Effects of elevated CO2 on early life history development of the yellowtail kingfish, Seriola lalandi, a large pelagic fish

An increasing number of studies have examined the effects of elevated carbon dioxide (CO2) and ocean acidification on marine fish, yet little is known about the effects on large pelagic fish. We tested the effects of elevated CO2 on the early life history development and behaviour of yellowtail kingfish, Seriola lalandi. Eggs and larvae were reared in current day control (450 µatm) and two elevated CO2 treatments for a total of 6 d, from 12 h post-fertilization until 3 d post-hatching (dph). Elevated CO2 treatments matched projections for the open ocean by the year 2100 under RCP 8.5 (880 µatm CO2) and a higher level (1700 µatm CO2) relevant to upwelling zones where pelagic fish often spawn. There was no effect of elevated CO2 on survival to hatching or 3 dph. Oil globule diameter decreased with an increasing CO2 level, indicating potential effects of elevated CO2 on energy utilization of newly hatched larvae, but other morphometric traits did not differ among treatments. Contrary to expectations, there were no effects of elevated CO2 on larval behaviour. Activity level, startle response, and phototaxis did not differ among treatments. Our results contrast with findings for reef fish, where a wide range of sensory and behavioural effects have been reported. We hypothesize that the absence of behavioural effects in 3 dph yellowtail kingfish is due to the early developmental state of newly hatched pelagic fish. Behavioural effects of high CO2 may not occur until larvae commence branchial acid-base regulation when the gills develop; however, further studies are required to test this hypothesis. Our results suggest that the early stages of kingfish development are tolerant to rising CO2 levels in the ocean.

Geochemistry and age model of sediment core BDP96-1

Within the framework of the Baikal Drilling Project (BDP), a 192 m long sediment core (BDP-96-1) was recovered from the Academician Ridge, a submerged topographic high between the North and Central Basins of Lake Baikal. Sedimentological, clay mineralogical and geochemical investigations were carried out on the core interval between 90 and 124 m depth, corresponding to ca. 2.4-3.4 Ma. The aim was to reconstruct the climatic and tectonic history of the continental region during the intensification of Northern Hemisphere glaciation in Late Pliocene time. A major climate change occurred in the Lake Baikal area at about 2.65 Ma. Enhanced physical weathering in the catchment, mirrored in the illite to smectite ratio, and temporarily reduced bioproduction in the lake, reflected by the diatom abundance, evidence a change towards a colder and more arid climate, probably associated with an intensification of the Siberian High. In addition, the coincident onset of distinct fluctuations in these parameters and in the Zr/Al ratio suggests the beginning of the Late Cenozoic high amplitude climate cycles at about 2.65 Ma. Fluctuations in the Zr/Al ratio are traced back to changes in the aeolian input, with high values in warmer, more humid phases due to a weaker Siberian High. Assuming that the sand content in the sediment reflects tectonic pulses, the Lake Baikal area was tectonically active during the entire investigated period, but in particular around 2.65 Ma. Tectonic movements have likely led to a gradual catchment change since about 3.15 Ma from the western towards the eastern lake surroundings, as indicated in the geochemistry and clay mineralogy of the sediments. The strong coincidence between tectonic and climatic changes in the Baikal area hints at the Himalayan uplift being one of the triggers for the Northern Hemisphere Glaciation.