Organ damage in Atlantic herring larvae as a result of ocean acidification

The dissolution of anthropogenically emitted excess carbon dioxide lowers the pH of the world's ocean water. The larvae of mass spawning marine fishes may be particularly vulnerable to such ocean acidification (OA), yet the generality of earlier results is unclear. Here we show the detrimental effects of OA on the development of a commercially important fish species, the Atlantic herring (Clupea harengus). Larvae were reared at three levels of CO2: today (0.0385 kPa), end of next century (0.183 kPa), and a coastal upwelling scenario (0.426 kPa), under near-natural conditions in large outdoor tanks. Exposure to elevated CO2 levels resulted in stunted growth and development, decreased condition, and severe tissue damage in many organs, with the degree of damage increasing with CO2 concentration. This complements earlier studies of OA on Atlantic cod larvae that revealed similar organ damage but at increased growth rates and no effect on condition.

A puzzle with many pieces: the genetic structure and diversity of Phaeocystis antarctica Karsten (Prymnesiophyta)

Strong ocean current systems characterize the Southern Ocean. The genetic structure of marine phytoplankton species is believed to depend mainly on currents. Genetic estimates of the relatedness of populations of phytoplankton species therefore should provide a proxy showing to what extent different geographic regions are interconnected by the ocean current systems. In this study, spatial and temporal patterns of genetic diversity were studied in the circumpolar prymnesiophyte Phaeocystis antarctica Karsten using seven nuclear microsatellite loci. Analyses were conducted for 86 P. antarctica isolates sampled around the Antarctic continent between 1982 and2007. The resultsrevealed highgenetic diversity without singlegenotypes recurringeven amongisolateswithin a bloom or originating from the same bucket of water. Populations of P. antarctica were significantly differentiated among the oceanic regions. However, some geographically distant populations were more closely related to each other than they were to other geographically close populations. Temporal haplotype turnover within regions was also suggested by the multilocus fingerprints. Our data suggest that even within blooms of P. antarctica genetic diversity and population sizes are large but exchange between different regions canbe limited. Positive and significant inbreeding coefficients hint at further regional substructure of populations, suggestingthat patches, once isolated from one another, may not reconnect. These data emphasize that even for planktonic species in a marine ecosystem that is influenced by strong currents, significant breaks in geneflow may occur.