presents an approach that uses two driving parameters to bound terrestrial carbon sequestration associated with an increase in carbon dioxide concentration.