Seawater carbonate chemistry and hatching rate, malformation rate, metamorphosis rate and shell growth of the Pacific abalone in a laboratory experiment

The hatching process of the Pacific abalone Haliotis discus hannai was prolonged at a pH of 7.6 and pH 7.3, and the embryonic developmental success was reduced. The hatching rate at pH 7.3 was significantly (10.8%) lower than that of the control (pH 8.2). The malformation rates at pH 7.9 and pH 8.2 were less than 20% but were 53.8% and 77.3% at pH 7.6 and pH 7.3, respectively. When newly hatched larvae were incubated for 48 h at pH 7.3, only 2.7% of the larvae settled, while more than 70% of the larvae completed settlement in the other three pH treatments. However, most 24 h old larvae could complete metamorphosis in all four pH treatments. Overall, a 0.3-unit reduction in water pH will produce no negative effect on the early development of the Pacific abalone, but further reduction in pH to the values predicted for seawater by the end of this century will have strong detrimental effects.

Effects of ocean acidification caused by rising CO2 on the early development of three mollusks

Increasing atmospheric CO2 can decrease seawater pH and carbonate ions, which may adversely affect the larval survival of calcareous animals. In this study, we simulated future atmospheric CO2 concentrations (800, 1500, 2000 and 3000 ppm) and examined the effects of ocean acidification on the early development of 3 mollusks (the abalones Haliotis diversicolor and H. discus hannai and the oyster Crassostrea angulata). We showed that fertilization rate, hatching rate, larval shell length, trochophore development, veliger survival and metamorphosis all decreased significantly at different pCO2 levels (except oyster hatching). H. discus hannai were more tolerant of high CO2 compared to H. diversicolor. At 2000 ppm CO2, 79.2% of H. discus hannai veliger larvae developed normally, but only 13.3% of H. diversicolor veliger larvae. Tolerance of C. angulata to ocean acidification was greater than the 2 abalone species; 50.5% of its D-larvae developed normally at 3000 ppm CO2. This apparent resistance of C. angulata to ocean acidification may be attributed to their adaptability to estuarine environments. Mechanisms underlying the resistance to ocean acidification of both abalones requires further investigation. Our results suggest that ocean acidification may decrease the yield of these 3 economically important shellfish if increasing CO2 is a future trend.

Radiolarians from ODP Leg 134 sites

In the cores obtained during Leg 134 of the Ocean Drilling Program, radiolarians occur intermittently and usually in a poor state of preservation, apparently as a result of the region having been at or near the boundary between the equatorial current system and the south-central Pacific water mass during most of the Cenozoic. A few well-preserved assemblages provide a record of the Quaternary forms, and some displaced middle and lower Eocene clasts preserve a record of radiolarians near that subepochal boundary. There are less satisfactory records of middle Miocene and early Miocene to late Oligocene forms.

Seawater carbonate chemistry and shell length of northern abalone (Haliotis kamtschatkana) during experiments, 2011

Increasing levels of anthropogenic carbon dioxide in the world's oceans are resulting in a decrease in the availability of carbonate ions and a drop in seawater pH. This process, known as ocean acidification, is a potential threat to marine populations via alterations in survival and development. To date, however, little research has examined the effects of ocean acidification on rare or endangered species. To begin to assess the impacts of acidification on endangered northern abalone (Haliotis kamtschatkana) populations, we exposed H. kamtschatkana larvae to various levels of CO2 [400 ppm (ambient), 800 ppm, and 1800 ppm CO2] and measured survival, settlement, shell size, and shell development. Larval survival decreased by ca. 40% in elevated CO2 treatments relative to the 400 ppm control. However, CO2 had no effect on the proportion of surviving larvae that metamorphosed at the end of the experiment. Larval shell abnormalities became apparent in approximately 40% of larvae reared at 800 ppm CO2, and almost all larvae reared at 1800 ppm CO2 either developed an abnormal shell or lacked a shell completely. Of the larvae that did not show shell abnormalities, shell size was reduced by 5% at 800 ppm compared to the control. Overall, larval development of H. kamtschatkana was found to be sensitive to ocean acidification. Near future levels of CO2 will likely pose a significant additional threat to this species, which is already endangered with extinction due in part to limited reproductive output and larval recruitment.

(Table T1) Radiolaria abundance of ODP Hole 175-1082A

A primary objective of Leg 175 was to investigate the upwelling history of the Benguela Current. Upwelling along the coast is found over the shelf in several well-established cells, as well as along the shelf-slope break, and extends over the 1000-m isobath. Streaming filaments along the coast also carry upwelled water off shore (Shannon, 1985). The upwelled nutrient-rich waters are sourced from the South Atlantic central water mass, which is a mixture of subtropical and subantarctic water masses. Below the central water mass lies Antarctic intermediate water (Shannon and Hunter, 1988, doi:10.2989/025776188784480735; Stramma and Peterson, 1989, doi:10.1175/1520-0485(1989)019<1440:GTITBC>2.0.CO;2). The upwelling system supports a robust marine community (Shannon and Pillar, 1986) where radiolarians are abundant (Bishop et al., 1978, doi:10.1016/0146-6291(78)90010-3). The endemic nature of radiolarians makes them useful in reconstructing the paleocirculation patterns. The biogeographic distribution of many species is limited by water-mass distribution. In a given geographic region, species may also have discrete depth habitats. However, their depth of occurrence can change worldwide because the depths of water masses vary with latitude (Boltovskoy, 1999). Consequently, species found at shallow depths at high latitudes (cold-water fauna) are observed deeper in the water column at lower latitudes. The low-latitude submergence of cold-water species broadens their distribution, resulting in species distributions that can cover multiple geographic regions (Kling, 1976, doi:10.1016/0011-7471(76)90880-9; Casey, doi:10.1016/0031-0182(89)90017-5; 1971; Boltovskoy, 1987, doi:10.1016/0377-8398(87)90014-4). Since radiolarian distribution is closely related to water-mass distribution and controlled by climatic conditions rather than geographic regions, similar assemblages characterize the equatorial, subtropical, transition, subpolar, and polar regions of ocean basins (Petrushevskaya, 1971a; Casey, 1989, doi:10.1016/0031-0182(89)90017-5; Boltovskoy, 1999). Numerous radiolarian species found in water masses in the Angola and Benguela Current systems have also been observed in plankton net samples, sediment traps, and surface-sediment studies in the Atlantic sector of the Southern Ocean, where they exhibited particular water-mass affinities (Abelmann, 1992a, doi:10.1007/BF00243107; Abelmann 1992b, doi:10.1007/BF00243108; Abelmann and Gowing, 1997, doi:10.1016/S0377-8398(96)00021-7). This report presents data on the radiolarian fauna recovered from Site 1082 sediments in the form of a survey of species reflecting the latitudinal migration of the Angola-Benguela Front and upwelling. The data constitute a time series of relative radiolarian abundances at very high resolution (every 20 cm) of the upper 12 m of Hole 1082A.